Reinforced impedance for voltage sensing

Abstract

A system includes: a current interrupter that includes a first terminal, a second terminal, and a switching apparatus between the first terminal and the second terminal. The system also includes an impedance assembly configured to sense a voltage at one or more of the first terminal and the second terminal, the impedance assembly including a linear impedance and a reinforcing structure on an exterior surface of the linear impedance. The reinforcing structure includes an electrically insulating material wrapped around the linear impedance.

Description

[0001] REINFORCED IMPEDANCE FOR VOLTAGE SENSING

[0002] CROSS-REFERENCE TO RELATED APPLICATION

[0003] This application claims the benefit of U.S. Provisional Application No. 63 / 556,580, filed on February 22, 2024 and titled REINFORCED IMPEDANCE FOR VOLTAGE SENSING, which is incorporated herein by reference in its entirety.

[0004] TECHNICAL FIELD

[0005] This disclosure relates to a reinforced impedance for voltage sensing.

[0006] BACKGROUND

[0007] A current interrupter is used to interrupt current to a load. In operational use, the current interrupter is at a relatively high voltage, for example, 1 kilovolts (kV) or higher. The current interrupter is enclosed in a housing.

[0008] SUMMARY

[0009] In one aspect, a system includes: a current interrupter that includes a first terminal, a second terminal, and a switching apparatus between the first terminal and the second terminal. The system also includes an impedance assembly configured to sense a voltage at one or more of the first terminal and the second terminal, the impedance assembly including a linear impedance and a reinforcing structure on an exterior surface of the linear impedance. The reinforcing structure includes an electrically insulating material wrapped around the linear impedance.

[0010] Implementations may include one or more of the following features.

[0011] The first terminal may be a source-side terminal, the second terminal may be a load-side terminal, and the impedance assembly may be configured to sense a voltage at the load-side terminal.

[0012] The first terminal may be a source-side terminal, the second terminal may be a load-side terminal, and the impedance assembly may be configured to sense a voltage at the source-side terminal. The linear impedance may include a linear resistor, and the reinforcing structure may be on an exterior surface of the linear resistor. The linear resistor may include a ceramic body and one or more electrically conductive traces on an exterior of the ceramic body.

[0013] The impedance assembly also may include a solid dielectric housing on the reinforcing structure. The solid dielectric housing may be an overmolded solid dielectric structure. The solid dielectric housing may be a stuffed housing.

[0014] The impedance assembly also may include a first fitting configured to provide an electrical and mechanical connection to a first end of the linear impedance, and a second fitting configured to provide an electrical and mechanical connection to a second end of the linear impedance.

[0015] The reinforcing structure may include fiberglass and resin.

[0016] The reinforcing structure may include a sheet of woven electrically insulating fibers.

[0017] The reinforcing structure may include one or more of a sheet, tape, and fabric that includes one or more fibers.

[0018] The reinforcing structure may be wound about the exterior surface of the linear impedance in a helix.

[0019] The first terminal may be a load-side terminal, the second terminal may be a source-side terminal, the linear impedance may be a linear resistor, and the current interrupter also may include a housing that extends from a first end to a second end. The housing may enclose the current interrupter, and the load-side terminal may be at the first end of the housing. A tank may be coupled to the second end of the housing; and the impedance assembly may be electrically connected between the load-side terminal and the tank. The system also may include a voltage sensor configured to produce an indication of the electrical current that flows in the linear resistor. The voltage sensor may be embedded in the housing that encloses the current interrupter.

[0020] In some implementations, the system also includes a voltage sensor in an operating rod of the current interrupter.

[0021] In another aspect, an apparatus includes: a resistor assembly that includes a linear resistor with a resistor body; a first fitting at a first end of the resistor assembly; a second fitting at a second end of the resistor assembly; and a reinforcing structure wrapped around the resistor body. At least part of the reinforcing structure is directly on an exterior surface of the resistor body, an exterior of part of the first fitting, and an exterior of part of the second fitting.

[0022] Implementations may include one or more of the following features.

[0023] The reinforcing structure may include one or more of a sheet, tape, and a fabric that includes fibers of an electrically insulating material.

[0024] The linear resistor may be substantially cylindrical; the first fitting may include a first tube; and the second fitting may include a second tube. The first tube may include first exterior threads, and the second tube includes second exterior threads.

[0025] The apparatus also may include an electrically insulating housing on part of the resistor assembly, at least part of the first fitting may extend from a first end of the electrically insulating housing, and at least part of the second fitting may extend from a second end of the electrically insulating housing.

[0026] The apparatus also may include an electrically conductive shield that at least partially surrounds a first end of the resistor body. The electrically conductive shield may be in contact with the first fitting. The electrically conductive shield may include a semiconductive layer.

[0027] The apparatus also may include an insulating adaptor configured to mechanically couple a shield electrode to the first fitting and to electrical isolate the shield electrode and the linear resistor.

[0028] The first fitting may provide a first mechanical and electrical connection interface for the resistor assembly, and the second fitting may provide a second mechanical and electrical connection interface for the resistor assembly.

[0029] In another aspect, a method includes: coupling a first connection point to a linear impedance; coupling a second connection point to the linear impedance; preparing a reinforced linear impedance by: wrapping the linear impedance with an electrically insulating layer, the electrically insulating layer including fibers of an electrically insulating material; and forming a reinforcing structure from the electrically insulating layer, the reinforcing structure being in direct contact with an exterior surface of the linear impedance; and installing the reinforced linear impedance in an electrically insulating housing with the first connection point and the second connection point extending from the electrically insulating housing, and the electrically insulating housing in contact with the reinforcing structure. In another aspect, an impedance assembly configured to sense a voltage at one or more terminals of a current interrupter includes: a linear impedance including: a body and at least one electrically conductive trace on an exterior surface of the body; a first electrically conductive endcap on a first end of the body and electrically connected to the at least one electrically conductive trace; a first fitting mechanically attached to the linear impedance, the first fitting being electrically isolated from the linear impedance and including an access point for electrically connecting to the linear impedance; and a reinforcing structure on an exterior surface of the linear impedance and at least part of the first fitting. The reinforcing structure includes an electrically insulating material wrapped around the linear impedance and part of the first fitting.

[0030] Implementations of any of the techniques described herein may include an impedance device, an impedance assembly, a voltage sensor, a linear resistor with a reinforcing structure, a system, an apparatus, and / or a method. The details of one or more implementations are set forth in the accompanying drawings and the description below. Other features will be apparent from the description and drawings, and from the claims.

[0031] DRAWING DESCRIPTION

[0032] FIG. 1A is a block diagram of a power system that includes a switching apparatus and an impedance device.

[0033] FIG. IB is a cross-sectional view of the impedance device of FIG. 1A.

[0034] FIG. 1C is a perspective view of a linear impedance.

[0035] FIGS. 2A and 2B are perspective views of an impedance assembly in an unassembled state.

[0036] FIG. 2C is a perspective view of the impedance assembly of FIGS. 2A and 2B in an assembled state.

[0037] FIG. 3A is a perspective exterior view of another impedance assembly.

[0038] FIG. 3B is a cross-sectional view of the impedance assembly of FIG. 3 A.

[0039] FIG. 3C is a detailed view of the inset labeled C in FIG. 3B.

[0040] FIG. 3D is a cross-sectional view of an impedance device that includes the impedance assembly of FIG. 3 A.

[0041] FIG. 4A is a cross-sectional view of another impedance apparatus. FIG. 4B is a cross-sectional view of an impedance device that includes the impedance apparatus of FIG. 4A.

[0042] FIG. 4C is a perspective exterior view of the impedance device of FIG. 4B.

[0043] FIG. 5A is a partial cross-sectional view of another impedance device.

[0044] FIG. 5B is a cross-sectional perspective view of a shield electrode.

[0045] FIG. 6A is a cross-sectional view of a stuffed housing.

[0046] FIG. 6B is a perspective view of a mold core.

[0047] FIG. 6C is a cross-sectional view of another impedance device.

