CN1088843C - Electronic metering device with automatic service sensor - Google Patents

Abstract

The present invention relates to a system diagnosis device and a display device thereof. The system diagnosis device used for integrative electrical measuring instruments comprises a microprocessor, a memorizer and a preselection sequential system and can diagnose, detect and record any result which exceeds a predetermined programmable control threshold value; the display device is used for displaying faults and/or identifying the diagnostic information of the selected diagnostic data and/or faults discovered in detecting electricity meters in a predetermined cycle. The system automatically inducts the type of electricity maintenance with electricity meters.

Description

Electrical Meter with Automatic Maintenance Sensing Device

This application is a partial continuation of the "system detection and fault analysis device for electrical measuring instruments" filed on March 26, 1993 with serial number 08/037,938.

The invention relates to a whole set of method and device for system installation and diagnosis of solid-state electrical measuring instruments.

Inductive watt-hour meters typically use a pulse generator to generate pulses proportional to the dial's rotational speed. These generated pulses are sent to an electronic recorder to obtain current, voltage, power and/or time spent using energy.

Various types of solid state polyphase electrical meters are also widely used today. This meter monitors electrical energy consumption and records or reports this power consumption in kilowatt-hours, power factor (KVA), and/or volt-amperes, typically using solid-state components and may utilize an analog-to-digital converter to provide digital data , rather than pulse data from which the indicator extracts various demand/consumption.

It is also known to install reconfigurable solid-state electrical meters in various single-phase or multi-phase electrical distribution systems. An example of a solid state electronic watt-hour meter is disclosed in US Patent No. 5,059,896 to Germer et al.

An example of a solid-state electricity demand recorder that can be used with a conventional watt-hour meter is disclosed in US Patent No. 4,697,182 to Swanson.

During the installation of these meters, maintenance personnel use various auxiliary equipment and diagnostic techniques to try to verify that the installation has been wired correctly. However, many installation tests, such as polarity and cross-phase checks, are performed on site by field personnel and thus rely on the knowledge and ability of these personnel.

With various diagnostic equipment available for field personnel to use during installation or periodic maintenance, there is a need for a standard series of system and installation diagnostics kits that can automatically and periodically perform a series of system and installation diagnostics without interrupting the operation of the meter. In addition, it is also necessary for the meter to perform periodic self-checks during operation to detect and record the occurrence of predefined fatal or non-fatal faults.

Furthermore, while there are some meters that are suitable for use in more than one type of electrical maintenance, such meters have the disadvantage that the user often must program the type of maintenance prior to installation. Such pre-installed programming of multi-type maintenance meters necessarily limits their multi-type maintenance capabilities.

In view of this, the purpose of the present invention is to provide a complete system detection and failure analysis device for the solid-state electrical measuring instrument.

Another object of the present invention is to provide a method and apparatus for integrating with a solid state electric meter and automatically performing a series of predetermined system installation and diagnostic tests thereon.

Yet another object of the present invention is to provide a system inspection and fault analysis device supported and integrated into an electrical meter, and also includes means for displaying selected inspection and system diagnostic test results when inquired by maintenance personnel.

It is yet another object of the present invention to provide an automatic system detection arrangement which periodically detects the existence of certain predetermined conditions and which, depending on the nature of the fault, takes predetermined action in response to the detection of any such fault.

Another object of the present invention is to provide a method and apparatus for determining the phase angle of each voltage and current phasor with respect to a predetermined reference phasor, the purpose of which is to verify that all meter components are sensing and receiving polyphase Correct voltage and current for each phase of electrical maintenance.

Yet another object of the present invention is to provide a method and apparatus for automatic detection of specific types of electrical maintenance in conjunction with a solid state multi-type maintenance meter, after the meter is installed, and periodically during its operation.

According to the present invention, a complete electric meter self-check and system diagnostic device is provided, including a microprocessor, memory, used to automatically and periodically perform a pre-selected set of meter self-checks and record any faults that occur Logic circuits for automatically and periodically performing a series of preselected system diagnostic tests and recording any results exceeding predetermined programmable thresholds, and display devices for displaying fault and/or diagnostic information, respectively Indicates one or more self-test faults, or selected diagnostic data and/or faults found during a meter self-check within a predetermined period.

The apparatus of the present invention is preferably combined with a solid-state electricity meter employing a digital-to-analog converter and associated digital sampling techniques to obtain digital data corresponding to one or more phases of current and voltage of a single-phase or multi-phase system to which the meter is connected .

The present invention automatically performs pre-selected meter self-checks, preferably daily, and/or when restarting after a power outage and/or reconfiguring the entire meter structure, to verify the operational capabilities of selected meter components. For example, in a preferred embodiment, the inventive device tests its own memory, microprocessor and selected registers in the meter to determine if billing data has deteriorated since the last check. Since the data corruption of billing is considered to be a fatal error of the meter, the device of the present invention will generate and display a fault code indicating the type of fault, lock the display on the fault code, and suspend all meter functions (except communication functions) until Reconfigure the table.

In addition, the device periodically checks for other non-fatal faults such as register overflow, clock, usage time, reverse power flow, and low battery. The frequency of fault inspections may vary, depending on the components and conditions being inspected, and the potential impact of such faults on the continued operation of the meter. Whether a non-fatal fault can lock out the display once discovered depends on the nature of the fault and how that particular meter is configured.

The present invention also periodically performs a series of preselected system diagnostic tests. These tests are performed while the meter is installed, and ideally every five seconds or so during normal meter operation. In the preferred embodiment, the device performs polarity, cross-phase and energy flow diagnostics, phase voltage deviation diagnostics, reactive phase current diagnostics, per-phase power factor diagnostics, and current waveform distortion detection diagnostics, such diagnostics are determined using the manufacturer's parameters as well as user-defined parameters that can be set by field personnel during installation.

In performing polarity, cross-phase, and energy flow diagnostics, the apparatus of the present invention uses accumulated current and voltage information to determine each voltage and current phasor (e.g., V _B , V _C , I _A , I _{B )} in a polyphase system. and _IC ) relative to the phase angle of a reference phasor (eg, V _A ). Each phase vector is predetermined for the normal position of this installation, and is used as a standard value for comparison with the calculated phase angles to determine whether each phase angle falls within a predetermined range. If any of the calculated phase angles is outside its corresponding predetermined range, a diagnostic fault message will be displayed. This diagnostic is particularly useful in installations, as such faults can point to cross-phase relationships in voltage or current loops, incorrect polarity in voltage or current loops, reversed phase energy flow in single or multiple phases (co-generated), or Internal meter measurement is not working properly.

The device of the present invention also specifically includes a "Toolbox" display which, when manually activated by field personnel, will scroll through the entire list of preselected values for field personnel to review, such as voltage and current for each phase, and The phase angles associated with the current phasors, and the number of diagnostic failures for each.

In one embodiment of the present invention, the device of the present invention automatically senses the type of electrical maintenance (i.e. single-phase, three-wire delta, four-wire Y) after the meter is installed and powered on, especially periodically during normal operation of the meter. shape or four-line triangle).

These system diagnostics, toolbox display and automatic maintenance sensing functions are performed by the device of the present invention without interrupting the operation of the meter unless the meter operation is intentionally discontinued due to a fatal fault.

The above and other objects, features and advantages of the present invention will be readily apparent from the following detailed discussion of the best modes for carrying out the invention with reference to the accompanying drawings.

