CN103346514A - Method for determining minimum insulation distance among flexible busbars of 500kV transformer substation in high altitude region - Google Patents

Abstract

The invention relates to a method for determining the minimum insulation distance between soft buses of a 500kV substation in a high-altitude area, including: (1) calculating the correction factor m of the altitude correction factor; (2) using the operating impact discharge correction formula to obtain the altitude correction factor K _am (3) Multiply the above-mentioned altitude correction factor K _am by the interphase operation overvoltage requirement value of the 500kV substation soft busbar, and obtain the minimum insulation distance d required between the 500kV substation soft busbars at a high altitude and the operating discharge voltage U when the altitude is 0m , and then according to the air gap discharge voltage curve at an altitude of 0m, the gap d ₀ corresponding to the operating discharge voltage U at an altitude of 0m is obtained, and the gap d ₀ is the minimum insulation distance d required between soft buses of a 500kV substation at a high altitude. The result obtained by the method of the invention is superior to the altitude correction method of IEC60071 and GB311.1.

Description

Determination method of minimum insulation distance between flexible buses of 500kV substation in high altitude area

technical field

The invention relates to a method for determining the minimum insulation distance between flexible buses of a 500kV substation in a high-altitude area, and belongs to the field of external insulation of power substations.

Background technique

my country's energy distribution is uneven, and the high-altitude areas in the west are rich in water and thermal power resources. With the deepening of the country's western development, the demand for west-to-east power transmission is becoming stronger and stronger. Ultra/UHV, long-distance, and large-capacity transmission corridors The substation and substation must pass through the high altitude area in the west, and the air in the high altitude area is thin, and the air insulation strength of the same gap will decrease to varying degrees with the increase of altitude.

When the transmission line and equipment are in normal operation or faulty operation, the system operating state changes suddenly, and the mutual conversion of electromagnetic energy in the system causes an oscillating transition process, causing high operating overvoltage on some electrical equipment or local power grids. With the rapid development of the power grid and the increase of the voltage level, the amplitude of the operating overvoltage also increases, and the external insulation selection of the power transmission and transformation equipment plays a decisive role in the operating overvoltage in the ultra-high voltage grid. One of the main factors of the insulation level of power transmission and transformation equipment, how to reasonably select the insulation distance between the soft busbars of the substation in the selection of external insulation of power transmission and transformation equipment is one of the key problems faced by the construction of 500kV substation projects in high altitude areas, which has great economic significance. significance and environmental benefits.

At present, domestic and foreign studies on the discharge characteristics of the external insulation of electrical equipment in high-altitude areas have proposed many altitude and atmospheric correction methods, some of which can obtain the altitude correction factor by substituting the corresponding altitude or typical meteorological conditions. Although simple and practical, but relatively rough. Some are substituted into the meteorological conditions of the location of the project. This method is relatively accurate, but it is difficult to obtain meteorological data. At present, there are mainly calculation methods recommended by standards such as GB311.1-1997, IEC60071-2:1996, GB/T16927.1-1997, and DL/T620-1997 for altitude and atmospheric correction. GB/T16927.1-1997 does not distinguish the obvious difference of the altitude correction coefficient under different voltages (operating shock and lightning shock), which is relatively rough and not suitable for correction of interphase operation; DL/T620-1997 needs the actual atmosphere of the test site Conditions, at the same time, the impact of phase-to-ground and phase-to-phase operation is uniformly treated, which is not suitable for correction of phase-to-phase operation. The correction method of GB311.1-1997 only considers the influence of altitude on the dielectric strength, and takes the dielectric strength at an altitude of 1000m as the starting point for correction, and does not perform altitude correction for areas at and below 1000m, which is slightly rough. The altitude correction method recommended by IEC60071-2:1996 is related to the type of test electrode, and is mainly suitable for altitudes below 2000m.

Contents of the invention

The purpose of the present invention is to overcome above-mentioned deficiencies in the prior art and provide a kind of method for determining the minimum insulation distance between the soft buses of 500kV substations in high altitude areas, the method corrects the operation overvoltage requirement value of the lines in high altitude areas to the soft buses of substations to The altitude is 0m, and then using the relationship curve between the air gap and the discharge voltage required at the altitude of 0m, the air gap distance between the soft busbars of the substation is determined, which is the minimum insulation distance required for the operation of the soft busbars of the 500kV substation in the high altitude area.

The technical solution adopted to realize the purpose of the present invention is: a method for determining the minimum insulation distance between flexible buses of 500kV substations in high altitude areas, including:

(1) Perform linear fitting according to the phase-to-phase operation overvoltage value of the 500kV substation soft bus at different altitudes, and obtain the correction factor m of the altitude correction factor:

m=-0.0003U+1.2384 In the formula, U is the operating overvoltage, unit: MV;

(2) Using the operating impulse discharge correction formula, the altitude correction factor K _am is obtained:

式中，H为海拔高度，23m≤H≤3742m；

In the formula, H is the altitude above sea level, 23m≤H≤3742m;

(3) Multiply the altitude correction factor K _am by the required value of the phase-to-phase operating overvoltage of the soft busbars of the 500kV substation to obtain the operating overvoltage U when the minimum insulation distance d between the soft buses of the 500kV substation at high altitude is at an altitude of 0m, Then according to the air gap discharge voltage curve at an altitude of 0m, the gap d ₀ corresponding to the operating overvoltage U at an altitude of 0 m is obtained, and the gap d ₀ is the minimum insulation distance d required between soft buses of a 500kV substation at a high altitude.

