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Re Watchdog contact. I have since found that the watchdog contact is wired to a spare input on another electronic feeder relay on site. Have now found from the other relays events that the watchdog contact did operate during the fault period. Setings for the relay have been verified as being...

Unfortunately the relay was not being polled or watchdog contacts monitored. During commissioning integral earths were mistakenly left on at the 22kV incomer. The transformer was livened from the point of supply some 25kM away from the substation. The 66kV transformer protection at the...

Interested to know if anyone has experienced problems with modern electronic protection relays designed for power transformers. I have recently experienced failure to operate with a close in secondary earth fault on a recently commissioned 66/22kV power transformer. The device appears to have...

Is there any resouce available to assist with better understanding of this phenomonon or ways of overcomming the problem. The problem exists with single phase switching, fusing of three phase transformers connected to relatively long lengths of underground cable. I understand the resonance is a...

Does any one know of any economic method of linking and teeing off 22kV cable above ground similar to 11kV systems such as HOLEC, Elastimold. I am looking at the prospect of installing cable instead of O/H line in some rural built up areas but research to date indicates that costs are still to...

Lower than 10 ohms is seen as a desirable value. However this is not always possible without an uneconomic amount of cost. In situations where low resistances are unachievable it is important to evaluate the step and touch values so as to minimise risk of injury. Other ways of equi potential...

From a rural overhead distribution perspective it is normal to install 3 phase overcurrent and earth fault on each feeder. Normal setting for earth fault in this case is 10% of the overcurrent setting and deffinate time of .5 seconds. Of course with better earthing you may get away with greater...