CN112731081A - Method and device for acquiring partial discharge phase - Google Patents

Abstract

At present, the instrument that collects the original waveform of the partial discharge UHF signal cannot obtain the power frequency phase of the UHF signal. Therefore, the present invention provides a method and device for obtaining the partial discharge phase, which converts the non-monotonic sine wave in a single cycle into It is a monotonous sawtooth wave in a single cycle, and the waveform of the sawtooth wave is collected for a very short time, and the phase of the sine wave corresponding to this waveform can be determined. The comparator converts the sine wave into a square wave, the processor performs data calculation on it, converts the square wave into a sawtooth wave, inputs the sawtooth wave to the UHF signal sampling device, calculates the moment when the partial discharge occurs, and finally converts it into a partial discharge. discharge phase.

Description

A method and apparatus for obtaining partial discharge phase

technical field

The present invention relates to the field of electric power technology, and in particular, to a method and a device for obtaining a partial discharge phase.

Background technique

At present, the instrument that collects the original waveform of the partial discharge UHF signal cannot obtain the power frequency phase of the UHF signal, because the single acquisition time length is less than 500ns when collecting the UHF signal. Compared with the short power frequency period, the corresponding power frequency phase cannot be confirmed.

SUMMARY OF THE INVENTION

In order to solve the above problems, the present invention provides a method and device for obtaining a partial discharge phase.

The method includes the steps:

a) Obtain 220V AC from the maintenance power supply, and step down to low-voltage AC;

b) Obtain the frequency f of the low-voltage alternating current, define the phase difference α as the phase at which the voltage of the maintenance power supply lags behind the voltage of the equipment to be subjected to partial discharge detection, and define the phase difference β as the phase at which the voltage of the low-voltage alternating current lags behind the voltage of the maintenance power supply, and obtain α, β;

c) inputting the low-voltage alternating current to a voltage comparator, and the voltage comparator converts its power frequency sinusoidal signal into a square wave signal;

d) inputting the square wave signal to the processor, after the processor detects the rising edge every time, the output voltage signal that increases according to the fixed slope k from 0V is converted into a sawtooth wave signal;

e) inputting the sawtooth wave signal to the UHF signal sampling equipment, the sampling equipment simultaneously collects the UHF signal and the sawtooth wave signal, and calculates the time t at which the partial discharge occurs according to the sawtooth wave signal amplitude;

f) According to the frequency f obtained in step b, convert the time t when the partial discharge occurs into phase γ:

γ=360tf;

g) According to the phase difference α obtained in step b, convert the phase γ into the real phase δ:

δ=γ+α+β.

Preferably, the method of converting the power frequency sinusoidal signal into a square wave signal described in step c is:

The threshold value of the voltage comparator is 0V. When the low-voltage AC voltage is positive, the voltage comparator outputs a fixed positive voltage signal. When the low-voltage AC voltage is negative, the voltage comparator outputs 0V.

Preferably, the method for calculating the time t when the partial discharge occurs in step e is:

Among them, w _m is the amplitude of the sawtooth signal when the UHF signal has a maximum value.

Preferably, the method for calculating the time t when the partial discharge occurs in step e is:

是锯齿波信号的幅值平均值。in,

is the average value of the amplitude of the sawtooth signal.

The device includes:

The step-down module is used to step down the 220V AC voltage of the maintenance power supply to a low-voltage AC signal.

A voltage comparator for converting a sine wave to a square wave.

A processor for performing data calculations to convert square waves into sawtooth waves.

The power supply module is used to rectify alternating current into direct current to supply power to the whole device.

The beneficial effects of the present invention are:

The invention converts the non-monotonic sine wave in a single cycle into a monotonic sawtooth wave within a single cycle, and collects the waveform of the sawtooth wave in a very short time, so that the phase of the sine wave corresponding to the waveform can be determined.

The invention realizes the acquisition of the original waveform of the partial discharge UHF signal and simultaneously determines the power frequency phase of the partial discharge, the UHF original waveform signal is used for the localization of the partial discharge, and the power frequency phase is used to draw a partial discharge diagnostic map such as a PRPD map, etc. The present invention enables simultaneous partial discharge diagnosis and localization.

Detailed ways

The technical solutions proposed by the present invention will be further described below according to specific embodiments, and the following is an implementation manner

Step S1: Obtain 220V alternating current from the maintenance power supply, and use a small transformer to step down it to low-voltage alternating current.

Step S2: Obtain the phase difference α of the voltage of the maintenance power supply behind the voltage of the equipment to be subjected to partial discharge detection (such as GIS, transformer) through the substation background system, and obtain the phase difference β of the low-voltage AC voltage described in S1 that is behind the voltage of the maintenance power supply by measuring , obtain the frequency f of the low-voltage alternating current by measuring.

