Lost Grey Zs

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seajayess

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Have been testing a factory, 2 DB fed from a TPN supply via an isolator up till today all circuit on the 2 boards have been OK. But today lost the Zs on the Grey phase on both boards but still had 230/400 volts,Zs OK on Brown and Black. DB boards mounted on a freezer type of wall with a door beside them, the door slammed shut, Grey Zs back. Thinking bad connection I have tried all the connections and they are all tight. Now Zs on the Grey phase is less than Brown and Black, I have worked out the readings and the Grey phase is about correct and the Brown and Black are on the high side Grey Zs 0.02 ohms Brown and Black 0.13 ohms hope this makes sense CJS ?:|

 

benji

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any signs of overheating on grey connections /possible cross thread on connections ie. it feels tight but it's not got the core

yours benji

 

seajayess

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No signs of over heating and all connections are tight nothing loose CJS

 

greensparky

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HI mate I am only a novice and hope you will not mind me putting in my two penneth,

I presume all your Ze readings are ok. so you have a problem with your R1,R2 on brown and black, is that rite,

can you do any dead testing ? to test your R1 on your phases. Is there any fixed equipment that is single phase taken off the grey. ie some lighting or any thing wired two phase off brown and black. Could this not give you a fulse reading,

I have only heard about 2 phase never seen it .

 
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Mr. Green:

All the Ze readings? There is only ONE Ze per installation.

You may have been thinking Zs - which the poster was talking about.

This is 3 phase mate - not 2.

CJS:

Any possibility of a cable biting insulation at a termination? other than that, I`d want to check anything connected upstream of your testing position, for (maybe internal) loose connection(s)

? main switches on the DBs

 
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It IS a valid supply type, mate.

There are two variants:

1. Where two seperate supplies are fed to a property; but they`re both from the same phase. Not Strictly 2 phase, though. Used where max dem for domestic is higher than a single supply can deliver.

2. Where a 2 or 3 wire (with/without neutral) is fed to (usually agricultural) property; where they may need a 400v supply; but do not require full 3 phase. Generally unusual; but it does exist.

HTH

KME

 

greensparky

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Glad you found your lost Zs,

KME please bare with me I am here to learn please explain, I thought on 3 phase you took Ze on all three phases but used the highest for your calculations, what i was trying to point out was any discrepancies on the three incoming cables.

 

greensparky

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Glad you found your lost Zs,KME please bare with me I am here to learn please explain, I thought on 3 phase you took Ze on all three phases but used the highest for your calculations, what i was trying to point out was any discrepancies on the three incoming cables.
 
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