CN102590703A - Single-phase grounding failure route selection method of resonance grounding system based on zero-sequence transient charge - Google Patents

Abstract

The invention discloses a single-phase grounding failure route selection method of a resonance grounding system based on zero-sequence transient charge, comprising the main steps: collecting a three-phase current signal and a three-phase voltage signal of a distribution network feeder bus as input quantity of a route selection element; performing decoupling calculation to obtain zero-sequence current and zero-sequence voltage of the feed lines, and filtering the power frequency component in the corresponding electric quantity; figuring out zero-sequence transient charge quantity accumulated during a failure transient process according to the zero-sequence transient current of the feed lines; and comparing the relative coefficient values of the obtained zero-sequence transient voltage with the zero-sequence transient electric charge quantity of the feed lines to judge whether the feed line with minimal relative coefficient is the failure feed line, so as to finish the identification of the failure feed line. The method disclosed by the invention can reliably identify the failure feed line under various failure conditions, an emulation result indicates that the method has high sensitivity and reliability under various operation working conditions, and the method has good anti-interference capability and has no special demand on equipment, so that the method can be used for realizing fast failure diagnosis of the resonance grounding system.

Description

Single-phase-to-ground fault line selection method for resonant grounded system based on zero-sequence transient charge

technical field

The invention relates to a single-phase grounding fault line selection method for a resonant grounding system based on zero-sequence transient charges in a power system.

Background technique

At present, the resonant grounding system using arc-suppression coil can extinguish the grounding arc by itself because the fault current is compensated by the arc-suppression coil after a single-phase ground fault occurs on the line, and the fault current becomes smaller. The line voltage is symmetrical in three phases and does not affect the power supply capacity to the load, so it is allowed to run for 1-2 hours with electricity. However, with the development of the distribution network, the number of bus feeders increases year by year and the use of cables in the line increases the short-circuit capacitor current, and multi-point grounding faults are likely to occur during long-term operation. Therefore, it is necessary to quickly and accurately determine the The fault feeder provides the basis for the precise location and troubleshooting of further faults.

For the fault line selection of the resonant grounding system of the distribution network, although the energy of the power frequency is large, it is compensated by the arc suppression coil, and the amplitude and direction of the fundamental wave component will change greatly. Based on this reason, the transient state generated after the fault is analyzed The realization of the line selection method based on transient information has gradually become a research and practical hotspot. However, the high-resistance grounding fault in the distribution network has always been a difficult point in line selection, because the grounding resistance is too large, and the amplitude of the transient quantity after the fault is very small, which makes it very difficult to accurately select the line after the fault in the resonant grounding system.

Contents of the invention

The purpose of the present invention is to overcome the deficiencies in the fault line selection of the existing distribution network resonant grounding system, and propose a single-phase ground fault line selection method for the resonant grounding system based on zero-sequence transient charges. With high sensitivity and fast speed, it can provide more accurate and reliable basis for further precise fault location and troubleshooting.

In order to solve the technical problem, the technical solution adopted by the present invention is a single-phase grounding fault line selection method for a resonant grounding system based on zero-sequence transient charge, the steps of which are as follows:

A. Collect the three-phase current signals and three-phase voltage signals at the bus terminals of each feeder line in the distribution network, and select the first half-cycle or full-cycle three-phase current signals and three-phase voltage signals of each feeder line after a single-phase ground fault The sampling data is used as the input quantity of the line selection element;

B. Decoupling the input quantity of the selected line selection element to obtain the zero-sequence current component and zero-sequence voltage component of each feeder line;

C. Filter out the 50Hz power frequency components in the zero-sequence current and zero-sequence voltage of each feeder to obtain the corresponding zero-sequence transient current and zero-sequence transient voltage, and calculate the selection according to the zero-sequence transient current of each feeder The amount of zero-sequence transient charge accumulated on the feeder in the first half cycle or the full cycle time;

D. Establish the corresponding relationship between the zero-sequence transient charge and the zero-sequence transient voltage of each feeder, and calculate the correlation coefficient between the transient zero-sequence voltage and the zero-sequence transient charge of each feeder. The feeder with the smallest correlation coefficient is determined as Faulty feeder.

