Hot socket detection in electricity meters

Abstract

Techniques for hot socket detection are disclosed. In one example, a meter includes a current transformer having a secondary bifilar winding. The meter is proximate to a current coil. The secondary bifilar winding includes a first bifilar winding and a second bifilar winding. A start lead of the first bifilar winding is connected to a start lead of the second bifilar winding. The meter further includes a voltage source configured to generate a direct current (DC) voltage signal. The DC voltage signal is provided to a finish lead of the first bifilar winding. A first sense resistor is connected between the finish lead of the second bifilar winding and ground. A processing circuit receives a signal indicative of the voltage across the first sense resistor and determines a temperature associated with the current coil. The processing circuit is further configured to detect a hot socket condition based on the temperature.

Description

[Technical field]

[0001] The present invention relates generally to electricity meters, and more particularly to a system and method for detecting hot socketing in an electricity meter. [Background technology]

[0002] Electric meters measure energy or power consumption between a utility power line and a load. For example, electric meters for residential customers are often connected at the point where the home's electrical system connects to the utility wiring. Utility meters include one or more electrical contacts through which a significant amount of electrical current flows. For example, the meter may have blades that connect to the power line and the load to allow measurements of load current and load voltage from within the meter. The blades are received by jaws of a meter mounting device for the building.

[0003] When the meter is to be replaced or repaired, it is pulled from the mounting device, thus allowing the blade to be removed from the jaws. Although the blade and jaws are typically mechanically robust, they are still subject to wear and possibly corrosion. This occurs especially if the meter is removed or replaced multiple times. If the jaws are significantly worn or corroded, non-trivial resistance can develop at the interface between the jaws and the blade, which is undesirable.

[0004] When the connection between the jaws of the meter mounting device and the blade of the meter becomes unreliable due to increased resistance, arching, or other conditions, a "hot socket" condition can occur. When a hot socket condition exists, the temperature of the meter, and in particular the temperature of the blade, increases.

[0005] Additionally, the meter may have one or more switches that allow for disconnection of the electrical supply to the load. For example, many meters allow for remote control of the switch. Such switches, when closed, carry the full current of the load and must necessarily have substantial contacts. Such switches may deteriorate with some frequency of use. As the switch contacts deteriorate, the resistance of the switch contacts increases. Such resistance creates additional, undesirable power losses in the meter.

[0006] Since introducing resistance is undesirable, a method is needed to detect any degradation of such connections over time that may occur. Summary of the Invention

[0007] Certain aspects and features include techniques for detecting hot socketing. In one example, the meter includes a current transformer including a primary winding, a secondary winding, and a secondary bifilar winding. The primary winding corresponds to a current coil, and the secondary bifilar winding includes a first bifilar winding and a second bifilar winding connected in series. A start lead of the first bifilar winding is connected to a start lead of the second bifilar winding. The meter further includes a voltage source configured to generate a direct current (DC) voltage signal. The DC voltage signal is provided to a finish lead of the first bifilar winding. A first sense resistor is connected between a finish lead of the second bifilar winding and ground. A temperature coefficient of the first sense resistor is less than a temperature coefficient of resistivity of a material of the first bifilar winding and the second bifilar winding. The meter further includes a processing circuit configured to receive an input corresponding to a voltage across the first sense resistor. The processing circuitry is configured to use the voltage across the first sense resistor to determine a temperature associated with the current coil, The processing circuitry is further configured to detect a hot socket condition if the temperature exceeds a temperature threshold.

[0008] In another example, the meter includes a current transformer. The current transformer includes a primary winding, a secondary winding, and a secondary bifilar winding. The primary winding corresponds to a current coil, and the secondary bifilar winding includes a first bifilar winding and a second bifilar winding connected in parallel. A finish lead of the first bifilar winding is connected to a start lead of the second bifilar winding. The meter further includes a voltage source configured to generate a DC voltage signal. The DC voltage signal is provided to the finish lead of the first bifilar winding and the start lead of the second bifilar winding, and a first sense resistor is connected between the start lead of the first bifilar winding, the finish lead of the second bifilar winding, and ground. The temperature coefficient of the first sense resistor is less than the temperature coefficient of resistivity of materials of the first bifilar winding and the second bifilar winding. The meter further includes a processing circuit configured to receive an input corresponding to a voltage across the first sense resistor. The processing circuit is configured to use the voltage across the first sense resistor to determine a temperature associated with the current coil. The processing circuit is further configured to detect a hot socket condition if the temperature exceeds a temperature threshold.