Fig. 1 is a system block diagram;

Fig. 2 is a perspective view of an electric meter with which the system of the present invention can be combined;

Fig. 3 is the block diagram of Fig. 2 ammeter;

Fig. 4 is a flow chart of the diagnostic detection of the power system of the present invention;

Figure 5 is a flowchart of the first part of polarity, cross-phase and power flow diagnostics implemented by the present invention;

Figure 6 is a flowchart of the second part of the polarity, cross-phase and power flow diagnostics implemented by the present invention;

Figure 7 is a flowchart of the first part of the phase voltage deviation diagnostic routine implemented by the present invention;

Fig. 8 is the flowchart of the second part of phase voltage deviation diagnosis realized by the present invention;

Fig. 9 is the flow chart of the first part of reactive phase current diagnosis realized by the present invention;

Fig. 10 is the flowchart of the second part of reactive phase current diagnosis realized by the present invention;

Fig. 11 is the flowchart of the first part of the diagnosis of each phase power factor realized by the present invention;

Fig. 12 is the flowchart of the second part of the diagnosis of each phase power factor realized by the present invention;

Fig. 13 is the flowchart of the third part of the diagnosis of each phase power factor realized by the present invention;

Figure 14 is a list of items displayed in the Toolbox display;

Figure 15 is a phase vector diagram for a typical three-phase meter installation;

Figure 16 is a waveform diagram illustrating two phasors representing system tracking:

FIG. 17A is the first part of the block diagram of the front-end module 42 in FIG. 3;

FIG. 17B is the second part of the block diagram of the front-end module 42 in FIG. 3;

Figure 18A is the first part of the block diagram of the register module 48 in Figure 3;

Figure 17B is the second part of the block diagram of the register module 48 in Figure 3;

Fig. 19 is the first flowchart of detection and diagnosis of current waveform distortion realized by the present invention;

Fig. 20 is the second flowchart of detection and diagnosis of current waveform distortion realized by the present invention;

Figure 21 illustrates a table representing the types of meter form vectors and associated electrical maintenance they can support;

Figure 22 is a flow chart of the first part of the automatic maintenance sensing function realized by the present invention;

Figure 23 is a flowchart of the second part of the automatic maintenance sensing function implemented by the present invention.

1, the system of the present invention, generally designated 20, includes a central processing unit 22 sufficient to store digital data corresponding to periodic sampling of voltage and current data from a voltage A/D converter 26 and a current A/D converter 28, respectively. Storage 24 for data, logic 30 for system-supported meter self-checks and system and installation diagnostics, and display means for displaying fault and diagnostic information.

Referring to Figure 2, the system 20 preferably incorporates a solid state polyphase kilowatt/kilowatt hour ("Kw/Kwh") single-function electricity meter 34 (as illustrated in Figures 3, 17A-B and 18A-B and described in detail below) , the meter includes a generally circular base 36, a conventional molded plastic case (not shown) with a fixed face plate and a cover 40. The electricity meter 34 meter also contains conventional current sensing components suitable for connection to the live power system.

Referring now to FIG. 3 in the preferred embodiment, the diagnostic logic circuit 30 of the system 20 of the present invention is incorporated into the front-end module 42 of the electric meter, which includes a microprocessor 44, an 8-bit circuit used as a voltage A/D converter 26. bit A/D converter, a random access memory 45 used as part of the system memory 24, and read only memory and EEPROM, where the system diagnostic logic resides (46). The front end modules are in addition to the system and installation diagnostics and toolbox displays performed by the system 20 of the present invention. It is also preferable to provide other meter functions including meter component self-check, A/D sampling, energy calculation, current demand, instantaneous value, any optional output, and meter communication. The display in this embodiment is a liquid crystal display 33 which preferably contains 9 seven-segment digits, 3 decimal points and is used to display power system information normally displayed by a conventional meter and diagnostic data generated by the system of the present invention The multiple icons of , generally as shown in Figure 3.

The meter 34 also includes a register module 48 with a microprocessor 50 including: read only memory; random access memory 51, which also serves in part as system memory; a 96-segment LCD display driver; and 24 I/O lines. In this embodiment, the read only memory and registers CPU 50 includes the display logic used to generate the toolbox display and the diagnostic trouble codes generated by the system 20 of the present invention. Register module 48 provides other meter functions such as maintaining billing values and billing register related functions, in addition to time related functions such as self read, time of use, run time and mass storage.

It should be noted that in the embodiment of the meter 34 shown in FIG. 3, the system 20 of the present invention uses an 8-byte A/D converter 26 for sensing the voltage signal and an external 12-byte A/D converter 26 for sensing the current sample. A/D converter 28 . As known to those skilled in the art, current transformer 28 requires higher resolution because current varies over a wider range than voltage. Those skilled in the art will also understand that current and voltage are preferably sensed simultaneously by separate transformers so that phase errors produced by the current transformers can be compensated directly by adjusting the delay between current sampling and voltage sampling. Thus, with an ideal current transformer and no transfer phase delay, separate transformers 26 and 28 can be used to simultaneously sample voltage and current.

The display logic used to generate the toolbox display and diagnostic fault information for system 20 is part of display logic 52 implemented by register CPU 50 in the particular embodiment of FIG. However, those skilled in the art will appreciate that the logic circuit and CPU capability of the system of the present invention can be implemented with a simpler signal processor structure (as shown in Figure 1), and the structure shown in Figure 3 or other hardware facilities. without departing from the essence of the present invention.

The system 20 of the present invention provides a full range of system diagnostic capabilities and diagnostic display functions through a "toolbox" display. The system and installation diagnostics are determined in part by the user through programming software. The toolbox is a display of diagnostic information that contains fixed settings in a specific operating mode, and it can be accessed by the user (usually field personnel) by actuating a magnetic switch on the meter. Each diagnostic capability is discussed in further detail below.

In one embodiment, system 20 also provides an automated maintenance sensing capability. As will be described in further detail below, this capability includes logic to automatically and periodically determine the maintenance of electricity provided by the meter based on The meter is pre-programmed with the form number and angular displacement of the voltage phasors Va and Vc. as described below. System and Installation Diagnostics

The system 20 of the present invention performs various system and installation diagnostics that can indicate potential problems related to electrical maintenance, incorrect installation of the meter, or malfunctioning within the meter. While such diagnostics may vary depending on the type of electrical maintenance provided by the meter, the diagnostics described below are generally performed by the system.

Referring to Figure 4, such system and installation diagnostics are also preferably implemented as a status mechanism. In the preferred embodiment, the diagnostics consist of four user-selectable diagnostics for the meter: (1) polarity, cross-phase, and energy flow checks; (2) phase voltage deviation checks; (3) current transformer checks; (4) Each phase power factor check; and (5) Current waveform distortion check. All selected diagnostics are performed by the meter at least every 5 sampling intervals.

When any fault condition occurs according to the parameters determined by the user corresponding to the diagnostic failure, the meter displays information to indicate its fault condition and optionally triggers the closure of an output contact, such as a mercury wetted relay or a programmed "fault condition alarm" solid state contacts. When a selected output is programmed as a fault condition alarm, the output contact will close whenever any diagnostic fault selected by the user is activated.

Referring again to FIG. 4, the system 20 of the present invention is best illustrated by a series of calculations and diagnostic checks shown at 54-62. In this preferred embodiment, the processing time is divided into sampling intervals equal to 60 power line clock cycles. For example, in a 50Hz device, this is 1.2 seconds. In a 60Hz device, the sampling interval will be 1 second.

Using a simple counter, system 20 performs the necessary sampling and calculations to determine the phase angle of I _A (preferably with respect to phasor V _A ) and performs diagnostic check #1 during the first sampling interval, shown at 54 .

During the second interval (56), the system 20 accumulates the necessary samples to calculate the phase angle of I _B and performs diagnostic check #2.

In the third interval (58), the system accumulates the necessary samples to calculate the phase angle of _IC and perform diagnostic check #3.

In the fourth interval (60), the system accumulates the necessary samples to calculate the phase angle of V _B and perform diagnostic check #4.

In the fifth interval (62), the system accumulates the necessary samples to calculate the phase angle of _VC , performs diagnostic check #5 and resets the counter.

The counter is incremented by 1 at the end of each interval (64 steps), and the sequence is repeated continuously. Thus, in a 60 Hz system, the phase angle is calculated for each current and voltage phasor and each of the four diagnostic checks is performed every 5 seconds. Different time intervals may be performed and/or subroutines 54-62 may be changed to accommodate more or less frequent examinations of one or more of the desired selected diagnostics, as known to those skilled in the art. Diagnostic #1 - Polarity, Cross Phase and Power Flow Checks

According to Figures 5 and 6, the polarity, cross-phase and energy flow checks are designed to check for any reversal of phase voltage and current polarity, and to check for miswiring of a phase voltage and a different phase current. This situation can also arise due to the presence of resonance. This check is done by periodically measuring the phase angle of each voltage and current phasor with respect to a reference vector (preferably _VA ). Each phase angle is compared to its ideal phase angle, which is defined as the possible phase angle from a balanced purely resistive load. If any voltage phase angle lags or leads its ideal phase angle by more than a predetermined value (preferably 10°), or any current phase angle lags or leads its ideal phase angle by more than a second predetermined value (preferably 90°), the meter indicates A diagnostic #1 failure.