Compared with prior art, the beneficial effect of the present invention is:

One, the present invention passes through the relative relationship between the distribution of the accumulated transient charge in each feeder and the transient voltage change of each feeder in half or one cycle, because the transient information used is accumulated, it improves the detection of weak signals The identification ability overcomes the shortcoming of too small transient current information caused by high-impedance grounding faults, solves the problem of inaccurate line selection caused by extremely weak transient electrical quantities in the case of high-impedance grounding, and improves the high-impedance grounding system of resonant grounding systems. Sensitivity and accuracy of line selection.

2. A single-phase grounding fault in a resonant grounding system will produce two transient processes at the same time. One is the discharge capacitor current caused by the sudden drop of the fault phase voltage, and the other is the charge capacitor current caused by the sudden increase of the non-fault phase voltage. The discharge capacitor current flows to the fault point through the bus bar, and directly passes through the fault phase line to ground capacitance and ground to form a circulation loop, while the charge capacitor current passes through the transformer and then passes through the non-fault phase line to ground capacitance and ground to form a path. The present invention examines the correlation coefficient values of different feeders by obtaining the distribution relationship between the total charge accumulated in the first half cycle or the full cycle of the two transient charging and discharging processes and the corresponding transient voltage, and the correlation coefficient value The closer to 1, it reflects that the load of the feeder is stable and the disturbance is small; on the contrary, the value of the correlation coefficient is smaller than 1, indicating that its load has undergone a sudden change or has been disturbed; therefore, the feeder with the smallest correlation coefficient value after a fault can be judged as a fault line. It does not need to directly identify the direction and magnitude of the transient current, and the line selection criterion is simple and easy to operate on site.

3. Since the accumulated transient charge is formed by the charging and discharging transient process generated by itself when a single-phase ground fault occurs in the resonant grounding system, it is not affected by the compensation degree of the neutral point of the system, which also makes the line selection accurate and reliable; and Only the three-phase current and voltage of each feeder on the bus side need to be collected, and the requirements for equipment are not high. Similarly, the reliability of the method is improved.

4. The present invention only needs to collect the transient quantity of the capacitor charging and discharging process when the single-phase is grounded, usually between several hundred to several thousand hertz, so the sampling frequency range is 10 kHz to 20 kHz, and there is no special requirement for the sampling equipment, which is convenient implement.

In the above step C, according to the zero-sequence transient current of each feeder, the specific method of calculating the zero-sequence transient charge accumulated on the feeder in the selected first half cycle or full cycle is as follows;

According to the following discrete integral formula, the accumulated charge in the i-th sampling interval from the occurrence of a single-phase fault is obtained

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; -</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}$

或i＝T/Δt时，T为三相电的周期，算出的电荷量

即为第一个半周期或全周期时间内累积在第n条馈线上的零序暂态电荷量

In the formula, is the zero-sequence transient current collected at the i-th sampling interval of the n-th feeder, and Δt is the sampling interval time; when

Or when i=T/Δt, T is the cycle of the three-phase electricity, the calculated amount of charge

That is, the zero-sequence transient charge accumulated on the nth feeder in the first half cycle or the whole cycle

This method can be used to conveniently and quickly calculate the zero-sequence transient charge accumulated by each feeder within the selected time.

The present invention will be further described in detail below in combination with specific embodiments.

Description of drawings

Fig. 1 is the topology structure of the simulation model of the simulation experiment of the embodiment of the present invention.

Fig. 2 is the relationship between the zero-sequence transient charge and the zero-sequence transient voltage of feeders 1-4 in the simulation experiment of the embodiment of the present invention.

Detailed ways

Example

A specific embodiment of the present invention is a method for line selection of a single-phase ground fault in a resonant ground system based on zero-sequence transient charges, the steps of which are as follows:

A. Collect the three-phase current signals and three-phase voltage signals at the bus terminals of each feeder line in the distribution network, and select the first half-cycle (ie 10ms) or full-cycle (20ms) three-phase current signals of each feeder line after a single-phase fault and the sampling data of the three-phase voltage signal as the input quantity of the line selection element.

B. Decoupling the input quantity of the selected line selection element to obtain the zero-sequence current component and zero-sequence voltage component of each feeder line respectively.