[0048] FIG. 7 is a cross-sectional view of another impedance device.

[0049] FIG. 8 is a flow chart of a process for manufacturing or assembling a linear impedance device that may be used in the voltage sensor system.

[0050] DETAILED DESCRIPTION

[0051] FIG. 1A is a block diagram of a power system 100. The system 100 includes a switching apparatus 110 and an impedance device 195. The switching apparatus 110 controls an electrical connection between a source 102 and a load 103. The impedance device 195 includes an impedance assembly 150 and a housing 180. During operational use of the switching apparatus 110, the impedance assembly 150 draws current that a sensor system 190 uses to determine a load-side voltage of the switching apparatus 110. FIG. 1 A shows a cross-sectional view of the device 195 extending generally along the Z direction. FIG. IB is a cross-sectional view of the device 195 in the X- Y plane.

[0052] The impedance assembly 150 includes a linear impedance 152 that is wrapped in a reinforcing structure 170. The reinforcing structure 170 provides mechanical structure and electrical insulation for the linear impedance 152. The reinforcing structure 170 increases the mechanical and electrical resilience of the impedance assembly 150, reduces unexpected failure of the impedance assembly 150, and promotes efficient manufacturing of the impedance device 195.

[0053] The switching apparatus 110 includes a current interrupter 120. When the current interrupter 120 is open, the load 103 is disconnected from the source 102. When the current interrupter 120 is closed, the source 102 is electrically connected to the load 103. The switching apparatus 110 also includes a source-side terminal 104 and a load-side terminal 105. The current interrupter 120 is electrically connected to the source-side terminal 104 and the load-side terminal 105. The terminals 104 and 105 are accessible from the exterior of the switching apparatus 110 and allow the current interrupter 120 to be electrically connected to the source 102 and the load 103.

[0054] The switching apparatus 110 also includes a user interface 130 that is electrically isolated from the current interrupter 120 by an electrically insulating assembly 108. The electrically insulating assembly 108 may be an electrically insulating rod. The electrically insulating rod may be an actuation or operating rod that may also contain a voltage sensor, which can be used to measure the voltage on the load side of the switching apparatus 110 or the source side of the switching apparatus 110.

[0055] In the example of FIG. 1 A, the impedance device 195 is used to sense a load-side voltage. The impedance assembly 150 is electrically coupled to the load-side terminal 105 and a low-voltage terminal 131 on the user interface 130. During operational use of the switching apparatus 110, a current Ir flows in the impedance assembly 150 and there is a voltage drop Vr across the impedance assembly 150, with the load-side terminal 105 having a higher potential than the low-voltage terminal 131. The current Ir and / or the voltage drop Vr is measured by a sensor 191 and used, along with the known impedance of the linear impedance 152, to determine the voltage at the load-side terminal 105. The sensor 191 may be a current sensor, a voltage sensor, a power meter, or a combination of such devices.

[0056] Although FIG. 1 A shows the impedance device 195 in an implementation in which the voltage at the load-side terminal 105 is determined, the impedance device 195 may be used to determine the voltage at the source-side terminal 104. In implementations in which the impedance device 195 is used to determine the voltage at the source-side terminal 104, the impedance assembly 150 is electrically connected to the source-side terminal 104 and the low- voltage terminal 131.

[0057] Moreover, the sensor 191 is illustrated as being separate from the switching apparatus 110, but this is not necessarily the case. For example, the sensor 191 may be embedded in a component of the switching apparatus 110 or otherwise in the switching apparatus 110. In some implementations, the sensor 191 is a voltage sensor that is embedded in a housing that encloses the current interrupter 120. In some implementations, the sensor 191 is a voltage sensor that is inside electrically insulating assembly 108 (for example, inside a hollow electrically insulating operating rod). In these implementations, one or more resistors are inside the insulating operating rod, with the resistors electrically connected between (1) an electrical contact of the current interrupter 120 and (2) a conductor that is electrically connected to an overvoltage protection device and a low-arm resistor. Other implementations and configurations are possible.

[0058] The impedance assembly 150 includes the linear impedance 152 and the reinforcing structure 170 (shown with dotted shading in FIG. IB). FIG. 1C is a perspective view of the linear impedance 152. The linear impedance 152 includes a body 153, which has an exterior surface 155, and one or more conductive traces 151 on the exterior surface 155. In the example shown in FIGS. IB and 1C, the body 153 has a circular cross-section. Other implementations are possible. For example, the body 153 may have a square or rectangular cross-sectional.

[0059] The body 153 is made of any material that that has a constant impedance regardless of the current that flows through the material. For example, the body 153 may be made of a ceramic material. The conductive traces 151 may be any electrically conductive material. Examples of materials that may be used for the conductive traces 151 include, without limitation, silver and copper. The conductive traces 151 may have any type of arrangement on the exterior surface 155. For example, the conductive traces 151 can be wrapped in a helical pattern or may alternate wrap direction to produce a non-inductive trace. In another example, the conductive traces 151 may be rings that are separated along the Z direction and do not touch each other. The conductive traces 151 have a relatively thin cross-section compared with the length of their path, and this increases the resistance of the conductive traces 151. The conductive traces 151 may be covered with a protective insulation layer. The protective insulation layer may be made out of any insulating material that bonds well to the exterior surface 155. For example, silicone rubber, epoxy, glass, or a combination of such materials may be used for the protective insulation layer. The conductive traces 151 may be placed on the exterior surface 155 by any application process. For example, the conductive traces 151 may be printed or deposited onto the exterior surface 155.

[0060] This configuration results in the linear impedance 152 having consistent impedance over a variety of operating conditions. For example the linear impedance 152 has a consistent impedance even when exposed to a range of voltages, temperatures, and humidity levels. The impedance of the linear impedance 152 is constant, or independent of the voltage or current flowing through it, thus, the current flowing through the impedance will be linearly dependent on the voltage over the impedance.

[0061] The linear impedance 152 is in contrast with a non-linear impedance. The impedance of an element with a non-linear impedance is not constant and instead changes depending on the amplitude of the voltage across the element. An arrester that includes a metal-oxide varistor (MOV) is an example of a device that includes an element with a non-linear impedance. An arrester protects electrical equipment from power surges that may be caused by switching, equipment failures, lighting, falling objects, and other events. The impedance of the MOV is a bulk material property of the metal-oxide disk(s) or cylinder that make the arrester. The bulk material properties are not linear, and the current through the material is not linearly dependent on the voltage over the material. At normal operating voltages with no power surge, the MOV has a high impedance and is effectively an insulator that does not conduct current. At higher voltages during a surge, the MOV has a very low impedance and is a conductor. The arrester is typically connected to ground and thus conducts current to ground during a power surge, diverting the surge away from the protected electrical equipment.

[0062] On the other hand, the linear impedance 152 is not a non-linear impedance and does not include a non-linear impedance element such as an MOV. Moreover, the impedance assembly 150 is used for voltage sensing and does not act as an arrester. Because the linear impedance 152 is used for voltage sensing, it is also used in conjunction with a measurement circuit that includes a sensing resistor in series with the linear impedance 152. For example, in implementations in which the linear impedance 152 is a linear resistor, by measuring the voltage across a sensing resistor, the voltage at the terminal of interest (Vi) is determined by: Vo=Vi*R2 / (Rl+R2), where R1 is the resistance of the linear resistor 152, R2 is the resistance of the sensing resistor, and Vo is the measured voltage across the sensing resistor. The sensing resistor has a much lower resistance than the linear impedance 152. For example, the resistance of the linear impedance 152 may be three orders of magnitude larger than the resistance of the sensing resistor, with the linear impedance 152 having a resistance of 100 mega-ohms (M ) and the sensing resistor having a resistance of 100 kilo-ohms (k ). The sensing resistor may be in the user interface 130 or the low- voltage terminal 131. On the other hand, an arrester lacks a sensing resistor. This is because the arrester is intended to handle surges and the low-voltage terminal of the arrester is generally intended to be connected to ground through as small of an impedance as possible.

