JPS59153420A - Defect current breaking 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] [Technical Field of the Invention] The present invention relates to a fault current interruption method, particularly when a grounding fault occurs in a power system, the current flowing through a power transmission line does not reach the current zero point or the vicinity of the zero point, and becomes positive or negative. The state remains unipolar (
This invention relates to a new fault current isolation method that eliminates fault current deviation (hereinafter referred to as current deviation) and eliminates fault current deviation (1/) and (2) using a disconnector. [Technical Background] When an accident occurs in a power system, the current that flows through the failure point and each phase of the power transmission line is generally a superimposition of alternating current and direct current. Figure 1 shows a typical current waveform flowing through the transmission line in the faulty section. In the figure, an accident occurs at time to, a command to disconnect is issued from the protective relay device to the breaker at time tl, and the current interruption is completed at t2.

However, depending on the operating conditions of the generator, power transmission system, etc., and the nature of the system fault, the transmission line current waveform immediately after a system fault may continue for several cycles without reaching the current zero point and remain unipolar. sell.

This aspect is shown in FIG.

On the other hand, the circuit breaker completes the circuit breaker when the DC reaches the zero point after the contacts are opened. By the way, since a breaker has a predetermined effective arc extinguishing time determined by its type, the current zero point must exist at least once during the effective arc extinguishing time in order to interrupt the current. Therefore, when a current deviation phenomenon as shown in Fig. 2 occurs, it is impossible to shut off the circuit in this state, and it becomes necessary to postpone the breaker trip command until just before the current reaches the zero point, and the system j (A-cross stability is not good.

The conditions for current deviation to occur are the system configuration, generator load condition,
Although it varies depending on the type of failure, as a result of examination, - line grounding,
Alternatively, it has recently been found that a very large 1E flow shift may occur in the non-fault phase of a two-wire grounding accident.

Figure 3 (,) is a general system diagram in which a generator 1 supplies power to a large power grid 4 through a power transmission line 3 through a step-up transformer 2 with a Y△ connection, and Figure 3 (b) is This is an equivalent circuit when a line ground fault occurs in the power transmission line 3.

In FIG. 3(b), the positive phase component if of the late NA current is equal to the negative phase component and the zero phase component. This current flows from the fault point to the generator, the system and the positive sequence impedances 5-1 and 5- of il+.
It is divided into 'llj flows shown by 8-1.8 to 2 in proportion to the reciprocal of 2. Similarly, in the negative phase circuit, the shunt current becomes 8-3.8-4 in inverse proportion to the negative phase impedance 6-1.6-2. In addition, in the zero-phase circuit, the shunt current 8-5 is inversely proportional to the zero-phase impedance 7-1.7-2.
．． It becomes 8-6. If the ratio of fault current division in the positive-phase, negative-phase, and zero-phase circuits is equal, the effect of the fault current due to single-wire grounding will not appear on the non-fault phase current. However, Fig. 3 (,
), when there is a Y△-connected step-up transformer 2, the zero-phase circuit is short-circuited by the short-circuit impedance of the transformer, and the zero-phase impedance 7-1 does not include the zero-phase impedance of the generator 1; It is smaller than the phase impedance 5-1 and the negative phase impedance 6-1. This tendency is remarkable when the failure point is close to the high voltage terminal of the transformer 2. On the other hand, since the zero-sequence impedance of the power transmission line 3 is p thicker than the positive-sequence and negative-sequence impedances, the grid-side zero-sequence impedance 7-2 is larger than the positive-sequence and negative-sequence impedances 5-2, 6-2. Therefore, among the fault currents, the zero-sequence current 8- flows from the fault point to the generator side.
5 may be considerably larger than the positive phase portion 8-1 and the negative phase portion 8-3. In such a case, the fault current may flow to the non-faulty phase, causing a zero current excursion in the non-faulty phase.

