SU1585767A1 - Method of determining the distance to places of double ground fault - Google Patents

Abstract

The invention can be used to determine the distance to damage points on overhead transmission lines in networks with insulated neutral voltage of 6 - 35 kV. The aim of the invention is to improve the accuracy of determining the distance to the closure points located on the same power line. The essence of the method for determining the distance to ground short circuits is that a more distant circuit is detected at a higher value of the reactive component of the phase voltage in the emergency mode, and the distance to the fault sites is determined taking into account the zero-sequence resistance of the section the lines between the closure points and the different resistivity to the near closure point.

Description

The invention relates to power engineering and can be used to determine the distance to damage sites on overhead power lines in networks with insulated neutral voltage of 6-35 kV.

The goal of research is to increase the accuracy of distance determination. to the closures located on the same transmission line, by taking into account different resistivity to the nearest ground fault point and the resistivity of the meaode by points of damage.

FIG. 1 shows a schematic of a 35 kV network; in fig. 2 - vector diagram of the springs and currents at double circuit to earth.

FIG. 1, the following notation is introduced: Ed, Yor, Y. - in the phases A, B, C of the supply system; Z ,, Zg, Z. - phase resistance. A, B, C supply system; Р - substation busbars 35 kV; M, N - ground closure points, respectively, of phases B, C; V, W - Zempi points behind transitional resistances of phases B, C; Rj, R are the transient resistances of the earth fault points W and V; TT CL

00

cl

vl

with sl

current transformers connected to the fixing device (meter); TN is a voltage transformer connected to a fixing device (measure

tel).

The essence of the method is the Tom that reveals a more distant ground fault location for the larger value of the reactive phase voltage component in the emergency mode, and the distance to the fault sites is determined by taking into account the zero-sequence resistance of the line section between the ground fault points.

The discovery of the short-circuit mode is performed with the help of threshold bodies of relay protection and automation. The reaction of the reactive voltage components of the damaged phases is carried out using phase detectors. The reactive components of the voltage are compared with each other, for example, using a comparator. The implementation of the calculations by the formula can be organized programmatically using a microcontroller or using elements of analog circuits used to perform similar calculations in the fixing resistance indicator.

When a double ground fault occurs, for example in phases B, C (Fig. 1), on. one radial line current at any point of phase A may be taken to be zero. The currents of phases B and C are respectively equal to and equal to the short-circuit current (CC) I j in the fault loop. Based on the second law of Kirchhoff, we can write down:

-6

.lirij

K 2z ;; 2z7f7 / R7v

ZM - where Z f, is the resistance of the supply phase

systems; 45

Unit - resistance of the line section to the first ground fault point; sop1 otvleniye of a section of the line between points of closing R, contact resistance at the closure points, to ground. Phase voltages are found as the voltage drop from the considered line trip to the points of zero potential V, W:

(2)

to the stack from the place of control of the point P to; point N will be;

UBC s1n. (And her) Y - mgG

the sun

UK & in (.) 21

 MN

(6)

ttHWV B U4 i (2MN-V 6 where .2I is the linear current of the damaged phases;: and gj.U is the voltage of the bursts of the damaged g phases.

In accordance with known methods, the measured reactance in the short-circuit loop is proportional. (3) distance to the point of damage, s

55

j

Yu

The phase voltages measured on the buses of the substation P are equal to expressions (2), (3), since there is no drop in voltage relative to earth in the section PN (Fig. 1). When measuring the sine of the angle between the current and the voltage of the damaged phases, a further value of the sine of the angle corresponds to a further point of the closure (Fig. 2), where IxRu,

, 1b and

 , voltage drop, respectively, on the resistances R, R ,,

l voltage drop respectively on resistors

20

25

thirty

45

- and .15 of power R, R ,. X, tJ, Ug

voltages in phases C and B, measured at substation tires; U - voltage

Ic 35

40

between damaged phases; Ig, currents flowing through the short circuit loop; ifg, (angles between currents and voltages of damaged phases. It is obvious (Fig. 2) that sin4 g sin if is a reactive component of phase voltage B

the more reactive component of the phase voltage C and (.X. by the value of, d, i.e. the presence of zero sequence resistance (XD.) on the section of the MN line causes the inequality to be fulfilled

(

The inductive resistance in the damaged line section between points M and N is determined as

Y s PX F C-. . we.ib.

Ugii sin (U, IK) (5)

Ix

Inductive resistance at the

to the stack from the place of control of the point P to; point N will be;

UBC s1n. (And her) Y - mgG

the sun

UK & in (.) 21

 MN

(6)

Considering the above distance to the nearest point, the damage is equal to: L .Kj.yKsin ().

21k

and .. 1. and

ten

y Siliiy IxIil (7)

 I to

e K, K - transformation ratios of current transformers and voltage of the controlled line; voltages between damaged phases; loop current short circuit J5;

voltage phase relative to earth with a more distant earth fault point;

inductive resistivity of the line.

20

The distance to the more distant point is equal; . .

, Ki and, s1n (IF ", 1k) Lb + -,

033 f

(3)

in UA

where is the voltage of the phase relative to the earth with a more distant ground fault point; the resistivity of the zero sequence of the line section between the ground fault points. ovA can be taken equal

expression (1).

1.83 (x., + X): ix.

Claims (1)

Invention Formula The method of determining the distance to the places of the double ground fault pu : ten - J5 measurement of component voltages and currents of damaged phases. a controlled power line in emergency mode and calculation from measured values of reactances to the places of damage, characterized in that, in order to determine the accuracy of determining the distance to the closing points located on the same power line, the damaged phase with the more remote closing point is determined by greater value of the reactive component of the phase voltage of the damaged phases, and the distance to the point of control, which is closest to the control point, is defined as 20 L 5J Y U 1§111 (ikA1k) 1 HudKu 21ts Chief sin (, IK) 25 thirty  UA and. 35 40 where is the resistivity, in the area up to the first ground fault location; transformation ratios of current transformers and voltage of controlled line; voltage between the damaged phases; tbk in the loop of damage; voltage to ground with a more distant closure point, distance to more distant point closures are defined as , t .. Ki.yj., sin (.Ijs) 1 1 V 1 T   Ku i. where X is the resistivity  zero sequence of the line segment between the ground fault points. and IK - F1 Icx. FIG. 2