SU1374324A1 - Apparatus for locating faulty phases in three-phase a.c.mains - Google Patents

Abstract

This invention relates to electrical engineering, in particular, to relay protection. The purpose of the invention is to improve the reliability of operation of the device by determining the type of short circuit. The device contains converters 4-6 connected to measuring inputs 1-3, a phase current compensation unit (BCFT) 7, emergency components allocation units (BVAS) 8-10, blocks forming modules of emergency components, (BFMAS) 11-13, logical keys 14-16, comparators 17-22 and block of determining the type of short circuit (BOVKZ) 23. With short-circuit the instantaneous value of electrical quantities at the outputs of converters 4-6 and the output of BCFT 7 changes is abrupt, and at the output of bv C 8-10 some time this signal is stored. Further in BFMAS 11-13, napa- DC power, the value of which is proportional to the values of the corresponding emergency component currents. The voltage from the Bda1AC outputs 11-13 through the open logic switches 14-16 enters the inputs of the comparators 17-22, the outputs of which form a voltage corresponding to the type of short-circuit that enters the BOVKZ 23. 2 ip. (L

Description

- @ at-J

The invention relates to electrical engineering and can be used for relay protection.

The purpose of the invention is to increase the reliability of the operation of the device by determining the type of short lock (CZ).

Figure 1 shows the structural diagram of the proposed device; Fig. 2 shows the signs of the voltages at the outputs of the device comparators for various types of single-phase and two-phase faults,

The device contains measuring inputs of 1-3 phase currents and phase converters of 4-6 phase currents connected to them phase by phase, the outputs of which are connected to block 7 for compensation of phase currents by zero-sequence current. The outputs of block 7 are connected in phase to the inputs of blocks 8-10 of the emergency components, the outputs of which are connected to the inputs of blocks 11-13 of forming emergency components modules, respectively, the outputs of which are phase-connected via logic switches 14-16 to the inputs of comparators 17-22, The output of block 11 through the key 14 is connected to the first inputs of the first 17 and fourth 20 comparators and to the second inputs of the second. 18 and sixth 22 comparators. The output of block 12 through the key 15 is connected to the first inputs of the second 18 and the fifth 21 comparators and to the second inputs of the third 19 and fourth 20 comparators. The output of block 13 through the key 16 is connected to the first inputs of the third 19 and sixth 22 comparators and to the second inputs of the first 17 and fifth 21 comparators.

The outputs of the comparators 17-22 are connected to the inputs of the logic unit 23 for determining the type of short-circuit; phase 24-26 and interphase 27-29 outputs of which are the outputs of the device,

The phase outputs 24-26 through the first inputs of the OR elements 30-32 respectively are connected to the control inputs of the keys 14-16. The second inputs 33-35 of the indicated elements OR are the logical inputs of the device. The inputs from the corresponding switches are connected to these inputs phase switches of the protected power line (not shown).

Transmitters of 4-6 phase currents provide a voltage at their outputs that is proportional to the phase currents in the whole range of them.

five

0

five

0

five

0

0

five

change. In block 7, implemented in the form of a summing device, phase currents 1 are compensated by zero-sequence current ID, therefore voltage across the phase outputs of block 7 is proportional to the compensated phase currents I cR In accordance with the expression H 3-1o 7 provides for the possibility of adjusting the compensation coefficient k,

Blocks 8-10 of the emergency components are a well-known scheme in which its input voltage is summed with the output voltage of an inertial link connected to the input of this unit and made either as a half-wave delay line or as a bandpass filter. The inertial link is set up so that in the steady state industrial frequency the voltage at its output is equal in magnitude and opposite in phase to the input voltage, therefore when adding these voltages in steady state at the outputs of blocks 8-10, the signal is absent.

Blocks 11–13 are straighteners, with smoothing or integrating links.

Each of the logical keys 14-16 is open, i.e. passes the value connected to its inputs to the output as long as there is no signal at the control input of the key. When a signal appears at the control input of a key, the corresponding emergency component of the current is excluded from the operation of the device.