[0063] Other types of impedance dividers and sensors may be used for the impedance device 195 and sensor system 190 as well, for instance, a capacitive divider. If other types of impedance dividers are used, similar relations may be used to step down the voltage signal.

[0064] The reinforcing structure 170 is any type of electrically insulating and structural material that is capable of being bonded directly to the exterior surface 155 of the linear impedance 152 and may be capable of being bonded directly to the traces 151 (when the traces 151 are present). Examples of the reinforcing structure 170 include, without limitation, a cloth, tape, strip, or sheet that includes solid strands of a dielectric material held together to form a wrappable structure and / or individual fibers that are wet-wound with a resin onto the structure 170. The strands may be woven together or may be held together by a resin or adhesive. The solid strands may be, for example, strands of fiberglass or strands of a reinforced plastic. Other implementations are possible. For example, the reinforcing structure 170 may be a dielectric matrix with particles of a dielectric material distributed in a dielectric base material.

[0065] The impedance assembly 150 is enclosed in the housing 180. The housing 180 is made of any electrically insulating material. For example, the housing 180 may be a solid dielectric material. The housing 180 may be an over-molded housing or a stuffed housing. In implementations in which the impedance assembly 150 includes the housing 180, the reinforcing structure 170 is between the housing 180 and the linear impedance 152.

[0066] Some legacy approaches to sensing load-side or source-side voltage in a switching system use a resistor apparatus that includes a linear resistor, a cage that extends for the entire length of the linear resistor and surrounds all or part of the linear resistor to provide mechanical support, and an over-molded solid dielectric insulation. To assemble these legacy resistor apparatuses, the linear resistor is placed in the cage and the dielectric insulation flows into and around the cage. The dielectric insulation is allowed to cure and becomes the solid dielectric insulation.

[0067] After assembly of the legacy resistor apparatus, the solid dielectric insulation makes contact with the linear resistor and the cage is embedded in the cured dielectric insulation. The linear resistor, cage, and solid dielectric insulation are made of different materials and have different coefficients of thermal expansion. When the assembled resistor apparatus is installed and used, the resistor apparatus is exposed to a wide range of temperatures (for example, temperatures between -50°C and 160°C), and the linear resistor, cage, and solid dielectric insulation expand and / or contract at different rates. This can create mechanical stress on the components of the resistor apparatus. The mechanical stress may lead to cracking in the resistor apparatus and / or debonding of the solid-dielectric insulation and possible failure of the soliddielectric insulation. Additionally, the mechanical stress, can change the impedance value of the linear impedance and therefore reduce the accuracy of a sensor that relies on knowledge of the impedance value.

[0068] Furthermore, in the legacy design, when the assembly cools, the dielectric insulation may pull away from the linear resistor and the cage simultaneously such that the insulation is stretched between the cage and resistor, thereby applying mechanical stress to the linear resistor and the cage. Still other legacy approaches include an assembly that includes a fiberglass tube that encloses the linear resistor with the space between the fiberglass tube and the linear resistor is filled with an elastomer. In some of these approaches, the assembly is also used as an electrically insulating operating rod, as in the electrically insulating assembly 108, and the assembly is stuffed into a pre-formed, stretchable housing rather than having an over-molded housing, and the assembly generally does not experience large thermal gradients.

[0069] On the other hand, the device 195 does not include the tube or the cage. Instead, the reinforcing structure 170 provides mechanical reinforcement and electrical isolation to the linear impedance 152 while eliminating free space between the linear impedance 152 and the reinforcing structure 170. The reinforcing structure 170 is directly on the exterior surface 155 of the linear impedance 152. Moreover, the reinforcing structure 170 and the linear impedance 152 may have similar coefficients of thermal expansion such that, when the impedance assembly 150 is exposed to temperature extremes, the linear impedance 152 and the reinforcing structure 170 expand at similar rates. Additionally, the impedance assembly 150 is not subjected to large dynamic loads during use and does not include moving parts. Thus, the reinforcing structure 170 remains on the surface 155 of the linear impedance 152.

[0070] Finally, because the impedance device 195 lacks the cage, the housing 180 is not pulled or stretched in the manner that can occur in the legacy approach. For example, the housing 180 is not stretched between separate elements as can occur in legacy designs that use the cage. When the impedance device 195 cools, the outer diameter of the housing 180 will shrink but is not bonded to an outer or surrounding structure, so the housing 180 freely reduces in size without stretching. This reduces mechanical stress, thereby reducing the likelihood of debonding and making it more likely that the housing 180 remain attached to the reinforcing structure 170.

[0071] Before discussing examples of the impedance device 195 and the impedance assembly 150 in more detail, an overview of an electrical power distribution system 101 and the switching apparatus 110 is provided.

[0072] The source 102, the switching apparatus 110, and the load 103 are part of the power distribution system 101. The power distribution system 101 is an alternating current (AC) system with a system operating voltage of, for example, at least 1 kilovolt (kV), 25 kV, 27, kV, 29 kV, up to 34.5 kV, up to 38 kV, up to 69 kV, or 69 kV or higher and a fundamental frequency of, for example, 50 or 60 Hertz (Hz). The power distribution system 101 includes one or more AC electricity sources and one or more loads. The source 102 and the load 103 are examples of a source and load. The source(s) may be any source of electricity such as, for example, a power plant that generates electricity from fossil fuel or from thermal energy, or an electrical substation. The source(s) may include one or more distributed energy resources, such as, for example, a solar energy system that includes an array of photovoltaic (PV) devices that convert sunlight into electricity or a wind-based energy system. More than one power source may supply electricity to the distribution system 101, and more than one type of power source may supply electricity to distribution system 101.

[0073] The load 103 is any type of device or system that utilizes electricity and may include electrical equipment that receives and transfers or distributes electricity to other equipment in the distribution system 101. The load 103 may include, for example, transformers, switchgear, energy storage systems, computer and communication equipment, lighting, heating and air conditioning, motors and electrical machinery in a manufacturing facility, and / or electrical appliances and systems in a residential building.

[0074] The current interrupter 120 is any type of device capable of interrupting the supply of electricity to the load 103. The current interrupter 120 may be rated for voltages between, for example, 15 kV and 38 kV, between 15 kV and 30 kV, or for voltages greater than 15 kV. Additional example voltage ratings for the current interrupter 120 include 15 kV, 15.5 kV, 25 kV, 27 kV, 29 kV, 29.2 kV, 35 kV, and 38 kV. These voltage ratings are provided as examples and the current interrupter 120 may have a different voltage rating. The current interrupter 120 may be rated for continuous current of, for example, between 5 amperes (A) and 1200 A, 630 A, 800 A, 1200A, or greater. The current interrupter 120 may be capable of interrupting fault currents of, for example, 200 A to 20 kA, 12.5 kA, or 16 kA.

[0075] The current interrupter 120 may be, for example, a switch that is capable of opening and closing repeatedly, such as a vacuum interrupter, oil interrupter, air interrupter, a sulfur hexafluoride (SFe) interrupter, or a solid state device. Other types of devices that are capable of interrupting and conducting current but are not necessarily capable of opening and closing repeatedly, such as a fuse, may be used as the current interrupter 120. In implementations in which the current interrupter 120 is a vacuum interrupter or other switch that is capable of opening and closing repeatedly, the switching apparatus 110 may be a recloser and may be a single-phase or three-phase recloser. If a three-phase recloser, three switching apparatus 110 may be used and may be operated independently or ganged, and may have separate or combined user interfaces 130.

[0076] In addition to the current interrupter 120, the switching apparatus 110 also includes various components 140 that are associated with the operation and / or monitoring of the current interrupter 120. Although shown as a single block, the various components 140 may include more than one component or subsystem. The various components 140 may include, for example, electronic controls, actuators, communication devices, and / or sensors. The sensors may be used to sense current, voltage, power flow, temperature, or other states of the switching apparatus 110. The various components 140 are not necessarily located in one part of the switching apparatus 110.

