Test point voltage sensor for high voltage separable connectors

A device to measure the voltage at a test point, also referred to as a test point voltage sensor, comprises a housing formed from a first material and a second material, wherein the first material comprises an insulating material and the second material comprises a conductive or semiconductive material. The housing includes an opening configured to cover a test point of a cable accessory. The device further includes a pressure pad, disposed in the housing, having a conductive mating surface configured to contact a test point of the basic insulation plug or end plug. The device further includes a low side capacitor embedded in the housing and electrically coupled to the conductive mating surface. The device further includes a signal wire electrically coupled to the low side capacitor.

This disclosure relates to sensors for high voltage and, in particular, relates to sensors for high voltage separable connectors which may provide a low voltage signal corresponding to a high voltage signal present in a separable connector.

BACKGROUND

As electrical power distribution becomes more complex through the advent of renewable energy, distributed generation, and the adoption of electric vehicles, intelligent electrical distribution and associated electrical sensing is becoming more useful and even necessary. Useful sensing may include voltage, current, and the time relationship between voltage and current at various locations within a power distribution network.

Traditionally, the power has been generated at a central location, and then distributed radially from the generation facility. As the development of the power grid matures, and more renewable energy is involved, the power flow in the distribution grid becomes less obvious, i.e., no longer simply flowing away from primary generation stations. Too, customers are becoming much more aware of power quality in regards voltage, harmonics, real/imaginary power magnitudes, etc.

Many existing relatively high voltage transformers and switchgears have a dedicated space for cable accessories, particularly in higher voltage applications (for example, 5 kV to 69 kV, or higher). Many of these transformers and switchgear are of a variety referred to in the power utility industry as dead-front. Dead-front means there are no exposed relatively high voltage surfaces in the connection between a power cable and the transformer or switchgear. Such cable accessory connections are sometimes referred to as elbows, T-bodies, or separable connectors.

Many cable accessories implement testpoints to provide a limited energy signal that could be transformed into a scaled fraction of the line voltage residing on the shielded and insulated conductor of the cable accessory. The historical use of these test points is for indication of the presence of line voltage at the transformer or switchgear.

The need to develop and provide voltage and current and power quality sensing at the distribution grid is increasing rapidly due to substantial change in the global power grid structure. With the advent of more power electronics which often incorporate high frequency switching in their power supplies, the injection of noise in the power grid is increasing. Because of these and other issues in the evolving grid, the need for sensing and sensors at the distribution level is increasing.

SUMMARY

In one embodiment of the present invention, a device for measuring the voltage at a test point, also referred to as a test point voltage sensor, comprises a housing formed from a first material and a second material, wherein the first material comprises an insulating material and the second material comprises a conductive or semiconductive material. The housing includes an opening configured to cover a test point of a cable accessory. The device further includes a pressure pad, disposed in the housing, having a conductive mating surface configured to contact a test point of the basic insulation plug or end plug. The device further includes a low side capacitor embedded in the housing and electrically coupled to the conductive mating surface. The device further includes a signal wire electrically coupled to the low side capacitor.

It is to be understood that both the foregoing general description and the following detailed description present embodiments of the subject matter of the present disclosure, and are intended to provide an overview or framework for understanding the nature and character of the subject matter of the present disclosure as it is claimed.

The disclosure may be more completely understood in consideration of the following detailed description of various embodiments of the disclosure and the accompanying drawings.

DETAILED DESCRIPTION

The present disclosure provides a device for measuring voltage at a test point, also referred to as a ‘test point voltage sensor’ (TPVS) that provides voltage and/or power quality sensing at a point of the distribution grid, such as at a separable connector. The test point voltage sensor can be installed and utilized at a point on the distribution grid without the need for a service technician/utility to take an outage. For example, an existing insulating plug cover can be removed from a separable connector, such as a T-body, using a hot stick, and TPVS may be installed on that same location using a hot stick, so that there is no power interruption. The test point voltage sensor is similar in shape to a standard T-body protective cap or cover on the insulation plug, but the TPVS cap or cover can electrically connect to the metallic hex feature on the insulating plug, reduce the voltage using a capacitive voltage divider within the TPVS cap, and using wires, can provide a periodic or continuous low voltage signal for grid measurement analysis. The output of the TPVS is a low voltage signal that is sufficient for an analytics system to sense the presence of voltage, sense the time/phase relationship of the voltage signal, provide information on faults (voltage spikes, drops), and with some calibration (whether automated or manual), may provide reasonably accurate voltage output to better measure the cable voltage. A voltage reading can be taken using the test point voltage sensor, while a current can be measured using an additional sensor, e.g., a Rogowski coil. Both voltage and current can be connected to a monitoring computer or an analytics unit, such as a sensor analytics unit.

