Neutral Grounding

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Read http://www.eon-uk.com/distribution/CiCdocs/01%20Technical%20Documents/CN%20Combined/Earthing%20Manual/E2%20Earthing%20Manual%20Earth%20Guidance%20Notes.pdf

I'm not positive if this will effect you or not, but here is an issue I have ran into with grounding neutral in the past.

I was doing research in college and was building a high voltage pulser. With solid state pulsers you get a lot of swing on the ground. It'll jump high, or go low for nanoseconds at a time.

The circuit worked fine, but when we connected it to a power source that was operating on a Groung Fault Circuit Interupter breaker type (GFCI) the breaker would trip every time we pulsed it because of that swing.

Aside from tripping breakers on certain power outlets the circuitry worked just fine, and the grounding of the neutral added a bit of stability to our design. Just a thought for you.

Two-phase electric power was available in the US in the late 19th and early 20th centuries. It is no longer available, because three-phase distribution is less expensive and works as well as two-phase for starting and running induction motors, which was the reason for its introduction.

It is a mistake to call center-neutral 240-volt electric power two-phase. It is single-phase. The two legs of this distribution are opposite in polarity, but there is no phase difference. An induction motor supplied from this source requires a circuit to produce a rotating magnetic field or some other means to initiate rotation.

Yeah, we don't use no stinkin' two-phase power here, we use 'dis:

http://en.wikipedia.org/wiki/Split-phase_electric_power

I agree with the preceeding note. There is no 2 phase system in existence I know. There are three phase systems in the industrial world, and then there is a single phase system - not necessary, IMHO - for domestic use. Two phase you referring to is a center tapped single phase. You cannot derive rotational information from it.

Since the YND11 means you have the Star conntion configuration on the primary side, then the Neutral Point is the centre of the star and it can be grounded for the purpose of checking against ground fault. You must make the star point first to avoid having circulating current in the ground from transformer to transformer!

Mind you, this Ground will not be valid for the Delta side circuitry.

GA

SR79 question: Star-point before or after grounding?

BRZK answer: If you have a grounding mat and a grounding system which rely all metallical parts of your installation, you can ground each neutral separately (Your grounding total resistance must be lower than 1 ohm, when your 3 neutrals are NOT connected, and they must be connected on the same close part of your grounding system or your grounding mat). If you are not sure of your grounding system or if that one is not practically under view, don't do that.

In that case, rely all the 3 neutrals in only one upper point, then go down to grounding system and deploy another time the 3 neutrals in 3 different directions (like a goose leg), on about 9 buried meters (at least 80 cm under surface) for each different leg of the 'goose leg', with a grounding pit and a grounding tube (of 3 meters of depth, at least, at each extremity). You are on HV side Yn. On LV side D11 you have no neutral out. D11 is a manufacturer shifting time-clock index. It depends really of the true time index of your generator, or of your upward source. If you don't have any generator upward your transformer, then your time-clock index, on LV side is really D11, starting from your transformers. You, then will not have any neutral distributed (This will necessited an ancillary transformer each time you will want to supply some lighting, for instance).

You can install a differential relay between each phase, the commoned HV neutrals and each phase on LV side, for a better protection. All neutrals, all metallical parts of all transformers HV and LV sides included must be relied on the same grounding system, in any case, except if you want a transformer tank protection.

In that case, each neutral and its relevant tank must be separated and all pieces and devices on EACH same tank must go down on 3 different straps to earth (with a C.T. at each grounding strap). In that case only (a transformer tank protection), you must not commoned the 3 neutrals on a goose leg. Also, this is the best surge and lightning economical protection for each transformer.

All connections in relation with a grounding of neutral must be in bare copper (I suggest, at least 70 sq.mm) with necessited grounding supports and clamps (carefull to steel/copper contacts _In that case, use only stainless steel with copper).

I hope this wil be simple and efficient enough for you, BRZK.