Generally, the current excursion in the faulty phase due to a ground fault is
In the system shown in Figure (a), this appears when the operating state of the generator 1 is extremely leading power factor operation, and since such operation is normally impossible, it hardly causes any problems. However, as mentioned above, if the number of zero-sequence current branches 8-5 on the generator side is larger than the positive and negative phase parts,
It has been found that during rated power factor operation with a lagging power factor, an extremely large current bias tL as shown in FIG. 2 appears in the non-faulty phase, which has become a problem.

Even in the case of a single-wire or two-wire grounding fault, if the proportion of the zero-sequence branch of the fault current is larger than the proportion of the positive-phase and negative-phase parts, as explained above, the generator 1 is delayed in power factor operation. In some cases, current deviation may occur in the non-faulty phase, which is a serious problem.

[Problems with weight technology]

This phenomenon has recently come into focus due to the increase in the size of sleep generators and the special operating conditions, and there are no known countermeasures in the prior art. As a general method, for example, acid 1jφ: Avoids leading power factor operation of the generator, which tends to cause a flow shift in the r phase, and performs strong excitation operation, but the above strong excitation operation This does not solve the problem of non-fault phase current deviations that sometimes occur. The reason for the non-fault phase current deviation at the time of a ground fault is that the zero-sequence impedance on the generator side is smaller than the positive-sequence and negative-sequence impedances, and the zero-sequence component of the fault current is large on the generator side. Therefore, a method has been proposed in which a zigzag-connected transformer is installed on the grid side to lower the zero-sequence impedance on the grid side and reduce the zero-sequence component of the fault current that is shunted to the generator side. Although this method is effective in reducing the current deviation occurring in the non-faulty phase, it is disadvantageous in terms of cost due to the addition of a zigzag connection transformer.

In addition, in the case of a - line grounding fault, conventionally called single-phase reclosing, the circuit breakers at both ends of the transmission line of only one failed phase are opened,
A method of disconnecting and reclosing for a certain period of time has been adopted, but as the voltage of power transmission lines increases, the arc at the fault point does not disappear while the - line is open, and this method cannot be applied. The number of cases in which phase isolation is required is increasing.

[Purpose of the invention]

The present invention has been made to solve the above-mentioned problems, and aims to provide a new fault current isolation method that can solve the current deviation that occurs at the time of a ground fault and effectively eliminate the fault section. It is said that

[Outline of the invention]

In the present invention, we focus on the fact that the first flow deviation that may occur in the non-faulty phase disappears by cutting off both ends of the transmission line of the faulty phase, and first, we cut off the circuit breakers at both ends of the faulty phase. After the ground fault has been removed, the attempt is made to cut off the non-fault phases.

[Embodiments of the invention]

Examples will be described below with reference to the drawings. FIG. 4 is a basic configuration diagram of the present invention and a system to which it is applied. power transmission line 3
breaker 9A-1'+ 9A-2 installed at both ends of
I
Shutoff is controlled by A and 11B. The open/closed state of the disconnectors 9A and 9B is determined by the information transmission devices 10A and 10B.
The information is immediately sent to the other party through the information transmission line 12,
The information is transmitted to the other party's cutoff selection control device], IA, ],
, input to IB.

FIG. 5 shows the detailed configuration of the cutoff selection control device 11A. Note that IIB also has a configuration based on the same principle as IIA, just by replacing the own end element and the opposite end element. In IIA, the tripping coil 14A-1 of the C-phase breaker 9-1 has the A-contact 13A-1a of the C-phase grounding fault detection relay, the self-end, the B-contact 9A-2b of the C-phase interrupter, 9A-3b
and the other end.

9B-2b corresponds to the C-phase breaker contact signal.

913-3bt-ri array, B contact 13-3b of C phase grounding fault detection relay, B contact of B phase own end and opposite end breaker, 9A-2b, 9B-2b are connected in series. , and b contact 13A-2 of the b-phase grounding fault detection relay.
B contact 9A-3b of B and C phase own end and opposite end breaker
, 9B-3b in series is excited by either one. In addition, the tripping coils 14A-2, 1 of the b-phase and C-phase
4A-3 is excited by a circuit in which the phase correspondence of each contact point in the case of the C phase is shifted.

