CN210109250U

CN210109250U - High-voltage low-pass filter

Info

Publication number: CN210109250U
Application number: CN201822049978.3U
Authority: CN
Inventors: 金学斌
Original assignee: BEIJING HUATIAN ELECTROMECHANICAL INSTITUTE Co Ltd
Current assignee: BEIJING HUATIAN ELECTROMECHANICAL INSTITUTE Co Ltd
Priority date: 2018-12-07
Filing date: 2018-12-07
Publication date: 2020-02-21
Anticipated expiration: 2028-12-07

Abstract

The utility model provides a high-pressure low pass filter, include: the high-voltage low-pass filter is a low-pass filter with the voltage class of 100kV or above. The high-voltage low-pass filter also comprises a grading ring which is positioned at the top of the high-voltage low-pass filter and between the reactor and the capacitor of the high-voltage low-pass filter so as to reduce the electric field intensity on the surface of the high-voltage electrode.

Description

High-voltage low-pass filter

Technical Field

The utility model relates to a low pass filter field. And more particularly to a high voltage low pass filter.

Background

The partial discharge test is a routine test in the production design process of power transformers with the voltage class of 110kV or above and most dry-type power transformers, the power supply for the test mostly adopts generator sets, the equipment condition of each manufacturing plant is different, the test conditions are greatly different, the generator sets, intermediate transformers and other equipment of most transformer manufacturing plants are old, the power supply of a test station is mixed with the production power of a workshop, therefore, the background noise is large during the partial discharge measurement, the accuracy of the test measurement is influenced, and even the test is difficult to perform due to the interference of a plurality of power supplies.

At present, because the input side voltage of a tested transformer is 6kV, 10kV or 35kV due to a power transformer with a voltage grade of 110kV or above, no filter capable of filtering interference exists, the interference is filtered by a middle transformer or an isolation transformer, the filtering effect is limited, one transformer can only filter about 10dB generally, a plurality of transformers are connected in series, the short-circuit impedance is greatly increased due to the fact that the frequency of a test power supply is 150-200Hz, and the loss in the test process is very large under a high voltage grade.

Therefore, it is desirable to provide a high-voltage low-pass filter capable of effectively filtering power supply and environmental interference in a partial discharge test of a high-voltage large-capacity power transformer.

SUMMERY OF THE UTILITY MODEL

An object of the utility model is to provide a can be in the high-pressure low pass filter of effective filtering power and environmental disturbance in the power transformer partial discharge test of high voltage large capacity.

In order to achieve the above purpose, the utility model adopts the following technical scheme:

a high-voltage low-pass filter comprises a reactor and a capacitor, and the high-voltage low-pass filter is a low-pass filter with the voltage class of 100kV or above.

Preferably, the capacitance value of the high-voltage low-pass filter is according to KL/Z₀And the actual maladjustment parameters are obtained through a fitting relation between the actual maladjustment parameters and the parameters, wherein the fitting relation is as follows:

wherein Ω represents KL/Z₀K2 pi, L is the inductance of the reactor of the high-voltage low-pass filter, Z₀For interferer impedance, a is a constant parameter of 5.32.

Preferably, the high-voltage low-pass filter comprises one or more monolithic structures, each monolithic structure comprising one capacitor and one reactor.

Preferably, the attenuation characteristic of the high-voltage low-pass filter is:

under the condition of 40kHz to 100kHz, the attenuation capacity is more than 20 dB; and

under the condition of 100kHz to 400kHz, the attenuation capacity is more than 40 dB.

Preferably, the high-voltage low-pass filter further comprises a grading ring which is positioned at the top of the high-voltage low-pass filter and between a reactor and a capacitor of the high-voltage low-pass filter.

The utility model has the advantages as follows:

the utility model provides a can be in high-voltage low pass filter of effective filtering power and environmental disturbance among the power transformer partial discharge test of high voltage large capacity.

Drawings

The following describes the embodiments of the present invention in further detail with reference to the accompanying drawings;

FIG. 1 is a block diagram of a high-voltage low-pass filter according to the present disclosure;

FIG. 2 is a schematic diagram of a circuit in a monolithic structure of a high-voltage low-pass filter according to the present disclosure;

FIG. 3 is a circuit schematic of an exemplary high-voltage low-pass filter structure formed from a single body of high-voltage low-pass filters according to the present disclosure;

FIG. 4 is a circuit schematic of an exemplary high-voltage low-pass filter structure formed from a single body of high-voltage low-pass filters according to the present disclosure; and

fig. 5 is a schematic circuit diagram illustrating an attenuation characteristic test of a high-voltage low-pass filter according to the present disclosure, using a single structure as an example.