As shown in FIG. 5, the polarity, cross phase and power flow check diagnostic routine 66 of the system 20 first checks each phase angle of each current and voltage phasor (at 68-76) power system) to determine whether each phase angle falls within tolerance to a predetermined ideal value for ABC rotation. If any of these phase angles do not fall within the allowable range of ideal values, the system sets the abc flag to false (at 78), then proceeds (as shown in Figure 6) to check each phase assuming a CBA rotation horn.

If all of the phase angles determined via 68-76 fall within the allowable range of their predetermined ideal values, then the system 20 sets the abc flag to correct at 80 (at 80) and proceeds to check the phase angles assumed to be cba rotations.

Referring now to FIG. 6, once the ABC rotation check is performed, the system checks the phase angles of each current and voltage phasor via 82-90 to determine if the phase angles for CBA rotation fall within the allowable range of their predetermined ideal values. If any phase angle is outside the allowable range of the predetermined ideal value for that phasor, the system sets the cba flag to false at 92 . If all phase angles measured fall within the allowable range of their predetermined ideal values, the system sets the cba flag to correct at 94 . The system 20 then determines whether the abc or cba designation is correct. If both are correct, the diagnostic check passes. If both the abc designation and the cba designation are incorrect, both the ABC and CBA rotation diagnostic checks are out of specification, indicating a diagnostic fault.

When a diagnostic fault is detected, the system records the occurrence of the fault and displays the fault, as described further below. However, in the present preferred example, no initial indication of such a diagnostic fault occurs until such a fault condition exists until three consecutive inspections.

As known to the skilled artisan, this diagnosis can point to one of certain problems, including cross-phase relationships of potential or current loops, wrong polarity of potential or current loops, reverse energy flow in one or more phases, or internal meter measurements Not working properly. Diagnostic #2 - Phase Voltage Deviation Check

Referring now to Figures 7 and 8, this phase voltage deviation check is designed to check (at 98) any phase voltage that is outside a user-determined range. This is actually a distribution transformer voltage gap check. This is done by periodically measuring the voltage of each phase and checking it against a predetermined voltage range calibrated by the program software.

The formula used for this check is: $V_{\mathrm{upper}}=(1+\frac{\mathrm{XX}}{100})V_A,$ as well as $V_{\mathrm{lower}}=(1-\frac{\mathrm{XX}}{100})V_A$

If any phase voltage is above V _upper or below V _lower , the meter will indicate a phase voltage range diagnostic fault.

It should be noted that in the preferred example, the system 20 checks (at 100) to determine whether the electrical maintenance supported by the meter on which the system 20 is installed is a three-phase, four-wire delta connection maintenance. If so, the system calculates the upper and lower limits for the particular case of the phase C voltage, as shown at 102 .

In addition, if the phase C or B voltage exceeds the predetermined range, the system indicates that the diagnostic check has failed (at 104 or 106), indicates a diagnostic fault, records the fault and displays the corresponding fault message, as described below. Otherwise, the diagnostic check is passed (at 108) and the test is complete.

It should be noted, however, that in the preferred example, the initial indication of such a diagnostic fault does not occur until the fault condition is present for three consecutive checks.

This diagnostic can point to loss of phase potential, wrong transformation ratio, shorted transformer windings, incorrect phase voltages, incorrect internal meter measurements, and other potential problems. Diagnostic #3 - Reactive Phase Current Check

Referring now to Figures 9 and 10, in performing reactive phase current diagnostics, the system 20 will periodically compare the instantaneous RMS current of each phase to a predetermined minimum current level, preferably in the range of 5mA to 200A in 1mA increments optional. If all three-phase currents are above the allowable level, or all three-phase currents are below the allowable level, the diagnosis is passed. Any other combination will cause Diagnostic #3 to be out of specification and will indicate a Diagnostic #3 failure.

Preferably, however, the recording and display of such a diagnostic fault does not occur until the fault condition is present on three consecutive inspections.

The presence of a diagnostic #3 fault means that one or more phases of the meter phase current magnitudes are out of specification. To solve this specific problem, the user must obtain phase current information from the Toolbox mode. As described later.

As known to those skilled in the art, this diagnostic check can be used to point out any of some potential problems, such as an open or shorted current transformer circuit. Diagnostic #4 - Per Phase Power Factor Check

Referring to Figures 11-13, the per-phase power factor diagnostic check is designed to verify that the phase angle between the current phasor and the ideal voltage phasor of each phase of the meter is within the user-specified range (+/-1-90°). Since this tolerance is more restrictive than for Diagnosis #1, system 20 does not perform this diagnostic check until Diagnosis #1 has passed. This diagnosis may point to any of a number of potential problems, including poor load power factor conditions, poor system conditions, or malfunctioning system equipment.

The system 20 first checks the abc and cba rotation flags at 114 and 116, and if both flags are wrong, it means that diagnosis #1 has failed. Since the tolerance of this diagnosis is larger than the limit for diagnosis #1, the diagnosis check is aborted.

If both the abc and cba flags are true (indicating that diagnostic #1 has passed), the system 20 performs the corresponding ABC and CBA rotation checks at 114 and 116, respectively. For ABC rotation, the system checks the phase angle (118-122) between the corresponding current phasor and the ideal voltage phasor to determine if the phase angle is within a user-defined range. If the phase angle is within the predetermined range, the diagnostic is passed (at 124). If not, the diagnostic fails (126), indicating a diagnostic #4 failure. In the case of CBA rotation, system 20 performs a similar range of checks (128-132) on the applicable current phasors. Diagnostic #5 - Current Waveform Distortion Check

Referring to Figure 19, the current waveform distortion check is designed to detect the presence of DC current in any one phase. This diagnostic is especially useful for meters designed to carry AC current only, where the performance of the current transformer is degraded by excessive DC currents that bias the transformer so that it operates in a non-linear region.

The basic method of generating DC current in an electric meter is to place a half-wave rectified load in parallel with the normal load. The presence of the half-wave rectified current signal has the effect of increasing the amplitude of the positive or negative half-cycle of the waveform while leaving the other half-cycle unaffected. For those meters that are not designed to pass DC current, when this signal appears at the input terminal of the current transformer, its level floats so that the output average value is zero. However, the peak magnitudes of the positive and negative half cycles of the waveform are no longer the same. DC current sense diagnostics take advantage of this phenomenon by taking the difference between positive and negative peak values within one sampling interval of the meter. If no DC current is present, the result of summing the current samples over an interval should be a value close to zero. In the presence of DC current, the totalizer value will increase significantly. This method (see Comb Filter method below) always gives accurate values regardless of the phase and amplitude of the accompanying AC current waveform.

Since the electric meter adopting the present invention is generally a multi-phase electric meter, it means that there are two-phase or three-phase currents measured by this meter, and it is possible for someone to tamper with the electric meter by connecting a half-wave rectifier circuit across the load to convert the DC The current is introduced into the device. This circuit can be added to a single phase. For this purpose, the DC detection diagnostic should be able to detect DC current on each phase bias.

The Comb Filter method for calculating the DC current detection value of each phase is illustrated in the flowchart in Figure 19. The method includes the following steps in each sampling interval:

(1) Record the sign of the first voltage sample in each interval;

(2) using the sign of the first voltage sample to detect the zero-crossing first voltage;

(3) Accumulate the second sampling current after the voltage crosses zero into the current peak accumulator (about 90°);

(4) Accumulate every fourth current sampling after the initial current sampling into the current peak value accumulator (approximately

180°);

(5) repeat step 4; and

(6) At the end of the sampling interval, divide the accumulated current peak value by the appropriate current used in the interval

value. Its effect is to normalize the results for the three different gain ranges present for the current. same

, the accumulator is cleared for the next sampling interval.

The result of the division in step 6 is a dimensionless value proportional to the phase DC current. This value will be called the DC detection value. The DC detection value is compared to a pre-selected detection threshold to determine if a DC current is likely to be present. In this example, the detection threshold is set to 3,000, since a value of 3,000 has been found to be a suitable threshold for both 200 amp and 20 amp meters.

This diagnostic uses A/D sampling to determine the voltage and current for each phase, 481 times per sampling interval (typically 1 second). Each phase current has a gain associated with it. This gain may change every sampling interval if the current magnitude changes fast enough. This is important in DC current sensing because the sensing technique requires summing the sampled current values over a certain period of time. If the selected time period is greater than the sampling interval, the possibility exists that the summation of the current values includes sampling in different gain ranges, so that the accumulated sampling loses its meaning. Therefore, it is important to normalize the resulting sampled current peak value with the appropriate current gain used in each sampling interval, as described in step (6) above.

