JP5608465B2 - Resistance value judgment device - Google Patents

Description

  The present invention relates to a resistance value determination device.

  The resistance value of the ground insulation resistance in a direct current circuit such as a direct current power supply device is lowered, for example, when the insulation coating of the power cable is damaged. When the resistance value of the ground insulation resistance decreases, a ground fault occurs easily in the DC circuit. Therefore, in order to grasp the sign of the ground fault, for example, the resistance value of the ground insulation resistance of the DC circuit may be measured to determine whether the insulation state of the DC circuit is good or not (see, for example, Patent Document 1). .

JP 2006-343267 A

  By the way, since the resistance value of the ground insulation resistance of the DC circuit generally varies greatly depending on the humidity, the quality of the insulation state of the DC circuit can be accurately determined only by the measured resistance value of the ground insulation resistance. Is difficult.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a resistance value determination device capable of accurately determining whether a DC circuit is in an insulated state.

In order to achieve the above object, a resistance value determination apparatus according to one aspect of the present invention stores in advance data indicating a relationship between a resistance value of a ground insulation resistance of a DC circuit and humidity around the DC circuit. And a measurement unit that measures the resistance value of the ground insulation resistance and the humidity around the DC circuit at every predetermined cycle, and the measurement every time the measurement unit measures the humidity around the DC circuit. Based on the humidity measured by the unit and the data, the acquisition unit for acquiring the resistance value of the ground insulation resistance corresponding to the measured humidity, or the resistance value measured by the measurement unit is smaller than a predetermined value, Alternatively, when the caution display indicating that the ground insulation resistance is deteriorated, which is performed when the rate of decrease in the resistance value measured by the measurement unit is greater than a predetermined value, has not continued for a predetermined period, the acquisition unit acquires Measured resistance value and the measurement unit Based on the resistance value, the variation range from resistance value acquired by the acquisition unit in the ground insulation resistance until the measured resistance value by the measurement unit determines repeatedly whether greater than a predetermined, the If the variation width is greater than the predetermined, and a determination unit which Ru is output a warning to the effect that the insulation state of the DC circuit is deteriorated.

  ADVANTAGE OF THE INVENTION According to this invention, the resistance value determination apparatus which can determine the quality of the insulation state of a DC circuit accurately can be provided.

It is a figure which shows the structure of the direct-current power supply device 10 provided with the resistance value determination apparatus 30 which is one Embodiment of this invention. It is a figure which shows the relationship between the initial resistance value Rp0 of the ground insulation resistance 40, and humidity. It is a figure which shows the functional block which the control apparatus 62 implement | achieves. It is a flowchart which shows the process which the measurement part implements. It is a flowchart which shows the process which the measurement part implements. It is a figure which shows the equivalent circuit of the DC power supply device 10 when the power cable 22 is grounded. It is a figure which shows the waveform of the change of the voltage Vp when the power cable 22 is grounded. 5 is a flowchart illustrating an example of a process for determining whether the insulation state of the DC power supply device 10 is good or bad.

  At least the following matters will become apparent from the description of this specification and the accompanying drawings. FIG. 1 is a diagram illustrating a configuration example of a DC power supply device 10 provided with a resistance value determination device 30 according to an embodiment of the present invention.

  The DC power supply device 10 is a device that converts alternating current to direct current and outputs electricity as a power source for operating an electrical device (not shown) while storing electricity in the storage battery 20, and includes a rectifier (not shown), the storage battery 20, and a relay. 21, power cables 22 and 23, and a resistance value determination device 30. Note that the DC power supply device 10 is a DC circuit that generates a DC voltage, and is provided, for example, in a substation of the power system.

  The relay 21 is a ground fault detection relay that is connected between the power cables 22 and 23 and detects the occurrence of a ground fault in the DC power supply device 10. When the relay 50 of the resistance value determination device 30 to be described later is turned on, the relay 21 is connected to the internal resistance (not shown) of the relay 21 from the power cables 22 and 23 and the current flowing to the ground via the relay 50. It is detected whether or not a ground fault has occurred in the power supply device 10, that is, the DC circuit.

