CN108051675B - High-altitude area 35kV and below live-line switching no-load line research method - Google Patents

Abstract

The invention belongs to the technical field of live-line work overhaul, and particularly relates to a method for researching a live-line switching no-load line of 35kV or below in a high-altitude area. According to the invention, simulation and experimental research are carried out on the capacitance current of 35kV, 20kV and 10kV switching no-load lines in the high-altitude area, the influence on overvoltage and overcurrent in the switching process of different voltage classes is analyzed, the discharge characteristic and the arc attenuation characteristic of the switching no-load lines are confirmed, the working condition of the 35kV and below line live-line switching no-load lines in the high-altitude area is determined, the blank of the 35kV and below line live-line switching no-load line working in the high-altitude area is filled, a basis is provided for improving the safety of the 35kV and below line live-line working in the high-altitude area, and a positive effect is played on promoting the development of the 35kV and below line live-line working in the high-altitude area.

Description

High-altitude area 35kV and below live-line switching no-load line research method

Technical Field

The invention belongs to the technical field of live-line work overhaul, and particularly relates to a research method for live-line switching no-load lines of 35kV and below in a high-altitude area.

Background

In the aspect of live-line work, domestic electric power supply enterprises or related research units do not report research and analysis on the influence of factors such as the altitude and the humidity of live-line work of lines of 35kV and below in a high-altitude area on disconnection of unloaded lines. Therefore, how to provide technical support for the development of live-line work on lines of 35kV and below in high-altitude areas and serve the first-class work of companies is a problem which is urgently needed to be solved for live-line maintenance of lines of 35kV and below.

Disclosure of Invention

Aiming at the problems in the prior art, the invention provides a research method for a live-line switching no-load line of 35kV and below in a high-altitude area, and provides a relation among a fracture distance, a capacitance current value and a voltage value which influence operation maintenance when the no-load line is switched under the weather conditions of 35kV, 20kV and 10kV altitudes, so that safe live-line maintenance is realized.

The technical scheme is as follows:

the method for researching the 35kV and the following electrified switching no-load lines in the high-altitude area is carried out according to the following steps:

(1) determining altitude and humidity conditions:

the relevant experiments were carried out under the following five conditions of altitude:

A. selecting a value from a natural environment with an altitude of 1800m-2000m, wherein the humidity is natural humidity;

B. selecting a value in a natural environment with an altitude of 3000m-3500m, wherein the humidity is natural humidity;

C. simulating an altitude value corresponding to a natural environment with an altitude of 1800m-2000m in a simulated climate laboratory, wherein the humidity is 80%;

D. simulating an altitude value corresponding to a natural environment with an altitude of 3000m-3500m in a simulated climate laboratory, wherein the humidity is 80%;

E. simulating a natural environment with an altitude of 4000m in a simulated climate laboratory, wherein the humidity is 80%;

(2) simulation research of switching capacitance and current:

A. determining a simulation model:

establishing a simulation model by using ATP-EMTP simulation software, selecting an LCC power transmission line model (a pure cable line and an overhead line), adopting a common standard tower type of a 10kV-35kV system, adopting a common standard type of a lead, selecting 500-2000 omega-m soil resistivity, selecting an ideal infinite power supply system as the system, and selecting a time control switch as an isolating switch;

B. carrying out simulation research:

a. establishing a switching no-load line model by using ATP-EMTP, and performing electromagnetic transient simulation on a no-load line switching the same voltage within the range of 10kV to 35kV at the same altitude, wherein the capacitance current values of the no-load line are respectively selected to be 0.1A, 0.2A, 0.3A, 0.4A and 0.5A;

when the fixed closing angle of the isolating switch is 90 degrees, observing the condition that the opening angles of the isolating switch are different, and determining the influence of the opening angles on overvoltage and overcurrent;

when the fixed opening angle of the isolating switch is 270 degrees, namely the residual voltage is-Em, observing the condition that the closing angle of the isolating switch is different, and determining the influence of the closing angle on overvoltage and overcurrent;

