ELECTRICAL SWITCH FOR HIGH VOLTAGE WITH INTEGRATED FAULT DETECTOR, METHOD FOR DETECTING A FAULT OF THE HIGH VOLTAGE SWITCH AND USE OF THE HIGH VOLTAGE SWITCH

Description

[0001] The invention relates to an electrical switching device for high voltage with an integrated fault detector. In addition, a method for detecting a fault in the electrical switching device for high voltage and a use of the electrical switching device for high voltage are described.

[0002] A high-voltage electrical switching device is a switch for switching an electric current with an alternating voltage exceeding 1 kV. One of the most frequent sources of failure in a switchgear assembly containing such a device is the high-voltage components of the switching device located within the assembly, in the form of screw connections. A screw connection that is only installed at a specific location within the switchgear assembly carries a particularly high risk of failure.

[0003] A screw connection on the electrical switching device, which connects a busbar to a high-voltage cable, plays a crucial role. Such a screw connection can deteriorate during operation, especially if improperly installed, causing additional local heating at the connection. This can lead to a deviation from the switching device's normal operating temperature and ultimately to its failure.

[0004] To assess the failure risk of the electrical switching device with the screw connection due to heating of the screw connection, measuring the temperature at the screw connection is crucial. A temperature sensor is required for this purpose. The temperature sensor acts as a fault detector, allowing any anomalies in the temperature at the screw connection to be detected.

[0005] From DE 10 2014 102509 A1, a method for determining the temperature in the area of ​​a high-voltage conductor of such a switching device is known using a temperature sensor. The temperature of the high-voltage conductor is then inferred from the determined (measured) temperature.

[0006] However, measuring the temperature at the screw connection is difficult because the electrical switching device is difficult to retrofit for an advantageous positioning of a suitable temperature sensor (e.g. SAW (Surface Acoustic Wafe) sensor or PT1000 (resistance thermometer)) near the screw connection.

[0007] The object of the present invention is to demonstrate how an electrical switching device for high voltage can be equipped with a fault detector without having to attach a separate component for a fault detector.

[0008] To solve the problem, an electrical switching device for high voltage is specified, comprising at least one field control electrode for field control of at least one high-voltage component of the electrical switching device and at least one fault detector integrated into the electrical switching device for detecting a fault in the electrical switching device. The fault detector includes the field control electrode. Furthermore, the fault detector includes a temperature sensor for measuring the temperature of the electrical switching device. For the temperature sensor, the field control electrode includes at least one capacitance electrode of a high-voltage capacitance of the electrical switching device. The high-voltage component has a capacitance dielectric electrically coupled to the field control electrode. The capacitance dielectric has at least one dielectric parameter that exhibits a temperature dependence.

[0009] A fault in the switching device represents a deviation of the actual temperature of the switching device from its setpoint temperature or from a range within that setpoint. The fault detector is a monitoring unit for monitoring the temperature of the electrical switching device. To assess the risk of failure of the electrical switching device, it can be used to determine whether a deviation of the measured actual temperature from the setpoint temperature is tolerable or whether a failure of the electrical switching device must be expected, thus necessitating measures to prevent such a failure.

[0010] To assess the failure risk of the electrical switching device, its temperature is monitored. The temperature dependence of the dielectric parameter allows conclusions to be drawn about the actual temperature of the capacitive dielectric and thus the actual temperature of the electrical switching device itself.

[0011] To solve the problem, a method for detecting a fault in the electrical switching device is also provided. A temperature sensor is used as the fault detector to determine the temperature of the electrical switching device.Preferably, the following process steps are carried out: a) providing capacitance data of the high-voltage capacitance as a function of the temperature of the capacitance dielectric, b) determining the actual value of the high-voltage capacitance by measuring an electrical voltage applied to the field control electrode and determining the actual value of an electrical reference voltage of the electrical switching device, and c) determining the temperature of the electrical switching device using an evaluation unit, taking into account the provided capacitance data of the high-voltage capacitance, the actual value of the high-voltage capacitance, and the actual value of the electrical reference voltage of the electrical switching device. In particular, a known temperature dependence of at least one dielectric parameter of the high-voltage capacitance is used to provide the capacitance data.Taking the reference voltage into account is advantageous because a voltage change due to a change in the temperature of the electrical switching device can be significantly higher than a change in the capacitance of the high-voltage capacitor due to the same change in the temperature of the capacitance dielectric.

