(Solved): Q7 A biased differential protection scheme employed for a 25 MVA 69 kV/13.8 kV transformer is show ...

Q7 A biased differential protection scheme employed for a 25 MVA 69 kV/13.8 kV transformer is shown in Figure 27. (a) Assess the sensitivity of the relays when the transformer is operating under normal condition Assume the pickup current of the relay is 200 mA (6) Devise and draw the CTs configuration if the relays maloperated. Show that the relay is not maloperated after reconfiguration of CTs arrangement. Assume both CT1 and CT2 have the following ratios. CT2=250:5 A CT1=721.68:5 A UU A 0 woon A B AR un B ww c WIN W ? RC 000 100 I RC mer 1 RC 000 w OC oc SOC Biased Differential Relays Figure Q7