HK1018524A - Modular core, self-powered powerline sensor - Google Patents

Description

Molded core self-powered powerline sensor

The present invention relates to a modular core, self-powered powerline sensor and, more particularly, to such a sensor that is capable of efficiently extracting power from a powerline having a very low level of line current.

This application is a continuation-in-part application of U.S. application serial No. 08/604,357 filed on 21/2/1996, while that application is a continuation of U.S. application serial No. 08/232,702 filed on 25/4/1994 (which was abandoned).

Ac power line monitoring for both overhead and underground applications, as well as primary and secondary applications, is useful for power companies to anticipate power outages due to equipment failures and overload on ac power lines, as well as power outages that may cause power loss to a large number of customers. The likelihood of powering down and losing the largest number of users increases during peak load when power usage is at a maximum and continuous power transmission is most critical. The restoration of outages caused by lines, transformers and other equipment is expensive, presents a hazard to utility employees, and can be costly to the utility in terms of lost power, lost revenue, and reputation damage. If the power line is an underground line, the effects of an unexpected power outage caused by a power line fault or overload are more severe. Due to the fact that most of the work required takes place in the ground, which is limited, sometimes damp, and never reaches ideal conditions, replacing a damaged underground line requires more people and enhanced safety measures. As a result, repairing such damaged underground lines is even more expensive, time consuming and dangerous.

Therefore, in order to better anticipate the potential for an unexpected power outage due to equipment failure and overload, ac power line sensors that sense electrical conditions such as power, voltage and current are very useful for utility companies to monitor ac power lines and associated equipment such as transformers and switches. If power companies are able to monitor conditions on the power line, they are better able to service and replace power lines that may become blacked out due to overload or failure, thereby reducing the number of unexpected power outages. By replacing and servicing such equipment, the utility company can greatly reduce the outage time for the customer. The costs associated with repairing or replacing damaged cables will also be reduced. Because of the overtime payments involved, the cost of replacing or repairing a damaged cable is much greater than if the repair or replacement were normally planned.

However, conventionally available power line sensors typically require invasive electrical connections to the monitored circuitry. Such installations are expensive for the utility company, may present a hazard to the installer, and may cause a power outage to the customer. Due to these limitations, power line sensors have not found widespread use in the power industry.

A sensor that addresses the deficiencies of the prior art systems is described in U.S. application No. 08/232,702, filed 25/4/1994 and assigned to the assignee of the present invention. The sensor utilizes a thin, relatively wide core of high permeability ferromagnetic material that is wrapped in a completely non-invasive manner around a layer of insulating rubber of an alternating current power line. A plurality of windings are wound around the core layer such that they are substantially parallel to the direction of the alternating current power line. The ac in the power line is used to induce a current in the windings to power the sensor and controller, and to sense the current in the ac power line and to measure a non-reference voltage level. The sensor is very thin in cross section and can therefore be easily mounted in confined volumes and on very closely spaced lines. Furthermore, it operates without invasive contact with the power line, and is therefore safe, easy and quick to install. However, this sensor does have drawbacks.

First, it does not efficiently extract power from the ac power line. For most efficient power extraction, the core should be annular, with a thickness in the core cross-section approximately equal to its width. However, to maintain a low profile, the sensor has a core section with a width much greater than the thickness. This results in a sensor that does not efficiently draw power from the power line and therefore is unable to draw enough power to operate on a power line with a small line current. To extract more power, the width of the core layer must be increased, but at the same time to maximize efficiency, the cross-sectional thickness must be increased commensurately. In order to achieve the desired power requirements, the thickness of the core cross-section must be increased to a point where it no longer retains its low profile and can therefore no longer be installed in confined volumes and dense lines.

In addition, the core width of the sensor is somewhat inflexible and difficult to mount on power line sections having substantial bends.

It is therefore an object of the present invention to provide a modular core, self-powered powerline sensor that senses conditions in or around an a.c. powerline in a completely non-intrusive manner.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor which effectively maximizes power extraction from an a.c. powerline while maintaining a low profile construction.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor that is capable of extracting power from a powerline with minimal line current.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor that is very flexible.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor that is powered in a completely non-intrusive manner by low power drawn directly from the a.c. powerline.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor that is capable of transmitting sensed conditions in and around an a.c. powerline through the powerline itself.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor that is capable of transmitting and receiving communications over a powerline ac line to and from a remote base station in a completely non-intrusive manner.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor which is quick, easy and safe to install without interrupting or interfering with the power supply to the user.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor that can be mounted on different size powerlines.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor that can be mounted on closely spaced cables within a confined volume.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor which is thin, compact in size and lightweight.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor that is mechanically supported by an ac powerline.

