WO2020097933A1

WO2020097933A1 - Voltage sensor and apparatus

Info

Publication number: WO2020097933A1
Application number: PCT/CN2018/115999
Authority: WO
Inventors: Liang Wu; Zhonghua Deng
Original assignee: Abb Schweiz Ag
Priority date: 2018-11-16
Filing date: 2018-11-16
Publication date: 2020-05-22
Also published as: EP3881085A1; EP3881085A4; CN112997086A

Abstract

Embodiments of present disclosure relate to a voltage sensor(10) and an apparatus(11) including the voltage sensor(10). The voltage sensor(10) comprises a first capacitor(12) configured to receive a first voltage for a first phase of an alternating current supply system(1), a second capacitor(14) coupled between the first capacitor(12) and a reference voltage and configured to generate a second voltage based on the first voltage; and a transformer(16) comprising a first winding(164) coupled in parallel to the second capacitor(14) and a second winding(166) magnetically coupled to the first winding(164), the transformer(16) configured to generate a third voltage directly for a field testing unit without conversion of voltage by a further transformer. The third voltage is based on the second voltage and below the second voltage.

Description

VOLTAGE SENSOR AND APPARATUS

TECHNICAL FIELD

Example embodiments of the present disclosure generally relate to voltage measurement, and more particularly, to a voltage sensor and an apparatus including the voltage sensor.

BACKGROUND

Alternating current (AC) power supply is widely used to provide electrical power. In order to maintain appropriate operation of an AC supply system, voltages at various locations of the AC power supply, among other properties of the AC supply system, need to be measured to determine real-time condition of AC transmission lines or equipment.

Generally, to measure a voltage of AC power supply, a resistance voltage divider (RVD) or a capacitance voltage divider (CVD) device is often used. The CVD device includes two capacitors coupled between the AC power supply and ground.

However, conventional RVD and CVD approaches are inaccurate and inefficient, because they are easily affected by a load, such as the transformer, coupled to the RVD or CVD.

SUMMARY

Example embodiments of the present disclosure propose a solution for AC voltage measuring.

In a first aspect, example embodiments of the present disclosure provide a voltage sensor. The voltage sensor comprises a first capacitor configured to receive a first voltage for a first phase of an alternating current supply system, a second capacitor coupled between the first capacitor and a reference voltage and configured to generate a second voltage based on the first voltage; and a transformer comprising a first winding coupled in parallel to the second capacitor and a second winding magnetically coupled to the first winding, the transformer configured to generate, based on the second voltage, a third voltage directly for a field testing unit without conversion of voltage by a further transformer, the third voltage being below the second voltage.

In some embodiments, the first voltage is below 50 kV, and the third voltage is below 12V.

In some embodiments, the first winding is directly coupled in parallel to the second capacitor without a reactance element coupled in serial with the first winding.

In some embodiments, the voltage sensor further comprises a third winding magnetically coupled to the first winding and configured to generate, based on the second voltage, a fault detection voltage for detecting a fault of the AC supply system.

In some embodiments, the voltage sensor further comprises an adjustable capacitor coupled to the second capacitor and configured to adjust capacitance of the second capacitor.

In a second aspect, example embodiments of the present disclosure provide a system for measuring voltages of at least two phases of an alternating current supply system. The system comprises at least two voltage sensors of the first aspect. The at least two voltage sensors are configured to sense voltages of the at least two phases of the AC supply system and output voltage signals indicating voltages of respective phase of the AC supply system.

In some embodiments, the system further comprises a connection shielding wire coupled to the at least voltage sensors and configured to transmit the third voltages from the at least two voltage sensors.

In some embodiments, the connection shielding wire includes two shielding layers encapsulating the conductive connection wire.

In a third aspect, example embodiments of the present disclosure provide a voltage sensing apparatus for implementing the voltage sensor of the first aspect. The voltage sensing apparatus comprises an AC terminal configured to receive the first voltage for the first phase of the AC supply system, the voltage sensor of the first aspect, and an output terminal coupled to the second winding and configured to output the third voltage; and an insulation material configured to encapsulate the first capacitor and the transformer and expose the second capacitor. The first electrode of the first capacitor of the voltage sensor is electrically coupled to the AC terminal.