[0009] In yet another example, the meter includes a current transformer. The current transformer includes a primary winding, a secondary winding, and a secondary bifilar winding. The primary winding corresponds to a current coil. The secondary bifilar winding includes a first bifilar winding and a second bifilar winding. A start lead of the first bifilar winding is connected to a start lead of the second bifilar winding. The meter further includes a voltage source configured to generate a DC voltage signal. The DC voltage signal is provided to a finish lead of the first bifilar winding. The meter further includes a first sense resistor connected between a finish lead of the second bifilar winding and ground. A temperature coefficient of the first sense resistor is less than a temperature coefficient of resistivity of a material of the first bifilar winding and the second bifilar winding. The meter further includes an A / D converter connected between the first sense resistor and an input of the processing circuit. The processing circuitry is configured to receive a signal from the A / D converter corresponding to the voltage across the first sense resistor, use the signal from the A / D converter to determine a temperature relative to the current coil, and detect a hot socket condition if the temperature exceeds a temperature threshold.

[0010] These illustrative examples are mentioned not to limit or define the present disclosure, but to provide examples to aid in understanding thereof. Further examples and further explanations are provided in the Detailed Description. [Brief description of the drawings]

[0011] These and other features, aspects, and advantages of the present disclosure will become better understood from the following detailed description when taken in conjunction with the accompanying drawings.

[0012] [Figure 1] FIG. 1 is a schematic block diagram of an exemplary measurement system according to one aspect of the present disclosure. [Diagram 2] FIG. 2 is a schematic diagram of an exemplary temperature sensor circuit having a bifilar winding with windings connected in series, according to one aspect of the disclosure. [Diagram 3] 1 is a graph illustrating measured voltage versus temperature according to one aspect of the present disclosure. [Figure 4] FIG. 2 is a schematic diagram of an exemplary temperature sensor circuit having a bifilar winding with windings connected in parallel, according to one aspect of the disclosure. [Diagram 5] 1 is a graph illustrating measured voltage versus temperature according to one aspect of the present disclosure. [Figure 6] 11 is a flow chart illustrating an example of a process for deriving a temperature of a current coil according to an aspect of the present disclosure. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Aspects of the present disclosure relate to detecting hot socketing in an electric meter. Hot socketing refers to a condition in which components of an electric meter, such as current carrying blades or jaws of a socket, wear or become damaged, causing a potentially dangerous increase in temperature within the electric meter. Hot socketing can occur when the jaws, blades or current coils deteriorate over time.

[0014] Previous solutions to detect hot socketing include adding a temperature sensor to the meter or using a modified current transformer with an additional secondary winding. The additional secondary winding is biased with a voltage to create a current that is in part indicative of the permeability of the current transformer. The permeability of the current transformer is temperature dependent, from which the temperature is derived. However, with this solution, the bias voltage must be applied intermittently to minimize the net magnetization by the winding and maintain the accuracy of the current sensor. This results in less frequent temperature measurements, which can affect the accuracy of the current measurement.

[0015] In contrast, aspects of the present disclosure obtain temperature measurements by biasing an auxiliary bifilar winding around a core of a current transformer that is placed in close proximity to the blade or current coil. The bifilar winding includes two closely spaced parallel windings. The current transformer may be a current transformer found in an electric meter, for example, a current transformer configured to measure the current flowing through a current coil.

[0016] The bifilar windings may be interconnected in parallel or in series. For example, in a series configuration, the start lead of the first winding is connected to the start lead of the second winding, the finish lead of the first winding is connected to a voltage source, and the finish lead of the second winding is connected to a sense resistor. In contrast, in a parallel configuration, the bifilar windings are configured such that the start lead of the first winding and the finish lead of the second winding are connected to a voltage source, and the finish lead of the first winding and the finish lead of the second winding are connected to a sense resistor.

[0017] Technical advantages of the present disclosure include more frequent temperature measurements and more accurate current measurements without the need for a temperature sensor. For example, previous solutions, by applying a direct current (DC) voltage to the secondary winding, may cause saturation and / or distortion of the measurement of the current through the sense resistor, thereby reducing the accuracy of the temperature measurement obtained therefrom. Further advantages include the ability to constantly apply a bias voltage because the magnetic fields of the bifilar windings cancel each other out.