The term “high voltage” as used herein means a voltage equal to or greater than a high voltage threshold. The high voltage threshold may be based on a standard, jurisdictional requirement, or end-user requirement that applies to the particular system being described. For example, high voltage may refer to operating at about the voltage rating defined in a standard, such as the Institute of Electrical and Electronics Engineers (IEEE) Standard 386 (2016) for separable insulated connector systems for power distribution systems rated 2.5 kV through 35 kV (classified as phase-to-phase root-mean-square, or rms), which is incorporated herein by reference for any and all purposes. Depending on the application, the high voltage threshold may be equal to or greater than about 2.5 kV, about 3 kV, about 5 kV, about 15 kV, about 25 kV, about 28 kV, about 35 kV, about 69 kV, or more (classified as phase-to-phase rms).

The term “low voltage” as used herein means a voltage that is less than the high voltage. Low voltage may be defined at or below a low voltage threshold. The low voltage threshold and the high voltage threshold may be the same threshold or a different threshold. A low voltage may be a fraction, or ratio less than 1, of a high voltage. The low voltage may be defined by a threshold fraction, or ratio (for example, less than or equal to about 1:100). Unless otherwise stated in the disclosure herein, low voltage is described using phase-to-ground rms.

The term “separable connector” as used herein means a connection or interface for a high voltage system that can be readily established or broken by engaging or separating the connection at an operating interface. Separable connectors may be fully insulated and shielded and used to terminate and insulate a power cable, insulate another electrical component, or connect an insulated power cable to electrical apparatus, other power cables, or both. Separable connectors may be connected to transformers or switchgears. Some separable connectors may be used for deadfront transformers and switchgears, which refers to having no exposed high voltage surfaces in the connector between a power cable and the transformer or switchgear in the power utility industry. Non-limiting examples of separable connectors include elbow separable insulated connectors and tee separable insulated connectors (for example, a T-Body).

The term “voltage rating” as used herein means a maximum voltage at which a connector is designed to operate. The voltage rating may be measured as the highest phase-to-ground voltage rms for single phase systems or may be measured as the highest phase-to-ground and phase-to-phase voltage rms for three-phase systems. However, any suitable type of voltage rating may be used to describe a maximum operational voltage. Unless otherwise stated in the disclosure herein, voltage rating refers to phase-to-ground rms.

The term “connection” as used herein means an interface, a connector, or other structure used to electrically or mechanically couple components together. For example, a connection may include a plug or socket, a wire, a cable, a conductor on a substrate, a piece of solder, a conductive via, or other similar electrical or mechanical coupling.

The terms “coupled” or “connected” refer to elements being attached to each other either directly (in direct contact with each other) or indirectly (having one or more elements between and attaching the two elements).

FIGS. 1A-1Cshow exploded schematic views of a test point voltage sensor to be deployed on a separable connector.FIG. 2shows a cross section view of a test point voltage sensor100installed on a basic insulation plug.FIG. 3shows a close up cross section view of an exemplary test point voltage sensor.FIG. 4shows a schematic diagram of the voltage divider circuit established when connecting a test point voltage sensor to a basic insulation plug installed on a separable connector located on the distribution grid.

As shown inFIG. 1A, a voltage measurement system100includes a test point voltage sensor (TPVS)150acan be installed on a high voltage separable connector, such as separable connector120a, that is deployed at a location on a power distribution grid. The separable connector120ain this example comprises a T-Body. In alternative embodiments, the TPVS can be installed on any suitable separable connector, such as an elbow separable insulated connector. The separable connector120amay include one, two, or more receptacles (for example, in a T-Body).

In the exemplary embodiment ofFIG. 1A, the TPVS150acan mate with an IEEE 600A T-body having a basic insulating plug (BIP), with a test point, inserted in a receptacle therein. As discussed below, the BIP130can be a conventional BIP or it can be a modified BIP, having one or more capacitors disposed therein. In further alternative aspects, the TPVS can be configured to be deployed for different voltage classes, IEC devices, etc., including a TPVS that may attach to an integrated test point of a 200A “elbow” or an integrated test point of a 600A T-body.

