A circuit for collecting discharge signals of different frequencies from gas-filled switch cabinets

Abstract

The present invention relates to a circuit for collecting discharge signals of different frequencies of a gas-filled switch cabinet, including a high-voltage sensor and a sampling module, wherein one end of the high-voltage sensor is connected to the high-voltage terminal of the gas-filled switch cabinet, the other end of the high-voltage sensor is connected to the electrical test interface, and the sampling module is connected to the electrical test interface via a banana plug. The high-voltage sensor is encapsulated in an insulator, and one end of the insulator is grounded. The present invention can obtain local discharge signals in the cabinet through the electrical test port of the gas-filled switch cabinet, and the present invention can be used to achieve proportional sampling of local discharge signals and attenuation compensation sampling of high-frequency signals. Through the implementation of the present invention, it is possible to achieve the diverse collection of local discharge signals inside the gas-filled switch cabinet, thereby improving the operation and inspection capabilities of the gas-filled switch cabinet.

Description

Technical Field

[0001] The invention belongs to the technical field of partial discharge detection of electric equipment, in particular to a circuit for collecting discharge signals of different frequencies of a gas-filled switch cabinet. Background Art

[0002] Cubicle type gas insulated switchgear (C-GIS), commonly known as gas-filled switchgear, encloses high-voltage components such as busbars, circuit breakers, disconnectors, transformers, power cables, etc. in a metal shell. The use of compressed gas, mainly SF6, as the insulating medium greatly reduces the volume and floor space of the gas-filled cabinet. In addition, because the high-voltage components are enclosed in a shell filled with SF6 gas or other gases, they are not affected by the external environment and there is no electromagnetic radiation or noise. For this reason, in recent years, gas-filled switchgear has gradually replaced traditional air-insulated switchgear in substation construction with its excellent characteristics such as high reliability, small size, and good insulation performance, and has also been widely used in subways, high-speed railways and other occasions.

[0003] With the increasing use of gas-filled switchgear, the number of its failures has also increased significantly. In recent years, the number of failures has become more frequent. The on-site operation and maintenance of gas-filled cabinets urgently needs effective partial discharge detection technology to detect hidden dangers early and ensure the safety of the power grid. Discharge that occurs only in local areas of the insulator without penetrating between the conductors to which the voltage is applied can occur near the conductor or in other places. This phenomenon is called partial discharge. The occurrence of partial discharge will damage the insulation of the equipment. If the partial discharge in the gas-filled switchgear cannot be discovered in time, it will lead to insulation effectiveness and equipment failure, greatly affecting the safe and stable operation of the power grid. However, the partial discharge detection methods currently used in traditional switchgears, such as transient ground voltage, ultrasound and ultra-high frequency detection methods, are almost ineffective for the detection of all-metal enclosed gas-filled cabinets, resulting in a gap in partial discharge detection technology for gas-filled switchgear.

[0004] Therefore, in order to ensure the normal operation of the gas-filled switchgear equipment and timely discover the hidden dangers of partial discharge in the equipment, it is necessary to develop new partial discharge detection methods and equipment to timely discover partial discharge in the gas-filled switchgear. Summary of the invention

[0005] The purpose of the present invention is to overcome the shortcomings of the prior art and propose a circuit for collecting discharge signals of different frequencies in a gas-filled switch cabinet. The local discharge signal in the cabinet is obtained through the electrical inspection port of the gas-filled switch cabinet, thereby realizing proportional sampling of the local discharge signal and attenuation compensation sampling of the high-frequency signal.

[0006] The present invention solves the technical problem by adopting the following technical solutions:

[0007] A circuit for collecting discharge signals of different frequencies of a gas-filled switch cabinet, comprising a high-voltage sensor and a sampling module, wherein one end of the high-voltage sensor is connected to the high-voltage terminal of the gas-filled switch cabinet, the other end of the high-voltage sensor is connected to the electric test interface, and the sampling module is connected to the electric test interface through a banana plug. The high-voltage sensor is encapsulated in an insulator, and one end of the insulator is grounded;

[0008] The sampling module includes a first gate switch, a second gate switch, a sampling chip, a capacitor C2 and an inductor L1, wherein one end of the first gate switch is connected to a high-voltage sensor, the other end of the first gate switch is connected to one end of the second gate switch through a grounded capacitor C2 and a grounded inductor L1, respectively, and the other end of the second gate switch is connected to the sampling chip. The sampling module is used to realize proportional sampling and high-frequency compensation sampling;

[0009] The specific implementation method of the proportional sampling is: when the first selection switch and the second selection switch are connected to the capacitor C2, the capacitor C2 is used for sampling, the 35kV high voltage end, the capacitor C1 and the capacitor C2 are connected in series, and the partial discharge signal voltage U measured by the capacitor C2 o The relationship with the high-voltage side partial discharge voltage U1 is:

[0010] U o =U1(C2 / C1)

[0011] Among them, C1 is a high-voltage sensor; when capacitor C2 is used for sampling, the output voltage value U o The ratio between the partial discharge voltage U1 on the high-voltage side and the high-voltage side is independent of the frequency and does not change with changes in frequency.