In some embodiments, the first capacitor includes a ceramic capacitor, and the second capacitor comprises a ceramic capacitor.

In some embodiments, the transformer is located between the first capacitor and the second capacitor with a wire extending through hollow portion of the windings of the transformer, the wire being configured to couple the first capacitor to the second capacitor.

In some embodiments, the system further comprises a first socket electrically coupled to the first capacitor and the reference voltage, the first socket being configured to be fit by the second capacitor.

In some embodiments, the output terminal is configured to match an aviation plug.

In some embodiments, the aviation plug is configured to couple to a connection shielding wire.

In some embodiments, the first capacitor is located above the transformer and the electrodes of the first capacitor are configured to electromagnetically shield the first capacitor and uniform electric field.

BRIEF DESCRIPTION OF THE DRAWINGS

Through the following detailed descriptions with reference to the accompanying drawings, the above and other objectives, features and advantages of the example embodiments disclosed herein will become more comprehensible. In the drawings, several example embodiments disclosed herein will be illustrated in an example and in a non-limiting manner, wherein:

Fig. 1 illustrates a system for measuring voltages of three phases of an AC supply system in accordance with some example embodiments of the present disclosure;

Fig. 2 illustrates voltage sensing apparatuses for the three phases of AC supply system in accordance with some example embodiments of the present disclosure;

Fig. 3 illustrates a schematic for the voltage sensor and a FTU in accordance with some example embodiments of the present disclosure;

Fig. 4 illustrates a cross-section view of a voltage sensing apparatus in accordance with some example embodiments of the present disclosure; and

Fig. 5 illustrates a front view of an output terminal for an aviation plug in accordance with some example embodiments of the present disclosure.

Throughout the drawings, the same or corresponding reference symbols refer to the same or corresponding parts.

DETAILED DESCRIPTION

The subject matter described herein will now be discussed with reference to several example embodiments. These embodiments are discussed only for the purpose of enabling those skilled persons in the art to better understand and thus implement the subject matter described herein, rather than suggesting any limitations on the scope of the subject matter.

The term “comprises” or “includes” and its variants are to be read as open terms that mean “includes, but is not limited to. ” The term “or” is to be read as “and/or” unless the context clearly indicates otherwise. The term “based on” is to be read as “based at least in part on. ” The term “being operable to” is to mean a function, an action, a motion or a state can be achieved by an operation induced by a user or an external mechanism. The term “one embodiment” and “an embodiment” are to be read as “at least one embodiment. ” The term “another embodiment” is to be read as “at least one other embodiment. ”

Unless specified or limited otherwise, the terms “mounted, ” “connected, ” “supported, ” and “coupled” and variations thereof are used broadly and encompass direct and indirect mountings, connections, supports, and couplings. Furthermore, “connected” and “coupled” are not restricted to physical or mechanical connections or couplings. In the description below, like reference numerals and labels are used to describe the same, similar or corresponding parts in the Figures. Other definitions, explicit and implicit, may be included below.

As mentioned above, conventional RVD and CVD approaches are inaccurate and inefficient, because they are easily affected by a load coupled to the RVD or CVD device. As an alternative, conventional capacitor voltage transformer (CVT) approaches for AC voltage often employ two-stage voltage conversion. At the first stage, the voltage from an AC source is converted from a voltage in a first order of 100 kV, for example 110 kV, to a voltage in an second order of several kV, for example 5.7 kV, at the middle node of the CVT device. At the second stage, the voltage in the second order is further converted to a voltage in a third order of dozens of volts, for example 57 V, by a transformer.

A load, such as a field testing unit (FTU) , may couple to the transformer to output a digital data indicating the voltage of the AC supply system. However, the FTU often includes a transformer to further convert the voltage in the order of dozens of volts to a voltage in an order of several volts, for example 2V, such that the voltage in the order of several volts can be suitable for subsequent processing.

