CN206892261U - Alternating current withstand voltage test device for overhead line - Google Patents

Abstract

The utility model discloses an AC withstand voltage test device for overhead lines, comprising: a variable frequency power supply, an excitation transformer, a resonant reactor, an AC contactor and a test interface; The output end of the resonant reactor is connected to the primary coil of the excitation transformer; one end of the resonant reactor is connected to one end of the secondary coil of the excitation transformer through an AC contactor, and the other end of the resonant reactor is connected to the test interface; the other end of the secondary coil of the excitation transformer One end is grounded; the test interface is used to connect with one end of the cable to be tested in the overhead line, and the other end of the cable to be tested is grounded. The device does not need to remove the overhead line when performing the AC withstand voltage test. The AC withstand voltage test is performed on the cable and the overhead line through the series resonance method, which can better detect the insulation defects of the entire line and reduce the labor intensity of the maintenance personnel. and work hazards.

Description

An AC withstand voltage test device for overhead lines

technical field

The utility model relates to the technical field of withstand voltage test, in particular to an AC withstand voltage test device for overhead lines.

Background technique

The existing 35kV neutral point ungrounded system is equipped with an arc suppressing coil, and the arc suppressing coil is automatically controlled and put into the adjustment system. However, overvoltages such as lightning and operation still cause great harm to the 35kV system, causing many groundings. Resulting in cable breakdown failure.

After the substation maintenance repairs the faulty cables, when carrying out the high-voltage test, the capacity of the test equipment cannot meet the conditions due to the conventional test method, so it is necessary to remove the overhead line, which not only increases the work intensity of the substation maintenance personnel, but also This greatly increases the danger of the work, and it is impossible to further investigate the hidden dangers of the insulation of the entire line.

The information disclosed in this background section is only intended to increase the understanding of the general background of the present invention, and should not be considered as an acknowledgment or in any form to imply that the information constitutes the prior art already known to those skilled in the art.

Utility model content

The purpose of the utility model is to provide an AC withstand voltage test device for overhead lines, so as to overcome the existing technical problem of large workload for AC withstand voltage tests on overhead lines.

In order to achieve the above object, the utility model provides an AC withstand voltage test device for overhead lines, including: a variable frequency power supply, an excitation transformer, a resonant reactor, an AC contactor and a test interface; the input terminal of the variable frequency power supply and The external alternating current is connected, the output terminal of the variable frequency power supply is connected with the primary coil of the excitation transformer; one end of the resonant reactor is connected with one end of the secondary coil of the excitation transformer through the AC contactor, and the The other end of the resonant reactor is connected to the test interface; the other end of the secondary coil of the excitation transformer is grounded; the test interface is used to be connected to one end of the cable to be tested of the overhead line, and the cable to be tested The other end is grounded.

In a possible implementation manner, the AC voltage withstand test device further includes: a high-voltage divider; one end of the high-voltage divider is connected to the test interface, and the other end is grounded.

In a possible implementation manner, the high-voltage voltage divider is a purely capacitive voltage divider.

In a possible implementation manner, the AC withstand voltage test device further includes: a high-voltage compensation capacitor; one end of the high-voltage compensation capacitor is connected to the test interface, and the other end is grounded.

In a possible implementation manner, the input terminal of the variable frequency power supply is used to receive 50Hz alternating current, and the voltage of the alternating current is 220V or 380V.

Compared with the prior art, the utility model has the following beneficial effects:

An AC voltage withstand test device for overhead lines provided by the embodiment of the utility model does not need to remove the overhead line when performing the AC withstand voltage test, and performs the AC withstand voltage test on the cable together with the overhead line through the series resonance method, which can be more It is good to find the insulation defect of the whole line, and reduce the labor intensity and work risk of maintenance personnel; at the same time, the equipment is simple, does not need to directly provide high voltage, and the test is simple.

Other features and advantages of the present invention will be set forth in the following description, and, in part, will be apparent from the description, or can be learned by practicing the present invention. The objectives and other advantages of the utility model will be realized and attained by the structure particularly pointed out in the written description and claims hereof as well as the appended drawings.

The technical solutions of the present utility model will be further described in detail through the drawings and embodiments below.

Description of drawings

The accompanying drawings are used to provide a further understanding of the utility model, and constitute a part of the description, and are used to explain the utility model together with the embodiments of the utility model, and do not constitute a limitation to the utility model. In the attached picture:

Fig. 1 is the first circuit structure diagram of the AC withstand voltage test device in the utility model embodiment;

Fig. 2 is a second circuit structure diagram of the AC voltage withstand test device in the embodiment of the present invention.

detailed description

The specific embodiments of the present utility model will be described in detail below in conjunction with the accompanying drawings, but it should be understood that the protection scope of the present utility model is not limited by the specific embodiments.

Unless expressly stated otherwise, throughout the specification and claims, the term "comprise" or variations thereof such as "includes" or "includes" and the like will be understood to include the stated elements or constituents, and not Other elements or other components are not excluded.

An AC withstand voltage test device for overhead lines disclosed in the embodiment of the utility model, as shown in Fig. 1 , includes: a variable frequency power supply, an excitation transformer T, a resonant reactor L, an AC contactor K and a test interface A.

Wherein, the input terminal of the variable frequency power supply is connected with the external alternating current, and the output terminal of the variable frequency power supply is connected with the primary coil of the excitation transformer T. In the embodiment of the utility model, the variable frequency power supply is used to realize the conversion of 50Hz power frequency → direct current → variable frequency alternating current, and output alternating current with adjustable frequency. Specifically, the input power of the variable frequency power supply can be commercial power or industrial power, the frequency is 50Hz, and the allowable error is ±5%; the voltage value is 220V/380V, and the allowable error is ±10%; the output voltage value is adjustable, generally AC 0~200V/400V, the output frequency range is 20~400Hz.