[0018] Turning now to the drawings, FIG. 1 is a schematic block diagram of an exemplary measurement system according to one embodiment of the present disclosure. FIG. 1 illustrates a measurement environment 100 including power lines 50a-n, a load 60, a meter 101, and a power source 104. In the example illustrated in FIG. 1, the power lines 50a-n deliver power from the power source 104 to the load 60 via the meter 101. The meter 101 performs various instrumentation including voltage current measurement, current measurement, and temperature measurement.

[0019] Figure 1 shows three power lines (each phase 5, 6, and a neutral wire 50n. However, the meter 101 may have any number of phases. For example, the meter 101 may be adapted to connect to a variety of other standard power line configurations associated with a standard electrical supply, including, but not limited to, a polyphase electrical supply and a single-phase residential supply.

[0020] Power lines 50a and 50b are provided to the meter 101 for measurement. The power lines 50a, 50b connect to a meter mounting device or socket having jaws 52a, 52b, 54a, 54b, and 54n. Specifically, the power lines 50a, 50b are electrically coupled to the jaws 52a, 52b, and the neutral line 50n is electrically coupled to the jaw 54n. The jaws 54a, 54b are electrically coupled to connections 60a and 60b of the load 60. The neutral line 50n is also coupled to the load 60. The jaws 52a, 52b, 54a, 54b, and 54n may be spring-loaded conductive receptacles configured to receive meter blades.

[0021] Meter 101 includes one or more of a supply switch 105, a sensor circuit 110, a measurement circuit 112, a power source 113, a communication circuit 121, and a display 130. Sensor circuit 110 can be configured to measure voltage, current, and / or temperature. For example, as shown, sensor circuit includes voltage sensor circuit 140, current sensor circuits 160 and 180, and temperature sensor circuits 170 and 190. The measurement signals generated by sensor circuit 110 are analog signals having respective waveforms representative of the voltage and current delivered to the load. The measurement signals are passed to measurement circuit 112.

[0022] The supply switch 105 is configured to enable or disable the connection of the power lines 50a-n to the meter 101. The supply switch 105 is a relay controllable by the processing circuitry 115. The processing circuitry 115 can cause the supply switch 105 to enable or disable the connection of the power lines 50a-n. In this way, the power supplier can enable or disable power remotely.

[0023] The meter 101 further includes current coils 122 and 124, which may be partially inside the meter 101. The current coil 122 includes a body 122a of a conductive metal, such as a copper rod, terminating at either end in blades 122b and 122c. When the meter 101 is properly installed in the meter mounting device, the blade 122b is received by jaw 52a and the blade 122c is received by jaw 54a. Thus, electricity may flow from the power line 50a through jaw 52a, the current coil 122, jaw 54a, and connection 60a to the load 60. The blades 122b, 122c are generally external to the housing, while the body 122a of the current coil 122 extends through the interior of the housing.

[0024] Similarly, the current coil 124 includes a body 124a of a conductive metal, such as a copper rod, terminating at either end in blades 124b and 124c. When the meter 101 is properly installed, blade 124b is received by jaw 52b and blade 124c is received by jaw 54b. Thus, electricity can flow from the power line 50b through jaw 52b, the current coil 124, jaw 54b, and connection 60b to the load 60. The blades 124b, 124c are generally external to the housing, while the body 124a of the current coil 124 extends through the interior of the housing. The neutral wire 50n is coupled into the meter via blade 125.

[0025] Temperature sensor circuits 170 and 190 are configured to identify phenomena indicative of a hot socket condition. Such phenomena include the temperature of meter 101 exceeding a threshold temperature level. Temperature sensor circuit 170 is configured to measure the temperature of current coil 122 (supplied with electricity of the first phase), and temperature sensor circuit 190 is configured to measure the temperature of current coil 124 (supplied with electricity of the second phase). Thus, in a multi-phase system, multiple temperature sensor circuits may be employed, for example, one temperature sensor circuit per phase.

