ABB RELION 620 Series Technical Manual page 737

1MAC504801-IB E
620 series ANSI
Technical Manual
Transient and semi-transient faults can be cleared by momentarily de-energizing the
power line. Using the autoreclose function minimizes interruptions in the power system
service and brings the power back on-line quickly and effortlessly.
The basic idea of the autoreclose function is simple. In overhead lines, where the
possibility of self-clearing faults is high, the autoreclose function tries to restore the power
by reclosing the breaker. This is a method to get the power system back into normal
operation by removing the transient or semi-transient faults. Several trials, that is,
autoreclose shots are allowed. If none of the trials is successful and the fault persists,
definite final tripping follows.
The autoreclose function can be used with every circuit breaker that has the ability for a
reclosing sequence. In 79 autoreclose function the implementing method of autoreclose
sequences is patented by ABB
Table 536: Important definitions related to autoreclosing
autoreclose shot an operation where after a preset time the breaker is closed from the breaker tripping
caused by protection
autoreclose a predefined method to do reclose attempts (shots) to restore the power system
sequence
SOTF If the protection detects a fault immediately after an open circuit breaker has been
closed, it indicates that the fault was already there. It can be, for example, a forgotten
grounding after maintenance work. Such closing of the circuit breaker is known as
switch on to fault. Autoreclosing in such conditions is prohibited.
final trip Occurs in case of a permanent fault, when the circuit breaker is opened for the last time
after all programmed autoreclose operations. Since no autoreclosing follows, the circuit
breaker remains open. This is called final trip or definite trip.
Section 9
Control functions
731