When looking at example 1.1 in Power System Analysis by Grainger I notice that the give the Apparent power equation to be S=VI*. In example 1.1 they use the apparent power calculated for S1 to be S1=V(-I)*. I believe this is because I has a direction that is different from the source convention of S1.
However for the problems at the end of the chapter when calculating S1 and S2 for problems 1.8-1.11 they do not use use a -I when calculating S1 but rather keep the positive value.
So my question comes in for a source when calculating the power when should you use S=VI* as opposed to S=V(-I)*? Is this determined by the sign conventions of the voltages and the currents?
How should the euqations be used so that you can use the rules that for P & Q greater then zero the circuit is absorbing real and reactive power while for P & Q being less than zero the circuit is supplying real and reactive power?
However for the problems at the end of the chapter when calculating S1 and S2 for problems 1.8-1.11 they do not use use a -I when calculating S1 but rather keep the positive value.
So my question comes in for a source when calculating the power when should you use S=VI* as opposed to S=V(-I)*? Is this determined by the sign conventions of the voltages and the currents?
How should the euqations be used so that you can use the rules that for P & Q greater then zero the circuit is absorbing real and reactive power while for P & Q being less than zero the circuit is supplying real and reactive power?
