SU1647739A1 - Device for selecting faulty phase of three-phase transmission line - Google Patents

Abstract

The invention relates to electrical engineering, in particular, to relay protection and automatic line, and can be used in single-phase automatic reclosing devices (OAPV). The aim of the invention is to enhance the functionality by providing line protection in a PELV loop. The principle of operation of the device is based on isolating the emergency components of the linear currents in block 4, forming the modules of these currents by the formers 5-7, forming the summers 11-13 of the sums of the modules of the emergency components of the two linear currents from the three, and then comparing the 8 to 10 absolute values of the indicated the sum of the emergency components of the two currents with the emergency component of the third current. If one or both of the disconnected phases in the OAPV cycle fails, the corresponding elements of the absolute values are triggered, and the three-phase disconnecting unit 18 generates a signal to disconnect the three phases, provided that one of the inputs of the first element And 19 receives the Fixed-input signaling signal of the OAPV from terminals 20, 1 silt yo

Description

The invention relates to electrical engineering, in particular, to relay protection and linear automation, and can be used in single-phase automatic reclosing devices (OAPV).

The aim of the invention is to enhance the functional capabilities by providing line protection in a PELV loop.

The drawing shows a functional diagram of the proposed device.

The device contains measuring transducers of 1-3 phase currents, the outputs of which are connected to the inputs of the block 4 for the allocation of emergency components of linear currents, the first 5, the second 6 and the third 7

module drivers connected by inputs to outputs of block 4 for isolating emergency components of linear currents and outputs for corresponding inputs of the first 8. second 9 and third 10 absolute value comparison elements, as well as first 11, second 12 and third 13 adders, elements 14 - The 16 memory, the inputs to the outputs of the corresponding elements 8-10 of the absolute value comparison, and the outputs to the inputs of the first element OR 17 and to the inputs of the three-phase disconnecting unit 18, the output of which is connected to one input of the first element And 19, Another input to the terminal

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vj VI SO H

20 in the signal circuit of the Fixation of the start of the auto-reclosing circuit, to which the input of the element HE 21 is also connected, connected to one input of the second element AND 22, to the other input of which the output of the first element OR 17 is connected, the second element OR 23 connected by one input to the output of block 18 three-phase disconnection, by another input to the output of the second element I 22, and the output through the delay element 24 to the control inputs of the memory elements 14-16.

The conditions for selecting the damaged phases A, B, and C, respectively, implemented in the elements of comparison, 8-10 absolute values have the form

KA (+ liflcbAl) / lltcl K; (1) KB (1 Pfo I + I iaЈc П / 11асд I ж; (2)

Kc (HtcHliacAD / liaABt K, (3) where K 1,2 ... 1,4 is the pickup setting.

Since the emergency components at the outputs of block 4 exist only during the time of their release (20-40 ms), memory elements 14-16 are provided in the device, which ensure that the name of the damaged phase is memorized (with a single-phase short-circuit to ground) after the emergency components disappear. In the three-phase disconnecting unit 18, a logical function of the type U XA (Xv + Xc) + Xv-Xc is implemented, (4)

where Y, XA, XB, Xc - output and input signals of block 18, respectively.

Thus, the signal at the output of block 18 appears when there are signals at any two or all three of its inputs.

The device works as follows

In the normal network operation mode, the alarm components at the outputs of block 4 are zero (if the unbalance is ignored) and there are no signals at the device outputs.

In the event of a fault in the network at the outputs of block 4, an emergency contingency occurs. values depending on the type of damage. The table shows the values of the coefficients Kj (jA, B, C) for various types of short circuits, computational in accordance with expressions (1) - (3) assuming that the resistances of the forward and backward sequences of network elements are equal.

In single-phase short-circuit and two-phase short-circuit and three-phase short-circuit conditions, the coefficients Kj (jA, B, C) do not depend on the position of the short-circuit point and the transition resistance at the fault site and are equal to the values indicated in the table.

In the two-phase short circuit to earth mode, the value of K depends on the ratio ZoK / (ZtK + + ZQK), where Z, IK, 2pk are equivalent resistances of the direct and zero sequence replacement circuits relative to the short-circuit point.

For a reactive network replacement circuit, provided that the transient resistances in the phases (Rn Φ 0) are neglected and taking into account only the general transient resistance (ground resistance R3), we have

& K 3R3 + JX0K ZJK + ZOK 3R3-H (Xt) K + XiK) n + jm

n + j (m +1)

(five)

Where

n 3R3 / XiK; m XQK / XIK. (6) The parameter m may in general

vary from 0.3 to 3.5. In the table, the values of the coefficients Kj are given for the two worst cases: a) m R3 0 (n 0); b) m 0.3, n Vm (m + 1) 0.6245.