b. building a switching no-load line model by using ATP-EMTP, and performing electromagnetic transient simulation on the no-load lines switched with different voltages within the range of 10kV to 35kV under the altitude condition in the step (1), wherein the capacitance current values of the no-load lines are respectively selected to be 0.1A, 0.2A, 0.3A, 0.4A and 0.5A;

setting the distance between contacts of the disconnecting switch to be 240mm, comparing the medium strength recovery voltage with the arc gap recovery voltage, setting to obtain a time region in which the electric arc can be reignited, summarizing the influence of one-time reignition and multiple reignitions of the electric arc on the amplitude of the overvoltage by using a power frequency arc extinguishing theory and a high-frequency theory, and recording the maximum overvoltage level and the maximum transient overcurrent level under the conditions of one-time reignition and the most severe reignition;

c. building a switching no-load line model by using ATP-EMTP, and researching the arc attenuation characteristics under the conditions of switching 10kV and 0.2m/s in the altitude condition in the step (1);

(3) switching capacitance current test research:

A. determining the test equipment:

selecting a capacitor bank, a power frequency test transformer, an isolating switch and a high-speed camera to form a simulated actual circuit, and simulating the no-load capacitive current working condition of a disconnected 10kV-35kV circuit to perform a test, wherein the power frequency test transformer is connected with the capacitor bank through a circuit, the isolating switch is arranged on the circuit, and the high-speed camera is aligned to the isolating switch and is matched with a high-speed camera and a recorder for use;

B. carrying out experimental study:

a. three voltage working conditions are created by using a power frequency test transformer, a three-phase asynchronous speed reduction motor drives an isolating switch to be switched on and off, live working is simulated, and the capacitance current values of a no-load circuit are respectively selected to be 0.1A, 0.2A, 0.3A, 0.4A and 0.5A;

b. performing a separation and combination test on the combination of the same voltage and different capacitive currents under the altitude and humidity conditions in the step (1), controlling the opening speed and the opening distance by adjusting the on-time and the power frequency, determining the speed by adopting a high-speed camera, recording the overvoltage and overcurrent values by adopting a recorder, recording the arc discharge process by adopting a high-speed camera, and measuring the arc length;

(4) the research conclusion is drawn:

and comparing the voltage values in the simulation research and the test research to obtain the voltage difference between the time operation and the simulation operation, and analyzing the factors causing the difference.

The invention has the beneficial effects that:

according to the invention, simulation and experimental research are carried out on the capacitance current of 35kV, 20kV and 10kV switching no-load lines in the high-altitude area, the influence on overvoltage and overcurrent in the switching process of different voltage classes is analyzed, the discharge characteristic and the arc attenuation characteristic of the switching no-load lines are confirmed, the working condition of the 35kV and below line live-line switching no-load lines in the high-altitude area is determined, the blank of the 35kV and below line live-line switching no-load line working in the high-altitude area is filled, a basis is provided for improving the safety of the 35kV and below line live-line working in the high-altitude area, and a positive effect is played on promoting the development of the 35kV and below line live-line working in the high-altitude area.

Drawings

FIG. 1 is a bus overvoltage level curve when a fixed closing angle is 90 degrees and an opening angle is 0 degrees;

FIG. 2 is a horizontal curve of bus overcurrent when the fixed closing angle is 90 DEG and the opening angle is 0 DEG;

FIG. 3 is a bus overvoltage level curve when the fixed switching-on angle is 90 degrees and the switching-off angle is 90 degrees;

fig. 4 is a bus overcurrent horizontal curve when the fixed closing angle is 90 ° and the opening angle is 90 °;

FIG. 5 is a bus overvoltage level curve when the fixed closing angle is 90 degrees and the opening angle is 180 degrees;

