Reclaim Time; Discrimination Time Setting - GE MiCOM P40 Agile Technical Manual

P44x/EN AP/Hb6
(AP) 5-154
• CB Opening + Reset time (Trip coil energised → Trip mechanism reset): 200ms
(b);
• Protection reset time: < 80ms (c);
• CB Closing time (Close command → Contacts make): 85ms (d).
De-ionising time for 220kV line:
• 280ms (e) for a three phase trip. (560ms for a single pole trip).
The minimum relay dead time setting is the greater of:
(a) + (c)
(a) + (e) - (d) = 50 + 280 - 85
In practice a few additional cycles would be added to allow for tolerances, so 3P - Dead
Time 1 could be chosen as ≥ 300ms, and 1P - Dead Time 1 could be chosen as ≥ 600ms.
The overall system dead time is found by adding (d) to the chosen settings, and then
subtracting (a). (here this gives 335ms and 635ms respectively).

5.10.1.3 Reclaim time

When the CB has closed, the reclaim time ("Reclaim Time") starts. If the circuit breaker does
not trip again, the autoreclose function resets at the end of the reclaim time. If the protection
operates during the reclaim time the relay either advances to the next shot in the
programmed autoreclose cycle, or, if all programmed reclose attempts have been made,
goes to lockout. The reclaim time is reset on expiry of the reclaim time-delay (setting) or if a
new 1P or 3P trip command is issued (see logic diagram).
A number of factors influence the choice of the reclaim timer, such as;
• Fault incidence/Past experience - Small reclaim times may be required where there is
a high incidence of recurrent lightning strikes to prevent unnecessary lockout for
transient faults.
• Spring charging time - For high speed autoreclose the reclaim time may be set longer
than the spring charging time. A minimum reclaim time of >5s may be needed to allow
the CB time to recover after a trip and close before it can perform another trip-close-
trip cycle. This time will depend on the duty (rating) of the CB. For delayed autoreclose
there is no need as the dead time can be extended by an extra CB healthy check AR
Inhibit Wind window time if there is insufficient energy in the CB.
• Switchgear Maintenance - Excessive operation resulting from short reclaim times can
mean shorter maintenance intervals.
• The Reclaim Time setting is always set greater than the tZ2 distance zone delay.

5.10.1.4 Discrimination time setting

When a single pole trip is issued by the relay, a 1-pole autoreclose cycle is initiated. The
Dead time1 and Discrimination timer are started.
If the autoreclose logic detects a single pole or three-pole trip (internal or external) during the
discrimination time-delay, the 1P high speed autoreclose cycle is disabled and replaced by a
3P high speed autoreclose cycle (if 3P trip mode is enabled, otherwise, the relay trips 3-
poles and the autorecloser is blocked):
= 50 + 80 = 130ms, to allow protection reset;
= 245ms, to allow de-ionising (three pole);
= 50 + 560 - 85 = 525ms, to allow de-ionising (single pole).
Application Notes
MiCOM P40 Agile P442, P444