CN114375400A - Adjustable voltage sensor - Google Patents

Abstract

The invention relates to a voltage sensor (1) comprising a voltage divider (40) for sensing an AC voltage of a HV/MV power conductor (10). In order to adjust the common total impedance of the low voltage parts of the voltage divider to a desired impedance, the low voltage part (60) comprises one or more low voltage impedance elements (110), a plurality of adjusting impedance elements (80) and a plurality of switches. Each switch electrically connects in parallel the adjusting impedance to at least one of the one or more low-voltage impedance elements (110) in its connected state. The total impedance of the high voltage part (50) and the total impedance of the low voltage part (60) of the voltage divider (40) are adapted such that by bringing one or more of the switches (90) into its connected state, the voltage divider (40) has a voltage division ratio of 3077, 6154, 6769 or 10000 for AC voltages between 5kV and 25kV single-phase ground and frequencies between 40 hertz and 70 hertz.

Description

Adjustable voltage sensor

Background

The present disclosure relates to AC voltage sensors for high or medium voltage power conductors in power networks and national power grids, in particular to voltage sensors comprising a voltage divider. The disclosure also relates to a method of adjusting the impedance in such a voltage divider.

Power network operators utilize voltage sensors to determine the voltage of power conductors in their networks. In the case of decentralized energy production, knowledge of the state of the network is essential to the proper operation and maintenance of the network.

A common type of voltage sensor for AC voltages uses a voltage divider having a high voltage part and a low voltage part, which are connected in series between the high voltage of the power conductor and the electrical ground. The contact between the high-voltage part and the low-voltage part provides a partial voltage which is proportional to the voltage of the power conductor and varies with this voltage. The divided voltage (or "signal voltage") is measured and processed to determine the voltage of the power conductor. The scaling factor between the voltage Vin of the power conductor and the signal voltage Vout is commonly referred to as the "voltage division ratio" T, where Vout is Vin/T, and T depends on the ratio of the total impedance of the high voltage part to the total impedance of the low voltage part.

In order to evaluate the signal voltage independently of the individual characteristics of the voltage divider, network operators often specify the voltage division ratio precisely. However, the impedance of the components of the high-voltage part and the low-voltage part is only specified to a certain accuracy, and their production tolerances are not negligible, so that the respective total impedance of the high-voltage part and the low-voltage part is only predictable within a certain corridor. Once assembled, the voltage divider can prove to have a voltage division ratio that is outside the accuracy specifications of the network operator.

Disclosure of Invention

The present disclosure relates to a voltage sensor for use with MV or HV power distribution networks. In such networks, power is distributed via HV/MV cables, transformers, switchgears, substations and the like at currents of several hundred amperes and voltages of several tens of kilovolts. As used herein, the term "medium voltage" or "MV" refers to AC voltages in the range of 1kV to 72kV, while the term "high voltage" or "HV" refers to AC voltages greater than 72 kV.

Traditionally, in High Voltage (HV) and Medium Voltage (MV) power networks, the voltage division ratio of a voltage divider in an AC voltage sensor is determined after assembly of the sensor and is taken into account by adjusting a downstream sensing circuit (commonly referred to as an RTU) to the voltage division ratio of a particular sensor before this sensing circuit determines the voltage of the power conductor of the signal voltage output from the sensor. However, providing a HV/MV partial pressure sensor with a given, consistent and predetermined partial pressure ratio may make the sensing circuit simpler, as it does not need to deal with sensors with a certain (possibly broad) range of partial pressure ratios. In addition, providing a uniform sensor with a predetermined voltage division ratio facilitates swapping one sensor for another without having to adjust the sensing circuit.

The present disclosure seeks to address these needs. In a first general aspect, the present disclosure provides a voltage sensor for sensing an AC voltage of an HV/MV power conductor, the voltage sensor comprising a capacitive voltage divider for sensing the AC voltage, the voltage divider comprising

-a high voltage part comprising one or more high voltage capacitors electrically connected in series with each other;

-a low voltage part comprising one or more low voltage capacitors electrically connected in series with each other between the high voltage part and an electrical ground;

-a signal contact, which is electrically arranged between the high voltage part and the low voltage part, for providing a signal voltage indicative of the AC voltage, characterized in that the low voltage part further comprises a plurality of adjusting capacitors and a plurality of switches for adjusting the common total impedance of the low voltage part to a desired impedance, wherein each switch is associated with and electrically connected to one or more of said adjusting capacitors and is capable of bringing the switch into a connected state and into a disconnected state, such that the switch, in its connected state, electrically connects the adjusting capacitor associated with the switch in parallel to at least one of the one or more low voltage capacitors; and in the disconnected state of the switch, at least one electrode of the regulating capacitor associated with the switch is electrically disconnected from the low-voltage capacitor, the switch connecting the associated regulating capacitor to the low-voltage capacitor in the connected state of the switch. The total impedance of the high voltage part and the total impedance of the low voltage part of the voltage divider are adapted such that by bringing one or more of the switches into a connected state of the switch, the voltage divider has a voltage division ratio of 3077 ± 0.5%, or 6154 ± 0.5%, or 6769 ± 0.5%, or 10000 ± 0.5% for AC voltages between 5kV and 25kV single phase ground and frequencies between 40 hertz and 70 hertz.

Each tuning capacitor may be electrically connected in parallel to the low voltage capacitor (or capacitors) through a switch associated with the tuning capacitor. Increasing the capacitance of the adjustment capacitor increases the capacitance of the low voltage portion of the voltage divider and decreases the impedance of the low voltage portion, whereby the voltage dividing ratio of the voltage divider becomes large.

Providing a suitable number of regulating capacitors with suitable respective impedances, either individually or in addition to other regulating capacitors already connected in parallel, each of which may be individually connected in parallel to one or more of the low-voltage capacitors by means of an associated switch, allows to reduce the accumulated total impedance of the low-voltage part and thereby to increase the voltage division ratio T of the voltage divider to a desired predetermined voltage division ratio. The limit to this adjustment of the voltage division ratio is given by the number of adjustment capacitors and the corresponding impedance of the adjustment capacitors and the accumulated impedance of the low voltage capacitors.

Depending on the type of switch used, the individual regulating capacitor may be disconnected from the low-voltage capacitor to which the regulating capacitor was previously connected by its associated switch. The regulating capacitor may be disconnected by disconnecting one or both electrodes of the regulating capacitor from the low voltage capacitor to which the regulating capacitor was previously connected. This disconnection leads to a higher accumulated total impedance of the low voltage part and thus to a smaller voltage division ratio T of the voltage divider. Disconnecting one or more individual tuning capacitors from the low voltage part may be advantageous to obtain a desired predetermined voltage division ratio of the voltage divider.

