MEASURING A PARTIAL DISCHARGE OF AN ELECTRICAL EQUIPMENT

Description

[0001] Regardless of the grammatical gender of a particular term, persons with male, female or other gender identity are included. BACKGROUND OF THE INVENTION Field of the invention

[0002] The present invention relates to an electrical device. Furthermore, the invention relates to a corresponding method for measuring a partial discharge at an electrical cable bushing of an electrical device. Description of the state of the art

[0003] Partial discharge (PD) measurements are a standard procedure for assessing the condition of electrical equipment. PD measurements have also proven effective in high- and medium-voltage switchgear. Various methods are used, including UHF sensors, TEV sensors, and measurement methods in the HF range such as coupling capacitors or HFCT (high-frequency current transformers) or other measuring coils. There is a desire to perform these measurements frequently or continuously.

[0004] This requires retrofitting the electrical equipment with the appropriate sensors. This involves considerable effort, which can reduce or negate the economic viability of the PD measurement application, both in new systems and in existing electrical equipment.

[0005] Today, this is solved by installing an HFCT in the high-voltage compartment of switchgear, particularly by placing the HFCT around the cable shield of the switchgear connecting cable. However, this solution is complex to install and maintain.

[0006] The document EP 2 787 584 A1 shows an electrical switchgear assembly comprising several compartments in which, on the one hand, the elements of the high-voltage electrical distribution and, on the other hand, the elements of the low-voltage control, measurement, including partial discharge measurement, communication, diagnostics and protection are arranged separately and insulated.

[0007] The object of the invention is to provide a solution for improved partial discharge measurement. SUMMARY OF THE INVENTION

[0008] The invention is based on the features of the independent claims. Advantageous further developments and refinements are the subject of the dependent claims. Refinements, possible applications, and advantages of the invention will become apparent from the following description and the drawings. Regardless of the grammatical gender of a particular term, it encompasses persons with male, female, or other gender identities.

[0009] The invention relates to an electrical device comprising: A high-voltage area, comprising: ∘ a cable connection space for an electrical line feedthrough and ∘ a capacitive coupling electrode or an inductive coupling, designed to couple out a first frequency range, wherein the capacitive coupling electrode or the inductive coupling is connected to the electrical line feedthrough, a low-voltage area, comprising: ∘ a system for measuring high-frequency currents (in particular a high-frequency current transformer (HFCT), a shunt resistor, a magnetic field sensor based on GMR or a Hall effect), designed to couple out a second frequency range and to perform voltage detection in the second frequency range, ∘ a voltage indicator system (in particular a voltage indicator system (VIS)), designed to measure a third frequency range and to perform voltage detection in the third frequency range, and the electrical line feedthrough,comprising a first terminal and a second terminal, wherein the first terminal is arranged in the cable connection space, wherein the second terminal is arranged in the low-voltage area and wherein the electrical line feedthrough runs from the cable connection space to the system for measuring high-frequency currents and to the voltage display system.

[0010] The disclosed arrangement has the advantage that the partial discharge is measured via the voltage detection by the system for measuring high-frequency currents (high-frequency converter) in the second frequency range.

[0011] A high electrical voltage is present in the high-voltage range. For the purposes of the invention, a high electrical voltage is defined as an alternating electrical voltage greater than or equal to 1 kV (SI unit: kilovolt) and / or a direct electrical voltage greater than or equal to 1.5 kV (SI unit).

[0012] The low-voltage range refers to electrical low voltage. Electrical low voltage refers to alternating voltage up to 1000 volts (SI unit) and / or direct voltage up to 1500 volts (SI unit).

[0013] The components of the low-voltage area are galvanically connected, the remaining components of the electrical equipment, in particular the high-voltage area, are galvanically separated from the low-voltage area.

[0014] The inductive coupling is designed in particular as a Rogowski coil.

[0015] The system for measuring high-frequency currents is designed in particular as a high-frequency current transformer (HFCT), a shunt resistor, a magnetic field sensor based on GMR or a Hall effect.

