SU650149A1 - Method of detecting power transmission line short-circuiting location - Google Patents

Description

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The invention relates to the field of relay protection of power lines and can be used to protect high voltage lines 50U-libO kV.

.1 a method of protecting high voltage lines is known, based on the analysis of electromagnetic waves associated with the presence of an electromagnetic transient 1J. Possessing high speed, this method, however, is difficult to use and is subject to interference from network commutations and lightning discharges. In addition, a short circuit with this method can be fixed only in the initial stage after its occurrence.

The closest in technical essence is a method of fixing a short circuit in the differential-phase b4 protection 2J. This method compares the phases of the sum of the forward sequence currents and the parts of the negative sequence current or the sum of the direct sequence current and the parts of the zero sequence current at the ends of the transmission line. This method is applied on 220-500 k6 lines up to 350-400 km long.

However, with this method, with a transmission line length of more than 400 km, correct measurement of the phases of the currents at the ends of the line with

short circuit is difficult due to the capacitive conductivity of the lines. In addition, if there is a concentrated capacitance outside the protection zone (for example, a longitudinal compensation device) and a short circuit outside the protection zone, it is possible that the damage is not fixed in the protection zone. The presence of forward and reverse sequence filters increases the protection time.

The aim of the invention is to improve the accuracy for long power lines.

The goal is achieved by the fact that in the method based on applying and forming electromagnetic waves at the ends of the line, transferring them to the anti-pole line ends, comparing them in phase between themselves and fixing a short circuit when the phases do not match, electromagnetic waves are formed by subtracting the phase wave and the wave zero sequence, combined with the interfacial wave of the other two phases, multiplied by the coefficient of fate.

The drawing shows a block diagram of the device that implements the method.

The device contains current measuring transformer 1, voltage measuring transformer 2 installed at opposite ends of the line. To trans0

A current sequence filter 3 is connected to a current format 1, and a phase difference current difference and a zero sequence current are calculated in block 4. The output of the zero-sequence current filter is connected to the variable 4 for calculating the difference in phase current and zero-sequence current. The voltage transformer b is connected to the voltage transformer, and a zero-sequence voltage difference-voltage computing unit 6 is used. The output of the zero sequence voltage filter 5 is connected to Olok b for calculating the difference in phase voltage and zero sequence voltage. The outputs of the current-voltage and voltage-difference calculation terminals are connected to the adder 7, which calculates the electromagnetic wave, and the IV accumulator / the outputs of the olok-a and Y outputs are calculated for the phase-to-phase wave of the other two phases of the line. The output of the high-frequency pulse packet generation unit 10 is connected to the electromagnetic wave calculation unit, and the transceiver 11 and the phase comparison unit 12 are connected to the outputs of the formation unit 10.

The mode of currents and voltages on the line under normal conditions, as well as during emergency and operational switches, can be represented by a set of forward and reverse electromagnetic waves traveling in opposite directions along the line:

l / + Z, i; (1)

W U- Zc /, (2)

where Zc is the characteristic impedance

V is a direct wave of electromagnetic

floor, W - reverse electromagnetic wave

dale,

Both the forward (V) and inverse (W) waves are linear functions of voltage and current, therefore, by measuring the voltage and current at any point, one can obtain, using (1) and (2), direct and reverse waves at this point.

In the transposed power lines, the current and the voltage are moissed into components a, p, 0. The component a is equal to the difference of the mode parameter of the phase A and the zero component. Then equations (1) and (2) for the α-component are rewritten as follows:

l / "(d /, - f / e) + Zc (ia- /); (3)

W .. (,) - Z, (,). (4)

The forward wave travels along the line in a positive direction at the speed of light, the opposite in the opposite direction at the same speed. Practically both waves are not distorted in lines x 500-

1150 kV. Therefore, measuring the waves at the ends of the section and transferring them to the opposite end (and the wave propagation speed along the line and the signal transmission speed are equal), and then comparing them with those measured at this end, they are judged on the presence or absence of a short circuit on the line. If the angle between the waves is zero (without taking into account the measurement error of the measuring equipment

the measuring unit of the device itself), then the short circuit is out of line, otherwise on the line. The measurement of the difference in phase shift by waves at the ends of the transmission line is the basis for the method of fixing a short circuit. In order for the protection to be more sensitive to phase-to-phase and short-circuits of other phases, to the values of V.J. and W- ,. interfacial waves K, V and, where t {is the coefficient of fate, the value of which is chosen so as to ensure maximum sensitivity of the protection. The coefficient of participation is determined by the type

protection: for phase protection and voters

damaged phases to protect against

all kinds of short circuit / (heaps

- (/ 0,6-; 0,8).

The operation of the device is as follows.

The current and voltage of the protected line from the current transformer 1 and the voltage transformer 2 are supplied to the zero sequence current filter 3, the zero sequence voltage filter 5, the phase current difference difference and the zero sequence current unit 6 and the phase voltage difference calculation block 6 and zero sequence.

The current and zero-sequence voltage released in the filters go to the units for calculating the difference, respectively, between currents and voltages. The difference currents generated in block 4 and the difference voltages produced in block 6, and the differences in the phase voltages and currents of the other two line phases from blocks 8 and 9, go to adder 7, in which the forward (reverse) value is calculated the waves.

This voltage, through the high-frequency pulse packet shaping unit 10, with a positive or negative half-wave value, is supplied to the transceiver 11 for transmission to the opposite

the end of the line to be protected and the phase comparison unit 12 with the signal formed by the voltage of the forward (reverse) wave at the opposite end of the line. If the phases do not match, the signals produced in

the place of installation of the protection and received from the opposite end of the protected line - fix a short circuit.

The use of the phase difference of two high-frequency signals, formed by direct and inverse tension.

waves as a sign of damage allows protection based on existing differential phase protection, but with a practically unlimited length of the protected line and not working falsely in the presence of longitudinal compensation devices in adjacent areas with the protected line.

Claims (2)

1. Popov I.N. On the use of transients and external sources of control for the implementation of relay protection devices. On Sat "Issues of optimal development of power systems and new technical means of their protection. M., “Science, 1970, p. 43-73. 2. Fedoseev, A. M. Relein, protection of electrical systems. M., “Energie, 1976, fig. 6-20. -, I NC .- i - 1 &-but 1L ..