RU2251193C1 - Method for inhibiting automatic load transfer on occurrence of short circuit across bused of double-transformer substation - Google Patents

Abstract

FIELD: automatic control of power networks.

SUBSTANCE: proposed method designed to inhibit automatic load transfer on occurrence of short circuit across substation buses includes recording of short-circuit current at power transformer bushing between bushing circuit breaker and automatic transfer switch, check-up of short-circuit current in outgoing lines, check-up of voltage across power transformer bus section, and generation of automatic transfer inhibit signal upon disconnection of short-circuit current by protective gear if short-circuit current is detected at power transformer bushing and not found in outgoing lines, provided transformer bus section is deenergized.

EFFECT: enlarged functional capabilities due to inhibiting load transfer on occurrence of shorts across substation buses.

1 cl, 3 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 countdown, then a signal to prohibit operation of a switch of a substation ABP [1]

The disadvantage of this method is its insufficient reliability and functionality, so this method is applicable only for three-phase short circuits on the substation buses in the presence of an automatic reclosure input circuit breaker.

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

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 protection being triggered, the time for a dead time pause of the automatic reclosure of the input switch and if at the end of the count, the short-circuit current appears again, then a signal is issued to prohibit the operation of the ABP switch, according to the invention, the short-circuit current is recorded at the input of its transformer between the input switch and the ABP switch, fix the short circuit current in the outgoing lines (feeders), control the voltage on the busbar sections of the supply transformer and, if the short circuit current is present at the input of the supply transformer, but is absent in the outgoing lines, then after the current protection is turned off short circuit, if there is no voltage on the busbar sections of the supply transformer, a signal to prohibit the ATS.

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 with a short circuit at point 16;

figure 3 shows a diagram of the signals at the outputs of the elements shown in figure 1 with a short circuit at point 17.

The circuit (see Fig. 1) contains a supply transformer T1, an input switch Q2 on the high voltage side, an input switch Q3 on the low voltage side, an ABP switch Q4, a switch in the outgoing line Q5, a switch in the outgoing line Q6, a switch in the outgoing line Q7 , DTKZ 8 short-circuit current sensor, DTKZ 9 short-circuit current sensor, DTKZ 10 short-circuit current sensor, DTKZ 11 short-circuit current sensor, OR-NOT 12 element, AND 13 element, Repeater 14 element, Memory 15 element, short circuit point 16, point short of circuit 17, presence sensor 18 DNN voltage.

With a short circuit (short circuit) at point 16 (see FIG. 1), the signal diagrams at the outputs of the elements shown in FIG. 1 have the form: 19 — at the output of element 8; 20 - at the output of element 9; 21 - at the output of element 10; 22 - at the output of element 11; 23 - at the output of element 12; 24 - at the output of element 13; 25 - at the output of element 14; 26 - at the output of element 18; 27 - at the output of element 15.

With a short circuit at point 17 (see FIG. 1), the signal diagrams at the outputs of the elements shown in FIG. 1 have the form: 28 — at the output of element 8; 29 - at the output of element 9; 30 - at the output of element 10; 31 - at the output of element 11; 32 - at the output of element 12; 33 - at the output of element 13; 34 - at the output of element 14; 35 - at the output of element 18; 36 - at the output of element 15.

The scheme works as follows.

In normal operation, the operating current flows in the outgoing lines and at the input of the transformer T1. Since the currents in the lines and at the input are not equal to the short circuit current, there are no signals at the outputs of DTKZ 8, DTKZ 9, DTKZ 10. Accordingly, there is a signal at the output of the OR-NOT 12 element, but since there is no signal from the DTKZ 11 element, then there is no signal at the output of AND element 13. All line voltages on the buses are present, therefore, there is a signal from the DNN18 element, which is sent to reset the Memory 15. element. 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 16), a short circuit current appears at the input of the transformer T1, which is detected by the DTKZ 11 sensor, a signal appears at the DTKZ 11 output ( figure 2, chart 22). Since the circuit occurred on the tires, then at the outputs of the sensors DTKZ 8, DTKZ 9 and DTKZ 10 there is no signal (Fig. 2, diagrams 19, 20, 21). As a result, the signal from the OR-NOT 12 element is supplied to one of the inputs of the And 13 element, at the second input of which there is a signal from DTKZ 11. At the And 13 output, a signal appears and is fed to the input of the Repeater 14 element (Fig. 2, diagram 24), which sends a signal to the input Memory 15 (figure 2, diagram 25). With the disappearance of voltage on the tires due to short circuit and turning it off with an input switch Q3, the signal from the NAM element 18 disappears (Fig. 2, diagram 26). Due to the presence of a signal at the input of the Memory 15 element and the absence of a reset signal, a signal will appear at the output of Memory 15, which will be a signal to prohibit the substation ATS (Fig. 2, diagram 27). When normal mode is restored, the voltage appears on the substation buses, which will be detected by the DNN 18 sensor, the signal from which will reset the Memory 15 element, the circuit will return to its original state.

In case of a short circuit (two or three phase) in the outgoing line (Fig. 1, point 17), its appearance is detected by short-circuit current sensors. in the line and at the input T1, it is DTKZ 8 and DTKZ 11, a signal appears at their outputs (Fig. 3, diagrams 28 and 31, respectively). As a result, the signal disappears from the OR-NOT 12 element, and therefore the signal disappears at one of the inputs of the And 13 element (Fig. 3, diagram 32), at the second input of which there is a signal from DTKZ 11. At the And 13 output, the signal will not appear and therefore will not will be fed to the input of the Repeater element 14 (figure 3, diagram 33). So there is no signal at the input of Memory 15 (Fig.3, diagram 34). Accordingly, the ATS prohibition signal will not be issued. After disconnecting the short circuit current switch Q5 will disappear signals from the sensors DTKZ 8 and DTKZ 11 (figure 3, diagrams 28 and 31, respectively), the circuit will return to its original state.

Thus, the ATS prohibition signal is given only in case of a short circuit on the substation buses between the input switch and the ATS switch, regardless of the type of short circuit (two or three phase). 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 1.03.2000 - 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 fix the short circuit current at the input of the supply transformer between the input switch and the ABP switch, in the same the instant of time is monitored for the short circuit current in the outgoing lines, the voltage across the busbar sections of the supply transformer is monitored, and if there is a short circuit current uet on input supply transformer but absent in the outgoing lines, after tripping fault current protection in the absence of voltage at the supply transformer section tire conclude that a short circuit on the tires two-transformer substation in which case the inhibiting signal supplied ABP.

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