Direct conversion from the voltage in the order of 100kV to the voltage in the order of dozens of volts or several volts is impossible, because the RVD or CVD device for implementing this conversion requires extremely large capacitor or resistor for receiving the AC voltage, and the cost for the extremely large capacitor or resistor will become inacceptable.

In addition, the capacitor or resistor at the lower portion of the RVD or CVD device may be vulnerable for breakdown. Moreover, the load at the lower portion of the RVD or CVD device is coupled in parallel to the capacitor or the resistor, and the capacitance or resistance of the FTU and cable poses a non-negligible effect to the capacitor of the lower portion. Thus, the change of FTU will change the parallel resistance or capacitance of the lower portion, and the voltage of the lower portion will also change. In this case, the change of FTU and cable will easily affect accuracy of the RVD or CVD device.

Fig. 1 illustrates a system 1 for measuring voltages of three phases of an AC supply system in accordance with some example embodiments of the present disclosure. The system 1 includes a first voltage sensor 10 for measuring a first phase V _A of the AC supply system, a second voltage sensor 20 for measuring a second phase V _B of the AC supply system, and a third voltage sensor 30 for measuring a third phase Vc of the AC supply system. The first, second and third voltage sensors are coupled to a FTU 40 for obtaining a data indicating voltages at respective phase.

The FTU 40 includes a first signal processing unit (SPU) 41, a second SPU 42, a third SPU 43 and a comparison circuit 44. The first, second and third SPUs are coupled to respective voltage sensor for obtaining a data indicating voltages at respective phase. Although the system 1 includes three voltage sensors and three FTUs, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, only one voltage sensor and SPU for any phase of the AC system may be applied, and more than three voltage sensors and FTUs may also be applied.

The comparison circuit 44 is serially coupled with the first, second and third voltage sensors for measuring summed voltage of the voltage signals from the three voltage sensors. Since the three voltages are from three phases of the AC supply system, normally the summed voltage is small, for example 0V. In case that the summed voltage exceeds a predetermined voltage window, for example, -1V to +1V, there may be a fault in the AC supply system. The comparison circuit 44 may thus transmit a signal indicating the fault to an alert device or to a control center of the AC supply system.

Although the three SPUs and the processing circuit 44 are provided in the FTU 40, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the three FTUs and the processing circuit 44 may be provided separately. In addition, although a FTU is used as a load for obtaining digital information of the voltage of the AC supply system, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. Other analog-to-digital converter (ADC) devices and processing circuits may also be applied.

Fig. 2 illustrates voltage sensing apparatuses for the three phases of AC supply system in accordance with some example embodiments of the present disclosure. The three voltage sensing apparatus 11, the second voltage sensing apparatus 21 and the third voltage sensing apparatus 31 are used to implement the three

voltage sensors

10, 20 and 30. Each of the three voltage sensing apparatuses includes an output terminal for an aviation plug. The aviation plug is coupled with a connection shielding wire 321 to transmit the voltages to the FTUs.

In an example, the connection shielding wire 321 includes a two-layer shielding structure. The connection shielding wire 321 includes a first shielding layer, such as aluminum foil layer, to encapsulate an insulation layer encapsulating the core conductive wire. The connection shielding wire 321 may also include a second shielding layer, such as copper-mesh layer, to encapsulate the first shielding layer. By employing the aviation plug and the connection shielding wire, the voltage sensing apparatuses can proof noise interruption.

Although three voltage sensing apparatuses are illustrated, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, only one sensing apparatus or two sensing apparatuses may be applied, and more than three sensing apparatus may also be applied. For example, in a railway power supply system, two phases of AC supply voltage may be employed. In this event, two sensing apparatuses may be used for sensing voltage of respective phase. Details of the voltage sensing apparatus will be described below.

