MGVCL Exam Paper (30-07-2021 Shift 1)
Which type of connection is employed for current transformers for the protection of delta- star connected 3-phase transformer?
The connection of CT on primary and secondary side is always reverse to the connection of transformer. To protect the power transformer with star-delta against fault, the type of connection of CTs should be in the delta–star connection otherwise the relay will operate when an external fault occurs due to zero sequence currents
Two-part tariff: In this type of tariff, the total bill is divided into two parts. The first one is the fixed charge and the second is the running charge. The fixed charge is because of the maximum demand and the second charge depends on the energy consumption by the load.
Let, E→EMF in volt φ→Flux in weber A→Parallel path (for wave winding = 2) Z→No. of armature conductors N→speed in rpm P = Number of poles E = PφNZ/(60A) E = 8*0.020*625/(60*2) E = 500 V
Bus Type - Known Parameter - Unknown Parameter Load Bus -P, Q - V, phase angle Generator Bus - P, V (magnitude) - Q, Voltage phase angle Slack Bus Voltage - magnitude and phase angle - P, Q
Condition of good conductor: σ/ϵω >> 1 Equation is given by: The constant ratio = σ/ϵω = 44913.6 σ/ϵω >> 1. hence sea water is a acting as a good conductor Since attenuation is 90%, so transmission is 10% So, e^(-αx) = 0.1
Attenuation constant = √(σμϵ/2) = 0.702 -αx = ln(0.1) x = 3.27 m
EXAMIANS