The main function of an interposing CT is to balance the currents supplied to the relay where there would be an imbalance due to the ratios of the main CTs.
Interposing CTs are equipment with a ratio that can be selected by the user to achieve the balance required.
An interposing CT is installed between the secondary winding of the main CT and relay.
India ranked 4^th in the Global Wind Power Installed Capacity index with cumulative installed wind power generation capacity of 25088.
Wind power generation capacity in India has significantly increased in recent years. As of 28 February 2021, the total installed wind power capacity was 38.789 GW, the fourth largest installed wind power capacity in the world.
The neutral point of a generator is usually earthed to facilitate protection of the stator winding and associated system.
Earthing also prevents damaging transient overvoltages in the event of an arcing earth fault or ferro resonance.
For HV generators, impedance is usually inserted in the stator earthing connection to limit the magnitude of earth fault current.
Frequency response analysis is the technique whereby a sinusoidal test signal is used to measure points on the frequency response of a transfer function or impedance function.
Sweep Frequency Response Analysis (SFRA) testing provides insight into the mechanical and electrical integrity of transformers.
Main Purpose of SFRA Test:
Transformer Core displacement
Winding displacement for both rotor and transformer
Broken or loosen clamp connections
Inter turn short circuit
Internal short circuit
Winding to Core Earth fault
Winding Open circuit condition
Slip, s = (Ns - Nr)/Ns
Ns = 120f/P
0.05 = (1000 - Nr)/1000
Nr = 950 rpm
Speed of rotor with respect to stator magnetic field = 950 - 1000 = -50 rpm
Speed of the stator magnetic field with respect to stator core = 0
Speed of the rotor magnetic field with respect to rotor = sNs
Speed of the stator magnetic field with respect to rotor magnetic field = 0
Speed of the rotor magnetic field with respect to stator core = Ns
ω = 500 rad/sec = 2πf.
At Resonance condition,
ωL = 1/(ωC)
L 0.2 H
Also at series resonace
1. fr = 1/[2π√(LC)]
2. PF = 1
3. Maximum current
4. Source voltage = voltage across resistor.