RU2227355C2 - Method prohibiting automatic cutting in of standby equipment for short-circuit across buses of two-transformer substation - Google Patents

Abstract

FIELD: automatics of electric networks. SUBSTANCE: invention is intended to prevent operation of substation switch of automatic cutting in of standby equipment for short-circuit across buses of two-transformer substation. Technical result consists in widening of application field of method by its use for prohibition of switching on of substation standby equipment for stable two- or three-phase short-circuit across substation buses in absence or presence of equipment of automatic re-cutting of input switch. Method consists in recording of indications of short-circuit currents, in recording of indication of short-circuit current at input of supply transformer, in control of current at input of supply transformer between input switch and automatic switch cutting in standby equipment, in recording of indication of short-circuit between input switch and automatic switch cutting in standby equipment. When it is cut out due to operation of protection line voltages across buses on side of supply transformer are controlled and in case of their absence conclusion is made that there exists stable short-circuit across substation buses between input switch and automatic switch cutting in standby equipment. In this case signal for prohibition of automatic cutting in of standby equipment is sent. EFFECT: widened application field of method. 2 dwg

Description

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

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 count, then the signal to prohibit the operation of the switch of the substation ABP. [1]

The disadvantage of this method is its reliability is not high enough and, in addition, its inapplicability for the implementation of the prohibition of ATS on a stable short circuit on the substation tires in the absence of an automatic reclosure device for an 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 known method, which consists in fixing the occurrence of short-circuit currents and measuring the time between them, the appearance of a short-circuit current at the input of the transformer is recorded, when it is turned off due to the operation of the protection, the dead time pause time of the automatic reclosure of the input switch starts, and if when the countdown ends, the short circuit current appears again, then a signal is issued to prohibit the operation of the substation ABP switch, according to the invention, the current at the input is controlled of its transformer between the input switch and the ABP switch, the appearance of a short circuit current between the input switch and the ABP switch is detected, when it is disconnected due to the operation of the protection, the line voltages on the buses from the supply transformer are monitored, and if they are absent, they signal to prohibit operation 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 supply transformer T 1, an input switch BB 2, an ABP 3 switch, a current sensor DT 4, a short-circuit current sensor DTKZ 5, element Memory 6, element NOT 7, element AND 8, element Memory 9 , the voltage presence sensor DNN 10, the voltage presence sensor DNN 11, the voltage presence sensor DNN 12, element 13, element I - NOT 14, short circuit point 15.

With a short circuit at point 15 (see FIG. 1), the signal diagrams at the outputs of the elements shown in FIG. 1 have the form: 16 — at the output of element 4; 17 - at the output of element 5; 18 - at the output of element 10; 19 - at the output of element 11; 20 - at the output of element 12; 21 - at the output of element 6; 22 - at the output of element 7; 23 - at the output of element 13; 24 - at the output of element 14; 25 - at the output of element 8; 26 - at the output of element 9.

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 sensor DT 4. Since the current is not equal to or greater than the short circuit current, there is no signal at the output of the DTKZ 5 and, accordingly, at the output of the Memory 6, there is no signal at the output of the AND element - NOT 14, since all linear voltages on the buses are present. And that means there is no signal at the output of element And 8 (figure 2, diagram 25). Therefore, the circuit does not start.