  The power cable 22 is a cable to which the positive voltage Vp of the storage battery 20 is applied, and the power cable 23 is a cable to which the negative voltage Vn of the storage battery 20 is applied. In the present embodiment, for example, the ground insulation resistance 40 and the ground capacitance 41 of the DC power supply device 10 are generated between the power cable 22 and the ground, and the ground insulation resistance is formed between the power cable 23 and the ground. 42 and ground capacitance 43 are generated. In the present embodiment, the resistance values of the ground insulation resistors 40 and 42 are Rp and Rn, respectively, and the capacitance values of the ground capacitances 41 and 43 are Cp and Cn, respectively.

  The resistance value determination device 30 measures the temperature and humidity around the ground insulation resistors 40 and 42, the ground capacitances 41 and 43, and the DC power supply device 10, and determines whether the insulation state of the DC power supply device 10, that is, the DC circuit is good or bad. judge. The resistance value determination device 30 includes a relay 50, a switch 51, a resistor 52, a sensor 60, a storage device 61, a control device 62, and a display device 63.

  The relay 50 is a switch for controlling the operation of the relay 21 based on an instruction from the control device 62. Specifically, when the relay 50 is turned on, a current flows from the power cables 22 and 23 to the ground through the internal resistance (not shown) of the relay 21 and the relay 50 in the event of a ground fault. It is possible to detect a fault. On the other hand, when the relay 50 is turned off, the current flowing from the power cables 22 and 23 to the ground via the relay 21 becomes zero, so the relay 21 stops detecting the ground fault. When the relay 50 is off, the impedance between the relay 21 and the ground is sufficiently larger than the ground insulation resistance 40 and the like.

  The switch 51 is a switch for forcibly grounding one of the power cables 22 and 23 via the resistor 52 based on an instruction from the control device 62. In the present embodiment, the resistance value of the resistor 52 is R1.

  The sensor 60 measures the temperature and humidity around the DC power supply device 10 based on an instruction from the control device 62.

  The storage device 61 stores initial data indicating the relationship between the initial resistance values Rp0 and Rn0 of the ground insulation resistances 40 and 42 and humidity, program data executed by the control device 62, and the like. The initial resistance values Rp0 and Rn0 of the ground insulation resistors 40 and 42 are, for example, the resistance values of the ground insulation resistors of the power cables 22 and 23 before the power cables 22 and 23 are actually used. Therefore, the initial data is obtained by measuring the resistance value of the ground insulation resistance of the power cables 22 and 23 before actual use, for example, in a laboratory for each of a plurality of humidity. The initial data is data having a correlation as shown in FIG. 2, for example, and the resistance values Rp0 and Rn0 decrease according to the humidity.

  The control device 62 measures the ground insulation resistances 40 and 42 and the ground capacitances 41 and 43, and determines the quality of the insulation state of the DC power supply device 10 using the measurement results and initial data. The control device 62 includes, for example, a microcomputer and implements various functions by executing program data stored in the storage device 61. Specifically, as illustrated in FIG. 3, the control device 62 realizes the functions of a measurement unit 70, an acquisition unit 71, determination units 72 to 75, a caution display unit 76, and an alarm output unit 77.

  The measurement unit 70 measures the ground insulation resistances 40 and 42 and the ground capacitances 41 and 43 at predetermined intervals, and causes the sensor 60 to measure the temperature and humidity around the DC power supply device 10. Specifically, the measurement unit 70 sequentially grounds the power cables 22 and 23 and measures the ground insulation resistances 40 and 42 and the ground capacitances 41 and 43 based on the voltages Vp and Vn at that time. Details of the measurement unit 70 will be described later. Further, the sensor 60 and the measurement unit 70 correspond to a measurement unit.

  The acquisition unit 71 selects and acquires resistance values Rp0 and Rn0 corresponding to the measured humidity from the initial data every time the measurement unit 70 measures the humidity. As described above, since the initial data is data having a correlation as shown in FIG. 2, when the humidity is determined, the resistance values Rp0 and Rn0 are also determined.

  Each of the determination units 72 to 75 determines whether or not the result measured by the measurement unit 70 is larger than a predetermined value in order to determine whether the insulation state of the DC power supply device 10, that is, the DC circuit is good. Although details will be described later, in the present embodiment, a plurality of determination units 72 to 75 using different determination methods are realized, so that even if the measurement environment or the like changes, the DC power supply device 10, that is, the DC circuit The insulation state can be accurately determined.

