CN102662120A - Low-voltage distribution line lightning trip risk evaluation method and device - Google Patents

Abstract

The invention discloses a low-voltage distribution line lightning trip risk evaluation method which comprises the following steps of: acquiring relevant parameters; substituting the acquired parameters into a specific formula, and respectively calculating a direct lightning flash trip rate and a lightning induction trip rate of the line; and finally, summing to obtain the total lightning trip rate, wherein the total lightning trip frequency serves as an evaluation criteria for measuring the lightning trip risk, and a reliable basis is provided for formulating and evaluating lightning protection measures of the low-voltage distribution line. The data required to be acquired in the evaluation method is easily acquired, the whole process does not refer to complex operation, and the obtained trip rate accurately reflects the trip risk. The invention also discloses a low-voltage distribution line lightning trip risk evaluation device which corresponds to the low-voltage distribution line lightning trip risk evaluation method. The evaluation method and the evaluation device are combined, so that a risk evaluation aim can be fulfilled.

Description

Low-voltage distributing line lightning stroke trip methods of risk assessment and device

Technical field

The present invention relates to distribution line shocking preventing technology field, particularly relate to a kind of low-voltage distributing line lightning stroke trip methods of risk assessment and device.

Background technology

The distribution line of low-voltage distributing line, particularly 10kV be electric system send out, become, fail, join, with the important component part of distribution system in the five big subsystems.It is bearing the important task to the load distribution electric energy, and its safe and stable operation is most important.But because the dielectric level of distribution line is low, grid structure is complicated, makes it not possess the ability of protection direct lightning strike.In addition, thunder and lightning also can reach more than the 500kV at the lightning induced voltage that produces on the lead, has also substantially exceeded the dielectric level of 10kV distribution line.According to statistics, in the electrical network of 6～35kV electric pressure, tripping rate with lightning strike is high, and often has equipment such as on-pole switch, disconnecting link, lightning arrester, transformer, sleeve pipe when lightening activity, to damage.

At present, each item lightning protection measures that the 10kV distribution line is formulated does not reach good lightning protection effect, and the stable operation of the improper yet serious harm of the operation maintenance of thunder resisting equipment electrical network.Therefore, set up low-voltage distributing line, particularly the lightning protection properties evaluation system of 10kV distribution line is to formulate scientific and rational lightning protection strategy, and distribute rationally and the operation maintenance scheme of formation each item lightning protection measures is the important means of reduction distribution damage to crops caused by thunder fault.

Summary of the invention

Based on above-mentioned situation, the present invention proposes a kind of low-voltage distributing line lightning stroke trip methods of risk assessment and device, with the be struck by lightning risk of back tripping operation of assessment low-voltage distributing line, for the formulation of low-voltage distributing line lightning protection strategy provides important evidence.

A kind of low-voltage distributing line tripping operation methods of risk assessment comprises step:

Gather the relevant data of low-voltage distributing line: ground dodges density N _g, probability of sustained arc η, amplitude of lightning current I, circuit average height h, insulator chain impulse flashover voltage U _50%

Adopt the direct lightning strike trip-out rate SFR of computes low-voltage distributing line respectively ₁With induction thunder trip-out rate SFR ₂:

${\mathrm{SFR}}_1=\frac{{2N}_g}{10}\mathrm{\η}{\∫}_{I_e}^{\∞}{D}_{c}p\left(I\right)\mathrm{dI}$

${\mathrm{SFR}}_2=\frac{{2N}_g}{10}\mathrm{\η}{\∫}_{I_1}^{\∞}(S_0-D_c)p\left(I\right)\mathrm{dI}$

In the following formula, D _cExpression circuit direct lightning strike draws thunder width, I _eExpression circuit direct lightning strike lightning withstand level, I ₁Produce the amplitude of lightning current critical value of lightning induced voltage on the expression circuit, S ₀When induction lightning network takes place on the expression circuit, the critical flashover distance of lightning strike spot, p (I) expression amplitude of lightning current probability density function;

Direct lightning strike trip-out rate SFR to low-voltage distributing line ₁With induction thunder trip-out rate SFR ₂Summation obtains the low-voltage distributing line tripping rate with lightning strike.

