Figure 33: Directional Angles - GE MiCOM P40 Agile Technical Manual

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Chapter 6 - Current Protection Functions

Residual voltage is nominally 180° out of phase with residual current. Consequently, the DEF elements are polarised from the

"-Vres" quantity. This 180° phase shift is automatically introduced within the device.

The directional criteria with residual voltage polarisation is given below:

Directional forward

(Ð VN + 180°) + RCA - 90° + (180° - tripping angle)/2 < Ð IN < ( Ð VN +180°) + RCA +90° - (180° -

tripping angle)/2

Directional reverse

(Ð VN + 180°) + RCA - 90° - (180° - tripping angle)/2 > Ð IN > ( Ð VN +180°) + RCA +90° + (180° -

tripping angle)/2

This can be best visualised with reference to the following diagram:

Figure 33: Directional angles

Some of the models derive the Residual Voltage quantity internally, from the 3-phase voltage input supplied from

either a 5-limb or three single-phase VTs. With some models (those with no Check Synchronism function) the

voltage transformer may be used to measure the Residual Voltage VN. This gives a more accurate result than with

derived voltage.

P14D-TM-EN-8