With an increase in the parameter m, the value of the coefficient Kj for intact (A) and damaged (B and C) phases will tend to 1 and 3, respectively (as for a two-phase short circuit without earth).

Thus, in accordance with conditions (1) - (3) and the data in the table, depending on the type of short-circuit, one (with a single-phase short-circuit to earth), two (with a two-phase short circuit without ground) or three (with a three-phase short-circuit) elements 8-10 compares absolute values, resulting in the appearance at the outputs of the corresponding elements 14-16 of the signal memory indicating the name of the damaged phases.

in the two-phase short-circuit to earth mode, the device may indicate either damage to two closed phases (for large values of m) or damage to all three phases. However, this does not affect operation.

devices, as in case of multiphase faults (two-phase and three-phase), in accordance with condition (4), a signal appears at the output of block 18 and a circuit is prepared for switching off the three phases of the line, closing at

line protection tripping (occurrence of the signal of the start of the automatic isolation circuit is detected).

When a single-phase fault is disconnected (including cascade), the K coefficients have values similar to the closure mode

this phase to earth (see table), i.e. in this mode, the reference element in the switched phase will be triggered. Triggering of the specified element does not change the output signals of the device, since

The output of the corresponding memory element is formed even in the single-phase short-circuit mode to the ground.

When a single phase (A) closes into a two phase closure (A and B) to earth, an absolute value comparison element is triggered in a newly closed phase (B) and a signal is output at the output of the corresponding memory element. This signal, in combination with the previously formed signal (in phase A), causes the signal to appear at the output of block 18. This prepares a three-phase line disconnect circuit that closes when the line protection is triggered.

If one or both of the disconnected phases are damaged in the OAPV cycle, the comparison elements in these phases are triggered and a signal is generated to turn off the three phases.

During multiphase faults, when single-phase faults are transformed into two-phase faults to earth, and also when damage occurs on disconnected phases in the OAPV cycle, a signal from the output of the three-phase tripping unit 18 passing through the second OR 23 element and delay element 24 resets the output signals elements 14-16 of memory. A similar reset occurs upon successful completion of the OAPV cycle (successful activation of the damaged phase), when the OAPV4 Start release signal disappears, as well as when an external single-phase short circuit occurs during a specified time, and is determined by the delay element 24, after selecting the damaged phase, not line protection is triggered (there is no signal for fixing the start of the automatic network.

Claims (1)

Apparatus of the Invention A device for selecting a faulty phase of a three-phase transmission line, comprising phase current measuring transducers by the number of line phases, connecting other i outputs to the inputs of the emergency current component extraction unit, the first, second and third elements of the absolute value comparison, the output of each of which connected to the main input of the corresponding memory element, as well as the first and second elements of AND, for example, with the aim of expanding the functionality by providing protection to In the single-phase automatic reclosing 5 (OAPV) cycle, the first, second and third module drivers, the first, second and third adders, the three-phase disconnecting unit, the first and second OR elements, the NOT element and the 10-second element, and the emergency current component extraction unit is made in the form of an emergency current separation unit, the first, second and third outputs of the emergency unit 5 components of linear currents are connected to the inputs of the first, second and third module drivers, respectively, the output of the first module driver is connected to one input of the first element of the comparison 0 absolute values, as well as to one input of the first and third adders, the output of the second generator module is connected to one input of the second element of the comparison of absolute values, to the other input of the first 5 accumulator and to one input of the second adder, the output of the third generator module is connected to one input of the third element comparing absolute values as well as to other inputs of the second and third 0 adders connected by outputs to other inputs of the first and second absolute value comparison elements, respectively, the output of the first adder is connected to another input of the third element 5 comparisons of absolute values, the outputs of all three memory elements are connected to the inputs of the first OR element, as well as to the inputs of a three-phase disconnection unit connected by an output to one input of the second OR element, as well as to one input of the first AND element, the other input of which is connected to the terminal in the signal circuit of the LCPA start-up start signal, to which is also connected the input of the element NOT connected 5 output to one input of the second element AND, to the other input of which the output of the first element OR is connected, and the output of the second element AND connected to another input of the second OR element connected 0 output through the delay element to the control inputs of all the memory elements. 3 0 V I drove to turn off FWE drove Start-up fixation ol