When decoupling, various existing decoupling methods can be used, such as symmetrical component transformation, as follows:

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="I"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">I</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; \&alpha;</span>}& {\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& {\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}& \mathrm{<span\; class="notranslate">\; \&alpha;</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}\\ {\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}\\ {\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

$\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 1</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}\end{array}\right]<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 3</span>}}\left[\begin{array}{ccc}\mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; \&alpha;</span>}& {\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& {\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}& \mathrm{<span\; class="notranslate">\; \&alpha;</span>}\\ \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}& \mathrm{<span\; class="notranslate">\; 1</span>}\end{array}\right]\left[\begin{array}{c}{\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; A</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; B</span>}}\\ {\mathrm{<span\; class="notranslate">\; u</span>}}_{\mathrm{<span\; class="notranslate">\; C</span>}}\end{array}\right]<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 2</span>}<span\; class="notranslate">\; )</span>$

In formula (1), I _A , I _B , and I _C are the A, B, and C phase currents measured by each feeder at the busbar; I ₀ is the zero-sequence current; I ₁ is the positive-sequence current; I ₂ is negative sequence current.

In formula (2), U _A , U _B , and U _C are the A, B, and C phase voltages measured by each feeder at the busbar; U ₀ is the zero-sequence voltage; U ₁ is the positive-sequence voltage; U ₂ is Negative sequence voltage.

In formulas (1) and (2), α is the rotation factor, and its expression is:

$\mathrm{<span\; class="notranslate">\; \&alpha;</span>}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{{\mathrm{<span\; class="notranslate">\; j</span>}\mathrm{<span\; class="notranslate">\; 120</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; +</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 3</span>}<span\; class="notranslate">\; )</span>$

${\mathrm{<span\; class="notranslate">\; \&alpha;</span>}}^{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; e</span>}}^{\mathrm{<span\; class="notranslate">\; j</span>}{\mathrm{<span\; class="notranslate">\; 240</span>}}^{\mathrm{<span\; class="notranslate">\; 0</span>}}}<span\; class="notranslate">\; =</span><span\; class="notranslate">\; -</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; j</span>}\frac{\sqrt{\mathrm{<span\; class="notranslate">\; 3</span>}}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 4</span>}<span\; class="notranslate">\; )</span>$

Through the above symmetrical component conversion, the asymmetrical current and voltage information after a single-phase ground fault occurs is transformed into three symmetrical sequence components, among which the obtained feeder zero-sequence current component I ₀ and zero-sequence voltage component U ₀ are the next step. information needed.

C. Filter out the 50Hz power frequency components in the zero-sequence current and zero-sequence voltage of each feeder to obtain the corresponding zero-sequence transient current and zero-sequence transient voltage, and calculate the selection according to the zero-sequence transient current of each feeder The amount of zero-sequence transient charge accumulated on the feeder during the first half cycle or the full cycle of a given period.

In this example, according to the zero-sequence transient current of each feeder, the specific method of calculating the zero-sequence transient charge accumulated on the feeder in the selected first half cycle or full cycle is as follows;

According to the following discrete integral formula, the accumulated charge in the i-th sampling interval from the occurrence of a single-phase fault is obtained

${\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>{\mathrm{<span\; class="notranslate">\; Q</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; +</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 2</span>}}<span\; class="notranslate">\; \&times;</span><span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 1</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; +</span>{\mathrm{<span\; class="notranslate">\; I</span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}\mathrm{<span\; class="notranslate">\; i</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span><span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; \&Delta;t</span>}$

为第n条馈线的第i个采样间隔采集的零序暂态电流，Δt为采样间隔的时间；当

或i＝T/Δt时，T为三相电的周期(20ms)，算出的电荷量

即为第一个半周期或全周期时间内累积在第n条馈线上的零序暂态电荷量

In the formula,

is the zero-sequence transient current collected at the i-th sampling interval of the n-th feeder, and Δt is the sampling interval time; when

Or when i=T/Δt, T is the period of the three-phase electricity (20ms), the calculated amount of charge

That is, the zero-sequence transient charge accumulated on the nth feeder in the first half cycle or the whole cycle

D. Establish the corresponding relationship between the zero-sequence transient charge and the zero-sequence transient voltage of each feeder, and calculate the correlation coefficient between the transient zero-sequence voltage and the zero-sequence transient charge of each feeder. The feeder with the smallest correlation coefficient is determined as Faulty feeder.