[0026] More specifically, the temperature sensor circuit 170 is connected to a winding 172 on a core 174. The core 174 may be the same core as described with respect to the current sensor circuit 160, for example a core arranged to detect the current in the current coil 122. The winding 172 is a bifilar winding, i.e. two parallel windings around the core 174. Further details are described with respect to Figs. 2 and 4. Similarly, the temperature sensor circuit 190 is connected to a winding 192 on a core 194. The core 194 may be the same core 184 as described with respect to the current sensor circuit 180, for example a core arranged to detect the current in the current coil 124. The winding 192 is a bifilar winding, i.e. two parallel windings around the core 194. Examples of the temperature sensor circuits 170 and 190 are described with respect to Figs. 2 and 4.

[0027] If the temperature sensor circuits 170 and / or 190 detect a hot socket condition, the meter 101 may be configured to send a warning signal to a remote device so that mitigation steps can be taken to prevent or minimize damage to the meter 101 and to prevent or minimize interruption of supply to the load 60. Mitigation steps may include remotely causing the supply switch 105 to disconnect the supply.

[0028] The current sensor circuit 160 is operable to detect a current flowing through the current coil 122. The current sensor circuit 160 includes a winding 162 disposed about a core 164. The core 164 may be part of a current transformer arranged to detect a current in the current coil 122. The current sensor circuit 180 is operable to detect a current flowing through the current coil 124. The current sensor circuit 180 includes a winding 182 disposed about a core 184. The core 184 may be part of a current transformer arranged to detect a current in the current coil 124.

[0029] The measurement circuit 112 includes an analog-to-digital (A / D) converter 114 and a processing circuit 115. The processing circuit 115 may be part of a commercially available chip package that includes the A / D converter 114, memory 120, and / or other supporting devices. The A / D converter 114 may be any suitable analog-to-digital converter configured to sample an analog measurement signal generated by the sensor circuit 110. The A / D converter 114 is operably coupled to provide the generated digital measurement signal to the processing circuit 115.

[0030] The processing circuit 115 includes a processing device configured to execute program instructions stored in memory to perform the various functions described herein and other measurement functions. The processing circuit 115 is operatively coupled to receive the digital measurement signal from the A / D converter 114 and generate voltage measurements, current measurements, temperature measurements, or energy consumption data therefrom. In FIG. 6, an example of a process used to generate a temperature measurement is described. The processing circuit 115 may include a digital processing circuit. The digital processing circuit processes the digitized measurement signal and thereby generates energy consumption data, power consumption data, voltage data, current data, or temperature data. The processing circuit 115 may include the functionality of a controller and / or a digital signal processor. The processing circuit 115 may suitably include general control circuitry and supervisory processing circuitry, not shown in detail. The processing circuit 115 communicates information with external devices through a serial input / output port, not shown, or through a communication circuit, also not shown.

[0031] Memory 120 includes one or more storage devices of various types. Memory 120 may include volatile or non-volatile random access memory, read-only memory, or other readable and / or writable memory devices. Memory 120 stores instructions and / or parameters used by processing circuit 115 to perform operations described herein, and may further store energy consumption data. Memory 120 may include a non-transitory computer-readable medium.

[0032] Communications circuitry 121 is operatively coupled to communicate information with at least one external device, as well as processing circuitry 115. To this end, communications circuitry 121 may include an optical transceiver disposed in a translucent or transparent optical port, not shown. Communications circuitry 121 may also include remote communications circuitry, such as a power line modem, a radio frequency (RF) transceiver, e.g., a pager radio, or other wireless device capable of transmitting over a wide area network (WAN) or other wireless communications network, or a cellular radio.

[0033] Display 130 is any display suitable for outputting information about meter 100, such as a liquid crystal display (LCD), a light emitting diode (LED) display, or a touch screen. For example, the information may include the operating status of meter 100, such as measurement or network status, or consumption information.

[0034] FIG 2 is a schematic diagram of an example temperature sensor circuit having a bifilar winding with windings connected in series, according to one embodiment of the disclosure. FIG 2 shows a meter environment 200 including a temperature sensor circuit 201, a current coil 202, a converter 210, an A / D converter 114, a processing circuit 115, a DC voltage source 250, and a current sensor circuit 260. The DC voltage source 250 may be provided by the meter's power supply or may be provided from another component within the meter. The temperature sensor circuit 201 is an example of the temperature sensor circuit 170 or 190.

