CN103293419A - Evaluation method of grounding device impact performance - Google Patents

Abstract

The invention discloses an evaluation method of grounding device impact performance. The method includes the steps of firstly, determining physical parameters of a grounding device in actual operation; secondly, building an equivalent numerical model, and calculating capacitance, inductance and conductivity of an element; thirdly, using a PSCAD/EMTDC simulation platform to evaluate impact features of impact current testing models; fourthly, drawing a device impact grounding resistance variation curve graph under different lightening current amplitude, different soil resistance, different size and different burying depth; fifthly, comparing grounding resistance with the curve graph to judge whether the grounding resistance accords with the curve variation range or not. By the method, grounding device grounding resistance impact features of a 10kV distribution line can be evaluated accurately.

Description

A kind of appraisal procedure of earthing device impact characteristics

Technical field

The present invention relates to a kind of assessment technology of earthing device ground connection impact characteristics, particularly a kind of appraisal procedure of earthing device impact characteristics.

Background technology

In electric system, thunderbolt is the one of the main reasons that causes the electric line flashover.Than higher area, always the trip number of times that caused by thunderbolt in the number of times of high-tension line accounts for the 40%-70% of sum at China's trip-out rate.For prevent the person get shocked, ensure electric system normal operation, prevent from being struck by lightning and the harm of static, need take certain earthed system.Operating experience both domestic and external and theoretical analysis show that effectively reducing pole tower ground resistance is to improve transmission line of electricity direct lightning strike protection effect effective measures the most.

The size of stake resistance not only geometric size and the shape and structure with ground-electrode is relevant, and is also relevant with the resistivity of the structure of the earth, soil, when lightning impulse current flows through and relevant with waveform with the amplitude of the dash current of the ground-electrode of flowing through.But for the shaft tower lightning protection of 10kV power distribution network, because the amplitude of lightning current is big, equivalent frequency height increases the current density that flows through earthing device, and can cause the transient process of a series of complexity owing to the rush of current characteristic.So thunderbolt shaft tower, lightning conducter or thunderbolt circuit are via lightning arrester, lightning current looses by earthing device and flows to the earth potential that forms in the earth, and what work is impulse earthed resistance rather than power frequency earthing resistance.

Because 10kV distribution line grid structure complexity, multi-point and wide-ranging, the integral insulation level is low, the tower grounding device is installed with lightning arrester usually and is set up, so be subjected to corrosion and the unreasonable factor affecting such as bury underground of environment, soil resistivity, the device itself of infield, cause pole tower ground resistance to surpass norm standard.When thunderbolt 10kV distribution line, lightning current will produce higher voltage at earthing device and fall, and cause the secondary failure rate of lightning arrester to raise, and greatly influence the normal operation of 10kV distribution.Improve earthing device and be protection distribution line and grid equipment in the electric system particularly lightning arrester exempt from the guarantee of fault current and lightning current infringement.

The present invention considers that 10kV distribution line lightning surge is by the amplitude of lightning current size behind the lightning arrester, earthing device under different lightning impulse currents has been adopted the electric parameter of setting up pi-network model calculating earthing device element, and set up the equivalent model of PSCAD/EMTDC emulation soil spark effect, by to the level-vertical-type earthing device of 10kV distribution line through the stream lightning current time, impulse resistance is with soil resistivity, the relation of amplitude of lightning current and earthing device depth of burying size variation, draw the impact characteristics of common 10kV distribution line earthing device, for reasonably optimizing the arrangement form of earthing device in the actual engineering, the tripping rate with lightning strike that reduces distribution line provides foundation.

Summary of the invention

The objective of the invention is to overcome the shortcoming of prior art with not enough, the appraisal procedure of a kind of level-vertical-type earthing device resistance characteristic is provided, impact characteristics rule at level in the 10kV distribution line-vertical-type earthing device, for can correctly assess level in the 10kV distribution-vertical-type earthing device in DIFFERENT METEOROLOGICAL CONDITIONS, geographical conditions, the otherness of structure size and mounting process is to the influence of earthing device impact characteristics, this method is carried out computational analysis by the mathematical model that makes up 10kV distribution line level-vertical-type earthing device, and this method is in conjunction with lightning current, soil resistivity changes, the earthing device impact characteristics difference of the depth of burying and proposing.The impact characteristics rule assessment of level in the 10kV distribution line-vertical-type earthing device is applicable to transformation construction and the 10kV distribution line lightning protection risk assessment of 10kV distribution line earthing device.

