SU1559318A1 - Method of determining distance to spot of phase ground fault in circuits with neutral insulated - Google Patents

Abstract

This invention relates to relay protection and can be used to determine the distance to the point where a wire is closed to earth in networks with insulated neutral. The purpose of the invention is to improve the accuracy of determining the distance to the point of closure. A monitored network imposes a current from a voltage source of a non-industrial frequency, in a circuit consisting of a series-connected regulated inductance and an equivalent network capacity relative to the earth, a voltage resonance is established. Upon reaching resonance, the inductance value is fixed. When a phase to ground fault occurs, the voltage at the equivalent network capacity and the angle between this voltage and the source voltage are fixed. Using the value of the obtained values and the value of the linear inductance of the line, calculate the distance to the site of damage. The invariance of the applied current flowing through the damaged wire is used to increase the efficiency of determining the location of the damage in the course search method. 1 il.

Description

The invention relates to relay protection and emergency control of power lines and can be used to determine the distance to the location of a phase closure:,; to earth (POZ) in a network with an isolated neutral.

The aim of the invention is to improve the accuracy of determining the distance to the point of closure of the phase conductor to earth by eliminating the effect on the measurement accuracy of the magnitude of the transient resistance at the point of closure and the RCCT of the wire relative to the earth.

The drawing shows a block diagram of a device for implementing this method.

The essence of the method is

creating a resonant circuit of a controlled inductance and network elements for the applied non-industrial frequency current, followed by measuring when the monitored line phase closes the electrical parameters caused by the flow of the superimposed current, and calculated from the measured distance to the fault.

The device for carrying out the method comprises a generator 1, a contact 2 relay protection, a current-limiting resistor 3, an adjustable inductance coil 4 (L), a resistance of 5 lines, an inductance of 6 lines, a transition resistance of 7, equivalent capacitance 8, compensating device 9. In this case, the generator 1, adjustable inductance 4, the compensating device 9, equivalent capacitance 8, the current-limiting resistor 3 form a series closed loop, contact eynoy shunts the current limiting protection rezistor.3, and the chain of series-connected inductive reactance line 6, the resistivity of the active line 5 and Peret Khodnev resistance 7 connected in parallel with an equivalent capacitive reactance 8

The device works as follows.

According to the drawing, for current I ,,, flowing through the active

(R01X) 5 and inductive

(

one.)

6 of the line resistance, and also through the active transition resistance (Rn) 7 in the place of the phase closure to the ground, write the following expression

 U-diXc)

3 Ix c7 x + 7Rn + Vix + Vx (ix-jx «)

(one)

de h.d equivalent capacitance-.

Je resistance 8 of the mains wire relative to the ground current from the generator 1, Ohm;

Sd is equivalent to the capacitance of the wire closed through the resistance Rn to earth. yes, f;

X СО1 L - inductive resistance of the coil, Ohm;

L is the inductance of the coil, GN; Q 2 / and -Ј is the circular frequency;

U is the voltage of the non-industrial frequency generator, V;

45

50

„- distance to the place

closure, km

It follows from equation (I) that current 13 is independent of the change in parameters

R0 + JX0 lx + R0-lx with the ratio

X

se

 x,

(2)

And this can be achieved at voltage resonance in the normal mode of network operation, bearing in mind that Rn with contact 2 of the relay protection is open.

Resonance of voltages in the circuit: adjustable inductance - the equivalent network capacity relative to the earth is established by changing the adjustable inductance L (the resistance of the compensating device to the superposed current is zero).

The amount of current flowing in this mode along the circuit is limited by a resistor. Resistor 3 by opening contact 2 is put into operation and when the phase to ground fault disappears during measurements.

When a voltage resonance is reached, the inductance L is fixed. Taking into account that X Xse,

U / jx.

(3)

Taking into account the expression (3), the distance Ijt to the closure point is found from the expression

t uqb

1st ----

I, - X,

sinif

(four)

where u. - voltage between point

(c), taken from the regulated resonant inductance L and ground, B; X0 27fLe; LO - inductance of one kilo: meter line, Gn / km; t {is the angle between the voltage U.

and a current of 13,

Taking into account expression (2) and in accordance with FIG. 2 with (f, 90 ° -tf, equation 4 can be written as

, X tab

xx; gb-cosfti

(five)

where oi is the angle between voltages U

50 and U

A8

The resistance Rn also affects the operation of portable devices that react to higher harmonic components, since when measuring, for example, due to the wind, the arc is stretched at the point of damage. The change due to this resistance Rn causes a change in the value of the current

Claims (1)

Claim 1. The method of determining the distance to the point of phase to ground fault in networks with isolated neutral, consisting in the fact that when turned on through a compensating device between the ground and the phase of the non-industrial frequency source checked, a voltage resonance is established in the circuit, consisting of the capacitance of the network wires and an additional adjustable inductance during normal operation of the power supply network, a stabilized current of non-industrial frequency is obtained, flowing through a wire closed to the ground - and lagging from the voltage source of the increased frequency by ninety degrees, it is distinguished by the fact that, in order to increase the accuracy, they fix the value of the resonant inductance of the circuit, measure the voltage between the point of attachment of the resonance inductance to the mains and ground, measure the angle between the measured voltage and the known voltage source of non-industrial frequency, and the distance to the point of phase to ground is determined by the formula 1χ = ^L / L _o ~ - cos <f, - the value of the resonant inductance of the selected circuit; - inductance of one km of the line; - voltage between the point of attachment of the resonant inductance to the mains and ground; - the angle between the measured voltage and the voltage of the source of non-industrial frequency U. The method according to claim 1, is characterized by the fact that, in order to clarify the closure, the places laid are laid stable in time. current flowing through a wire closed to ground using a portable device on the line