It is a further object of this invention to provide such a modular core, self-powered powerline sensor that is inexpensive and free to use.

The present invention results from the realization that a very thin profile, self-powered power line sensor that can operate efficiently even by drawing sufficient power from an ac power line having very little line current can be achieved by providing a core comprising a plurality of thin profile molded core elements arranged around the ac power line, each molded core element having a plurality of windings for drawing power from the ac power line, wherein the windings of each molded core element are interconnected to provide a sensing means for sensing a condition in or around the ac power line, and a controller means powered by the windings and sensitive to the sensing means for receiving a signal indicative of the sensed condition.

The invention features a modular core, self-powered powerline sensor. The current extraction means of the sensor comprises a plurality of moulded core elements arranged around the ac power line. There is a winding layer energized by alternating current power wire that includes a plurality of windings arranged around each molded core element. The windings of each molded core element are interconnected. Voltage and current sensors and other devices that sense conditions in or around the ac power line are powered by the windings when they require power. A controller, also powered by the winding, is sensitive to the sensing device and receives (and transmits) signals indicative of the sensed condition.

In a preferred embodiment, the molded core elements of the current extraction device are preferably annular, low profile, and they may be formed of high permeability ferromagnetic material. The width of the molded core elements may be approximately equal to their cross-sectional thickness. The molded core element may include gaps therein that can be pushed apart to enable the powerline sensor to be installed on and removed from the a.c. powerline. The windings of each molded core element may be electrically interconnected in series or in parallel, and the windings may be energized using a non-contact transformer action with the ac power line.

The voltage sensor includes a capacitor for capacitively sensing a voltage on the ac power line, the capacitor including first and second diaphragms disposed proximate the ac power line and a dielectric disposed between the plates. The dielectric may be air. The first and second partitions may be arranged coaxially around the ac power line. The current sensor is an inductor that includes a plurality of windings disposed about the first and second spacers, and a separator material. Other sensors may be used to sense a number of other conditions in or around the ac power line.

The controller means may comprise means for transmitting a signal indicative of the sensed condition over the ac power line. The transmitting means may transmit a signal to a distant base station. The transmitting means may comprise a communications core element arranged around the ac power line and a plurality of windings arranged around the communications core element to couple the signal to the ac power line by contactless transformer action. The controller device may include means for transmitting a signal indicative of the sensed condition over the ac power line, and the transmitting means may be interconnected with the capacitor to capacitively couple the signal to the ac power line. The controller means may comprise means for receiving communications from a remote base station and the receiving means may be interconnected with a capacitor for capacitively coupling communications from the ac power line. The controller means may comprise means for receiving communications from a remote base station sent over the ac power line. The receiving means may comprise a communications core element arranged around the ac power line and a plurality of windings arranged around the communications core element to couple communications from the remote base station over the ac power line. The controller device may include means for transmitting a signal indicative of the sensed condition over the ac power line, and means for receiving communications transmitted from the remote base station, wherein the transmitting means and the receiving means are interconnected with a capacitor to capacitively couple the signal transmitted by the controller device to the ac power line, and to capacitively couple the signal transmitted by the remote base station from the ac power line. The controller means may further comprise means for receiving communications from a remote base station and the plurality of windings on the communications core element may be coupled for communication from the ac power line by a contactless transformer action. The controller means may include means for statistically calculating received signals indicative of sensed conditions over a predetermined period of time to establish a nominal condition level, and means for detecting a change from said nominal level. The sensed condition may be a voltage. The statistical calculation means may comprise means for averaging the received signals over a predetermined time period.

Other objects, features and advantages will occur to those skilled in the art from the following description of a preferred embodiment and the accompanying drawings, in which:

FIG. 1A is a three-dimensional view of a modular core, self-powered powerline sensor in accordance with the present invention;

FIG. 1B is a schematic drawing depicting the winding interconnections of the molded core element of FIG. 1;

FIG. 1C is a three-dimensional view of a sensing device of the modular core, self-powered powerline sensor of FIG. 1A;

fig. 2 shows the modular core, self-powered powerline sensor of fig. 1, wrapped around with a protective cover and having electronic components arranged between the protective cover and the sensor winding.

FIG. 3 is a schematic block diagram of both the sensor and base station of FIG. 1 coupled to an AC power line; and

fig. 4 is a flow chart of software that may be used by the microcontroller of fig. 3 to establish a time-based nominal level for a sensed condition in or around the ac power line to determine a change in or around the ac power line from the nominal condition.