[0077] The user interface 130 allows manual control and / or monitoring of the current interrupter 120 and / or one or more of the various components 140. The user interface 130 is intended to be used by a human operator. The user interface 130 may include, for example, a handle that allows manual operation of the current interrupter 120 and / or a perceivable indicator that provides the status of the current interrupter 120. The user interface 130 also may include a mounting assembly that is used to attach the switching apparatus 110 to a utility pole or other structure. The user interface 130 may include an electronic control that may either be integrated in the switching apparatus 110 or may be separately coupled via cable or wireless signal to the switching apparatus 110. FIGS. 2A and 2B are a perspective view of an impedance assembly 250 in an unassembled state. FIG. 2C is a perspective view of the impedance assembly 250 in an assembled state. The impedance assembly 250 may be used in the voltage sensor system 190 (FIG. 1 A). The impedance assembly 250 includes a linear impedance 252, a reinforcing structure 270 (which is formed from a layer 274), and connection fittings 258 and 259. The linear impedance 252 may be a linear resistor.

[0078] The linear impedance 252 has a body 253. In the example shown, the body 253 is substantially cylindrical. However, the body 253 may have other shapes. For example, the body 253 may have a square or rectangular cross-section.

[0079] The body 253 has an exterior sidewall surface 255 that extends in the Z direction from an end 256 to an end 257. The body 253 may be made of any material that provides an impedance suitable for the application. The linear impedance 252 may be a linear resistance with a resistance of, for example, 100 to 200 megaohms (M ) and the body 253 may be ceramic. The linear impedance 252 also includes one or more electrically conductive traces 251 that are on the exterior sidewall surface 255. The electrically conductive traces 251 may be, for example, silver or copper.

[0080] Regardless of the specific configuration of the linear impedance 252, the impedance of the linear impedance 252 remains constant over the range of voltages and currents expected to be encountered during use of the impedance assembly 250.

[0081] The body 253 also includes electrically conductive elements 242, 246 at the respective ends 256, 257. Each electrically conductive element 242, 246 may be, for example, an endcap, a metallic coating, or a metal disk. The electrically conductive elements 242, 246 are in electrical contact with the electrically conductive traces 251 on the exterior sidewall surface 255 of the body 253. The electrically conductive elements 242, 246 may be used to facilitate electrical connection between the linear impedance 252 and an external element. The impedance assembly 250 may be made without the electrically conductive elements 242, 246.

[0082] The connection fitting 258 is mounted onto the end 256, and the connection fitting 259 is mounted onto the end 257. Each connection fitting 258, 259 is any element capable of providing a mechanical and electrical connection between the body 253 and an external component. Each connection fitting 258, 259 is a hollow structure with a respective opening 261, 262 through which an electrical connection to the body 253 can be made. For example, each connection fitting 258, 259 may be a tube.

[0083] The connection fitting 258, 259 may be mounted onto the respective end 256, 257 and / or the respective electrically conductive element 242, 246 in any manner. For example, the connection fittings 258, 259 may be attached to the respective electrically conductive elements 242, 246 by a threaded connection or with an adhesive. Moreover, the connection fittings 258, 259 are not necessarily hollow structures. For example, each connection fitting 258, 259 may be a solid electrically conductive bar or electrically conductive post that attaches to threads on each end 256, 257 or that is attached to each end 256, 257 by an adhesive or fastener (such as a screw).

[0084] FIG. 2B shows a perspective view of the layer 274, which is formed into the reinforcing structure 270. In the example of FIG. 2B, the layer 274 is a pre-formed sheet that includes strands 271 of an insulating material in a woven pattern embedded in a base 272. The base 272 is any electrically insulating material that is capable of being bent, curved, wrapped, coiled, or shaped without breaking. The base 272 may be, for example, a resin, an epoxy, or a polymer material. The layer 274 may have a form other than a sheet. For example, layer 274 may be a strip, tape, ribbon, or wet-wound fiber that has an extent in the Z direction that is less than the extent of the body 253. The layer 274 may include more than one pre-formed piece. For example, the layer 274 may be a collection of sheets and / or a collection of strips that are all applied to the exterior sidewall surface 255 to form the reinforcing structure 270.

[0085] To assemble the impedance assembly 250, the layer 274 is placed on the exterior sidewall surface 255 and may be placed on a portion of an exterior of the connection fitting 258 and a portion of an exterior of the connection fitting 259. The layer 274 is applied directly to and is in direct contact with the exterior sidewall surface 255 of the impedance assembly 250 and with portions of the exterior of the fittings 258 and 259. The layer 274 is a pre-formed material that can be shaped and wrapped around or otherwise applied to the exterior sidewall surface 255. Although the layer 274 may include materials that melt or flow when heated, the layer 274 is applied to the exterior sidewall surface 255 as a flexible but solid material. Applying the layer 274 is different than and may be simpler than applying, for example, a liquid coating to the exterior sidewall surface 255. After placing the layer 274 on the exterior sidewall surface 255, the layer 274 is processed to form the reinforcing structure 270. The layer 274 may be processed by being exposed to chemical, thermal, ultraviolet (UV) radiation, and / or a curing process to create the reinforcing structure 270 that is adhered or bonded to the exterior sidewall surface 255. There are no voids, or substantially no voids, between the reinforcing structure 270 and the exterior sidewall surface 255. The layer 274 may also bond to the traces 251 (if traces are on the surface 255). Moreover, the reinforcing structure 270 is able to transfer mechanical loads between the fitting 258 and the fitting 259 such that these loads are not transferred through the body 253. Thus, the reinforcing structure 270 improves the structural strength of the impedance assembly 250. When the linear impedance 252 is manufactured, it has a known impedance value. The reinforcing structure 270 prevents or mitigates unexpected changes to that known impedance value that could otherwise occur due to mechanical stress and loading on the linear impedance 252.

[0086] FIG. 3 A is a perspective exterior view of an impedance assembly 350. FIG. 3B is a cross-sectional view of the impedance assembly 350. The impedance assembly 350 is another example of an impedance assembly that may be used in the voltage sensor system 190 of FIG. 1A.

[0087] The impedance assembly 350 includes a linear impedance 352 that has a body 353 and an exterior sidewall 355. The linear impedance 352 may be a linear resistor. The linear impedance 352 includes electrically conductive traces on the sidewall 355. The conductive traces may be covered or coated with an insulating material such as glass or rubber. The body 353 extends in the Z direction from a first end 356 to a second end 357. An electrically conductive endcap 342 is on the first end 356, and an electrically conductive endcap 346 is on the second end 357. The electrically conductive endcaps 342, 346 are in electrical contact with the conductive traces on the sidewall 355. The electrically conductive endcap 342 defines a threaded recess 398, and the electrically conductive endcap 346 defines a threaded recess 399. The impedance assembly 350 also includes first and second connection fittings 358, 359 that are used to mechanically and electrically connect the impedance assembly 350 to one or more external components.

[0088] Referring also to FIG. 3C, which is a detailed view of the inset labeled C in FIG. 3B, the first connection fitting 358 is a tube that extends in the Z direction from a tube end 366a to a tube end 366b. The connection fitting 358 may be a metal tube. The connection fitting 358 also includes an open interior region 361 defined by an interior surface 369. The connection fitting 358 includes exterior threads 363 at the tube end 366a and may have a smooth exterior (no exterior threads) at the tube end 366b. In another example, the tube end 366b may have a nonsmooth exterior surface, such as a roughened, sandblasted, or knurled exterior surface.

[0089] Moreover, in some implementations, the tube end 366a does not include the external threads 363.

[0090] In the example shown, the first connection fitting 358 includes the open interior region 361, but the first connection fitting 358 may be implemented without the open interior region 361. For example, a solid connector that lacks an open interior region but includes the exterior threads 363 may be attached to the end 356 of the linear impedance 352. In another example, instead of the first connection fitting 358 being hollow throughout its length in the Z direction, the first connection fitting 358 may have an interior female thread that attaches to a corresponding male threaded element on the end 356. In yet another example, both tube ends 366a and 366b may be blind holes, with the tube end 366b holding a pin that centers on the body 353 and the other tube end 366a having a thread that an electrical connection could connect to.

