JPS58175918A - Breaker control system - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a breaker control method when a no-current phenomenon occurs in a power system, and particularly to a method suitable for high-speed shutoff.

When a power system fault occurs, if the DC component in the fault 1lEfL exceeds the AC component, it will last for several cycles or more.
The zero point of WLft does not occur. In such a non-zero state, it is possible to mechanically open the circuit breaker, but electrically, arcing due to direct current continues, and there is a risk of damage to the circuit breaker. For this reason, in conventional breaking systems, when such a lack of current zero is detected, the circuit breaker is prevented from opening for the purpose of protecting the breaker, and once the current zero condition is eliminated, the blocking of the breaker from opening is released. was. In the case of this type of system, a shutdown command is issued to the circuit breaker as soon as the non-zero condition is resolved, which increases the shutdown time, causing the accident condition to continue for a long time and worsening system stability. was there.

In view of the above, an object of the present invention is to provide a method for determining the zero-time period that affects the circuit breaker based on the nature of the accident and minimizing the delay in the circuit breaker's shutoff time.

Analysis has revealed that the duration time of ttlft without zero in a power transmission line is the longest when two wires are shorted during phase-advanced operation, and that it is more likely to occur in the lagging phase (for example, C phase in the case of a BE short-circuit). In the present invention, as a method for resolving the zero failure at the time of a two-set accident, the various locations having the zero point of the fault phase are shut off, and then an opening command is given to the zero failure breaker.

As shown in FIG. 1, in a general power transmission system, power is supplied from a generator G to a system S via a transmission edge L1 transformer Tr. In the same figure, current transformers CTI and CT2 mutually transmit the current passing through CBI and CB2fr to transmission line C, and there is a fault F in the internal direction, that is, between CBI and CB2. If it is determined that
and issues a cutoff command to CB2 to eliminate the accident.

As mentioned above, the most severe case without zero is a two-wire accident during phase-leading operation, and the lagging phase on the power supply side has the longest zero-free time.

FIG. 2 shows the part of the power transmission line in FIG. 1 in more detail, and it is assumed that a beC phase line short circuit occurs at point F. At this time, the more the generator is in phase advance operation, the easier it is to avoid zero, and the C
Zero current is likely to occur in the phase.

The above non-zero phenomenon occurs because the generator has a leading power factor, so the transient DC component with the same value as the maximum AC component caused by the accident angle and the transient DC component determined by the pre-fault tide current overlap with the same sign. This is caused by

Figure 3 (i) + (b) e (c) u Breaker CBI of the fault phase that can be cut out among the four sets of circuit breakers in the event of a 2-line fault.

CB2. The combinations when CB3 is opened in this order are shown. This CBI, CB2. The time required for zeroless circuit breaker CB4 to open after opening CB3 is shown in Figure 3 (d).
). The horizontal axis in FIG. 3(d) represents the combination (a) of the opening order of the three circuit breakers.

(b) and (C) are shown. As shown in Figure ＠), when the two-phase breaker on the grid side opens at the fault point (case in Figure 11(a)), the delayed phase breaker CB4 on the generator 11 side opens. The time it takes to reach the zero point is CB1°CB2.
There are cases where it reaches CB3L or disconnection 2Qmsec.
There are problems with current circuit breakers. To keep this in mind, the present invention performs an AND operation on the conditions shown in Fig. 4, and only when all the conditions are satisfied, the relay's operation time is delayed by a predetermined period of time and a cutoff command is issued to the breaker. I have something to do. 4th line for each protective wire for each phase.
The logic of the diagram is added.

Of these, the pre-fault power factor can be calculated as the product of voltage and current. Maku,
The delayed phase of a two-phase short circuit can be detected by the method shown in FIG. 5 based on the operation results of high-speed relays, voltages, and currents.

However, it is only necessary to determine that the phase in which the accident is being detected is two-phase, and the lead/lag relationship for these two phases.

The determination of case (a) in FIG. 3 is made by the method shown in FIGS. 6 and 7. In other words, Figure 3 (1), (b)
.

Among the combinations of the shutdown order in (C), the breaker locking measure is adopted only for case (1) of the grid-side advance opening where no zero is a problem for a long time. The fIA6 diagram shows only the a-phase, and the output (II-1) of the a-phase accident detection relay and the current at are provided with slime levels L, , L, and detected at the nine zero point (
1-2). This value is obtained for each phase as shown in A, B, and C in FIG. 7, and the OR of these outputs is taken as D. Signals can only be obtained in the event of an accident. In the case of a two-phase short circuit, there are four sets of corresponding fault tjIL flows, but since there is no zero in a breaker without a zero, the zero points are numerous.

The order in which signals A, B, and C are obtained is determined from the first output of the signals obtained after this accident. When four sets of signals A, B, and C are obtained, it is a normal accident with a zero point.

In this case, the output of the logic circuit shown in FIG. 4 does not act on the protection relay device, and the system is maintained as in the conventional case. True signal A, B
Even when only three sets of , C are obtained, if the self phase is not a delayed phase due to a two-phase short circuit, a system maintenance output is given as in the conventional case. When the own phase is on the lagging side and only three sets of input signals A, B, and C are obtained, "C" in the figure is the slowest time at which the zero point occurs after the accident occurs, and "C" is the progress on the generator side. Phase (a)
In the case of phase) (when the ab phase is short-circuited), this corresponds to the case shown in FIG. Therefore, if the other two conditions shown in FIG. 4 are satisfied, a corresponding b-phase cutoff command is sent.

According to the present invention, it is determined that the system IIII2 phase is to be opened in advance according to the order in which the zero point pulses of each phase arrive, but in reality, the system is also opened in the order in which the zero point pulses arrive. In other words,
Assuming that the time from the breaker closing command to the opening of the mechanism is assumed to be uniform, the closing command will be at zero point and l according to the judgment in Figure 4.
This is due to the fact that they are given sequentially starting from what was given.

According to the present invention, with the addition of simple judgment as described above, destruction of a breaker can be prevented by extending the breaker time in special cases. Furthermore, since the cases in which the cutoff time of the circuit breaker is extended are limited, the effect on stability is much greater than in the case where the cutoff time is extended indiscriminately.

[Brief explanation of drawings]

Figure 1 is a system diagram that is the subject of this application, Figure 2 is a diagram showing the relationship between circuit breakers at both ends of the transmission line and the occurrence of zero zero, and Figure 3 is a diagram showing the relationship between the circuit breaker at both ends of the transmission line and the occurrence of zero zero. Diagram showing the time relationship of #! Figure 4 is a diagram showing conditions for delaying the cutoff time of a specific breaker, Figure 5 is a processing flow for detecting a delayed phase when two phases are shorted, and Figures 6 and 7 are:
FIG. 2 is a diagram showing a circuit for determining whether or not two-phase circuit breakers at the same location should be opened. 1Y...Protective relay device, CB...Cutoff switch agent Roshi Ii Akio Takao Case 7m

Claims (1)

[Claims] 1. Among the circuit breakers whose terminals had phase leading currents before the fault due to power generation, for circuit breakers that become lagging phase in the event of a two-wire fault, the point at which the current zero point of the faulty phase at the other end occurs is at its own end. t or breaker control method characterized by delaying the closing command to the breaker for a certain period of time earlier than the point of occurrence of the current zero point of other fault phases.