[0035] The temperature sensor circuit 201 includes a first bifilar winding 220, a second bifilar winding 230, and a sense resistor 240. The first bifilar winding 220 includes a start lead 222 and a finish lead 224. The second bifilar winding 230 includes a start lead 232 and a finish lead 234. The first bifilar winding 220 and the second bifilar winding 230 are identical in length and are wound on the core of the transformer 210 such that the start lead 222 and the start lead 232 are at a first end of the current transformer and the finish lead 224 and the finish lead 234 are at a second end of the current transformer.

[0036] The converter 210 is arranged to detect the current in the current coil 202, which is a primary winding. The converter 210 includes a first bifilar winding 220 and a second bifilar winding 230, which are secondary windings, and a current sensor winding 270, which is also a secondary winding. The current sensor winding 270 is used by a current sensor circuit 260 to sense the current flowing in the current coil 202. The current sensor circuit 260 includes a sense resistor 261.

[0037] As depicted, first bifilar winding 220 and second bifilar winding 230 are in a series configuration. Start lead 222 is connected to start lead 232. Finish lead 224 is connected to a DC voltage source 250. Finish lead 234 is connected to a first end of sense resistor 240 and to an input of A / D converter 114. A second end of sense resistor 240 is connected to ground.

[0038] In an alternative configuration (not shown), finish lead 224 is connected to finish lead 234. In this configuration, start lead 222 is connected to a DC voltage source 250, and start lead 232 is connected to a first end of sense resistor 240, the second end of which is connected to ground.

[0039] The first bifilar winding 220 has a resistivity R1, the second bifilar winding 220 has a resistivity R2, and the sense resistor has a resistance R3. In some examples, the resistance R3 of the sense resistor is greater than the resistivity of the windings of the bifilar winding. In one example, the resistivity of each of the bifilar windings is 100 ohms, the resistance of the sense resistor is 200 ohms, the specific impedance L1 of the first bifilar winding 220 is 50 henries, and the specific impedance L2 of the second bifilar winding is 50 henries.

[0040] Because the temperature coefficient (or temperature coefficients) of resistivity of the first and second bifilar windings are different from the temperature coefficient of resistivity of the sense resistor, as the temperature of the current coil (primary winding) changes, the measured voltage across the sense resistor R3 changes. In one example, the temperature coefficient of the sense resistor is less than the temperature coefficient of each bifilar winding. Example temperature coefficients include 0.00393 for each bifilar winding and 0.0001 for the sense resistor.

[0041] When a voltage is applied by the DC voltage source 250, the A / D converter 114 receives a signal indicative of the voltage across the sense resistor 240. In one example, the DC voltage source provides approximately 3.3 volts to the finish lead of the first bifilar winding. The A / D converter converts the signal to a digital output. The processing circuitry 115 receives the digital output signal from the A / D converter 114 and uses the digital signal to determine a temperature value. The voltage level provided by the DC voltage source and the size of the sense resistor may be selected based on the specifications of the A / D converter. In some embodiments, the voltage and resistance are selected such that the input to the A / D converter when the current coil is operating at the expected normal operating temperature is in the middle of the range of the A / D converter. As the temperature of the current coil changes, the measured voltage across the sense resistor changes. Thus, the measured voltage is indicative of temperature, as shown in FIG. 3.

[0042] 3 is a graph showing measured voltage versus temperature according to one embodiment of the present disclosure. FIG 3 shows a graph 300 including a plot 310. Plot 310 shows sensed voltage 302 versus temperature 301. It can be seen that as the temperature increases, the sensed voltage decreases.

[0043] FIG 4 is a schematic diagram of an exemplary temperature sensor circuit having a bifilar winding with windings connected in parallel according to one embodiment of the disclosure. FIG 4 shows a meter environment 400 including a temperature sensor circuit 401, a current coil 402, a current transformer 410, an A / D converter 114, a processing circuit 115, a DC voltage source 450, and a current sensor circuit 460. The DC voltage source 450 may be provided by the meter's power supply or may be provided from another component within the meter. The temperature sensor circuit 401 is an example of the temperature sensor circuit 170 or 190.