The calculation formula of the correlation coefficient between the transient zero-sequence voltage and the zero-sequence transient charge of each feeder is:

${\mathrm{<span\; class="notranslate">\; \&rho;</span>}}_{\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; Cov</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="u"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">u</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; ,</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="Q"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">Q</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>}{\sqrt{\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="u"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">u</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>}<span\; class="notranslate">\; \&CenterDot;</span>\sqrt{\mathrm{<span\; class="notranslate">\; D.</span>}<span\; class="notranslate">\; (</span>{\mathrm{<span\; class="notranslate">\; <figure-callout\; id="0"\; label="Q"\; filenames="HDA0000136620350000012.png"\; state="\{\{state\}\}">Q</figure-callout></span>}}_{\mathrm{<span\; class="notranslate">\; 0</span>}}^{<span\; class="notranslate">\; \&prime;</span>\mathrm{<span\; class="notranslate">\; no</span>}}<span\; class="notranslate">\; )</span>}}$

表示第n条馈线的零序暂态电压量和零序暂态电荷量的协方差，

表示第n条馈线的零序暂态电压量的方差，

表示第n条馈线的零序暂态电荷量的方差。In the formula, ρ _n represents the correlation coefficient between the zero-sequence transient voltage and the zero-sequence transient charge of the nth feeder,

Indicates the covariance of the zero-sequence transient voltage and zero-sequence transient charge of the nth feeder,

Indicates the variance of the zero-sequence transient voltage of the nth feeder,

Indicates the variance of the zero-sequence transient charge of the nth feeder.

Simulation:

In order to verify the method of the present invention, a simulation experiment has been carried out on the above method, and the simulation experiment results show that its line selection sensitivity is high, the line selection speed is fast, and the line selection is accurate and reliable.

Combined with the parameters of an actual operating line, a single power supply 4-feeder resonant grounding system with a voltage level of 35kV is built as an experimental model, and the line is a frequency-dependent overhead line model. Its topology is shown in Figure 1. The relevant parameters are: the length of feeder 1 is 30 km, the length of feeder 2 is 19 km, the length of feeder 3 is 10 km, and the length of feeder 4 is 6 km. Positive and negative sequence impedance Z ₁ = Z ₂ = 0.25542+j0.37294Ω/km of overhead lines, positive and negative sequence admittance Y ₁ = Y ₂ = j3.0803×10 ^-6 s/km, zero sequence impedance Z ₀ ＝0.51664+j1.48516Ω/km, zero-sequence admittance Y ₀ ＝j1.47574326×10 ^-6 s/km, the arc suppression coil compensation degree is set to overcompensation 10%, and the signal acquisition device is installed at the busbar end of each feeder line Carry out data acquisition of three-phase fault current and three-phase fault voltage.

The data sampling rate is 20kHz, and the length of the data window is 414 points, that is, one period. Assume that the feeder 1 has a phase A ground fault at t=0.3243s at a distance of l=18km from the busbar, and the transition resistance R=2000Ω. Then it can be calculated: the zero-sequence transient charge accumulated by feeder 1-4 in the first period, the corresponding correlation coefficient value of zero-sequence transient charge and zero-sequence transient voltage ρ ₁ =-0.1084, ρ ₂ = 0.9992, ρ ₃ =0.9986, ρ ₄ =0.9951. According to the criterion condition, ρ ₁ is the smallest, so feeder 1 is the fault feeder. Figure 2 is the relationship curve between the zero-sequence transient charge and the zero-sequence transient voltage accumulated at each moment of the first cycle of feeders 1-4. The curves in Figure 2 that tend to be linear distribution are feeders 2, 3, and 4 , and the curve with irregular distribution is the fault feeder curve, which also shows that the zero-sequence transient charge and zero-sequence transient voltage on feeders 2, 3, and 4 are highly linearly positively correlated, while the zero-sequence transient voltage on feeder 1 There is no obvious correlation between the amount of transient charge and the zero-sequence transient voltage.

Table 1 and Table 2 below show the line selection results of the method of the present invention under the working conditions of different fault distances and different fault grounding resistances.

Table 1 compares the line selection results when a phase A ground fault occurs on feeder 1 at different distances (fault occurrence time is 0.3243s, transition resistance R=2800Ω):

Table 1

√: Indicates that the protection line selection result is consistent with the actual fault feeder setting result

Table 2 is the comparison of line selection results for feeder 1 when phase A ground fault occurs with different ground resistance (fault occurrence time is 0.3243s, fault distance l=15km).