Purpose of the present invention is achieved through the following technical solutions, and a kind of appraisal procedure of earthing device impact characteristics may further comprise the steps:

1, at a kind of in the 10kV distribution line existing level-vertical earthing device, measure the level body (as accompanying drawing 1 level body 3) that adopts zinc-coated flat steel sheet, and each section length that adopts the vertical body (as accompanying drawing 1 vertical body 4) of Zinc-coated angle steel; And measure level body apart from the depth of burying on ground, and the soil resistivity of location;

2, calculate the numerical parameter of earthing device level body and vertical body, the equivalent-circuit model shown in 2 is built the Equivalent Calculation Model of earthing device with reference to the accompanying drawings;

(1) inductance L of calculated level body and each section length of vertical body ₀, the inductance of each section grounding body unit length, its formula is as follows:

$L_0=\frac{\mathrm{\μ}}{2\mathrm{\π}}(1n\frac{2l}{r_{\mathrm{ef}}}-1),---\left(1\right)$

In the formula: μ ₀Be the magnetic capacity of vacuum, desirable μ in usage range ₀=4 π * 10 ^-7, r _EfBe the grounding body radius, l is every section grounding body length;

(2) the inductance C of calculated level body and each section length of vertical body ₀, each section grounding body unit length is to the electric capacity of infinite distance zero-potential surface, and its formula is as follows:

C ₀=ερG ₀ （2）

In the formula, ε is the specific inductive capacity of soil, desirable ε=9 * 8.86 * 10 in usage range ^-12F/m;

(3) electricity of each section length of calculated level body is led G ₀, and the electricity of each section length of vertical body is led G ₁, its formula is as follows:

$G_0=\frac{2\mathrm{\&pi;}}{\mathrm{\&rho;}(1\mathrm{<figure-callout\; id="2"\; label="n\; l"\; filenames="HDA00003279511800022.png"\; state="\{\{state\}\}">n</figure-callout>}\frac{l^{}}{}\frac{{}^2}{2{\mathrm{hr}}_{\mathrm{ef}}}-0.61)}---\left(3\right)$

$G_1=\frac{2\mathrm{\&pi;}}{\mathrm{\&rho;}(1n\frac{2l}{r_{\mathrm{ef}}}-0.31)}---\left(4\right)$

In the formula, ρ is soil resistivity, and h is the grounding body buried depth, r _EfBe equivalent radius.

3, the impact characteristics that utilizes the PSCAD/EMTDC emulation platform to carry out the dash current test model comprises:

(1) the device impulse earthed resistance change curve under the different amplitude of lightning current 30kA of drafting, 50kA, the 70kA;

(2) the device impulse earthed resistance change curve under drafting different soils resistivity 50 Ω/m, 100 Ω/m, 150 Ω/m;

(3) draw different earthing device sizes and comprise that numbers of branches is the device impulse earthed resistance change curve under 2 to 8;

(4) the device impulse earthed resistance change curve under the different depth of burying 0.6m to 1.2m of drafting;

4, measure the stake resistance of earthing device actual motion in the 10kV distribution line; To measure to such an extent that stake resistance is depicted as change curve and accompanying drawing 3, accompanying drawing 4, accompanying drawing 5, accompanying drawing 6 contrasts, whether in meeting the curvilinear motion scope and whether meet the continuous Changing Pattern of curve.

Principle of work of the present invention: the present invention is at first according to the level-vertical-type earthing device practical structures feature of 10kV distribution line, measure the level body that adopts zinc-coated flat steel sheet, and each section length of vertical body that adopts Zinc-coated angle steel, apart from the depth of burying on ground and the soil resistivity of location, adopt distributed parameter model to calculate the equivalence element numerical value of actual model, calculate the level body of earthing device and inductance, electric capacity and the electricity of each section length of vertical body and lead.Set up the pi-network realistic model at the PSCAD/EMTDC emulation platform then, utilize the PSCAD/EMTDC emulation platform to carry out the impact characteristics of dash current test model, and draw the device impulse earthed resistance change curve of different amplitude of lightning current, different soils resistivity, the different depth of buryings; Measure the actual operating data and plot contrast of earthing device at last, whether in meeting the curvilinear motion scope and whether meet the continuous Changing Pattern of curve, for transformation and the construction of 10kV distribution line are considering to select only earthing device shape and the depth of burying under economy and the applicability.

The present invention has following advantage and effect with respect to prior art:

1, the Equivalent Calculation Model of 10kV distribution line earthing device of the present invention is simple, can the fine ruuning situation of earthing device under the lightning current effect that simulates.

2, the present invention can draw 10kV distribution line level-vertical-type earthing device at the impact characteristics Changing Pattern of different lightning impulse currents.

3, the present invention can draw the impact characteristics Changing Pattern of 10kV distribution line level-vertical-type earthing device under the condition of resembling of differently regulating the flow of vital energy of different lightning impulse currents, different soils resistivity.

4, the present invention can draw 10kV distribution line level-vertical-type earthing device at the different size of the different depth of buryings, different numbers of branches and the impact characteristics Changing Pattern under the mounting process condition.