The same principle can be applied in resistive voltage dividers. In a second basic aspect, the present disclosure therefore also provides a voltage sensor for sensing an AC voltage of an HV/MV power conductor, the voltage sensor comprising a resistive voltage divider for sensing the AC voltage, the voltage divider comprising

-a high voltage part comprising one or more high voltage resistors electrically connected in series with each other;

-a low voltage portion comprising one or more low voltage resistors electrically connected in series with each other between the high voltage portion and an electrical ground;

-a signal contact, which is electrically arranged between the high voltage part and the low voltage part, for providing a signal voltage indicative of the AC voltage, characterized in that the low voltage part further comprises a plurality of adjusting resistors and a plurality of switches for adjusting the common total impedance of the low voltage part to a desired impedance, wherein each switch is associated with and electrically connected to one or more of the adjusting resistors and is capable of bringing the switch into a connected state and into a disconnected state, such that the switch electrically connects the adjusting resistor associated with the switch in parallel to at least one of the one or more low voltage resistors in the connected state of the switch; and electrically disconnecting at least one contact of the regulating resistor associated with the switch from the low voltage resistor in the disconnected state of the switch, the switch connecting the associated regulating resistor to the low voltage resistor in the connected state of the switch. The total impedance of the high voltage part and the total impedance of the low voltage part of the voltage divider are adapted such that by bringing one or more of the switches into a connected state of the switch, the voltage divider has a voltage division ratio of 3077 ± 0.5%, or 6154 ± 0.5%, or 6769 ± 0.5%, or 10000 ± 0.5% for AC voltages between 5kV and 25kV single phase ground and frequencies between 40 hertz and 70 hertz.

In an even more general sense, the present disclosure provides a voltage sensor for sensing an AC voltage of an HV/MV power conductor, the voltage sensor comprising a voltage divider for sensing the AC voltage, the voltage divider comprising

-a high voltage part comprising a plurality of discrete high voltage impedance elements, the high voltage impedance elements being electrically connected in series with each other;

-a low voltage portion comprising one or more discrete low voltage impedance elements electrically connected in series with each other between the high voltage portion and an electrical ground;

-a signal contact, which is electrically arranged between the high voltage part and the low voltage part, for providing a signal voltage indicative of the AC voltage, characterized in that the low voltage part further comprises a plurality of adjusting impedance elements and a plurality of switches for adjusting the common total impedance of the low voltage part to a desired impedance, wherein each switch is associated with and electrically connected to one or more of the adjusting impedance elements and is capable of bringing the switch into a connected state and into a disconnected state, such that the switch electrically connects the adjusting impedance element associated with the switch in parallel to at least one of the one or more low voltage impedance elements in the connected state of the switch; and electrically disconnecting at least one contact of the adjusting impedance element associated with the switch from the low-voltage impedance element in the disconnected state of the switch, the switch connecting the associated adjusting impedance element to the low-voltage impedance element in the connected state of the switch. The total impedance of the high voltage part and the total impedance of the low voltage part of the voltage divider are adapted such that by bringing one or more of the switches into a connected state of the switch, the voltage divider has a voltage division ratio of 3077 ± 0.5%, or 6154 ± 0.5%, or 6769 ± 0.5%, or 10000 ± 0.5% for AC voltages between 5kV and 25kV single phase ground and frequencies between 40 hertz and 70 hertz.

The regulating capacitor is a conventional capacitor, suitably electrically connected by means of a switch associated with the regulating capacitor, so that the regulating capacitor can be electrically connected in parallel to at least one of the low-voltage capacitor or the low-voltage portion of the voltage divider by bringing the switch into its connected state. The regulating capacitor is not connected in parallel to at least one of the low voltage portion of the voltage divider or the low voltage capacitor when the switch is in the disconnected state of the switch.

The tuning capacitor may be a discrete capacitor, a surface mount capacitor, a through-hole capacitor, or an embedded capacitor. For example, the electrodes of the conditioning capacitor may be formed by conductive traces or conductive areas in the support, for example on a circuit board or on a PCB (printed circuit board).

A discrete capacitor is a capacitor that exists without other elements that must be present to form the capacitor. In particular, the discrete capacitors may be present independently of conductive traces on a printed circuit board or PCB or other component. A discrete resistor is a resistor that is present in the case of other elements that must be present to form the resistor. In particular, the discrete resistors may be present independently of conductive traces on a printed circuit board or PCB or other component. Typically, a discrete impedance element (i.e., a discrete capacitor, a discrete resistor, or a discrete inductor) is an impedance element that is present without other elements that must be present to form a capacitor. In particular, the discrete impedance elements may be present independently of conductive traces on a printed circuit board or PCB or other component.

The adjusting resistor is a conventional resistor as described above, the resistor being suitably electrically connected by a switch associated with the resistor, such that the resistor may be electrically connected in parallel to at least one of the low voltage part of the voltage divider or the low voltage resistor by bringing the switch into the connected state of the switch. When the switch is in the disconnected state of the switch, the regulating resistor is not connected in parallel to at least one of the low voltage part of the voltage divider or the low voltage resistor.

The tuning resistor may be a discrete resistor, a surface mount resistor, a through-hole resistor, or an embedded resistor.

Generally, the adjusting impedance element is a conventional impedance element (i.e. a resistor, a capacitor or an inductor) suitably electrically connected by a switch associated with the impedance element, such that the impedance element can be electrically connected in parallel to at least one of the low voltage part of the voltage divider or the low voltage impedance element by bringing the switch into the connected state of the switch. The adjusting resistance element is not connected in parallel to at least one of the low voltage portion of the voltage divider or the low voltage impedance element when the switch is in the disconnected state of the switch.

The tuning impedance element may be a discrete impedance element, a surface mount impedance element, a through-hole mounted impedance element, or an embedded impedance element.

The switch that may be used for the voltage sensor according to the present disclosure may for example be a mechanically operated switch, wherein a mechanical action brings the switch from a connected state of the switch into a disconnected state of the switch, or vice versa, such as a dip switch or an electrically operated switch or an optically operated switch. The switches in a voltage sensor according to the present disclosure may be of different types: the first switch and the third switch may for example be mechanical switches, the second switch may be an electrical switch, etc.

If the switch is kept alone in the switching devices or transformers of the power network, which are specified by its manufacturer for the power network, under normal operating conditions, i.e. under ambient conditions, the switch maintains its state (connected state or disconnected state) for a period of at least months or years after bringing the switch from its connected state into its disconnected state, or vice versa.