In another example, a TPVS can mate with an IEEE 600A T-body120aat an integrated test point140.

In another example, inFIG. 1B, a TPVS150bcan mate with an integrated test point140of a 200A “elbow”120b.

Referring back toFIG. 1A, separable connector120aincludes a receptacle122that receives a basic insulating plug (BIP) or end plug130. The BIP130includes a tapered insertion end134and a contact point132, such as a lug or hex head nut, on the other end of BIP130. The BIP130can comprise a conventional BIP, formed from an insulating resin or other insulating polymer, such as is widely commercially available. Alternatively, BIP or end plug130can be a modified end plug with one or more integrated discrete capacitors disposed therein.

In this aspect, the TPVS150ais shaped as a cover or an end cap that is shaped to fit over the head portion135of BIP130and outer surface123of cable accessory receptacle122. As shown in more detail inFIG. 2, TPVS150aincludes an opening153configured to snuggly fit, e.g., via friction fit, over BIP end135. In addition, the inner diameter of TPVS150ais configured such that flange portion157(seeFIG. 3) snuggly fits over the outer surface123of the cable accessory receptacle that receives BIP130.

An electrical contact is made between a pressure pad155and contact point132via a conductive mating surface158(seeFIG. 3) formed on the contact surface of pressure pad155. The electrical contact between contact point132and mating surface158of pressure pad155is maintained with a suitable compression force, such as is provided by spring156. In addition, the conductive mating surface158of pressure pad155can include a plurality of surface features, such as sharpened protrusions, that are configured to break through any oxidation layer formed on the surface of the contact point132.

As mentioned above, in alternative aspects the TPVS can also be configured to engage an integrated test point, such as test point140, of cable accessory120aor120b. In these embodiments, TPVS150bhas a smaller housing configured to mate with a smaller test point140. The same or similar components included in TPVS150acan be included in TPVS150b.

The housing of TPVS150acan be formed using an appropriate insulating material, such as EPDM or silicone rubber. As shown inFIG. 2, in this aspect, TPVS is formed from a material having an insulating portion154and a conductive or semiconductive portion152. In this embodiment, the outer conductive/semiconductive portion152of TPVS150acomprises a conductive EPDM rubber, and the inner insulating portion comprises an insulating EPDM rubber. In one aspect, the conductive EPDM portion152can be over-molded onto the insulating EPDM portion154. Alternatively, the main body of TPVS150acan be formed from an insulating silicone material, with the outer surface and the mating inner ring coated with a conductive coating to provide for safety and shielding.

In addition, as shown inFIG. 3, TPVS150acan optionally include a substrate, such as a printed circuit board170disposed and configured to fit within the body of the TPVS150a. In this example, the small printed circuit board170includes one or more capacitors. In this example, a single capacitor172is disposed on board170and serves as the “low side” (C2) capacitor of a capacitive voltage divider, schematically illustrated inFIG. 4. Alternatively, the low side capacitor172(or C2) can simply be coupled to the ground wire164without the need for a circuit board170. In a further embodiment, the low side capacitor172can comprise one or more capacitors.

Further, in this example, TPVS150includes a signal output cable160that comprises a signal wire161, which provides a low voltage signal, which may correspond to the voltage across the one or more low voltage capacitors, to an analytics device, such as a data acquisition device or sensor analytics unit (not shown), and optionally, a neutral/ground wire163to couple to ground of the data analytics unit. In this example, and as schematically shown inFIG. 4, signal wire161provides a low voltage signal from pressure pad155which is in electrical contact with the BIP contact point132(capacitively-coupled voltage output). In addition, ground wire164is to be connected to a local/cable accessory ground.