FIG. 6 is a horizontal curve of bus overcurrent when the fixed switching-on angle is 90 degrees and the switching-off angle is 180 degrees;

fig. 7 is a bus overvoltage level curve when the fixed closing angle is 90 ° and the opening angle is 270 °;

fig. 8 is a bus overvoltage level curve when the fixed closing angle is 90 ° and the opening angle is 270 °;

fig. 9 is a statistical chart of overvoltage levels generated by different opening angles when the fixed closing angle is 90 degrees;

fig. 10 is a statistical chart of the overcurrent levels generated at different opening angles when the fixed closing angle is 90 °;

fig. 11 is a bus overvoltage level curve when the fixed opening angle is 270 ° and the closing angle is 0 °;

fig. 12 is a bus overcurrent horizontal curve when the fixed opening angle is 270 ° and the closing angle is 0 °;

fig. 13 is a bus overvoltage level curve when the fixed opening angle is 270 ° and the closing angle is 90 °;

fig. 14 is a bus overcurrent horizontal curve when the fixed opening angle is 270 ° and the closing angle is 90 °;

fig. 15 is a bus overcurrent horizontal curve when the fixed opening angle is 270 ° and the closing angle is 180 °;

fig. 16 is a bus overcurrent horizontal curve when the fixed opening angle is 270 ° and the closing angle is 180 °;

fig. 17 is a bus overcurrent horizontal curve when a fixed opening angle is 270 ° and a closing angle is 270 °;

fig. 18 is a bus overcurrent horizontal curve when the fixed opening angle is 270 ° and the closing angle is 270 °;

fig. 19 is a statistical chart of overvoltage levels generated by different closing angles when the fixed opening angle is 270 °;

fig. 20 is a statistical chart of the overcurrent levels generated at different closing angles when the fixed opening angle is 270 °;

FIG. 21 is a bus overvoltage level curve when the capacitance current is 0.5A under the theory of power frequency arc quenching of a 10kV power distribution network no-load line;

FIG. 22 is a bus overcurrent level curve when the capacitance current is 0.5A under the theory of power frequency arc-quenching of a 10kV power distribution network no-load line;

FIG. 23 is a bus overvoltage level curve when a restrike occurs at a capacitance current of 0.3A under a 10kV power distribution network no-load line high frequency theory is cut off;

FIG. 24 is a bus overcurrent level curve when a reignition occurs once when the capacitance current is 0.3A under the high frequency theory of 10kV power distribution network no-load line cut-off;

FIG. 25 is a bus overvoltage level curve when multiple restriking is performed when the capacitance current is 0.3A under the high frequency theory of 10kV power distribution network no-load line cutoff;

FIG. 26 is a bus overcurrent level curve when the high frequency theory of 10kV power distribution network no-load line is cut off and the capacitance current is 0.3A, and multiple reignitions are performed;

FIG. 27 is a simplified simulation model;

FIG. 28 is a graph of the temperature field distribution isolated at 0.1A current cutoff;

FIG. 29 is a graph of the temperature field distribution isolated at 0.2A current cutoff;

FIG. 30 is a graph of the temperature field distribution isolated at 0.3A current cutoff;

FIG. 31 is a graph of the temperature field distribution isolated off when 0.4A current is turned off;

FIG. 32 is a graph of the temperature field distribution isolated at 0.5A current cutoff;

FIG. 33 is a schematic of a typical wave 1 of an experimental study;

FIG. 34 is a schematic of a typical wave 2 of an experimental study;

FIG. 35 is a schematic of a typical wave 3 of an experimental study;

FIG. 36 is a schematic of a typical wave 4 of an experimental study;

FIG. 37 is a schematic diagram of a typical wave 5 of an experimental study;

FIG. 38 is a schematic of a typical wave 6 from an experimental study;

FIG. 39 is a schematic of a typical wave 7 from an experimental study;

fig. 40 is a wiring diagram for a switching no-load line test research.