5, the impact characteristics rule under the employing different condition of the present invention can be for reasonably optimizing the arrangement form of earthing device in the actual lightning protection improvement project, and the tripping rate with lightning strike that reduces distribution line provides foundation.

Description of drawings

Fig. 1 is the level-vertical-type earthing device synoptic diagram of 10kV distribution line.

Fig. 2 is the impulse resistance curvilinear motion figure under the different soils resistivity.

Fig. 3 is the impulse resistance curvilinear motion figure under the different amplitude of lightning current.

Fig. 4 is the impulse resistance curvilinear motion figure under the different numbers of branches.

Fig. 5 is the impulse resistance curvilinear motion figure under the different depth of buryings.

Fig. 6 is earthing device component models equivalent circuit diagram.

Embodiment

The present invention is described in further detail below in conjunction with embodiment and accompanying drawing, but embodiments of the present invention are not limited thereto.

Embodiment

At be a kind of in the 10kV distribution line earthing device of existing level-vertical-type structure, dash current 1 as shown in Figure 1, ground 2, level body 3, vertical body 4, according to actual conditions measure construction or transform in the length of a grounding body segmentation, the depth of burying and soil resistivity are determined the realistic model structure of earthing device.

2. the earthing device conductor uses distributed parameter model to carry out the numerical operation processing, with the unit length conductor resistance R of this branch ₀, self-induction L ₀, scatter admittance G over the ground ₀, ground capacitance C ₀Be described (parameter as shown in Figure 2).

3. build equivalent numerical, the electric capacity of computing element, inductance and electricity are led.L ₀, C ₀Be respectively the inductance that diminishes the lead per unit length, to the electric capacity of infinite distance zero-potential surface, G ₀, G ₁Lead for the electricity of level, vertical junction terrain, its formula is as follows:

$L_0=\frac{\mathrm{\&mu;}}{2\mathrm{\&pi;}}(1n\frac{2l}{r_{\mathrm{ef}}}-1),---\left(1\right)$

In the formula: μ ₀Be the magnetic capacity of vacuum, desirable μ in usage range ₀=4 π * 10 ^-7, r _EfBe the grounding body radius, l is every section grounding body length.

$G_0=\frac{2\mathrm{\&pi;}}{\mathrm{\&rho;}(1\mathrm{<figure-callout\; id="2"\; label="n\; l"\; filenames="HDA00003279511800022.png"\; state="\{\{state\}\}">n</figure-callout>}\frac{l^{}}{}\frac{{}^2}{2{\mathrm{hr}}_{\mathrm{ef}}}-0.61)},---\left(2\right)$

$G_1=\frac{2\mathrm{\&pi;}}{\mathrm{\&rho;}(1n\frac{2l}{r_{\mathrm{ef}}}-0.31)},---\left(3\right)$

In the formula, ρ is soil resistivity, and h is the grounding body buried depth, r _EfBe equivalent radius.

Each section grounding body unit length to the electric capacity of infinite distance zero-potential surface is:

C ₀=ερG ₀ ， （4）

In the formula, ε is the specific inductive capacity of soil, desirable ε=9 * 8.86 * 10 in usage range ^-12F/m.

Because the electric field intensity of spark zone boundary is the critical breakdown field strength of soil, but then each section conductor is considered equivalent radius through type after the spark discharge:

$J=\frac{E_C}{\mathrm{\&rho;}}=\frac{\mathrm{\&Delta;<figure-callout\; id="2"\; label="I"\; filenames="HDA00003279511800022.png"\; state="\{\{state\}\}">I</figure-callout>}}{2\mathrm{\&pi;\&Delta;l}},---\left(5\right)$

$r_{\mathrm{ef}}=\frac{\mathrm{\&rho;\&Delta;<figure-callout\; id="2"\; label="l"\; filenames="HDA00003279511800022.png"\; state="\{\{state\}\}">l</figure-callout>}}{2\mathrm{\&pi;\&Delta;}{\mathrm{IE}}_C},---\left(6\right)$

J is that △ I is the electric current that scatters to the earth by conductor by the wandering current density of conductor in the formula, and △ l is the length of every section conductor, and ρ is soil resistivity, E _cBe the critical breakdown field strength of soil.

4. set up the PSCAD/EMTDC model according to above-mentioned condition and carry out simulation calculation, adopt pi-network analogue ground device, simulate the lightning current waveform with ideal current source.The lightning current waveform adopts 2.6/50 μ s, and with two exponential expression is:

I=AI _m[exp（-αt）-exp（-βt）]， （7）

5. on the PSCAD/EMTDC model, utilize different electric capacity, inductance and the electricity of formula (5) (6) computing element to lead by changing soil resistivity, stake resistance change curve when being plotted in soil resistivity and being 50 Ω/m, 100 Ω/m, 150 Ω/m, as shown in Figure 3.

