CN102818959B - Method for calculating minimum air clear distance of direct current valve hall based on improved clearance coefficient - Google Patents

Abstract

The invention relates to a method for calculating minimum an air clear distance of a direct current valve hall based on an improved clearance coefficient, belonging to the field of designs of direct current transmission lines of transmission and transformation projects. The method comprises the steps of: firstly, obtaining a gap discharge voltage of each gap in a valve hall through a switching impulsive discharge test; then determining a function relationship among the gap discharge voltage, the electrode size and the gap distance by using a least square method; obtaining an improved gap coefficient taking influences of electrode size and gap distance into consideration by using the function relationship; and finally, determining the minimum air clear distance of the direct current valve hall by using an iteration method according to the improved gap coefficient. According to the method provided by the invention, the minimum air clear distance of the direct current valve hall can be obtained by calculation, and can be reduced as far as possible when the operation safety of equipment can be ensured, and project investment is saved.

Description

The minimum air clearance computing method in the straight-wavy valve Room based on improving percent break

Technical field

The present invention relates to the minimum air clearance computing method in a kind of straight-wavy valve Room based on improving percent break, the method that relates in particular to the air clearance of electrical equipment in current conversion station in a kind of definite DC transmission system, converting plant, the Inverter Station valve Room, belongs to project of transmitting and converting electricity DC power transmission line design field.

Background technology

The straight-wavy valve Room refers to placement converter valve, the rectifying valve of current conversion station in DC transmission system, converting plant, Inverter Station, the special place of inversion valve.Air gap distance between each electrical equipment (as valve, sleeve pipe, transformer) in the straight-wavy valve Room and between equipment and body of wall or ground, is called air clearance.Air clearance has material impact to construction costs, the factor that must consider while being the design straight-wavy valve Room.Air clearance is generally determined by thunder and lightning and the switching impulse sparkover voltage in gap.Right ± 500kV and the above straight-wavy valve Room, the air clearance being determined by switching impulse sparkover voltage is generally less than the clearance being determined by lightning impulse sparking voltage.

The computing method of the minimum air clearance in the straight-wavy valve Room being determined by switching impulse sparkover voltage extensively adopting in engineering design at present, are as follows:

(1) obtain under standard atmosphere condition the superpotential U that the clearance of considering need tolerate _w-corr.U _w-corrcomputing formula be

$U_{w-\mathrm{corr}}=\frac{k_m{U}_w}{K_t(1-2\mathrm{\σ})}---\left(1\right)$

Wherein U _wfor the switching impulse dielectric level of electrical equipment under the typical meteorological condition of the valve Room; k _mit is design margin; K _tit is Atmospheric corrections coefficient; σ is the coefficient of variation of gap discharge voltage, and to switching impulse, σ gets 6%.

(2) calculate minimum air clearance.Minimum air clearance computing formula is

$L=\sqrt[0.6]{\frac{U_{w-\mathrm{corr}}}{500K}}---\left(2\right)$

Wherein d is minimum air clearance, and unit is m; K is the percent break that characterizes electrode shape characteristic, and different coefficients represents different electrode type, and general selection is as follows: line---sheet separation K=1.15, wire---conductor spacing K=1.3, rod---excellent gap K=1.4.

In said method, the value of percent break is mainly for rod---plate, rod-rod, line---the conventional gap such as plate, in esse gap-type and electrode structure in a large amount of valves Room, as ball---plate or grading ring---consideration is not given in sheet separation; The electrode structure definite to certain, percent break only has a kind of value, does not consider the impact of the variable such as clearance distance and electrode size on percent break value.Above-mentioned computing method are more coarse, and error is larger.

The value of percent break K is directly related with air clearance, and the size of air clearance directly has influence on valve Room size, and then affects construction costs.For guarantee equipment and personal safety, said method in use needs to leave larger nargin, has greatly increased construction investment.

In recent years, China's DC transmission engineering is more and more.Engineering design is in the urgent need to a kind of percent break obtaining value method and the minimum clearance computing method that can consider the many factors such as valve Room actual gap type and electrode structure, electrode size.