The signs of the voltages t., - U at the outputs of the comparators 17-22, respectively, are determined by the signs of the following differences: P. k-1; and „1„ - k-I,

BUT

with. VV k-I; U, Iggde 1d, 1 „, 1 U-I, - U, - k-I ,, ,,,. -A -B -c magnitude of phase emergency component currents; k is a constant coefficient.

The logic unit 23 for determining the type of short circuit is a combination of logical elements that, to implement certain logical functions with the signs of the signals U - at the outputs of the comparators 17-22, allow us to determine the type of short circuit. With single-phase faults, a signal appears at the corresponding phase outputs 24-26, and with two-phase faults, at the corresponding inter-phase outputs 27-29 of the logic unit 23 for determining the type of faults.

The device works as follows.

At short-circuit, the instantaneous value of the electrical quantities at the outputs is pre-determined and can be both positive and negative (Accounting for certain combinations of signs

and.and

those. the implementation of certain logical functions allows one to judge the form of a fault.

So, for fixing, for example, the closure of phase A to earth is sufficient

callers 4-6, as well as the output to implement the following logical

7 (i.e., at the inputs of blocks 8–10) changes in a jump-like manner, and the other (at the output of the inertial link), due to the storage properties of the inertial link, for some time, determined by the link parameters, retains a value proportional to the pre-emergency current. Thus, the sum of these two, for example, the function: At d and and and. and.

In this case, the output signal (Y.) Of the logic unit for determining the type of short-circuit appears (m: i.e., fixing 15 s for the closure of phase A to ground) if there are positive voltages U and U (for comparators 17 and 20) and no positive ones (or there are negative

is proportional to the corresponding jg) voltages and „and U (at the output 30

following functions:

 Y. Y - with

phase fault current component, in the short circuit mode, appears abruptly at the outputs of blocks 8-10 and is maintained for some time. In blocks 11-13, voltages are generated from c-25c: Y "of this current, the magnitudes of which are proportional to the values of the corresponding emergency currents. The voltages from the outputs of blocks 11–13 through the open logic switches 14–16 are fed to the inputs of comparators 17–22, at the outputs of which voltages are generated and - and corresponding to the type of short circuit.

In the case of single-phase faults to earth, the emergency component of the current of the damaged phase, as shown by studies for high and ultra high voltage networks, in the worst extreme conditions of sensitivity, is at least 1.2-1.3 times higher than the emergency components currents intact phases that are equal to each other.

With two-phase faults and two-phase earth faults, the emergency currents of the damaged phases, although in the general case they are not equal to each other, are also no less than k 1.2–1.3 times higher than the emergency component of the current of the intact phase.

The table in FIG. 2 shows the signs of the voltages at the outputs of the comparators 17-22 of the proposed device with various types of single-phase and two-phase short circuits. In this case, in the general case of two-phase short circuits, the sign of the output voltages of the comparators, to which signals from damaged phases are applied.

dah comparators 18 and 22).

Similarly, to determine other types of single-phase closures in the logic block, the following functions are implemented

one

5 - course 25 of block 23; Y

signal at output 26 of block 23.

To determine the two-phase closures in the logic block,

Y „

y + y j

e, hell ft e

V Y ,, Y ,, - Y, .Y.

In the general case for biphasic faults with

Taking into account the possibility of transition of single-phase short-circuit to two-phase short-circuit to earth in a logical block, the following functions are realized: at output 27 of block 23} Ygp Y + + Yg Yj. - the signal at the output 28 of the block 23; Y,

Y + A.

 -SA AND VYHO .- de 29 blocks 23. 4i

In the case of an incomplete phase network mode, when one of the phases of the power line, for example, phase A, is disconnected from the position relay, the disconnected phase is disconnected to the logic input 33 of the device and consequently to the control input of the logical switch 14 through the OR element 30 a signal is received, as a result of which the influence on the operation of the device of the disconnected phase circuit is eliminated.

