Slopes And Thresholds - GE P741 Technical Manual

Commissioning
MiCOM P741, P742, P743
I is fixed to a lowest value of ID>2/k2 and IDCZ>2/kCZ, the Az and Acz points will thus be
bias
ID>2 and IDCZ>2. So I
To test the slopes:
I is fixed to a value greater than ID>2/k2 and IDCZ>2/kCZ the Bz and Bcz points will thus
bias
be I x k2 and I
bias
When we reach the point Xcz the Central Unit LED 8 and relay 8 will operate and when we
reach the point Xz the differential element will operate.
To calculate the slope k, k = (I
The differential current will increase twice the value I.
Note 1:
Note 2:
6.3.1.2

Slopes and thresholds

If a LED has been assigned in central or/and peripheral units to display the trip information,
these may be used to indicate correct operation. If not, monitor option will need to be used –
see the next paragraph.
On P741 go Central Unit GROUP1-->BUSBAR PROTECT and set I
On P742/3 go to COMMISSION TESTS column in the menu, scroll down and change cells
[Monitor Bit 1] to [BUSBAR_TRIPPING]. Doing so, cell [Test Port Status] will appropriately
set or reset the bits that now represent BUSBAR_TRIPPING (with the rightmost bit
representing Busbar Trip. From now on you should monitor the indication of [Test Port
Status]. Make a note of which elements need to be re-enabled or re-set after testing.
Test of I >2:
D
I >1 Alarm Timer should be set to 100s during testing.
D
Inject a I current smaller than I
2
Test of the operating time of the differential element:
Inject a I current greater than twice I
2
differential element.
Test of I >1:
D
I >1 Alarm Timer should be set to 100ms.
D
Inject a I current smaller than I
2
Alarm of LED circuitry fault).
Test of I >1 Alarm Timer:
D
I >1 Alarm Timer should be set to 5s.
D
Inject a I2 current greater than twice the I
Alarm is coming in 5s.
Note: Same tests can be applied for the Differential Sensitive Earth Fault Protection.
Note: the Sensitive Differential Earth Fault (SDEF) is 20ms delayed and controlled by a
settable threshold I
phase currents.
IMPORTANT NOTE: Check that if the SDEF is enabled, all the CTs are of the same
= I + I = fixed value (Points A)
bias 1 2
x kCZ. So I = I + I
bias bias 1 2
– I ) / (I + I
1 2 1
I >1 alarm timer will be set to 100s during the test.
D
Whenever possible, inject 2 × I
must be higher than 1.7 × I
order to ensure a 15ms tripping time
>2 and slowly increase I
D
>2 threshold and measure the operating time of the
D
>1 and slowly increase I
D
ph> to unblock/block the sensitive element depending of the restrain
bias
standard.
= fixed value (Points B)
)
2
>2. Alternatively, the minimum current
D
>2 at 60Hz and I.42 × I
D
D
until tripping.
2
until circuit fault appears (LED
2
>1 threshold and check that the Circuitry Fault
D
P74x/EN CM/Na7
(CM) 10-29
>2 at 50Hz in
D
>1 Alarm timer to 100s
CM