Model meaning

Z: Vacuum Interruption

N: Indoor installation (indoor)

28: Design serial number

12: Rated voltage (kV)

Core function

Full current interrupting: safely interrupt rated current, overload current and short circuit current (up to 31.5kA).

Quick protection: the opening time is ≤60ms, and the fault current is cut off.

Typical application

Auxiliary power protection for incoming/outgoing lines of 12kV distribution system, distribution stations of industrial and mining enterprises and power plants (suitable for switchgear such as KYN28A-12 and XGN2-12).

Selection formula

Short-circuit verification: the expected short-circuit current of the system is less than or equal to the rated breaking current (Isc) of the circuit breaker.

Continuous current: maximum load current × 1.2 ≤ rated current (Ir)

Altitude correction: When it is more than 1000m, the volume of Ir decreases by 1% for every 100m increase.

Mechanical characteristic monitoring

Key indicators: opening speed (1.2 0.2m/s) and overtravel (4±0.5mm).

Abnormal threshold: speed drop > 15% or overtravel < 3mm → overhaul immediately.

Periodic maintenance

3 years /3000 operations:

Measure the resistance of the main circuit (standard: ≤45μΩ @ 1250A)

Check the contact wear (allowable wear ≤3mm)

10 years: replace the vacuum interrupter (compulsory scrapping cycle)

Safety specification

When operating, it must be in the test position/working position, and it is forbidden to open and close in the intermediate state.