Detailed Description

The invention provides a research method for a 35kV and below live-line switching no-load line in a high altitude area, and the technical scheme in the embodiment of the invention is clearly and completely described below by combining the attached drawings in the embodiment of the invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

The method for researching the 35kV and the following electrified switching no-load lines in the high-altitude area is carried out according to the following steps:

(1) determining altitude and humidity conditions:

the relevant experiments were carried out under the following five conditions of altitude:

A. selecting a value from a natural environment with an altitude of 1800m-2000m, wherein the humidity is natural humidity;

B. selecting a value in a natural environment with an altitude of 3000m-3500m, wherein the humidity is natural humidity;

C. simulating an altitude value corresponding to a natural environment with an altitude of 1800m-2000m in a simulated climate laboratory, wherein the humidity is 80%;

D. simulating an altitude value corresponding to a natural environment with an altitude of 3000m-3500m in a simulated climate laboratory, wherein the humidity is 80%;

E. simulating a natural environment with an altitude of 4000m in a simulated climate laboratory, wherein the humidity is 80%;

(2) simulation research of switching capacitance and current:

simulation study example 1 (influence of opening angle on over-voltage and over-current)

Adopt ATP-EMTP simulation software, set up simulation model, take 2000m height above sea level, isolator's separating brake flows through the unloaded circuit of 10kV of 0.3A electric capacity electric current as an example, when isolator's fixed combined floodgate angle was 90, supposedly take place a relighting, observe the condition that the separating brake angle is not synchronized:

making statistics on the system overvoltage and overcurrent levels when the opening angle is 0 degrees, as shown in fig. 1 and fig. 2;

making statistics on the overvoltage and overcurrent levels of the system when the opening angle is 90 degrees, as shown in fig. 3 and 4;

making statistics on the overvoltage and overcurrent levels of the system when the opening angle is 180 degrees, as shown in fig. 5 and fig. 6;

statistics are made on the overvoltage and overcurrent levels of the system when the opening angle is 270 degrees, as shown in fig. 7 and fig. 8;

when the isolating switch is in the process of breaking the no-load circuit, the phase A is pulled open, and the reignition between the contacts of the isolating switch is the reason of the generation of the overvoltage of the no-load circuit, wherein the level of the overvoltage is determined by the residual voltage on the no-load circuit. The opening angle determines the residual voltage on the line after the contact is pulled open. When the opening angle is 0 degrees, the residual voltage on the idle line is 0, and when the closing angle is 90 degrees, the electric arc between the contacts is reignited to cause electromagnetic oscillation and overvoltage. When the opening angle is 90 degrees, the residual voltage on the no-load line is Em, the voltage difference between the residual voltage and the voltage of the bus when the closing angle is 90 degrees is not large, strong electromagnetic oscillation is difficult to cause, and the generated overvoltage phenomenon is not obvious. When the opening angle is 270 degrees, the voltage difference between the contacts is the most serious, the induced electromagnetic oscillation is the strongest, and the generated overvoltage and overcurrent levels are also the highest.

When the capacitance currents of 0.1A, 0.2A, 0.3A, 0.4A and 0.5A respectively flow through the empty load line, the generated rules are consistent, and statistics is made, as shown in fig. 9 and fig. 10.

It is known that when the switching-off angle is opposite to the switching-on angle, the overvoltage and overcurrent generated by the bus are the most serious.

Simulation study example 2 (influence of closing angle on over-voltage and over-current)

Based on the 10kV no-load line model established in example 1, taking an no-load line in which 0.3A capacitance current flows through the opening of the disconnector at an altitude of 2000m as an example, when the fixed opening angle of the disconnector is 270 °, that is, the residual voltage is-Em, it is assumed that a re-ignition occurs, and the situation that the closing angle is not simultaneous is observed.