Fig. 3 illustrates a schematic for the voltage sensor 10 and a FTU 40 in accordance with some example embodiments of the present disclosure. The voltage sensor 10 is an example of the three voltage sensors of Fig. 1, and includes a first capacitor 12, a second capacitor 14 and a transformer 16. The first capacitor 12 is configured to receive a first voltage V _A for a first phase of an AC supply system. The first voltage is below 50 kV. In practice, the first voltage may be one of 40.5 kV, 35 kV, 24 kV, 12 kV, 6kV and 3kV.

The second capacitor 14 is coupled between the first capacitor 12 and a reference voltage, for example ground, and configured to generate a second voltage based on the first voltage. The second voltage is below 50 V. In an example, the second voltage is 18.8 V.

The transformer 16 includes a first winding 164 and a second winding 166. The first winding 164 is coupled in parallel to the second capacitor 14. The second winding 166 is magnetically coupled to the first winding 164. The transformer 16 is configured to generate, based on the second voltage, a third voltage directly for a FTU without conversion of voltage by a further transformer. The third voltage is below 12 V, which is below the second voltage. In an example, the third voltage is 1.88 V. In addition, the transformer 16 may increase impedance.

The first winding 164 is directly coupled in parallel to the second capacitor 14 without a reactance element coupled in serial with first winding. Although a reactance 162 is illustrated in Fig. 4, this reactance 162 is inherent to or can be implemented by the first winding 164. In practice, no reactance element is needed to serially couple to the first winding 164. This is because the reactance in this case is relatively small, and the reactance of the first winding 164 can achieves the function of an individual reactance. By contrast, a separate reactance element is needed to serially couple to the first winding for resonance in conventional CVD or RVD approaches for AC voltages of 110 kV. In this case, the voltage sensor 10 eliminates requirement of a separate reactance element. This reduces cost of a voltage sensor.

The voltage sensor 10 may further include a third winding 168. The third winding 168 is magnetically coupled to the first winding 164, and configured to generate, based on the second voltage, a fault detection voltage for detecting a fault of the AC supply system. The third winding 168 is serially coupled with the third windings of another two voltage sensors and the comparison circuit for detecting the fault of the AC supply system, as described above with reference to the comparison circuit 44 of Fig. 1.

Although the third winding is illustrated, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the voltage sensor 10 may include no third winding. The voltage sensor may sense respective phase, and the processing circuit may determine an fault based on the data from the three voltage sensor without a fault detection voltage from the serially coupled third windings.

Although the voltage sensor 10 is illustrated to include a second capacitor 14, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, an adjustable capacitor (not shown) may be coupled to the second capacitor 14 and configured to adjust capacitance of the second capacitor 14. By providing an adjustable capacitor, the utility operator may adjust the voltage sensor 10 in-site as needed. For example, the second voltage and the third voltage may be adjusted in response to adjusting the adjustable capacitor. As an alternative, the second capacitor 14 may be an adjustable capacitor.

The SPU 41 includes an operational amplifier 411, an ADC converter 412 and a controller 413. The operational amplifier 411 is directly coupled to the second winding 166 and configured to receive the voltage signal from the second winding 166. The ADC converter 412 is coupled to the operational amplifier 412, and configured to convert the voltage signal into a digital signal. The controller 413 is configured to determine the data indicative of the voltages of the at least two phases based on the digital signal.

In an example, the controller 413 is a CPU. Although a CPU may be used to implement the controller 413, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, a digital signal processor (DSP) may also be used to implement the controller 413. It can be seen that the third voltage is directly transmitted to the SPU 41 without conversion of voltage by a further transformer.

As compared to the conventional RVD and CVD, the composite impedance of the cable and the FTU will be much greater than original composite impedance at the second capacitor 14 due to impedance amplification of the transformer 16 and also significantly greater than the impedance of the second capacitor. In this case, the variation of the load applied at the second capacitor 14 will have little impact on the sensing accuracy. In addition, the cost of the FTU and the AC voltage sensing system is reduced.

