3 phase voltage difference...

[Dane]

Im quite bored this morning, so i thought id get my tester out and go practice on 3 phase in my unit!! (dont normally do 3 phase)

Set tester to phase rotation

All correct

But what im unsure about is

it says on tester

L1 408v

L2 408v

L3 401v

Why 7v loss?

I carried out the phase rotation test at the Main isolator also, so closest point to meter

Just curious

 

[Andy™]

L3 to what?

 

[Lee321]

[quote name='Andy

 

[Andy™]

yes, but it still doesnt make sense

 

[Lee321]

could be a large load on that phase on neighbouring units dragging it down

maybe

 

[Dane]

My tester just put all 3 leads one to each Phase

There was no load what so ever with neighbouring units. as we are the only unit on there.

The main line is around 4m away with the big transformer on, our cable comes down from that under about 4m of ground then up into the unit.

Like i say, i do little 3 phase, and was bored so thought id go have a look.

 

[RussellR]

The Route the Phase takes could be potentially be marginally longer, so you would get additional volt drop on that phase. It is not unusual to see minor differences in the Loop impedances across three phase as the earth path is the same for all, it can only be that there are variations in the resistances of the Line Conductor.

 

[Dane]

The Route the Phase takes could be potentially be marginally longer, so you would get additional volt drop on that phase. It is not unusual to see minor differences in the Loop impedances across three phase as the earth path is the same for all, it can only be that there are variations in the resistances of the Line Conductor.

Over such a short distance...this is quite a large drop though?

The corner of the unit, is exactly 4m from the pole.

It drops from the pole, underground (now 2m under) we built it up.

So roughly 12m of cable in total from the Pole.

Cant see there been that much drop over such a short distance?

 

[RussellR]

Over such a short distance...this is quite a large drop though?The corner of the unit, is exactly 4m from the pole.

It drops from the pole, underground (now 2m under) we built it up.

So roughly 12m of cable in total from the Pole.

Cant see there been that much drop over such a short distance?

True that is a fair drop on what are presumably large CSA cables , Meter ?, or meter lead ?

 

[Andy™]

Im quite bored this morning, so i thought id get my tester out and go practice on 3 phase in my unit!! (dont normally do 3 phase) Set tester to phase rotation

All correct

But what im unsure about is

it says on tester

L1 408v

L2 408v

L3 401v

Why 7v loss?

I carried out the phase rotation test at the Main isolator also, so closest point to meter

Just curious

thinking about it a bit more, you dont have a 7v loss on one phase. 2 phases must be lower than the third

 

[Dane]

This Mornings results were

L1 - L2 408v

L2 - L3 408v

L3 - L1 401v

I took them at the isolator with the isolator in the off position.

Ive just been out again now, as its bugging me.

and ive had some different results.

L1 - L2 418v

L2 - L3 417v

L3 - L1 413v

Metrel Tester, in calibration, new. New leads.

Is there any chance that the main lines got that much of a load on it some where that it effects our property?

 

[Andy™]

those readings suggest L2 is higher than L1 & L3. can you get a reading between each phase to neutral, and each phase to earth

a high load on any transformer will effect everyone else on that transformer

 

[Dane]

[quote name='Andy

 

[Andy™]

heavy load on the 11KV to the tx could cause volt drop, but its unlikely to be that

 

[Dane]

Here we are

L1 - Neutral 236v

L1 - Earth 236v

Showing 53hz

L2 - Neutral 235v

L2 - Earth 235v

51hz

L3 - Neutral 235v

L3 - Earth 235v

51hz

I am leaving test probes on long enough to be sure its settled aswell.

Im just curious about this one. Again no load on the aboves, Main isolator off and test on incomer.

Edit - Not going in there again tonight, too friggin dark when isolators off :^O

 

[RussellR]

Have you tried swapping the positions of the leads to see if the difference moves around ?