Summary of the invention

The object of the invention is to propose the minimum air clearance computing method in a kind of straight-wavy valve Room based on improving percent break, consider gap-type, electrode size, clearance distance, meteorological condition and sea level elevation etc. in the valve Room, improve percent break by introducing, utilize meteorological condition and the sea level elevation modification method of existing comparative maturity, determine easily the minimum clearance of safe straight-wavy valve Room air.

The minimum air clearance computing method in the straight-wavy valve Room based on improving percent break that the present invention proposes, comprise the following steps:

(1) establishing the gap-type between electrical equipment in the straight-wavy valve Room comprises: ball or ring are to plate, pipe bus to plate, ball or ring to pipe bus, pipe bus to pipe bus and valve tower over the ground, for every kind of gap-type, obtain clearance distance d and electrode size r by actual measurement, by switching impulse discharge test, obtain the sparking voltage U corresponding with this clearance distance and electrode size ₅₀, repeat this step, obtain clearance distance d, electrode size r and the sparking voltage U of same gap-type ₅₀between discrete point combination (d ₁, r ₁, U ₅₀₁), (d ₂, r ₂, U ₅₀₂), (d ₃, r ₃, U ₅₀₃) ... (d _i, r _i, U _50i), wherein i measures number of times;

(2) to above-mentioned each gap-type, by the each gap discharge voltage U of following formula matching ₅₀and the funtcional relationship between each clearance distance d and electrode size r, electrode is wherein any in ball, ring, pipe bus or valve tower:

$U_{50}=d^{\frac{5}{3}}(b_0+b_1\left(\frac{1}{d}\right)+b_2{\left(\frac{1}{d}\right)}^2)(a_0+a_{1}r+a_2{r}^2)$

Wherein a ₀, a ₁, a ₂, b ₀, b ₁and b ₂respectively coefficient undetermined,

By (d ₁, r ₁, U ₅₀₁), (d ₂, r ₂, U ₅₀₂), (d ₃, r ₃, U ₅₀₃) ... (d _i, r _i, U _50i) in respectively substitution above formula of value, calculate coefficient a by least square method ₀, a ₁, a ₂, b ₀, b ₁and b ₂;

(3) according to the sparking voltage U of step (2) ₅₀function expression, obtain the improvement percent break expression formula K under switching impulse effect:

$K=\frac{(b_0+b_1\frac{1}{d}+b_2{\left(\frac{1}{d}\right)}^2)(a_0+a_{1}r+a_2{r}^2)}{500}$

(4) according to the expression formula K of above-mentioned improvement percent break, calculate the minimum clearance in all types of gaps, concrete grammar is as follows:

(4-1), according to the requirement of DC power transmission system systems engineering Xi, set a design margin k _m, and calculate the relative air density δ under the service condition of the straight-wavy valve Room:

$\mathrm{\δ}=\frac{p}{p_0}\frac{273+t_0}{273+t}$

Wherein p ₀for the atmospheric pressure under standard state, t ₀for the temperature under standard state, p is the air pressure under the service condition of the straight-wavy valve Room, and t is the temperature under the service condition of the straight-wavy valve Room;

(4-2) set two intermediate parameters m and w, when initialization, the value of two intermediate parameters m and w is 0, and definition atmospheric density correction factor is k ₁, definition humidity correction factor is k ₂, initial value is established k ₁=1, k ₂=1, and establish initial improvement percent break K=1;

(4-3) calculate Atmospheric corrections COEFFICIENT K _t, K _t=k ₁k ₂;

(4-4) the sparking voltage U of calculated gap _w-corr, wherein U _wfor the switching impulse insulation tolerance value of the electrical equipment that is connected with electrode in the straight-wavy valve Room, k _mdesign margin, K _tbe Atmospheric corrections coefficient, σ is the coefficient of variation of gap discharge voltage, and for switching impulse, σ gets 6%;

(4-5) according to above-mentioned U _w-corr, calculate a clearance distance d:

$d=\sqrt[0.6]{\frac{U_{w-\mathrm{corr}}}{500K}}$

(4-6), according to electrode size r and above-mentioned clearance distance d, calculate and improve percent break K:

$K=\frac{(b_0+b_1\frac{1}{d}+b_2{\left(\frac{1}{d}\right)}^2)(a_0+a_{1}r+a_2{r}^2)}{500}$

(4-7) utilize the K obtaining in the d that obtains in step (4-5) and step (4-6), obtain an intermediate parameters g:

$g=\frac{U_{w-\mathrm{corr}}}{500\mathrm{d\δK}}$

(4-8), according to the funtcional relationship in above-mentioned g value and following table, calculate intermediate parameters m and w;

The funtcional relationship of intermediate parameters m and w and intermediate parameters g

(4-9), according to the m and the w that obtain in step (4-8), calculate Atmospheric corrections COEFFICIENT K _t,

k ₁＝δ ^m

k ₂＝k ^w

$k=1+0.01(\frac{d}{\mathrm{\δ}}-11)$

K _t＝k ₁k ₂；

(4-10) the clearance distance d of step (4-5) is judged, if while facing twice iteration mutually, the relative difference of d is less than or equal to 0.1%, stop calculating, and the minimum air clearance in the straight-wavy valve Room under using this clearance distance d as these natural conditions, if while facing twice iteration mutually, the relative difference of d is greater than 0.1%, and repeating step (4-5) is to (4-10).

The minimum air clearance computing method in the straight-wavy valve Room based on improving percent break that the present invention proposes, compared with the prior art, can take into full account true electrode structure and size and the impact of clearance distance on percent break value in the valve Room.The minimum air clearance in the straight-wavy valve Room determines the size in the valve Room, can significantly affect the overall cost in device fabrication difficulty and the straight-wavy valve Room.Determine the minimum air clearance in the straight-wavy valve Room according to the present invention, can, in the equipment of guarantee security of operation, reduce as far as possible air clearance value, cost saving.Computing method of the present invention, mainly for the air clearance being determined by switching impulse, but the inventive method and principle are applicable equally to lightning impulse.

Embodiment

The minimum air clearance computing method in the straight-wavy valve Room based on improving percent break that the present invention proposes, comprise the following steps:

(1) establishing the gap-type between electrical equipment in the straight-wavy valve Room comprises: ball or ring are to plate, pipe bus to plate, ball or ring to pipe bus, pipe bus to pipe bus and valve tower over the ground, for every kind of gap-type, obtain clearance distance d and electrode size r by actual measurement, by switching impulse discharge test, obtain the sparking voltage U corresponding with this clearance distance and electrode size ₅₀, repeat this step, obtain clearance distance d, electrode size r and the sparking voltage U of same gap-type ₅₀between discrete point combination (d ₁, r ₁, U ₅₀₁), (d ₂, r ₂, U ₅₀₂), (d ₃, r ₃, U ₅₀₃) ... (d _i, r _i, U _50i), wherein i measures number of times;

(2) to above-mentioned each gap-type, by the each gap discharge voltage U of following formula matching ₅₀and the funtcional relationship between each clearance distance d and electrode size r, electrode is wherein any in ball, ring, pipe bus or valve tower:

$U_{50}=d^{\frac{5}{3}}(b_0+b_1\left(\frac{1}{d}\right)+b_2{\left(\frac{1}{d}\right)}^2)(a_0+a_{1}r+a_2{r}^2)$

Wherein a ₀, a ₁, a ₂, b ₀, b ₁and b ₂respectively coefficient undetermined,

By (d ₁, r ₁, U ₅₀₁), (d ₂, r ₂, U ₅₀₂), (d ₃, r ₃, U ₅₀₃) ... (d _i, r _i, U _50i) in respectively substitution above formula of value, calculate coefficient a by least square method ₀, a ₁, a ₂, b ₀, b ₁and b ₂;

(3) according to the sparking voltage U of step (2) ₅₀function expression, obtain the improvement percent break expression formula K under switching impulse effect:

$K=\frac{(b_0+b_1\frac{1}{d}+b_2{\left(\frac{1}{d}\right)}^2)(a_0+a_{1}r+a_2{r}^2)}{500}$

(4) according to the expression formula K of above-mentioned improvement percent break, calculate the minimum clearance in all types of gaps, concrete grammar is as follows:

(4-1), according to the engine request of DC transmission system, set a design margin k _m, and calculate the relative air density δ under the service condition of the straight-wavy valve Room:

$\mathrm{\δ}=\frac{p}{p_0}\frac{273+t_0}{273+t}$

Wherein p ₀for the atmospheric pressure under standard state, t ₀for the temperature under standard state, p is the air pressure under the service condition of the straight-wavy valve Room, and t is the temperature under the service condition of the straight-wavy valve Room;

(4-2) set two intermediate parameters m and w, when initialization, the value of two intermediate parameters m and w is 0, and definition atmospheric density correction factor is k ₁, definition humidity correction factor is k ₂, initial value is established k ₁=1, k ₂=1, and establish initial improvement percent break K=1;

(4-3) calculate Atmospheric corrections COEFFICIENT K _t, K _t=k ₁k ₂;

(4-4) the sparking voltage U of calculated gap _w-corr, wherein U _wfor the switching impulse insulation tolerance value of the electrical equipment that is connected with electrode in the straight-wavy valve Room, k _mdesign margin, K _tbe Atmospheric corrections coefficient, σ is the coefficient of variation of gap discharge voltage, and for switching impulse, σ gets 6%;

(4-5) according to above-mentioned U _w-corr, calculate a clearance distance d:

$d=\sqrt[0.6]{\frac{U_{w-\mathrm{corr}}}{500K}}$

(4-6), according to electrode size r and above-mentioned clearance distance d, calculate and improve percent break K:

$K=\frac{(b_0+b_1\frac{1}{d}+b_2{\left(\frac{1}{d}\right)}^2)(a_0+a_{1}r+a_2{r}^2)}{500}$

(4-7) utilize the K obtaining in the d that obtains in step (4-5) and step (4-6), obtain an intermediate parameters g:

$g=\frac{U_{w-\mathrm{corr}}}{500\mathrm{d\δK}}$

(4-8), according to the funtcional relationship in above-mentioned g value and following table, calculate intermediate parameters m and w;

The funtcional relationship of intermediate parameters m and w and intermediate parameters g

(4-9), according to the m and the w that obtain in step (4-8), calculate Atmospheric corrections COEFFICIENT K _t,

k ₁＝δ ^m

k ₂＝k ^w

$k=1+0.01(\frac{d}{\mathrm{\δ}}-11)$

K _t＝k ₁k ₂；

(4-10) the clearance distance d of step (4-5) is judged, if while facing twice iteration mutually, the relative difference of d is less than or equal to 0.1%, stop calculating, and the minimum air clearance in the straight-wavy valve Room under using this clearance distance d as these natural conditions, if while facing twice iteration mutually, the relative difference of d is greater than 0.1%, and repeating step (4-5) is to (4-10).

Claims (1)

1. the minimum air clearance computing method in the straight-wavy valve Room based on improving percent break, is characterized in that the method comprises the following steps:

(1) establishing the gap-type between electrical equipment in the straight-wavy valve Room comprises: ball or ring are to plate, pipe bus to plate, ball or ring to pipe bus, pipe bus to pipe bus and valve tower over the ground, for every kind of gap-type, obtain clearance distance d and electrode size r by actual measurement, by switching impulse discharge test, obtain the sparking voltage U corresponding with this clearance distance and electrode size ₅₀, repeat this step, obtain clearance distance d, electrode size r and the sparking voltage U of same gap-type ₅₀between discrete point combination (d ₁, r ₁, U ₅₀₁), (d ₂, r ₂, U ₅₀₂), (d ₃, r ₃, U ₅₀₃) ... (d _i, r _i, U _50i), wherein i measures number of times;