Detailed Description

In order to explain the present invention more clearly, the present invention will be further described with reference to the preferred embodiments and the accompanying drawings. Similar parts in the figures are denoted by the same reference numerals. It is to be understood by persons skilled in the art that the following detailed description is illustrative and not restrictive, and is not to be taken as limiting the scope of the invention.

Fig. 1 is a block diagram of a high-voltage low-pass filter 10 according to the present disclosure.

As shown in fig. 1, the single structure of the high-voltage low-pass filter 10 of the present disclosure includes a reactor 101 and a capacitor 103, and further includes grading rings 105-1 and 105-2. Each cell structure is a half-filter structure, i.e., includes one reactor 101 and one capacitor 103 connected in series with each other.

As shown in fig. 1, it is a single block structure of the high-voltage low-pass filter 10 of the present disclosure.

As shown in the figure, a reactor 101 is positioned above a capacitor 103, and grading rings 105-1 and 105-2 are positioned at the top of a high-voltage low-pass filter 10 to reduce the electric field intensity on the surface of a high-voltage electrode and avoid the influence of corona discharge caused by the tip of a wire and the like on the measurement of partial discharge of a reactor coil. Grading rings 105-1 and 105-2 may be made of sheet metal, preferably 2mm thick aluminum plate spun and welded, surface polished, and the electrode shape is also ring-shaped, exemplary dimensions of grading rings 105-1 and 105-2 are shown in fig. 2, ring inner diameter D is 40cm, ring cross-sectional diameter D is 8cm, and the highest voltage at which corona discharge does not occur is:

U＝41.5×8^0.72×(40/5+1)^0.32＝329kV (1)

the exemplary grading ring may be used for filters having an operating voltage that is marginally below this value, it being understood that similarly, filters above this operating voltage may be sized appropriately according to the exemplary grading ring when needed.

As shown in fig. 1, since the high-voltage low-pass filter has a large size and a high weight, casters are installed under the package of each single structure for easy movement in use.

With respect to the specific parameters and the combination topology of the reactor 101 and the capacitor 103 in the high-voltage low-pass filter 10, the following will be described in detail with reference to fig. 2, fig. 3 and fig. 4. Wherein, fig. 2 is a schematic circuit diagram in a monolithic structure of the high-voltage low-pass filter 10 according to the present disclosure; FIG. 3 is a circuit schematic of an exemplary high-voltage low-pass filter structure made up of a single body of the high-voltage low-pass filter 10 according to the present disclosure; and fig. 4 is a circuit schematic of an exemplary high-voltage low-pass filter structure made up of a single body of the high-voltage low-pass filter 10 according to the present disclosure.

As shown in fig. 2, a schematic circuit diagram of a reactor 101 (shown as L) and a capacitor 103 (shown as C) connected in series is shown, and when the two single-body structures are combined, the capacitors 103 are directly connected in parallel to form a "T" type filter as shown in fig. 3, and the reactor 101 in the two single-body structures is connected in series at one end not connected to the capacitor 103 to form a "pi" type filter. When the method is applied to the application of filtering to the power transformer, for example, when a partial discharge test is performed, when each phase needs to be filtered in a mode of combining the single structures, the partial discharge test is performed once on the power transformer, and 6 single structures are required to be used simultaneously.

To describe the high-voltage low-pass filter 10 of the present application in more detail, the design process of the high-voltage low-pass filter 10 according to the present disclosure is described below.

In step 201, in order to enable the high voltage low pass filter 10 to be applied to a power transformer with a voltage level of above 110kV, in this embodiment, the high voltage low pass filter 10 is designed to reach the following indexes:

rated voltage: 80kV to ground (effective value)

Attenuation characteristics: the attenuation of the filtering frequency of 100kHz-400kHz is more than or equal to 40dB

Self partial discharge: less than or equal to 5 pC.

In this embodiment, in order to satisfy the partial discharge test requirements of most transformers, the rated voltage is increased to 100A.

In the embodiment, the rated frequency is 150Hz, which can meet the condition that the output power frequency of the generator set is between 100Hz and 200 Hz.

In the present embodiment, the high-voltage low-pass filter 10 of the present disclosure may satisfy: under the condition of 40kHz to 100kHz, the attenuation capacity is more than 20 dB; and under the condition of 100kHz to 400kHz, the attenuation capability is more than 40 dB. Since the background noise of the general test site partial discharge test exceeds 1000pC and is attenuated by 40dB in the range of 100-400kHz, the high-voltage low-pass filter 10 can reduce the background noise in the range to 10pC in the partial discharge test.