Fig. 1A shows a modular core, self-powered powerline sensor 10 arranged around an ac powerline 12 in accordance with the present invention. The power line 12 includes a conductive strand (or single core) 14 and an insulating rubber layer 16. The illustrated ac power line 12 is a cable of the type typically used in underground secondary power distribution applications; however, this is not a necessary limitation of the present invention, as the sensor 10 can be used for overhead secondary voltage applications with insulated or non-insulated cables, as well as overhead and underground primary voltage applications.

The sensor 10 comprises low profile moulded core elements 18,20 and 22 arranged around the power line 12 by pushing open gaps 19,21 and 23 therein to mount the core elements on the power line 12 and then resiliently returning the gaps to their original positions to secure the core elements in position. The core element is formed of a high permeability ferromagnetic material, such as steel, and is typically encased in an insulating material.

The core elements 18,20 and 22 are annular in shape and have a cross-sectional thickness T approximately equal to their width W, typically approximately 1/2 inches. Thus, as previously described, they are approximately configured to most efficiently extract power from the ac power line 12. As also previously described, for a single core system, in order to improve the amount of power extraction from the ac power line, the width of the core must be increased and its cross-sectional thickness must be increased commensurately to maintain efficiency. However, increasing the cross-sectional thickness to maintain efficiency makes the cross-section of the sensor very thick and prohibits its use in confined volumes and on closely spaced lines. According to the invention, the core consists of several, in this case three, moulded core elements. This maintains efficiency by having the core elements have a cross-sectional thickness approximately equal to their width, and by using several core elements, the cross-sectional thickness of the sensor can be limited to maintain a low profile while allowing increased power extraction.

The size of the core elements 18,20 and 22 that optimizes power extraction is a combination that minimizes losses while maximizing coupling between the multiple windings on the core (secondary windings) and the power line cable passing through the center of the core (primary windings).

The three fundamental losses observed in practice are those caused by the resistance of the secondary winding, those caused by the induction of leakage flux, and those caused by the induction of eddy currents in the core material. Other losses are present and they may affect performance to a greater or lesser extent depending on design details. However, the three losses mentioned above are the major losses observed.

In a test embodiment of the sensor, the core comprises a design made of tape wound magnetic steel material. By tape winding is meant that the core is made by spirally winding a continuous strip of steel to form a loop much like a coil of co-tape. The advantage of this manufacturing method is that it is relatively easy and inexpensive, and it allows the use of magnetic steel that is preferentially oriented so that the maximum permeability is in line with the length of the steel strip. When the steel strip so oriented is wound in a toroid, the maximum permeability is approximately arranged in a loop along the toroidal core. Thus, the maximum permeability path is in line with the path of the magnetic flux created by the flow of current in the primary conductor through the toroidal core. If the tape wound core is made of a magnetic material coated with an electrically insulating layer, the material will form a core structure that effectively restricts eddy current flow in the path directed radially outward from the center of the primary winding through the core. However, such a configuration does not tend to restrict eddy currents flowing in paths in the core parallel to the primary winding, and eddy currents induced in the core by the primary winding current will tend to follow these parallel paths. Irrespective of other issues, if a toroidal core can be electrically divided into a plurality of side-by-side cores to provide an open circuit in the core eddy current path parallel to the primary winding, these eddy currents will be significantly reduced with their associated losses (reactive power).

The cross section of the core can be optimized to minimize losses and maximize coupling between the primary and secondary windings. The typical core has an inner diameter R₁Outer diameter R₂And a width W. Core cross-sectional thickness T of R₁And R₂The difference between, namely:

T=R₂-R₁ (1)

the coupling between the primary and secondary windings may be characterized by the number of flux turns in the core. The secondary winding resistance and leakage inductance may be characterized by the length of each secondary band on the core or the length of the perimeter of the core cross-section (2T + 2W). The core size can be optimized by maximizing the number of flux turns and minimizing the core cross-sectional perimeter. For the expected size range of the sensor, the optimal core size requires a ratio of W to T (W/T) in the approximate range of 1 to 3. As noted, the experimental embodiment of the sensor utilizes three cores 18,20 and 22, each having a W/T ratio of approximately 1.