[0016] The voltage display system is designed in particular as a "Voltage Indicator System" (VIS).

[0017] The electrical cable feedthrough can also be referred to as a connecting cable. In one embodiment, the connecting cable has a cable shield. Alternatively, unshielded cables can be used for the connecting cable.

[0018] In other words, a core idea of ​​this invention is to decouple the second frequency range (in particular 100 kHz to 100 MHz) from the signal path of the voltage detection system via the system for measuring high-frequency currents (in particular an HFCT (High Frequency Current Transformer)).

[0019] Many electrical devices (such as high- and medium-voltage switchgear) already contain a capacitive coupling electrode (built into a bushing) for voltage detection (i.e., for transmitting a voltage signal of 50 Hz, 100 MHz, etc.) in accordance with IEC 62271-213 and comparable standards, or for general field control. However, only the 50 Hz signal has been used for voltage detection (particularly by VIS). However, capacitive coupling electrodes are used to couple out a wider frequency range, including frequencies relevant for partial discharge measurements in the HF range (100 kHz to 100 MHz). The proposed solution of the invention can be used as an alternative to previous solutions.

[0020] An HFCT placed according to the invention will physically only measure a small measurement signal, since experience shows that the coupling capacitance (relatively very small, since the complex resistance is relatively high) of a feedthrough is in the pF range (picofarads). However, interference / noise is even smaller, so the small measurement signal is irrelevant.

[0021] The present invention also offers the advantage that the required installation space for the HFCT sensor can be very small due to the thin signal lines, enabling an optimized design. This also requires a smaller sensor, since the cable leading into the low-voltage area has a small diameter.

[0022] The present invention also offers the advantage that complete assembly in the factory allows for appropriate calibration of the system in a defined environment. The HFCT can be assembled in the factory (at the manufacturer's site, not on-site at the customer's site). This provides the following advantages: Complete in-factory assembly, testing, and calibration for new systems. Simplified assembly and wiring, as the signal (tapped by HFCT in the low-voltage area of ​​the switchgear) is located close to the VIS evaluation system (in the low-voltage area). Simplified assembly for systems in operation, as only work is required in the low-voltage area. This eliminates the need for shutdown in the case of a light-fault-tested switchgear according to IEC 62271-200.

[0023] The present invention also offers the advantage that the 50 Hz signal (e.g., for creating a PRPD pattern) can be extracted from the VDIS (=VIS), particularly in VDIS according to IEC62271-213 with the optional voltage output provided by this standard. The low voltage level of this signal allows for easy further processing.

[0024] In a further development of the invention, a potential-isolated tap is made between the high-voltage area and the low-voltage area.

[0025] Due to the isolated tap, the high voltage of the high-voltage range is not present in the low-voltage range. The isolated tap is specifically designed as a capacitive tap.

[0026] In particular, in the high-voltage range, a capacitive tap acts as the first capacitance, and in either the high- or low-voltage range, a second impedance is present that is much smaller than the first capacitance. Due to the resulting divider, in both cases, only a low voltage is present when diverting to the low-voltage range.

[0027] The high-voltage and low-voltage areas are technically compartmentalized. Therefore, work in the low-voltage area can be carried out in accordance with the Low Voltage Directive, while the high-voltage area can be carried out in accordance with the High Voltage Directive.

[0028] In a further development of the invention, the system for measuring high-frequency currents is arranged in the low-voltage range. This is advantageous because the low-voltage range allows for work in accordance with the Low Voltage Directive.

[0029] In a further development of the invention, the electrical equipment is designed as: a critical electrical equipment and / or an electrical switchgear and / or a high-voltage installation and / or a transformer and / or a motor.

[0030] A critical electrical device is an electrical device that itself and / or its components perform a critical function. A critical function is one whose failure leads to far above-average damage, particularly consequential damage.

[0031] The high-voltage system has a high electrical voltage. A high electrical voltage is present in the high-voltage range. For the purposes of the invention, a high electrical voltage is defined as an alternating electrical voltage greater than or equal to 1 kV (SI unit: kilovolt) and / or a direct electrical voltage greater than or equal to 1.5 kV (SI unit: kilovolt).