With short circuits on high and extra high voltage power lines, including single-phase short circuit transitions to two-phase short circuits to earth, intense and long-term transients may occur in power lines, as well as in emergency phase separation circuits of 50

55

implement the following logical

function: At d and and and. and.

In this case, the signal at the output 24 (Y.) Of the logic block determining the type of short circuit appears (m: i.e. fixes with the closure of phase A to ground) in the case of positive voltages U and U (at the comparators 17 and 20) and there are no positive (or negative) voltages and "and U (output 0

following functions:

 Y. Y - with

5 cs: Y "

dah comparators 18 and 22).

Similarly, to determine other types of single-phase closures in the logic block, the following functions are implemented

one

5 - course 25 of block 23; Y

signal at output 26 of block 23.

To determine the two-phase closures in the logic block,

Y „

y + y j

e, hell ft e

V Y ,, Y ,, - Y, .Y.

In the general case for biphasic faults with

5 cs: Y "

Taking into account the possibility of transition of single-phase short-circuit to two-phase short-circuit to earth in a logical block, the following functions are realized: at output 27 of block 23} Ygp Y + + Yg Yj. - the signal at the output 28 of the block 23; Y,

Y + A.

 -SA AND VYHO .- de 29 blocks 23. 4i

In the case of an incomplete phase network mode, when one of the phases of the power line, for example, phase A, is disconnected from the position relay, the disconnected phase is disconnected to the logic input 33 of the device and consequently to the control input of the logical switch 14 through the OR element 30 a signal is received, as a result of which the influence on the operation of the device of the disconnected phase circuit is eliminated.

With short circuits on high and extra high voltage power lines, including single-phase short circuit transitions to two-phase short circuits to earth, intense and long-term transients may occur in power lines, as well as in emergency phase separation circuits.

five

current of the proposed device. Such transients in the release circuit of the emergency unit, its first damaged phase, which is detected by the appearance of a signal at the output 24 (e) of unit 23, could lead either to an incorrect determination of the last closed phase, or to

a slowdown in determining this phase, Q comparators and a logical block, therefore, the influence of the transition process in the circuit of the first damaged phase A is eliminated by the operation of the device by the logical key 14, the control input of which in this case receives a signal through the second input of the element OR 30 from the output 24 (Y) of block 23. Thus, the proposed device, on the basis of comparing the magnitudes of emergency components of phase currents, allows, without using complex FSK blocks, only to detect one damage on the basis of logical operations ennuyu phase at x of single phase circuit, two phase damaged when other types of asymmetric faults as well as functioning correctly when unbalance and transition of some species other damage.

Claims (1)

Invention Formula A device for selecting faulty fades in a three-phase AC mains with breakers, containing measuring converters of faults currents, the outputs of which through a common compensation unit are connected in phases to serially connected emergency release units and components for forming an emergency component module, and three comparators, characterized in that, in order to increase the reliability of operation by determining the short circuit type NIN, it additionally contains three keys, three OR elements, a quarter, five, and two 0 five 0 five determining the type of short circuit, while the output of the module forming the emergency component module of the first phase is connected via a key to the first inputs of the first and fourth comparators and to the second inputs of the second and sixth comparators; the output of the forming module of the module of the second phase is connected to the first the inputs of the second and fifth comparators and to the second inputs of the third and fourth comparators, the output of the block forming the emergency component module of the third phase is connected via a key to the first inputs of the third and the sixth comparators and to the second inputs of the first and fifth comparators, the outputs of the comparators are connected to the inputs of the logic unit for determining the type of short circuit, the phase outputs of which through the first inputs of the OR Elements are connected to the control of u1; 1, by their key inputs of the corresponding phase, to the second inputs the elements OR are connected to the outputs of the position relay. The corresponding phase switch is disconnected, and the phase and phase outputs of the short-circuit logic determining block are simultaneously the outputs of the device. Cs4