By winding a wire, such as 28 gauge magnetic wire, in a number of turns around each core element 18,20 and 22 and interconnecting the windings of each core element in series as shown in fig. 1B, a winding layer is formed comprising windings 24,26 and 28. Alternatively, the windings may be connected in parallel. The ac power in the power line 12 induces currents in the windings 24,26 and 28 by the contactless transformer action. The appropriate winding ratio is selected so that when the ac power line 12 is energized, the desired current will be induced in the windings. The number of winding turns determines the ratio between the current induced in the winding and the current in the alternating power line 12 to the extent that the core elements 18,20 and 22 contain an induced magnetic flux density equal to or less than their saturation level. For line currents as small as 20 amps, a typical number of windings for each core element is 75 in order to extract enough power to operate the sensor 10. By increasing the number of core elements or windings, or both, the sensor 10 can be made to extract more power and thus be able to operate at even smaller ac currents.

The sensor 10 also includes the voltage and current sensing device 36 of fig. 1A and 1C. The voltage is sensed by a capacitor 37 having a first inner surface conductor 38 adjacent the insulating layer 16 of the ac power line 12 and an outer surface conductor 40 spaced from the inner conductor 38. The two conductors are arranged coaxially around the ac power line 12 and contain a dielectric 42, such as air or a foam core, between them. The capacitor 37 is used to sense the voltage capacitively coupled from the ac power line 12, which is proportional to the voltage of the power line 12, and as described below, serves as a receiver to capacitively couple high frequency power line communications from the power line 12. Because capacitor 37 is arranged coaxially around power line 12, it tends to counteract the effects of power in multiple power lines that may be near power line 12, rather than in power line 12.

To further reduce noise and/or unwanted effects of external magnetic fields, such as those generated by adjacent power lines or other sources of electromagnetic fields, the inner surface conductor 38 is electrically connected to additional coaxial plates 39 and 41, the plates 39 and 41 being spaced externally of the plate 38 in the same manner as the plate 40 and with the same dielectric between the plates 39 and 38 and the plates 38 and 41. The additional plates 39 and 41 each have approximately half the surface area of the outer coaxial plate 40 and are electrically connected to the inner coaxial plate 38 as shown. Thus, any external signal will tend to be picked up equally by both the inner and outer coaxial plates 38, 40 and no differential measurement is exhibited between the inner and outer surface conductors 38, 40. There may be only one coaxial plate, such as plate 39, which has the same surface area as outer plate 40. Alternatively, there may be three coaxial plates, each having one third of the surface area of the outer plate 40. Generally, if there are n plates, the surface area of each plate is 1/n of the surface area of outer plate 40.

Around the capacitor 37 is arranged an inductor 43 with a number of current measuring windings 44 wound around a ring-shaped separation material (e.g. foam) 45. The current of the ac power line 12 induces a current in the winding 44 that is proportional to the current flowing in the ac power line 12. Because the inductor 43 is wrapped around a separate material 45 containing air or foam, it does not become saturated as with a typical iron core. The sense current is therefore more linearized, making it more accurate and easier to interpret.

The separating material 45 contributes to the shape of the winding 44 and its material has a low permeability like air. The separation material 45 may have a higher magnetic permeability, but care must be taken to include a gap or control the magnetic permeability so that the material of the shape 45 does not become magnetically saturated and the current sensed by the inductor 43 becomes less linear and harder to interpret. The non-linearised current measurement can be sensed and accurately interpreted by the inductor 43, however this requires a somewhat greater complexity for the other components of the sensor.

The voltage and current sensing device 36 also includes a gap 46 formed therein to allow the sensing device to be installed on the ac power line 12 or removed from the ac power line 12. Although the voltage sensor device (capacitor 37) and the current sensor device (inductor 43) of the voltage and current sensing device 36 are shown as being arranged at the same location around the power line 12, this is not a necessary limitation of the present invention. They may be arranged close to each other or even spaced apart from each other.

The communication device 48 is comprised of a communication core element 50 and a plurality of windings 52 wound around the core element 50 to transmit communications from the sensor 10 noninvasively to the ac power line 12 by contactless transformer action. Preferably, the communication device 48 functions as a high frequency communication transmitter and the capacitor 37 of the sensor 36 functions as a high frequency communication receiver in addition to a voltage sensor. However, any one may be used to transmit or receive or both. Thus, non-invasive coupling for signal communication with a power line in accordance with the present invention can be described as reactive coupling to encompass both capacitive and inductive coupling techniques.

