Areva MiCOM P125, Technical Manual

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Application Guide P12y/EN AP/D32
MiCOM P125/P126 & P127 Page 23/74
2.4.3 Wattmetric (Pe) Characteristic
The P125, P126 and P127 relays include the zero sequence power measurement function.
They also offer the possibility to choose between a Wattmetric (Pe) protection and IeCos
(active component of the earth fault current) protection functionality mode.
The following figure shows the characteristic tripping zone for the wattmetric protection.
Pe> Pe>>
IeCos> IeCos>>
Pe/IeCos
Q/IeSin
5˚ 5˚
Tripping zone
P0365ENa
In the following formula the power thresholds in the relay menu are called Pe> & Pe>>.
The Pe> and Pe>> settings are calculated as:
Vres x Ires x Cos (f – fc) = 9 x Ve x Ie x Cos (f – fc)
Where:
f = angle between the polarising voltage (Vres) and the residual current
fc = relay characteristic angle (RCA/torque angle)
Vres = residual voltage
Ires = residual current
Ve
= zero sequence voltage
Ie = zero sequence current