[0091] In the implementation of FIGS. 3A-3C, the tube end 366b of the first connection fitting 358 may include an externally threaded post, screw, or pin that connects to the threaded recess 398 to attach the first connection fitting 358 to the body 353. In some implementations, a separate screw is inserted into the open interior region 361 and threaded into the threaded recess 398 to attach the first connection fitting 358 to the body 353.

[0092] A washer 365 is between the endcap 342 (which is on the first end 356 of the linear impedance 352) and the tube end 366b of the first connection fitting 358. The washer 365 is a ring or an annulus that has a center opening 394 (FIG. 3C) through which the external threaded post of the first connection fitting 358 extends. The washer 365 is made of an electrically insulating material and isolates the linear impedance 352 from the first connection fitting 358. For example, the washer 365 may be made of PolyEtherEtherKetone (PEEK), Kapton tape, or ceramic. Thus, the washer 365 electrically isolates the first connection fitting 358 from the endcap 342 and the conductive traces that are on the sidewall 355 of the linear impedance 352. Because of the isolation provided by the washer 365, the endcap 342 and the first connection fitting 358 are electrically isolated from each other and may have separate voltages. Providing the electrical isolation between the linear impedance 352 and the fitting 358 may reduce noise and improve measurement accuracy. For example, the endcap 342 may be used to provide a voltage signal for measurement while the first connection fitting 358 is grounded for shielding.

[0093] A centering spacer 377 is in contact with the washer 365 and the interior surface 369 of the fitting 358. The centering spacer 377 is made of an electrically insulating material. The centering spacer 377 extends into the open interior region 361. The centering spacer 377 maintains concentricity of the first connection fitting 358 and the linear impedance 352, provides additional electrical isolation between the first connection fitting 358 and the linear impedance

[0094] 352, and bolsters the bending strength of a component that compresses the fitting 358 and the impedance 352 during assembly.

[0095] Although the centering spacer 377 and the washer 365 may improve the performance and manufacturability of the impedance assembly 350 and provide electrical isolation between the end 356 of the body 353 and the first connection fitting 358, the impedance assembly 350 may be manufactured and used without the washer 365 and / or without the centering spacer 377.

[0096] The second connection fitting 359 is a tube that extends in the Z direction from a tube end 367a to a tube end 367b and has an open interior region 362 defined by an interior surface 368. The connection fitting 359 includes exterior threads 364 at the tube end 367b. The second connection fitting 359 is attached to the endcap 346, which is on the second end 357 of the body

[0097] 353. The endcap 346 includes the threaded recess 399, which receives a threaded post or pin on the tube end 367a of the second connection fitting 359 to connect the second connection fitting 359 to the linear impedance 352.

[0098] Although in the example discussed in FIGS. 3A-3C, the first and second ends 356 and 357 are covered with the respective endcaps 342 and 346, other implementations are possible. For example, if electrical isolation is not used between the endcap 342 and the connection fitting 358, the endcap 342 and the connection fitting 358 may be combined as a single element. In these implementations, the connection fitting 358 is electrically connected to the traces on the sidewall 355 of the body 353.

[0099] Returning to FIG. 3B, the open interior region 362 provides an electrical connection point to connect to the endcap 346 and to the linear impedance 352. For example, the open interior region 362 provides a passageway through which an electrical connection (for example, a wire or metal bar) may pass and be electrically connected to the endcap 346. The exterior threads 364 may be used to mechanically mount the impedance assembly 350 to a separate structure. The connection fitting 359 provides an alternative to directly mounting the linear impedance 352 to the separate structure. Moreover, using the connection fitting 359 to attach the linear impedance 352 to the separate structure instead of directly mounting the linear impedance 352 to the separate structure reduces the mechanical load on the linear impedance 352 and increases the overall accuracy of a voltage sensor that includes the impedance assembly 350.

[0100] Similarly, the open interior region 361 provides an opening for an electrical connection to the endcap 342 (and the linear impedance 352), and the threads 363 provide a mounting point for the impedance assembly 350. Moreover, this arrangement allows mechanical loads on the connection fitting 358 (or connection fitting 359) to transfer to the reinforcing structure 270 and to be transmitted through the reinforcing structure 270 to the opposite connection fitting 359 (or the connection fitting 358). This allows mechanical loads go through reinforcing structure 270 and not through the body 253.

[0101] The reinforcing structure 270 is wrapped around the sidewall 355 of the linear impedance 352 and around a portion of the exterior surface of the fittings 358, 359. The reinforcing structure 270 makes direct contact with the sidewall 355 and any exposed conductive traces on the sidewall 355. The reinforcing structure 270 provides mechanical strength and electrical isolation to the fittings 358, 359 and the linear impedance 352. For example, the reinforcing structure 270 helps to hold the fittings 358, 359 to the linear impedance 352 and also helps maintain integrity of the body 353.

[0102] The reinforcing structure 270 is not applied to the exterior threads 363 and 364 and does not cover the open interior regions 361 and 362. Thus, the reinforcing structure 270 does not prevent the impedance assembly 350 from being attached to one or more external structures and electrically connected to a current path that includes components external to the impedance assembly 350. During manufacture of the impedance assembly 350, end protectors may be attached to the threads 363 and 364 to protect the threads 363 and 364 and the open interior regions 361 and 362.

[0103] FIG. 3D is a cross-sectional view of an impedance device 395 that includes the impedance assembly 350 and a housing 380. The housing 380 is made of an insulating material. For example, the housing 380 may be a solid dielectric insulation. The housing 380 encloses most, but not all of the impedance assembly 350. For example, and as shown in FIG. 3D, the housing 380 surrounds and is in contact with the wrapped linear impedance 352 and the nonthreaded portions of the fittings 358, 359 near respective ends 366b, 367a. However, some or all of the threads 363, 364 are accessible from outside of the housing 380. Additional components may be attached to or placed over the threads 363 and / or the threads 364. Moreover, the open interior regions 361 and 362 are not blocked by the housing 380 or the reinforcing structure 270 and remain available to make electrical connections between the linear impedance 352 and one or more external devices or current paths. The housing 380 may be formed by overmolding or the housing 380 may be a stuffed housing.

[0104] FIGS. 4A-4C relate to an impedance apparatus 492 that includes the impedance assembly 350. FIG. 4A is a cross-sectional view of the impedance apparatus 492. FIG. 4B is a cross- sectional view of an impedance device 495 that includes the impedance apparatus 492 and a housing 480, with the impedance device 495 attached to a busbar 478. FIG. 4C is a perspective exterior view of the impedance device 495 attached to the busbar 478.

[0105] Referring to FIG. 4A, the impedance apparatus 492 includes a bus coupler 475 that is threaded onto the threads 364 of the second connection fitting 359. The bus coupler 475 includes an opening 476 that is concentric with the open interior region 362 of the second connection fitting 359. Thus, when the bus coupler 475 is attached to the impedance assembly 350, a wire, screw, bolt, or other electrically conductive element may be passed though the opening 476 and the open interior region 362 and electrically connected to the endcap 346 to thereby connect the electrically conductive element to the linear impedance 352. Although the bus coupler 475 is shown with the opening 476, the bus coupler 476 may be implemented without the opening 476.

[0106] The bus coupler 475 may be attached to the threads 364 before the linear impedance 352 and the fittings 358, 359 are wrapped with the reinforcing structure 270. Thus, the bus coupler 475 also may act as an end protector that protects the threads 364 during manufacture of the impedance assembly 350.

[0107] Referring also to FIGS. 4B and 4C, the bus coupler 475 provides an anti-rotation electromechanical connection between the busbar 478 and the linear impedance 352. The bus coupler 475 is attached to the busbar 478 with fasteners 421 and 422. The fasteners 421 and 422 are on opposites sides of the opening 476 and thus prevent the impedance device 495 from rotating about the Z axis. The fasteners 421 and 422 may be, for example, screws, bolts, or posts.

