CN104142452B - Method based on residual voltage during two single-phase potential transformers extraction power distribution network single-phase earthings - Google Patents

Abstract

The present invention is a kind of method of residual voltage extracted based on two single-phase potential transformers during power distribution network single-phase earthing, it is characterized in, determines including the choosing of earth fault RELATED APPLICATIONS vector, primary vector VV1 is formationed, secondary vector VV2 formation, the selection principle in t1 and t2 moment, the acquisition time of electric measurement Vp1 and Vp2 and sample rate, calculate the steps such as residual voltage is vectorial.There is methodological science reasonable, simple and easy to do, obtain residual voltage low cost, and the physical size of relevant device can be reduced, it is adaptable to include a plurality of outlet and the distribution network system of a bus, to carry out selective grounding protection when there is singlephase earth fault.

Description

Extraction of zero-sequence voltage in single-phase grounding of distribution network based on two single-phase voltage transformers Methods

technical field

The invention relates to a grounding detection technology of a power distribution network, in particular to a method for extracting a zero-sequence voltage when a single-phase grounding of a power distribution network is based on two single-phase voltage transformers.

Background technique

my country's 10kV distribution network has a large number, wide distribution range, low equipment insulation level, and is susceptible to various faults caused by the internal factors of the power grid and the external natural environment; among them, the probability of single-phase ground faults is the highest, which can account for the total faults. About 80% of it. When a single-phase ground fault occurs in the distribution network, the line voltage between the three phases is still symmetrical, and the fault current is small, which does not affect the continuous power supply to the load, and does not need to trip immediately. The regulations stipulate that it can continue to run for 1 to 2 hours.

One of the characteristics of ground fault occurrence, zero-sequence voltage is an important characteristic quantity for ground fault detection, alarm and processing; with the rapid development of urban distribution network scale, the requirements for automatic control technology and level are getting higher and higher, outdoor automatic The scope of application of measurement and control equipment such as FTU and intelligent high-voltage electrical appliances continues to expand; due to the limitations of various reasons for the installation of outdoor automatic measurement and control equipment, no zero-sequence voltage transformer is installed, but only simple single-phase voltage transformers and single line voltage The transformer cannot obtain the zero-sequence voltage; it brings great difficulties to the detection, alarm and processing of the ground fault for the outdoor automatic measurement and control equipment. So far, there have been no literature reports and practical applications of the method of extracting the zero-sequence voltage of the ground fault based on two single-phase inductors.

Contents of the invention

The technical problem to be solved by the present invention is to provide a method for extracting the zero-sequence voltage when the single-phase grounding of the distribution network is based on two single-phase voltage transformers. The method is scientific and reasonable, simple and easy to operate, and the cost of obtaining the zero-sequence voltage is low , and can reduce the physical size of related equipment, and is suitable for distribution network systems including multiple outgoing lines and a busbar, so as to perform grounding line selection protection in the event of single-phase grounding faults.

The technical solution adopted to solve the technical problem is a method for extracting the zero-sequence voltage when the single-phase grounding of the distribution network is based on two single-phase voltage transformers, which is characterized in that it includes the following content:

1) Before and after the ground fault, the selection steps of the reference vector: it is used to use the first single-phase voltage transformer according to the law that the phase amplitude of the line voltage basically does not change in the relevant electrical quantities before and after the ground fault. Transform the primary line voltage and send it to the analog quantity acquisition terminal of the equipment, and use the collected electrical quantity as the reference vector Vr;

2) Steps for forming the first vector VV1: use the second single-phase voltage transformer to transform the primary a-phase voltage and send it to the analog quantity acquisition terminal of the equipment. The reference vector of Vr is compared to form the first vector VV1 for analysis and calculation;

3) Forming step of the second vector VV2: use the second single-phase voltage transformer to transform the voltage of phase a and send it to the analog quantity acquisition terminal of the equipment. The reference vector Vr is compared to form the second vector VV2 for analysis and calculation;

4) The selection principle of the t1 moment of the step 2) and the t2 of the step 3) is: t2-t1=20 milliseconds, which is a power frequency cycle difference.

5) The acquisition time and sampling rate of the electrical measurement Vp1 of the step 2) and the electrical measurement Vp2 of the step 3) are determined: the acquisition time is a continuous 20 milliseconds; the sampling rate is specified as 3200.

6) The step of calculating the zero-sequence voltage vector: according to the vector difference between the first vector VV1 and the second vector VV2, calculate the zero-sequence voltage V0 at the time of grounding, namely:

V0=VV2-VV1.

The reference vector Vr in the step 1) is the secondary measurement value of the phase-to-phase voltage of a and b phases, or the secondary measurement value of the phase-to-phase voltage of b and c phases, or the secondary measurement value of the phase-to-phase voltage of c and a phases.

