Mar 2013
Electricity Distribution
Transient Fault Detection from Disturbance Recorders
Mar 2013
Western Power Distribution
WPD Future Networks Team (01332 827446)
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Carbon Emission Reduction Technologies
Pecking faults are small discharges caused by voids within the insulation of distribution cables, or surface tracking over compromised insulation on equipment. The discharges are insufficient to cause circuit protection devices to initiate a trip signal and will self heal temporarily.

As these network disturbances do not cause loss of supply and are difficult to detect, they are normally ignored, but evidence suggests that they can re occur at irregular intervals and are often the precursor to the development of a more serious fault. If these incipient faults can be identified with equipment that can detect the small dips on the voltage waveform and short surges in current, then proactive action could be taken. If the pecking fault waveform changes are sufficient to allow the disturbances to be interpreted as an impedance value to the point of fault, then this information can be used with GIS data to determine search areas allowing these potential faults to be located and rectified before they cause a loss of supply to any customers.

The project has been extended so that data collected from the monitoring of the substation battery can be used to identify the time of operation of the trip coil so that protection and switchgear operating times can be differentiated, allowing identification of any incorrect protection or circuit breaker clearance operation.

Use of disturbance recorder information to determine a search area for of potential faults by interpreting the waveform characteristics associated with self healing pecking faults.