It should be noted that the calculation of the DC detection value will only be done for one phase in any single sampling interval. Therefore, unlike other diagnostics that are performed by the meter at least every 5 sampling intervals (typically every 5 seconds), each phase of the possible three-phase current is checked three consecutive times at 5-second intervals for a total sampling time of 15 seconds per phase. Thus, the total time required for a complete current waveform diagnostic check is 45 seconds (15 seconds each for Phase A, Phase B, and Phase C).

If all three consecutive intervals of DC detection for a particular phase are found to be greater than the selected detection threshold, the presence of DC current on that phase is recorded. When all three phases have been checked, if a DC current is recorded on any phase, diagnostics are initiated. When a 45 second interval has elapsed without abnormalities being detected on any phase, the diagnostics will be turned off.

It is worth noting that the detection threshold should be set at a DC current level corresponding to the level at which the meter's current transformers begin to deteriorate so that diagnostic #5 faults can be detected and recorded before this DC level is reached.

Referring to Figure 20, this diagnostic invokes the Phase Check routine three times for each phase of the three-phase electricity. The phase inspection program samples each accumulated current of the phase at three sampling intervals, normalizes the accumulated sampled data, and stores this value as a DC detection value DVn.

Referring again to Figure 19, the check diagnostic #5 routine begins at 200 by clearing the interval readings and each fault reading for phases A, B, and C (PHA ERRCT, PHB ERRCT, and PHCERRCT), the interval counter may be a modulo 9 counter , which increments from 0-8, then back to 0, and so on. In each of the first three 5-second intervals (i.e. Interval Count = 0, 1 and 2), the program performs a phase check on Phase A at 202, and in the next three 5-second intervals (i.e. Interval Count = 3 , 4, and 5), the program performs a phase check on Phase B at 204, and for the last three 5-second intervals of the 45-second diagnostic cycle (i.e. interval count = 6, 7, and 8), the program performs a phase check on Phase C at 206 examine.

Once each phase check procedure for phase A is complete, the system determines at 208 if the DC detection value is greater than the detection threshold, and if the DC detection value is greater than the detection threshold, the phase A fault counter (Phase A ERRCT) is incremented. The phase check routine is then called three times for phase B. After each phase inspection procedure is completed, the system 20 again detects at 210 whether the DC detection value is greater than the detection threshold and sets the B-phase failure counter (B-phase ERRCT) accordingly. The phase check routine is then invoked for phase C, and the system 20 again compares the detected DC value from phase C with the detection threshold at 212 and increments the phase C fault counter (phase C ERRCT) accordingly.

Next the system determines at 214 whether the fault counter for any of phases A, B, and C is equal to three. If equal to 3, DC current is detected for that phase during three consecutive samples, the system flags a diagnostic #5 at 216 for each phase with ERRCT=3, i.e. phase A, B and C fault counters Failure (PHA CHK FAILURE, PHB CHKFAILURE, or PHC CHK FAILURE, respectively). In any case, diagnosis is complete by adding each of the PHA, PHB, and PHC CHK FAILURE counts to the Diagnostic #5 counter (representing the cumulative total of Diagnostic #5 faults).

Thus, at the end of the 45 second sampling interval, after three current checks per phase, if any of the three-phase fault counters registered a fault in all three checks, a diagnostic #5 fault would be logged. The Diagnostic #5 counter (DIAG#5 ERRORCOUNTER) reported in Tool Box mode is the sum of these three DC detection counters per phase. Automatic Maintenance Sensing

In one embodiment of the invention, the system includes logic for automatically determining the electrical maintenance supported by the meter based on the preprogrammed form factor of the meter and the angular displacement of the voltage vectors Va and Vc. This capability eliminates the requirement for the user to program the type of electrical maintenance into the meter prior to installation, thus allowing the user to take full advantage of the meter's flexible, multi-type maintenance capabilities and reducing the user's meter cataloging requirements. Additionally, the automatic electrical maintenance sensing capability ensures that the meter and any enabling systems and installation diagnostics will function correctly after installation with minimal pre-programming. Finally, the automatic service sensing capability allows the meter to be reinstalled from one service to another without preprogramming the change in service type supported by the meter.

Referring to FIG. 21 , in one embodiment, the system includes an automatic electrical maintenance sensing capability for those meters that are preprogrammed into forms 5S, 6S, 9S, 12S, 16S, 26S, 5A, 6A, 8A, and 10A . Each of the different maintenances of one of the form groups shown in Figure 19 has a unique balanced resistive load vector diagram showing the phase angle orientation of each individual phase current and voltage with respect to the A-phase voltage. In a real world application, the current phasor will move away from these balanced resistive load locations due to load changes. However, the voltage phasor does not vary with load and should be within 1° or 2° of its balanced resistive load location. Because the B-phase voltage vector does not appear on the two-element ammeter, nor does it exist in the 6S (6A) ammeter, this voltage is designed. However, the phase C voltage vector exists for all different forms and maintenance and is measured relative to the phase A voltage. Thus, for a meter of the type indicated in Figure 21, inspection of the angular position of the phase C voltage vector relative to the phase A voltage vector provides only the information needed to determine which maintenance the meter is in.

The only exception to this rule is that net and four-wire wye maintenance cannot be distinguished in the 5S, 265 form group by simply checking the C-phase and A-phase voltage vector positions. In the example of the system described here, the system simply assumes a four-wire wye maintenance under these conditions.

Thus, as shown in Figure 21, if the form factor of the meter is known, the type of electrical maintenance can often be determined by measuring the angular displacement of the voltage vector. Virtually every meter in the 8A, 10A, 9S, and 16S forms supports four-wire Wye and four-wire Delta electrical maintenance. Due to the different displacements of the voltage vectors Va and Vc in the four-wire Wye and four-wire delta systems (120° and 90° for the ABC steering), it is necessary to ensure an effective angle measurement of the phasors calculated by the system After starting an appropriate time lag, the system measures the displacement between the Va and Vc voltage vectors, and based on this displacement determines whether the meter is installed in a four-wire wye or a four-wire delta system.

Similarly, for meter form 6S or 6A, the system determines whether the displacement of the Va and Vc phase vectors is within the allowable range (preferably ±10°) from 120° to ensure that the meter is installed in the proper four-phase Y it supports Electrical maintenance is in progress. For 12S meters, the system determines whether the phase angles of the Va and Vc phase vectors are within the allowable thresholds of 60°, 120° or 180°, and if so, the determination has been installed in three-wire delta, network or single-phase power maintenance respectively electric meter. Finally, for the 5S, 5A, and 26S forms, the system checks the Va and Vc phasors to determine if their phase angles fall within the three-line triangle (60°), four-line triangle (90°), or four-line wye (120°) maintenance Each of the allowable thresholds, if yes, record the corresponding type of electrical maintenance.

It should be noted that in the 5S, 5A, or 26S forms, the system cannot distinguish between the four-wire Wye and the net maintenance because the angle between the Va and Vc phasors under ABC rotation is 120° for both maintenances. However, since there are not many applications using 5S in the network at present, in one embodiment, the system only assumes a 120° Va/Vc angular displacement is a four-wire Y-shaped power system. It should be understood that if the meter is actually used in network maintenance, the meter will still function correctly regardless of how the automatic maintenance sensing function of the meter is installed in a four-wire wye network. However, since there is a 30° phase shift between current (I) and voltage (V) in a four-wire wye, and the current and voltage phasors do not shift each other during network maintenance, if the above-mentioned automatic electrical maintenance sensing function is included If 5S, 5A or 26S meters are used in the network, some diagnostic calculations (such as the diagnostic 1 and diagnostic 4) may not truly indicate a fault.

It should be understood that such a system can also be used to automatically detect electrical maintenance with other forms of electricity meters by checking voltage phasors and/or other information obtained by automatic diagnosis.

It should also be noted that the angular displacements shown in Figure 21 are for the ABC order. In performing electrical maintenance determinations, the system preferably also checks the angular displacement values of Va and Vc for the ABC steering. It should be understood that in CBA steering, the phase C voltage phasor Vc should be 360° minus the position of Vc shown in Figure 21.

Figures 22 and 23 show a flowchart of the automatic maintenance check function employed in one embodiment of the present invention. Each time the meter is powered up, or the system diagnostics are reconfigured, the meter will perform a system check maintenance function. This can be initiated by restoring the maintenance type to an invalid value. At start-up or after a reconfiguration (for example, a power outage), the system will recognize this invalid value and automatically start the determination of a valid maintenance type.