Fig. 4 illustrates a cross-section view of a voltage sensing apparatus 11 in accordance with some example embodiments of the present disclosure. The voltage sensing apparatus 11 includes a housing 111 fixed to a support base 114, and an AC terminal 112 arranged on a first surface of the housing 111 for receiving the first voltage V _A for the first phase of the AC supply system. By setting the AC terminal 112 on top surface and other terminals on other surface, the apparatus is easy to mount in-site. Although the voltage sensing apparatus 11 is illustrated to include a housing 111, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, the voltage sensing apparatus 11 may include no housing 111, with the encapsulation material exposed to environment.

The voltage sensor 10 of Fig. 3 is located in the housing 111. The first capacitor 12 included two

electrodes

121 and 123. Both electrodes are sufficiently large so as to shield the transformer 16 in a top view. By setting so, the first capacitor 12 is located above the transformer 16, and the electrodes of the first capacitor 12 provide an electromagnetically shielding function due to the large electrodes of the first capacitor 12.

A first electrode 121 is located on top surface of the voltage sensor 10. The first electrode 121 of the first capacitor 12 of the voltage sensor 10 is electrically coupled to the AC terminal 112. The second electrode 123 of the first capacitor 12 of the voltage sensor 10 is located below the first electrode 121. A dielectric 122 is sandwiched between the first and

second electrodes

121 and 123. The first capacitor 12 and the second capacitor 14 may be ceramic capacitors.

By using a ceramic capacitor, the voltage sensing device may have a compact size and a long life time. In addition, the ceramic capacitor may have a stable property during temperature variation. For voltage sensors for an AC system, temperature may change significantly. As such, the ceramic capacitor can provide a stable capacitance during the temperature variation, and the sensing accuracy may be increased accordingly.

The second capacitor 14 is located on bottom surface of the voltage sensor 10, and is electrically coupled to the first capacitor 12 via a wire extending through hollow portion of the windings of the transformer 16. The transformer 16 is located between the first capacitor 12 and the second capacitor 14. The first and second windings of the transformer 16 are circled around the wire, and insulated from each other by an insulation material 118.

The insulation material 118 is filled into the housing 111 and configured to encapsulate the first capacitor 12 and the transformer 16 and expose the second capacitor 14. In an example, the insulation material 118 may be epoxy. An output terminal 113 is located on a second surface of the housing 111 for outputting the third voltage. The output terminal 113 is electrically coupled to a second electrode of the second winding 166, configured to match an aviation plug. The insulation material 118 is filled between the output terminal and ground.

By physical isolation between the windings of the transformer 16, the voltage sensor can withstand a voltage variation of 3 kV/min. By contrast, the conventional CVD or RVD device cannot withstand such a voltage variation, because the 3 kV voltage directly applied between the output terminal and the ground may cause a breakdown to the CVD or RVD device. Our design can withstand due to the physical separate between first winding and second winding.

As described above, the second capacitor 14 is exposed from the insulation material 118. By setting so, the second capacitor 14 may be easily dismounted from the voltage sensor and replaced by a new second capacitor. In order to facilitate the mounting and dismounting of the second capacitor 14, a first socket may be provided to electrically couple to the first capacitor 12 and the reference voltage. The first socket may be encapsulated by the insulation material 118, and configured to be fit by the second capacitor 14.

In addition, a further socket may be provided for the adjustable capacitor 15 as described above. The further socket may also be encapsulated by the insulation material 118, and configured to be fit by the adjustable capacitor. Although two sockets are illustrated for the second capacitor 14 and the adjustable capacitor 15, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, only one socket or more than three sockets may be provided for capacitors.

Fig. 5 illustrates a front view of an output terminal 113 for an aviation plug in accordance with some example embodiments of the present disclosure. The output terminal 113 is configured to match the aviation plug, and includes four terminals for voltage signal and ground, and a circular insulation material 281. Although the four terminals are illustrated, this is only for illustration without suggesting any limitations as to the scope of the subject matter described here. For example, two or more than four terminals may be provided in the circular insulation material 281.