[0044] The temperature sensor circuit 401 includes a first bifilar winding 420, a second bifilar winding 430, and a sense resistor 440. The first bifilar winding 420 includes a start lead 422 and a finish lead 424. The second bifilar winding 430 includes a start lead 432 and a finish lead 434. The first bifilar winding 420 and the second bifilar winding 430 are identical in length and are wound on the core of the current transformer 410 such that the start leads 422 and 432 are at a first end of the current transformer and the finish leads 424 and 434 are at a second end of the current transformer.

[0045] The current transformer 410 is arranged to detect the current in the current coil 402, which is a primary winding, and includes a first bifilar winding 420 and a second bifilar winding 430, which are secondary windings, and a current sensor winding 470, which is also a secondary winding. The current sensor winding 470 is used by a current sensor circuit 460 to sense the current flowing in the current coil 402. The current sensor circuit 460 includes a sense resistor 461.

[0046] The first bifilar winding 420 and the second bifilar winding 430 are connected in parallel. The start lead 422 and the finish lead 434 are connected together and to a DC voltage source 450. The finish lead 424 and the start lead 432 are connected to a sense resistor 440, which is in turn connected to ground. The finish lead 424 and the start lead 432 are also connected to the inputs of the A / D converter 114. In this manner, the first bifilar winding 420 and the second bifilar winding 430 are oriented to produce opposing but equal magnetic fields. Thus, the magnetic field produced by the current flowing through the first bifilar winding 420 cancels the magnetic field produced by the current flowing through the second bifilar winding 430, resulting in a zero net flux on the core and a very small effect on the accuracy of the current measurements made by the current sensor circuit 460.

[0047] The first bifilar winding 420 has a resistivity R1, the second bifilar winding 420 has a resistivity R2, and the sense resistor has a resistance R3. In some examples, the resistance R3 of the sense resistor is greater than the resistivity of the windings of the bifilar winding. In one example, the resistivity of each of the bifilar windings is 10,000 ohms, the resistance of the sense resistor is 5,000 ohms, the specific impedance L1 of the first bifilar winding 420 is 100 henries, and the specific impedance L2 of the second bifilar winding 430 is 100 henries.

[0048] Because the temperature coefficient (or temperature coefficients) of resistivity of the first and second bifilar windings are different from the temperature coefficient of resistivity of the sense resistor, as the temperature of the current coil (primary winding) changes, the measured voltage across the sense resistor R3 changes. In one example, the temperature coefficient of the sense resistor is less than the temperature coefficient of each bifilar winding. Example temperature coefficients include 0.00393 for each bifilar winding and 0.001 for the sense resistor.

[0049] When a voltage is applied by the DC voltage source 450, the A / D converter 114 receives a signal indicative of the voltage across the sense resistor 440. In one example, the DC voltage source provides approximately 3.3 volts to the start lead of the first bifilar winding. The A / D converter converts the signal to a digital output. The processing circuitry 115 receives the digital output signal from the A / D converter 114 and uses the digital signal to determine a temperature value. The voltage level provided by the DC voltage source and the size of the sense resistor may be selected based on the specifications of the A / D converter. In some embodiments, the voltage and resistance are selected such that the input to the A / D converter is in the middle of the range of the A / D converter when the current coil is operating at the expected normal operating temperature. As the temperature of the current coil changes, the measured voltage across the sense resistor changes. Thus, the measured voltage is indicative of temperature, as shown in FIG. 5.

[0050] 5 is a graph showing measured voltage versus temperature according to one embodiment of the present disclosure. FIG 5 shows a graph 500 including a plot 510. Plot 510 shows sensed voltage 502 versus temperature 501. It can be seen that as the temperature increases, the sensed voltage decreases.

[0051] 6 is a flow chart illustrating an example of a process for deriving a temperature of a current coil according to one embodiment of the present disclosure, which is described with respect to the circuit illustrated by FIG. 2 for illustrative purposes, but may also be performed with the circuit illustrated by FIG.

[0052] In block 601, process 600 includes applying a direct current (DC) voltage signal to a secondary bifilar winding of a current transformer. Using Figure 2 as an example, processing circuitry 115 causes a DC voltage from DC voltage source 250 to be applied to first bifilar winding 220 and second bifilar winding 230. As long as power is supplied to meter 101, processing circuitry 115 can supply power to DC voltage source 250, which in turn supplies power to the bifilar windings.

[0053] At block 602, the process 600 includes receiving an input corresponding to a voltage across a sense resistor connected to the bifilar winding. The A / D converter 114 receives a signal indicative of the voltage across the sense resistor 240.