Step S3: Input the above-mentioned low-voltage alternating current to the voltage comparator, the threshold value of the voltage comparator is 0V, when the low-voltage alternating current voltage is positive, the voltage comparator outputs a fixed positive voltage signal, and when the low-voltage alternating current voltage is negative, the voltage comparator outputs 0V , the voltage comparator converts the power frequency sine signal into a square wave signal.

Step S4: Input the above square wave signal to the processor, the processor continuously detects the rising edge, and after each rising edge is detected, it outputs a voltage signal that increases from 0V according to the fixed slope k, and the processor converts the square wave signal into Sawtooth signal.

Step S5: Input the above-mentioned sawtooth wave signal to the UHF signal sampling device, the sampling device simultaneously collects the UHF signal and the sawtooth wave signal, the sawtooth wave signal is w, and there are two methods for calculating the time t of partial discharge occurrence:

w_m是特高频信号出现最大值时锯齿波信号的幅值；

w _m is the amplitude of the sawtooth signal when the UHF signal has a maximum value;

是锯齿波信号的幅值平均值。or

is the average value of the amplitude of the sawtooth signal.

Step S6: According to the frequency f obtained in S2, the time t is converted into a phase γ=360tf.

Step S6: According to the phase difference α obtained in S2, the above phase is converted into a real phase δ=γ+α+β.

的单位是V(伏特)。In the above formula, the unit of α, β, γ is ° (degree), the unit of t is s (second), the unit of f is Hz (Hertz), the unit of w, w _m ,

The unit is V (Volt).

Finally, it should be noted that the above are only preferred embodiments of the present invention, and are not intended to limit the present invention. Although the present invention has been described in detail with reference to the foregoing embodiments, for those skilled in the art, it is still The technical solutions described in the foregoing embodiments may be modified, or some technical features thereof may be equivalently replaced. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims (5)

1. A method for obtaining a partial discharge phase, comprising the steps of:

a) acquiring 220V alternating current from a maintenance power supply, and reducing the voltage into low-voltage alternating current;

b) acquiring the frequency f of low-voltage alternating current, defining a phase difference alpha as a phase position where the voltage of a maintenance power supply lags behind the voltage of equipment to be subjected to partial discharge detection, defining a phase difference beta as a phase position where the voltage of the low-voltage alternating current lags behind the voltage of the maintenance power supply, and calculating to obtain alpha and beta;

c) inputting the low-voltage alternating current into a voltage comparator, and converting a power frequency sinusoidal signal into a square wave signal by the voltage comparator;

d) inputting the square wave signal into a processor, outputting a voltage signal increased from 0V according to a fixed slope k by the processor after the processor detects a rising edge every time so as to convert the voltage signal into a sawtooth wave signal, wherein the value of k is to ensure that the amplitude of the sawtooth wave is within the input voltage range of the processor;

e) inputting the sawtooth wave signal into ultrahigh frequency signal sampling equipment, simultaneously acquiring the ultrahigh frequency signal and the sawtooth wave signal by the sampling equipment, and calculating the time t when partial discharge occurs according to the amplitude of the sawtooth wave signal;

f) and b, converting the time t of the partial discharge into a phase gamma according to the frequency f obtained in the step b:

γ＝360tf；

g) according to the phase difference alpha and beta obtained in the step b, converting the phase gamma into a real phase delta:

δ＝γ+α+β。

2. the method for obtaining the partial discharge phase according to claim 1, wherein the step c of converting the power frequency sinusoidal signal into the square wave signal is as follows:

the threshold value of the voltage comparator is 0V, when the voltage of the low-voltage alternating current is positive, the voltage comparator outputs a fixed positive voltage signal, and when the voltage of the low-voltage alternating current is negative, the voltage comparator outputs 0V.

3. The method for obtaining the partial discharge phase according to claim 1, wherein the method for calculating the time t when the partial discharge occurs in step e is as follows:

wherein, w_mIs the amplitude of the sawtooth wave signal when the ultrahigh frequency signal has a maximum value.

4. The method for obtaining the partial discharge phase according to claim 1, wherein the method for calculating the time t when the partial discharge occurs in step e is as follows:

wherein,

is the average value of the amplitudes of the sawtooth signals.

5. An apparatus for acquiring a partial discharge phase, comprising:

the voltage reduction module is used for reducing the 220V alternating current voltage of the maintenance power supply into a low-voltage alternating current signal;

a voltage comparator for converting a sine wave into a square wave;

the processor is used for calculating data and converting the square wave into a sawtooth wave;

and the power supply module is used for rectifying the alternating current into direct current to supply power to the whole set of device.