This is about Protective Relaying. Please help me

Q4 a) b) (3) c) (3) What are the four communication technologies mainly used in pilot protections? What are the three working modes for Power Line Carrier Pilot Protection? If a distance pilot protection is the main protection for a transmission line and a distance protection works as the backup protection, when the backup protection is under maintenance, the main protection has to be stopped, why? If the differential relay for a pilot protection uses static setting value to avoid the possible maximum unbalance current, the sensitivity may not be enough. How can we utilize dynamic setting value to solve this problem? d) (10) Q4 a) b) (3) c) (3) What are the four communication technologies mainly used in pilot protections? What are the three working modes for Power Line Carrier Pilot Protection? If a distance pilot protection is the main protection for a transmission line and a distance protection works as the backup protection, when the backup protection is under maintenance, the main protection has to be stopped, why? If the differential relay for a pilot protection uses static setting value to avoid the possible maximum unbalance current, the sensitivity may not be enough. How can we utilize dynamic setting value to solve this problem? d)