[0032] In a further development of the invention lies in the: first frequency range a frequency of 16.66 Hz to 100 MHz, in particular 50 Hz to 100 Hz and / or third frequency range a frequency of 16.66 Hz to 400 Hz, in particular 50 Hz to 60 Hz and / or second frequency range a frequency of 100 KHz to 100 MHz and / or before.

[0033] The system for measuring high-frequency currents, especially HFCT, is preferably designed so that low-frequency interference (especially < 100 kHz) or very high-frequency interference (especially > 100 MHz) is not coupled out in order to achieve a favorable signal-to-noise ratio. This is advantageous because frequencies from 100 kHz to 100 MHz are particularly interesting for partial discharge measurements.

[0034] A frequency of the third frequency range of 16.66 Hz is particularly relevant for rail applications, a frequency of 400 Hz is particularly relevant for aviation applications, especially aircraft.

[0035] In a further development of the invention, the electrical cable feedthrough runs from the cable connection compartment via the system for measuring high-frequency currents to the voltage display system.

[0036] The electrical cable feedthrough thus first reaches the system for measuring high-frequency currents and then continues from there to the voltage display system.

[0037] In a further development of the invention, the electrical line feedthrough runs from the capacitive coupling electrodes to the system for measuring high-frequency currents.

[0038] The electrical leadthrough thus first reaches the capacitive coupling electrode or the inductive coupling, and then continues from there to the system for measuring high-frequency currents. In particular, the electrical leadthrough then continues to the voltage display system.

[0039] In a further development of the invention, the high-voltage range and the low-voltage range are separated from each other. "Separated" means no overlapping area. It also means that a separation exists.

[0040] In a further development of the invention, there is a galvanic separation between the high-voltage range and the low-voltage range. In particular, a demarcation between the high-voltage range and the low-voltage range is thus formed as the galvanic separation.

[0041] In a further development of the invention, the electrical cable feedthrough is grounded via a first inductance in the low-voltage range. The cable feed to the IVDS (=VIS) is thus optimized: According to this embodiment, the cable shield is advantageously grounded via the first inductance near the system for measuring high-frequency currents. See also Fig. 2 .

[0042] In a further development of the invention, the electrical cable feedthrough runs through the system for measuring high-frequency currents together with a grounding connection. The cable feed to the IVDS (=VIS) is thus optimized: In this embodiment, the cable shield and the grounding of the IVDS (=VIS) are routed together through the HFCT. See also Fig. 3 .

[0043] In a further development of the invention, the electrical cable bushing is designed such that an electrical absorption circuit is present between the system for measuring high-frequency currents and the cable connection compartment. This creates an absorption circuit that is specifically tuned to frequencies advantageous for partial discharge (PD) measurements. Development results have shown that the absorption circuit is automatically created by the system for measuring high-frequency currents, in particular a high-frequency current transformer (HFCT). The system for measuring high-frequency currents is advantageously designed such that the advantageous frequencies can be measured in the second frequency range of 100 kHz to 100 MHz.

[0044] In a further development of the invention, the electrical equipment according to the invention also comprises: A second inductance, wherein the second inductance is designed such that the second frequency range corresponds to a convolution of a signal of a transfer function from a partial discharge point to the capacitive coupling electrode.

[0045] In particular, the system for measuring high-frequency currents, in particular the high-frequency current transformer (HFCT), is itself designed as the second inductor. Alternatively, the system for measuring high-frequency currents has an additional component as the second inductor.

[0046] The second inductance and a resulting absorption circuit are designed to preferably measure the second frequency range that results in a convolution of a PD signal from a partial discharge point, in particular a defect, with a transfer function from the defect to the capacitive coupling electrode. Experience has shown that for the size of the electrical equipment, in particular a switchgear and "critical electrical equipment thereof" as well as insulating bushings, these are individual, specific frequencies in the range from 100 kHz to 100 MHz. The second inductance is thus tuned to the second frequency range.