As mentioned above, BIP130can comprise a conventional or modified BIP or end plug. If the BIP130comprises a conventional BIP, having a capacitance C, the TPVS can detect the voltage signal and waveform, where the resulting voltage data signal from the TPVS may be uncalibrated. If there is an independent measurement of the voltage to provide the system a calibration factor, an accurate value of the signal voltage amplitude can be determined and correlated to the line voltage. By measuring temperature at an insulating plug attached to the TPVS, a temperature correction factor may be utilized. It is noted, however, that a conventional BIP or end plug may drift more in temperature than a modified end plug having a capacitor, making the resulting voltage data signal temperature dependent If the BIP130comprises a modified BIP, having a one or more capacitors with a known capacitance, such as is described in PCT Patent Pub. No. WO 2018/211358, incorporated by reference herein in its entirety, the output signal could be calibrated (if a calibration factor is determined). Non-limiting examples of the voltage rating for such a high voltage capacitor(s) C1includes ratings of at least about 2.5 kV, about 3 kV, about 5 kV, about 10 kV, about 15 kV, about 20 kV, about 25 kV, or about 30 kV.

In some embodiments, the high voltage capacitor(s) C1has a capacitance that may be selected in a range from about 10 pF to about 100 pF. Non-limiting examples of the capacitance include about 10 pF, about 30 pF, about 50 pF, about 70 pF, and about 90 pF. C1also has an impedance. The magnitude of the impedance at a base frequency (for example, 50/60 Hz) may be equal to a large impedance value, such as about 100 MΩ. C1may comprise one or more ceramic capacitors. Ceramic capacitors may provide accuracy and stability over the operating temperature range. Non-limiting examples of types of ceramic capacitors include class 1 dielectrics, such as C0G/NP0.

Low side capacitor(s)172(C2) has a capacitance that may be selected in a range from about 10 nF to about 1 μF. Non-limiting examples of the capacitance include about 10 nF, 0.1 μF, about 0.3 μF, about 0.5 μF, about 0.7 μF, and about 0.9 μF. The capacitance value may be selected to provide a capacitance ratio of the high voltage capacitor(s) C1to the low voltage capacitor(s) C2of about 100:1, about 1,000:1, about 10,000:1, or about 100,000:1. Capacitor(s)172has an impedance, where the magnitude of the impedance at the base frequency (for example, 50/60 Hz) may be equal to a low impedance, such as about 10 kΩ Capacitor(s)172(C2) may comprise one or more ceramic capacitors. Ceramic capacitors may provide accuracy and stability over the operating temperature range. Capacitor172may comprise a surface mount capacitor. Based on these values, the voltage data signal may have a maximum voltage less than or equal to about 0.5 V, about 1 V, about 10 V, about 42 V, about 100 V, or about 300 V.

Non-limiting examples of the operating temperature range for the TPVS include a lower end equal to or greater than about −40° C., about −30° C., about −20° C., about −5° C., or higher. Non-limiting examples of the operating temperature range include a higher end equal to or less than about 105° C., about 85° C., about 65° C., about 40° C., or lower. Non-limiting examples of the operating temperature range include being between about −5° C. to about 40° C., about −20° C. to about 65° C., about −30° C. to about 85° C., about −40° C. to about 65° C., and about −40° C. to about 105° C.

The TPVS150amay have a voltage rating, or be rated, to operate in high voltage systems, such as system100. The voltage rating may be designed to meet a standard, jurisdictional requirement, or end-user requirement. Non-limiting examples of the voltage rating of the TPVS in a three-phase system include about 2.5 kV, about 3 kV, about 5 kV, about 15 kV, about 25 kV, about 28 kV, about 35 kV, or about 69 kV or more (classified as phase-to-phase rms). In some embodiments, the voltage rating is at least 5 kV.

In some aspects, the frequency range over which the TPVS is sufficiently accurate may be described as an operating frequency range. The frequency response may be flat or substantially flat, which may correspond to minimum variation, over the operating frequency range. Non-limiting examples of flatness may include plus or minus (+/−) about 3 dB, about 1 dB, about 0.5 dB, and about 0.1 dB. The frequency response may be designed to meet a standard, jurisdictional requirement, or end-user requirement. The operating frequency range may extend to about the 50th harmonic, or even up to the 63rd harmonic, of a base frequency of the high voltage signal present in the separable connector104. Non-limiting examples of the operating frequency range may include one or more of the base frequency of about 60 Hz (or about 50 Hz), the 50th harmonic of about 3 kHz (or about 2.5 kHz), the 63rd harmonic of about 3.8 kHz (or about 3.2 kHz), and higher. The frequency response may also remain stable over all or substantially all of the operating temperature range. Certain remote terminal units (RTUs) or intelligent electronic devices (IEDs) may analyze and report these higher order harmonics.