(2) to above-mentioned each gap-type, by the each gap discharge voltage U of following formula matching ₅₀and the funtcional relationship between each clearance distance d and electrode size r, electrode is wherein any in ball, ring, pipe bus or valve tower:

$U_{50}=d^{\frac{5}{3}}(b_0+b_1\left(\frac{1}{d}\right)+b_2{\left(\frac{1}{d}\right)}^2)(a_0+a_{1}r+a_2{r}^2)$

Wherein a ₀, a ₁, a ₂, b ₀, b ₁and b ₂respectively coefficient undetermined,

By (d ₁, r ₁, U ₅₀₁), (d ₂, r ₂, U ₅₀₂), (d ₃, r ₃, U ₅₀₃) ... (d _i, r _i, U _50i) in respectively substitution above formula of value, calculate coefficient a by least square method ₀, a ₁, a ₂, b ₀, b ₁and b ₂;

(3) according to the sparking voltage U of step (2) ₅₀function expression, obtain the improvement percent break expression formula K under switching impulse effect:

$K=\frac{(b_0+b_1\frac{1}{d}+b_2{\left(\frac{1}{d}\right)}^2)(a_0+a_{1}r+a_2{r}^2)}{500}$

(4) according to above-mentioned improvement percent break expression formula K, calculate the minimum air clearance in all types of gaps, concrete grammar is as follows:

(4-1), according to the engine request of DC transmission system, set a design margin k _m, and calculate the relative air density δ under the service condition of the straight-wavy valve Room:

$\mathrm{\δ}=\frac{p}{p_0}\frac{273+t_0}{273+t}$

Wherein p ₀for the atmospheric pressure under standard state, t ₀for the temperature under standard state, p is the air pressure under the service condition of the straight-wavy valve Room, and t is the temperature under the service condition of the straight-wavy valve Room;

(4-2) set two intermediate parameters m and w, when initialization, the value of two intermediate parameters m and w is 0, and definition atmospheric density correction factor is k ₁, definition humidity correction factor is k ₂, initial value is established k ₁=1, k ₂=1, and establish initial improvement percent break K=1;

(4-3) calculate Atmospheric corrections COEFFICIENT K _t, K _t=k ₁k ₂;

(4-4) the sparking voltage U of calculated gap _w-corr, wherein U _wfor the switching impulse insulation tolerance value of the electrical equipment that is connected with electrode in the straight-wavy valve Room, k _mdesign margin, K _tbe Atmospheric corrections coefficient, σ is the coefficient of variation of gap discharge voltage, and for switching impulse, σ gets 6%;

(4-5) according to above-mentioned U _w-corr, calculate a clearance distance d:

$d=0.6\sqrt{\frac{U_{w-\mathrm{corr}}}{500K}}$

(4-6), according to electrode size r and above-mentioned clearance distance d, calculate and improve percent break K:

$K=\frac{(b_0+b_1\frac{1}{d}+b_2{\left(\frac{1}{d}\right)}^2)(a_0+a_{1}r+a_2{r}^2)}{500}$

(4-7) utilize the K obtaining in the d that obtains in step (4-5) and step (4-6), obtain an intermediate parameters g:

$g=\frac{U_{w-\mathrm{corr}}}{500\mathrm{d\δK}}$

(4-8), according to the funtcional relationship in above-mentioned g value and following table, calculate intermediate parameters m and w;

The funtcional relationship of intermediate parameters m and w and intermediate parameters g

(4-9), according to the m and the w that obtain in step (4-8), calculate Atmospheric corrections COEFFICIENT K _t,

k ₁＝δ ^m

k ₂＝k ^w

$k=1+0.01(\frac{d}{\mathrm{\δ}}-11)$

K _t＝k ₁k ₂；

(4-10) the clearance distance d of step (4-5) is judged, if while facing twice iteration mutually, the relative difference of d is less than or equal to 0.1%, stop calculating, and the minimum air clearance in the straight-wavy valve Room under using this clearance distance d as natural conditions, if while facing twice iteration mutually, the relative difference of d is greater than 0.1%, and repeating step (4-5) is to (4-10).