Monitoring protection and switchgear performance on distribution systems

Security of supply on 11 kV overhead line networks depends on many factors from the mechanical strength of the supports and conductors to the speed and discrimination of the protection and switchgear. Protection and switchgear must be considered together since it is their combined behaviour which determines how much of the network is disconnected when a fault occurs. Assessment of the performance of protection and switchgear, especially following the maloperation of one or the other, is difficult without quantitative data on the amplitude and duration of fault currents. The author presents a recorder which can monitor a number of circuits using a CMOS microprocessor