Grounded Generator - Neutral Solid

Hire someone qualified, (an electrician), to check out you system and answer your questions.

I can assure you that will be the predominant opinion on this forum.

If done wrong, someone could die, (like you).

http://www.imsasafety.org/journal/ma03/ma5.htm (based on the NEC)

This site will give you information regarding your question. It basically says that

1. if the generator has the neutral terminal grounded, then the transfer switch has to switch the neutral along with the phase conductors.

2. if the transfer switch does not switch the neutral then the connection of the neutral terminal to ground must be removed. The generator frame is bonded to the systems equipment grounding conductor(EGC). No exceptions. My terminology my be slightly different than you local code.
I hope this helps.

Here we do not have anyone as "qualified electricians"

every electrician has their own way of installing, no code at all, and no education.

but WHY

1. if the generator has the neutral terminal grounded, then the transfer switch has to switch the neutral along with the phase conductors.

whats wrong if we dont switch the neutral? whats the reason(not that the code says to, whats behind that)

because we so not use any gfci or rcd's

i asked many electricians and one said fine, one said generator will blow!

and one said the lineman on the pole will get shock over there,

It is safer to connect neutral to earth. Safer and would not harm any one nor your generator.

If you do not connect one lead of 1 phase Generator or neutral of 3 phase to earth - and if insulation of any appliance is weak and gets leaked to body of appliance - the fuse will not blow and isolate the appliance. Some one touches such appliance can get shock. Hence safer to connect always neutral of generator.

Also it is safer to always connect the neutral of load to neutral of supply one is using. That means when you are on public utility your load shall be connected to phase and neutral of utility.

Similarly when load is connected to Generator - both phase and neutral of generator shall be used.

Hence you need a 2 pole change over.

The OP doesn't state if the system is a separately derived neutral system.

The article you are refering to is in reference to whether a ground rod is required when using a portable generator.

The article does not state anywhere that the the generator neutral must be physically disconnected under any condition.

the generator is a big 100kva one and has 7 earth/neutral pits specially for that.

I cannot use a 2 pole changeover. only single pole as the essential load's neutral cannot be separated from non-essential load.

here every appliance which has a 3rd pin at its plug for earth gets earth from locally at the premises and not by the utility or the generator. it is always connected.

I understand

- It is 100kVA 3 phase and neutral DG Set.

- It is base load DG Set (No utility)

- You have 7 Numbers of earth pits.

Please ensure

- Distance between 2 adjacent earth pits is more than depth of the pits. (if the pits are constructed close by it is as good as one earth pit).

- Resistance to earth of each earth conductor is not more than 7 ohm. This way when you will connect all pits together - overall value or earth will be less than 1 Ohm. It is desirable to have overall earth resistance shall be 1 Ohm.

For 100kVA DG Set, at Xd" of 8%, maximum fault current is 1700 amps at 415V for first 3 to 4 cycles (60 to 80 m. secs), 800 A for next 100 to 200 m. secs and later 400A for 1.5 secs (400A for 3 Secs if the generator has PMG exciter).

For above currents size of main earth conductor shall not be less than 35 sq mm Cu minimum. Same size of earth conductor shall be used to interconnect all pits.

The earth bus of your distribution board and neutral of generator shall be connected to earth pits.

For safety - it is desirable to earth the neutral of generator directly at Terminal Box of Generator. Do not use any removable link or switch disconnect in this circuit.

You can install

1 pole switches in single phase loads (that means neutral will go directly to neutral of load).

3 Pole switches for 3 phase balance loads such as motors.

4 TPN- 3 phase & Neutral) pole switches in 3 phase heating load (if any)

yes, but the DG set is not owned by me and it is run by a joint community

i use only single phase loads

now

1 pole switches in single phase loads (that means neutral will go directly to neutral of load).

currently my electrician made a setup with a 2 pole transfer switch,

that

when it is on generator, the generator neutral and utility neutral join together.

essential load's phase is connected to transfer switch to switch between generator and utility

when onm utility, the generator phase and neutral is not used anywhere

when it is on utility, the generator neutral and phase are disconnected

yes, but the DG set is not owned by me and it is run by a joint community

i use only single phase loads. This is OK. For additional safety connect neutral of to earth of generator supply at premises of your house. This is called multiple earthing and increases safety.

now

1 pole switches in single phase loads (that means neutral will go directly to neutral of load). Yes

currently my electrician made a setup with a 2 pole transfer switch, No harm. You can keep 2 pole switches.

that

when it is on generator, the generator neutral and utility neutral join together. This will happen in 1 pole switches also unless you ask electrician to install 2 pole changeover in utility and DG supply. That means when you are on Utility you are using neutral of utility. When you are on Generator you are using Neutral of Generator.

essential load's phase is connected to transfer switch to switch between generator and utility when on utility, the generator phase and neutral is not used anywhere

when it is on utility, the generator neutral and phase are disconnected

This will happen in 1 pole switches also unless you ask electrician to install 2 pole changeover in utility and DG supply. That means when you are on Utility you are using neutral of utility. When you are on Generator you are using Neutral of Generator.

when i am on generator i am using half neutal of utility and half neutral of generator!

because they both are getting joined there, right?

