Field breaker tripping options for generator static excitation systems with AC field circuit breakers - A case study
Short circuit contributions from synchronous generators can persist for several seconds even after the field circuit breaker is opened. Delayed tripping of an AC field circuit breaker can allow faster reduction of generator field current in some circumstances. Faster reduction of generator field current will reduce the energy in a short circuit and consequently reduce the damage caused by the short circuit. This paper describes a case study examining the issues associated with the decision to delay tripping of AC field circuit breakers.
Modern technical aspects of Field Discharge equipment for excitation systems
The ANSI/IEEE C37.18 1979 ldquostandard enclosed field discharge circuit breakers for rotating electrical machineryrdquo [1] has passed through several reaffirmations and still valid until 2008. This standard provides excellent information and is widely used as basis for the specification, design and testing of field discharge equipment. However, the content of this standard still reflecting the technological state of the art for equipments designed and manufactured during the time that this standard was being approved for the first time (1976). This paper contains an overview of the actual technological aspects of field discharge equipment in terms of available technology, design criteria and practical executions. The information of this paper could be partially used for future actualization of the IEC37.18.
Detection of fast neutrons in a plastic scintillator using digital pulse processing to reject gammas
Abstract We report on neutron–gamma discrimination in a plastic scintillator based on the time delay inherent in second and third chance neutron scattering. Because of the time delay (≈3 ns) between the first and second scattering of a neutron, calculations of gammas and neutrons in a plastic scintillator predict that a neutron signal should be significantly broader than a pulse from a gamma event. Experimentally, we have used a fast digital oscilloscope coupled to a computer to examine individual pulses from neutron or gamma induced signals in fast scintillators coupled to a fast PMT. Individual neutron-induced signals were consistent with the predictions of our model, but gamma pulses were broader than expected. We present various tests to understand this phenomenon and discuss a way to overcome this problem.