JP3307063B2 - Power system protection apparatus and method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a power system protection device and
Relates to the method, especially was series compensation (hereinafter, series compensation system as referred) protection device suitable power system protection against zero-less phenomenon occurring during short circuit failure and related to the method
I do.

[0002]

2. Description of the Related Art In order to reduce the series reactance of a transmission line in a power system, there is a series compensation in which a capacitor is inserted in series with the transmission line. This is shown in U.S. Pat .
As Patent and U.S. Patent No. 4,829,229 999,565, is configured to bypass the both ends of the capacitor to the capacitor 5a, and 5b parallel.

FIG. 2 shows a single-phase circuit of a three-phase circuit of a three-phase two-line power transmission system, and series compensators 2a and 2b are installed in each line. Now, in order to cut off the fault currents 41a and 41b due to the ground fault that occurred at the position 4, the protection relays 32a and 32b determine the fault occurrence location, and provide a trip signal to the breakers 31a and 31b to be fault-protected. Circuit breakers 31a and 31b cut off the fault current. Normally, an overvoltage is generated across the series capacitors of the series compensators 2a and 2b. To prevent this, the series compensators 2a and 2b are provided with overvoltage protection devices 6a and 6b such as discharge gaps and arresters. Prevent occurrence.

[0004]

When a short-circuit fault occurs, if the timing operation for protecting the series capacitors 5a and 5b by bypassing the series capacitors 5a and 5b with the series compensating devices 2a and 2b is delayed or an error occurs such that the bypass cannot be performed. , An overvoltage occurs in the series capacitors 5a and 5b. If the bypass switches 7a and 7b in parallel with the series capacitors 5a and 5b are closed in such an inappropriate state, or if the series capacitors 5a and 5b are short-circuited due to insulation breakdown, the fault current 41 will be temporarily lost as shown in FIG. During this time, there may be a zero-less operation that does not pass through the current zero point.

It is assumed that a failure occurs at time 101, the overvoltage protection device malfunctions at time 102, and both ends of the series capacitor are short-circuited at time 103. During the period 106 during which the zero-less phenomenon occurs, the time 104 at which the circuit breaker 31a or 31b interrupts the fault current 41 is reached.
1a or 31b fails to shut off. Usually, the fault current interruption performance of the circuit breaker is guaranteed within a range of 0.5 to 2.0 cycles after the breaker is opened. Therefore, if a zero-less phenomenon occurs in this range, the breaker will not be able to shut off,
Reclosing is also difficult.

[0006] The present invention has been made in view of the above points,
And it has as its object to solve the aforementioned problems, in that provides a protection device and method for a power system fault protection can be performed reliably.

[0007]

In order to solve the above problems, the present invention monitors the operation of a bypass protection device of a series compensator, detects a malfunction of the bypass protection device, and detects a fault current to be cut off. When it is determined that the zero-less phenomenon occurs, information for controlling the opening start time of the circuit breaker is given to the protection relay that operates the circuit breaker that should interrupt the fault current, and after the zero-less phenomenon is eliminated. , in which so as to cut off the fault current immediately.

[0008]

By using the above means, the failure protection of the series compensation system can be performed reliably and at high speed. Further, the zero-less phenomenon of the breaking current which is likely to occur in the series compensation system can be dealt with even by using a normal AC circuit breaker, and it becomes unnecessary to use a circuit breaker having a special structure.

[0009]

FIG. 1 shows an embodiment of the present invention.
The series compensator 2 includes a series capacitor 5, an overvoltage protection device 6 such as a discharge gap or an arrester, which is a bypass protection device, and a bypass switch 7.

The protection device 1 has a bypass current 11 which is the sum of the currents flowing through the overvoltage protection device 6 and the bypass switch 7.
And the series capacitor terminal voltage 12 of the series capacitor 5 is input. The system failure information 13 is input from a protection relay (not shown). From the bypass current 11, the series capacitor terminal voltage 12, and the failure information 13, the protection device 1 determines whether the bypass protection operation of the series compensator 2 is caused by a system failure, and determines whether the bypass protection in the series compensator 2 is successful. And whether the zero-less phenomenon occurs in the breaking current of the circuit breaker is given to the protection relay as the determination information 14. The determination information 14 is given to the protection relay for operating the circuit breaker before issuing a trip signal to the circuit breaker.