The sensor 10 typically includes a protective cover 62 that provides electrical insulation, as shown in FIG. 2. The cover 62 is typically formed of rubber and is secured to the windings with self-curing tape, adhesive, or other suitable means. Straps 63 and 64 removably secure power line sensor 10 in place about alternating current power line 12. The overlay 62 performs the additional function of effectively sandwiching the electronic components 66 mounted on the flexible printed circuit board 68 between it and the winding surface. The electrical connection between the winding (fig. 1B) and the electronic component is made by an electrical connection that is not visible in the figure but is schematically represented in fig. 3. The electronic components 66 include various types of sensors to sense virtually any phenomenon, such as temperature, pressure, radiation, humidity, etc.; a power source supplied by windings 24,26 and 28 (fig. 1), windings 24,26 and 28 being energized by a non-contact transformer action with ac power line 12; a microcontroller; as well as various other elements, which are discussed in more detail below with reference to fig. 3.

Although all of the electronic components depicted in fig. 2 are shown as being fixed to the flexible circuit board 68, this is not necessary as the sensors may be arranged off the circuit board 68 and sandwiched between the protective cover 62 and the windings, or the sensors may even be positioned outside of the protective cover 62 to sense certain types of phenomena around the outside of the protective cover 62.

A modular core, self-powered powerline sensor 10 is schematically depicted in the system 100 of fig. 3. The power of modular core, self-powered powerline sensor 10 is derived from the a.c. powerline 12 using windings 24,26 and 28. the a.c. powerline 12 can be a single phase powerline, which can be either individual or part of a polyphase transmission or distribution system, with windings 24,26 and 28 being shown as single windings in this figure for clarity. These windings are connected to a power supply 102 by wires 103 and 104, the power supply 102 being arranged on the flexible circuit board 68. The power supply 102 may be an ac to dc regulator integrated circuit that provides 5 vdc to the microcontroller 106, and it also provides 12V and +5V outputs that may be used by one or more sensors or other electronic components.

The microcontroller 106 may be an 8-bit embedded controller with an analog-to-digital converter. The sensors 108 and 112 are shown as being interconnected with the microcontroller 106, however, a different number of sensors may be used. The sensors 108 to 110 are arranged on the flexible circuit board 68, while the sensors 111 and 112 are arranged outside the protective cover 62 of fig. 2. Only one sensor, sensor 112, is powered by power source 102 because the remaining sensors do not require an external power source to operate. These sensors provide an analog or digital signal to the microcontroller 106 indicative of the particular condition sensed in or around the ac power line 12. In addition to these sensors, a capacitor 37 operating as a voltage sensor and an inductor 43 operating as a current sensor are shown.

Capacitor 37 is interconnected by lines 114 and 115 with signal conditioner 116, and signal conditioner 116 performs amplification and filtering of the sensed signal to match the input requirements of microcontroller 106. The signal of the voltage sensor 37 is a capacitively coupled voltage representing the instantaneous voltage on the ac power line 12. Because there is no reference voltage, the voltage sensor 37 does not provide an absolute voltage reading to the microcontroller 106. However, by monitoring the instantaneous voltage level provided by capacitor 37 over a period of time, an average or nominal voltage level can be determined, and after the nominal level is established, the change from the nominal voltage level can be resolved by the instantaneous input provided by capacitor 37. The microcontroller 106 may perform other statistical calculations, such as weighting, on the non-reference voltage input signals and may determine the deviation from these other types of statistical determinations.

Current sensing is performed by an inductor 43, and the inductor 43 induces a current that is proportional to the ac line current in the power line 12. The sensed current is then provided to a current pickup signal conditioner 117, which amplifies and filters the signal before it is provided to the microcontroller 106.

Sensors 108 and 110 are disposed on flexible circuit board 68 and sensors 111 and 112 are disposed on the exterior of protective cover 62. These sensors may sense, for example, temperature, pressure, gas, humidity, radiation or light (visible or infrared). In fact, sensors that actually sense any phenomenon may be utilized. Some sensors, such as temperature sensors or radiation sensors, may be mounted directly on the flexible circuit board 68, while other sensors, such as sensors 111 and 112, operate only under the exterior arranged in the protective cover 62, such sensors sensing gases and light, for example.

The sensors 108 and 112 and the voltage and current sensors 36 continuously sense various conditions in or around the ac power line 12 and provide analog or digital signals representative of these sensed conditions to the microcontroller 106. If necessary, the controller 106 converts the signals provided by the sensors into digital signals, and the controller 106 then generates communication data representative of the sensed conditions, and this data is provided over line 118 to power line carrier electronics 120, which encodes the data. The power line carrier electronics 120 then provides the encoded data to the output exciter 112, which sends low voltage, high current pulses to the windings 52 of the communication device 48 to non-invasively couple the transmissions of the microcontroller 106 of the sensor 10 to the ac power line 12 via a contactless transformer action. To locally sense the condition of the power line, a storage device 129 may be connected on lines 118 and 119. The storage device 129 is arranged at some convenient location near the power line.