[0054] At block 603, process 600 includes determining a temperature using the voltage across the sense resistor. Processing circuitry 115 receives a digitized voltage representative of the voltage across the sense resistor from A / D converter 114 and converts the digitized voltage to a temperature. Processing circuitry 115 may use a predefined ratio or scale between voltage and temperature (e.g., as depicted in FIG. 3).

[0055] At block 604, process 600 includes detecting a hot socket condition in response to determining that the temperature exceeds the temperature threshold. If the temperature is greater than the temperature threshold, processing circuitry 115 may identify a hot socket condition. In response, processing circuitry 115 may perform an action, such as causing communication circuitry 121 to send a message toward the head-end system or disconnecting supply switch 105.

[0056] While the present subject matter has been described in detail with respect to certain aspects thereof, it will be appreciated that those skilled in the art, upon gaining an understanding of the foregoing, may readily make modifications, variations, and equivalents to such aspects. Accordingly, it should be understood that the present disclosure has been presented for purposes of illustration and not limitation, and is not intended to exclude the inclusion of modifications, variations, and / or additions to the present subject matter as would be readily apparent to one of ordinary skill in the art.

Claims

1. a current transformer including a primary winding, a secondary winding, and a secondary bifilar winding; A voltage source configured to generate a DC voltage signal; a first sense resistor; processing circuitry; The primary winding corresponds to a current coil; the secondary bifilar winding includes a first bifilar winding and a second bifilar winding connected in series; a start lead of the first bifilar winding connected to a start lead of the second bifilar winding; the DC voltage signal is provided to a finish lead of the first bifilar winding; the first sense resistor is connected between a finish lead of the second bifilar winding and ground; a temperature coefficient of the first sense resistor is less than a temperature coefficient of resistivity of a material of the first bifilar winding and the second bifilar winding; The processing circuitry includes: receiving an input corresponding to a voltage across the first sense resistor; using the voltage across the first sense resistor to determine a temperature associated with the current coil; Detecting a hot socket condition if the temperature exceeds a temperature threshold. It was configured as follows: Meter.

2. An A / D converter is further provided, an input of the A / D converter is connected to the first sense resistor and an output of the A / D converter is connected to the processing circuit and provides an input corresponding to the voltage across the first sense resistor; 2. The meter of claim 1.

3. a second sense resistor connected between the secondary winding and ground; The processing circuitry includes: receiving an input corresponding to a voltage across the second sense resistor; The voltage across the second sense resistor is used to determine the current associated with the current coil. Further configured as follows:

2. The meter of claim 1.

4. 2. The meter of claim 1, wherein the resistance of said first sense resistor is greater than the resistance of said first bifilar winding and said second bifilar winding.

5. A communication circuit is further provided, the processing circuitry is further configured to communicate a message indicative of the hot socket condition to a remote system via the communication circuitry.

2. The meter of claim 1.

6. a supply switch for controlling connection of the meter to a power source; the processing circuitry is further configured to control the supply switch to disconnect the meter from the power source in response to receiving a message via the communication circuitry including a disconnect command.

6. The meter of claim 5.

7. the current coil corresponds to a first phase of electricity and the second current coil corresponds to a second phase of electricity; The meter is a second current transformer including a primary winding, a secondary winding, and a secondary bifilar winding; a third sense resistor; a primary winding of the second current transformer corresponds to the second current coil; the secondary bifilar winding of the second current transformer includes a first bifilar winding and a second bifilar winding; the third sense resistor is connected between a finish lead of a second bifilar winding of the second current transformer and ground; The processing circuitry includes: receiving an input corresponding to a voltage across the third sense resistor; using the voltage across the third sense resistor to determine a temperature associated with the second current coil; Detecting the hot socket condition if the temperature exceeds the temperature threshold. It was configured as follows:

2. The meter of claim 1.

8. a current transformer including a primary winding, a secondary winding, and a secondary bifilar winding; A voltage source configured to generate a DC voltage signal; a first sense resistor; processing circuitry; The primary winding corresponds to a current coil; the secondary bifilar winding includes a first bifilar winding and a second bifilar winding connected in parallel; a finish lead of the first bifilar winding connected to a start lead of the second bifilar winding; the DC voltage signal is applied to the finish lead of the first bifilar winding and to the start lead of the second bifilar winding; the first sense resistor is connected between a start lead of the first bifilar winding, a finish lead of the second bifilar winding, and ground; a temperature coefficient of the first sense resistor is less than a temperature coefficient of resistivity of a material of the first bifilar winding and the second bifilar winding; The processing circuitry includes: receiving an input corresponding to a voltage across the first sense resistor; using the voltage across the first sense resistor to determine a temperature associated with the current coil; Detecting a hot socket condition if the temperature exceeds a temperature threshold. It was configured as follows: Meter.