Set a diagnostic delay of a predetermined length, preferably about 8 seconds for a meter running at 60 Hz, to allow the meter to stabilize and take angle measurements for the five possible phasors to be calculated. Therefore, during this delay period, the automatic maintenance sensing function does not operate because the Va and Vc phasor values may be unreliable. After the diagnostic delay, automatic maintenance sensing is activated at the end of each sampling interval (1 second for 60z) until a valid maintenance is found. If active maintenance is not found and any diagnostics have been initiated in the system, then such failure to determine active maintenance will be recorded as a Diagnosis #1 failure. If the diagnostics are not activated, no invalid maintenance faults are logged. In a system embodiment using the automatic maintenance sensing function, Diagnosis #1 faults for an invalid maintenance will not appear on the display unless Diagnosis #1 can be scrolled or locked, as described herein.

As long as no valid maintenance is found, the diagnostics will not be checked. Once a valid maintenance is determined (the type of maintenance recorded in the system), the automatic maintenance sensing is discontinued and the meter begins a diagnostic check of those activated system diagnostics during each sampling period, as described below.

It should be noted that in one example of the present invention, Diagnostic #1 failures operate slightly differently than normal Diagnostic #1 failures when a maintenance check failure occurs. If the maintenance type is not immediately found on the first check, a Diagnostic #1 failure is initiated as long as at least one system diagnostic function is working in the system. Diagnosis #1 is cleared as soon as a valid maintenance is found. Faults will only show on the meter if Diagnosis #1 can be scrolled or locked. This failure is always recorded in the diagnostic #1 fault counter whenever one of the system diagnostics is enabled. If no system diagnostics are enabled, this failure will not be logged. This allows the user to choose to turn off any warnings.

10°)以便通过诊断。在现场操作中，鉴于电压相矢量的变化很有限，一般在其平衡阻性负载位置1°或2°范围内，这一容限被证明是足够的。用户确定诊断It should be noted that in the implementation shown in Figures 22 and 23, the system allows a margin of voltage phasor position (preferably

10°) to pass the diagnosis. In field operation this tolerance has proven adequate given the limited variation in the voltage phasor, typically within 1° or 2° of its balanced resistive load position. User Determined Diagnosis

The system preferably allows the user to enable or disable one or more system diagnostics during meter installation. If diagnostic, the system preferably also provides user-defined parameters, as described below.

In order to activate or deactivate any of the above diagnostic tests, the user must answer the following types of prompts in each diagnostic test programming software supported by the system.

"Diagnostic #N Forbidden"

For each "diagnosis N" (where N represents one of the diagnosis numbers 1-4), when pressing the Return key, the user gets a menu, preferably including the following options:

Disable

Ignore (ignore)

Lock (Lock)

Scroll

The Disable option stops the execution of that diagnostic.

Ignore selection (if performed) means that diagnostics will affect fault status alerts (described below), but will not be displayed.

Lock selection (if enabled) will cause a diagnostic fault message to be locked on the meter display if a diagnostic fault is detected.

Scroll selection (if enabled) will generate diagnostic fault messages to be displayed during the "offtime" between each normal mode display item after a diagnostic fault is found.

In addition to the above prompts, the user will be prompted to program the type of electrical maintenance (eg 4-wire wye) supported by the particular meter installation.

For diagnostic #2, the user is also prompted to insert a value (preferably corresponding to a percentage tolerance) to program tolerance for all voltages in response to the following prompt:

Diagnosis #2 Percent Tolerance: ____________

For diagnostic #3, it is best to prompt the user for the minimum acceptable current level for the design in response to the following prompts:

Diagnostic #3 Minimum Current: ____________

Diagnostic #4 preferably also prompts the user to design the allowable phase angle tolerance by interpolating a value (1-90°) in response to the following prompt:

Diagnosis #4 Phase Angle Tolerance: ____________

If Lock or Scroll is selected, the meter will display the following information whenever a diagnostic fault is detected:

     Fault diagnosis N (where N = diagnosis number)

At the same time, the number of occurrences of this fault counter is incremented by 1 every time a fault is detected. However, as previously stated, in the preferred embodiment, the system response message and initial display of a diagnostic fault is not generated until the fault condition has occurred in three consecutive checks. Likewise, the fault does not disappear from the display until the fault is no longer present in two consecutive checks.

Additionally, during the "off time" between each normal mode meter display, the display either freezes on the fault message or scrolls the fault message through the display, depending on how the system was installed. Various other display methods consistent with the teachings of the present invention may be used. Meter self-check

Preferably, the system 20 of the present invention is suitably programmed to periodically perform a series of meter self-checks. If any fault is detected, the system will record a fault condition, display a fault code corresponding to the type of fault detected, and Take other appropriate actions depending on the type of failure.

The system preferably implements a series of procedures that periodically check for fatal and non-fatal failures. The so-called fatal failure means that the failure of detection may be unreliable recorded data, or may cause unreliable operation of the meter in the future. The system 20 preferably performs self-checking of the ammeter, checks the internal RAM of the ammeter register module, the ROM of the register module, the EEPROM of the register module, the false RESET of the register module, and the internal RAM, ROM and EEPROM of the front-end module. It is a good idea to have these meter parts checked whenever the meter is restarted or the meter is reconfigured after a power outage. If a RAM, ROM, front-end module processor failure, or other fatal failure is detected, the system 20 will display a predetermined fault code corresponding to the detected failure, lock the display on that code until the meter is reinitialized, and suspend all but communication All meter functions.

The system 20 checks for a power down fault by detecting whether the registered module processor encounters a hardware RESET without first performing a scheduled power down procedure. This situation may occur when a transient on the power supply line momentarily asserts the RESET line. One way to check for a false RESET is to write a special character into the register EEPROM as the last step in power-off handling. If this special character is not present at power-up, a spurious RESET has occurred. The system 20 will then display the power down fault code and suspend all meter functions except communications.

The system checks for RAM, ROM, EEPROM, and processor failures of the front-end modules in the same manner as described above. In the case of the combination of electricity meters according to Fig. 3, if any fatal failure of the front-end module is detected, the front-end module will stop the communication with the register module. If communication between the front-end module and the register module is interrupted for more than 5 minutes, it is sufficient to assume that one of these faults has been detected, a front-end processor failure fault code is displayed, and the 68HC11 RESET line is asserted until the front-end module resumes normal operation.

The meter self-check performed by the system preferably also includes a list of non-fatal faults such as register full-scale overflow, system clock, time-of-use (TOU), mass memory, reverse power flow, and low-voltage battery fault conditions.

For example, if the peak Kw register exceeds the preset register full-scale value, a register full-scale overflow fault will be reported. If this condition is detected, the system displays a register full-scale overflow fault which is cleared when the meter is restarted or when the fault is cleared by a predetermined programming device.

A clock fault will be reported if the minute, hour, day or month data is outside the predetermined range. In the event of a clock failure, TOU and memory size selection will be disabled and recording interval data will be suspended until the meter is reset.

If an internal TOU parameter becomes unreliable or contains a value outside its predetermined allowable range, a TOU failure will be reported. In case of TOU failure, the corresponding failure code will be displayed and TOU selection will be prohibited.

A mass storage fault will be reported if internal mass storage parameters become unreliable or outside of their predetermined allowable ranges. If a mass storage fault occurs, the corresponding fault code is displayed and mass storage selection is inhibited.

If the front-end module detects the equivalent of a full and continuous dial rotation in the opposite direction, a reverse power flow fault will be reported. This fault is always reported regardless of whether the energy is stable or not.

If a LOBAT signal is confirmed on the power combination circuit during the level check, a low battery fault will be reported. If a low voltage battery failure is detected, an appropriate fault code will be displayed, as will a clock failure, which will abort all TOU and mass storage selections. If the battery is replaced before any power outage, the low battery fault will be cleared when the battery voltage rises above a predetermined threshold. However, if the battery voltage falls below the threshold after a power outage, the meter must be reset to clear the fault.

The system preferably checks registers for full-scale overflow at the end of each request interval, and preferably checks for clock, TOU, and mass memory failures at power-up, at 2300 hours, and at any type of meter reset. Reverse power flow faults are best checked by the system every second, and low voltage battery faults at power-up and every interval.