[0012] As a dielectric parameter of the capacitance dielectric, at least one temperature-dependent material property of the capacitance dielectric is selected from the group consisting of loss factor (tan δ) and relative permittivity (εR). Advantageously, several of these material properties are used, thus increasing the accuracy of the temperature determination of the capacitance dielectric.

[0013] Advantageously, the actual value of the high-voltage capacitance and the actual value of the electrical reference voltage are determined at essentially the same temperature. The permissible deviation depends on the temperature dependence of the reference voltage measurement. When using an inductive voltage transformer, a deviation within the entire operating range of the transformer is generally possible. Since the measurements are performed at approximately the same temperature, any differing influence of temperature on the measurement results for the actual capacitance and reference voltage can be neglected. For example, the capacitance and reference voltage are determined simultaneously after thermal equilibrium has been reached.

[0014] It is also advantageous to determine the actual value of the high-voltage capacitance and the actual value of the electrical reference voltage at essentially the same frequency. This allows interfering, frequency-dependent influences on the measurement results to be neglected.

[0015] The temperature of an electrical switching device can depend on many factors. This method is particularly advantageous when the temperature of the electrical switching device depends primarily on the temperature of a screw connection to a high-voltage cable. A high temperature of the electrical switching device indicates improper assembly of one of the high-voltage screw connections of the electrical switching device.

[0016] With regard to the electrical switching device, it is advantageous if the capacitive dielectric is formed using a castable dielectric starting material. This simplifies the manufacturing of the electrical switching device.

[0017] Various organic and / or inorganic capacitance materials are conceivable as dielectrics. It is particularly advantageous if the capacitance dielectric contains at least one capacitance material selected from the group consisting of epoxy resins and ceramics. The epoxy resin used here typically contains at least one inorganic filler with a proportion of, for example, 60 wt.% or more. The inorganic filler may, for example, consist of ceramic and / or glass-like particles.

[0018] Regarding the method, an epoxy resin is used as the capacitance dielectric according to a specific embodiment. The determination of the high-voltage capacitance and the determination of the reference voltage are carried out at the glass transition temperature of the epoxy resin. It is precisely at the glass transition temperature that the dielectric properties of the epoxy casting resin deteriorate significantly. This allows the temperature of the capacitance dielectric, and thus the temperature of the electrical switching device, to be determined with a high degree of certainty.

[0019] With regard to the electrical switching device, the high-voltage capacitance is formed by a connection socket of the electrical switching device according to a special design.

[0020] Capacitance measurement can be performed in any desired manner. In a specific embodiment, the electrical switching device is equipped with an interface for acquiring a capacitive output signal according to IEC61243-5 / 62271-213 / 62271-206.

[0021] According to a further embodiment of the method, a comparison is made with a reference value in the form of a signal from an adjacent phase and / or the same phase of another high-voltage electrical switching device with sufficiently similar geometry and material properties. This allows for the determination of a relative change, for example, by specifying limit values ​​within which these relative changes are permissible.

[0022] According to another aspect of the invention, the electrical switching device is used for a switchgear system for switching an electric current with high voltage of over 1 kV.

[0023] If the invention is intended to consider only a relative change in a dielectric parameter, the method can also be applied to historical data, for example, if further parameters such as the current or the current's temporal behavior are taken into account, or if a comparison with adjacent phases is made when the voltage is sufficiently symmetrical, as well as with adjacent switching fields of the same phase. This can be particularly advantageous because a sufficiently large number of switching fields provides a sufficient number of reference values ​​for increased accuracy.

