Folded current sense shunt resistor

A shunt resistor may, in some cases, receive interference from magnetic fields. The shunt resistor may include a resistive element coupled between multiple conductive elements, and measurement circuitry coupled to the leads, forming an electrically conductive loop. Current through the shunt resistor may be determined by measuring the current through the resistive element at the leads. An induced voltage in the loop may be determined by the product of the loop area and the magnetic field passing through the loop. Consequently, when a magnetic field is passed through the shunt resistor loop, an undesirable interfering signal may be produced, distorting the output signal of the shunt resistor. As the interfering signal is a product of the loop area and the magnetic field, the geometry of the shunt resistor may be modified to reduce the loop area and thus reduce or minimize the interference on the shunt resistor.

BACKGROUND

This disclosure relates to current measurement in an electronic device. More particularly, this disclosure relates to shunt resistors implemented to measure current in an electronic device.

Shunt resistors may be used to measure current in an electronic device. The shunt resistors may measure current through the electronic device and produce a signal proportional to current flowing through the shunt resistor. The shunt resistor may, in some cases, receive interference from magnetic fields. The interference may distort the shunt resistor's output signal, leading to undesirable impacts on the shunt resistor (e.g., reduced current measurement accuracy).

DETAILED DESCRIPTION

Shunt resistors may be used to measure current in an electronic device or system. The shunt resistor may measure current through the electronic device and produce a signal (e.g., a voltage) proportional to current flowing through the shunt resistor. The shunt resistor may be implemented to replace a current transformer as the shunt resistor may consume less space and less power than a current transformer and, unlike a current transformer, may also measure direct current (DC).

The shunt resistor may, in some cases, receive interference from magnetic fields. When a shunt resistor is placed inside a magnetic field, the signal (e.g., the voltage) may be distorted by interfering electromagnetic signals (e.g., causing an induced voltage) induced by the magnetic fields. The interfering signals may be associated with a nearby power signal (e.g., a 50 hertz (Hz) power signal, a 60 Hz power signal, and so on) emitted from nearby electrical conductors, radio transmitters, electronic devices, naturally occurring electromagnetic compatibility events (e.g., an electrostatic discharge, such as a lightning strike), and so on.

The shunt resistor may include a resistive element coupled between multiple conductive elements. The conductive elements may each include conductive plates, the conductive plates include conductive leads (e.g., Kelvin leads) protruding beyond the resistive element. A high current signal may be passed to a first conductive plate, through the resistive element and out through a second conductive plate. The resistive element may convert the high current signal to a proportional low voltage signal. Measurement circuitry may be coupled to the shunt resistor via the leads, forming an electrically conductive loop. Current through the shunt resistor may be determined (e.g., via the measurement circuitry) based on the current through the resistive element at the leads and/or the voltage signal outputted by the resistive element. An induced voltage in the loop may be determined by the product of the loop area and the magnetic field passing through the loop. Consequently, when a magnetic field is passed through the shunt resistor loop, an undesirable interfering signal may be produced, distorting the output signal of the shunt resistor.

As the interfering signal (e.g., an induced voltage on the shunt resistor, particularly the resistive element of the shunt resistor) is a product of the loop area and the magnetic field passing through the loop, the geometry of the shunt resistor may be modified to reduce the loop area and thus reduce or minimize the interference on the shunt resistor. In some embodiments, the loop area may be reduced or minimized by affixing an insulative material to a portion of the shunt resistor (e.g., affixing the insulative material to a conductive plate, conductive leads, and/or a resistive element of the shunt resistor). A conductive material may then be overlaid on top of the insulative material. In some embodiments, the insulative and conductive materials may be affixed by a metal clip.

In other embodiments, the loop area may be reduced or minimized by folding the shunt resistor and/or the resistive element coupled to the shunt resistor such that the two conductive plates are disposed parallel to each other. The conductive plates may be separated by an insulative materials (e.g., air, a plastic compound, and so on). In some instances, it may be beneficial to reduce or minimize the space between the conductive plates to reduce or minimize the area of the loop. In some embodiments, the resistive element of the shunt resistor may be folded or manufactured into particular geometries that may further reduce the loop area.