In a preferred embodiment of the system 20, the system allows the user to select which meter self-check functions to perform. In the preferred embodiment, if any one of the selected non-fatal faults is detected, during the off-time between normal display items, the system displays a predetermined fault code corresponding to the detected fault. Alternatively, the system may allow the user to program the system to lock the display on the fault code of any non-fatal fault upon detection of any such fault. In this case, actuation of a switch by the user will cause the meter to scroll once through the normal display menu and then latch on to the non-fatal fault display.

It should be noted that, in the preferred embodiment, fatal fault checking cannot be disabled. If a non-fatal fault check is not selected, it will not be displayed and flagged.

Those skilled in the art will appreciate that various display methods can be used. For example, the system can be programmed to lock the display on a fault code corresponding to any detected non-fatal fault until the magnetic switch is actuated. Once the magnetic switch is activated, the system scrolls through its normal display and then locks on to the display for non-fatal fault codes. Alternatively, the system may be programmed to periodically display any or all non-fatal fault codes by continuing to scroll through a predetermined display list.

Other meter components may be checked periodically in the same manner using conventional methods and programmed fault codes which may be displayed when appropriate to alert the user to possible data interruptions or unreliable meter operation. toolbox mode

The diagnostic toolbox is preferably a set of fixed selection display items in the format shown in FIG. In the preferred embodiment, the toolbox display is accessed via a magnetic spring switch at the 12 o'clock position on the dial and activated by holding the magnet against the spring switch for at least 5 seconds. This can be done by the user placing a magnet on top of the meter.

When accessed, each display item of the toolbox is displayed in the order shown in Figure 14 and shown respectively. Once the meter is in toolbox display mode, all toolbox display items will scroll at least once. When the magnet is removed, the meter will finish scrolling to the bottom of the toolbox display list and then resume normal mode operation. The TEST alarm will flash twice per second for the entire time the meter is in toolbox mode.

All #DIAG Error counters are preferably cleared by an external device such as a laptop PC or via normal communication. In the preferred example, the maximum value of each counter is 255.

When in toolbox mode, the meter works as usual, which ensures that even if the magnet stays on the top of the meter for an extended period of time, the meter operation is still unaffected. During the entire time the meter is in toolbox mode, the system continuously modifies the displayed toolbox parameters as their values change.

In toolbox mode, the Watt Disk Emulator turns at a speed of 1.33 seconds per revolution in the direction of the power flow of the phase whose information is being displayed at that moment. For example, when Phase A voltage, current, voltage phase angle, and current phase angle are being displayed, the Watt Disk Emulator rotates once per second in the direction of Phase A power flow. Once the Phase B value is displayed (if present), the Watt Disk Emulator turns to reverse if the Phase B power flow is opposite to that of Phase A. Turn off the Watt Disk Emulator when all four spin failure counters are displayed.

Since the user requires continuous potential indication, the three-phase potential indications (preferably represented by V _A , V _B and V _C ) all appear on the display. These indications are "ON" as long as the corresponding voltage is above a predetermined threshold. This threshold is best defined as 75% of the lowest voltage value at which the meter is rated to operate. If any voltage drops below the threshold, its indicator flashes preferably at a rate of 2 times per second,

When there are more than one fault at the same time, according to the predetermined priority, only the information related to one of the faults will be displayed. In a preferred embodiment of the system, the following priorities are established:

1. Meter self-check faults take precedence over system and installation diagnostic faults.

2. Since only one system and installation diagnostic fault can be displayed at a time, the highest priority

The incident for will be an incident displayed with a predetermined prioritized list.

If there are two or more system and installation diagnostic faults, the fault with the highest priority will be the one that is displayed and that triggers the output contact to close. If this fault is repaired, the next highest priority fault still present will be displayed and will trigger the output contact to close again. Therefore, as long as one or more diagnostic faults are triggered, the output contact is always assumed to be closed (fault status alarm).

As mentioned above and shown in FIG. 14, the toolbox display preferably also displays the instantaneous values of current and voltage for each phase. and its phase relative to the Phase A voltage. From this information, the user is able to construct a phasor diagram that helps define the correct installation and operation of the meter. This display also shows the cumulative number of diagnostic faults per diagnostic since the last system reset operation.

Figures 14 and 15 respectively give examples of the required relationship between the phasor vector diagram and the toolbox display for a three-phase meter installation. Using the phase current, voltage, and phase angle information given in the toolbox display, the user should be able to construct a vector diagram as shown in Figure 15. This will allow the user to get a snapshot print of the power system status and to identify any features and faults. As mentioned earlier, the toolbox will also give the status of four diagnostic counters, which will provide users with more detailed system status information. Phase angle calculation

In the preferred embodiment, the sum toolbox used in System Diagnostics #1 and #4 displays the required phase angle information for phase current and voltage from the accumulated current and current values for each phase and the accumulated products Q and Y (below definition) to determine. Phase A voltage is best used as a reference (or reference phasor) for other angles. Therefore, the phase A voltage angle appears in the display as 0.0°. For (I _A , I _B , I _C , V _B , V _C ) these five other phase angle values will be reported relative to the Phase A voltage value and will always be given relative to a hysteresis reference value. 1. The phase angle between V _A and I _A

If the power (Power) and apparent power (Apparent Power) are known, the power factor can be deduced. The relationship is as follows:

Apparent Power = I _RMS V _RMS

Power Factor = Power/Apparent Power = Power/I _RMS V _RMS The phase angle (θ) between voltage and current can be calculated as follows:

                    θ = arc cos (power factor)

The device of the present invention can also determine whether the current is leading or lagging the voltage by checking the sign of the reactive power. If the reactive power is positive, the current lags the voltage, and if the reactive power is negative, the current leads the voltage.

In this embodiment, the power, RMS voltage and RMS current of each phase of the meter are calculated every 60 line cycles. This is done by taking 481 voltage and current samples over 60 line cycles. The necessary multiplications and accumulations are done first, and then these values are averaged to give the power, RMS voltage and RMS current for a given 60 line cycles. These quantities are then used to calculate the power factor of each phase at the end of every 60 cycles.

Reactive power can be calculated in the same way as power, except that a 90° phase shift must be induced between the current and voltage measurements. 2. Derivation of general phase angle calculation method

As demonstrated below, the method of calculating the V _A to I _A phase angle can be generalized to calculate any reference phasor (such as V _A ) with any other phasor (such as V _B , I _B , V _C , or I _C ) .

Referring now to Figure 16, consider the following two sine waves of the same frequency, different amplitudes, and phase shifted from each other:

a(t)=Acos(ωt)

            b(t) = Bcos(ωt-θ)

Denoting the cosine phase angle as (ωt-θ) implicitly assumes that θ represents a lagged phase shift of b(t) with reference to a(t). The respective positions indicate whether b(t) reaches its maximum value before or after a(t) in time. If b(t) reaches its maximum after a(t), it is said to lag a(t). If b(t) reaches its maximum value before a(t), it is said to lead a(t).

For the purpose of separating the phase angle θ, the average of the products of these two sine waves will be calculated. This average will be marked with Q. The equation for finding the average is as follows: $Q=\frac{1}{T}\underset{0}{\overset{T}{\∫}}A\cos \left(\mathrm{\ωt}\right)B\cos (\mathrm{\ωt}-\mathrm{\θ})\mathrm{dt}.$ where A and B represent the amplitudes of the sine waves a(t) and b(t), respectively. The amplitude X _MAX of a sine wave is related to its RMS (root mean square) value X _RMS , expressed by the following formula: $x_{\mathrm{MAX}}=\sqrt{2}{x}_{\mathrm{RMS}}$ therefore, $A=\sqrt{2}{A}_{\mathrm{RMS}},B=\sqrt{2}{B}_{\mathrm{RMS}}$ Substituting these relations into the equation for Q, we get:

Q = A _RMS B _RMS cos θ or $\cos \mathrm{\θ}=\frac{Q}{A_{\mathrm{RMS}}{B}_{\mathrm{RMS}}}$ Finally got:

Thus, given the average of the product of two sine waves and the RMS values of the two individual waves, the phase angle between the two waves can be calculated. With this information alone we cannot determine whether b(t) is lagging or leading a(t). However, if the sign of the angle θ is known, it can be determined whether the angle is leading or lagging.