[0108] Referring again to FIG. 4A, the impedance apparatus 492 also includes a shield electrode 433 and an insulating adaptor 432. A threaded adaptor opening 434 passes through the insulating adaptor 432 in the Z direction. The impedance assembly 350 is attached to the insulating adaptor 432 by threading the external threads 363 on the fitting 358 onto the threads in the adaptor opening 434. After the impedance assembly 350 is attached to the insulating adaptor 432, the open interior region 361 remains accessible from a bottom 435 of the adaptor 432.

[0109] The insulating adaptor 432 is made of an electrically insulating material that can withstand high temperatures and has a high mechanical strength. Examples of materials that may be used for the insulating adaptor 432 include, without limitation, high-strength polymers, thermoset materials, thermoplastic materials, a glass-filled phenolic, PEEK, PolyArylEtherKetones (PAEK), and polyester bulk molding compounds (BMC).

[0110] The insulating adaptor 432 is concentrically received in a base region 436 of the shield electrode 433. The insulating adaptor 432 may be held in the shield electrode 433 with a press fit or interference fit. The shield electrode 433 includes a sidewall 437 that extends in the Z direction from the base region 436 and surrounds the first connection fitting 358 and a lower portion of the impedance assembly 350. The base region 436 is circular in the X-Y plane, and the sidewall 437 is substantially cylindrical. The sidewall 437 defines a cup region 447 and includes one or more openings 438 that pass through the sidewall 437. The shield electrode 433 may be a single piece or may be made of more than one piece. In implementations in which the shield electrode 433 is made from more than one piece (such as the implementation shown in FIG. 4A), a flange of the insulating adaptor 432 is captured or pinched by two pieces to hold the adaptor 432 to the shield electrode 433. The shield electrode 433 is made of an electrically conductive material such as, for example, aluminum, copper, brass, bronze, stainless steel, or other metal alloys.

[0111] Other implementations are possible. For example, in some implementations, the insulating adaptor 432 is attached to the shield electrode 433 by attaching threads on an exterior of the insulating adaptor 432 to corresponding threads on the shield electrode 433.

[0112] In operational use of the impedance apparatus 492, the shield electrode 433 provides shielding and reduces signal noise by coupling capacitive cross-talk to electrical ground rather than to the sensor output, thus improving the accuracy of a voltage sensor that includes the impedance apparatus 492. The insulating adaptor 432 mechanically couples the shield electrode 433 (which may be grounded) to the impedance assembly 350 (which is at a relatively low voltage) while electrically isolating the shield electrode 433 and the impedance assembly 350 from each other.

[0113] The shield electrode 433 also includes an extension tube 439 that defines a passageway 441. The extension tube 439 and the passageway 441 extend from the base region 436 in the -Z direction. The shield electrode 433 and the extension tube 439 may be a single piece or may be separate elements that are joined together. The passageway 441 is aligned with the adaptor opening 434 and the open interior region 361 in the impedance assembly 350. Thus, a wire or other electrically conductive element may pass through the passageway 441 and the open interior region 361 from the exterior of the impedance apparatus 492 to electrically connect to the endcap 342. In this way, the linear impedance 352 may be electrically connected to an external electrical device. Moreover, the extension tube 439 provides a capacitive / ground shield for an electrically conductive element in the passageway 441.

[0114] Referring again to FIGS. 4B and 4C, the housing 480 is made of a solid dielectric insulation that is over-molded onto the impedance apparatus 492. The over-molded housing 480 may be silicone rubber, Ethylene Propylene Diene Monomer (EPDM), or epoxy (for example, cycloaliphatic epoxy if used in outdoor applications or bisphenol A epoxy if used indoors).

[0115] During the over-molding process, the solid dielectric insulation adheres to the reinforcing structure 270, the shield electrode 433, and the bus coupler 475. The solid dielectric insulation also flows into the cup region 447 of the shield electrode 433 through the openings 438 and surrounds the lower portion of the impedance assembly 350. The openings 438 allow the dielectric insulation to flow into and fill the cup region 447 and allow air to escape from the cup region 447 while the dielectric insulation fills the cup region 447. The housing 480 includes sheds 481 to increase creep distance. The housing 480 may be rated for outdoor use.

[0116] The housing 480 does not completely enclose the bus coupler 475 and does not block the passageway 441 or the opening 476. Furthermore, at least part of the outer diameter of the extension tube 439 is not encased in the housing 480. Thus, the extension tube 439 may be used for mounting the sensor. The extension tube 439 is made of an electrically conductive material, such as, for example, aluminum, stainless steel, or a semiconductive polymer. The extension tube 439 provides additional space for additional mechanical connections, longer ground shielding, and longer creep distance allowance. The extension tube 439 also may be used to mount the impedance device 495 to the switching apparatus 110 or otherwise locate the impedance device 495 in space.

[0117] Thus, the impedance apparatus 492 with the housing 480 may be electrically and mechanically connected to external structures and devices. For example, the busbar 478 may be mounted to a load-side terminal (such as the terminal 105 of FIG. 1A).

[0118] FIG. 5 A is a partial cross-sectional view of an impedance device 595. The device 595 includes a rigid and electrically conductive shield electrode 533 and a solid dielectric housing 580. The housing 580 is another example of an overmolded housing. FIG. 5B is a cross- sectional perspective view of the shield electrode 533.

[0119] Referring to FIG. 5B, the shield electrode 533 extends in the Z direction from an end 549a to an end 549b. The end 549b is rounded and lacks sharp edges to reduce electrical stress on the housing 580 (FIG. 5A). The shield electrode 533 includes a base portion 536 at the end 549a, and a sidewall 537 that extends in the Z direction from the base portion 536. The base portion 536 includes a threaded bore 544 that extends in the Z direction from the end 549a to a shelf 545. The bore 544 is concentric with the sidewall 537. The shield electrode 533 has an open area above the bore 544 that is defined by an inner side 543 of the sidewall 537. The shield electrode 533 may be made of any electrically conductive material, such as, for example, aluminum, copper, brass, bronze, stainless steel, or other metal alloys.

[0120] Referring to FIG. 5 A, the threaded bore 544 is attached to the threads 363 of the fitting 358 to attach the shield electrode 533 to the impedance assembly 350. The shield electrode 533 is concentric with the body 353 and the fitting 358. The shield 533 is threaded onto the threads 363 of the fitting 358. The shield 533 and the fitting 358 are electrically conductive. Thus, the shield 533 is electrically connected to the fitting 358. During operational use, the first connection fitting 358 provides a ground for the shield 533.

[0121] In the example shown in FIG. 5A, the shelf 545 is flush with an end 583 of the housing 580. However, other implementations are possible and the shield 533 may be oriented such that the shelf 545 is not flush with the end 583. The sidewall 537 surrounds the non-threaded portion of the fitting 358 and the lower portions of the body 353 and the reinforcing structure 270. The threads 363 extend farther along the Z direction than the threaded bore 544. Thus, when the shield 533 is attached to the threads 363, the open interior region 361 and the threads near the open interior region 361 (and the tube end 366a) extend in the -Z direction from the base portion 536 of the shield electrode 523. This allows the open interior region 361 to be used to electrically connect the impedance device 595 to an external current path and for the threads 363 to be used to mechanically connect the lower portion of the device 595 to an external structure.

[0122] The housing 580 is in contact with the sidewall 537, the inner side 543 of the sidewall 537, and the reinforcing structure 270. The solid dielectric housing 580 also fills the cylindrical space between the inner side 543, the reinforcing structure 270, and the non-threaded portion of the fitting 358. The reinforcing structure 270 is between the non-threaded portion of the fitting 358 and the housing 580.

[0123] The impedance devices 495 and 595 are examples of devices that have an over-molded housing. FIGS. 6A, 6B, and 7 show impedance devices that have a stuffed housing.