In the above technical solution, the required overvoltage value of the phase-to-phase operation of the 500kV substation soft busbar is between 1.500MV and 2.600MV.

The method of the present invention converts the required minimum insulation distance between soft buses of 500kV substations in the high altitude area into the operating discharge voltage at the altitude of 0m by establishing the relationship between the high altitude area and the altitude 0m, and then according to the altitude 0m air gap discharge voltage curve , to obtain the gap d corresponding to the operating discharge voltage at an altitude of 0m, and the gap d is the minimum insulation distance between soft buses of a 500kV substation at a certain altitude.

Description of drawings

Fig. 1 is a flow chart of the method for determining the minimum insulation distance between soft buses of 500kV substations in high altitude areas according to the present invention.

Detailed ways

The present invention will be further described in detail below in conjunction with the accompanying drawings and specific embodiments.

The method for determining the minimum insulation distance between soft buses of 500kV substations in high-altitude areas of the present invention establishes a mathematical model, proposes the parameters of the mathematical model, and then compares and analyzes the test results according to the verification test to determine the parameters in the mathematical model, and then proposes the method of the present invention. The present invention is based on the external insulation electrical test in different altitude areas, and compares and analyzes the difference between the test results of the typical electrode of the 500kV substation—the soft busbar at different test points, and proposes a high-altitude correction suitable for the interphase operation impulse voltage of the soft busbar of the 500kV substation formula. As shown in Figure 1, the concrete steps of the inventive method are:

Step S100, obtain the altitude correction factor K _am according to the following formula (1):

${\mathrm{<span\; class="notranslate">\; K</span>}}_{\mathrm{<span\; class="notranslate">\; am</span>}}<span\; class="notranslate">\; =</span>\frac{\mathrm{<span\; class="notranslate">\; 1</span>}}{\mathrm{<span\; class="notranslate">\; 1.0</span>}<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; m</span>}<span\; class="notranslate">\; \&times;</span>\mathrm{<span\; class="notranslate">\; h</span>}<span\; class="notranslate">\; \&times;</span>{\mathrm{<span\; class="notranslate">\; 10</span>}}^{<span\; class="notranslate">\; -</span>\mathrm{<span\; class="notranslate">\; 4</span>}}}<span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; -</span><span\; class="notranslate">\; (</span>\mathrm{<span\; class="notranslate">\; 1</span>}<span\; class="notranslate">\; )</span>$

In the formula, m is the correction factor of the altitude correction factor; H is the altitude above sea level, 23m≤H≤3742m.

Step S200, through experiments at test points at different altitudes, determine the value of the correction factor m of the altitude correction factor in the above formula (1), specifically through the following formula (2):

m=-0.0003U+1.2384 (2)

In the formula, U is the operating overvoltage, unit: MV.

Step S300: Multiply the obtained altitude correction factor K _am by the required value of the phase-to-phase operating overvoltage of the 500kV substation soft busbars to obtain the operating overvoltage U required for the minimum insulation distance d between the soft busbars of the 500kV substation at high altitudes at an altitude of 0m , and then according to the air gap discharge voltage curve at an altitude of 0m, the gap d ₀ corresponding to the operating overvoltage U at an altitude of 0m is obtained, and the gap d ₀ is the minimum insulation distance d required between soft buses of a 500kV substation at a high altitude.

Among them, the required overvoltage value of the phase-to-phase operation of the soft bus in the 500kV substation is between 1.5MV and 2.6MV.

As the altitude increases, the air density gradually decreases, and the insulation strength of the air in the interphase gap will decrease to varying degrees. Therefore, the air gap between the soft busbars of the substation in the high altitude area cannot directly adopt the design specifications of the low altitude area. Appropriately increased by altitude correction. The method of the invention provides the calculation formula of the correction factor for the impact altitude of the soft bus of the 500kV substation between phases. The following is illustrated by specific examples.

Taking the minimum design gap d required for the operating overvoltage of a 500kV substation at an altitude of 3000m as an example, set the required value of the phase-to-phase operating overvoltage to 2354kV, and use formula (2) to correct it. The correction factor of the correction factor m=-0.0003U+1.2384, put 2354kV into the above formula to calculate the correction factor of the altitude correction factor m=0.629, put the altitude 3000m into the correction formula (1), and get the altitude correction factor K _am = 1.591, and then it is obtained that the minimum design gap d required for the operating overvoltage of a 500kV substation at an altitude of 3000m is 3745kV at an altitude of 0m (the operating discharge voltage U is equal to the required value of the overvoltage value multiplied by the correction factor K _am ), and then according to From the air gap discharge voltage curve at an altitude of 0m, the value of the gap d corresponding to the 3745kV operating discharge voltage is obtained. The gap d is the minimum design insulation distance required by the soft busbar phase-to-phase operating overvoltage at an altitude of 3000m.

