3 Phase PSCC

[disinfo]

Good Morning,

My test meter does not allow me to measure between two phases of a 3 phase supply for determining PSCC.

I understand that the thing to do is test between each phase and neutral and then double the highest value to reach the PSCC (PFC in a 3-Ph as it will be the highest)

But...

How do I determine the PSCC on a supply that has no neutral, such as one that is supplying a load of 3 Phase motors.

Many thanks

 

[Electrifying]

Is there no neutral incommer at all?

What earthing system is it?

 

[ricicle]

The highest PFC will be at the origin where you should have the Neutral, unless you have a special set - up (eg phase shifting transformer)

 

[FDJ]

How do I determine the PSCC on a supply that has no neutral, such as one that is supplying a load of 3 Phase motors.

Many thanks

Are you sure there is no neutral?
Do the motors have star/delta starters?

Frank

 

[Spark123]

If you have no neutral and your tester won't do P-P then do a P-E and double it.

 

[ericmark]

Top of range meters will measure phase to phase and if you really need the reading then hire a meter.
The other method is to measure where you have got a neutral then use R1 measurement to calculate the PSCC as one does with new installation before power is available.

 

[Electrifying]

If you have no neutral and your tester won't do P-P then do a P-E and double it.

That could give you a figure that's miles out - that's why I asked him what the earthing system was first

 

[disinfo]

Thanks for the replies guys,

I think I was a little vague with my original post.

We are installing a line of Hydraulic presses at a well known lighting manufacturer, their guys or rather their sub-contractors did the armour installation and connection to my panel.

We fill out our own test sheets as part of the technical manual, I would generally have the PFC value given to me but the data isn't available at the moment.

Anyhow, I measured Earth loop impedance at the isolator to be 0.29 and doubled the PEFC as per Spark123's suggestion which gave me something like 1.6kA, it all became a little academic really when I realized the ferraz fuses in the panel have a 120kA breaking capacity.

Maybe its time to get a tester that can do 3ph PSCC as eric has said.

Cheers

 

[RF Lighting]

You could hire mine. You only live round the corner from me I think

 

[disinfo]

You could hire mine. You only live round the corner from me I think

Funny you should say that, there is a "secure hospital" just up the road!!!

 

[RF Lighting]

 

[disinfo]

I know how you feel.

The missus says its where I'll be living soon

 

[Adam_151]

Thanks for the replies guys,
Maybe its time to get a tester that can do 3ph PSCC as eric has said.

If you are looking at upgrading your loop tester and funds can stretch, then I'd highly recommend looking at the megger LTW series, but by far the most friendly to use I've ever come across