Alstom UK Limited

Alstom

Areva T&d Sa

Zhiqian Bo

A protection system for an electrical power line system of the type comprising radially connected power line sections, wherein a first electrically upstream one of the line sections is connectable to a power source. The protection system comprises at least one relay installed at or near at least the upstream end of each line section to protect that line section, each relay having an associated circuit breaker. The relays are provided with a first set of accelerated overcurrent functions and a second set of under-current/under-voltage functions, the relays being directional and the first and second sets of functions being time graded in reverse to each other. The first and second sets of functions are distributed amongst the relays such that if an under-current/under-voltage function in a second relay located downstream of a first relay triggers operation of a circuit breaker associated with the second relay, an accelerated overcurrent function in the first relay triggers accelerated operation of a circuit breaker associated with the first relay, thereby to isolate from the power source the line section that the first relay protects.

Power line protection

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.

Protection of electrical power lines

A fault protection apparatus is disclosed for use in a time graded fault protection scheme. The apparatus comprises a circuit breaker having a normally closed trip contact provided in a line, current measurement apparatus adapted to produce an output signal indicative to the current in the line at the circuit breaker, and fault signal processing apparatus adapted to process the output signal from the current measurement apparatus to detect an initial fault on the line at a first instance. The fault signal processing apparatus is further adapted to process the output of the current measurement apparatus after the initial fault has been detected and to produce an accelerated opening signal in the event that the output signal meets a predetermined criteria, and a control device which is adapted to open said circuit breaker trip contact in response to said accelerated opening signal.

Fault protection apparatus

A method of protecting a section of a line is disclosed. The method comprises providing a local fault protection assembly at one end of the section distal from at least one remote fault protection assembly at the other side of the section, each assembly comprising a circuit breaker, a line signal measurement assembly adapted to produce an output signal indicative of the voltage or current on the line, and a signal processing assembly adapted to process the output signal to produce a fault signal in the event that the output signal indicates the presence of a fault in the line, the method comprising the steps of monitoring the output signal from the signal measurement apparatus at the local circuit breaker to detect the presence of a fault within a first zone extending over at least a part of the section from the local breaker or outside of this first zone, and in the event that the output signal is indicative of a fault within the first zone substantially instantly opening the local circuit breaker, and in the event that the fault is outside the first zone detecting the operation of the remote circuit breaker by monitoring the output signal from the local signal measurement apparatus, monitoring the output signal to determine the condition of the section of line after the remote circuit breaker has been operated, and operating the local circuit breaker in the event that the fault condition meets a predetermined criteria.

Growing community of inventors

Bath, United Kingdom

Zhiqian Bo