Micom P721, Technical Manual

Page: 288 / 334

P72x/EN CM/C21 Commissioning and Maintenance
Page 18/28 MiCOM P721/P723
Values to be recorded:
[95] Threshold I Sup for each phase
Time delay tSup for each phase.
[95] Threshold I Sup check:
If the time delay [95] Fault Timer t Sup is short, gradually increase the injected current to [95]
Threshold I Sup and verify that [95] Sup is asserted. Keep injecting the current and after the
timer elapses verify that [95] tSup is also asserted.
If the time delay [95] Fault Timer t Sup is long, inject 0.95
×
[95] Threshold I Sup and check
that [95] Sup is not asserted. Then inject 1.1
×
[95] Threshold I Sup and check that [95] Sup
is asserted. Keep injecting the later current and after the timer elapses verify that [95] tSup
is also asserted.
Gradually decrease the injected current and record the value of the drop out.
Checks:
Alarm message on the LCD.
Alarm LED flashes.
[95] tSup LED on (if programmed).
Trip output does not close
(If
Diff I Threshold [87]
2 2
Idiff
Sup I Threshold [95]
peak peak
<
×
<
−
and the [95] Fault timer
t Sup has elapsed).
[95A] tSup A output closes (if programmed).
[95B] tSup B output closes (if programmed).
[95C] tSup C output closes (if programmed).
[95] Fault Timer tSup check:
Apply a current onto one of the phases and measure the time delay [95] tSup by presetting
the current above the [95] Threshold I Sup (2 x [95] Threshold I Sup < I injected < [87]
Threshold I Diff) and verify that [95] Sup is asserted. Keep injecting the current and after the
timer elapses verify that [95] tSup is also asserted. Repeat the same test for phases B and
C using [95B] tSup B and [95C] tSup C respectively.
4.5.5 [95] Threshold I Sup with Fast mode
The Fast mode detects a number of samples above the threshold during one AC half cycle.
The Fast mode threshold is 2
× √
2
×
[95] Threshold I Sup.
Values to be recorded:
[95] Threshold I Sup for each phase
Time delay tSup for each phase.
[95] Threshold I Sup check:
If the time delay [95] Fault Timer tSup is short, gradually increase the injection current up to
the value of 2
× √
2
×
[95] Threshold I Sup and verify that [95] Sup is asserted. Keep
injecting the current and after the timer elapses verify that [95] tSup is also asserted.
If the time delay [95] Fault Timer tSup is long, inject 0.95 x 2
× √
2
×
[95] Threshold I Sup and
check that [95] Sup is not asserted. Then inject 1.1 x 2
× √
2
×
[95] Threshold I Sup and
check that [95] Sup is asserted. Keep injecting the later current and after the timer elapses
verify that [95] tSup is also asserted.
Gradually decrease the injected current and record the value of the drop out.