Typical alarms in gas insulated switchgear (GIS)

Low gas density (approximately 90%) in each gas compartment and zone signifying a gas leak.
Low gas density (approximately 80%) in each gas compartment and zone signifying that the dielectric ratings of the apparatus can no longer be met.
Low circuit breaker operating mechanism pressure (pneumatic, hydraulic or spring).
Low circuit breaker operating mechanism pressure signifying that the circuit breaker can no longer successfully open or close in this case the protection scheme may be design to block any operation. It should be noted that in addition to providing insulation, in most puffer type circuit breakers the gas also acts as a damper/cushion for the operating mechanism.
Loss of voltage to the circuit breaker mechanism’s motor supplying operating energy.
Loss of the DC control voltage or voltages to the circuit breakers.
Loss of DC control voltage to the annunciator in the local control cabinet.
Pole disagreement operation.
Excessive run-time of the circuit breaker operating mechanism’s motor supplying operating energy.
Overcurrent operation of the circuit breaker mechanism s motor protective.