Determination information 14 that a zero-less phenomenon occurs
The protection relay that has received the signal waits for a trip signal to the circuit breaker until the zero-less phenomenon is resolved. When there is no zero-less phenomenon in the breaking current, the protection relay immediately issues a fault current breaking command to the breaker.

As a criterion for determining the success or failure of the bypass protection in the series compensator 2 of the protection device 1, for example, failure
A time difference is obtained by comparing the failure occurrence time from the time with the bypass protection time from the bypass current 11 and the series capacitor terminal voltage 12, and when the time difference exceeds a preset allowable range, it is determined that the bypass protection has failed. To do.

Alternatively, a difference between the series capacitor terminal voltage 12 and a preset overvoltage protection level or a variation in bypass protection operation between each phase or line is used, and when these values exceed allowable values, bypass protection is performed. You may judge that it failed.

In the example of FIG. 3, the time 102 when the overvoltage protection has failed is the earliest as the determination time. When the zero-less phenomenon occurs in the breaking current, the time 105 at which the breaker can cut off the current is set.
The protection device 1 determines the judgment information 1 so as to interrupt the fault current at
4 to the protection relay.

As described above, the fault protection device for a series compensation system according to the present invention can reliably shut off the failure of the circuit breaker particularly against the zero-less phenomenon of a fault current which is highly likely to occur in the series compensation system. And the circuit breaker is reclosed, and the reliability of the series compensation system can be improved.

FIG. 4 is a sequence example of the protection device 1 for controlling the failure protection operation of the circuit breaker. The fault current interruption period 112 of the normal interruption in which the zero-less phenomenon does not occur has a time width 111 of 0.5 to 2.5 cycles from the failure occurrence time 101. On the other hand, when the zero-less phenomenon occurs, in the zero-less occurrence period 106, the circuit breakers 31a and 31b are not opened but wait until a time 113 when the zero-less phenomenon disappears.
Immediately after the zero-less phenomenon is resolved, the circuit breakers 31a and 31b
, The fault current cutoff period 112a is shifted until the cutoff time width 111a.

FIG. 5 shows an example of the configuration of the protection device 1. The current judging unit 15 determines whether a current has flowed from the bypass current 11 to the bypass protection device. The bypass protection suppresses an increase in the voltage across the series capacitor. A voltage determination unit 16 that determines from the terminal voltage 12 of the series capacitor and a determination information output unit 17 that determines whether the breaking current of the circuit breaker becomes zero-less current.

The current judging section 15 outputs the presence or absence of a current or the time during which the current flows. The voltage determination unit 16 outputs whether or not an overvoltage has occurred. The determination information output unit 17 is configured to output the current determination unit 15 or the voltage determination unit 16 or the failure information 13
Therefore, it is determined whether or not a zero-less fault current will be obtained, and the determination information 14 is output. In particular, if the zero-less current generation condition obtained by the system analysis is given to the determination information output unit 17 in advance, it can be used as a criterion for zero-less current generation prediction.

FIG. 6 shows an embodiment in which the present invention is applied to the case of two-line power transmission. Depending on the occurrence of a failure, bypass protection of the series capacitor may be required in any of the series compensators 2a and 2b. Therefore, the protection device 1 includes the currents from the series compensators 2a and 2b, the voltage bypass currents 11a and 11b, and the series capacitor terminal voltage 12a.
a and 12b are given as information. The determination information 14a, 14b from the protection device 1 is transmitted to the protection relay 32a, 3
2b, the protection relays 32a and 32b trip the circuit breakers 31a and 31b as usual when the zero-less current does not flow, and shut down the failure. When the zero-less current flows, the protection relays 32a and 32b wait for the zero-less elimination and then trip. To shut down the fault.

