Note: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)/2Directional reverse(Ð VN + 180°) + RCA - 90° - (180° - tripping angle)/2 >Ð IN > (Ð VN +180°) + RCA +90° + (180° -tripping angle)/2This can be best visualised with reference to the following diagram:V00748VN VNINFigure 33: Directional anglesSome of the models derive the Residual Voltage quantity internally, from the 3-phase voltage input supplied fromeither a 5-limb or three single-phase VTs. With some models (those with no Check Synchronism function) thevoltage transformer may be used to measure the Residual Voltage VN. This gives a more accurate result than withderived voltage.Chapter 6 - Current Protection Functions P14D100 P14D-TM-EN-8