[0047] The invention also comprises a method for measuring a partial discharge at an electrical cable feedthrough of an electrical device, comprising the following steps: Providing an electrical cable feedthrough comprising a first terminal and a second terminal. Arranging the first terminal in a cable connection compartment of a high-voltage area. Arranging the second terminal on a voltage display system in a low-voltage area, such that the electrical cable feedthrough runs from the cable connection compartment to a system for measuring high-frequency currents and to the voltage display system. Coupling out a first frequency range by means of a capacitive coupling electrode or an inductive coupling, wherein the capacitive coupling electrode or the inductive coupling is located in the high-voltage area. Measuring a third frequency range by means of the voltage display system. Performing voltage detection in the third frequency range by means of the voltage display system. Coupling out a second frequency range by means of the system for measuring high-frequency currents.and measuring the partial discharge by performing a voltage detection in the second frequency range by the high-frequency current measuring system.

[0048] The invention also includes a method for measuring a partial discharge using an electrical device according to the invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0049] The special features and advantages of the invention will become apparent from the following explanations of several embodiments based on the schematic drawings.

[0050] It shows Fig. 1 is a schematic representation of the electrical equipment according to the invention, Fig. 2 is a circuit diagram of a first embodiment of the electrical equipment according to the invention and Fig. 3 is a circuit diagram of a second embodiment of the electrical equipment according to the invention. DETAILED DESCRIPTION OF THE INVENTION

[0051] Fig. 1 shows a schematic representation of the electrical equipment 1 according to the invention comprising: A high-voltage area 12, comprising: ∘ a cable connection space 121 for an electrical line feedthrough 122 and ∘ a capacitive coupling electrode or an inductive coupling, designed to couple out a first frequency range, wherein the capacitive coupling electrode or the inductive coupling is connected to the electrical line feedthrough 122, a low-voltage area 11, comprising: ∘ a system for measuring high-frequency currents 111, designed to couple out a second frequency range and to perform voltage detection in the second frequency range, ∘ a voltage display system 112, designed to measure a third frequency range and to perform voltage detection in the third frequency range, and the electrical line feedthrough 122, comprising a first connection and a second connection, wherein the first connection is arranged in the cable connection space 121,wherein the second terminal is arranged in the low-voltage area 11 and wherein the electrical cable feedthrough 122 runs from the cable connection space 121 to the system for measuring high-frequency currents 111 and to the voltage display system 112. ,

[0052] Fig. 2 shows a circuit diagram of a first embodiment of the electrical equipment 1 according to the invention. In this further development of the invention, the electrical cable feedthrough 122 is grounded via a first inductance 113 in the low-voltage area 12. The cable feed 122 to the IVDS 112 (=VIS 112) is thus optimized: According to this embodiment, the cable shield is grounded via the first inductance 113 near the system for measuring high-frequency currents 111. In addition, components are shown, as already described in Fig. 1 described.

[0053] Fig. 3 shows a circuit diagram of a second embodiment of the electrical equipment 1 according to the invention. In this development of the invention, the electrical cable feedthrough 122 runs together with an earthing 114 through the system for measuring high-frequency currents 111. The cable feed 122 to the IVDS 112 (=VIS 112) is thus optimized: The cable shield and the earthing 114 of the IVDS 112 (=VIS 112) are guided together through the HFCT 111 according to this embodiment. In addition, components are shown, as already shown in Fig. 1 described.

[0054] Although the invention has been illustrated and described in detail by the embodiments, the invention is not limited by the disclosed examples and other variations can be derived therefrom by a person skilled in the art without departing from the scope of the invention as defined by the claims.