The switch may be an electrical element that can be brought from a disconnected state into a connected state but cannot thereafter be returned into its disconnected state. Alternatively, the switch may be an electrical element that may be brought from a connected state into a disconnected state but thereafter cannot be returned into its connected state. Preferably, however, the switch may be an electrical element which can be brought from a disconnected state into a connected state and which can thereafter be brought back into its disconnected state and which can thereafter be brought back into its connected state.

In embodiments where one or more of the tuning capacitors are supported on the PCB, the switches associated with the one or more of the tuning capacitors may be supported on the PCB. In embodiments where one or more of the tuning resistors are supported on the PCB, the switches associated with the one or more of the tuning resistors may be supported on the PCB.

A switch is considered to be associated with a regulating capacitor or a regulating resistor or a regulating impedance element if it electrically connects in parallel to at least one of one or more low-voltage capacitors or low-voltage resistors or low-voltage impedance elements of the voltage divider by bringing the switch into the connected state of the switch.

In contrast to the regulating capacitor, the low-voltage capacitor is part of the low-voltage part from the beginning and before any switch is brought into the connected state of the switch. In contrast to the regulating resistor, the low voltage resistor is part of the low voltage part from the beginning and before any switch is brought into the connected state of the switch.

The common total impedance of the low voltage portions of the voltage divider is the electrical impedance of the entire low voltage portion, including the effect on the total impedance of those tuning capacitors or those tuning resistors that are electrically connected in parallel to either one of the low voltage capacitor or the low voltage resistor. The common total impedance also includes the effect on any resistor or impedance that may be electrically connected to any of the low voltage capacitors and the effect of any capacitor or impedance that may be electrically connected to any of the low voltage resistors.

The voltage division ratio T of the voltage divider is a dimensionless number obtained by dividing the sum of the total impedances of the high voltage part and the low voltage part by the value of the common total impedance of the low voltage part as follows: t ═ Z_LV+Z_HV)/Z_LV. For a given temperature of the voltage divider and a given frequency of the AC voltage, it is assumed that the high voltage part of the voltage divider has a fixed impedance Z_HV. In order to obtain a voltage divider with a desired voltage division ratio T, the common total impedance Z of the low voltage parts is adjusted_LVSuitably adjusted to the desired impedance Z_LVSuch that (Z)_LV*+Z_HV)/Z_LVEqual to the desired partial pressure ratio T. To Z_LVThis adjustment of (2) is done by increasing the impedance of selected ones of the adjusting capacitors or adjusting resistors to the impedance of the low voltage part, which in turn is done by bringing the respective associated switches of these selected adjusting capacitors/resistors into a connected state of the switches. The closing of these switches makes these regulating capacitors/resistors lowPressing a portion of the section.

In certain embodiments of the voltage sensor according to the present disclosure, the plurality of tuning capacitors comprises at least four tuning capacitors, or wherein the plurality of tuning capacitors comprises at least ten tuning capacitors. In certain embodiments of the voltage sensor according to the present disclosure, the plurality of tuning resistors comprises at least four tuning resistors, or wherein the plurality of tuning resistors comprises at least ten tuning resistors. The larger the number of adjusting capacitors/resistors can allow the finer the adjustment of the common total impedance of the low voltage part and thus the finer the adjustment of the voltage division ratio of the voltage divider.

In certain embodiments of the voltage sensor according to the present disclosure, each regulation capacitor is associated with one switch, and each switch is associated with one regulation capacitor. In certain embodiments of the voltage sensor according to the present disclosure, each of the adjustment resistors is associated with one of the switches, and each of the switches is associated with one of the adjustment resistors. The one-to-one assignment may facilitate greater control over the adjustment of the total impedance of the low voltage portion. It may also make the layout of the corresponding circuit easier.

In certain embodiments of the voltage sensor according to the present disclosure, two switches are associated with one regulating capacitor, such that each of the two switches is capable of connecting the regulating capacitor in parallel to at least one of the one or more low voltage capacitors. In certain embodiments of the voltage sensor according to the present disclosure, two switches are associated with one regulating resistor, such that each of the two switches may connect the regulating resistor in parallel to at least one of the one or more low voltage resistors. This may provide redundancy in case of failure of one switch. This in turn may enhance the reliability of the voltage sensor.

In certain embodiments of the voltage sensor according to the present disclosure, each of the tuning capacitors has a capacitance between 0.05% and 20.00% of the combined capacitance of the one or more low-voltage capacitors. In certain embodiments of the voltage sensor according to the present disclosure, each of the adjustment resistors has a resistance between 0.05% and 20.00% of the combined resistance of the one or more low voltage resistors. A tuning capacitor/resistor with a capacitance/resistance in this range may be particularly suitable for providing a wide range of tuning possibilities of the common total impedance of the low voltage part of the voltage divider at both coarser and fine granularity. This may enhance the versatility of the voltage sensor or may allow the use of cheaper, lower accuracy low voltage capacitors/resistors or cheaper, lower accuracy high voltage capacitors/resistors.

The term "impedance element" is used herein to refer collectively to capacitors and resistors as well as inductances. Thus, more generally, in certain embodiments of the voltage sensor according to the present disclosure, each conditioning impedance element has an electrical impedance of between 0.05% and 20.00% of the combined impedance of the one or more low voltage impedances. A tuning impedance element with an electrical impedance in this range may be particularly suitable for providing a wide range of tuning possibilities of the common total impedance of the low voltage part of the voltage divider at both coarser and fine granularity. This may enhance the versatility of the voltage sensor or may allow the use of cheaper, lower accuracy low voltage impedance elements or cheaper, lower accuracy high voltage impedance elements.

In certain embodiments of the voltage sensor according to the present disclosure, each of the tuning capacitors has a capacitance between 0.2 nanofarad (nF) and 50 nF. Such a regulating capacitor may be particularly advantageous when regulating the voltage division ratio of a voltage divider in a network, where the AC voltages have a common amplitude (e.g. 12kV) and the signal voltage is considered to be in the usually required range of e.g. between 1 and 10 volts.

The so-called "E series" is a system that derives preferred values for use in electronic components. The "E series" consists of the E1, E3, E6, E12, E24, E48, E96, and E192 series, where the numbers following "E" represent the number of median "stages" in each series. While it is theoretically possible to produce any number of components, the need for inventory simplification in practice has led the industry to identify E-series for resistors, capacitors and inductors. The preferred number of E-series is selected so that when the part is manufactured it will end up within a range of approximately equally spaced values on a logarithmic scale. Each E series subdivides the interval from 1 to 10 (decimal) into stages 3, 6, 12, 24, 48, 96, 192. Exemplary E6 series use values of 1.0, 1.5, 2.2, 3.3, 4.7, and 6.8.

