Areva MiCOM P441, Technical Manual

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Application Notes P44x/EN AP/E33
MiCOM P441/P442 & P444 Page 85/220
•
When protecting solidly-earthed distribution systems or cable feeders, a -45
°
RCA
setting should be set.
•
When protecting solidly-earthed transmission systems, a -60
°
RCA setting should be
set.
2.17.3 Application of Negative Sequence Polarising
In certain applications, the use of residual voltage polarisation of DEF may either be not
possible to achieve, or problematic. An example of the former case would be where a
suitable type of VT was unavailable, for example if only a three limb VT were fitted. An
example of the latter case would be an HV/EHV parallel line application where problems with
zero sequence mutual coupling may exist. In either of these situations, the problem may be
solved by the use of negative phase sequence (nps) quantities for polarisation. This method
determines the fault direction by comparison of nps voltage with nps current. The operate
quantity, however, is still residual current.
When negative sequence polarising is used, the relay requires that the Characteristic Angle
is set. The Application Notes section for the Negative Sequence Overcurrent Protection
better describes how the angle is calculated - typically set at - 45°
(I
2
lags (-V
2
)).
2.18 Aided DEF protection schemes
The option of using separate channels for DEF aided tripping, and distance protection
schemes, is offered in the P441, P442 and P444 relays. When a separate channel for DEF
is used, the above DEF schemes are independently selectable. When a common signalling
channel is employed, the distance and DEF must Share a common scheme. In this case a
permissive overreach or blocking distance scheme must be used. The aided tripping
schemes can perform single pole tripping. The relay has aided scheme settings as shown in
the following table:
Menu text Default setting Setting range Step size
Min Max
GROUP 1
AIDED D.E.F.
Aided DEF Status Enabled Disabled or Enabled
Polarisation Zero Sequence Zero Sequence or Negative Sequence
V> Voltage Set 1V 0.5V 20V 0.01V
IN Forward 0.1 x In 0.05 x In 4 x In 0.01 x In
Time Delay 0 0 10s 0.1s
Scheme Logic Shared Shared, Blocking or Permissive
Tripping Three Phase Three Phase or Single Phase
FIGURE 47 - MiCOM S1 SETTINGS