By using the present invention, short-circuit fault protection of the series compensation system can be reliably performed.
1b has an advantage that a circuit breaker generally used in a normal AC system can be used as it is. Also, as gas breakers are mainly used in AC systems with high voltage or higher, use a gas breaker with a longer arc and a longer arc between the poles, or use multiple circuit breakers connected in series. Then, the DC component of the fault current 41 attenuates faster, and the fault occurrence time 10
The time from 1 to the time 113 when the zero-less phenomenon disappears can be shortened.

Further, the protection device 1 determines whether bypass protection has been performed or not, and furthermore, the protection relays 32a, 32b.
Of the current flowing in the system from the current signal at the zero point, and the occurrence and continuation of the zero-less phenomenon are judged together with the judgment information 14 from the protection device 1, and the circuit breakers 31a, 31b
Can be controlled. In this method, since the occurrence of the zero-less phenomenon is monitored twice, the reliability of the opening start time control of the circuit breaker is increased.

The time from the fault occurrence time 101 shown in FIG. 4 to the time 113 at which the zero-less phenomenon disappears is about 5 to 10 cycles, depending on system conditions and fault conditions. As a result, the failure protection is delayed by about 2 to 7 cycles. However, the time during which a circuit breaker can exhibit the breaking performance according to its specifications is usually at most about two cycles at most. Therefore, to protect the failure without preventing the circuit breaker from being able to break and from being closed again It is effective to use the method and apparatus for protecting a failure of a series compensation system according to the present invention.

[0023]

According to the present invention, fault protection in the series compensation system is ensured, and in particular, the conventional circuit breaker can cope with a zero-less phenomenon of a fault current which is likely to occur in the series compensation system.

[Brief description of the drawings]

FIG. 1 is a fault protection device for a series compensation system according to the present invention.

FIG. 2 shows fault protection of a conventional series compensation system.

FIG. 3 is an example of a fault current waveform.

FIG. 4 is an example of an operation sequence of the circuit breaker.

FIG. 5 is a configuration example of a failure protection device according to the present invention.

FIG. 6 is an application example of a method and an apparatus for protecting a failure of a series compensation system according to the present invention.

[Explanation of symbols]

1: protection device, 11, 11a, 11b: bypass current,
12, 12a, 12b ... series capacitor terminal voltage, 13
... failure information, 14, 14a, 14b ... zero-less occurrence determination information, 15 ... current determination unit, 16 ... voltage determination unit, 17 ... determination information output unit, 2, 2a, 2b ... series compensator, 31a,
31b ... breaker, 32a, 32b ... protection relay, 41,
41a, 41b: fault current, 106: current zero-less occurrence period, 113: zero-less elimination time.

Continuation of the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02H 3/08-3/253 H02H ⁷ /00-7/20 H02J 3/00-5/00 G05F 1/70

Claims (3)

(57) [Claims] 1. A series capacitor inserted in series in a power system.
And a bypass for bypassing both ends of the series capacitor.
A power system including a protection device and controlling power of the power system
In the protection apparatus of the integration, and means for detecting the operating condition of the bypass protection device, the
Distribution to the power system according to the operation state detected by the detection means.
Equipped with control means for controlling the opening time of the installed circuit breaker
A power system protection device, characterized in that: 2. A series capacitor inserted in series with a power system.
And a bypass for bypassing both ends of the series capacitor.
Using a compensating device having a protection device,
In a power system protection method for controlling a power state, a terminal voltage across the series capacitor and the bypass protection are provided.
By monitoring the current flowing through the device, the operation of the bypass protection device is monitored.
Judging the operation status, and checking the power of the circuit breaker
Judging the flow situation, said interruption when said current has a zero point
Power system, characterized in that the
Protection method. 3. A series capacitor inserted in series with a power system.
And a bypass for bypassing both ends of the series capacitor.
Using a compensating device having a protection device,
In a power system protection method for controlling a state, a voltage across the series capacitor and the series capacitor may be exceeded.
Voltage with the set voltage of the bypass protection device to protect the voltage
Difference and the bypass after an abnormality occurs in the power system
By using the time difference until the current flows through the protection device,
Means for evaluating the operation of the power protection device,
Within the preset time for the breaking current of the circuit breaker
It is determined that a zero-less current is generated in the zero-less current.
Is turned on by the circuit breaker when
A method for protecting a power system, comprising interrupting current.