In certain embodiments of the voltage sensor according to the present disclosure, the capacitances of the tuning capacitors are equally spaced on a logarithmic scale. In some of these embodiments, the capacitance values of the tuning capacitors are equally spaced on a logarithmic scale, such as represented by the E6 series. In certain embodiments of the voltage sensor according to the present disclosure, the resistance values of the tuning resistors are equally spaced on a logarithmic scale. In some of these embodiments, the resistance of the tuning resistors are equally spaced on a logarithmic scale, such as that represented by the E6 series.

In certain embodiments of the voltage sensor according to the present disclosure, each of the tuning capacitors has a capacitance that is different from the respective capacitances of all of the other tuning capacitors. In certain embodiments of the voltage sensor according to the present disclosure, each of the adjustment resistors has a resistance that is different from the respective resistances of all of the other adjustment resistors. This may allow for finer granularity and accuracy in adjusting the total impedance of the low voltage portion and the voltage division ratio of the voltage divider.

According to the present disclosure, the total impedance of the high voltage part and the total impedance of the low voltage part of the voltage divider are adapted such that by bringing one or more of the switches into a connected state of the switch, the voltage divider has a voltage division ratio of 3077 ± 0.5%, or 6154 ± 0.5%, or 6769 ± 0.5%, or 10000 ± 0.5% for an AC voltage between 5kV and 25kV single phase ground and a frequency between 40 hertz and 70 hertz.

These voltage division ratios help to provide signal voltages that can be processed with existing off-the-shelf equipment and thereby help to meet major market demands. Generally, an RTU (remote terminal unit) processes a signal voltage of a voltage sensor according to the present disclosure, the signal voltage being an input voltage of the RTU. Many common RTUs are designed to handle an input voltage of 2.00 volts at a nominal AC boost voltage of 20kV at a nominal AC frequency of 50 hertz, or to handle an input voltage of 3.25 volts at a nominal AC boost voltage of 20kV at a nominal AC frequency of 50 hertz, or to handle a specific input voltage of 6.50 volts or 2.95 volts at a nominal AC boost voltage of 20kV at a nominal AC frequency of 50 hertz. To be compatible with such common RTUs and therefore more versatile, the voltage divider of the sensor may advantageously be set to a specific voltage division ratio using switches, i.e. at least to the following voltage division ratios: 3077 (for an RTU input voltage of 6.50 volts at a nominal AC voltage of 20000 volts and a nominal AC frequency of 50 hertz), 6154 (for an RTU input voltage of 3.25 volts at a nominal AC voltage of 20000 volts and a nominal AC frequency of 50 hertz), 6769 (for an RTU input voltage of 2.95 volts at a nominal AC voltage of 20000 volts and a nominal AC frequency of 50 hertz) or 10000 (for an RTU input voltage of 2.00 volts at a nominal AC voltage of 20000 volts and a nominal AC frequency of 50 hertz). These particular voltage division ratios are advantageous for any type of voltage divider comprised in the sensor, i.e. for capacitive voltage dividers as described herein, resistive voltage dividers as described herein, hybrid (capacitive-resistive) voltage dividers or other types of voltage dividers.

In certain of these embodiments, the true partial pressure ratio T is within 0.5% of the desired partial pressure ratio T, wherein this accuracy is obtained by: selecting a suitable accuracy level of the low-voltage capacitor and a suitable set of tuning capacitors, and using a switch to connect in parallel the suitable one of the tuning capacitors to the low-voltage capacitor. In certain of these embodiments, the true partial pressure ratio T is within 0.5% of the desired partial pressure ratio T, wherein this accuracy is obtained by: selecting a suitable precision level of the low voltage resistor and a suitable set of tuning resistors, and using a switch to connect a suitable one of the tuning resistors in parallel to the low voltage resistor.

For certain metering applications, particularly in europe, a signal voltage of about 100 volts may be required, with the AC voltage to be sensed being about 10kV single-phase ground at a frequency of 50 hertz. This requirement translates into a desired partial pressure ratio T of about 100.

The range of partial pressure ratios that may be desired is quite broad, i.e., from about 100 and below 100 to about 10000 and above 10000. Traditionally, manufacturers of voltage sensors have covered this range by providing different types of voltage sensors, the types having different hardware configurations and providing different voltage division ratios within the range, and each type facilitating voltage division ratio adjustment at limited intervals.

However, the present disclosure provides a voltage sensor that can cover a wide range of voltage division ratios with a single hardware configuration, allowing manufacturers to reduce the number of inventory items and achieve cost advantages.

Thus, in certain embodiments of the voltage sensor according to the present disclosure, the total impedance of the high voltage part and the total impedance of the low voltage part of the voltage divider are adapted such that for a 10kV single-phase grounded AC voltage and a frequency of 50 hertz, the voltage divider has a voltage division ratio of 10 ± 0.5% or less when one or more of the plurality of switches is in the disconnected state of the switch, and a voltage division ratio of 10000 ± 0.5% or more when at least one of these one or more of the plurality of switches is in the connected state of the switch.

A voltage sensor as described herein may have an output impedance that varies with the voltage division ratio and an associated common total impedance of the low voltage portion determined by the particular combination of connected and disconnected switches. Each output impedance is related to an allowable load impedance, i.e., an allowable sum of impedances of all equipment connected to the signal contact, such as signal cables, connectors, voltage measuring devices like RTUs, etc. When the voltage sensor is a passive voltage divider, the accuracy of the voltage division ratio of the sensor depends on the load impedance.

To reduce this dependency, the sensor may further comprise an impedance correction circuit. Such impedance correction circuitry may include, for example, an operational amplifier. In order for the signal voltage to remain "clean" and in order not to amplify noise together with the signal voltage, the operational amplifier may be a non-inverting operational amplifier with an amplification factor of 1. A suitably selected operational amplifier provides the sensor output signal, for example to a Remote Terminal Unit (RTU) which processes the sensor output signal, the operational amplifier having a low output impedance. The impedance correction circuit is advantageously arranged close to the signal contacts (e.g. within a few centimeters or very few centimeters) to keep the connection lines between the signal contacts and the circuit short circuits and their impedance negligible. The low output impedance facilitates the use of longer wires or cables that transmit the sensor output signal from the impedance correction circuit to the remote terminal unit.

Thus, in general, a voltage sensor according to the present disclosure may further include a non-inverting operational amplifier for providing a sensor output signal at a low output impedance, the input of the operational amplifier being electrically connected to the signal contact.

In certain embodiments of the voltage sensor according to the present disclosure, after bringing at least one switch of the plurality of switches into the connected state of the switch, it is impossible to bring the switch from the connected state of the switch into the disconnected state of the switch. In certain instances, irreversible adjustment can help avoid tampering, as well as intentional tampering after installation, other intentional or accidental misadjustments.