[0024] Since only an average value is available for determining the temperature of the electrical switching device via a back-calculation from a determined dielectric parameter, the accuracy can be improved by weighting the average value over further parameters such as the time-dependent change of the current and ambient temperature in combination with a physical model.

[0025] In summary, the following advantages of the invention can be highlighted: Due to the fault detector integrated into the electrical switching device, no discrete component is required. Existing components of the electrical switching device are used. Existing data sources can be used to provide high-voltage capacitance data. Therefore, no work in the high-voltage area is necessary. In some types of electrical switching devices, a field control electrode is located closer to the fault location than a separate fault sensor would need to be installed.

[0026] The invention is described in more detail below with reference to an exemplary embodiment and the accompanying figures. The figures are schematic and not to scale. Figure 1 shows a diagram illustrating the operation of the electrical switching device with integrated fault detector. Figure 2 shows a connection socket of a high-voltage cable of the electrical switching device. Figure 3 shows measurement results of the dielectric parameters as a function of temperature. Figure 4 shows a method for determining the temperature of a component of the electrical switching device.

[0027] A switchgear 2 with an electrical switching device 1 for high voltage is given. The electrical switching device 1 can switch an electric current at high voltage (AC voltage of over 1 kV). The electrical switching device 1 is connected to a high-voltage cable 123 via a terminal 122.

[0028] The electrical switching device 1 has a field control electrode 11 for field control of at least one high-voltage component 10 of the electrical switching device 1 and an integrated fault detector 12. The integrated fault detector 12 is a temperature sensor 120. The high-voltage component 10 of the electrical switching device 1 is a screw connection 110.

[0029] For the temperature sensor 120, the field control electrode 11 has a capacitance electrode 1210, a high-voltage capacitance 121 of the electrical switching device 1, and the high-voltage component 10 (screw connection 110) has a capacitance dielectric 1211 electrically coupled to the field control electrode 11.

[0030] The capacitance dielectric 1211 exhibits a dielectric parameter 1212 that shows a temperature dependence. The capacitance dielectric 1211 is an epoxy casting resin filled with quartz flour.

[0031] To determine the temperature of component (screw connection) 10 of the electrical switching device 1, the high-voltage component 10 and the temperature sensor 120 are in thermal exchange. Thermal energy is exchanged between the component and the temperature sensor.

[0032] The following procedure steps are carried out to determine the temperature of the high-voltage component 10 ( Figure 4 ): a) Providing 2001 capacitance data of the high-voltage capacitance 121 as a function of the temperature of the capacitance dielectric 1211, b) Determining 2002 an actual value of the capacitance of the high-voltage capacitance 121 by measuring an electrical voltage applied to the field control electrode 11 and determining an actual value of an electrical reference voltage of the electrical switching device 1, and c) Determining 2003 the temperature of the electrical switching device 1 using an evaluation unit 140, taking into account the provided capacitance data of the high-voltage capacitance 121, the actual value of the capacitance of the high-voltage capacitance 121, and the actual value of the electrical reference voltage 131 of the electrical switching device 1.

[0033] To provide the capacitance data, a temperature dependence of the dielectric capacitance parameter 1212 of the capacitance dielectric 1211 is used. The loss factor tan δ and the relative permittivity εR of the epoxy casting resin are considered as dielectric parameters.

[0034] Determining the actual value of the high-voltage capacitor 121 and the actual value of the electrical reference voltage 131 is performed at essentially the same frequency. The frequency (measurement frequency) is 50 Hz (1311) and, in an alternative version, 60 Hz (1312).

[0035] The electrical switching device 1 is used in a switchgear 2 for switching an electric current with high voltage of over 1 kV.

