In power tranformer and voltage above 750KVA
Mock Interview questions
Calculate the number disk in the insulator .Each disk can handle the 11kv
Number of insulator calculation for example 220 KV line .
Number of insulator =120/(11*root2)+1
so the Number of insulator :10
Here root2 for the insulation depends on the peak voltage
+1 for the more protection
lighting surge voltage:
when the electrical equipment like fan ,tv etc are on off . Over voltage transient surge can occur in the AC power lines .Near by any lightening strike on the transmission line .Nearby lightning strikes can also generate transient surges in AC .
switching surge voltage:
when the sudden interruption in any circuit surges will produce .Switching surge is sudden hike in voltage level because of switching.When switching is done suddenly, there is increase in voltage for some seconds.You can see when heater is switched off, voltage surge occurs and there is change in brightness of bulb for second.
Harmonic voltages suppression
Provides low impedance to zero sequence currents
Less cost compared to Scott transformer
It provides perfect isolation between ground and component
EHV: Extra High Voltage transmission line .It will carries 345kv – 500kv
HVDC;High Voltage Direct current transmission line
Inverse definite minimum time rely .IDMT relay is operating inverse to the current carrying by it.its minimum time relay.
Minimising damage at the fault location
Maintaining power system stability
localising isolation to avoid wide spread disruption
fault clearance performance