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# high PSC?

Discuss high PSC? in the Periodic Inspection Reporting & Certification area at ElectriciansForums.net

#### LukeScotty

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Arms
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Did some testing and my readings on 3 phase psc was like 6.7Ka, is that normal? as I find it rather high? thats between 2 of the phases, whats the reasons for this? and is it the suppliers fault for it being so high, What is an average PSC reading on a three phase and single phase anyway?

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W

#### wayne

if it goes over max permissable for device(mccb) try bs88's as they have a higher Ka rating

S

#### Shakey

Luke

NO NO NO NO

repeat after me

NEVER TEST PSCC BETWEEN PHASES

most test meters operate on 230V. You have just banged 400V accross it. Not good.

Measure PSCC Line to Neutral as you would with single phase, then double it to get your three phase value.

Dont forget your PFC's are just mathematical evaluations of Ze or Z.

I = V/R

where I is PFC and R is Z or Ze

so for a Ze of 0.5 ohms for example I would be PEFC would be 460A

If you were to measure Z (between line and neutral) and use this value, it would give you PSCC, which would then be doubled for a threr phase system

Most 60898's i have seen are rated at 10KA so you are fine

W

#### wayne

some meters DO test phase to phase (metrel if memory serves)
and your right dont test at 230 across 400 bang new meter please!!

#### ian.settle1

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Mentor
Arms
Luke

NO NO NO NO

repeat after me

NEVER TEST PSCC BETWEEN PHASES

most test meters operate on 230V. You have just banged 400V accross it. Not good.

Measure PSCC Line to Neutral as you would with single phase, then double it to get your three phase value.

Dont forget your PFC's are just mathematical evaluations of Ze or Z.

I = V/R

where I is PFC and R is Z or Ze

so for a Ze of 0.5 ohms for example I would be PEFC would be 460A

If you were to measure Z (between line and neutral) and use this value, it would give you PSCC, which would then be doubled for a threr phase system

Most 60898's i have seen are rated at 10KA so you are fine
Most of AVO(MEGGER) you can test between phases go up to 440volts

S

#### Shakey

Most of AVO(MEGGER) you can test between phases go up to 440volts
Yes I agree Ian, some meters will, and some meters wont. And some people dont know the difference. So adopting the standard practice (as per GN3) of measuring phase to neutral and doubling the value to obtain equivalaent three phase value is a good deal in my book.

It GUARANTEES the meter aint gonna go pop!

W

#### wayne

phase neutral earth times2 works for me

C

#### CCRISP

pscc is done either with 3 leads or 2
if you are using 3 leads the black and green lead goes in the neutral and the red lead in the phases
take all 3 readings and then double the highest
if you look in guidance note 3 it say that in a 3 phase system the pscc will always be the higher than pefc because as a rule of thumb you double it

#### telectrix

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Mentor
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Esteemed
think he might have sorted it, 4 years down the line.

#### Test-Meter

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think he might have sorted it, 4 years down the line.

Hahahaha!!!!!! Let's hope so - I wouldn't want his invoice otherwise!!!

#### ackbarthestar

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Mentor
Arms
Yes I agree Ian, some meters will, and some meters wont. And some people dont know the difference. So adopting the standard practice (as per GN3) of measuring phase to neutral and doubling the value to obtain equivalaent three phase value is a good deal in my book.

It GUARANTEES the meter aint gonna go pop!
3-phase psc measurements aren't really that difficult. It strikes me that if you are live testing you should know how to use your instruments and know its limitations. (see GN3 for advice).

The old Robin loop testers will give you a firework display, without warning, if used to test 3-phase psc, but the newer Flukes, Meggers, and Metrels are usually Ok.

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