CN101702003A

CN101702003A - Detection circuit for partial discharge of capacitor

Info

Publication number: CN101702003A
Application number: CN200910075335A
Authority: CN
Inventors: 何平; 高生; 刘大永; 景崇友; 赵秀生
Original assignee: Baoding Tianwei Xinyu Technology Development Co Ltd; Baoding Tianwei Group Co Ltd
Current assignee: Jiangsu Laitekai Machinery Co ltd
Priority date: 2009-09-10
Filing date: 2009-09-10
Publication date: 2010-05-05
Anticipated expiration: 2029-09-10
Also published as: CN101702003B

Abstract

The invention relates to a detection circuit for the partial discharge of a capacitor, which is used for detecting the partial discharge signals of a high-voltage capacitor. The detection circuit comprises a self-balancing coupling transformer, an inducer and a capacitor, wherein the self-balancing coupling transformer comprises an iron core and three coils, and the first coil has the same structure as that of the second coil. The head end of the first coil is an unbalanced input end connected with a test power supply through a sampling capacitor, and the tail end of the first coil is connected with the tail end of the second coil through the inducer and connected with the head end of the second coil through the capacitor. The head end of the second coil is connected with a signal public end, and partial discharge signals outputted from the two ends of the third coil are connected with a partial discharge tester. The invention can work at two test modes: unbalanced mode and balanced mode, and can separate out partial discharge pulse current signals when an impedance magnetic core is approximate to zero magnetic flux at either test mode. The self-balancing coupling transformer can not be saturated, therefore the sensitivity of partial discharge detection can not be influenced by the current size in a main loop.

Description

Detection circuit for partial discharge of capacitor

Technical field

The present invention relates to a kind of circuit that is used to detect the high-voltage power capacitor local discharge signal, belong to the detection technique field.

Background technology

In the production run of high-voltage power capacitor, need test its insulating property by detecting its inner discharge capacity.At present, the method that detects high-voltage power capacitor internal discharge amount mainly contains two kinds, and a kind of is supersonic testing method, and a kind of is pulse current method, the shortcoming that adopts supersonic testing method is that quantitative error is bigger, can not accurately measure the discharge value of capacitor inside sometimes; Pulse current method be with test product electric capacity with receive test after the coupling transformer primary coil is connected with on the alternating-current measurement power supply, judge the discharge capacity of measured capacitance inside by detecting pulsed current signal in the transformer secondary output coil.The shortcoming of this method is that the leakage current of capacitor is very faint with respect to the test current that flows through it, be not easy to detect, and when the test current in the series loop is big, can make coupling transformer saturated, cause detection sensitivity to descend, even can't detect.

Summary of the invention

The objective of the invention is to overcome the deficiencies in the prior art, a kind of highly sensitive detection circuit for partial discharge of capacitor is provided.

Problem of the present invention realizes with following technical proposals:

A kind of detection circuit for partial discharge of capacitor, comprise self-equilibrating coupling transformer, inductance and electric capacity in the formation, described self-equilibrating transformer is made up of iron core and three coils, the structure of first coil and second coil is identical, the head end of first coil is non-equilibrium input end, connect testing power supply by test product electric capacity, its tail end connects the tail end of second coil through inductance, and connect the head end of second coil through electric capacity, the head end of second coil connects the signal common port, and tester is put in the discharge signal office of connecing of office of tertiary coil two ends output.

Above-mentioned detection circuit for partial discharge of capacitor, also comprise the test pattern switch in the formation, the non-equilibrium contact of described test pattern switch is connected between the tail end and inductance of first coil, the balance contact is connected between the head end of the tail end of first coil and second coil, the tail end of described second coil connects testing power supply as the balance input end through standard capacitance.

Above-mentioned detection circuit for partial discharge of capacitor is connected to the output impedance build-out resistor at the two ends of tertiary coil.

Above-mentioned detection circuit for partial discharge of capacitor, the span of described inductance are 0.1-1mH; The span of electric capacity is 0.001-0.47 μ F.

The present invention constitutes the high-voltage capacitor detection circuit for partial discharge with balance coupling transformer, inductance, electric capacity and test pattern switch, this testing circuit both can be operated in non-equilibrium test pattern, also can be operated in the balance test pattern, all can be under the state of impedance magnetic core under two kinds of test patterns near zero magnetic flux, pulsed current signal is put in office to be separated, the balance coupling transformer saturated phenomenon can not occur, thereby the size of main circuit current can not influence office and puts detection sensitivity.

Description of drawings

The invention will be further described below in conjunction with accompanying drawing.

