Abstract: An electrical system and a sensor for on-line monitoring of the state of high-voltage insulation in the electrical system. In this arrangement, the signals associated with partial discharge activity are monitored and transmitted from the sensor to monitoring instrumentation. The sensor is interconnected with the potential stress shield of existing bushings. The capacitance in the bushing between the main conductor and the stress shield conducts partial discharge current which is available for being sensed.

Abstract: An electrical system and a sensor for on-line monitoring of the state of high-voltage insulation in the electrical system. In this arrangement, the signals associated with partial discharge activity are monitored and transmitted from the sensor to monitoring instrumentation. The sensor is interconnected with the potential stress shield of existing bushings. The capacitance in the bushing between the main conductor and the stress shield conducts partial discharge current which is available for being sensed.

Abstract: Electrical switchgear for receiving either a vacuum circuit breaker or a dummy element and including a levering-in assembly with a positional interlock bar that is operated by a levering-in block in the levering-in assembly and by a finger on the dummy element. Access to the levering-in device is blocked when the source breaker is in the connect position. A key to unlock the access is obtained by levering the source breaker or a dummy out to the test position and locking it in that position or by levering a dummy element to a connect position and locking it in that position.