Statistics are made on the system overvoltage and overcurrent levels when the closing angle is 0 °, as shown in fig. 11 and 12;

statistics are made on the system overvoltage and overcurrent levels when the closing angle is 90 °, as shown in fig. 13 and 14;

statistics are made on the system overvoltage and overcurrent levels when the closing angle is 180 °, as shown in fig. 15 and 16;

statistics are made on the system overvoltage and overcurrent levels when the closing angle is 270 °, as shown in fig. 17 and 18;

in this case, when the closing angle is 90 °, the generated overvoltage level and overcurrent level are the most serious. If the opening angle is set to 0 °, both the overvoltage and overcurrent levels generated when the closing angle is 90 ° and 270 ° are severe, but in this case, the closing angle is not as high as 90 °. The reason for this is that the residual charge on the lines makes the electromagnetic oscillation phenomenon worse.

When the capacitance currents of 0.1A, 0.a, 0.3A, 0.4A and 0.5A respectively flow through the empty load line, the generated rules are consistent, and statistics is made, as shown in fig. 19 and 20.

Since the time corresponding to the reignition of the arc is uncertain, the value of the corresponding overvoltage on the line is also uncertain, and therefore it is not reasonable to limit the closing overvoltage from the closing time. However, the speed of movement of the contacts is increased, meaning that the time for reignition to occur is greatly reduced, and the slow contacts that produce overvoltage and overcurrent levels are low.

Simulation study example 3 (over-voltage and over-current level study for 10kV power distribution network disconnection no-load line)

Referring to the Standard design of 10kV and 35kV distribution networks of southern Power grid company in China, in a 10kV line, a steel-cored aluminum stranded wire LGJ240/30 is adopted as an overhead line, and the length is set by a capacitance current flowing through the circuit. The bolt angle steel tower is adopted, the conducting wires are arranged in a triangular mode, the height of the tower top is 13m, the distance between two sides and the ground is 11m, the distance between a middle line and the ground is 11.7m, the distance between two side lines is 2m, the distance between the two side lines and the middle line is 1.5m, and the span is 250 m. The soil resistivity was selected to be 2000 Ω · m.

Building a switching no-load line model by using ATP-EMTP, and performing electromagnetic transient simulation on the switching 10kV no-load line under the altitude condition in the step (1);

when the distance between the contacts of the disconnecting switch is set to be 240mm, the medium strength recovery voltage and the arc gap recovery voltage are compared, and the time region of the possible reignition of the arc is obtained through setting, and is shown in the following table:

	0.1A	0.2A	0.3A	0.4A	0.5A
						2000m	0.205s	0.365s	0.675s	1.135s	1.2s
3000m	0.235s	0.415s	0.765s	1.2s	1.2s
						4000m	0.262s	0.475s	0.865s	1.2s	1.2s

using the line frequency arc quenching theory, the overvoltage and overcurrent levels were recorded, using the capacitance current value of the unloaded line as 0.5A for example, as shown in fig. 21 and 22.

Setting the switch open after the high frequency current has substantially decayed allows the maximum voltage between the interruptions to always not exceed 2Em, which means that the levels of overvoltage and overcurrent produced are not particularly high.

Under the condition of using a high-frequency theory, taking the capacitance current value of an unloaded circuit as an example to be 0.3A, recording the overvoltage level and the overcurrent level of the bus under the conditions of one-time reignition and multiple reignitions,

at the time of the primary reburn, as shown in fig. 23 and 24;

multiple reburning events, as shown in fig. 25 and 26;

the change in the maximum overvoltage amplitude is affected by the number of arc reignitions. When the reignition times are increased, the maximum amplitude of the overvoltage is increased along with the increase of the reignition times of the electric arc, and when the maximum amplitude of the brake-separating overvoltage reaches a certain value within a limited value, as can be seen from the figure, the amplitude of the overvoltage is not increased much when the reignition times are increased.