  The determination unit 72 (capacitance value determination unit) determines whether or not the capacitance values Cp and Cn of the ground capacitances 41 and 43 measured by the measurement unit 70 are larger than a predetermined value (for example, 400 μF).

  The determination unit 73 (resistance value determination unit) determines whether or not the resistance values Rp and Rn of the ground insulation resistances 40 and 42 measured by the measurement unit 70 are larger than a predetermined value (for example, 100 kΩ).

  The determination unit 74 calculates a decrease rate of the resistance values Rp, Rn based on the resistance values Rp, Rn measured at predetermined intervals, and whether the calculated decrease rate is greater than a predetermined value (for example, 50%). Determine whether or not.

  The determination unit 75 calculates temporal changes in the resistance values Rp and Rn, and determines whether the temporal changes, that is, the decrease in the resistance values Rp and Rn is greater than a predetermined value. Specifically, the determination unit 75 subtracts the measured resistance values Rp and Rn from the initial resistance values Rp0 and Rn0 acquired by the acquisition unit 71 to determine whether or not the change width is larger than a predetermined value. judge. For this reason, even when the resistance values Rp and Rn change due to the influence of humidity, the determination unit 75 can accurately determine the quality of the insulation state of the DC power supply device 10, that is, the DC circuit. .

  When the determination unit 72 determines that the capacitance values Cp and Cn are larger than the predetermined value, the caution display unit 76 causes the display device 63 to display a caution display indicating that the ground capacitances 41 and 43 are deteriorated. . Further, when the determination unit 73 determines that the resistance values Rp and Rn are smaller than the predetermined value or the determination unit 74 determines that the decrease rate is larger than the predetermined value, the caution display unit 76 A caution display indicating that 40 and 42 are deteriorated is displayed on the display device 63.

  If the warning output is displayed on the display device 63 continuously for a predetermined period (for example, one week) or if the change with time is larger than the predetermined by the determination unit 75, the alarm output unit 77 It is determined that the insulation state of 10 has deteriorated, and an alarm is output.

== Details of Measuring Unit 70 ==
Here, details of a process in which the measurement unit 70 measures the ground insulation resistance 40 and the like based on the voltages Vp and Vn will be described with reference to FIGS.

  First, the measurement unit 70 turns off the relay 50 so that the internal resistance of the relay 21 does not affect the resistance value of the ground insulation resistance 40 or the like (S100). Then, the measurement unit 70 connects the switch 51 to the positive-side power cable 22, grounds the power cable 22 via the resistor 52, and starts measuring the voltages Vp and Vn (S101). As a result, the DC power supply device 10 is equivalent to a circuit as shown in FIG. Further, as shown in FIG. 7, the voltage Vp when the power cable 22 is grounded depends on the time constant τ 1 determined by the ground insulation resistances 40 and 42 and the resistance 52 and the ground capacitances 41 and 43. Decrease at a slow speed. Here, the voltage Vp before the power cable 22 is grounded is assumed to be the voltage Vp0. For this reason, when the time constant τ1 elapses after the power cable 22 is grounded, the voltage Vp drops from the voltage Vp0 to the voltage Vp0 × 1 / e (e≈2.71).

  Then, the measurement unit 70 determines whether or not the changes in the voltages Vp and Vn are sufficiently small and the voltages Vp and Vn are stabilized (S102). When determining that the voltages Vp and Vn are stable (S102: YES), the measuring unit 70 stores the time constant τ1 and the voltages Vp and Vn at the time of the determination in the storage device 61 (S103). Here, the voltages when the voltages Vp and Vn are stabilized are Vp1 and Vn1, respectively. Then, the measurement unit 70 operates the switch 51 to cancel the ground fault of the power cable 22 (S104), and turns on the relay 50 to bring the voltages Vp and Vn to the level before the occurrence of the ground fault (S105). ).

  Thereafter, the measurement unit 70 determines whether or not the levels of the voltages Vp and Vn are the levels before the occurrence of the ground fault, that is, whether or not the voltages Vp0 and Vn0 are reached (S106). When the voltages Vp and Vn reach the level before the occurrence of the ground fault (S106: YES), the measurement unit 70 starts the process of grounding the negative power cable 23. The process for grounding the negative power cable 23 is the same as the process for grounding the positive power cable 22 (S100 to S104).