[0012] Moreover, the specific implementation method of the high-frequency compensation sampling is: when the first selection switch and the second selection switch are connected to the inductor L1, the inductor L1 is used for sampling, the 35kV high-voltage end, the capacitor C1 and the inductor L1 are connected in series, and the sampling voltage output value U on the inductor L1 is o for:

[0013]

[0014] Among them, C1 is the high-voltage sensor; U1 is the partial discharge voltage on the high-voltage side, w is the frequency. When the frequency increases, U o The proportionality coefficient of U1 is related to the frequency w It is a positive correlation, the higher the frequency, the larger the value.

[0015] The advantages and positive effects of the present invention are:

[0016] The present invention includes a high-voltage sensor and a sampling module, wherein one end of the high-voltage sensor is connected to the high-voltage terminal of the gas-filled switch cabinet, the other end of the high-voltage sensor is connected to the electrical test interface, and the sampling module is connected to the electrical test interface via a banana plug. The high-voltage sensor is encapsulated in an insulator, and one end of the insulator is grounded. The present invention can obtain the local discharge signal in the cabinet through the electrical test port of the gas-filled switch cabinet. The present invention can realize proportional sampling of the local discharge signal and attenuation compensation sampling of the high-frequency signal. Through the implementation of the present invention, the diverse collection of the internal local discharge signal of the gas-filled switch cabinet can be realized, and the operation and inspection capability of the gas-filled switch cabinet can be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a circuit structure diagram of the present invention. DETAILED DESCRIPTION

[0018] The present invention is further described in detail below with reference to the accompanying drawings.

[0019] Traditional partial discharge detection methods for switch cabinets include: transient ground voltage method, ultrasonic method and ultra-high frequency method. The above methods have good sensitivity for traditional air-insulated switch cabinets, but for inflatable switch cabinets, due to the double-layer shielding structure, the measurement signals in the above detection methods cannot effectively pass through the double-layer shielding to pass out of the inflatable switch cabinet body, resulting in extremely low detection sensitivity and inability to effectively detect partial discharge signals in the cabinet.

[0020] Compared with the prior art, the design idea of ​​the present invention is to directly obtain the signal in the switch cabinet at the test port without the need for an independent sensor structure. When the partial discharge signal is transmitted in the cabinet, the attenuation characteristics of signals of different frequencies have great differences. When directly using resistance sampling, the sampling accuracy of each frequency will decrease. The present invention can ensure proportional sampling and switch to the compensation sampling mode, thereby improving the reliability of signal sampling.

[0021] A circuit for collecting discharge signals of different frequencies from a gas-filled switch cabinet, such as Figure 1 As shown, it includes a high-voltage sensor and a sampling module, wherein one end of the high-voltage sensor is connected to the high-voltage terminal of the inflatable switch cabinet, the other end of the high-voltage sensor is connected to the electrical test interface, the sampling module is connected to the electrical test interface through a 4mm banana plug, the high-voltage sensor is encapsulated in an insulator, one end of the insulator is grounded, and the high-voltage sensor is a capacitor structure, represented by capacitor C1, and the capacitance value is about 100pF.

[0022] Moreover, the sampling module includes a first selection switch, a second selection switch, a sampling chip, a capacitor C2 and an inductor L1, wherein one end of the first selection switch is connected to the high-voltage sensor, the other end of the first selection switch is connected to one end of the second selection switch through the grounding capacitor C2 and the grounding inductor L1 respectively, and the other end of the second selection switch is connected to the sampling chip, and the proportional sampling through the sampling capacitor C2 and the high-frequency compensation sampling through the sampling inductor L1 are respectively realized by controlling the first selection switch and the second selection switch in the sampling module.

[0023] The specific implementation method of proportional sampling is: when the first selection switch and the second selection switch are connected to capacitor C2, capacitor C2 is used for sampling, and the 35kV high-voltage end, capacitor C1 and capacitor C2 are connected in series. At this time, the 35kV power frequency voltage signal and the high-frequency signal (100kHz-50MHz) of partial discharge will be divided according to the capacitive reactance value of the two capacitors. In the present invention, only high-frequency signals are considered. Because the power frequency signal can be filtered out by the subsequent high-pass filter circuit to prevent it from interfering with the sampling circuit.