FIG.1illustrates a simplified diagram of an electric power delivery system1, in accordance with an embodiment of the present disclosure. The electric power delivery system100may generate, transmit, and/or distribute electric energy to one or more loads. As illustrated, the electric power delivery system1includes electric generators10,12,14, and16. The electric power delivery system1may also include power transformers17,20,22,30,42,44, and50. Furthermore, the electric power delivery system may include lines24,34,36, and58to transmit and/or deliver power. Circuit breakers52,60, and76may be used control flow of power in the electric power delivery system1. Busses18,26,32, and48and/or loads38and40receive the power in and/or from (e.g., output by) the electric power delivery system1. A variety of other types of equipment may also be included in electric power delivery system1, such as current sensors (e.g., wireless current sensor (WCS)84), potential transformers (e.g., potential transformer82), voltage regulators, capacitors (e.g., capacitor74) and/or capacitor banks (e.g., capacitor bank (CB)88), antennas (e.g., antenna86), and other suitable types of equipment useful in power generation, transmission, and/or distribution.

A substation19may include the electric generator14, which may be a distributed generator, and which may be connected to the bus26through the power transformer17(e.g., a step-up transformer). The bus26may be connected to a distribution bus32via the power transformer30(e.g., a step-down transformer). Various distribution lines36and34may be connected to the distribution bus32. The distribution line36may be connected to a substation41where the distribution line36is monitored and/or controlled using an intelligent electronic device (IED)06, which may selectively open and close the circuit breaker52. A load40may be fed from distribution line36. The power transformer44(e.g., a step-down transformer), in communication with the distribution bus32via distribution line36, may be used to step down a voltage for consumption by the load40.

A distribution line34may deliver electric power to a bus48of the substation51. The bus48may also receive electric power from a distributed generator16via transformer50. The distribution line58may deliver electric power from the bus48to a load38, and may include the power transformer42(e.g., a step-down transformer). A circuit breaker60may be used to selectively connect the bus48to the distribution line34. The IED8may be used to monitor and/or control the circuit breaker60as well as the distribution line58.

The electric power delivery system1may be monitored, controlled, automated, and/or protected using IEDs such as the IEDs4,6,8,15, and70, and a central monitoring system72. In general, the IEDs in an electric power generation and transmission system may be used for protection, control, automation, and/or monitoring of equipment in the system. For example, the IEDs may be used to monitor equipment of many types, including electric transmission lines, electric distribution lines, current sensors, busses, switches, circuit breakers, reclosers, transformers, autotransformers, tap changers, voltage regulators, capacitor banks, generators, motors, pumps, compressors, valves, and a variety of other suitable types of monitored equipment.

As used herein, an IED (e.g., the IEDs4,6,8,15, and70) may refer to any processing-based device that monitors, controls, automates, and/or protects monitored equipment within the electric power delivery system1. Such devices may include, for example, remote terminal units, merging units, differential relays, distance relays, directional relays, feeder relays, overcurrent relays, voltage regulator controls, voltage relays, breaker failure relays, generator relays, motor relays, automation controllers, bay controllers, meters, recloser controls, communications processors, computing platforms, programmable logic controllers (PLCs), programmable automation controllers, input and output modules, and the like. The term IED may be used to describe an individual IED or a system including multiple IEDs. Moreover, an IED of this disclosure may use a non-transitory computer-readable medium (e.g., memory) that may store instructions that, when executed by a processor of the IED, cause the processor to perform processes or methods disclosed herein. Moreover, the IED may include a wireless communication system to receive and/or transmit wireless messages from a wireless electrical measurement device. The wireless communication system of the IED may be able to communicate with a wireless communication system of the wireless electrical measurement devices, and may include any suitable communication circuitry for communication via a personal area network (PAN), such as Bluetooth or ZigBee, a local area network (LAN) or wireless local area network (WLAN), such as an 802.11x Wi-Fi network, and/or a wide area network (WAN), (e.g., third-generation (3G) cellular, fourth-generation (4G) cellular, universal mobile telecommunication system (UMTS), long term evolution (LTE), long term evolution license assisted access (LTE-LAA), fifth-generation (5G) cellular, and/or 5G New Radio (5G NR) cellular). In some cases, the IEDs may be located remote from the respective substation and provide data to the respective substation via a fiber-optic cable.

