RU2218647C2 - Method for inhibiting automatic load transfer in response to short circuit at substation buses - Google Patents

Abstract

FIELD: automatic protection of power lines against substation circuit breaker operation in response to shorted buses. SUBSTANCE: proposed method used for inhibiting closure of automatic load transfer center in response to steady double- or three-phase short circuit at substation buses in absence or presence of automatic reclosing device for lead-in circuit breaker includes recording of short-circuit current through power transformer bushing at the same time checking operating current through power transformer bushing between lead-in circuit breaker and automatic load transfer circuit breaker; recording of short-circuit current between lead-in circuit breaker and automatic load transfer circuit breaker upon its opening due to operation of protective gear; measurement of working current between lead-in circuit breaker and automatic load transfer breaker; if it equals zero, conclusion is made that steady short circuit has occurred at substation buses between lead-in circuit breaker and automatic load transfer circuit breaker in which case automatic load transfer inhibit signal is sent. EFFECT: enlarged functional capabilities and fields of application. 1 cl, 2 dwg

Description

 The invention relates to the automation of electrical networks and is intended to prevent the operation of the switch of the substation automatic switch on reserve (ATS) for a short circuit on the substation tires.

 A known method of prohibiting substation automatic turning on of the reserve, in which the short-circuit current is recorded at the input of the supply transformer, after its disappearance, the time of a non-current pause of the automatic restart (AR) of the input switch is counted, and if the short-circuit current appears again at the end of the countdown, then a signal to prohibit operation of the substation ABP switch [1].

 The disadvantage of this method is its lack of reliability and, in addition, its inapplicability for the implementation of the ban ATS on a stable short circuit on the substation tires in the absence of an automatic reclosure device of the input switch. Also, this method is not sufficiently functional, since it is applicable only for three-phase short circuits on substation buses.

 The objective of the invention is to expand the scope and functionality of the method by using it to prohibit the inclusion of an ABP point on a stable two- or three-phase short circuit on the substation buses in the absence or presence of an automatic reclosure device of an input switch.

 To solve this problem, in a method consisting in fixing the occurrence of short-circuit currents and measuring the time between them, when all three line voltages disappear, the appearance of a short-circuit current at the input of the transformer is recorded, when it is turned off due to the protection being activated, the countdown time of the automatic reclosure input circuit breaker and if at the end of the counting the short circuit current appears again, a signal is issued to prohibit the operation of the circuit breaker of the substation ABP, according to the invention In June they control the operating current at the input of the supply transformer between the input switch and the ABP switch, record the appearance of a short circuit current between the input switch and the ABP switch, when it is turned off due to the operation of the protection, measure the current at the same point and, if it is zero, give a signal to prohibit the operation of the switch of substation ABP.

The essence of the invention is illustrated by drawings, where:
figure 1 shows a structural diagram of a device that implements the method,
figure 2 shows a diagram of the signals at the outputs of the elements shown in figure 1.

 The circuit (see Fig. 1) contains a current sensor DT 1, an operating current sensor DRT 2, an element NOT 3, a short-circuit current sensor DTKZ 4, an element Memory 5, an element NOT 6, an element And 7, an element Memory 8, a supply transformer T 9, input switch BB 10, switch ABP 11, short circuit point 12.

 With a short circuit at point 12 (see FIG. 1), the signal diagrams at the outputs of the elements shown in FIG. 1 have the form: 13 — at the output of element 1; 14 - at the output of element 2; 15 - at the output of element 3; 16 - at the output of element 4; 17 - at the output of element 5; 18 - at the output of element 6; 19 - at the output of element 7; 20 - at the output of element 8.

 The scheme works as follows.

 In the normal mode of operation of the line, a working current of some magnitude flows, which is controlled by the current sensors ДТ 1 and operating current ДРТ 2. There is no signal at the output of the element NOT 3, and since the current is not equal to and no more than the short circuit current, there is no signal at the output of DTKZ 4 and, accordingly, at the output of the Memory element 5, which means that there is no signal at the output of the And 7 element (Fig. 2, diagram 19). Therefore, the circuit does not start.