To determine the sign of this angle, consider the average of the product of two sine waves, and let a(t) have a phase shift of 90° or π/2 radians. The expression of the phase shift variant of a(t) is as follows: $\hat{a}\left(t\right)=A\cos (\mathrm{\&omega;t}-\frac{\mathrm{\&pi;}}{2})$ The average value of the product of a(t) and b(t) will be called the quantity Y. The equation is as follows: Solving this integral gives the following relation: $Y=\frac{\mathrm{<figure-callout\; id="2"\; label="AB"\; filenames="C96191021.600511.png"\; state="\{\{state\}\}">AB</figure-callout>}}{2}\sin \left(\mathrm{\&theta;}\right)$

考察反余弦(arccosine)和反正弦(arcsine)函数幅角的符号，即可确定这个角度是滞后角还是领先角。既然正角相应于滞后角，则下面的关系用来确定这个角度是滞后角还是领先角就是对的：Thus, if the mean (Q) of the product of two sine waves is known, the mean (Q) of these sine wave products delayed and phase shifted by 90° from the reference wave is known, and the RMS value of each wave is known, then The phase angle can be calculated and it can be determined whether the non-reference wave is lagging or leading the reference wave. The two equations that can be used to determine the magnitude of the phase angle are as follows:

By examining the sign of the argument of the arccosine and arcsine functions, we can determine whether the angle is a lagging angle or a leading angle. Since a positive angle corresponds to a lagging angle, the following relation is true for determining whether the angle is lagging or leading:

Argument of arcsine (+), argument of arcsine (+)

- Hysteresis 0° to 90°;

Argument of arcsine (-), argument of arcsine (+)

- Lag 90° to 180°;

Argument of arcsine (-), argument of arcsine (-)

- leading 90° to 180°;

Argument of arcsine (+), argument of arcsine (-)

-Leading 0° to 90°. Therefore, if the Q, Y and RMS values of a(t) and b(t) can be obtained, the phase angle between these sine waves can be determined.

The above technique for finding the phase angle will work for any voltage or current pair. For example, to determine the phase angle between V _B and _VA , the two quantities that must be calculated are the average of the two wave products (Q _VAB ), and the average of these two wave products with V _A shifted by 90° ( Y _VAB ).

As previously stated, the electricity meter incorporated into the preferred embodiment of system 20 samples _VB and _VA 481 times every 60 line cycles. The product of V _A and V _B is calculated for each of the 481 samples and accumulated over the sampling interval, then the average of the two wave products (Q _VAB ) can be calculated at the end of the sampling interval. The equation for Q _VAB is as follows: $Q_{\mathrm{VAB}}=C\frac{\underset{\mathrm{no}=1}{\overset{481}{\mathrm{\&Sigma;}}}{V}_{A\left(\mathrm{no}\right)}\&times;V_{B\left(\mathrm{no}\right)}}{481}$ where C is a calculated scale factor used to compensate phase voltage drops to measurable levels.

Y _VAB can be obtained from the following formula in a similar way: $Y_{\mathrm{VAB}}=C\frac{\underset{\mathrm{no}=1}{\overset{481}{\mathrm{\&Sigma;}}}{V}_{A(\mathrm{no}-1)}\&times;V_{B\left(\mathrm{no}\right)}}{481}$ In the formula, C for calculating Y _VAB is the same as C for calculating Q _VAB , and V _A(n-2) is the voltage V _A that is sampled twice before sampling V _An .

Sampling is designed such that two consecutive samples of a signal are separated by 44.91°. Therefore, if the voltage is sampled from two samples ago, this will produce an 89.82° phase shift of almost 90°.

It should be noted that instead of sampling with a phase shift of _VA , other quantities may be phase shifted by 90° to calculate the phase angle. This will result in a Y _VAB value of the same size. However, since the phase angle is shifted by 180°, the sign information will be changed. Using this formula, the following sign relationship exists between the arccosine and the arcsine function argument:

Argument of arcsine (+), argument of arcsine (-)

- Lag angle between 0° and 90°;

Argument of arcsine (-), argument of arcsine (-)

- Lag angle between 90° and 180°;

Argument of arcsine (-), argument of arcsine (+)

- Leading angle between 90° and 180°;

Argument of arcsine (+), argument of arcsine (+)

-Leading angle between 0° and 90°.

If the new value of the phase angle necessary for the toolbox display is to be calculated for each sampling interval, the above ten product and accumulation terms must be calculated for each sampling interval. Due to the excessive use of processor time and the RAM required to accumulate all ten terms in each sampling interval, it is best to consider only one pair of these terms for each sampling interval. This limits processing time and RAM usage so that new phase angle values are available for toolbox display every five sample intervals.

In a preferred embodiment, product terms are computed and accumulated in the following order:

1. V _A * I _A and V _A(-90°) * I _A of the first sampling period-phase angle I _A ;

2. V _A * I _B and V _{A (-90°)} * I _B of the second sampling period-phase angle I B;

3. The third sampling period - V _A * I _C and V _A(-90°) * I _C of the phase angle I _C ;

4. Fourth sampling period - V _A * V _B and V _A(-90°) * V _B of the phase angle V _B ; and

5. Fifth sampling period - V _A *V _C and V _A(-90°) *V _C of the phase angle V _C . After the fifth sampling interval, the sequence restarts and the necessary Q and Y values for phase angle _IA are accumulated. A sample of V _A is stored at each sampling interval. This requires that at each interval two additional values for _VA be stored, ie the two previous values of _VA .

In this embodiment, these functions are implemented in 68HC11 assembly code. The multiplication and accumulation of these product terms occurs in the front-end sampling interrupt routine. Voltage values are 8-bit values, while current values are 12-bit values. Since V _A is always involved in any product, this means that some products will be 8x8 bits and some will be 8x12 bits. Since it is desirable to use the same algorithm for all multiplications, the 8 bit values are expanded to 12 bit values so that only 8 x 12 bit multiplications are used in the preferred embodiment.

Expand the 8-bit voltage value of V _B and V _C to a 12-bit value through the sign, so that all the multiplication and accumulation of the product items are processed by two algorithms in order to obtain the phase angle, one is the product item of the Y value One is the accumulation of the product term of the Q value. The sign extension of the voltage values V _B and V _C is performed in each sampling interval. This necessitates a special check to identify the sampling intervals in which these quantities are needed, since they are available at each sampling interval.

The full 12-bit values for current and voltage are best stored in 16-bit registers in memory because memory is partitioned on byte boundaries.

The front-end sampling routine must have a way to identify which product terms are to be computed at each sampling interval. Preferably, the counter identifier is used for indexing to access the correct value for the multiplication necessary for the accumulation of the Q and Y values.

To accumulate the two product terms, two accumulators are placed next to the memory map. Each accumulator is the same size since both do 8x12 bit multiplications. The maximum possible cumulative value is as follows:

The maximum 8-bit value = 128

Maximum 12-bit value = 2048

Maximum accumulation result = 481*128*2048 = 07840000 (hexadecimal) Therefore, each accumulator is 4 bytes long in order to accumulate the worst case result. Therefore, two 4-byte accumulators are bypassed to accumulate each pair of product terms for each sampling interval.

At the end of each sampling interval, the results in the two 4-byte accumulators are stored in the two 4-byte holding areas to await background processing necessary to complete the calculation of the phase angle during the next sampling period.

Once the accumulated pair of product terms has been transferred to the holding registers at the end of a sample interval, subsequent calculations necessary to determine the phase angle are performed in the background during the next sample while the next pair of product terms are accumulated in the foreground. These daemons must also be able to determine which pairs of accumulative product terms they want to compute. A separate counter identifier is used for this daemon, which operates in the same manner as the counter identifier for the front-end sampling interrupt. However, since this identifier is always one count after the front-end module samples the interrupt program counter identifier, it is possible to use the same counter.

The electricity meter 34 shown in Figures 2, 3, 17A-B and 18A-B, specifically configured with the system 20 of the present invention, is a solid-state single function Kw/Kwh electricity meter using digital sampling techniques, in addition to providing the diagnostics produced by the system 20 of the present invention In addition to the information, general Kw/Kwh demand, hours of use and other general real-time billing information are provided. The electricity meter 34 is preferably programmed using software running on an IBM compatible personal computer under the MS-DOS operating system. Such software includes logic that prompts the user to provide meter configuration parameters, preferably including installation prompts that provide user-determined parameters for diagnostics supported by the system 20 of the present invention, so that a hand-held personal computer can be plugged into a communication port on the meter and be used at any time. Program the meter at installation.