A kind of low-voltage distributing line induction thunder risk assessment device comprises:

Data acquisition module is used to gather the relevant data of low-voltage distributing line: ground dodges density N _g, probability of sustained arc η, amplitude of lightning current I, circuit average height h, insulator chain impulse flashover voltage U _50%

Direct lightning strike and induction thunder trip-out rate determination module are used for adopting respectively the direct lightning strike trip-out rate SFR of computes low-voltage distributing line ₁With induction thunder trip-out rate SFR ₂:

${\mathrm{SFR}}_1=\frac{{2N}_g}{10}\mathrm{\η}{\∫}_{I_e}^{\∞}{D}_{c}p\left(I\right)\mathrm{dI}$

${\mathrm{SFR}}_2=\frac{{2N}_g}{10}\mathrm{\η}{\∫}_{I_1}^{\∞}(S_0-D_c)p\left(I\right)\mathrm{dI}$

In the following formula, D _cExpression circuit direct lightning strike draws thunder width, I _eExpression circuit direct lightning strike lightning withstand level, I ₁Produce the amplitude of lightning current critical value of lightning induced voltage on the expression circuit, S ₀When induction lightning network takes place on the expression circuit, the critical flashover distance of lightning strike spot, p (I) expression amplitude of lightning current probability density function;

Total trip-out rate determination module is used for the direct lightning strike trip-out rate SFR to low-voltage distributing line ₁With induction thunder trip-out rate SFR ₂Summation obtains the low-voltage distributing line tripping rate with lightning strike.

Low-voltage distributing line lightning stroke trip methods of risk assessment of the present invention; Gather correlation parameter earlier; With the specific formula of gathering of parameter substitution, computational scheme direct lightning strike trip-out rate and induction thunder trip-out rate are sued for peace at last and are obtained total tripping rate with lightning strike respectively again; With total lightning stroke trip frequency as the evaluation criteria of weighing the lightning stroke trip risk, for the formulation of low-voltage distributing line lightning protection measures and comparation and assessment etc. provide reliable foundation.The data of the required collection of this appraisal procedure are easy to obtain, and whole process does not relate to complex calculations, and the gained trip-out rate has reflected the tripping operation risk exactly.Low-voltage distributing line lightning stroke trip risk assessment device of the present invention is the device corresponding with above-mentioned appraisal procedure, and appraisal procedure is used in combination with apparatus for evaluating, can realize the purpose of risk assessment.

Description of drawings

Fig. 1 is the electric geometric model schematic diagram of 10kV distribution line;

Fig. 2 is a low-voltage distributing line lightning stroke trip methods of risk assessment schematic flow sheet of the present invention;

Fig. 3 is a low-voltage distributing line lightning stroke trip risk assessment apparatus structure synoptic diagram of the present invention.

Embodiment

Based on the difference of lightning strike spot position, thunderbolt can be divided into direct lightning strike and induction thunder, and these two kinds of thunders all possibly cause low-voltage distributing line tripping operation fault.The present invention takes all factors into consideration the influence of direct lightning strike and induction thunder, with direct lightning strike trip-out rate and the standard of induction thunder trip-out rate sum as assessment low-voltage distributing line tripping operation risk.Be example with the 10kV distribution line below, in conjunction with accompanying drawing and the present invention of embodiment illustrated in detail.

Judge the flashover that whether insulate during China line thunder protection calculates, be superpotential and insulator chain or the clearance U that occurs with insulator chain two ends relatively always _50%Sparking voltage method (definition method) is as criterion, and superpotential surpasses the U of insulation _50%Sparking voltage promptly is judged to flashover ^[18]Getting 10kV distribution line wave impedance is 335 Ω, and according to the inferior rule of Peter, circuit direct lightning strike lightning withstand level does

$I_e=\frac{U_{50\%}}{144.15}---\left(1\right)$

Except that the minority the Northwest, the amplitude of lightning current probability of the general area thunderbolt circuit that China's rules are recommended does

P＝10 ^-I/88 （2）

Differential obtains the amplitude of lightning current probability density function

$p\left(I\right)=\frac{\ln 10}{88}{10}^{-\frac{I}{88}}---\left(3\right)$

Circuit direct lightning strike trip-out rate computing formula does

${\mathrm{SFR}}_1=\frac{{2N}_g}{10}\mathrm{\η}{\∫}_{I_e}^{\∞}{D}_{c}p\left(I\right)\mathrm{dI}---\left(4\right)$