Now, if a grounding fault occurs, regardless of whether it is 1-wire grounding, '1' or 2#J grounding, the faulty phase that has almost no current deviation problem under normal operating conditions will be detected by the a contact of the grounding fault detection relay 13 of each phase. Both the own end and the other end are cut off without delay. For example, in the case of C-phase grounding, the non-faulty single-wire grounded phase with a large possibility of current deviation is connected to the B-phase after the C-phase circuit breakers 9A'-1 and 9B-1 at both ends are cut off and the fault is removed. The breaker is 13A-3
b.

The tripping coil 14A-2 is energized through the contacts of 9A-1b and 9B-1b, and the C-phase breaker is energized at 1.3'A.
-2b, 9A-1b, 1.4 A through 9B-1bt
-3 is energized and cut off.

In addition, the non-faulty phases of two-wire grounding are, for example, in the case of a C-phase connected pond, C-phase circuit breakers 9A-2, 9B-2, 9A-:
3.9 After B-3 is cut off and the fault is cleared, the C-phase breaker is 9A-2b, 9A-3b, 9B-2b, 9B
-3b, the tripping coil 14A-1 is energized and cut off. In either case, there is no problem because the non-fault phase is cut off after the ground fault is completely removed and the current deviation disappears.

FIG. 6 shows another embodiment. In the figure, transmission line current is input to current zero point detectors 15A-1, 15A-2 and 15A-3 via current transformers 16A-1116A-2 and 16A-3. Although a modified example of the cutoff selection control device is also shown in Fig. 6, for the fault phase, the tripping coil is excited and cut off by the a contact of the ground fault detection relay of the own phase, and the example shown in Fig. 5 is the same as In the non-fault phase, one of the circuit breakers has already been disconnected, and 9A-1, b,
Current zero point detector contact 15A-1 closes when either 9A-2b or 9A-Jb closes and the current deviation decreases due to fault cutoff, and the current phase current b1 passes through the zero point.
a, 15A-2a, and 15A-38 are closed, and interrupter trip circuits 14A-1, 1
4A-2 and 14A-3 are excited and cut off. When shutting off, the faulty phase is immediately shut off, so even if there is some delay in shutting off the non-faulty phase, there is no adverse effect on transient stability.

〔Effect of the invention〕

As explained above, according to the present invention, in the event of a ground fault, the faulty phase with no risk of current deviation is cut off in advance 2, and the current deviation of the non-faulty phases with a large risk of current deviation is eliminated by the faulty phase cutoff. Since it is shut off later, it is possible to effectively eliminate the inability to shut off due to large current deviations.

[Brief explanation of drawings]

Figure 1 is a transmission line current waveform diagram at the time of a fault, Figure 2 is a transmission line current waveform diagram with a small current deviation, Figure 3(a) is a power transmission system diagram, and Figure 3(a) is a transmission line current waveform diagram. b) is an equivalent diagram V showing a configuration diagram of another embodiment when a one-wire grounding failure occurs. I...I'lf, Machine, 2...Outside voltage transformer, 3...Shipping'Ichikinu 11 4...City! ib, 5...11-phase impedance, 6... convenient impedance, 7... zero-sequence impedance, 8... acid 1, positive phase of flow, 9... circuit breaker, 10
... Information transmission device, 11... Cutoff selection control device, 12... Transmission line, 13... Ground failure phase detection relay, 14... Breaker trip coil, 15... Current zero point detection 16...Current transformer. (7317) Representative Patent Attorney Noriyuki Chika (and 1 others)
Figure 1 Figure 2 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] In a new method for breaking fault current at the time of a ground fault in a power system in which a generator is connected to a power transmission line via a step-up transformer having a Y△ connection, a breaker at both ends of a faulty phase in a faulty section of a power transmission line is cut off in advance, A new fault current isolation method characterized by cutting off non-fault phases after the ground fault has been removed.