17A-B illustrate the front end module 44 of the electricity meter 34 preferentially incorporating the system 20 of the present invention. The front end module 44 preferably includes a Notorola MC68HC11KA4 microprocessor 140 operating in monolithic mode, an integrated 8-bit A/D converter 142 (used as the voltage converter 26 in the system 20 of the present invention), generally indicated at 144 24K bytes of read-only memory (ROM), 640 bytes of electrically erasable programmable read-only memory (EEPROM) and 768 bytes of random access memory (RAM). ROM and EEPROM contain diagnostic logic, while RAM is used as the memory of the present invention. An external 12-bit A/D converter shown at 146 is used as the current converter 28 of the system 20 of the present invention.

An additional fault condition alert function can be implemented as an option on the front end module 44 . This function uses a data line (for example) to an external communication device, which can be activated as soon as a fault condition is determined. The inventive system 20 may utilize this selection function to enable and account for the existence of any of the fault conditions diagnosed by the inventive system 20 .

An option board 146 can be plugged into the front end module 44 to provide various signals to the outside world. For example, a fault condition alarm can be set to a low current solid state or mercury-wetted relay to indicate when one or more diagnostic faults have been detected. Other auxiliary functions such as automatic meter reading or real-time billing can be implemented on the option board, or a similarly constructed option board for use with the front-end module.

Referring now to Fig. 18A-B, the register module 48 of the electric meter of preferential configuration system 20 of the present invention comprises a NECuPD75316GF single-chip microprocessor 148, 16K byte ROM (150 represents), 512 * 4 bit RAM (152 represents), and a A 96-segment LCD display driver 154 is adapted to drive an LCD display 156 like the particular type of display 33 shown in FIG. 3 and used in the preferred embodiment of the electricity meter 34.

Serial data will be transferred between the front end module 44 and the register module 48 over the four-wire synchronous serial data lines indicated at 158 in FIGS. 17A-B and 160 in FIGS. 18A-B , respectively. The front-end module will monitor and update the status of all diagnostics performed by the system 20 of the present invention, and periodically (preferably once per second) post these statuses to the register module 48 for display via the above-mentioned serial communication line, and upon power down When storing volatile data. In addition, any instantaneous quantities required for the toolbox display of the present invention must be passed from the front-end module to the register module. The front-end module 44 also passes various other conventional meter information to the register module 48, such as energy usage (in Kwh) recorded for the last 60 line cycles, as well as energy flow direction (send or receive), current demand and Interval end message.

Information that may be passed from register module 48 to front end module 44 generally includes cycle meter register status information.

Referring again to Figures 17A-B, the front-end module 44 enables per-phase voltage, current and wattage to be measured for a sampling interval. As mentioned earlier, the front-end module preferably takes 481 samples every 60 line cycles, which corresponds to 481 Hz when the line frequency is 60 Hz and 401 Hz when the line frequency is 50 Hz. This sampling frequency is recalculated every 60 cycles based on the measured line frequency. As previously stated, when the system of the present invention is incorporated into an electric meter of the type shown in FIG. 3, its diagnostic functions (including determination of instantaneous per-phase current, voltage, wattage and phase angle) are preferably performed by the front end module 44.

Referring again to FIGS. 3 and 18A-B , the register module 48 preferably performs the function of driving the LCD display 33 in the electricity meter 34 . As mentioned above, the toolbox display of the present invention can be realized by actuating an alternate display switch (not shown) according to a predetermined cycle. On startup, toolbox display mode is triggered, and the display will scroll the entire toolbox display menu, as described earlier in this article. During the display of the toolbox, the "TEST" icon preferably flashes continuously, and the watt-disk simulator (represented by the five rectangular icons on the lower portion of the display 33) will scroll at a rate of about one revolution every 1.33 seconds. The direction of the watt-disk simulator will be the same as the direction of power flow for the displayed phase (left to right when receiving, right to left when transmitting). When the end of display is reached and the alternate display switch is no longer activated, the meter will remain in toolbox display mode. It should be noted that the meter will continue to perform all normal mode meter operations while the toolbox display sequence is in effect, as previously stated.

When the alternate display switch is not activated, the ammeter display 33 operates on the ammeter 34 in a normal display mode.

Communication to and from the electricity meter may also be accomplished through the front end module 44 via a connection to the optical port 162 .

Therefore, the whole electric meter system diagnosis of the present invention includes besides reminding field personnel to pay attention to any fault found, also provides the ability of continuous self-inspection of electric meter internal parts under the condition of not interrupting electric meter operation, and this system also provides frequent system diagnostic check and display The ability to diagnose results so that relevant diagnostic data can be provided to system personnel during or after meter installation.

The system provides the flexibility to allow the user to program the system to select and determine the specific maintenance functions and parameters appropriate to be supported by the meter installation.

Finally, the toolbox display capability of the present invention also allows periodic display of important information about the inner workings of the meter and the maintenance features supported by the meter without interrupting normal maintenance and meter operation.

While the best modes for carrying out the invention have been described in detail, those skilled in the art to which this invention relates will recognize various designs and examples for practicing the invention as defined by the following claims.

Claims (12)

1. an electronic electricity meter detection electric system diagnostic device comprises:

A microprocessor;

The storer that rationally is connected with microprocessor;

Be used for carrying out automatically periodically pre-selected test that ammeter detects and the logical circuit that writes down measured any fault;

Be used for carrying out automatically periodically the logical circuit that any result who exceeds predetermined threshold was tested and write down in a series of pre-selected system diagnostics;

Be used for showing expression because of in predetermined period the ammeter of the doing display device of testing the failure message of one or more faults of finding, and

Be used for showing the display device of expression because of any Fault Diagnosis information of in predetermined period, doing the ammeter diagnostic test and finding.

2. the system of claim 1 also comprises and is used for automatically measuring the logical circuit that the electricity that ammeter is housed is safeguarded type.

3. the system of claim 2 wherein is used for measuring automatically the electricity that ammeter is housed and safeguards this mensuration of execution in the initialization procedure of logical circuit when ammeter is installed of type.

4. the system of claim 3 wherein is used for measuring automatically the electricity that ammeter is housed and safeguards that the logical circuit of type carries out this mensuration when ammeter reconfigures.

5. the system of claim 2 wherein is used for measuring the electricity that ammeter is housed and safeguards that the logical circuit of type carries out this mensuration automatically and periodically in the ammeter normal work period.

6. an ammeter electric system diagnostic device comprises:

A microprocessor;

The storer that rationally is connected with microprocessor;

Be used for automatically measuring the logical circuit of the electric system type that ammeter is housed.

7. the system of claim 6 also comprises the logical circuit that is used for determining the power system voltage information record thus.

8. the system of claim 6, the logical circuit that wherein is used for measuring power system voltage information comprises in order to measure the logical circuit of at least one voltage phase vector with respect to the phase angle of a selected reference voltage phase vector, and wherein be used for measuring electricity and safeguard that the logical circuit of type comprises and be used at least one phase vector with respect to the voltage phase angle of a selected reference phase vector and a different set ofly may safeguard that the pre-selected voltage phase vector angle of type compares by electricity, if and had electricity to safeguard type, would determine that according to voltage phase vector angle electricity safeguards the logical circuit of type.

9. the system of claim 8 wherein is used for measuring electricity and safeguards that the logical circuit of type is according to C phase voltage vector V _C, A phase voltage vector V _AAnd the predetermined form factor of ammeter carries out this mensuration.

10. the system of claim 9 wherein is used for measuring at least one phase vector and comprises with respect to the logical circuit of the phase angle of a selected reference phase vector and be used for storage corresponding to benchmark phase vector X _BThe accumulating values of the instantaneous voltage that records, storage are corresponding to another selected reference phase vector X _NThe accumulating values of the instantaneous voltage that records, in a predetermined period, measure and be labeled as X respectively _{B (RMS)}And X _{N (RMS)}X _BAnd X _NThe RMS value, measure X _{B (RMS)}And X _{N (RMS)}Product P, measure corresponding to X _BAnd X _NThe mean value Q of two sinusoidal wave products, and measure and be labeled as X _{B (90 °)}Corresponding to X _BThe logical circuit of the mean value Y of two sinusoidal wave products of phase shift modification.

11. the system of claim 10, logical circuit wherein also comprises and is used for measuring the phase angle theta size of a phase vector with respect to a selected reference phase vector, and size equals arc sin (Q/P), logical circuit.

12. the system of claim 11, benchmark phase vector X wherein _BBe A phase voltage phase vector, its another phase vector X _NIt is C phase voltage phase vector.

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