Further, while operations are depicted in a particular order, this should not be understood as requiring that such operations be performed in the particular order shown or in sequential order, or that all illustrated operations be performed, to achieve desirable results. In certain circumstances, multitasking and parallel processing may be advantageous. Likewise, while several specific implementation details are contained in the above discussions, these should not be construed as limitations on the scope of the present disclosure, but rather as descriptions of features that may be specific to particular embodiments. Certain features that are described in the context of separate embodiments may also be implemented in combination in a single embodiment. On the other hand, various features that are described in the context of a single embodiment may also be implemented in multiple embodiments separately or in any suitable sub-combination.

Although the subject matter has been described in language specific to structural features and/or methodological acts, it is to be understood that the subject matter defined in the appended claims is not necessarily limited to the specific features or acts described above. Rather, the specific features and acts described above are disclosed as example forms of implementing the claims.

Claims

A voltage sensor (10) , comprising:

a first capacitor (12) configured to receive a first voltage (V _A) for a first phase of an alternating current (AC) supply system,

a second capacitor (14) coupled between the first capacitor (12) and a reference voltage and configured to generate a second voltage based on the first voltage; and

a transformer (16) comprising a first winding (164) coupled in parallel to the second capacitor (14) and a second winding (166) magnetically coupled to the first winding (164) , the transformer (16) configured to generate, based on the second voltage, a third voltage directly for a field testing unit without conversion of voltage by a further transformer, the third voltage being below the second voltage.
The voltage sensor (10) of claim 1, wherein the first voltage is below 50 kV, and the third voltage is below 12V.
The voltage sensor (10) of Claim 1, wherein the first winding (164) is directly coupled in parallel to the second capacitor without a reactance element coupled in serial with the second capacitor.
The voltage sensor (10) of claim 1, further comprising a third winding (168) magnetically coupled to the first winding (164) and configured to generate, based on the second voltage, a fault detection voltage for detecting a fault of the AC supply system.
The voltage sensor (10) of claim 1, further comprising an adjustable capacitor coupled to the second capacitor (14) and configured to adjust capacitance of the second capacitor (14) .
A system (1) for measuring voltages of at least two phases of an alternating current (AC) supply system, comprising:

at least two voltage sensors (10) of any of claims 1-5, the at least two voltage sensors (10) configured to sense voltages of the at least two phases of the AC supply system and output voltage signals indicating voltages of respective phase of the AC supply system.
The system (1) of claim 6, further comprising:

a connection shielding wire coupled to the at least voltage sensors and configured to transmit the third voltages from the at least two voltage sensors (10) .
The system (1) of claim 7, wherein the connection shielding wire includes two shielding layers encapsulating the conductive connection wire.
A voltage sensing apparatus (11) for implementing the voltage sensor (10) of claim 1, comprising:

an alternating current (AC) terminal (112) configured to receive the first voltage (V _A) for the first phase of the AC supply system,

the voltage sensor (10) of claim 1, a first electrode (121) of the first capacitor (12) of the voltage sensor (10) being electrically coupled to the AC terminal (112) ; and

an output terminal (113) coupled to the second winding and configured to output the third voltage; and

an insulation material (118) configured to encapsulate the first capacitor (12) and the transformer (16) and expose the second capacitor (14) .
The voltage sensing apparatus (11) of claim 9, wherein the first capacitor includes a ceramic capacitor, and the second capacitor comprises a ceramic capacitor.
The voltage sensing apparatus (11) of claim 9, wherein the transformer (16) is located between the first capacitor (12) and the second capacitor (14) with a wire extending through hollow portion of the windings of the transformer (16) , the wire being configured to couple the first capacitor (12) to the second capacitor (14) .
The voltage sensing apparatus (11) of claim 9, further comprising a first socket electrically coupled to the first capacitor (12) and the reference voltage, the first socket being configured to be fit by the second capacitor (14) .
The voltage sensing apparatus (11) of claim 9, wherein the output terminal (113) is configured to match an aviation plug.
The voltage sensing apparatus (11) of claim 14, wherein the aviation plug is configured to couple to a connection shielding wire.
The voltage sensing apparatus (11) of claim 9, wherein the first capacitor (12) is located above the transformer (16) and the electrode of the first capacitor are configured to electromagnetically shield the first capacitor and uniform electric field.