Table 2

√: Indicates that the protection line selection result is consistent with the actual fault feeder setting result

The line selection results in Table 1 and Table 2 show that under various working conditions of fault distance and fault grounding resistance, the correlation degree between the zero-sequence transient charge and zero-sequence transient voltage of the faulted feeder is significantly lower than that of the healthy feeder . The line selection result is accurate and easy for operators to read, which proves that the inventive method has high reliability and practicability.

The above experiments did not consider the influence of noise. In order to verify the adaptability of the present invention in practical engineering applications, Gaussian white noise was superimposed on the collected three-phase current and voltage signals to simulate signal interference that may occur in practical applications to verify the present invention. Invented line selection reliability under low signal-to-noise ratio.

A single-phase ground fault occurs at 20km away from the busbar on feeder 1, and the data sampling rate is 20kHz. The length of the data window is 414 sampling points (one cycle) after the fault (t=0.3243s). Comparison of line selection results in the case of Signal-to-noise ratio (SNR).

table 3

√: Indicates that the protection line selection result is consistent with the actual fault feeder setting result

The experimental results of adding Gaussian noise show that the fault line selection can be completed correctly when the signal-to-noise ratio of the input signal is from 10dB to 70dB. However, it can be found that when the signal-to-noise ratio is above 40dB, the correlation coefficients between the zero-sequence transient charge and the zero-sequence transient voltage of the healthy feeder are all above 0.95, indicating that the distribution of the zero-sequence transient charge of the healthy feeder and the zero-sequence transient The voltage change is highly linear. As the signal-to-noise ratio decreases, the noise has a greater impact on the effective information of the electric quantity, and the corresponding correlation coefficient value of the charge quantity distribution of the fault feeder and the healthy feeder also changes greatly. But the correlation coefficient value of the faulty feeder is always significantly lower than that of the healthy feeder. Based on the analysis of the above failure conditions, it is shown that the line selection sensitivity of the present invention is high, the anti-interference ability is strong, and it can be adapted to the actual application in the field.

Claims (2)

1. the resonant earthed system fault line selection method for single-phase-to-ground fault based on zero sequence transient state electric charge the steps include:

A, gather the three-phase current signal and the three-phase voltage signal of each bar feeder line bus end of power distribution network, the sampled data of first semiperiod or holocyclic three-phase current signal and three-phase voltage signal of choosing each bar feeder line behind the singlephase earth fault is as the input quantity of route selection element;

B, the input quantity of the route selection element chosen is carried out decoupling zero, obtain the zero-sequence current component and the zero sequence voltage component of each bar feeder line respectively;

50Hz power frequency component in C, each bar feeder line zero-sequence current of filtering and the residual voltage; Obtain corresponding zero sequence transient current and zero sequence transient voltage, and obtain the zero sequence transient state quantity of electric charge that is accumulated in first selected semiperiod or time in complete period on each bar feeder line according to the zero sequence transient current of each bar feeder line;

D, set up the corresponding relation of each bar feeder line zero sequence transient state quantity of electric charge and zero sequence transient voltage, calculate the related coefficient of the transient state residual voltage and the zero sequence transient state quantity of electric charge of each bar feeder line, the minimum feeder line of related coefficient is judged to be fault feeder.

2. the resonant earthed system fault line selection method for single-phase-to-ground fault based on zero sequence transient state electric charge according to claim 1; It is characterized in that: described C is in the step, obtains the specific practice that is accumulated in the zero sequence transient state quantity of electric charge on each bar feeder line in first selected semiperiod or time in complete period according to the zero sequence transient current of each bar feeder line and is:

Draw the singlephase earth fault charges accumulated amount

in time in i SI that begins that takes place by following discrete integration formula

$Q_{0i}^{\&prime;n}=Q_{0i-1}^{\&prime;n}+\frac{1}{2}\&times;(I_{0i-1}^{\&prime;n}-I_{0i}^{\&prime;n})\&times;\mathrm{\&Delta;t}$

In the formula;

is the zero sequence transient current of gathering in i the SI of n bar feeder line, and Δ t is the time in SI; When

or i=T/ Δ t; T is the cycle of three-phase electricity, and the quantity of electric charge of calculating is the zero sequence transient state quantity of electric charge

that is accumulated in first semiperiod or time in complete period on the n bar feeder line

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