ZW20A-12F type outdoor high-voltage AC boundary vacuum circuit breaker (commonly known as watchdog) is a kind ofoutdoor power distribution equipment with 12KV rated voltage and 50Hz three-phase alternating current.
When T type wiring of 12kV distribution line gets user internal error, or although this problem happens in the inner side of user’sinlet switch, when the time limit of its protection operation and the protection of transformer substation’s outlet switch areimproper, it will cause separating brake of protection of transformer substation’s outlet switch. If the fault is permanent, the re-
closure of substation will be unsuccessful. So, the trouble within a middle voltage user interface will make the whole distributingmain line out of power. This common secondary failure in powernetwork will cause serious loss to the society.
ZW20A-12F type outdoor high-voltage AC boundary vacuum circuit breaker is installed in the responsibility boundary point ofoverhead distribution line, then the front end of user line side will cut off the single-phase ground fault and inter-phase shortcircuit fault automatically, to avoid the user interface’s fault from spreading to the transmission main line.
This kind of switch can realize the following functions: instantaneous trip protection, over-current protection, three-timereclosing, event recording, anti- surge protection, zero-sequence protection, real-time clock, acceleration after automaticreclosing, real-time status query, smart tablet computer control, local or remote setup of setting value, active report of faul.
1. Automatic locking phase-to-phase short circuit fault: when a phase-to-phase short circuit fault happens in user branch line, after trippingbefore the transformer substation carries out the protection action, the boundary circuit breaker immediately switches off and locks out.
2. Automatic removal of single-phase earth fault: when a single-phase earth fault happens in user branch line, the boundary circuit breakerswitches off automatically before the transformer substation carries out the protection action; both the transformer substation and trunkbranch users do not feel the occurrence of failure.
3. Rapid positioning of fault points: after the user branch failure causes protective action by boundary circuit breaker, responsibility userswill face a power failure and take the initiative to submit failure information, then electric power company will send people to the site tofind out the cause of the failure through handheld computers or communication module, so as to restore the power in time.
4. To keep the original circuit breaker function: the boundary circuit breaker has abilities to cut off 20-25KA short circuit current.