Claims

1. Electrical switching device (1) for high voltage, having - at least one field control electrode (11) for controlling the field of at least one high-voltage-carrying component (10) of the electrical switching device (1) and - having at least one fault detector (12) for detecting a fault in the electrical switching device (1), said fault detector being integrated in the electrical switching device (1), wherein - the fault detector (12) comprises the field control electrode (11), - the fault detector (12) comprises a temperature sensor (120) for measuring a temperature of the electrical switching device (1) and for the temperature sensor (120) - the field control electrode (11) comprises at least one capacitance electrode (1210) of a high-voltage capacitor (121) of the electrical switching device (1), - the high-voltage component (10) comprises a capacitance dielectric (1211) which is electrically coupled to the field control electrode (11) and - the capacitance dielectric (1211) has at least one dielectric parameter (1212) having a temperature dependency.

2. Electrical switching device (1) according to Claim 1, wherein the capacitance dielectric (1211) is formed with the aid of a castable dielectric starting material.

3. Electrical switching device (1) according to Claim 1 or 2, wherein the capacitance dielectric (1211) comprises at least one capacitance material (1213) selected from the group of epoxy casting resin and ceramic.

4. Electrical switching device (1) according to one of Claims 1 to 3, wherein the high-voltage capacitor (121) is formed of a connection socket (122) of the electrical switching device (1).

5. Electrical switching device according to one of Claims 1 to 4 having an interface for sensing a capacitive output signal in accordance with IEC61243-5 / 62271-213 / 62271-206.

6. Method for detecting a fault in an electrical switching device (1) according to one of Claims 1 to 5, wherein, as fault detector (12), a temperature sensor (120) is used to determine a temperature of the electrical switching device (1).

7. Method according to Claim 6, wherein, in order to determine the temperature of the electrical switching device (1), the following method steps are carried out: a) providing (2001) capacitance data of the high-voltage capacitor (121) on the basis of a temperature of the capacitance dielectric (1211), b) determining (2002) an actual value of the capacitance of the high-voltage capacitor (121) by measuring an electrical voltage present at the field control electrode (11) and determining an actual value of an electrical reference voltage of the electrical switching device (1) and c) ascertaining (2003) the temperature of the electrical switching device (1) with the aid of an evaluation unit (140) taking into account the provided capacitance data of the high-voltage capacitor (121), the actual value of the capacitance of the high-voltage capacitor (121) and the actual value of the electrical reference voltage (131) of the electrical switching device (1).

8. Method according to Claim 7, wherein, in order to provide the capacitance data, a known temperature dependency of at least one dielectric parameter (1212) of the high-voltage capacitor (121) is used.

9. Method according to Claim 8, wherein at least one temperature-dependent material variable of the capacitance dielectric selected from the group of loss factor and relative permittivity is used as the dielectric parameter (1212) of the capacitance dielectric (1211).

10. Method according to one of Claims 7 to 9, wherein the actual value of the capacitance of the high-voltage capacitor (121) and the actual value of the electrical reference voltage (131) are determined at an essentially identical temperature.

11. Method according to one of Claims 7 to 10, wherein the actual value of the capacitance of the high-voltage capacitor (121) and the actual value of the electrical reference voltage (131) are determined at an essentially identical frequency (1311, 1312).

12. Method according to one of Claims 7 to 11, wherein the temperature of the electrical switching device (1) depends essentially on a temperature of a screw connection (110) to a high-voltage cable (123).

13. Method according to one of Claims 7 to 12, wherein an epoxy resin is used as the capacitance dielectric (1211) and the capacitance of the high-voltage capacitor (121) and the reference voltage (131) are determined at a glass transition temperature of the epoxy resin.

14. Method according to one of Claims 7 to 13, wherein a comparison with a reference value in the form of a signal of an adjacent phase and / or an identical phase of a further electrical switching device for high voltage having a sufficiently similar geometry and sufficiently similar material properties is carried out.

15. Use of an electrical switching device (1) according to one of Claims 1 to 5 for a switching installation (2) for switching an electrical AC current with high voltage of over 1 kV.