When thundercloud during near the ground discharge the circuit, the negative charge in the leader channel is by neutralization rapidly, and the electric field that leader channel produced reduces rapidly, makes the bound charge on the lead obtain discharging, and forms lightning induced voltage along lead two lateral movements.Simultaneously, the lightning current in the thunder and lightning passage has been set up powerful electromagnetic field at the passage surrounding space, and the variation of this electromagnetic field also will make lead induce very high voltage, and electrostatic induction voltage and electromagnetic induction voltage mutual superposition make and produce superpotential on the lead.Use the electromagnetic field method following to the computing formula of lightning induced voltage:

$U_g=\frac{I}{2\mathrm{\π}{\mathrm{\ϵ}}_{0}v}\ln [\frac{h}{S}+\sqrt{1+{\left(\frac{h}{S}\right)}^2}]---\left(5\right)$

Get Be constant, at S ²>>h ²The time, following formula can be reduced to

$U_g=K\frac{\mathrm{Ih}}{S}---\left(6\right)$

Above lightning induced voltage maximum amplitude is based on that Utopian hypothesis obtains, and in fact electrostatic induction thunder superpotential also will be revised, therefore add correction factor K ₁, then

$U_g=K_{K_1}\frac{\mathrm{Ih}}{S}---\left(7\right)$

In the lightning protection research abroad, get K=38.8 usually, and, get K1 according to the circuit concrete condition ₌0.6 ~ 0.9 revises.KK generally directly gets in China ₁=25 calculate lightning induced voltage.

The induced overvoltage U that produces on the line when thunderbolt ground _gThe time

$U_g=K_{K_1}\frac{\mathrm{Ih}}{S}>U_{50\%}---\left(8\right)$

Line insulator string generation flashover, this paper defines U _g=U _50%The time apart from S ₀Be critical flashover distance, obvious critical flashover distance is the function of amplitude of lightning current I and lead height h.

Therefore, line influence tripping rate with lightning strike computing formula does

${\mathrm{SFR}}_2=\frac{{2N}_g}{10}\mathrm{\η}{\∫}_{I_1}^{\∞}(S_0-D_c)p\left(I\right)\mathrm{dI}---\left(9\right)$

Lightning outage rate

SFR=SFR ₁+SFR ₂ （10）

The N that relates in the above calculating formula _gExpression ground dodges density, η representes that probability of sustained arc, I represent that amplitude of lightning current, h represent circuit average height, U _50%Expression low-voltage distributing line insulator chain impulse flashover voltage, D _cThe expression direct lightning strike draws thunder width, I ₁Produce the amplitude of lightning current critical value of lightning induced voltage on the expression circuit, S ₀When induction lightning network takes place on the expression circuit, the critical flashover distance of lightning strike spot.

According to electric geometric model principle, the thunder that drops in the distance of wire certain limit will be attacked lead directly, and the voltage that produces on the line when its lightning current is greater than insulator lightning impulse withstand voltage U _50%The time, insulation flashover takes place.The electric geometric model schematic diagram of 10kV distribution line as shown in Figure 1, D _cFor the circuit direct lightning strike draws thunder width, D _cSize and lead to expose arc relevant with the intersection point of the earth exposure arc, so D _cSize depend on the size of lightning current.The present invention divides two kinds of situation that the size of 10kV distribution wire pass thunder width is discussed.

It is with lead height O that lead exposes arc ₁(x ₀, h) be the center of circle, to hit apart from R _dBe the circle of radius, expose that the coordinate of any is on the arc (x, y), with horizontal angle be θ, its algebraic equation does

${\left({x-x}_0\right)}^2+{(y-h)}^2=R_d^2---\left(11\right)$

It is to be 0.9R apart from the earth horizontal range that ground exposes arc _dRay, its algebraic equation does

y＝x+0.9R _d/cosθ （12）

Simultaneous (11), (12) formula can be known, as 0＜I≤[(h-x ₀)/(0.6h ^0.6Sec θ-0.95h ^0.6)] ^1.35The time, the earth exposes arc at O ₁The below of point, D at this moment _c=R _d=0.67h ^0.6I ^0.74

As I＞[(h-x ₀)/(0.6h ^0.6Sec θ-0.95h ^0.6)] ^1.35The time, the earth exposes arc at O ₁The top of point, the group of solving an equation (4), (5) obtain intersection point

$x_1=\frac{x_0+h-0.54h^{0.6}{I}^{0.74}\mathrm{Sec}\mathrm{\θ}+\sqrt{{0.72h}^{1.2}{I}^{1.48}-{(x_0-h+0.5h^{0.6}+I^{0.74}\mathrm{Sec}\mathrm{\θ})}^2}}{2}$ At this moment, D _c=x ₁

In the following formula, x ₀Expression shaft tower cross-arm length, x ₁The expression the earth exposes arc and circuit exposes the horizontal range of the intersection point of arc to shaft tower, and θ representes ground elevation.