 In case of a short circuit (two- or three-phase) in the busbar section of the substation located between the input switch and the ABP switch (Fig. 1, point 12), a short-circuit current appears, which is detected by DTKZ 4, a signal appears at the output of DTKZ 4 (Fig. 2, diagram 16). The signal disappears at the output of the element NOT 6 (figure 2, diagram 18). The signal at the output of the DRT 2 disappears (since a short circuit current, which is larger than the working one, flows) (Fig. 2, diagram 14), therefore, a signal appears at the output of the element NOT 3 (Fig. 2, diagram 15), which is also fed to one from the inputs of the element And 7 will be present there after disconnecting the short-circuit current by the protection, if the operating current is equal to zero. A signal appears at the output of the Memory 5 element (Fig. 2, diagram 15). After turning off the protection of the short circuit current, a signal appears at the output of the element NOT 6 and is fed to one of the inputs of the element And 7 (figure 2, diagram 18). The presence of signals at all inputs of the element And 7 leads to the appearance of a signal at its output (figure 2, diagram 19). This signal is remembered by the element MEMORY 8 (figure 2, diagram 20) and is a signal to prohibit ATS.

 When the normal mode is restored, the operating current appears, which means that a signal appears at the output of the DRT 2 (figure 2, diagram 14). This signal resets information from the elements Memory 5 (Fig. 2, diagram 17), Memory 8 (Fig. 2, diagram 20), the signal from the element NOT 3 disappears, which brings the circuit to its original state.

 If a short circuit does not occur on the substation buses between the input switch and the ABP switch, but is supposed to be in one of the outgoing lines, then after switching off the short circuit current by the protection of this line, the operating current will reappear, therefore, a signal will appear at the output of DRT 2 and will disappear at the output of the element NOT 3. The signal from DRT 2 will reset the Memory element 5. Therefore, there will be no signals from these elements at the inputs of the And 7 element and, therefore, the ATS will not be disabled.

 If the operating current disappears due to other reasons (for example, operational switching, failure of the supply transformer, etc.), then there will be no signals from the DTKZ, that is, there will be no signal at the output of the Memory 5 element and will not be fed to the input of the And 7 element, therefore , ATS prohibition signal will not be issued.

 If the input switch is equipped with an automatic reclosure device, then after its operation, with a stable short circuit on the buses, the input switch will again be switched off by the protection and, accordingly, the operating current will be equal to zero. This means that the situation will be similar to the case without automatic reclosure BB 10 (there was a short circuit current, and after it is turned off, the working current is zero) and, therefore, an ATS ban will be issued. In the event of an unstable short circuit after the reclosure of the explosive 10, the operating current will appear and a ban will not be issued.

 Thus, the signal to prohibit turning on the switch of a substation ABP is given only in case of a short circuit on the substation buses between the input switch and the switch of the ABP, regardless of the type of short circuit (two- or three-phase) and the presence or absence of the automatic reclosure device of the input switch. This extends the scope and functionality of the method, which increases the service life of the circuit breaker, reduces the cost of its repair and maintenance.

Sourse of information
1. Patent 2173017, cl. H 02 J 9/06 - prototype.

Claims (1)

A method of prohibiting automatic turn-on of the reserve (ATS) for a short circuit on the substation buses, which consists in fixing the appearance of a short circuit current at the input of the supply transformer, characterized in that they control the working current at the input of the supply transformer between the input switch and the ATS switch, fix the appearance of the short circuit current between the input switch and the ABP switch, when it is turned off due to the operation of the protection, measure the operating current between the input switch and the ABP switch and if it is zero, then conclude that there was a steady short circuit on the substation buses and in this case an ABP inhibit signal is issued.

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