In certain embodiments of the voltage sensor according to the present disclosure, at least one of the switches is externally accessible. In case the elements of the voltage sensor are encapsulated, for example in a cured resin or in a rubber body or an EPDM body, the encapsulating structure may comprise, for example, a window, a recess or an opening to allow access to the at least one switch from outside the encapsulating structure. This may allow adjusting the common total impedance of the low voltage parts (and thus the voltage division ratio of the voltage divider) after manufacturing or during or after mounting the voltage sensor. For the same reason, in some of these embodiments, all switches are externally accessible.

In certain embodiments of the voltage sensor according to the present disclosure, at least one of the switches is a dip switch. Dip switches are widely available at low cost and are reliable enough for many applications, and therefore their use may facilitate cost-effective manufacturing.

In certain embodiments of the voltage sensor according to the present disclosure, at least one switch of the plurality of switches is adapted and/or arranged such that the switch can be brought into the connected state manually or by a robotic actuator or by pneumatic force. The possibility of manual adjustment provides greater flexibility in the manner and time in which the switch may be actuated. In certain situations, tool-less operation of the switch is desirable. On the other hand, robotic actuation or pneumatic actuation may facilitate automated manufacturing of the voltage sensor and may result in a more cost-effective manufacturing or calibration/adjustment process.

In certain embodiments of the voltage sensor according to the present disclosure, the regulating capacitor and the switch are disposed on a printed circuit board. In certain embodiments of the voltage sensor according to the present disclosure, the regulating resistor and the switch are disposed on a printed circuit board. The arrangement on the PCB may help to provide a robust support for the capacitors and switches. Furthermore, PCBs are widely available and the circuitry can be manufactured on the PCB at low cost, resulting in lower manufacturing costs for the voltage sensor.

In certain embodiments of the voltage sensor according to the present disclosure, the printed circuit board has an elongated shape such that it can be accommodated in the cable. Housing in a cable may save space and may help provide environmental protection for the PCB and electrical components disposed on the PCB.

In certain embodiments of a voltage sensor according to the present disclosure, a printed circuit board has output pads arranged and shaped to be soldered to pins of a connector (e.g., an M12 connector). The direct mechanical and electrical connection of the PCB to the connector may render the use of intermediate cables obsolete and may thereby help to reduce the number of soldering points and improve the mechanical stability of the assembly of the PCB and the connector, thereby improving the reliability of the voltage sensor.

In certain embodiments of the voltage sensor according to the present disclosure, the printed circuit board has a strain relief slot to engage with a strength member or shield of the cable. The integrated strain relief feature takes mechanical load of the solder joint and thereby potentially improves solder joint life and reliability of the voltage sensor assembly.

The invention also provides an electrical power network for distributing electrical power in a national electrical grid, the electrical power network comprising HV/MV power conductors and a voltage sensor as described herein electrically connected to the power conductors to sense AC voltages of the power conductors. Due to accurate knowledge about the voltages in certain power conductors of the network, a power network incorporating voltage sensors as described herein may be operated more efficiently.

The present invention also provides a method of adjusting the common total impedance of the low voltage part of a voltage divider of a voltage sensor as described herein to a desired impedance, the method comprising the step of bringing at least one of the switches into a connected state or into a disconnected state.

Drawings

The following figures illustrate particular embodiments of the invention:

FIG. 1 is a circuit diagram of a capacitive voltage sensor according to the present disclosure;

FIG. 2 is a perspective view of a calibration unit for a sensor according to the present disclosure;

FIG. 3 is a perspective view of a PCB of a voltage sensor according to the present disclosure soldered to a connector;

FIG. 4 is a circuit diagram of a resistive voltage sensor according to the present disclosure; and is

Fig. 5 is a circuit diagram of a capacitive voltage sensor including an impedance correction circuit according to the present disclosure.

Detailed Description

In the circuit diagram of fig. 1, a capacitive voltage sensor 1 according to the present disclosure is shown. The capacitive voltage sensor is used for sensing the AC voltage of a high voltage power cable 10, which is shown in cross-section in fig. 1. The cable 10 has a center conductor 20 surrounded by an insulating layer 30. In use, the center conductor 20 conducts electricity in a national grid at an AC voltage of 12 kilovolts (kV) and a current of several hundred amperes.

The voltage sensor 1 is electrically connected to the central conductor 20 in order to sense the AC voltage of the conductor 20. For this sensing, the voltage sensor 1 comprises a voltage divider 40, which in turn consists of a high voltage part 50 and a low voltage part 60. The high voltage part 50 is electrically connected between the AC voltage of the center conductor 20 of the power cable 10 and the low voltage part 60, and includes four high voltage capacitors 70 electrically connected in series with each other.

The low voltage part 60 is electrically connected between the high voltage part 50 and the electrical ground 100 and comprises two low voltage capacitors 110 which are electrically connected between the high voltage part 50 and the ground 100 and are connected in series with each other.

The divided voltage or "signal voltage" may be picked up at a signal contact 120 electrically positioned between the high voltage portion 50 and the low voltage portion 60. The signal voltage is indicative of the AC voltage of conductor 20 and varies in proportion to the AC voltage, the scale factor being the division ratio of voltage divider 40. A voltage measuring device 130 is connected between the signal contact 120 and the ground 100 to measure the signal voltage. The value of the AC voltage is obtained by multiplying the signal voltage by the voltage division ratio.

The low voltage portion 60 also includes ten conditioning capacitors 80 and ten switches 90 in a particular configuration: each regulating capacitor 80 can be connected in parallel to the low voltage capacitor 110 by closing the switch 90 associated with the regulating capacitor 80.

In the embodiment shown in fig. 1, each regulating capacitor 80 has one switch 90 associated with it: the associated switch 90 of the regulating capacitor 80 is a switch 90 which, when closed (i.e. when brought into its "connected state"), electrically connects the regulating capacitor 80 in parallel to the low voltage capacitor 110. For example, one of the switches 90 associated with the conditioning capacitor 80a is the switch 90a because when the switch is closed, the switch connects the conditioning capacitor 80a in parallel to the low voltage capacitor 110. The switch 90 is a dip switch which can be brought from its disconnected state into its connected state manually or by an automated tool, for example by a tool operated by a robot or by a pneumatic cylinder mechanism.