TPVS150acan further include an eyelet or hole162configured to receive a hook feature of a conventional “hot stick” or insulated pole (not shown). For example, a technician can identify an existing location in the grid to monitor voltage, current, and or power. The technician can remove an existing end cap from an installed BIP or end plug using a hot stick. The technician can then replace the existing end cap with the grounded TPVS using the hot stick to place the TPVS over the test point or BIP and cable accessory receptacle outer wall surface. The signal/neutral/ground wires from the TPVS can be connected to the appropriate monitoring/analytics device or ground location to begin data monitoring/collection. In this manner, TPVS150can be installed onto a BIP130without having to take a power outage.

In a further alternative aspect, a TPVS150ccan be utilized to provide consistent sealing when in use and provide ease of installation/removal. As shown inFIG. 5, TPVS150ccan include a one-way air valve165disposed in an air shaft167formed in the body of TPVS150c. The valve includes a release pin166that opens the valve when depressed/activated and allows air flow through shaft167. When the release pin166is not depressed/activated, air flow through shaft167is blocked. During installation, the technician can replace an existing end cap with the grounded TPVS150cusing the hot stick to place the TPVS150cover the test point or BIP and cable accessory receptacle outer wall surface. The hot stick can have a flat surface on the hook end and can depress the release pin166when placing the TPVS150cover the test point/BIP/receptacle. The air flow through the TPVS body allows for straightforward installation. When the hot stick is removed, and the release pin returns to its “closed” position, air flow through the TPVS150cis blocked by valve165, thus creating a strong suction seal. When removing TPVS150c, the hot stick can activate the valve165/release pin166, opening air flow and removing the suction, thus allowing for more straightforward removal of the TPVS150c. Alternative valve constructions and orientations can also be utilized, as would be apparent to one of ordinary skill in the art given the present description.

Thus, the test point voltage sensor150a,150b,150callows the deployment of a retrofittable voltage sensor to the distribution grid without the utility/customer having to take an outage. While the voltage signal may not be highly accurate, due to the variability in the BIP/end plug capacitance value, the output does scale with the line voltage. The TPVS can provide a sufficient voltage signal so that the monitoring hardware/analytics unit can detect, at least, faults, power flow, and power quality. If calibrated, the TPVS can also detect relatively accurate voltage magnitude. The capacitive voltage divider of the TPVS may facilitate measurements beyond the base or fundamental frequency and may facilitate the use of standard high-voltage DC commissioning testing without additional leakage current through the voltage divider. The TPVS may be utilized in smart grid applications.

The exemplary TPVS configurations described herein may be utilized in a number of different separable connector products and test points, including shielded terminations, specifically, 200A or 600A separable connectors. In addition, the sensors and products incorporating such sensors can be utilized in a network, such as an electrical grid network.

In one example, a TPVS constructed in a manner similar to the device described above, was tested. The upper image ofFIG. 6shows the voltage output of an example TPVS during a 40 kV voltage withstand. The lower image shows signal capture during +125 kV impulse testing per IEEE 386 standard.

Those skilled in the art will appreciate that various adaptations and modifications of the exemplary and alternative embodiments described herein can be configured without departing from the scope of the invention. Therefore, it is to be understood that, within the scope of the appended claims, the invention may be practiced other than as specifically described herein. For example, the example embodiments described herein may be combined in a variety of ways with each other.

All references and publications cited herein are expressly incorporated herein by reference in their entirety into this disclosure, except to the extent they may directly contradict this disclosure.

The recitation of numerical ranges by endpoints includes all numbers subsumed within that range (for example 1 to 5 includes 1, 1.5, 2, 2.75, 3, 3.80, 4, and 5) and any range within that range. Herein, the terms “up to” or “no greater than” a number (for example, up to 50) includes the number (for example, 50), and the term “no less than” a number (for example, no less than 5) includes the number (for example, 5).

Terms related to orientation, such as “end”, are used to describe relative positions of components and are not meant to limit the orientation of the embodiments contemplated.

The term “and/or” means one or all of the listed elements or a combination of any two or more of the listed elements (for example, casting and/or treating an alloy means casting, treating, or both casting and treating the alloy).

The phrases “at least one of,” “comprises at least one of,” and “one or more of” followed by a list refers to any one of the items in the list and any combination of two or more items in the list.