Fig. 1 is a structural principle synoptic diagram of the present invention;

Fig. 2 is the electrical schematic diagram of non-balance test pattern;

Fig. 3 is the electrical schematic diagram of balance test pattern.

Each label is among the figure: T, balance coupling transformer; L, inductance; C, electric capacity; N1, first coil; N2, second coil; N3, tertiary coil; K, test pattern switch; R, output impedance build-out resistor; BNC, lead-out terminal; C _S, test product electric capacity; C _B, standard capacitance; 1, non-equilibrium input end, 2, the balance input end, 3, non-equilibrium contact; 4, balance contact; COM, signal common port.

Embodiment

Referring to Fig. 2, under non-equilibrium test pattern, non-equilibrium contact 3 closures of test pattern switch K, balance contact 4 disconnects, and non-equilibrium input end 1 connects the test product capacitor C _S, balance input end 2 does not meet standard capacitance C _B, thereby test convenient.After testing power supply is connected, because inductance L is short-circuit condition to low frequency signal, and high-frequency signal is high-impedance state, capacitor C then is high-impedance state to low frequency signal, high-frequency signal is short-circuit condition, low frequency test current signal enters from the head end of N1, from the end outflow of N1, through after the inductance L, enter from the end of winding N2, the head end of N2 flows out, and the magnetic field that produces in two windings is opposite fully, cancels each other; The high-frequency discharge pulse signal enters from the head end of N1, through winding N1, and capacitor C, from the head end of N2, promptly signal common port COM flows out, and just can detect this discharge pulse signal at the two ends of N3.Because in testing process, the test current signal of low frequency can not be coupled among the N3 and go, but is cancelled, thereby transformer saturated phenomenon can not occur, has improved detection sensitivity of the present invention greatly.

Referring to Fig. 3, under the balance test pattern, balance contact 4 closures of test pattern switch K, non-equilibrium contact 3 disconnects, and non-equilibrium input end 1 connects the test product capacitor C _S, balance input end 2 meets standard capacitance C _B, the test product capacitor C _SWith standard capacitance C _BThe other end all connect testing power supply.This moment inductance L open circuit, capacitor C is then by short circuit, add trial voltage after, flow through the test product capacitor C _SElectric current (by having sneaked into office's discharge signal behind the test product) enter the head end of N1, flow through standard capacitance C _BElectric current (no office discharge signal) enter the end of N2, so the test current of identical size produces equal and opposite in direction in two windings, opposite polarity magnetic field, cancel each other in two parts magnetic field, and the discharge pulse current signal only passes through in winding N1, be not cancelled, this signal is exported from winding N3 two ends.

The coil N1 of balance coupling transformer T and N2 are symmetrical fully, and less coupling capacitance is arranged, and the number of turn of N3 is determined by output impedance; Transformer core can be other permeability magnetic materials such as FERRITE CORE or siliconized plate; Inductance L can be air core inductor or magnetic core, iron-core inductance; Capacitor C can be noninductive electric capacity or common electric capacity, and electric capacity is according to the discharge signal frequency band decision of test product electric capacity office.Local discharge signal takes out from output BNC terminal, can strengthen antijamming capability, connects testing tool through it.

Claims

1. detection circuit for partial discharge of capacitor, it is characterized in that, comprise self-equilibrating coupling transformer (T), inductance (L) and electric capacity (C) in the formation, described self-equilibrating transformer (T) is made up of iron core and three coils, first coil (N1) is identical with the structure of second coil (N2), the head end of first coil (N1) is non-equilibrium input end (1), by test product electric capacity (C _S) connect testing power supply, its tail end connects the tail end of second coil (N2) through inductance (L), and connect the head end of second coil (N2) through electric capacity (C), and the head end of second coil (N2) connects signal common port (COM), and tester is put in the discharge signal office of connecing of office of tertiary coil (N3) two ends output.

2. according to the described detection circuit for partial discharge of capacitor of claim 1, it is characterized in that, also comprise test pattern switch (K) in the formation, the non-equilibrium contact (3) of described test pattern switch (K) is connected between the tail end and inductance (L) of first coil (N1), balance contact (4) is connected between the head end of the tail end of first coil (N1) and second coil (N2), the tail end of described second coil (N2) is as balance input end (2), through standard capacitance (C _B) connect testing power supply.

3. according to claim 1 or 2 described detection circuit for partial discharge of capacitor, it is characterized in that, be connected to output impedance build-out resistor (R) at the two ends of tertiary coil (N3).

4. according to the described detection circuit for partial discharge of capacitor of claim 3, it is characterized in that the span of described inductance (L) is 0.1-1mH; The span of electric capacity (C) is 0.001-0.47 μ F.