  Specifically, the measurement unit 70 turns off the relay 50 so that the internal resistance of the relay 21 does not affect the resistance value of the ground insulation resistance 40 or the like (S107). Then, the measuring unit 70 connects the switch 51 to the negative power cable 23, grounds the power cable 23 via the resistor 52, and starts measuring the voltages Vp and Vn (S108).

  Then, the measurement unit 70 determines whether or not the changes in the voltages Vp and Vn are sufficiently small and the voltages Vp and Vn are stabilized (S109).

  When determining that the voltages Vp and Vn are stable (S109: YES), the measurement unit 70 determines that the time constant τ2 at which the voltage Vn decreases from the voltage Vn0 to the voltage Vn0 × 1 / e (e≈2.71) is determined. The voltages Vp and Vn are stored in the storage device 61 (S110). Note that the voltages when the negative power cable 23 is grounded and the voltages Vp and Vn are stabilized are Vp2 and Vn2, respectively. Thereafter, the measurement unit 70 operates the switch 51 to release the ground fault of the power cable 23 (S111), and turns on the relay 50 so that the relay 21 can detect a ground fault (S112).

Then, the measuring unit 70 calculates the resistance values Rp and Rn of the ground insulation resistors 40 and 42 from the voltages Vp1, Vp2, Vn1, and Vn2 stored in the storage device 61 (S113). Specifically, in FIG. 6, for example, when the voltages Vp and Vn are stable, the parallel resistance of the ground insulation resistance 40 and the resistance 52 and the current flowing through the ground insulation resistance 42 are the same. Therefore, the following formula (1) is established between the voltages Vp1 and Vn1.
Vp1 = ((R1 // Rp) / Rn) × Vn1 (1)
Similarly, the following equation (2) is established between the voltages Vp2 and Vn2.
Vp2 = ((R1 // Rn) / Rp) × Vn2 (2)
Here, since the resistance value R1 and the voltages Vp1, Vp2, Vn1, and Vn2 are known, the resistance values Rp and Rn are calculated from the equations (1) and (2).

  The measuring unit 70 calculates the capacitance values Cp and Cn of the ground insulating capacitors 41 and 43 from the resistance value R1, the calculated resistance values Rp and Rn, and the time constants τ1 and τ2 described above (S114). In the present embodiment, the measurement unit 70 stores the calculated resistance value Rp and the like in the storage device 61 as measurement values.

  Then, the measurement unit 70 causes the sensor 60 to measure the temperature and humidity around the DC power supply device 10 (S115). The measurement unit 70 acquires information on the resistance value Rp and the like by executing such processing.

== Processing of Control Device 62 ==
Here, the process in which the control device 62 determines the quality of the insulation state of the DC power supply device 10 using the measurement results of the ground insulation resistance 40 and the like, initial data, and the like will be described with reference to FIG. In the present embodiment, the process shown in FIG. 8 is executed at predetermined intervals.

  First, the measurement unit 70 measures resistance values Rp, Rn and capacitance values Cp, Cn, and causes the sensor 60 to measure the temperature and humidity around the DC power supply device 10 (S200). Note that the process S200 corresponds to the processes S100 to S115 shown in FIGS. Then, the measurement unit 70 stores the measurement result in the storage device 61 (S201).