[0124] FIG. 6A is a cross-sectional view of a stuffed housing 680 prior to receiving a impedance assembly. FIG. 6B is a perspective view of a mold core 697. FIG. 6C is a cross-sectional view of an impedance device 695. The device 695 may be used as the device 195 in the voltage sensor system 190 of FIG. 1A.

[0125] The housing 680 is made of a stretchable insulating material such as, for example, silicone rubber or EPDM. To form the housing 680, the insulating material is molded around the mold core 697. The mold core 697 is separated from the insulating material, creating a passageway 685 where the mold core 697 was. The mold core 697 has similar but smaller dimensions than the impedance assembly 350 such that the passageway 685 has a diameter that is smaller than the impedance assembly 350.

[0126] The housing 680 also includes an electrically conductive or semiconductive shield electrode 633 that is molded into the housing 680. Because the electrode 633 is molded into the housing 680, the electrode 633 does not require additional assembly at a later point. Although the housing 680 is shown as including the shield electrode 633, the shield electrode 633 is optional and the housing 680 may lack the shield electrode 633.

[0127] To assemble the impedance device 695, the impedance assembly 350 is pushed or stuffed into an end 683 of the passageway 685 and the housing 680 is stretched to accommodate the impedance assembly 350. The housing 680 and the impedance assembly 350 are held together as the housing 680 is allowed to shrink or relax around the impedance assembly 350, thereby forming the impedance device 695.

[0128] Referring to FIG. 6C, the device 695 includes the impedance assembly 350 and the housing 680. The threads 363, 364 of the respective fittings 358, 359 extend from the housing 680 such that the impedance device 695 may be electrically and mechanically mounted to external structures and to an external current path. An inset 696 shows the shield electrode 633 and the fitting 358 in more detail.

[0129] The shield electrode 633 (shown in grey solid shading) has a sidewall 637 that extends in the Z direction from an end 636a to an end 636b. The sidewall 637 is a cylinder, annulus, or ring with an open interior region that is defined by an inner side 643 of the sidewall 637. The shield electrode 633 is concentric with the wrapped linear impedance 352 and the fitting 358.

[0130] The inner side 643 of the shield electrode 633 surrounds the reinforcing structure 270 and the non-threaded exterior side portion of the fitting 358. The shield electrode 633 touches the connection fitting 358 but is isolated from the voltages along the surface of the linear impedance 352. The shield electrode 633 may be isolated from voltages in the conductive trace(s) on the sidewall 355 of the linear resistor 352 by the reinforcing structure 270. The shield electrode 633 does not directly touch the sidewall 355 of the linear impedance 352. Additionally, there may be an electrically insulating material, such as silicone rubber, room-temperature-vulcanizing (RTV) silicone, or silicone grease, between the shield electrode 633 and the reinforcing structure 270.

[0131] The shield electrode 633 is made of any electrically conductive and non-rigid, compliant, and / or stretchable material. For example, the shield electrode 633 may be made of a semiconductive material that is not rigid and has some flexibility. Specific examples of materials that may be used for the shield electrode 633 include semiconductive elastomers, such as, for example, a carbon-filled silicone rubber or EPDM, or a metallic coating that is not rigid. The shield electrode 633 (which may be grounded during operational use of the impedance device 695) provides capacitive shielding, thereby reducing noise and improving the accuracy of a voltage sensor that includes the impedance device 695.

[0132] FIG. 7 is a cross-sectional view of an impedance device 795. The impedance device 795 includes a stuffed housing 780 and the impedance assembly 350. The housing 780 is made from an electrically insulating material that is flexible and capable of stretching. The insulating material may be, for example, silicone rubber or EPDM. A shield electrode 733 made of a non-rigid material that can conduct electricity is embedded in the insulating material. The shield electrode 733 may be made of a semi- conductive material, such as, for example, a semi-conductive elastomer. Examples of a semi- conductive elastomer include carbon-filled silicone rubber or EPDM.

[0133] The housing 780 is formed by molding the insulating material over a mold core (such as the mold core 697). The mold core is removed to form an opening or passage that has slightly smaller dimensions than the impedance assembly 350. The impedance assembly 350 is then stuffed into the opening and the housing 780 is stretched over the impedance assembly 350 until the impedance assembly 350 is encased in the housing 780. After the impedance assembly 350 is stuffed into the housing 780, the shield electrode 733 is in electrical contact with the fitting 358.

[0134] Unlike the shield electrode 633, which is in contact with the reinforcing structure 270, the shield electrode 733 includes a bottom 735 (which is shown as a tapered conical shape but does not need to be), and sidewall 737 with an inner side 743 that does not touch the reinforcing structure 270. The space between inner side 743 and reinforcing structure 270 is filled with the solid dielectric insulating material of the housing 780. Separating the inner side 743 from reinforcing structure 270 reduces an electrical stress inside housing 780 and increases electrical performance. Although the shield electrode 733 offers increased electrical performance, the shield electrode 733 is optional and the impedance device 795 may be implemented without the shield electrode 733.

[0135] FIG. 8 is a flow chart of a process 800. The process 800 is an example of a process for manufacturing or assembling a linear impedance device that may be used in the voltage sensor system 190 (FIG. 1A). The process 800 is discussed with respect to FIGS. 3A-3D to provide an example.

[0136] The fitting 358 is coupled to the end 356 of the linear impedance 352, and the fitting 359 is coupled to the end 357 of the linear impedance 352 (810). The fitting 358 may be coupled to the end 356 by first placing the washer 365 on the end 356 and then placing the centering spacer 377 and fitting 358 on the washer 365. The fitting 359 is press fit directly to the end 357.

[0137] In some implementations, the washer 365 and the centering spacer 377 are not used. In these implementations, the fitting 358 is attached directly to the endcap 342 or directly to the end 356 of the body 353. The fittings 358 and 359 may be coupled to the impedance 352 in other ways. For example, in some implementations, the linear impedance 352 is a pre-made or pre-formed cylindrical ceramic body with electrically conductive traces on the sidewall 355. The endcaps 342 and 346 are electrically connected to the conductive traces. In these implementations, the fitting 358 is attached to the threaded recess 398 of the endcap 342, and the fitting 359 is attached to the threaded recess 399 of the endcap 346 with a second screw. If the insulating washer 365 is used, the washer 365 is placed on the endcap 342 before the fitting 358 is attached to the threaded recess 398. The washer 365 is between the endcap 342 and the fitting 358, and the centering spacer 377 extends through the opening 394 of the washer 365. The threads 363 on the fitting 358 may be covered with a first thread protector, and the threads 364 on the fitting 359 may be covered with a second thread protector.

[0138] The impedance assembly 350 is prepared (820). The impedance assembly 350 is prepared by attaching the layer 274 (FIG. 2B) to the sidewall 355, the tube end 366b of the fitting 358, and the tube end 367a of the fitting 359. The layer 274 may be attached by winding the layer 274 about the body 353 and the fittings 358 and 359. The layer 274 may be applied in a coiled-like manner. In some implementations, the layer 274 may include strips or sheets that are applied to the sidewall 355 in the Z direction instead of or in addition to being wound about the body 353.

[0139] The layer 274 may be heated shortly before applying the layer 274 to the sidewall 355 and / or the layer 274 may be heated while it is in contact with the sidewall 355. Heating the layer 274 may make the layer 274 more flexible and easier to wrap. Furthermore, the layer 274 may include adhesive agents and compounds that flow or become sticky when heated and are more likely to bond with the sidewall 355 and the non-threaded portions of the fittings 358 and 359. The threads 363 and 364 and / or the open interior regions 361 and 362 may be covered with protectors to prevent the layer 274 from covering the threads 363 and 364 or the open interior regions 361 and 362.

