Enertec

Paul Loewenstein

Isabelle Heller

The invention concerns a method of direct measurement of a parameter characterizing a fault on an electricity line 1, such as the distance x or the resistance R.sub.d of the fault, the method being based on Ohm's Law including the line inductance L and the resistances R, R.sub.d. The signals respectively associated with the variation of current i(t) and of voltage v(t) at the measuring point M are operated upon by transfer functions the ratio of which is equal to:

Method of measuring the distance of a fault on a line taking account of

A directional relay for providing indication of the direction of a fault on an electric power transfer network has an adder (9), a subtractor (10) and filters (11) which receive signals from voltage and current transformers (6,7) and derive signals related to fault-induced forward and backward transient waves on the network. To ensure reliable operation even when the relay is close to a low impedance element such as a generator (2), the forward wave related signal is delayed in a delay unit (12) by an amount equal to the propagation time of the wave along the section protected by the relay, before the difference between its square and that of the backward wave related signal are integrated (16) to derive the fault direction signal. If the protected section has a low distributed capacitance, the voltage and current signals can instead be combined by a differentiator (22) and adder (23) and filtered (11B) to produce a signal related to the forward transient wave appearing at a point X along the protected section. The integrator (16) receives the product of this signal and the filtered current signal.

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Mountain View, CA, United States of America

Paul Loewenstein