Alternatively, as shown in dashed lines, the output of driver 122 may be provided to inner surface conductor 38 and outer surface conductor 40 of capacitor 37 of fig. 1 via lines 124 and 125, respectively. In this arrangement, the signal sent from the microcontroller 106 is capacitively coupled to the ac power line 12, and the exciter 122 must be configured to provide a high voltage, low current output pulse. It is presently preferred that the exciter 122 be configured to excite the windings 52 of the communication device 48. Driver 122 may be a high voltage amplifier (inverting or non-inverting).

The data transmitted by the microcontroller 106 includes an identification code identifying the power line sensor 10 and an identification code indicating the type of data transmitted to each individual specific sensor (108, 112, 37, and 43) on the power line 10. That is, the transmission includes information about the source of the transmission (many power line sensors may be used at various locations in the power distribution system of the utility company), as well as information about the type of data being transmitted, i.e., whether it is data about voltage, current, temperature, radiation, etc. The transmissions and identification codes and data of interest may occur on a regular basis, by time when a particular threshold is sensed, or by any desired criteria. The communication code may conform to a selected formal communication system specification or protocol. The protocol may be based on the OSI (open systems interconnection) reference model for communication proposed by ISO (international organization for standardization) Geneva, Switzerland. Any other communication code suitable for power line communication may be utilized.

The data transmitted by the sensor 10 is received by the remote base station 126. The base station 126 is interconnected with the power line 12 with direct electrical connections 127 and 128 connected to the power line 12 ', the power line 12 ' being part of a power distribution or transmission system power line and typically being either a ground line, a neutral line, or a power line that is out of phase with the power line 12 ' (in a polyphase system). However, the connection to the power line may be accomplished with a non-contact transformer action or capacitive coupling, as described above with respect to sensor 10. For example, inductor 43 'may be used to provide a connection to the power line through non-invasive inductive coupling and/or capacitor 37' may be used to provide non-invasive capacitive coupling. The transmitted data is provided to a computer 132 via a standard power line carrier modem 130 that matches the communication analog to digital of the sensor 10. The base station 126 is also capable of transmitting data from a computer 132 to the ac power line 12 via a power line carrier modem 130. Thus, for example, the base station 126 may query the molded core self-powered power line sensor 10 and any other power line sensors on the system for sensor information on demand, rather than passively waiting for the power line sensor to transmit. In addition, the power line sensors may be reprogrammed from the base station 126.

The coded communications transmitted by the remote base station 126 are preferably received by the capacitor 37 from the ac power line 12 with capacitive coupling. These high frequency communication signals are provided to high pass filters 134 and 136, pass them therethrough, and are provided to power line carrier electronics 120. The power line carrier electronics 120 decodes the communication signals and sends them to the microcontroller 106 via line 119.

Alternatively, the winding 52 of the communication device 48 may be used to receive communications from a remote base station 126. This is achieved by providing leads 138 and 139 (drawn in dashed lines) interconnecting the winding 52 with the high pass filters 134 and 136.

It should be noted that while it is preferred to use non-intrusive powerline communication between the sensors 10 and the base station 126, this is not a necessary limitation of the present invention. Direct contact power line communication or non-power line communication may be utilized, such as radio frequency, telephone line modem, cable television, cellular telephone, infrared, fiber optic cable, microwave, or ultrasonic communication.

The microcontroller 106 performs analog-to-digital conversion of sensed conditions, performs calculations and updates to memory locations storing previously sensed conditions, performs numerical operations such as determining running time averages and the like, tracks time for synchronization, and controls communication between the modular core self-powered powerline sensor 10 and the base station 126.

The microcontroller 106 can provide the base station 126 with the actual instantaneous value of a particular sensed condition, such as an actual temperature or radiation reading. However, it can also provide an indication to the base station 126 that the particular condition being sensed has changed from a nominal level, and the amount of such change. As briefly mentioned above, voltage sensing requires such data transmission because no sensing voltage can be compared to determine a reference level for an absolute voltage. Thus, the sensed voltage is compared to a nominal level and the change in the sensed voltage from the nominal level is determined and transmitted to the base station 126. The nominal level may be an average voltage level, or other types of statistical calculations may be performed on the sensed voltage data, such as weighting, and may be compared to the nominal level to determine changes from the nominal level. Furthermore, while this process is not required to be performed for all types of sensors (as many sensors provide absolute values of the sensed condition), it may be used for any condition being sensed. In fact, it may be more useful to provide a change in the nominal level relative to the sensed condition than to provide an actual absolute sensed value. This is because in many instances the monitored conditions are not monitored as actual values, but rather as changes from some nominal value.