The first vector VV1 forming step of said step 2) further includes:

The electrical quantity reference vector Vr and the phase a voltage electrical measurement Vp1 are collected synchronously at time t1;

Simultaneous Fourier transformation of the electrical quantity reference vector Vr and the electrical measurement Vp1 of phase a voltage;

The amplitude of the Fourier transform of phase a voltage electrical measurement Vp1 is taken as the amplitude of the first vector VV1, and the electrical quantity is the angle between the reference vector Vr and the electrical measurement Vp1 of phase a voltage as the phase angle of VV1.

The second vector VV2 forming step of said step 3) further includes:

The electrical quantity reference vector Vr and the phase a voltage electrical measurement Vp2 are collected synchronously at time t2;

Simultaneous Fourier transformation of the electrical quantity reference vector Vr and the electrical measurement Vp2 of the a-phase voltage;

Phase a voltage electrical measurement Vp2 is the amplitude of the Fourier transform of the second vector VV2, and the angle between the electrical quantity reference vector Vr and phase a voltage electrical measurement Vp2 is used as the phase angle of the second vector VV2.

The step 2) and step 3) are the voltage transformation of the second single-phase voltage transformer to the primary a-phase voltage, or the voltage transformation of the second single-phase voltage transformer to the primary b-phase voltage, or the second branch The single-phase voltage transformer converts the voltage of the primary c-phase voltage.

The invention is based on two single mutual inductors to extract the zero-sequence voltage of the ground fault, which is scientific and reasonable, simple and easy to implement, and the cost of obtaining the zero-sequence voltage is low, and can reduce the physical size of related equipment, and is suitable for including multiple outgoing lines The distribution network system with one busbar is used for grounding line selection protection when a single-phase ground fault occurs. It is mainly used for automatic control systems and measurement systems that need to extract zero-sequence voltage when grounding occurs in a 6-35kv distribution network. When a single-phase ground fault occurs, the zero-sequence voltage of the system is extracted for detection, alarm, measurement and corresponding automatic processing procedures of the ground fault.

detailed description

The present invention will be further described below using specific embodiments.

A method based on two single-phase voltage transformers to extract the zero-sequence voltage of a distribution network when a single-phase is grounded, including the following:

1) Before and after the ground fault, the selection steps of the reference vector: it is used to use the first single-phase voltage transformer according to the law that the phase amplitude of the line voltage basically does not change in the relevant electrical quantities before and after the ground fault. Transform the primary line voltage and send it to the analog quantity acquisition terminal of the equipment, and use the collected electrical quantity as the reference vector Vr;

2) Steps for forming the first vector VV1: use the second single-phase voltage transformer to transform the primary a-phase voltage and send it to the analog quantity acquisition terminal of the equipment. The reference vector of Vr is compared to form the first vector VV1 for analysis and calculation;

3) Forming step of the second vector VV2: use the second single-phase voltage transformer to transform the voltage of phase a and send it to the analog quantity acquisition terminal of the equipment. The reference vector Vr is compared to form the second vector VV2 for analysis and calculation;

4) The selection principle of the t1 moment of the step 2) and the t2 of the step 3) is: t2-t1=20 milliseconds, which is a power frequency cycle difference.

5) The acquisition time and sampling rate of the electrical measurement Vp1 of the step 2) and the electrical measurement Vp2 of the step 3) are determined: the acquisition time is a continuous 20 milliseconds; the sampling rate is specified as 3200.

6) The step of calculating the zero-sequence voltage vector: according to the vector difference between the first vector VV1 and the second vector VV2, calculate the zero-sequence voltage V0 at the time of grounding, namely:

V0=VV2-VV1.

The reference vector Vr in the step 1) is the secondary measurement value of the phase-to-phase voltage of a and b phases, or the secondary measurement value of the phase-to-phase voltage of b and c phases, or the secondary measurement value of the phase-to-phase voltage of c and a phases.

The first vector VV1 forming step of said step 2) further includes:

The electrical quantity reference vector Vr and the phase a voltage electrical measurement Vp1 are collected synchronously at time t1;

Simultaneous Fourier transformation of the electrical quantity reference vector Vr and the electrical measurement Vp1 of phase a voltage;

The amplitude of the Fourier transform of phase a voltage electrical measurement Vp1 is taken as the amplitude of the first vector VV1, and the electrical quantity is the angle between the reference vector Vr and the electrical measurement Vp1 of phase a voltage as the phase angle of VV1.

The second vector VV2 forming step of said step 3) further includes:

The electrical quantity reference vector Vr and the phase a voltage electrical measurement Vp2 are collected synchronously at time t2;

Simultaneous Fourier transformation of the electrical quantity reference vector Vr and the electrical measurement Vp2 of the a-phase voltage;

Phase a voltage electrical measurement Vp2 is the amplitude of the Fourier transform of the second vector VV2, and the angle between the electrical quantity reference vector Vr and phase a voltage electrical measurement Vp2 is used as the phase angle of the second vector VV2.