In the event of a short circuit (two- or three-phase) (in the diagram, see Fig. 2, the case of a two-phase fault is shown), a short-circuit current appears on the busbar section of the substation located between the input switch and the ABP switch (Fig. 1, point 15), which is detected by the DTKZ 5 sensor, a signal appears at the DTKZ 5 output (Fig. 2, diagram 17). The signal disappears at the output of the element NOT 7 (figure 2, diagram 22). There is a signal at the output of the element Memory 6 (Fig. 2, diagram 21) and will be applied to one of the inputs of element And 8. Since a short circuit occurred on the buses, when a two-phase circuit occurs, one of the line voltages becomes equal to zero, therefore, the signal disappears from one of the sensors of the presence of voltage, in the diagram it is NAM 10 (Fig. 2, diagram 18). In view of this, the signal from the element And 13 will disappear (figure 2, diagram 23) and a signal will appear at the output of the element AND - NOT 14 (figure 2, diagram 24), which is fed to one of the inputs of the element And 8. After the protection is switched off, the short-circuit current the circuit will disappear the signals at the outputs of the elements DTKZ 5, DNN 11, DNN 12, a signal appears at the output of the element NOT 7 and is fed to one of the inputs of the element And 8 (figure 2, diagram 22). There will also be signals from the elements Memory 6 and AND - NOT 14 (Fig.2, diagrams 21 and 24, respectively). The presence of signals at all inputs of the element And 8 leads to the appearance of a signal at its output (figure 2, diagram 25). This signal is stored by the element Memory 9 (figure 2, diagram 26) and is a signal to prohibit ATS.

With a three-phase short circuit, the signals from the elements of the DNN 10, DNN 11 and DNN 12 will disappear simultaneously when a short circuit current occurs. Otherwise, the operation of the circuit will not change.

When normal mode is restored, all linear voltages appear, which means that signals appear at the outputs of the elements ДНН 10 (Fig.2, diagram 18), ДНН 11 (Fig.2, diagram 19), ДНН 12 (Fig.2, diagram 20). As a result, a signal appears at the output of element And 13 (figure 2, diagram 23), which resets information from the elements Memory 6 (figure 2, diagram 21), Memory 9 (figure 2, diagram 26), the signal disappears from the element And - NOT 14, which brings the circuit to its original state.

If a short circuit does not occur on the substation tires between the input circuit breaker and the ABP switch, but is assumed in one of the outgoing lines, then after switching off the short circuit current by the protection of this line, all line voltage on the buses will reappear (and if the short circuit occurred at a point on the line remote from the bus , then they will be present in the presence of a short circuit current), therefore, a signal appears at the output of the And 13 element and disappears (or does not appear) at the AND output - NOT 14. The signal from And 13 will reset the Memory 6 element. 3 There will be no signals from AND elements - NOT 14 and Memory 6 at the inputs of AND 8 element, and therefore, ABP will not be prohibited.

If the line voltages on the buses disappear due to other reasons (for example, operational switching, failure of the supply transformer, etc.), then there will be no signals from the DTKZ element 5, that is, there will be no signal at the output of the Memory 6 element and will not go to the input of the And element 8, therefore, the ATS prohibition signal will not be issued.

If the input switch is equipped with an automatic reclosure device, then after its operation, with a steady short circuit on the buses, the input switch will again be switched off by the protection and, accordingly, the voltage on the tires will be equal to zero. This means that the situation will be similar to the case without AR 10 BB (there was a short circuit current, and after disconnecting it there are no line voltages on the buses between the input switch and the ATS switch), and, therefore, an ATS ban will be issued. In the event of an unstable short circuit after the automatic recirculation of the explosive 10, line voltages will appear on the buses and a ban will not be issued.

Thus, the signal to prohibit turning on the switch of a substation ABP is given only in the case of a short circuit on the substation buses between the input switch and the ABP switch, 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 No. 2173017, cl. H 02 J 9/06 from 01.03.2000 - prototype.

Claims (1)

A method of prohibiting automatic switching on of the reserve (ATS) to a short circuit on the buses of a two-transformer substation, which consists in fixing the appearance of a short circuit current at the input of the supply transformer, characterized in that they control the current at the input of the supply transformer between the input switch and the ATS switch, fix the appearance of a short circuit current between the input switch and the ABP switch, when it is disconnected due to the operation of the protection, the line voltage on the buses is monitored by if it is absent, and if they are absent, then conclude that there was a steady short circuit on the substation buses between the input switch and the ATS switch, and in this case an ATS prohibition signal is sent.

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