To detect and transmit changes in the nominal level relative to the sensed condition, the microcontroller 106 operates according to the flow chart 150 of FIG. 4. At step 152, the modular core, self-powered powerline sensor is installed and the condition or conditions (e.g., voltage, current, temperature, radiation, etc.) are continuously and instantaneously acquired at step 154. At step 156, the instantaneous value of the sensed condition over time t is averaged over time, or other type of statistical calculation, such as weighting, is performed to determine the nominal level of the condition on the ac power line. At this point, the initial calibration is complete to the extent that the desired type of statistically calculated nominal levels has been determined. The calibration process may be performed anywhere from a few seconds to weeks or even months to obtain an accurate nominal level reading. After the initial calibration process is complete, the instantaneous value obtained in step 154 is compared to a nominal level in step 158. After the initial nominal level is determined, it is continuously recalculated from the new instantaneous sensor data. At step 160 it is determined whether the instantaneous value has changed from the nominal level and if so, a signal is sent to the remote base station indicating the change and the extent of the change at step 162. Regardless of whether a change is detected, the system returns to step 154 to obtain another instantaneous value, and the process continues until the sensor is removed from the ac power line or determination of the particular condition being sensed is no longer required.

Although specific features of the invention are shown in some drawings and not in others, this is for convenience only as each feature may be combined with any or all of the other features in accordance with the invention.

Other embodiments will occur to those skilled in the art and are within the following claims.

Claims (49)

1. A modular core, self-powered powerline sensor comprising:

a plurality of molded core elements arranged around an AC power line;

a winding layer, energized by an alternating current power line, comprising a plurality of windings arranged around each of said molded core elements, wherein the windings of each of said molded core elements are interconnected;

means for sensing a condition in or around the ac power line; and

controller means powered by said winding and sensitive to said sensing means to receive a signal indicative of a sensed condition.

2. The modular core, self-powered powerline sensor of claim 1 in which said modular core element is in the form of a toroid.

3. The modular core, self-powered powerline sensor of claim 1 in which said modular core element is low profile.

4. The modular core, self-powered powerline sensor of claim 1 in which said modular core elements are formed of a high permeability ferromagnetic material.

5. The modular core, self-powered powerline sensor of claim 1 in which each of said modular core elements has a width approximately equal to its cross-sectional thickness.

6. The modular core, self-powered powerline sensor of claim 1 in which said modular core elements include a gap therein which can be pushed open to allow the powerline sensor to be installed on or removed from the a.c. powerline.

7. The modular core, self-powered powerline sensor of claim 1 in which the windings of each of said modular core elements are electrically interconnected in series or in parallel.

8. The modular core, self-powered powerline sensor of claim 1 in which said plurality of windings are energized by a non-contact transformer action with the a.c. powerline.

9. The modular core, self-powered powerline sensor of claim 1 in which said means for sensing a condition includes means for sensing the voltage on the a.c. powerline.

10. The modular core, self-powered powerline sensor of claim 9 in which said means for sensing the voltage includes a capacitor for capacitively sensing the voltage on the a.c. powerline including inner and outer spacers disposed adjacent said a.c. powerline and a dielectric disposed between said spacers.

11. The modular core, self-powered powerline sensor of claim 10 in which said dielectric is air.

12. The modular core, self-powered powerline sensor of claim 10 in which said first and second diaphragms are coaxially disposed about said a.c. powerline.

13. The modular core, self-powered powerline sensor of claim 10 further including n additional plates electrically connected to said inner coaxial plate for reducing noise.

14. The modular core, self-powered powerline sensor of claim 13 in which each of said n additional plates has a surface area which is approximately 1/n the surface area of said outer plate.

15. The modular core, self-powered powerline sensor of claim 1 in which said means for sensing includes means for sensing the current of the a.c. powerline.

16. The sensor of claim 15, wherein said sensing means comprises an inductor.

17. The sensor of claim 16, wherein the inductor comprises a plurality of current measurement windings wound around a separation material, the separation material being disposed around the power line.

18. The sensor of claim 17, wherein said separation material has a low magnetic permeability.

19. The sensor of claim 17, wherein the separation material is a foam.

20. The sensor of claim 17, wherein the separation material is annular.

21. The modular core, self-powered powerline sensor of claim 1 in which said means for sensing a condition includes means for sensing a plurality of conditions in or around the a.c. powerline.

22. The modular core, self-powered powerline sensor of claim 1 in which said controller means includes means for transmitting said signal indicative of the sensed condition over the a.c. powerline.