After the test of example 3, the following statistics were obtained:

1) at an altitude of 2000 m:

the primary reburn event, as shown in the table below,

	maximum overvoltage level (p.u.)	Maximum transient overcurrent level (A)
			0.5A	1.83	70
0.4A	1.62	63
			0.3A	1.55	59
0.2A	1.48	46
			0.1A	1.25	34

In the most severe cases of reignition, as shown in the table below,

	maximum overvoltage level (p.u.)	Maximum transient overcurrent level (A)
			0.5A	2.69	145
0.4A	2.45	140
			0.3A	2.28	135
0.2A	2.19	124
			0.1A	2.10	107

2) At an altitude of 3000 m:

the primary reburn event, as shown in the table below,

in the most severe cases of reignition, as shown in the table below,

	maximum overvoltage level (p.u.)	Maximum transient overcurrent level (A)
			0.5A	2.69	146
0.4A	2.45	141
			0.3A	2.28	135
0.2A	2.20	123
			0.1A	2.11	106

3) At an altitude of 4000 m:

the primary reburn event, as shown in the table below,

	maximum overvoltage level (p.u.)	Maximum transient overcurrent level (A)
			0.5A	1.83	70
0.4A	1.62	63
			0.3A	1.55	59
0.2A	1.48	46
			0.1A	1.25	34

In the most severe cases of reignition, as shown in the table below,

	maximum overvoltage level (p.u.)	Maximum transient overcurrent level (A)
			0.5A	2.69	146
0.4A	2.45	141
			0.3A	2.28	135
0.2A	2.20	123
			0.1A	2.11	106

And (4) conclusion: under the same altitude, the larger the value of capacitance current flowing through the circuit is, the more serious the overvoltage and overcurrent level generated by restriking between contacts is, and the different charge storage capacities of the circuit are.

When the same capacitance current value flows through the circuit, the arc does not shake, the arc column is not broken, repeated reignition occurs on the circuit, and the overvoltage and overcurrent levels are basically unchanged.

The overvoltage level generated by switching the no-load line is between 1.25 and 2.69p.u.

Simulation study example 4 (cut off 35kV distribution network no-load line overvoltage and overcurrent level study)

Referring to 10kV and 35kV distribution network standard design of southern Power grid company in China, in a 35kV line, a steel-cored aluminum stranded wire LGJ240/30 is adopted as an overhead line, the span is set to be 600m, and the length of the line is determined by the capacitance current flowing through the line. The bolt angle steel tower is adopted, the conducting wires are arranged in a triangular mode, the height of the tower top is 18m, the distance between two sides and the ground is 16.8m, the distance between a middle line and the ground is 18.3m, the distance between two side lines is 5.66m, and the distance between two side lines and the middle line is 3.2 m. The soil resistivity was selected to be 2000 Ω · m.

After testing, the following statistics were obtained:

1) at an altitude of 2000 m:

the primary reburn event, as shown in the table below,

	maximum overvoltage level (p.u.)	Maximum transient overcurrent level (A)
			0.5A	1.98	160
0.4A	1.76	147
			0.3A	1.54	134
0.2A	1.54	130
			0.1A	1.48	129

In the most severe case of reignition:

2) under 3000m condition

Under the condition of primary reburning:

	maximum overvoltage level (p.u.)	Maximum transient overcurrent level (A)
			0.5A	1.98	160
0.4A	1.76	147
			0.3A	1.54	134
0.2A	1.54	130
			0.1A	1.48	129

In the most severe case of reignition:

	maximum overvoltage level (p.u.)	Maximum transient overcurrent level (A)
			0.5A	2.70	342
0.4A	2.53	339
			0.3A	2.44	305
0.2A	2.21	283
			0.1A	2.18	278

3) Under 4000m condition

Under the condition of primary reburning:

	maximum overvoltage level (p.u.)	Maximum transient overcurrent level (A)
			0.5A	1.98	160
0.4A	1.76	147
			0.3A	1.54	134
0.2A	1.54	130
			0.1A	1.48	129

In the most severe case of reignition:

simulation study example 5 (arc attenuation characteristics study under 10kV and 0.2m/s conditions)

A mathematical model (shown in figure 27) is established for the 10kV circuit breaker arc extinguishing chamber in the contact opening process based on a flow dynamics N-S equation and an energy continuity equation. The influence of an external circuit and mechanical motion on the electric arc is coupled by starting from the physical process of the electric arc with air as a medium and neglecting the action of a magnetic field and gravity, so that the simulation calculation of the dynamic behavior of the electric arc during arc extinction is realized.