Insulation discharge characteristic tests other than this example were carried out at three test points in Wuhan (23m above sea level), Xining (2254m above sea level) and Guoluo (3742m above sea level). The details are as follows:

The parameter value of the correction factor m of the altitude correction factor is determined by taking three test points of different altitudes in Wuhan, Xining and Guoluo. The same layout is adopted in Wuhan, Xining, and Guoluo: the simulated soft busbar of the 500kV substation is made of steel pipes with the same diameter, the pipe diameter is 60mm, and the splitting distance is 400mm. In the test, in order to prevent abnormal discharge at the end of the wire, the end of the soft busbar is processed into an arc shape, and a uniform shielding ring with a diameter of 500mm is added. The distances between the two soft buses are 5m, 6m, 7m and 8m respectively, and the height of the soft buses to the ground is 12m. The impulse voltage of the interphase insulation test depends not only on the sum of positive and negative voltages, but also on the proportion of positive and negative voltages. Use the voltage distribution coefficient α=U ^- /(U ⁺ +U ^- ) to represent the distribution ratio of positive and negative voltage components. The overvoltage simulation results of the 500kV system show that when the maximum operating overvoltage between phases occurs, the voltage distribution coefficient α is approximately equal to 0.4, Therefore, the test mainly uses α=0.4 for experimental research.

The Wuhan test site uses two impulse voltage generators with voltages of 5400kV and 3600kV to jointly conduct phase-to-phase tests. Both the test sites in Qinghai use 3600kV and 4200kV mobile impulse voltage generators. The test voltage of the three places adopts the standard operating wave of 250/2500μs, the accuracy of the measurement system of the corresponding equipment meets the test requirements, and the total uncertainty of the measured voltage peak value is less than 3%. The impulse voltage control system adopts the impulse voltage automatic control system of optical fiber isolation and computer control technology, which can realize all digitization of charging, triggering, data acquisition, etc., and has the characteristics of stable performance, high reliability, strong anti-interference ability and good data repeatability. Use the same sample, mainly soft busbars. During the test, the layout is simulated by simulating the actual substation operating conditions.

In this embodiment, the method of the present invention is used to correct the interphase operation shock of the soft bus of a 500kV substation in a high-altitude area. At the same time, the correction result U of the present invention is compared with the correction result of the correction formula of GB311.1 and IEC60071.

The correction result of the present invention refers to the voltage value obtained after correcting the operating impulse discharge voltage values at different altitudes to 0m above sea level by using the correction formula, which is represented by U ₀ here.

In the altitude correction of the soft bus interphase operation impact test at the three test points of Wuhan, Xining and Guoluo, from the altitude correction calculation results, the test results of the three places are corrected to the correction result of the altitude 0m according to the altitude correction factor calculated by the present invention U _0w , U _0x and U _0g , the average absolute deviation of the calibration results is 3.86%, and the maximum deviation is less than 5.7%; the absolute average deviation of the calibration results using IEC60071 is 7.3%, and the maximum deviation is less than 10.5%; GB311.1 The average deviation of the absolute value of the correction result is 20.4%, and the maximum deviation is less than 24.8%. Therefore, the present invention is significantly better than the altitude correction method of IEC60071 and GB311.1 in the correction of the operation shock test result under the test altitude condition.

Claims (2)

1. the minimum insulation distance is determined method between the soft bus of high altitude localities 500kV transformer station, it is characterized in that, comprising:

(1) carry out linear fit according to the Different Altitude point 500kV transformer station alternate switching overvoltage value of soft bus, obtain the modifying factor m of height above sea level correction factor:

m=-0.0003U+1.2384

In the formula, U is switching overvoltage, the MV of unit;

(2) adopt switching impulse discharge correction formula, obtain height above sea level correction factor K _Am:

$K_{\mathrm{am}}=\frac{1}{1.0-m\&times;H\&times;{10}^{-4}}$

In the formula, H is height above sea level, 23m≤H≤3742m;

(3) with described height above sea level correction factor K _AmMultiply by the alternate switching overvoltage required value of the soft bus of 500kV transformer station, obtain required minimum insulation between the soft bus of high height above sea level place 500kV transformer station apart from the operated discharge voltage U of d when the height above sea level 0m, then according to height above sea level 0m air gap discharge voltage profile, the gap d of the operated discharge voltage U correspondence when obtaining described height above sea level 0m ₀, this gap d ₀Be between the soft bus of high height above sea level place 500kV transformer station required minimum insulation apart from d.

2. determine method according to minimum insulation distance between the soft bus of claim 1 described high altitude localities 500kV transformer station, it is characterized in that: the alternate switching overvoltage U required value of the soft bus of described 500kV transformer station is between 1.5MV～2.6MV.