Read IEEE Std 1100-2005 Recommended Practice for Powering and Grounding Electronic Equipment, and 142-2007 IEEE Recommended Practice for Grounding of Industrial and Commercial Power Systems.

Better yet: The IEEE 3000 Standards Collection

That will get you started on the right path.

It won't make you qualified, but may help with your education. Rather than just getting the right answer, you should understand why the answer is right.

What has not been asked and needs to be in order to give you a proper answer is...

Is the neutral at the incoming connection point of the utility tied to ground electrodes and is it bonded to the case of the distribution system? If not it should be...

After that point, outside and downstream of the service box, all non-current carrying components of your distribution system then need to be bonded back to that point.

This is your bonding system. It ensures an equipotential plane in your facility and serves as a return path for fault current back to the source to operate your over current devices. This protects your people from situations where there is a fault.

So... now you wish to add a generator where the neutral is bonded to the case and it is connected to 7 earth pits. What you need to do in this case is to disconnect the neutral going back to the service entrance by way of your transfer switch. Why?

If you leave two points of interconnection between the neutral and the grounding system you have a redundant path for fault current back to the source. This is a bad thing. The impedance difference in the two return paths can cause a voltage rise in one area of the bonding system relative to another area of the same bonding system, which is a very bad thing.

If you cannot break the neutral to ground connection at the generator, you must break the one going back to your service connection point from the utility. This was clearly shown in the diagrams provided by WarEagle.

Under both the Canadian code and the US code, there may only be one connection point between the neutral and ground on a contained system, which is what it sounds like you have. From what you said about the lack of code in your location... I would follow the requirements of the Canadian or the US code.

If this is not clear... please ask more question. Doing this wrong can kill people during a fault event on your system.

here no neutral is tied with a ground electrode.

sometimes it is done and the ground electrode is called as additional neutral.(not a ground)

the devices(3-prong outlets) get the ground separately from the ground rod pit by the customer, without any connection with the neutral.

so there is no generator earth or the utility earth. all earth is given by that ground pit irrespective of the source of power. of course the generator metal case is grounded at the generator.

"If you leave two points of interconnection between the neutral and the grounding system you have a redundant path for fault current back to the source."

how? as the ground is separate from neutral?

simple diagram diagram without any mcb's

At this point in the discussion, without a doubt your system is dangerous.

When powered by the utility source, with no local tie between the neutral and ground, you are using the earth return path back to the utility source for fault current for anything other than a line to neutral fault.

Tieing your ground pins on your receptacles to an earth pit that has no connection to the neutral inside your building provides nothing in the way of protection and I doubt that any of your breakers will operate on anything other than a line to neutral fault.

You say that the utility neutral is not tied to ground yet you show it as such in the diagram you supplied? You make no mention of a bonding system at all!

I wish you good luck, but at this point, my only further advice to you is to get a competent electrical engineer, who knows the local electrical customs and requirements, in to advise you. Your system is very dangerous.

That neutral of the Generator is to be earthed and the neutral from the generator also is to be taken to utility no doubt about it

you mean joining a earthed neutral of a generator to utility neutral

utility neutral is again earthed at my place

it would be safe if the neutral is connected to be used within your premises and need not to be connected the with system neutral(utility) other than your premises i.e not to be extended away than your area of load but a good grounding essential

i dont understand, could you give me a example?

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now my current setup is like the earthed neutral of generator gets connected to earthed utility neutral when the transfer switch is flipped to generator side

when this is done when power is available, the

EL light(earth leakage light)

rev (reverse flow of electricity from premises to grid) glows on the electricity power meter

the is occuring even without powering on the generator. happens simply if i flip transfer switch to generator side.

will give u a detailed diagram if u want

There is lot of confusion.

Make connections as per below diagram. I had modified your earlier circuit diagram and attached. In between I stopped reading posts regarding this subject. Noticed that again it has started. Pl follow connection scheme below and should not be any problem.

yea your diagram is correct BUT

a SEPARATE NEUTRAL WAS NOT pulled/put in the building's wiring/switchboard for each appliance(light,fan) everything has a COMMON neutral

That is not safe for utility personnel. Assume

- Utility has taken a shutdown to work on the feeder.

- Essential load is connected to DG set.

- Non Essential load is not connected but neutral is common between essential and not essential loads.

- If earthing of neutral of generator gets opened or loose by any reason, the neutral will start floating and will have any voltage between 415V and Zero.

- This floating voltage will be feed back to utility overhead/ cable conductor and any Workman working on feeder will get electric shock.

No Utility will permit or approve such wiring connections.

An alternative to take care of above disparity in common neutral is to use 3 pole switch instead of 2 pole switch and rout neutral of Utility via switch in such a way that Utility neutral is isolated when the load is switched over to DG Set. Pl see revised diagram.

but they will not even power down the neutral line as well

then in case of a non-grounded neutral of generator how can it be solidly connected to the utility neutral

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we have laid 2 extra earth pits for the neutral of the utility also(shown in diagram) to prevent such things from happening

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here before working on the main lines, we are not allowed to switch on our generators.

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the use of a 3 pole transfer switch suggested by you is a good idea, BUT

there are some heavy loads (2 AC's) and here such high current carrying maunal changeover(greater than 20A) is not available..

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another way is to switch off the main isolator before flipping the transfer switch to generator side