Taking the case of an altitude of 2000m as an example, the distribution of the temperature field with 0.1A current cut-off interval is simulated as shown in fig. 28;

taking the case of an altitude of 2000m as an example, the distribution of the temperature field with 0.2A current cut-off interval is shown in fig. 29;

taking the case of an altitude of 2000m as an example, the distribution of the temperature field with 0.3A current cut-off interval is shown in fig. 30;

taking the case of an altitude of 2000m as an example, the distribution of the temperature field with 0.4A current cut-off interval is shown in fig. 31;

taking the case of an altitude of 2000m as an example, the distribution of the temperature field with 0.5A current cut-off interval is simulated as shown in fig. 32;

as the cutoff current increases, the arc generates heat more severely, and the area of the high-temperature region increases.

(3) Switched capacitor current test research

A capacitor bank, a power frequency test transformer, an isolating switch and a high-speed camera are selected to form a simulated actual circuit, and the no-load capacitive current working condition of a disconnected 10kV-35kV circuit is simulated for testing, wherein the power frequency test transformer is connected with the capacitor bank through a circuit, the isolating switch is arranged on the circuit, and the high-speed camera is aligned to the isolating switch and used in cooperation with a high-speed camera and a recorder, as shown in figure 40.

Three voltage working conditions are created by using a power frequency test transformer, a three-phase asynchronous speed reduction motor drives an isolating switch to be switched on and off, live working is simulated, and the capacitance current values of a no-load circuit are respectively selected to be 0.1A, 0.2A, 0.3A, 0.4A and 0.5A;

under different altitudes and humidity conditions, the combination of the same voltage and different capacitive currents is subjected to a separation and combination test, and the specific test data is as follows:

the opening speed and the opening distance are controlled by adjusting the on-time and the power supply frequency, the speed is determined by adopting a high-speed camera, the overvoltage and overcurrent values are recorded by adopting a wave recorder, the arc-drawing process is recorded by adopting a high-speed camera, the arc length is measured, and typical waveforms are recorded by the wave recorder as shown in fig. 33, 34, 35, 36, 37, 38 and 39;

from the test waveform, in the splitting and combining process, higher overvoltage is generated, the highest overvoltage reaches 6.9 times of rated voltage, obviously exceeds the multiple required by the existing regulation, and is also obviously larger than the conclusion of simulation research. Meanwhile, as can be seen from simulation, in the opening and closing process, when the opening and closing angle is 90 degrees or 270 degrees, the overvoltage and the overcurrent are both large and are larger than those in opening and closing at other angles, and from the test waveform, because the isolating switch has no arc extinguishing function and the load is a purely capacitive load, in the opening process, when the current zero crossing point is extinguished, the voltage is just at the peak value, so that the overvoltage is abnormally large in the opening process.

During the actual operation of live working, because the load is not pure capacitive or pure inductive, but is a load with all of capacitance, inductance and resistance, when a no-load circuit is disconnected, the voltage when the current naturally arcs will not be the peak value, and the overvoltage level will not be similar to the conclusion obtained by the test.

