Answer / balasubramanian

CT PT ratings are decided on
1. Class : Protection, metering (for CT)
2. Burden: The load of relays, cabling, etc.
3. Fault level: The thermal capacity of CT for bearing the
fault current for required time 1 sec, 3 sec etc.
4. The voltage level of the system

Answer / pradeep kumar

ct decied as per metering OR protection ct Use ct as per
metering that we can use the metering instrument of panel
OR control room 1A OR 5A

Answer / d.durga prasad

In CT

CT primary rating will be decided by its load current &
secondary will depend up on purpose of of selection (either
metering or protection )

In PT

It will always depend upon its system rating & in secondary
the class will be depend upon its purpose of its
utilization as same as in the CT secodary. but the voltage
level is always 110V in secondary of transformer.

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