In addition to switch 90b, switch 90 is shown in a disconnected state of the switch disconnecting one electrode of the conditioning capacitor 80 respectively associated with the switch from the low voltage capacitor 110. Considering the impedance of the high voltage part 50, the impedance of the low voltage part 60 is the combined impedance of the low voltage capacitors 110 before closing the switch 90b, which results in a certain voltage division ratio of the voltage divider 40. After closing the switch 90b, the impedance of the regulating capacitor 80b, now connected in parallel to the low-voltage capacitor 110, increases to the combined impedance of the low-voltage capacitor 110 according to the known laws of electricity, resulting in a smaller total impedance of the low-voltage part 60 and a larger voltage division ratio T.

In order to facilitate the meeting of the specified voltage division ratio, the adjusting capacitors 80 have different individual capacitances and thus different individual impedances. Starting from the combined impedance of the low-voltage capacitors 110, an increase of a smaller impedance may be sufficient to obtain a defined voltage division ratio. The user may then choose to connect a selected one of the ten tuning capacitors 80 in parallel to the low voltage capacitor 110, the tuning capacitor 80 having a suitably small additional impedance for the low voltage portion 60 to have a suitable total impedance to provide the voltage divider 40 with the specified division ratio.

Obviously, not only a single regulating capacitor 90 may be added, but also two or three or four, etc. or all of the switches 90 may be brought into the connection state of the switch to connect their associated regulating capacitors 90 in parallel to the low-voltage capacitor 110.

In an alternative embodiment, the low voltage portion 60 includes twelve regulating capacitors 80. Two of these regulating capacitors 80 may have individual capacitances in order to bring the voltage division ratio approximately close to the specific desired voltage division ratio T, for example, T100 or T3077 or T6154 or T6769 or T10000, but slightly below the specific desired voltage division ratio. Two switches, each defining two states, provide four different switch combinations. In certain embodiments, each switching combination brings the voltage division ratio approximately close to one of four particular desired voltage division ratios T.

The remaining ten regulating capacitors 80 have individual capacitances that are appropriately selected to match the desired voltage division ratio with an accuracy of 1%, 0.5%, or 0.2%. In order to minimize the number of parts, the values of the capacitances of these adjustment capacitors 80 are chosen such that their nominal capacitance values are equally spaced on a logarithmic scale, for example represented by the E6 series.

By connecting the high voltage part of the voltage sensor 1 of fig. 1 to a well known AC voltage having a desired operating frequency and a desired operating temperature, the voltage sensor can be set at manufacture to a given desired voltage division ratio, with all switches 90 in the disconnected state of the switches. The appropriate switch 90 (switch or switches) will then be brought into its connected state so that the signal voltage as measured by the voltage measuring device 130 is at a voltage equal to the known AC voltage multiplied by the desired voltage division ratio.

The low voltage capacitor 110, the regulating capacitor 80 and the switch 90 may be arranged on a Printed Circuit Board (PCB), which may be located at a distance from the physical location of the high voltage part 60. Alternatively, only the adjustment capacitor 80 and the switch 90 may be disposed on the printed circuit board. The PCB may be positioned at a distance from the physical location of the low voltage capacitor 110. A signal cable indicated by 140 may direct signal lines from the signal contact 120 and the sensor ground 100 from the output of the low voltage capacitor 110 to the PCB, and an output cable 150 may direct lines from the PCB output to the voltage measurement device 130.

In certain embodiments, the conditioning capacitor 80 and the switch 90 are grouped in close physical proximity to each other and form a "calibration unit". This calibration unit may comprise a Printed Circuit Board (PCB) on which the adjusting capacitor 80 and the switch 90 are arranged and supported.

Fig. 2 shows a calibration unit 200 as described above in a perspective view. The calibration unit includes a PCB 210 of a generally elongated shape. The twelve dip switches 91 are arranged in a row, each switch 91 being associated with a corresponding regulating capacitor, which is arranged below the switch 91 and is therefore not visible in fig. 2. The regulating capacitors and the switches 91 are electrically arranged as shown in fig. 1, so that each switch 91 can be brought into a connected state, in which it connects its associated regulating capacitor in parallel to one or more low-voltage capacitors 110.

The calibration unit 200 is suitably shaped to be accommodated in the output cable of the voltage sensor 1. The first end portion 220 of the PCB 210 has means to connect to a signal line (carrying the signal voltage of the signal contact 120 of the voltage divider 40) and a ground line in the signal cable 140. The signal wire may be soldered to the signal wire soldering point 230, and the ground wire may be soldered to the ground wire soldering point 240. From these solder joints 230, 240, conductive traces 280 on the PCB 210 lead to the tuning capacitor 80 and the switch 90, as shown in fig. 1.

The strain relief slots 250 and strain relief openings 260 in the PCB 210 may receive and grip end portions of a shielding mesh (not shown) of the signal cable 140 to provide strain relief for the signal cable 140.

At an opposite second end portion 270 of PCB 210, voltage measuring device 130 is connected to a set of conditioning capacitors 80 and switches 90 on PCB 210 via output cables 150. To connect the two wires of the output cable 150 (for ground and for signal voltage), two contact pads 290 are placed at the distal edge of the PCB 210. Contact pads 290 are connected to the set of tuning capacitors 80 and switches 90 on PCB 210 via conductive traces 300.

It is often necessary to connect the voltage sensor to the measuring device 130 and/or the processing unit via a so-called M12 connector. As shown in the perspective semi-transparent view of fig. 3, the exemplary connector 310 includes a central wire member 320 and a threaded cap nut 330 that encapsulates the wire member 320, and a connector sleeve 340 for covering the electrical connections of the wire member 320. To avoid additional wires leading from the PCB 210 to the central wiring member 320 of the connector 310, the second end portion 270 of the PCB 210 is suitably shaped to allow the cap nut 330 and the connector sleeve 340 to slide over the second end portion. Thus, the second end portion 270 is shaped to form a narrow protrusion that is long enough to extend into the M12 connector 310 up to the wiring member 320 of the connector. The contact pads 290 on the PCB 210 are suitably spaced apart so that they can be soldered directly to two corresponding contact pins 350 of the wiring member 320. This direct connection of the conditioning capacitor 80 and its associated switch 91 to the connector 310 causes the output cable 150 between the PCB 210 and the connector 310 to be discarded.

In the circuit diagram of fig. 4, a resistive voltage sensor 2 according to the present disclosure is shown. The resistive voltage sensor is used to sense the AC voltage of a high voltage power cable 10, which is shown in cross-section in fig. 4. The cable 10 has a center conductor 20 surrounded by an insulating layer 30, as described above for fig. 1.

The voltage sensor 2 is electrically connected to the central conductor 20 in order to sense the AC voltage of the conductor 20. For this sensing, the voltage sensor 2 comprises a resistive voltage divider 41, which in turn is composed of a high voltage part 50 and a low voltage part 60. The high voltage part 50 is electrically connected between the AC voltage of the center conductor 20 of the power cable 10 and the low voltage part 60, and includes four high voltage resistors 71 electrically connected in series with each other.