A common time signal may be distributed throughout the electric power delivery system1. Utilizing a common time source68may ensure that IEDs have a synchronized time signal that can be used to generate time synchronized data, such as synchrophasors. In various embodiments, the IEDs4,6,8,15, and70may be coupled to a common time source(s)68and receive a common time signal. The common time signal may be distributed in the electric power delivery system1using a communications network62and/or using a common time source68, such as a Global Navigation Satellite System (“GNSS”), or the like.

According to various embodiments, the central monitoring system72may include one or more of a variety of types of systems. For example, the central monitoring system72may include a supervisory control and data acquisition (SCADA) system and/or a wide area control and situational awareness (WACSA) system. Additionally or alternatively, the central monitoring system72may include an intrusion detection system that may receive data (e.g., notifications, data packets, messages, and the like) from any of the IEDs4,6,8,15and central IED70and may process and/or troubleshoot the received data to determine a cause of a cybersecurity event or network abnormality. A central IED70may be in communication with the IEDs4,6,8, and15. The IEDs4,6,8and15may be located remote from the central IED70, and may communicate over various media such as a direct communication from IED6or over the communications network62. According to various embodiments, some IEDs may be in direct communication with other IEDs. For example, the IED4may be in direct communication with the central IED70. Additionally or alternatively, some IEDs may be in communication via the communications network62. For example, the IED8may be in communication with the central IED70via the communications network62. In some embodiments, an IED may refer to a relay, a merging unit, or the like.

Communication via the communications network62may be facilitated by networking devices including, but not limited to, multiplexers, routers, hubs, gateways, firewalls, and/or switches. In some embodiments, the IEDs and the network devices may include physically distinct devices. In certain embodiments, the IEDs and/or the network devices may be composite devices that may be configured in a variety of ways to perform overlapping functions. The IEDs and the network devices may include multi-function hardware (e.g., processors, computer-readable storage media, communications interfaces, etc.) that may be utilized to perform a variety of tasks that pertain to network communications and/or to operation of equipment within the electric power delivery system1.

A communications controller80may interface with equipment in the communications network62to create a software-defined network (SDN) that facilitates communication between the IEDs4,6,8,15, and70and the central monitoring system72. In various embodiments, the communications controller80may interface with a control plane (not shown) in the communications network62. Using the control plane, the communications controller80may direct the flow of data within the communications network62.

The communications controller80may receive information from multiple devices in the communications network62regarding transmission of data. In embodiments in which the communications network62includes fiber optic communication links, the data collected by the communications controller80may include reflection characteristics, attenuation characteristics, signal-to-noise ratio characteristics, harmonic characteristics, packet loss statics, and the like. In embodiments in which the communications network62includes electrical communication links, the data collected by the communications controller80may include voltage measurements, signal-to-noise ratio characteristics, packet loss statics, and the like. In some embodiments, the communications network62may include both electrical and optical transmission media. The information collected by the communications controller80may be used to assess a likelihood of a failure, to generate information about precursors to a failure, and to identify a root cause of a failure. The communications controller80may associate information regarding a status of various communication devices and communication links to assess a likelihood of a failure. Such associations may be utilized to generate information about the precursors to a failure and/or to identify root cause(s) of a failure consistent with embodiments of the present disclosure.

Embodiments presented herein may monitor communications of one or more of the IEDs4,6,8,15,70and, in particular, monitor data packets received at and/or transmitted from one or more of the IEDs4,6,8,15,70. Such monitoring may determine an occurrence of a security event, communications stresses, and/or the like.

With the foregoing in mind,FIG.2is a schematic diagram of a current measuring device100, including a shunt resistor102coupled to a measurement circuit104. The shunt resistor may include two conductive plates106A and106B and a resistive element110coupled between the conductive plates106A and106B. Each conductive plate106A and106B includes a lead108A and108B (e.g., Kelvin leads) to which the measurement circuit104is coupled. A loop112is formed by the conductive plates106A and106B (e.g., in particular, the leads108A and108B), and the resistive element110. In some embodiments, the conductive plates106A and106B and the leads108A and108B may include one or more conductive materials (e.g., copper) and the resistive element110may include one or more resistive materials (e.g., an alloy including copper, manganese, and nickel).