  Further, the determination unit 71 determines whether or not the capacitance values Cp and Cn are larger than a predetermined value (S202). When the determination unit 71 determines that the capacitance values Cp and Cn are larger than the predetermined values (S202: YES), the caution display unit 76 displays a caution display indicating that the ground capacitances 41 and 43 are deteriorated. (S203). On the other hand, if the determination unit 71 determines that the capacitance values Cp and Cn are smaller than the predetermined values (S202: NO) or if a caution display is displayed in step S203, the determination unit 72 indicates that the resistance values Rp and Rn are predetermined. It is determined whether or not the value is larger (S204). When the determination unit 72 determines that the resistance values Rp and Rn are smaller than the predetermined values (S204: NO), the caution display unit 76 displays a caution display that the ground insulation resistances 40 and 42 are deteriorated. 63 is displayed (S206). On the other hand, when the determination unit 72 determines that the resistance values Rp and Rn are larger than the predetermined value (S204: YES), the determination unit 73 determines whether or not the decrease rate of the resistance values Rp and Rn is larger than the predetermined value. (S205). When it is determined that the rate of decrease is greater than the predetermined value (S205: YES), the caution display unit 76 causes the display device 63 to display a caution display indicating that the ground insulation resistances 40 and 42 have deteriorated ( S206). On the other hand, if it is determined that the decrease rate is smaller than the predetermined value (S205: NO), or if a caution display is displayed in the process S206, the warning output unit 77 continues the caution display for a predetermined period on the display device 63. It is determined whether it is displayed (S207). Then, the warning output unit 77 determines that the insulation state of the DC power supply device 10 has deteriorated and outputs a warning when the caution display is continuously displayed on the display device 63 (S207: YES). (S208). The warning is displayed, for example, on a monitor of a control station in the power system. If the caution display is not continuously displayed on the display device 63 for a predetermined period (S207: NO), the determination unit 75 determines whether or not the temporal changes in the resistance values Rp and Rn are greater than the predetermined. It is determined (S209). And if the determination part 75 determines with the time-dependent change of resistance value Rp and Rn being larger than predetermined (S209: YES), the alarm output part 77 will determine with the insulation state of the DC power supply device 10 getting worse. Then, an alarm is output (S208). On the other hand, when the determination unit 75 determines that the temporal changes in the resistance values Rp and Rn are smaller than a predetermined value (S209: NO), the process S200 is performed again after a predetermined period.

  The resistance value determination device 30 according to the present embodiment has been described above. In the determination unit 75, whether or not the change with time of the ground insulation resistances 40 and 41 is larger than a predetermined value depends on the difference between the initial resistance values Rp0 and Rn0 corresponding to the measured humidity and the resistance values Rp and Rn. Based on the determination. Thus, even if the resistance values Rp and Rn change due to the influence of humidity, is the change over time of the resistance value in which the influence of the humidity in the ground insulation resistances 40 and 42 is suppressed larger than a predetermined value? Therefore, it is possible to accurately determine whether the insulation state of the DC power supply device 10 is good or not.

  Moreover, in this embodiment, the quality of the insulation state of the DC power supply device 10 is automatically determined every predetermined period (for example, FIG. 8). For this reason, for example, since it is not necessary for the user to directly control the resistance value determination device 30 to execute the determination process, the load on the user is reduced.

  Moreover, the warning output part 77 will output the warning which shows that the insulation state of the DC power supply device 10 deteriorated, if the change with time of resistance value Rp, Rn became large. For this reason, the user can grasp | ascertain that the insulation state of the DC power supply circuit 10 deteriorated reliably.

  Further, for example, a power cable or the like may be added to the DC power supply device 10 later. In such a case, the determination unit 75 may not be able to accurately determine the quality of the insulation state of the DC power supply device 10 based on the initial data. However, the determination unit 72 determines that the insulation state has deteriorated when the measured resistance values Rp and Rn are smaller than a predetermined value. For this reason, the resistance value determination device 30 can accurately determine whether the insulation state of the DC power supply device 10 is good or not even when a power cable is added.

  Further, when the capacitance value Cp of the ground capacitance 41 or the like increases, the insulation state of the DC power supply device 10 may deteriorate. Since the determination unit 72 determines that the insulation state has deteriorated when the capacitance values Cp and Cn are larger than the predetermined values, the determination unit 72 can accurately determine whether the insulation state of the DC power supply device 10 is good.

  Further, the resistance value Rp of the ground insulation resistance 40 varies depending on the humidity. However, the alarm output unit 77 outputs an alarm when a situation where the resistance value Rp is smaller than a predetermined value continues for a predetermined period. Therefore, even when the resistance value Rp is decreased due to humidity, the resistance value determination device 30 does not immediately determine that the insulation state of the DC power supply device 10 has deteriorated, and therefore the possibility of erroneous determination can be reduced.

  The alarm output unit 77 outputs an alarm when a situation where the capacitance value Cp is larger than a predetermined value continues for a predetermined period. Therefore, even if the capacitance value Cp increases due to humidity, the resistance value determination device 30 does not immediately determine that the insulation state of the DC power supply device 10 has deteriorated, and therefore the possibility of erroneous determination can be reduced. .

