CALCULATION OF SUB-TRANSIENT, TRANSIENT, STEADY STATE REACTANCE – PART – 01

SUB-TRANSIENT REACTANCE Xd’’

It is the ratio of induced e.m.f on no load and the sub-transient symmetrical current.

SUB-TRANSIENT CURRENT

I’’ = Eo / Xd’’

TRANSIENT REACTANCE Xd’

It is the ratio of induced e.m.f on no load to the transient symmetrical r.m.s current.

TRANSIENT CURRENT

I’ = Eo / Xd’

STEADY STATE REACTANCE Xd

It is the ratio of induced e.m.f to the steady state r.m.s current.

STEADY-STATE CURRENT

I = Eo / Xd

Eo – is the r.m.s value of open circuit phase voltage.

Xd’’< Xd’ < Xd

APPLICATION OF Xd’’ AND Xd’

SUB-TRANSIENT REACTANCE Xd’’

It is used for determining the interrupting capacity of the circuit breaker.

TRANSIENT REACTANCE Xd’

It is used for relay setting and coordination.