Claims (1)

1. The method for researching the 35kV and the following electrified switching no-load lines in the high-altitude area is characterized by comprising the following steps of:

(1) determining altitude and humidity conditions:

the relevant experiments were carried out under the following five conditions of altitude:

A. selecting a value from a natural environment with an altitude of 1800m-2000m, wherein the humidity is natural humidity;

B. selecting a value in a natural environment with an altitude of 3000m-3500m, wherein the humidity is natural humidity;

C. simulating an altitude value corresponding to a natural environment with an altitude of 1800m-2000m in a simulated climate laboratory, wherein the humidity is 80%;

D. simulating an altitude value corresponding to a natural environment with an altitude of 3000m-3500m in a simulated climate laboratory, wherein the humidity is 80%;

E. simulating a natural environment with an altitude of 4000m in a simulated climate laboratory, wherein the humidity is 80%;

(2) simulation research of switching capacitance and current:

A. determining a simulation model:

establishing a simulation model by using ATP-EMTP simulation software, selecting an LCC power transmission line model (a pure cable line and an overhead line), adopting a common standard tower type of a 10kV-35kV system, adopting a common standard type of a lead, selecting 500-2000 omega-m soil resistivity, selecting an ideal infinite power supply system as the system, and selecting a time control switch as an isolating switch;

B. carrying out simulation research:

a. establishing a switching no-load line model by using ATP-EMTP, and performing electromagnetic transient simulation on a no-load line switching the same voltage within the range of 10kV to 35kV at the same altitude, wherein the capacitance current values of the no-load line are respectively selected to be 0.1A, 0.2A, 0.3A, 0.4A and 0.5A;

when the fixed closing angle is 90 degrees, observing the condition of different opening angles, and determining the influence of the opening angles on overvoltage and overcurrent;

when the fixed opening angle is 270 degrees, namely the residual voltage is-Em, observing the situation of different closing angles, and determining the influence of the closing angles on overvoltage and overcurrent;

b. building a switching no-load line model by using ATP-EMTP, and performing electromagnetic transient simulation on the no-load lines switched with different voltages within the range of 10kV to 35kV under the altitude condition in the step (1), wherein the capacitance current values of the no-load lines are respectively selected to be 0.1A, 0.2A, 0.3A, 0.4A and 0.5A;

setting the distance between contacts of the disconnecting switch to be 240mm, comparing the medium strength recovery voltage with the arc gap recovery voltage, setting to obtain a time region in which the electric arc can be reignited, summarizing the influence of one-time reignition and multiple reignitions of the electric arc on the amplitude of the overvoltage by using a power frequency arc extinguishing theory and a high-frequency theory, and recording the maximum overvoltage level and the maximum transient overcurrent level under the conditions of one-time reignition and the most severe reignition;

c. building a switching no-load line model by using ATP-EMTP, and researching the arc attenuation characteristics under the conditions of switching 10kV and 0.2m/s in the altitude condition in the step (1);

(3) switching capacitance current test research:

A. determining the test equipment:

selecting a capacitor bank, a power frequency test transformer, an isolating switch and a high-speed camera to form a simulated actual circuit, and simulating the no-load capacitive current working condition of a disconnected 10kV-35kV circuit to perform a test, wherein the power frequency test transformer is connected with the capacitor bank through a circuit, the isolating switch is arranged on the circuit, and the high-speed camera is aligned to the isolating switch and is matched with a high-speed camera and a recorder for use;

B. carrying out experimental study:

a. three voltage working conditions are created by using a power frequency test transformer, a three-phase asynchronous speed reduction motor drives an isolating switch to be switched on and off, live working is simulated, and the capacitance current values of a no-load circuit are respectively selected to be 0.1A, 0.2A, 0.3A, 0.4A and 0.5A;

b. performing a separation and combination test on the combination of the same voltage and different capacitive currents under the altitude and humidity conditions in the step (1), controlling the opening speed and the opening distance by adjusting the on-time and the power frequency, determining the speed by adopting a high-speed camera, recording the overvoltage and overcurrent values by adopting a recorder, recording the arc discharge process by adopting a high-speed camera, and measuring the arc length;

(4) the research conclusion is drawn:

and comparing the voltage values in the simulation research and the test research to obtain the voltage difference between the actual operation and the simulation operation, and analyzing the factors causing the difference.

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