The shunt resistor102may receive an electrical current from an electronic device, such as the LEDs4,6,8,15, and70, convert (e.g., via the resistive element110) the current to a proportional voltage signal, and the measurement circuit104may determine the current supplied to the shunt resistor102based on the voltage signal. As mentioned above, a magnetic field may cause interference (e.g., an induced voltage) in the loop112. Consequently, the current measured by the measurement circuitry104may be less accurate due to the induced voltage. As the induced voltage is a product of the area of the loop112and the magnetic field passing through the loop112, the geometry of the shunt resistor102may be modified to reduce the area of the loop112and thus reduce or minimize the interference on the shunt resistor102.

FIG.3includes a schematic diagram200illustrating a top perspective of a shunt resistor202with a modified geometry and a schematic diagram204illustrating a side perspective of the shunt resistor202with the modified geometry, in accordance with an aspect of the present disclosure. The shunt resistor202may include the conductive plate106A, the lead108A, and the resistive element110. The shunt resistor202includes an insulator206(e.g., a thin sheet of insulative material, such as a plastic compound) coupled to the conductive plate106A, the lead108A, and the resistive element110. The shunt resistor202includes a conductor208(e.g., a thin sheet of conductive material, such as copper) electrically coupled to the insulator206and the conductive plate106B. The insulator206and the conductor208may be affixed to the shunt resistor202via a conductive clip. As may be observed from the schematic diagram204of the shunt resistor202, an electrically conductive loop (e.g., a loop210) is formed by the conductive plate106A, the lead108A, the resistive element110and the conductor208. The area of the loop210may be less than the area of the loop112discussed with respect toFIG.2. As discussed, the smaller area of the loop210may result in reduced interference (e.g., a smaller induced voltage) on the shunt resistor202due to a magnetic field. It may be observed that the shunt resistor110may be smaller, and thus may consume less area on a printed circuit board (PCB), due to the loop210being formed by conductive plate106A, the resistive element110, and the conductor208.

In some embodiments, an electrically conductive loop may be formed by folding a shunt resistor (e.g.,102) about an axis such that an edge surface of each of the conductive plates are positioned parallel to each other, with one conductive plate (e.g.,106A) is disposed a distance from another conductive plate (e.g.,106B).FIG.4includes a first perspective view300of a folded shunt resistor302and a second perspective view304of the folded shunt resistor302, in accordance with an aspect of the present disclosure. The folded shunt resistor302includes the conductive plates106A and106B, the conductive plates106A and106B including the conductive leads108A and108B, respectively. In some embodiments, the conductive plates106A and106B may be manufactured to include asymmetric geometries. For example, at least a portion of the conductive plate106A may extend outward about an axis a greater distance than the at least a portion of the conductive plate106B. While not shown inFIG.4, the measurement circuitry104may be coupled to the conductive leads108A and108B to determine the current through the shunt resistor302(e.g., based on the voltage of the resistive element110) as illustrated and discussed with respect toFIG.2andFIG.3.

The conductive plates106A and106B may be separated by an insulative material (e.g., air, a plastic compound, and so on). In some instances, it may be beneficial to minimize the space between the conductive plate106A and the conductive plate106B to minimize the area of an electrically conductive loop (e.g., loop308). The conductive plates106A and106B each include a ring terminal306A and306B, respectively. In some embodiments the ring terminals306A and306B may be symmetrically aligned. In other embodiments, the ring terminals306A and306B may be offset from each other (e.g., such that the ring terminal306A is set below the ring terminal306B). This may be accomplished by asymmetrically folding the shunt resistor302, drilling the ring terminals306A and306B at offset heights on their respective conductive plates, and so on.

The shunt resistor302includes the resistive element110. As may be observed with respect to the second perspective view304, the resistive element may be coupled to the conductive plates106A and106B. The resistive element110may be disposed beneath the conductive plates106A and106B. In some embodiments, the resistive element110may be enclosed on at least three sides by the conductive plates106A and106B. In other embodiments, the geometry of the resistive element110may be adjusted by folding the resistive element110, changing the size or shape of the resistive element110, and so on.

