Protection of electrical power lines
AssigneeAlstom
InventorZhiqian Bo
Life of this patent
Estimating the term…
Abstract
A method of protecting a section of a three phase power line uses superimposed current components in the power line to enable a local relay to detect operation of remote circuit breakers of remote relays in response to a fault on at least one phase of the power line. Line signal transducers output line condition signals indicative of voltage and/or current in the line near the circuit breaker, and a signal processor in the local relay processes the line condition signals to selectively produce a fault signal for opening its circuit breaker after taking account of remote circuit breaker operation.
Claims11
A method of protecting a section (LINE1) of a three-phase power line characterised by the use of superimposed current components (Ibs, Ics) in the power line to detect operation of remote circuit breakers (B12, B21) in response to a fault on at least one phase of the power line.
A method of protecting a first section (LINE1) of a three-phase power line, said first section having local and remote ends (S, R) and being joined to at least a second section (LINE2) at said remote end (R), a local fault protection apparatus (R11, R1F)) and a first remote fault protection apparatus (R12, R1R) being provided at said local and remote ends respectively to establish a protected zone therebetween, and at least a second remote fault protection apparatus (R21, R2F) being provided to protect said second section (LINE2), each fault protection apparatus comprising a circuit breaker (B11, B12, B21, B1F, B1R, B2F), measurement means (CT, VT) for outputting line condition signals indicative of voltage and/or current in the line near the circuit breaker, and a signal processing means adapted to process the line condition signals to selectively produce a fault signal for opening the circuit breaker in response to a fault in the line, the method being performed by the signal processing means of at least the local fault protection apparatus (R11, R1F) and being characterised by the steps of:
- (A) monitoring the line condition signals to detect faults either in the protected zone or outside the protected zone;
- and
- (B) opening the circuit breaker of the local fault protection apparatus
- (i) instantly if a fault is detected in the protected zone;
- or
- (ii) after either a first delay or a second shorter delay if a fault is detected outside the protected zone, the first and second delays being determined by monitoring the line condition signals and choosing the first or second delay according to whether the line condition signals meet a first or a second predetermined criterion respectively.
A method according to any preceding claim comprising the additional steps of defining a time window within which operation of a circuit breaker of a remote fault protection apparatus can be expected and ignoring any changes in the magnitude of an unfaulted phase current outside the time window, thereby facilitating correct detection of operation said circuit breaker.
A fault protection apparatus adapted to perform a method according to any one of the preceding claims.
Dependencies are inferred from the claim text.