When being struck by lightning in the earth, the superpotential size U that on lead, produces _g=25Ih/S>U _50%The time, insulator chain flashover, i.e. S<25Ih/U _50%The time insulation flashover.It is S apart from the horizontal range of lead that the present invention defines lightning strike spot ₀=25Ih/U _50%The time distance be critical flashover distance.

Based on above theory, the appraisal procedure of low-voltage distributing line lightning stroke trip risk of the present invention, as shown in Figure 2, may further comprise the steps:

Step S1, at first gather the data relevant: ground sudden strain of a muscle density N with low-voltage distributing line _g, probability of sustained arc η, amplitude of lightning current I, circuit average height h, low-voltage distributing line insulator chain impulse flashover voltage U _50%

Step S2, according to formula (4) and (9), calculate direct lightning strike trip-out rate and induction thunder trip-out rate respectively;

Step S3, according to formula (10), with step S2 gained direct lightning strike trip-out rate and the addition of induction thunder trip-out rate, obtain total tripping rate with lightning strike, estimate the size of lightning stroke trip risk with this.

Low-voltage distributing line lightning stroke trip risk assessment device of the present invention is the device corresponding with above-mentioned appraisal procedure, and is as shown in Figure 3, comprising:

Data acquisition module is used to gather the relevant data of low-voltage distributing line: ground dodges density N _g, probability of sustained arc η, amplitude of lightning current I, circuit average height h, low-voltage distributing line insulator chain impulse flashover voltage U _50%

Direct lightning strike and induction thunder trip-out rate determination module are used for adopting respectively (4), (9) to calculate the direct lightning strike trip-out rate SFR of low-voltage distributing line ₁With induction thunder trip-out rate SFR ₂:

Total trip-out rate determination module is used for the direct lightning strike trip-out rate SFR to low-voltage distributing line ₁With induction thunder trip-out rate SFR ₂Summation obtains the low-voltage distributing line tripping rate with lightning strike.

Can know that by above description and Fig. 3 data acquisition module, direct lightning strike link to each other with total trip-out rate determination module with induction thunder trip-out rate determination module successively, have constituted this apparatus for evaluating.The other technologies characteristic of this apparatus for evaluating is identical with above-mentioned appraisal procedure, does not repeat them here.Appraisal procedure of the present invention is used in combination the purpose of the risk assessment that can realize tripping with apparatus for evaluating.

The above embodiment has only expressed several kinds of embodiments of the present invention, and it describes comparatively concrete and detailed, but can not therefore be interpreted as the restriction to claim of the present invention.Should be pointed out that for the person of ordinary skill of the art under the prerequisite that does not break away from the present invention's design, can also make some distortion and improvement, these all belong to protection scope of the present invention.Therefore, the protection domain of patent of the present invention should be as the criterion with accompanying claims.

Claims (4)

1. a low-voltage distributing line lightning stroke trip methods of risk assessment is characterized in that, comprises step:

Gather the relevant data of low-voltage distributing line: ground dodges density N _g, probability of sustained arc η, amplitude of lightning current I, circuit average height h, insulator chain impulse flashover voltage U _50%

Adopt the direct lightning strike trip-out rate SFR of computes low-voltage distributing line respectively ₁With induction thunder trip-out rate SFR ₂:

${\mathrm{SFR}}_1=\frac{{2N}_g}{10}\mathrm{\&eta;}{\&Integral;}_{I_e}^{\&infin;}{D}_{c}p\left(I\right)\mathrm{dI}$

${\mathrm{SFR}}_2=\frac{{2N}_g}{10}\mathrm{\&eta;}{\&Integral;}_{I_1}^{\&infin;}(S_0-D_c)p\left(I\right)\mathrm{dI}$

In the following formula, D _cExpression circuit direct lightning strike draws thunder width, I _eExpression circuit direct lightning strike lightning withstand level, I ₁Produce the amplitude of lightning current critical value of lightning induced voltage on the expression circuit, S ₀When induction lightning network takes place on the expression circuit, the critical flashover distance of lightning strike spot, p (I) expression amplitude of lightning current probability density function;

Direct lightning strike trip-out rate SFR to low-voltage distributing line ₁With induction thunder trip-out rate SFR ₂Summation obtains the low-voltage distributing line tripping rate with lightning strike.