In step 203, the impedance of the high voltage low pass filter 10 is determined. In order to satisfy a rated voltage of 80kV and a rated current of 100A, namely, the excitation impedance of the tested power transformer satisfies: in this embodiment, the impedance of the filter is usually about 1% of the excitation impedance of the power transformer to be tested, and the impedance of the reactor 101 of the high-voltage low-pass filter 10 (denoted by X) may be set to 10 Ω, while Z is 80kV/100A is 800 Ω to avoid insertion loss.

In step 205, according to the determined impedance value, the inductance of the high-voltage low-pass filter 10 is determined as follows:

in step 207, the capacitance of the capacitor 103 is determined. In particular if a load impedance Z is assumed₂And the interference source impedance Z₀The same, that is, the detuning parameter V-Z2/Z-1, when the voltage level is less than 1kV, the internal impedance of the interference source and the transmission line is usually 50 Ω or 75 Ω, and in the present embodiment, the interference source impedance is 4000 Ω when the rated voltage is 80 kV.

In actual test, the misadjustment parameter Z2/Z₀1 does not exist, in a power system, there is a large difference in the load offset parameters of different filter bands, and in a power transformer with a high voltage class, it is more difficult to accurately determine the offset parameters.

In the present disclosure, KL/Z is determined₀And calculating the capacitance value by utilizing the fitting relation with the actual detuning parameter. Specifically, the fitting relationship is:

In the present embodiment, theWith a 40% margin, when the high-voltage low-pass filter 10 reaches 40dB from 100kHz, the transition frequency fs is 100 × 60% and 60 kHz. Then KL/Z₀(4000) ═ 0.94 at 2X π X60000 Hz X0.01H, KL/Z₀The value of (2) is taken in, and V is calculated to be 5.6.

Then C ═ L × (V/Z) can be obtained₀)≈20nF。

Therefore, the reactor 101 has a value of 5mH and the capacitor 103 has a value of 10nF in the single structure of the high-voltage low-pass filter 10 of the present embodiment.

Determination of KL/Z by the above₀The fitting relation process between the actual detuning parameter and the actual detuning parameter can obtain the value of the capacitor of the low-pass filter under the high voltage level at one time, so that the production design of the high voltage level does not need to utilize a large amount of simulation and debugging processes under the low voltage condition, and the problem that the production can not be designed under the high voltage level is solved. That is, the design process of the capacitor in the filter is simplified, so that the high-voltage low-pass filter can be industrially produced.

The monomer structure assembled by the above method was subjected to a routine test to obtain the experimental results shown in table 3:

TABLE 3

The attenuation characteristics of the single structure of the high-voltage low-pass filter 10 obtained in this embodiment were measured according to the circuit diagram shown in fig. 5, in which G denotes a signal generator, R1 is equivalent to an interference source impedance, R2 is equivalent to a load impedance, and V1 and V2 denote ac millivolt meters. Insertion loss is defined as

The results of the experiment are shown in table 4:

TABLE 4

As can be seen from the test results in tables 3 and 4, when the high-voltage low-pass filter 10 of the present embodiment is connected to a power transformer for partial discharge measurement, when the test voltage is 80kV, the partial discharge amount is 2pC, not more than 5pC, and the insertion loss is not more than 50 dB. By using the high-voltage low-pass filter 10 of the present disclosure, an ideal test condition can be provided for the partial discharge test.

Obviously, the above embodiments of the present invention are only examples for clearly illustrating the present invention, and are not intended to limit the embodiments of the present invention, and it is obvious for those skilled in the art to make other variations or changes based on the above descriptions, and all the embodiments cannot be exhausted here, and all the obvious variations or changes that belong to the technical solutions of the present invention are still in the protection scope of the present invention.

Claims

1. A high-voltage low-pass filter comprises a reactor and a capacitor, and is characterized in that the high-voltage low-pass filter is a low-pass filter with a voltage class of 100kV or above,

the high-voltage low-pass filter further comprises a grading ring which is positioned at the top of the high-voltage low-pass filter and between the reactor and the capacitor of the high-voltage low-pass filter.

2. High-voltage low-pass filter according to claim 1, characterized in that the capacitance value of the high-voltage low-pass filter is according to KL/Z₀And the actual detuning parameter, wherein the fitting relation is as follows:

wherein, omega is KL/Z₀K2 pi, L is an inductance value of the reactor, Z₀For interferer impedance, a is a constant parameter of 5.32.

3. A high-voltage low-pass filter according to claim 1, characterized by comprising one or more monolithic structures, each monolithic structure comprising one of said capacitors and one of said reactors.

4. The high-voltage low-pass filter according to claim 1, characterized in that the attenuation characteristic of the high-voltage low-pass filter is: