# Power System/transformer question

Discussion in 'Homework Help' started by pppopey, Mar 24, 2012.

1. ### pppopey Thread Starter New Member

Sep 27, 2011
13
0
attached is the question i am trying to solve.

I do not know how to do per unit questions.

Part a) of the question ask to convert into per unit and then per phase equivalent circuit. I do not understand how to do it. Please guide.

Also, how to calculate the bus1 voltage?

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2. ### mlog Member

Feb 11, 2012
276
36
The values of voltage, current, VA rating, and impedance are expressed in a per-unit (p.u.) system, which is a percent expressed as a decimal. Usually the "base" of the system is a kVA and kV rating. From those, the base current and base impedance can be calculated. For single-phase systems and per-phase values, the per-phase kVA and line-to-neutral kV can be used as the bases. In your problem, you have been given the kVA rating and the kV value for the base.

Within any part of a system, the impedance must be expressed in the same p.u system. It may be necessary to convert from another p.u. system.