Micom P721, Technical Manual

Page: 287 / 334

Commissioning and Maintenance P72x/EN CM/C21
MiCOM P721/P723 Page 17/28
Protection Menu
[95] PHASE BUS-WIRE SUPERV
[95] Phase Bus-Wire Sup YES
[95] Threshold I Sup 2.00 In
[95] Fault timer t Sup 3.00 s
[95] Measurement Filter Fourier, Sample, Fast sample modes
[95] Reset Timer tReset 0.00 s
AUTOMAT. CTRL/Output Relays
Assign [95A] tSup A, [95B] tSup B, [95C] tSup C and [95] Sup to any of the outputs relays
(RL2-RL8) to monitor the status of the bus wire supervision function.
4.5.3 [95] Threshold I Sup with Fourier mode
The Fourier mode is based on the module of the fundamental of the differential current.
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 up to
the value of the [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 x [95] Threshold I Sup and check
that [95] Sup is not asserted. Then inject 1.1 x [95] Threshold I Sup and check [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] Idiff Sup I Threshold [95]
< <
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 t Sup check:
Apply a current onto phase A and measure the time delay [95A] tSup A by presetting the
current above the [95] Threshold I Sup (2 x [95] Threshold I Diff
<
I injected
<
[87] Threshold
I Diff). Repeat the same test for phases B and C using [95B] tSup B and [95C] tSup C
respectively.
4.5.4 [95] Threshold I Sup with Sample mode
The sample mode compares the peak to peak value of the differential current divided by
2
× √
2 against the [95] Threshold I Sup.