6. the lightning current generation module on the PSCAD/EMTDC model changes the amplitude of lightning current size, stake resistance change curve when being plotted in amplitude of lightning current and being 30kA, 50kA, 70kA, as shown in Figure 4.

7. on the PSCAD/EMTDC model, utilize electric capacity, inductance and the electricity of formula (1) (2) (3) (4) increase or minimizing element to lead by changing numbers of branches, be plotted in the stake resistance change curve under the different size, as shown in Figure 5.

8. on the PSCAD/EMTDC model, utilize the electricity of formula (2) (3) computing element to lead by changing the depth of burying, be plotted in the stake resistance change curve under the different depth of buryings, as shown in Figure 6.

9. measure the stake resistance of actual motion in the 10kV distribution line of earthing device and accompanying drawing 3, accompanying drawing 4, accompanying drawing 5, accompanying drawing 6 contrasts, whether in meeting the curvilinear motion scope and whether meet the continuous Changing Pattern of curve.

Above-described embodiment is preferred implementation of the present invention; but embodiments of the present invention are not restricted to the described embodiments; other any do not deviate from change, the modification done under spiritual essence of the present invention and the principle, substitutes, combination, simplify; all should be the substitute mode of equivalence, be included within protection scope of the present invention.

Claims (6)

1. the appraisal procedure of an earthing device impact characteristics is characterized in that, may further comprise the steps:

Step 1: at a kind of in the 10kV distribution line level-vertical earthing device, comprise level body and the vertical body of several segmentations, described level body and vertical body are orthogonal, measure the length of each segmentation of level body and vertical body;

Step 2: measuring process 1 described level body is apart from the depth of burying on ground, and the soil resistivity of described earthing device location;

Step 3: adopt equivalent-circuit model to build the level body of earthing device and the Equivalent Calculation Model of vertical body, set up the PSCAD/EMTDC model and carry out simulation calculation;

Step 4: the impulse resistance change curve of drawing earthing device;

Step 5: the data of measuring the earthing device actual motion are assessed.

2. appraisal procedure according to claim 1 is characterized in that, in the described step 3, calculates the inductance of each segmentation grounding body unit length of described equivalent-circuit model, and its computing formula is as follows:

$L_0=\frac{\mathrm{\&mu;}}{2\mathrm{\&pi;}}(1n\frac{2l}{r_{\mathrm{ef}}}-1),$

In the formula, μ ₀For the magnetic capacity of vacuum, get μ ₀=4 π * 10 ^-7, r _EfBe the grounding body radius, l is every section grounding body length.

3. appraisal procedure according to claim 1 is characterized in that, in the described step 3, calculates the length electricity of each segmentation of the level body in the described equivalent-circuit model and leads G ₀, calculate each section length electricity of the vertical body in the described equivalent-circuit model and lead G ₁, its computing formula is as follows:

$G_0=\frac{2\mathrm{\&pi;}}{\mathrm{\&rho;}(1n\frac{l^2}{2{\mathrm{hr}}_{\mathrm{ef}}}-0.61)},$

$G_1=\frac{2\mathrm{\&pi;}}{\mathrm{\&rho;}(1n\frac{2l}{r_{\mathrm{ef}}}-0.31)},$

In the formula, ρ is soil resistivity, and h is the grounding body buried depth, r _EfBe equivalent radius.

4. appraisal procedure according to claim 1 is characterized in that, wherein each section grounding body unit length is to the electric capacity of infinite distance zero-potential surface for equivalent-circuit model in the described step 3, and its formula is as follows:

C ₀=ερG ₀，

In the formula, ε is the specific inductive capacity of soil, gets ε=9 * 8.86 * 10 ^-12F/m.

5. appraisal procedure according to claim 1 is characterized in that, described step 4 may further comprise the steps:

Earthing device impulse resistance change curve under A, the different amplitude of lightning current 30kA of drafting, 50kA, the 70kA;

Earthing device impulse resistance change curve under B, drafting different soils resistivity 50 Ω/m, 100 Ω/m, 150 Ω/m;

C, the different earthing device sizes of drafting comprise that numbers of branches is 2 to 8 earthing device impulse resistance change curve;

Earthing device impulse resistance change curve under D, the different depth of burying 0.6m to 1.2m of drafting.

6. appraisal procedure according to claim 1 is characterized in that, described step 5 may further comprise the steps:

(1) measures earthing device stake resistance under the different ruuning situations in the 10kV distribution line, and draw change curve;

(2) will measure the earthing device impulse resistance change curve contrast of calculating of stake resistance change curve and emulation platform, whether in meeting the earthing device impulse resistance curve map variation range that emulation platform calculates;

(3) whether to the earthing device in scope is judged to be qualifiedly, the earthing device in scope is not then judged defective, needs further transform the depth of burying and the size of earthing device again.

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