The low-voltage portion 60 is electrically connected between the high-voltage portion 50 and the electrical ground 100 and comprises two low-voltage resistors 111 electrically connected between the high-voltage portion 50 and the ground 100 and connected in series with each other.

As described above for fig. 1, a divided voltage or "signal voltage" may be picked up at the signal contact 120 that is electrically positioned between the high voltage portion 50 and the low voltage portion 60.

The low voltage part 60 also comprises ten regulating resistors 81 and ten switches 90 in a specific configuration: each of the trimming resistors 81 may be connected in parallel to a low voltage resistor 111 by closing the switch 90 associated with the trimming resistor 81.

In the embodiment shown in fig. 4, each regulating resistor 81 has exactly one switch 90 associated with it: the associated switch 90 of the adjusting resistor 81 is a switch 90 which, when closed (i.e. when brought into its "connected state"), electrically connects the adjusting resistor 81 in parallel to a low voltage resistor 111. For example, one of the switches 90 associated with the regulating resistor 81a is the switch 90a because when the switch is closed, it connects the regulating resistor 81a in parallel to the low voltage resistor 111. The switch 90 is a dip switch which can be brought from its disconnected state into its connected state manually or by an automated tool, for example by a tool operated by a robot or by a pneumatic cylinder mechanism.

In addition to switch 90b, switch 90 is shown in a disconnected state of the switch disconnecting one contact of the regulating resistor 81 associated with the switch from the low voltage resistor 111, respectively. Considering the impedance of the high voltage part 50, the impedance of the low voltage part 60 is the combined impedance of the low voltage resistors 111 before closing the switch 90b, which results in a certain voltage division ratio of the voltage divider 41. After closing the switch 90b, the impedance of the adjusting resistor 80b, now connected in parallel to the low-voltage resistor 111, increases to the combined impedance of the low-voltage resistor 111 according to the known law of electricity, resulting in a smaller total impedance and a larger voltage division ratio T of the low-voltage portion 60.

In order to facilitate the meeting of the specified voltage division ratio, the adjusting resistors 81 have different individual resistances and thus different individual impedances. Starting from the combined impedance of the low voltage resistors 111, a smaller increase in impedance may be sufficient to obtain the specified voltage division ratio. The user may then choose to connect a selected one of the ten adjusting resistors 81 in parallel to the low voltage resistor 111, the adjusting resistor 81 having a suitably small additional impedance for the low voltage portion 60 to have a suitable total impedance to provide the voltage divider 40 with the specified division ratio.

Obviously, not only a single adjusting resistor 81 may be added, but also two or three or four, etc. or all of the switches 90 may be brought into the connected state of the switch to connect their associated adjusting resistors 81 in parallel to the low voltage resistor 111.

By connecting the high voltage part of the voltage sensor 2 of fig. 4 to a well known AC voltage having a desired operating frequency and a desired operating temperature, the voltage sensor can be set at manufacture to a given desired voltage division ratio, with all switches 90 in their disconnected state. The appropriate switch 90 (switch or switches) will then be brought into its connected state so that the signal voltage as measured by the voltage measuring device 130 is at a voltage equal to the known AC voltage multiplied by the desired voltage division ratio.

The low voltage resistor 111, the regulating resistor 81 and the switch 90 may be arranged on a Printed Circuit Board (PCB), which may be located at a distance from the physical location of the high voltage part 60. Alternatively, only the adjusting resistor 81 and the switch 90 may be disposed on the printed circuit board. The PCB may be located at a distance from the physical location of the low voltage resistor 111. A signal cable indicated by 140 may direct signal lines from the signal contact 120 and the sensor ground 100 from the output of the low voltage resistor 111 to the PCB, and an output cable 150 may direct lines from the PCB output to the voltage measurement device 130.

In certain embodiments, the adjustment resistor 81 and the switch 90 are grouped in close physical proximity to each other and form a "calibration unit". This calibration unit may comprise a Printed Circuit Board (PCB) on which the adjusting resistor 81 and the switch 90 are arranged and supported.

Fig. 5 is a circuit diagram of a further capacitive voltage sensor 3 according to the present disclosure. The capacitive voltage sensor is the same as the voltage sensor of fig. 1 except that it comprises an impedance correction circuit 360 for reducing the dependence of the sensing accuracy of the voltage sensor 3 on the load impedance. The impedance correction circuit 360 includes a measurement resistor 370 and a measurement capacitor 380 that are electrically connected in parallel with each other between the signal contact 120 and the ground 100. The signal voltage is fed into the non-inverting input 390 of the operational amplifier 400, while the inverting input 410 is connected with the output 420 of the amplifier 400, resulting in an amplifier gain of 1. The unmodified signal voltage from the output 420 of the operational amplifier is transmitted to the voltage measuring device 130.

The operational amplifier 400 is a non-inverting operational amplifier having an amplification factor of 1 so that the signal voltage remains "clean" and noise is not amplified together with the signal voltage. The operational amplifier 400 is suitably selected to provide a sensor output signal to the voltage measurement device 130, which processes the sensor output signal. Operational amplifier 400 has a low output impedance so that the sensor output signal can be transmitted from amplifier output 420 to voltage measurement device 130 via a longer line. The impedance correction circuit 360 is disposed close to the signal contact 120 (e.g., within a few centimeters or very few centimeters) to keep the connecting lines between the signal contact 120 and the circuit 360 short and their impedance negligible. The low output impedance of amplifier 400 facilitates the use of a longer output cable 150 that transmits the sensor output signal from impedance correction circuit 360 to voltage measurement device 130.

In the high voltage portion 50 of the voltage sensor 3, the high voltage capacitor 70 has a combined total impedance of 36 picofarads, while the low voltage capacitor 110 has a combined total impedance of 3.4985 nanofarads (the measurement capacitor 380 has a capacitance of about 50 picofarads and has no significant effect on the total impedance of the low voltage portion 60). The voltage divider ratio of the voltage divider 40 is therefore about 100. An AC input voltage of 10 kilovolts at power conductor 20 produces a signal voltage of about 100 volts at voltage measuring device 130. Signal voltages in the range of 100 volts are in line with the requirements of some power utility companies for metering applications in their power networks.

