Favourite Phases

"Red is hot, Yellow is cowardly,
and Blue is decidedly cold"

You laugh! Open up a distribution board and see just how badly the phases are unequally loaded - and it is purely psychological. Ok, maybe it's not always so, as there are times that other beliefs get in the way, such as the one held by some audio-visual guys thinking all related AV gear must run on the same phase - coming from a bad practice of not wiring up the referenced ground equipment properly. The result is, however, the same.

This thinking carries a significant danger - and the higher the output power of the gear, the higher the danger. Large pulses of current on a single phase of a 3-phase supply will pull the Neutral toward the loaded phase causing a lower voltage on this phase and a corresponding higher voltage on the other two phases. Not only is the voltage in question, but also the harmonic content which is now shared with the other phases.

It is still my firm belief that this is what caused the fire in Buckingham Palace when the musicians were practicing for the the "Party At The Palace" as part of the 50th Jubilee celebrations. No-one has confirmed this, but no-one is denying it either! Until I get a chance to prove it otherwise, I will hold firm to this thought.

It starts becoming obvious what the cures are, the first is to remove the references! Their only purpose in life is to offer some means to reduce the noise that can exist on some pieces of entertainment appliances. But, something needs to then take the place of the referenced grounds. We cover this later.

Till now we have only spoken of low voltage distribution but the favourite phases continues into the lower order HV side too. It does, however, have a unique twist.

This has more to do with rural distribution networks where the typically 11kV lines are spread in a triangular shape with two phases forming the base, and one the apex. When installers come along to put in a single phase rural domestic transformer there is a serious dislike of wanting to connect anything to the upper phase, and nearly everything thus lands up being connected to the two phases forming the base of the 'triangle'.

During the day, while industry loads the line, the phases remain relatively balanced. Come night time, when the load is predominantly rural domestic, the two lower phases, red and blue, are loaded to the extreme while yellow soars above them. This leads to imbalance deluxe, and everything that works with three phases now taking some serious strain (that's if it does not give up working all together!).

Miniature Neutrals  >>

| | Ask a Question |

© 02.02.03