In the circuit of figure, the switch is closed to position-1 for a long time. At t = 0 the switch position is changed from postion-1 to postion-2. Find an expression for the current i(t).

Standard eqution of current for this condition,
i(t) = i(0+)*cos(wt)
i(0+) = E/R
For LC circuit,
w = 1/√(LC)

i(t) = (E/R)*cos((1/√(LC))*t) A

The magnitude of the generator earth-fault current is limited by

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.

If all the devices are connected to a central hub, then the topology is called

Which one of the following statement is TRUE?

In the cables, the location of fault is usually found out by comparing the capacitances of insulated conductors.

Consider the following statements associated with Buchholz's relays.
Statement 1: Buchholz's relay is a current operated device.
Statement 2 : Buchholz's relay is placed between the transformer tank and the conservator.

Buchholz relay is gas operated relay.
It will operate when internal fault occurs in transformer.
It is placed between tank to main conservator.
It has two contacts trip and alarm.
Use of Buchholz relay in distribution transformer is not economical.

The voltage applied to a transformer primary is increased keeping V/f constant. With this, the core loss ____ and the magnetizing current (Im) ____

For trasnformer:
1. e = 4.44fφ*Turns
2. V/f ≈ e/f ∝ φ ∝ B
3. Eddy Current loss, Pe ∝ B²f² ∝ f² (as B is constant if V/f is constant)
4. Hysteresis loss, Ph ∝ B^1.6*f ∝ f
If V/f is constant, B is constant, mmf required to create B is constant, Im is constant.