2. low-voltage distributing line lightning stroke trip methods of risk assessment according to claim 1 is characterized in that said I _eExpression formula do The expression formula of said S0 does

The expression formula of said p (I) does

Said D _cExpression formula be:

As 0＜I≤[(h-x ₀)/(0.6h ^0.6Sec θ-0.95h ^0.6)] ^1.35, D _c=0.67h ^0.6I ^0.74

As I＞[(h-x ₀)/(0.6h ^0.6Sec θ-0.95h ^0.6)] ^1.35The time, D _c=x ₁,

$x_1=\frac{x_0+h-0.54h^{0.6}{I}^{0.74}\sec \mathrm{\&theta;}+\sqrt{{0.72h}^{1.2}{I}^{1.48}-{(x_0-h+0.5h^{0.6}+I^{0.74}\sec \mathrm{\&theta;})}^2}}{2}$

In the following formula, x ₀Expression shaft tower cross-arm length, x ₁The expression the earth exposes arc and circuit exposes the horizontal range of the intersection point of arc to shaft tower, and θ representes ground elevation.

3. a low-voltage distributing line lightning stroke trip risk assessment device is characterized in that, comprising:

Data acquisition module is used to gather the relevant data of low-voltage distributing line: ground dodges density N _g, probability of sustained arc η, amplitude of lightning current I, circuit average height h, insulator chain impulse flashover voltage U _50%

Direct lightning strike and induction thunder trip-out rate determination module are used for adopting respectively the direct lightning strike trip-out rate SFR of computes low-voltage distributing line ₁With induction thunder trip-out rate SFR ₂:

${\mathrm{SFR}}_1=\frac{{2N}_g}{10}\mathrm{\&eta;}{\&Integral;}_{I_e}^{\&infin;}{D}_{c}p\left(I\right)\mathrm{dI}$

${\mathrm{SFR}}_2=\frac{{2N}_g}{10}\mathrm{\&eta;}{\&Integral;}_{I_1}^{\&infin;}(S_0-D_c)p\left(I\right)\mathrm{dI}$

In the following formula, D _cExpression circuit direct lightning strike draws thunder width, I _eExpression circuit direct lightning strike lightning withstand level, I ₁Produce the amplitude of lightning current critical value of lightning induced voltage on the expression circuit, S ₀When induction lightning network takes place on the expression circuit, the critical flashover distance of lightning strike spot, p (I) expression amplitude of lightning current probability density function;

Total trip-out rate determination module is used for the direct lightning strike trip-out rate SFR to low-voltage distributing line ₁With induction thunder trip-out rate SFR ₂Summation obtains the low-voltage distributing line tripping rate with lightning strike.

4. low-voltage distributing line lightning stroke trip risk assessment device according to claim 3 is characterized in that said I _eExpression formula do

Said S ₀Expression formula do

The expression formula of said p (I) does Said D _cExpression formula be:

As 0＜I≤[(h-x ₀)/(0.6h ^0.6Sec θ-0.95h ^0.6)] ^1.35, D _c=0.67h ^0.6I ^0.74

As I＞[(h-x ₀)/(0.6h ^0.6Sec θ-0.95h ^0.6)] ^1.35The time, D _c=x ₁,

$x_1=\frac{x_0+h-0.54h^{0.6}{I}^{0.74}\sec \mathrm{\&theta;}+\sqrt{{0.72h}^{1.2}{I}^{1.48}-{(x_0-h+0.5h^{0.6}+I^{0.74}\sec \mathrm{\&theta;})}^2}}{2}$

In the following formula, x ₀Expression shaft tower cross-arm length, x ₁The expression the earth exposes arc and circuit exposes the horizontal range of the intersection point of arc to shaft tower, and θ representes ground elevation.

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