Protection function of
circuit breaker 2
1. Charging protection
The charging protection is composed of two-stage two-time limit phase over-current and one-stage zero-sequence over-current. The current is taken from the TA of the circuit breaker. When the charging protection is switched on, the phase current element of the corresponding section will trip after the corresponding setting delay and the outlet of the charging protection will trip the
circuit breaker. After the charging protection is activated, the failure protection is activated, and then other circuit breakers are tripped through the failure protection delay outlet. In addition, failure protection, dead zone protection, inconsistency protection, and charging protection actions all block and reclose. The charging protection is only activated when the line (transformer) is charging, and it will exit immediately after the charging is normal.
2. Dead zone protection
The cause of the dead zone: When a short circuit occurs between the circuit breaker and the current transformer, in many cases the fault cannot be removed after the protection is activated.
Significance of dead-zone configuration: Considering such dead-zone faults in the station, the current is generally larger and the impact on the system is also greater. Although reliable failure to remove, the failure protection action generally requires a long delay, so special Set up a dead zone protection faster than the failure protection action.
Dead zone protection input: on the basis of failure protection input, the dead zone protection control word is also put into the dead zone protection function to take effect.
The action of the dead zone protection: three-phase trip signal + three-phase trip + dead zone current action, the dead zone protection is activated after the dead zone delay.
Dead zone protection outlet: the same as the breaker failure protection outlet, that is, which
circuit breakers are tripped at the failure outlet of the side circuit breaker, and which circuit breakers are tripped at the dead zone outlet of the side circuit breaker.
This is why the dead zone protection is attached to the failure protection plate. The dead zone protection can also be understood as an alternative failure protection.
3. Three-phase inconsistent protection
The origin of the three-phase inconsistency: For the split-phase
circuit breaker, due to equipment quality and operation, there may be inconsistent actions of the three-phase circuit breaker during operation, resulting in only one or two phases tripping, which is in a non-full-phase abnormal state.
The harm of three-phase inconsistency: When the system is in a non-full-phase operation state, the negative sequence, zero sequence and other components in the system will cause certain harm to the electrical equipment, and also affect the correct operation of the system protection device, so the power system is not allowed to be long Incomplete phase operation in time.
If the line reclosing is unsuccessful, when the system enters the non-full-phase operation, there will be no other protection to eliminate this fault. Therefore, the non-full-phase protection (three-phase inconsistent protection) is installed in the circuit breaker of the split-phase operation. When the phase reaches a certain time, the other phases are skipped.
Realization of three-phase inconsistency: The protection function to eliminate the abnormal state of three-phase inconsistency. In high-voltage or ultra-high-voltage systems, the
circuit breaker is generally placed in the
It is implemented in the body, but it is also implemented in the circuit breaker protection (or line protection).
The inconsistency protection is in the circuit breaker body, the national grid 18 countermeasures requirements: 220kV and above voltage level circuit breakers should be equipped with the three-phase position of the circuit breaker body
Inconsistent protection. Even after the single-phase tripping of the
circuit breaker, if the reclosing action, the circuit breaker fails to reclose due to pressure, mechanical, secondary circuit, etc., the three-phase must be tripped within 2-2.5s, and no reclosing is required. Ensure the safety of the system.
When there is no three-phase inconsistency protection in the circuit breaker, an independent three-phase inconsistency protection device can be installed. Independent three-phase inconsistent protection except for circuit breakers
In addition to the auxiliary contact or position contact forming the starting circuit for judging the three-phase inconsistency, zero sequence current and negative sequence current can also be used to block the circuit to improve the reliability of the circuit.
Input of three-phase inconsistency protection: When the three-phase inconsistency protection soft plate and hard plate are both put in, the three-phase inconsistency protection function will work.
Three-phase inconsistent start: three-phase jump position input is inconsistent + jump position phase no flow.
The action of the three-phase inconsistency protection: the inconsistency is activated by the zero sequence opening control word, the inconsistent start is activated by the inconsistent zero sequence current criterion, and then the three-phase circuit breaker is tripped through the inconsistent delay outlet. The inconsistency is activated by the negative sequence opening control word, the inconsistent start is activated by the inconsistent negative sequence current criterion, and then the three-phase circuit breaker is tripped by the inconsistent delay outlet. When the above two control words are both exited, the three-phase
circuit breaker will be tripped by the inconsistent delay outlet after the inconsistent three-phase start.
The three-phase inconsistency protection action does not start failure, and at the same time the recloser is blocked.
Locking of three-phase inconsistent protection: The
circuit breaker is in a three-phase inconsistent state for 12 seconds, a position inconsistency alarm is issued, and the three-phase inconsistency protection is blocked.
The setting principle of the time relay of the three-phase inconsistent protection: The delay setting of the three-phase inconsistency protection of the relay protection device should be able to avoid the action time of the reclosing.
4. Instant follow jump
This loop is up to the user to decide whether to put it in. Instantaneous follow-up is divided into: single-phase follow-up, two-phase trip combined three-phase and three-phase follow-up. Jump after these three loops exit
For this
circuit breaker, only the above three circuits can send a trip command when the starting element is active. Single-phase follow-up: Receive the Ta, Tb, Tc single-phase trip signal from the line protection, and the corresponding phase's high constant current element will act, and the instantaneous phase trip will occur.
Two-phase tripping and three-phase tripping: the two-phase tripping signal from the line protection is received and only the two-phase tripping signal is received, and the high constant current element of any phase is activated, and the three-phase tripping will be combined after a 15ms delay.
Three-phase follow-up: After receiving a three-phase trip signal, and the high constant value current element of any phase acts, the instantaneous three-phase trip exits.
5. Judgment of AC voltage disconnection
The criterion for the judgment of AC voltage disconnection is: the protection does not start, and the three-phase voltage vector sum is greater than 12V, and the TV short-line abnormal signal is sent after a delay of 1.25s. When the TV is disconnected, the low-power factor component will be withdrawn, and the synchronization detection and non-pressure detection functions will be exited, and other functions are normal. When the three-phase line voltage returns to normal 10s, it will automatically resume normal operation.
6. Alarm for abnormal trip position
When the TWJ is active and the phase circuit has current, or the TWJ positions of the three phases are inconsistent, the TWJ abnormality will be reported after a 10S delay.
