4 Pole Rcd On Sports Lighting !help!

[Lukeyw]

Hi I have been asked to look at the lighting at my local sports centre. I been to look and the set up is as follows.

3ph supply TN-C-S to a 4 pole 63A RCD, This feeds two isolators that each feed 3 stantions either side of e pitch. The lights are 3x 2KW high pressure sodium lamps per stantion. So 18 all together.

The problem is this, the RCD trips if all lights are turned on, but only when they get to full load after about 15-20 mins. If one side is left off all is good. Now I have checked the RCD and all is fine with that, there is no neutrals on any of the installation after the cut out. My theory is maybe some functional earth leakage due to no neutral and the RCD is picking this up as a fault?? I'm a bit lost

Any help would be great

Cheers Luke

 

[kme]

Wait a minute here.

You`ve three lights up a pole - 2KW each, 6 poles.

How is the power split? Surely not TP to each pole?

Each lamp is a "standard" 230V, arranged with all their "neutrals" termed off?

Don`t like that. Problems if a lamp goes.....

Or is each pole SP, and brought back to the RCD?

Whats the OCPD design?

More info needed, methinks...

 

[Lukeyw]

You got 2 cables per phase coming off the load side of the RCD, they go to there designated terminal on each isolator.

So basically u got one side of the pitch (3 poles-9 lamps) on one isolator and one side on the other. 3ph up each pole and obviously each fitting is 230v.

It's wired as a balanced load so the RCD has a link between one phase and neutral. There are no neutrals anywhere in the installation after the DNO equipment.

It all comes on fine until the lamps warm up and then the RCD trips.

 

[SLIPSHOD & SLAPDASH]

New one on me, cant help you though.

Something is not correct in your description, without a neutral there is no 240V unless you have a centre tapped tranny somewhere.

 

[batty]

An insulation test would be the first step I think.

 

[Lukeyw]

I think I have some pics hold on guys ...

Done an IR batty and all came back fine even blasted 1000v down it

 

[SPECIAL LOCATION]

An insulation test would be the first step I think.

+1..

Irrespective of the supply type..

loading arrangements etc...

Basic tests first I would think...

Breakdown of insulation anywhere on the cables or at a fitting..

once under load...

possibly due to heat at a joint...?

or damp somewhere?

 

[Lukeyw]

+1..

Irrespective of the supply type..

loading arrangements etc...

Basic tests first I would think...

Breakdown of insulation anywhere on the cables or at a fitting..

once under load...

possibly due to heat at a joint...?

or damp somewhere?

They are all fine at 1stni thought RCD might be on its way out but all fine

 

[steptoe]

if, and its an if,

all was working fine beforehand,

and,

there is NO neutral,

then I can only think of a breakdown of the ballasts or otherwise once they get hot,

if the RCD is tripping then you have an imbalance,

Im really NOT happy about the no N set-up though, it just seems a half arsed way of doing it TBH, in my mind its just not right, there is no need for it.

 

[Lukeyw]

if, and its an if,

all was working fine beforehand,

and,

there is NO neutral,

then I can only think of a breakdown of the ballasts or otherwise once they get hot,

if the RCD is tripping then you have an imbalance,

Im really NOT happy about the no N set-up though, it just seems a half arsed way of doing it TBH, in my mind its just not right, there is no need for it.

Apparently the lights are a year old. They changed all the stantions and fittings and switchgear but left existing RCD and cabling to the lighting.

 

[SPECIAL LOCATION]

What is the actual rating of the RCD?

and what current does it actually trip at during testing?

 

[kme]

The lights are 240. Given the imbalances in the way the lamps warm up, some`ll get more - others less than their fair share. For resistive loads - its ok. Not so for inductive. Ramming as KV down `em for iso testing isn`t a really good idea, either, to be honest.

By the way - in your post above,  you mention isolators and RCDs - but NO mention of any OCPD.

The RCD isn`t working properly, in the way you describe. It wants to have a neutral, and expects to see one, for any returning current. If one phase is booted over to the neutral, the RCD isn`t fitted to mfrs specs. 

I`d be looking for an excuse to EDN the install, from your description.

 

[SPECIAL LOCATION]

Whatever the cause is......

There is a level of inconvenience caused by a single fault..

with "unwanted" tripping of RCD..

considering reg 314.1..

maybe the best next step is to split the individual stanchions with their own local RCD rather than one global RCD?

Another thought...

Are these metal stanchions..  big earthy structures?

bonded to your supply cables..

exporting your TN-C-S earth around the ground??

or even absorbing earthy currents back up from the ground through your RCD onto your supply earth? 

 

[ParkySparky]

2000w sports lamps are 400v these lamps will run off 2 phases that's why no neutral.

How would a 240v piece of equipment work with no neutral.

All sports ground lighting I have worked on is 400v lamps, igniters and ballasts.

You've already stated you have 2 phases going up each pole but no neutral! Think about it! They are not 240v fittings!

 

[Lukeyw]

What is the actual rating of the RCD?

and what current does it actually trip at during testing?

What is the actual rating of the RCD?

and what current does it actually trip at during testing?

63A 30mA and they trip at 25mA 1x 42mS 5x 14.8mS

 

[wozz]

Agree with parky, i bet they are 400v ballasts. is the control gear accessible? you maybe be able to smell the dodgy one before testing!

 

[kme]

Parky:

In post #3, the O/P states that he has THREE phases going up each pole - not two.

I do agree that the fittings might be 400V - the OP didn`t say. 

 

[wozz]

each pole serves three fittings, so you would need three phases up each one to balance the three fittings. No real experience of these but i think that would be all balanced in my head.

 

[stuartrw79]

Haven`t installed/worked on for a long time, but if memory serves me correctly, fairly standard set up is 3 ph supply via 3 pole MCB`s via contactors from whatever controls required Photocell/clock/switches etc supplied to each column.....sometimes multiple 3ph supplies depending on how you want them controlled i.e. half lighting 2 fittings per column 100 % 4 fittings per column depending on how many lanterns per column you have. This also makes sure that if you get a fault on any one circuit you never lose all the lanterns from the same column. At the bottom of the column you`ll have 3ph isolator/ isolators feeding DP MCB`s which in turn protect individual 400v Lanterns,

Did some EICR`s not so long ago for the MOD, Rugby pitches, and it’s not always easy to work out switching arrangements etc unless it’s clearly marked..

 

[Lukeyw]

I have got some pics i will post them in a bit and show u all the arrangement