Claims (18)

1. A voltage sensor (1) for sensing an AC voltage of an HV/MV power conductor (20), the voltage sensor comprising a capacitive voltage divider (40) for sensing the AC voltage, the voltage divider comprising

-a high voltage part (50) comprising one or more high voltage capacitors (70) electrically connected in series with each other;

-a low voltage portion (60) comprising one or more low voltage capacitors (110) electrically connected in series with each other between the high voltage portion (50) and an electrical ground (100);

-a signal contact (120) electrically arranged between the high voltage part (50) and the low voltage part (60) for providing a signal voltage indicative of the AC voltage,

wherein the low voltage part (60) further comprises a plurality of regulating capacitors (80) and a plurality of switches (90) for regulating the common total impedance of the low voltage part to a desired impedance, wherein each switch (90) is associated with and electrically connected to one or more of the regulating capacitors (80) and is capable of bringing the switch (90) into a connected state and into a disconnected state such that the switch (90)

-electrically connecting in parallel, in the connected state of the switch, the regulating capacitor (80) associated with the switch to at least one of the one or more low-voltage capacitors (110);

-electrically disconnecting at least one electrode of the regulating capacitor (80) associated with the switch from the low voltage capacitor (110) in the disconnected state of the switch, in the connected state of the switch the associated regulating capacitor (80) being connected to the low voltage capacitor,

and wherein the total impedance of the high voltage part (50) and the total impedance of the low voltage part (60) of the voltage divider (40) are adapted such that by bringing one or more of the switches (90) into a connected state of the switches, the voltage divider (40) has a voltage division ratio of 3077 ± 0.5% or 6154 ± 0.5% or 6769 ± 0.5% or 10000 ± 0.5% for single-phase grounded AC voltages between 5kV and 25kV and frequencies between 40 hertz and 70 hertz.

2. The voltage sensor of claim 1, wherein the plurality of adjustment capacitors (80) comprises at least four adjustment capacitors (80), or wherein the plurality of adjustment capacitors (80) comprises at least ten adjustment capacitors (80).

3. Voltage sensor according to claim 1 or claim 2, wherein each regulating capacitor (80) is associated with one switch (90), and wherein each switch (90) is associated with one regulating capacitor (80).

4. Voltage sensor according to any of the preceding claims, wherein two switches (90) are associated with one regulation capacitor (80), such that each of the two switches (90) is capable of connecting the regulation capacitor (80) in parallel to at least one of the one or more low voltage capacitors (110).

5. Voltage sensor according to any one of the preceding claims, wherein each conditioning capacitor (80) has a capacitance of between 0.05% and 20.00% of the combined capacitance of the one or more low voltage capacitors.

6. Voltage sensor according to any one of the preceding claims, wherein the nominal capacitance values of the adjustment capacitors (80) are equally spaced on a logarithmic scale, for example represented by the E6 series.

7. Voltage sensor according to any of the preceding claims, wherein the total impedance of the high voltage part (50) and the total impedance of the low voltage part (60) of the voltage divider (40) are adapted such that for a 10kV single phase grounded AC voltage and a frequency of 50 hz, the voltage divider (40) has a voltage division ratio of 10 ± 0.5% or less when one or more of the plurality of switches (90) is in the disconnected state of the switch, and a voltage division ratio of 10000 ± 0.5% or more when at least one of these one or more of the plurality of switches (90) is in the connected state of the switch.

8. The voltage sensor of any of the preceding claims, further comprising a non-inverting operational amplifier (400) for providing a sensor output signal at a low output impedance, an input (390) of the operational amplifier being electrically connected to the signal contact (120).

9. Voltage sensor according to any of the preceding claims, wherein the switch cannot be brought from its connected state into its disconnected state after bringing at least one switch (90) of the plurality of switches (90) into its connected state.

10. Voltage sensor according to any one of the preceding claims, wherein at least one of the switches (90) is externally accessible.

11. Voltage sensor according to any of the preceding claims, wherein at least one switch (90) of the plurality of switches (90) is adapted and/or arranged such that the switch can be brought into a connected state manually or by a robotic actuator or by pneumatic force.

12. Voltage sensor according to any of the preceding claims, wherein the regulating capacitor (80) and the switch (90) are arranged on a printed circuit board (210).

13. The voltage sensor of claim 12, wherein the printed circuit board (210) has an elongated shape such that the printed circuit board can be accommodated in a cable.

14. Voltage sensor according to claim 12 or 13, wherein the printed circuit board (210) has output pads (290) arranged and shaped to be soldered to pins (320) of a connector (310), such as an M12 connector.

15. The voltage sensor of any of claims 12-14, wherein the printed circuit board (210) has a strain relief slot (250) to engage with a strength member or shield of a cable.

16. A voltage sensor (2) for sensing an AC voltage of a HV/MV power conductor (20), the voltage sensor comprising a resistive voltage divider (41) for sensing the AC voltage, the voltage divider comprising

-a high voltage part (50) comprising one or more high voltage resistors (71) electrically connected in series with each other;

-a low voltage portion (60) comprising one or more low voltage resistors (111) electrically connected in series with each other between the high voltage portion (50) and an electrical ground (100);

-a signal contact (120) electrically arranged between the high voltage part (50) and the low voltage part (60) for providing a signal voltage indicative of the AC voltage,

characterized in that the low-voltage part (60) further comprises a plurality of adjusting resistors (81) and a plurality of switches (90) for adjusting the common total impedance of the low-voltage part to a desired impedance, wherein each switch (90) is associated with and electrically connected to one or more of the adjusting resistors (81) and is capable of bringing the switch into a connected state and into a disconnected state such that the switch (90)

-electrically connecting in parallel, in the connected state of the switch, the regulating resistor (81) associated with the switch to at least one of the one or more low voltage resistors (111);

-electrically disconnecting at least one contact of the regulating resistor (81) associated with the switch from the low voltage resistor (111) in the disconnected state of the switch, in the connected state of the switch the associated regulating resistor (81) being connected to the low voltage resistor,

wherein the total impedance of the high voltage part (50) and the total impedance of the low voltage part (60) of the voltage divider (41) are adapted such that by bringing one or more of the switches (90) into a connected state of the switches, the voltage divider (41) has a voltage division ratio of 3077 ± 0.5% or 6154 ± 0.5% or 6769 ± 0.5% or 10000 ± 0.5% for single-phase grounded AC voltages between 5kV and 25kV and frequencies between 40 hertz and 70 hertz.

17. An electric power network for distributing electric power in a national electric power network, the electric power network comprising a HV/MV power conductor (20) and a voltage sensor (1) according to any one of the preceding claims, the voltage sensor being electrically connected to the power conductor for sensing an AC voltage of the power conductor.

18. A method of adjusting the common total impedance of the low voltage parts (60) of the voltage divider (40, 41) of the voltage sensor (1, 2) according to any of claims 1 to 15 to a desired impedance, the method comprising the step of bringing at least one of the switches (90) into a connected state or into a disconnected state.

Images