[0140] The layer 274 is allowed to harden or is cured to become the reinforcing structure 270. For example, the layer 274 may be subjected to chemical, thermal, ultraviolet (UV) radiation, or another curing process to create the reinforcing structure 270. In some implementations, the layer 274 is hardened by simply allowing the layer 274 to cool. The curing or hardening process bonds the layer 274 to the sidewall 355 such that there are no voids, or substantially no voids, between the reinforcing structure 270 and the sidewall 355. The thread protectors (if used) are removed after the layer 274 is placed on the sidewall 355 and after the layer 274 hardens or cures into the reinforcing structure 270.

[0141] The impedance assembly 350 is installed in the insulating housing 380 (830). The insulating housing 380 may be over-molded or stuffed.

[0142] For implementations in which the insulating housing 380 is over-molded, the impedance assembly 350 is placed in a mold and solid dielectric insulation in a flowable or moldable form is placed in the mold around the impedance assembly 350 with the fittings 358 and 359 at least partially exposed and / or covered with protectors or functional elements (for example, a bus coupler or a shield electrode) to prevent adherence to the dielectric insulation. The solid dielectric insulation is allowed to cure and the housing 380 is formed.

[0143] For implementations in which the insulating housing 380 is a stuffed housing, a mold core (such as the mold core 697 of FIG. 6B) that has spatial dimensions that are similar but smaller than the spatial dimensions of the impedance assembly 350 is provided. A flexible insulating material is placed or molded around the mold core. The mold core is separated from the insulating material, leaving a passage or opening (such as the passageway 685 of FIG. 6B) in the insulating material and forming the housing 380. The housing 380 is in a relaxed state after formation.

[0144] To install the impedance assembly 350 in the housing 380, the impedance assembly 350 is inserted into the passage or opening and / or the housing 380 is stretched around the impedance assembly 350. The housing 380 is in a stretched state during the insertion of the impedance assembly 350. The housing 380 partially relaxes after the impedance assembly 350 is inserted such that the impedance 350 is held securely in the housing 380. The installation of the impedance assembly 350 into the housing 380 may or may not include the formation of the housing 380. In other words, the housing 380 may be pre-formed or pre-prepared and provided in a state that is ready to receive the impedance assembly 350, or the housing 380 may be formed from a bulk dielectric material using the mold core as discussed above as part of installing the impedance assembly 350 in the housing. Moreover, the housing 380 may or may not include a shield electrode molded into the insulating material used for the housing 380. The shield electrodes 633 and 733 discussed above are examples of a shield electrode that may be molded into the housing 380. These and other implementations are within the scope of the claims.

Claims

WHAT IS CLAIMED IS:

1. A system comprising: a current interrupter comprising: a first terminal; a second terminal; and a switching apparatus between the first terminal and the second terminal; and an impedance assembly configured to sense a voltage at one or more of the first terminal and the second terminal, the impedance assembly comprising: a linear impedance; and a reinforcing structure on an exterior surface of the linear impedance, wherein the reinforcing structure comprises an electrically insulating material wrapped around the linear impedance.

2. The system of claim 1, wherein the first terminal is a source-side terminal, the second terminal is a load-side terminal, and the impedance assembly is configured to sense a voltage at the load-side terminal.

3. The system of claim 1, wherein the first terminal is a source-side terminal, the second terminal is a load-side terminal, and the impedance assembly is configured to sense a voltage at the source-side terminal.

4. The system of claim 1, wherein the linear impedance comprises a linear resistor, and the reinforcing structure is on an exterior surface of the linear resistor.

5. The system of claim 4, wherein the linear resistor comprises a ceramic body and one or more electrically conductive traces on an exterior of the ceramic body.

6. The system of claim 1, wherein the impedance assembly further comprises a solid dielectric housing on the reinforcing structure.

7. The system of claim 6, wherein the solid dielectric housing comprises an overmolded solid dielectric structure.

8. The system of claim 6, wherein the solid dielectric housing comprises a stuffed housing.

9. The system of claim 1, wherein the impedance assembly further comprises a first fitting configured to provide an electrical and mechanical connection to a first end of the linear impedance, and a second fitting configured to provide an electrical and mechanical connection to a second end of the linear impedance.

10. The system of claim 1, wherein the reinforcing structure comprises fiberglass and resin.

11. The system of claim 1, wherein the reinforcing structure comprises a sheet of woven electrically insulating fibers.

12. The system of claim 1, wherein the reinforcing structure comprises one or more of a sheet, tape, and fabric that comprises one or more fibers.

13. The system of claim 1, wherein the reinforcing structure is wound about the exterior surface of the linear impedance in a helix.

14. The system of claim 1, wherein the first terminal is a load-side terminal, the second terminal is a source-side terminal, the linear impedance is a linear resistor, and the current interrupter further comprises: a housing that extends from a first end to a second end, wherein the housing encloses the current interrupter, and the load-side terminal is at the first end of the housing; and a tank coupled to the second end of the housing; and the impedance assembly is electrically connected between the load-side terminal and the tank; and wherein the system further comprises a voltage sensor configured to produce an indication of the electrical current that flows in the linear resistor.

15. The system of claim 14, wherein the voltage sensor is embedded in the housing that encloses the current interrupter.

16. The system of claim 1, further comprising a voltage sensor, and wherein the voltage sensor is in an operating rod of the current interrupter.

17. An apparatus comprising: a resistor assembly comprising: a linear resistor comprising a resistor body; a first fitting at a first end of the resistor assembly; a second fitting at a second end of the resistor assembly; and a reinforcing structure wrapped around the resistor body, wherein at least part of the reinforcing structure is directly on an exterior surface of the resistor body, an exterior of part of the first fitting, and an exterior of part of the second fitting.

18. The apparatus of claim 17, wherein the reinforcing structure is one or more of a sheet, tape, and a fabric that comprises fibers of an electrically insulating material.

19. The apparatus of claim 17, wherein the linear resistor is substantially cylindrical; the first fitting comprises a first tube; and the second fitting comprises a second tube.

20. The apparatus of claim 19, wherein the first tube comprises first exterior threads, and the second tube comprises second exterior threads.

21. The apparatus of claim 17, further comprising an electrically insulating housing on part of the resistor assembly; and wherein at least part of the first fitting extends from a first end of the electrically insulating housing, and at least part of the second fitting extends from a second end of the electrically insulating housing.

22. The apparatus of claim 17, further comprising an electrically conductive shield that at least partially surrounds a first end of the resistor body.

23. The apparatus of claim 22, wherein the electrically conductive shield is in contact with the first fitting.

24. The apparatus of claim 22, wherein the electrically conductive shield comprises a semiconductive layer.

25. The apparatus of claim 17, further comprising an insulating adaptor configured to mechanically couple a shield electrode to the first fitting and to electrical isolate the shield electrode and the linear resistor.

26. The apparatus of claim 17, wherein the first fitting provides a first mechanical and electrical connection interface for the resistor assembly, and the second fitting provides a second mechanical and electrical connection interface for the resistor assembly.

27. A method comprising: coupling a first connection point to a linear impedance; coupling a second connection point to the linear impedance; preparing a reinforced linear impedance by: wrapping the linear impedance with an electrically insulating layer, the electrically insulating layer comprising fibers of an electrically insulating material; and forming a reinforcing structure from the electrically insulating layer, the reinforcing structure being in direct contact with an exterior surface of the linear impedance; and installing the reinforced linear impedance in an electrically insulating housing with the first connection point and the second connection point extending from the electrically insulating housing, and the electrically insulating housing in contact with the reinforcing structure.

28. An impedance assembly configured to sense a voltage at one or more terminals of a current interrupter, the impedance assembly comprising:a linear impedance comprising: a body and at least one electrically conductive trace on an exterior surface of the body; a first electrically conductive endcap on a first end of the body and electrically connected to the at least one electrically conductive trace; a first fitting mechanically attached to the linear impedance, wherein the first fitting is electrically isolated from the linear impedance and comprises an access point for electrically connecting to the linear impedance; and a reinforcing structure on an exterior surface of the linear impedance and at least part of the first fitting, wherein the reinforcing structure comprises an electrically insulating material wrapped around the linear impedance and part of the first fitting.

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