As shown in Figure 1, one end of the resonant reactor L is connected to one end of the secondary coil of the excitation transformer T through an AC contactor K, and the other end of the resonant reactor L is connected to the test interface A; the secondary coil of the excitation transformer T The other end is grounded.

In the embodiment of the utility model, the resonant reactor L and the capacitive inductance to be measured are connected in series to form a resonant circuit, and the resonant reactor L is an inductor with adjustable inductance. By adjusting the inductance of the resonant reactor L, the circuit can reach a resonant state. The excitation transformer is used to isolate the variable frequency power supply from the variable voltage test circuit to protect the variable frequency power supply; at the same time, it plays the role of variable voltage matching to maximize the power and voltage match between the variable frequency power supply and the cable to be tested. The AC contactor K is used to control the on-off of the resonant circuit, which can quickly disconnect the resonant circuit in case of an accident.

The test interface A is used to connect to one end of the cable X to be tested in the overhead line, and the other end of the cable X to be tested is grounded. In the embodiment of the utility model, the test interface A can be quickly connected to the cable to be tested, thereby improving the test efficiency.

The working principle of the AC voltage withstand test device provided by the embodiment of the utility model is as follows: for a series resonant circuit, when the sinusoidal frequency of the external input voltage of the resonant circuit reaches a certain frequency (i.e. the resonant frequency of the circuit), the resonant circuit Inductive reactance is equal to capacitive reactance, namely: So the resonant angular frequency And since ω=2πf ₀ , the resonant frequency Among them, L represents the inductance of the resonant reactor, and C represents the capacitance of the capacitive cable to be tested.

At the same time, when the resonant circuit produces series resonance, U _s =QU ₀ , Among them, the quality factor of the resonant circuit is R is the resistance value of the resonant circuit, which is specifically composed of the excitation transformer of the circuit and the internal resistance of the cable to be tested; U _s represents the voltage on both sides of the cable to be measured, U ₀ represents the output voltage of the secondary coil of the excitation transformer, P _s Indicates the power of the cable to be tested, and P ₀ indicates the output power of the secondary coil of the excitation transformer.

Since the frequency of the resonant circuit can vary within the range of 20-400Hz, the resonant frequency has a large variation range, and the quality factor Q has a large variation range, generally between tens and hundreds. According to the above analysis, since U _s =QU ₀ , That is, a relatively high voltage U _s can be provided for the cable to be tested by a small voltage value U ₀ . For example, when performing a 52KV AC withstand voltage test on cables of overhead lines, if Q is 100, then the excitation transformer can output a voltage of 520V.

An AC voltage withstand test device for overhead lines provided by the embodiment of the utility model does not need to remove the overhead line when performing the AC withstand voltage test, and performs the AC withstand voltage test on the cable together with the overhead line through the series resonance method, which can be more It is good to find the insulation defect of the whole line, and reduce the labor intensity and work risk of maintenance personnel; at the same time, the equipment is simple, does not need to directly provide high voltage, and the test is simple.

On the basis of the above embodiments, as shown in FIG. 2 , the device further includes: a high-voltage divider S; one end of the high-voltage divider S is connected to the test interface A, and the other end is grounded. The high-voltage voltage divider is used to measure the test voltage of the cable X to be tested. When using series resonance, a pure capacitive voltage divider can generally be used to output the detected voltage through direct coupling or optical fiber isolation.

On the basis of the above embodiments, as shown in FIG. 2 , the device further includes: a high-voltage compensation capacitor C1; one end of the high-voltage compensation capacitor C1 is connected to the test interface A, and the other end is grounded. The main function of the high-voltage compensation capacitor is to compensate the short-distance, small equivalent capacitance (less than a few thousand picofarads) of the power cable capacitance, and connect it in parallel to the resonant circuit so that the natural resonant frequency of the circuit is at the frequency of the variable frequency power supply or the specified frequency within range.

The foregoing descriptions of specific exemplary embodiments of the present invention have been presented for purposes of illustration and description. These descriptions are not intended to limit the invention to the precise form disclosed, and obviously many modifications and variations are possible in light of the above teaching. The purpose of selecting and describing the exemplary embodiments is to explain the specific principles of the present invention and its practical application, so that those skilled in the art can realize and utilize various exemplary embodiments of the present invention and various Different options and changes. It is intended that the scope of the invention be defined by the claims and their equivalents.

Claims (5)

1. An AC withstand voltage test device for overhead lines, characterized in that it comprises: variable frequency power supply, excitation transformer, resonant reactor, AC contactor and test interface; The input terminal of the variable frequency power supply is connected to an external alternating current, and the output terminal of the variable frequency power supply is connected to the primary coil of the excitation transformer; One end of the resonant reactor is connected to one end of the secondary coil of the excitation transformer through the AC contactor, and the other end of the resonant reactor is connected to the test interface; The other end is grounded; The test interface is used to connect with one end of the cable under test of the overhead line, and the other end of the cable under test is grounded. 2 . The AC voltage withstand test device according to claim 1 , further comprising: a high-voltage divider; one end of the high-voltage divider is connected to the test interface, and the other end is grounded. 3. The AC withstand voltage test device according to claim 2, characterized in that the high voltage divider is a purely capacitive voltage divider. 4. The AC voltage withstand test device according to claim 1, further comprising: a high voltage compensation capacitor; One end of the high-voltage compensation capacitor is connected to the test interface, and the other end is grounded. 5 . The AC withstand voltage test device according to claim 1 , wherein the input terminal of the variable frequency power supply is used to receive 50 Hz alternating current, and the voltage of the alternating current is 220V or 380V.