23. The modular core, self-powered powerline sensor of claim 22 in which said means for transmitting transmits said signal to a remote base station.

24. The sensor of claim 23, wherein said transmitting means transmits said signal to a storage device disposed proximate the power line.

25. The modular core, self-powered powerline sensor of claim 22 in which said means for transmitting includes a communications core element disposed about the a.c. powerline and a plurality of windings disposed about said communications core element for coupling said signal to the a.c. powerline through a non-contact transformer action.

26. The modular core, self-powered powerline sensor of claim 10 in which said controller means includes means for transmitting said signal indicative of the sensed condition over the a.c. powerline and said means for transmitting is interconnected with said capacitor for capacitively coupling said signal to the a.c. powerline.

27. The modular core, self-powered powerline sensor of claim 10 in which said controller means includes means for receiving communications from a remote base station and said receiving means is interconnected with said capacitor for capacitively coupling communications from the powerline.

28. The modular core, self-powered powerline sensor of claim 1 in which said controller means includes means for receiving communications from a remote base station transmitted over the a.c. powerline.

29. The modular core, self-powered powerline sensor of claim 28 in which said means for receiving includes a communications core element disposed about the a.c. powerline and a plurality of windings disposed about said communications core element for coupling communications from said a.c. powerline from said remote base station.

30. The modular core, self-powered powerline sensor of claim 10 in which said controller means includes means for transmitting said signal indicative of the sensed condition over the a.c. powerline and means for receiving communications transmitted from a remote base station, wherein said means for transmitting and means for receiving are interconnected with said capacitor for capacitively coupling signals transmitted by said controller means to the a.c. powerline and for capacitively coupling signals transmitted by said remote base station from the a.c. powerline.

31. The modular core, self-powered powerline sensor of claim 25 in which said controller means further includes means for receiving communications from a remote base station and said plurality of windings on said communications core element couple said communications from the a.c. powerline through a non-contact transformer action.

32. The modular core, self-powered powerline sensor of claim 1 in which said controller means includes means for statistically calculating said received signal indicative of said sensed condition over a predetermined period of time to establish a nominal condition level and means for detecting changes from said nominal level.

33. The modular core, self-powered powerline sensor of claim 32 in which said sensed condition is voltage.

34. The modular core, self-powered powerline sensor of claim 32 in which said statistical calculation means includes means for averaging said signals received during said predetermined time period.

35. A modular core, self-powered powerline sensor system comprising:

a plurality of molded core elements arranged around an AC power line;

a winding layer, energized by an alternating current power line, comprising a plurality of windings arranged around each of said molded core elements, wherein the windings of each of said molded core elements are interconnected;

means for sensing a condition in or around the ac power line; and

controller means powered by said winding and sensitive to said sensing means to receive signals indicative of the sensed condition, to transmit said received signals to a remote base station over said ac power line, and to receive communications transmitted from said remote base station.

36. A sensing device for a power line, the sensing device comprising:

a voltage sensing capacitor including a pair of spaced inner and outer plates disposed about the power line and a dielectric disposed between said plates; and

an inductor for sensing current includes a separator material disposed about a power line and a plurality of windings wound about the separator material.

37. The sensing device of claim 36, wherein said capacitor further comprises n additional plates electrically connected to said inner plate, each of said plates having a surface area approximately equal to 1/n of the surface area of said outer plate to reduce noise.

38. The sensing device of claim 36, wherein the inner and outer plates are annular.

39. The sensing device of claim 36, wherein the separation material has a low magnetic permeability.

40. The sensing device of claim 39, wherein the separation material is a foam.

41. The sensing device of claim 39, wherein the separation material is annular.

42. The sensing device of claim 36, wherein the inductor is disposed on the capacitor.

43. The sensing device of claim 42, wherein said winding is wound around said capacitor.

44. A power extraction device, comprising:

a plurality of molded core elements arranged around an AC power line; and

a winding layer, energized by said alternating current power line, comprising a plurality of windings arranged around each of said molded core elements, wherein the windings of each molded core element are interconnected.

45. The power extraction device of claim 44, wherein the molded core element is annular.

46. The power extraction device of claim 44, wherein the molded core element is low profile.

47. The power extraction device of claim 44, wherein the molded core element is formed of a high permeability ferromagnetic material.

48. The power extraction device of claim 44, wherein each of the molded core elements has a width approximately equal to its cross-sectional thickness.

49. The power extraction device of claim 44, wherein the molded core element includes a gap therein that can be pushed open to allow the power line sensor to be installed on and removed from the AC power line.