9. An A / D converter is further provided, an input of the A / D converter is connected to the first sense resistor and an output of the A / D converter is connected to the processing circuit and provides an input corresponding to the voltage across the first sense resistor; 9. The meter of claim 8.

10. a second sense resistor connected between the secondary winding and ground; The processing circuitry includes: receiving an input corresponding to a voltage across the second sense resistor; The voltage across the second sense resistor is used to determine the current associated with the current coil. Further configured as follows:

9. The meter of claim 8.

11. 9. The meter of claim 8, wherein the resistance of the first sense resistor is greater than the resistance of the first bifilar winding and the second bifilar winding.

12. A communication circuit is further provided, the processing circuitry is further configured to communicate a message indicative of the hot socket condition to a remote system via the communication circuitry.

9. The meter of claim 8.

13. a supply switch for controlling connection of the meter to a power source; the processing circuitry is further configured to control the supply switch to disconnect the meter from the power source in response to receiving a message via the communication circuitry including a disconnect command.

13. The meter of claim 12.

14. the current coil corresponds to a first phase of electricity and the second current coil corresponds to a second phase of electricity; The meter is a second current transformer including a primary winding, a secondary winding, and a secondary bifilar winding; a third sense resistor; a primary winding of the second current transformer corresponds to the second current coil; the secondary bifilar winding of the second current transformer includes a first bifilar winding and a second bifilar winding; the third sense resistor is connected between a finish lead of a second bifilar winding of the second current transformer and ground; The processing circuitry includes: receiving an input corresponding to a voltage across the third sense resistor; using the voltage across the third sense resistor to determine a temperature associated with the second current coil; Detecting the hot socket condition if the temperature exceeds the temperature threshold. It was configured as follows:

9. The meter of claim 8.

15. a current transformer including a primary winding, a secondary winding, and a secondary bifilar winding; A voltage source configured to generate a DC voltage signal; a first sense resistor; an A / D converter connected between the first sense resistor and an input of a processing circuit; The primary winding corresponds to a current coil; the secondary bifilar winding includes a first bifilar winding and a second bifilar winding; a start lead of the first bifilar winding connected to a start lead of the second bifilar winding; the DC voltage signal is provided to a finish lead of the first bifilar winding; the first sense resistor is connected between a finish lead of the second bifilar winding and ground; a temperature coefficient of the first sense resistor is less than a temperature coefficient of resistivity of a material of the first bifilar winding and the second bifilar winding; The processing circuitry includes: receiving a signal from the A / D converter corresponding to a voltage across the first sense resistor; determining a temperature associated with the current coil using the signal from the A / D converter; Detecting a hot socket condition if the temperature exceeds a temperature threshold. It was configured as follows: Meter.

16. a second sense resistor connected between the secondary winding and ground; The processing circuitry includes: receiving an input corresponding to a voltage across the second sense resistor; The voltage across the second sense resistor is used to determine the current associated with the current coil. Further configured as follows:

16. The meter of claim 15.

17. 16. The meter of claim 15, wherein the resistance of the first sense resistor is greater than the resistance of the first bifilar winding and the second bifilar winding.

18. A communication circuit is further provided, the processing circuitry is further configured to communicate a message indicative of the hot socket condition to a remote system via the communication circuitry.

16. The meter of claim 15.

19. A communication circuit is further provided, the processing circuitry is further configured to communicate a message indicative of the hot socket condition to a remote system via the communication circuitry.

16. The meter of claim 15.

20. a supply switch for controlling connection of the meter to a power source; the processing circuitry is further configured to control the supply switch to disconnect the meter from the power source in response to receiving a message via the communication circuitry including a disconnect command.

20. The meter of claim 19.

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