FIG.5is a folded shunt resistor400including a folded resistive element402, in accordance with an aspect of the present disclosure. Similar to the first perspective view300and the second perspective view304of the shunt resistor302discussed above, the shunt resistor400includes the conductive plates106A and106B, the conductive plates106A and106B including the leads108A and108B, respectively and including the ring terminals306A and306B, respectively. As discussed above, the conductive plates106A and106B may be separated by an insulative materials (e.g., air, a plastic compound, and so on). In some instances, it may be beneficial to minimize the space between the conductive plate106A and the conductive plate106B to minimize the area of an electrically conductive loop (e.g., loop404).

As discussed above, the ring terminals306A and306B may be symmetrically aligned or may be offset from each other (e.g., such that the ring terminal306B is set below the ring terminal306A, or vice versa). While not shown inFIG.5, the measurement circuitry104may be coupled to the conductive leads108A and108B to determine the current through the shunt resistor400(e.g., based on the voltage of the resistive element402) as illustrated and discussed with respect toFIG.2andFIG.3.

The folded resistive element402may be folded into a semicylindrical shape, such that a first edge surface406A and a second edge surface406B of the folded resistive element402are positioned parallel to each other and symmetrically about an axis. The first edge surface406A is coupled to the conductive plate106A such that the first edge surface406A and the conductive plate106A are positioned in parallel. The second edge surface406B is coupled to the conductive plate106B such that the second edge surface406B and the conductive plate106B are positioned in parallel. By folding the folded resistive element402, the area of the loop404may be reduced to less than loops associated with other configurations (e.g., the loop112). Consequently, the folded shunt resistor400and folded resistive element402may reduce the induced voltage on the folded shunt resistor400while preserving the current measuring characteristics of the folded shunt resistor400(e.g., by preserving the current measuring characteristics of the leads108A and108B).

FIG.6is a shunt resistor500including a resistive element502, wherein the resistive element502is a variation of the folded resistive element402discussed with respect toFIG.5, in accordance with an aspect of the present disclosure. The resistive element502may be manufactured into a rectangular block. For example, the resistive element502may be formed by combining (e.g., welding) two resistive sub-elements of a given thickness into a single structure. The resistive element502may be coupled or affixed to the conductive plates106A and106B to form the loop504. The resistive element502may preserve the resistive characteristics of the folded resistive element402and preserve the connection of the conductive plates106A and106B to the resistive element502while maintaining an electrically conductive loop with a relatively small area (e.g., the loop504).

It should be noted that the embodiments discussed above may be implemented alongside with or in conjunction with a variety of methods to reduce interference on a shunt resistor due to a magnetic field. For example, any of the embodiments discussed above may be enclosed within a chassis (e.g., a steel chassis) designed to shield the shunt resistor, the measurement circuitry, and so on from the magnetic field. Additionally, any of the embodiments discussed above may include an electrical connector geometry that enables any of the shunt resistors discussed above to be able to electrically couple to connectors designed to couple to a current transformer.

While specific embodiments and applications of the disclosure have been illustrated and described, it is to be noted that the disclosure is not limited to the precise configurations and devices disclosed herein. For example, the systems and methods described herein may be applied to an industrial electric power delivery system or an electric power delivery system implemented in a boat or oil platform that may or may not include long-distance transmission of high-voltage power. Accordingly, many changes may be made to the details of the above-described embodiments without departing from the underlying principles of this disclosure. The scope of the present disclosure should, therefore, be determined only by the following claims.

Indeed, the embodiments set forth in the present disclosure may be susceptible to various modifications and alternative forms, specific embodiments have been shown by way of example in the drawings and have been described in detail herein. However, it may be noted that the disclosure is not intended to be limited to the particular forms disclosed. The disclosure is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the disclosure as defined by the following appended claims. In addition, the techniques presented and claimed herein are referenced and applied to material objects and concrete examples of a practical nature that demonstrably improve the present technical field and, as such, are not abstract, intangible or purely theoretical. Further, if any claims appended to the end of this specification contain one or more elements designated as “means for [perform]ing [a function] . . . ” or “step for [perform]ing [a function] . . . ”, it is intended that such elements are to be interpreted under 35 U.S.C. 112(f). For any claims containing elements designated in any other manner, however, it is intended that such elements are not to be interpreted under 35 U.S.C. 112(f).