  The above-described embodiment is intended to facilitate understanding of the present invention, and is not intended to limit the present invention. The present invention is changed and improved without departing from the gist thereof, and the present invention includes equivalents thereof.

  For example, the determination unit 72 determines whether or not the resistance values Rp and Rn are larger than a predetermined value (for example, 100 kΩ) in the process S204, but the determination unit 72 further determines that the resistance values Rp and Rn are other predetermined values. It may be determined whether or not (for example, 1 MΩ). If it is determined that the resistances Rp and Rn are greater than, for example, 1 MΩ, the process S207 in FIG. 8 may not be performed, and the process S207 may be performed directly. That is, when the measured resistance values Rp and Rn are sufficiently large, the process S207 may be executed without calculating the decrease rate of the resistance value. That is, when the resistance value Rp or the like is sufficiently high, the process S205 can be omitted, and the load on the control device 62 can be reduced.

  In addition, initial data for each of a plurality of temperatures may be acquired and stored in the storage device 61 in advance. In this case, for example, by causing the measurement unit 70 to select optimal initial data based on the temperature information, the influence of the temperature from the resistance value Rp and the like can be suppressed.

10 DC power supply device 20 Storage battery 21 Relay 22, 23 Power cable
DESCRIPTION OF SYMBOLS 30 Resistance value determination apparatus 40,42 Ground insulation resistance 41,43 Ground electrostatic capacitance 50 Relay 51 Switch 52 Resistance 60 Sensor 61 Memory | storage device 62 Control apparatus 63 Display apparatus 70 Measurement part 71 Acquisition part 72-75 Judgment part 76 Caution display part 77 Warning output section

Claims (6)

A storage unit that stores in advance data indicating the relationship between the resistance value of the ground insulation resistance of the DC circuit and the humidity around the DC circuit;
For each predetermined period, a measurement unit that measures the resistance value of the ground insulation resistance and the humidity around the DC circuit;
Obtaining the resistance value of the ground insulation resistance corresponding to the measured humidity based on the humidity measured by the measurement unit and the data each time the measurement unit measures the humidity around the DC circuit And
That the resistance value measured by the measurement unit is smaller than a predetermined value, or that the ground insulation resistance performed when the rate of decrease of the resistance value measured by the measurement unit is larger than a predetermined value is deteriorated When the caution display is not continued for a predetermined period , based on the resistance value acquired by the acquisition unit and the resistance value measured by the measurement unit, from the resistance value acquired by the acquisition unit in the ground insulation resistance It is repeatedly determined whether or not the change width up to the resistance value measured by the measurement unit is larger than a predetermined value. If the change width is larger than the predetermined value, an alarm is output to the effect that the insulation state of the DC circuit is deteriorated. a determination unit that Ru is,
A resistance value determination device comprising: The resistance value determination device according to claim 1 ,
When the determination unit determines that the change width from the resistance value acquired by the acquisition unit in the ground insulation resistance to the resistance value measured by the measurement unit is larger than a predetermined value, an alarm output unit that outputs an alarm is provided. To provide further,
A resistance value determination device characterized by the above. The resistance value determination device according to claim 2 ,
A resistance value determination unit that repeatedly determines whether or not the resistance value measured at each predetermined period is larger than a predetermined value;
A resistance value determination device characterized by the above. The resistance value determination device according to claim 2 or 3 , wherein
The measuring unit is
Measure the capacitance value of the ground capacitance of the DC circuit at each predetermined period ,
A capacitance value determination unit that repeatedly determines whether or not the capacitance value measured at each predetermined period is larger than a predetermined value;
A resistance value determination device characterized by the above. The resistance value determination device according to claim 4 ,
The alarm output unit
When a predetermined time period the resistance-format tough period is determined continuously that the measured resistance value is smaller than the predetermined value, it outputs the alarm,
A resistance value determination device characterized by the above. The resistance value determination device according to claim 4 or 5 ,
The alarm output unit
When a predetermined period time determines said capacitance value-format tough that measured capacitance value is greater than the predetermined value in succession to output the alarm,
A resistance value determination device characterized by the above.

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