The phase sequence (or phase rotation) of the three phases of the generator must be the same as the phase sequence of the three phases of the electrical system (Grid). The only time that the phase sequence could be wrong is at initial installation or after maintenance. There are two possible problem sources.
The phase rotation is A-B-C. You can’t determine phase rotation with a phasor diagram unless you know the one universal rule in the relay testing world. ALL PHASORS ROTATE COUNTER-CLOCKWISE. The video below shows you how the waveforms and phasors inter-relate. Media error: Format (s) not supported or source (s) not found
Check Phase Sequence:Using phase sequence meter , ascertain that the two sources have similar phase sequence, either both having ABC sequence or both having ACB sequence. Check Phase Angle: Measure the potential difference between the respective phases that is going to be paralleled.
As previously mentioned, the phase angle between the voltage produced by the generator and the voltage produced by the grid must be zero. The phase angle (0 to 360°) can be readily observed by comparing the simultaneous occurrence of the peaks or zero crossings of the sinusoidal waveforms.
Phase rotation or phase sequence is a concept that is not well understood and misapplied in many installations. Lets dive in to what is this ‘Phase Rotation’ as is referred to in 3 phase electrical systems. Here are the some keys points to note: Phase rotation/ Phase Sequence is important in the following applications
Phase Sequence The phase sequence (or phase rotation) of the three phases of the generator must be the same as the phase sequence of the three phases of the electrical system (Grid). The only time that the phase sequence could be wrong is at initial installation or after maintenance.