GE MiCOM P40 Agile Technical Manual

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Application Notes P44x/EN AP/Hb6MiCOM P40 Agile P442, P444 (AP) 5-45residual current on the parallel line is measured. It is extremely important that the polarity ofconnection for the mutual CT input is correct, as shown.The system assumed for the distance protection worked example will be used here, refer tosection 3.3. The Green Valley – Blue River line is considered.Line length: 100 kmCT ratio: 1 200 / 5VT ratio: 230 000 / 115Line impedances: Z 1 = 0.089 + j0.476 = 0.484 / 79.4° Ω/kmZM0 = 0.107 + j0.571 = 0.581 / 79.4° Ω/km (Mutual)Ratio of secondary to primary impedance = 1200 / 5230000 /115 = 0.12Line Impedance = 100 x 0.484 / 79.4° x 0.12= 5.81 / 79.4° Ω secondary.Relay Line Angle settings 0° to 360° in 1° steps. Therefore, select Line Angle = 80° forconvenience.Therefore set Line Impedance and Line Angle: = 5.81 / 80° Ω (secondary).No residual compensation needs to be set for the fault locator, as the relay automaticallyuses the kZ0 factor applicable to the distance zone which tripped.Should a CT residual input be available for the parallel line, mutual compensation could beset as follows:kZm Mutual Comp, kZm = ZM0 / 3.Z 1 Ie: As a ratio.kZm Angle, ∠kZm = ∠ ZM 0 / 3.Z 1 Set in degrees.The CT ratio for the mutual compensation may be different from the Line CT ratio. However,for this example we will assume that they are identical.kZm = ZM0 / 3.Z 1 = 0.581 / 79.4° / (3 x 0.484 / 79.4°)= 0.40 / 0°Therefore set kZm Mutual Comp = 0.40kZm Angle = 0°