The step 2) and step 3) are the voltage transformation of the second single-phase voltage transformer to the primary a-phase voltage, or the voltage transformation of the second single-phase voltage transformer to the primary b-phase voltage, or the second branch The single-phase voltage transformer converts the voltage of the primary c-phase voltage.

The present invention is based on the method for extracting the zero-sequence voltage when the ground fault occurs with two single-phase transformers. The single-phase voltage transformer and various measuring instruments used are commonly used detection instruments in the field. Both the Fourier transform of the electric measurement Vp1 of the phase a voltage and the Fourier transformation of the electric measurement Vp2 of the phase a voltage adopt the Fourier product transform, which is a technique familiar to those skilled in the art.

The specific embodiments of the present invention are not intended to limit the present invention. Without departing from the spirit and essence of the present invention, those skilled in the art can make various corresponding changes and deformations according to the present invention, but these corresponding Changes and deformations should all belong to the protection scope of the claims of the present invention.

Claims (5)

1. A method based on two single-phase voltage transformers extracting the zero-sequence voltage of distribution network single-phase grounding, it is characterized in that, it comprises the following content: 1) Before and after the ground fault, the selection steps of the reference vector: it is used to use the first single-phase voltage transformer according to the law that the phase amplitude of the line voltage basically does not change in the relevant electrical quantities before and after the ground fault. Transform the primary line voltage and send it to the analog quantity acquisition terminal of the equipment, and use the collected electrical quantity as the reference vector Vr; 2) Steps for forming the first vector VV1: use the second single-phase voltage transformer to transform the primary a-phase voltage and send it to the analog quantity acquisition terminal of the equipment. The reference vector Vr is compared to form the first vector VV1 for analysis and calculation; 3) Forming step of the second vector VV2: use the second single-phase voltage transformer to transform the voltage of phase a and send it to the analog quantity acquisition terminal of the equipment. The reference vector Vr is compared to form the second vector VV2 for analysis and calculation; 4) the t1 moment of described step 2) and the selection principle of t2 of step 3) are: t2-t1=20 milliseconds, promptly differ a power frequency cycle; 5) the acquisition time and sampling rate determination of the electrical measurement Vp1 of the step 2) and the electrical measurement Vp2 of the step 3): the acquisition time is continuous 20 milliseconds; the sampling rate is defined as 3200; 6) The step of calculating the zero-sequence voltage vector: according to the vector difference between the first vector VV1 and the second vector VV2, calculate the zero-sequence voltage V0 at the time of grounding, namely: V0=VV2-VV1. 2. the method for zero-sequence voltage when extracting distribution network single-phase grounding based on two single-phase voltage transformers according to claim 1, is characterized in that, the reference vector Vr of described step 1) is a, b phase The secondary measurement value of the phase-to-phase voltage, or the secondary measurement value of the phase-to-phase voltage of b and c phases, or the secondary measurement value of the phase-to-phase voltage of c and a phases. 3. the method for extracting the zero-sequence voltage when the single-phase grounding of distribution network is based on two single-phase voltage transformers according to claim 1, it is characterized in that, the first vector VV1 forming step of described step 2) further comprises : The reference vector Vr and phase a voltage electrical measurement Vp1 are collected synchronously at time t1; Simultaneous Fourier transformation of the reference vector Vr and the electrical measurement Vp1 of phase a voltage; The magnitude of the Fourier transform of phase a voltage electrical measurement Vp1 is taken as the magnitude of the first vector VV1, and the angle between the reference vector Vr and phase a voltage electrical measurement Vp1 is taken as the phase angle of VV1. 4. the method for extracting the zero-sequence voltage when single-phase grounding of distribution network based on two single-phase voltage transformers according to claim 1, is characterized in that, described step 3) the second vector VV2 forming step further comprises : The reference vector Vr and the electrical measurement Vp2 of phase a voltage are collected synchronously at time t2; Simultaneous Fourier transformation of the reference vector Vr and the electrical measurement Vp2 of the phase a voltage; Phase a voltage electrical measurement Vp2 is the amplitude of the Fourier transform of the second vector VV2, and the angle between the reference vector Vr and phase a voltage electrical measurement Vp2 is used as the phase angle of the second vector VV2. 5. The method for extracting the zero-sequence voltage when the distribution network is single-phase grounded based on two single-phase voltage transformers according to claim 1, is characterized in that, described step 2) and step 3) second branch single-phase The voltage transformation of the voltage transformer to the primary a-phase voltage, or the voltage transformation of the second single-phase voltage transformer to the primary b-phase voltage, or the voltage transformation of the second single-phase voltage transformer to the primary c-phase voltage.