[0024] When capacitor C2 is used for sampling, the partial discharge signal voltage U measured by capacitor C2 is o The relationship with the high-voltage side partial discharge voltage U1 is:

[0025] U o =U1(C2 / C1)

[0026] Among them, C1 is a high-voltage sensor; when capacitor C2 is used for sampling, the output voltage value U o The ratio between the partial discharge voltage U1 on the high-voltage side and the frequency is independent and does not change with the frequency. Therefore, this function can be used to achieve proportional sampling of partial discharge signals, that is, to sample the same proportional part of each frequency component.

[0027] Since the frequency components of partial discharge signals are mostly concentrated in the range of 100 kHz-50MHz, and the partial discharge signals are severely attenuated during transmission, when collecting partial discharge signals with relatively concentrated high-frequency components, proportional sampling cannot effectively guarantee the accuracy of signal collection, and may even lead to invalid sampling due to excessive attenuation of high-frequency components.

[0028] The specific implementation method of high-frequency compensation sampling is as follows: when the first selection switch and the second selection switch are connected to the inductor L1, the inductor L1 is used for sampling, the 35kV high-voltage end, the capacitor C1 and the inductor L1 are connected in series, and the sampling voltage output value U on the inductor L1 is o for:

[0029]

[0030] Among them, C1 is the high-voltage sensor; U1 is the partial discharge voltage on the high-voltage side, w is the frequency. When the frequency increases, U o The proportionality coefficient of U1 is related to the frequency w The relationship is positively correlated, and the higher the frequency, the larger the value. Therefore, the high-frequency component can be compensated by switching this function to overcome the attenuation of the high-frequency component during the transmission process.

[0031] By switching the above-mentioned proportional sampling and high-frequency compensation sampling functions, sampling of different discharge signals can be achieved. For example, when the discharge type is suspected to be surface discharge, since its main frequency component is the low-frequency part, proportional sampling can be used for collection without compensating the high-frequency component. When the discharge in the switch cabinet is suspected to be suspended discharge, the frequency component of the discharge signal is concentrated around 20MHz, and the attenuation during transmission is serious, so a high-frequency compensation sampling circuit is required to collect the signal.

[0032] It should be emphasized that the embodiments described in the present invention are illustrative rather than restrictive. Therefore, the present invention includes but is not limited to the embodiments described in the specific implementation manner. Any other implementation manners derived by those skilled in the art based on the technical solution of the present invention also fall within the scope of protection of the present invention.

Claims

1. A circuit for collecting discharge signals of different frequencies from a gas-filled switch cabinet, characterized in that: It includes a high-voltage sensor and a sampling module, wherein one end of the high-voltage sensor is connected to the high-voltage terminal of the gas-filled switch cabinet, the other end of the high-voltage sensor is connected to the electric test interface, and the sampling module is connected to the electric test interface through a banana plug. The high-voltage sensor is encapsulated in an insulator, and one end of the insulator is grounded; The sampling module includes a first gate switch, a second gate switch, a sampling chip, a capacitor C2 and an inductor L1, wherein one end of the first gate switch is connected to a high-voltage sensor, the other end of the first gate switch is connected to one end of the second gate switch through a grounded capacitor C2 and a grounded inductor L1, respectively, and the other end of the second gate switch is connected to the sampling chip. The sampling module is used to realize proportional sampling and high-frequency compensation sampling; The specific implementation method of the proportional sampling is: when the first selection switch and the second selection switch are connected to the capacitor C2, the capacitor C2 is used for sampling, the 35kV high voltage end, the capacitor C1 and the capacitor C2 are connected in series, and the partial discharge signal voltage U measured by the capacitor C2 o The relationship with the high-voltage side partial discharge voltage U1 is: IN o =U1(C2 / C1) Among them, C1 is a high-voltage sensor; when capacitor C2 is used for sampling, the output voltage value U o The ratio between the partial discharge voltage U1 on the high-voltage side and the high-voltage side is independent of the frequency and does not change with changes in frequency.

2. A circuit for collecting discharge signals of different frequencies of a gas-filled switch cabinet according to claim 1, characterized in that: The specific implementation method of the high-frequency compensation sampling is: when the first selection switch and the second selection switch are connected to the inductor L1, the inductor L1 is used for sampling, the 35kV high-voltage end, the capacitor C1 and the inductor L1 are connected in series, and the sampled voltage output value U on the inductor L1 o for: Among them, C1 is the high-voltage sensor; U1 is the partial discharge voltage on the high-voltage side, w is the frequency. When the frequency increases, U o The proportionality coefficient of U1 is related to the frequency w It is a positive correlation, the higher the frequency, the larger the value.

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