Claims

1. Electrical equipment item (1), having: - a high-voltage region (12), having: ∘ a cable connection space (121) for an electrical cable bushing (122), and o a capacitive coupling electrode or an inductive coupling, designed to output couple a first frequency range, wherein the capacitive coupling electrode or the inductive coupling is connected to the electrical cable bushing (122), - a low-voltage region (11), having: ∘ a system for measuring high-frequency currents (111), designed to output couple a second frequency range and to carry out voltage detection in the second frequency range, ∘ a voltage indicator system (112), designed to measure a third frequency range and to carry out voltage detection in the third frequency range, and - the electrical cable bushing (122), having a first connection and a second connection, wherein the first connection is arranged in the cable connection space (121), wherein the second connection is arranged in the low-voltage region (11), and wherein the electrical cable bushing (122) runs from the cable connection space (121) to the system for measuring high-frequency currents (111) and to the voltage indicator system (112).

2. Electrical equipment item (1) according to Claim 1, wherein a potential-isolated tap is implemented between the high-voltage region (12) and the low-voltage region (11).

3. Electrical equipment item (1) according to either of the preceding claims, wherein the system for measuring high-frequency currents (111) is arranged in the low-voltage region (11).

4. Electrical equipment item (1), according to one of the preceding claims, in the form of: - a critical electrical equipment item (1) and / or - an electrical switchgear assembly (1) and / or - a high-voltage installation (1) and / or - a transformer (1) and / or - a motor (1).

5. Electrical equipment item (1) according to one of the preceding claims, wherein: - the first frequency range has a frequency of 16.66 Hz to 100 Mhz, in particular 50 Hz to 100 Hz and / or - the third frequency range has a frequency of 16.66 Hz to 400 Hz, in particular 50 Hz to 60 Hz and / or - the second frequency range has a frequency of 100 KHz to 100 Mhz.

6. Electrical equipment item (1) according to one of the preceding claims, wherein the electrical cable bushing (122) runs from the cable connection space (121) to the voltage indicator system (112) via the system for measuring high-frequency currents (111).

7. Electrical equipment item (1) according to one of the preceding claims, wherein the electrical cable bushing (122) runs from the capacitive coupling electrodes to the system for measuring high-frequency currents (111).

8. Electrical equipment item (1) according to one of the preceding claims, wherein the high-voltage region (12) and the low-voltage region (11) are separated from one another.

9. Electrical equipment item (1) according to one of the preceding claims, wherein there is galvanic isolation between the high-voltage region (12) and the low-voltage region (11).

10. Electrical equipment item (1) according to one of the preceding claims, wherein the electrical cable bushing (122) is earthed via a first inductor (113) in the low-voltage region (11).

11. Electrical equipment item (1) according to one of the preceding claims, wherein the electrical cable bushing (122) runs together with earthing (114) through the system for measuring high-frequency currents (111).

12. Electrical equipment item (1) according to one of the preceding claims, wherein the electrical cable bushing (122) is configured in such a way that there is an electrical absorption circuit between the system for measuring high-frequency currents (111) and the cable connection space (121).

13. Electrical equipment item (1) according to one of the preceding claims, furthermore having: - a second inductor, wherein the second inductor is configured in such a way that the second frequency range of a convolution of a signal corresponds to a transfer function from a partial discharge point to the capacitive coupling electrode.

14. Method for measuring a partial discharge on an electrical cable bushing (122) of an electrical equipment item (1), comprising the steps of: - providing an electrical cable bushing (122), having a first connection and a second connection, - arranging the first connection in a cable connection space (121) of a high-voltage region (12), - arranging the second connection on a voltage indicator system (112) in a low-voltage region (11), with the result that the electrical cable bushing (122) runs from the cable connection space (121) to a system for measuring high-frequency currents (111) and to the voltage indicator system (112), - a capacitive coupling electrode or an inductive coupling output coupling a first frequency range, wherein the capacitive coupling electrode or the inductive coupling is in the high voltage region (12), - the voltage indicator system (112) measuring a third frequency range, - the voltage indicator system (112) carrying out voltage detection in the third frequency range, - the system for measuring high-frequency currents (111) output coupling a second frequency range, and - the system for measuring high-frequency currents (111) measuring the partial discharge by carrying out voltage detection in the second frequency range.

15. Method according to Claim 14 with an electrical equipment item (1) according to one of Claims 1 to 13.