equivalent THDv

[laurent13]

Hi,
I have 2 transformers on which I could measure THDv on the LV side. 1% on 1st transformer (2.5MVA), 2.1% on the second one (2MVA).
Both Transformers are supplied by the same 13.2kV switchgear
Is there an easy way to calculate the equivalent THDv on the 13.2kV side?

Thanks

 

[Skogsgurra]

No.

I assume that those two transformers have nothing more in common than the primary voltage. And that they are loaded. The load is what determines THDV to a great extent, probably around half of the THDV contribution is from the load. The only thing you can say for sure is that the 13.2 kV THDV is less than 1%

Aren't there any PT:s on the 13.2 kV side? It is an easy matter to measure there. My guess is that you wil see around .5%

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[laurent13]

Thanks

Yes, transformers are loaded (40% for 1st one, 50% for 2nd one) and supply different gears, so as you said, nothing in commom except primary voltage. Unfortunately, no meters on the 13.2kV side....

My guess is less than 1%, but I was wondering if any calculation method (even approximation) exists.

 

[krisys]

You may review what are loads?

Are there predominantly non-linear loads (such as UPS, VSD, thyristor controlled heaters, Fluorescent lamps etc.)in the transformer which has 2.1% THD?

As such 2.1% at 415V is not a THD level which is a cause for any concern as the tolerable level is much higher.

 

[waross]

Could part of the harmonic distortion be originating on the supply grid?

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[laurent13]

Sorry, I was away a few days.
Loads are mainly motors driven by VSD.
I'm not really concerned by the value itself, as it remains under 3%.
My concern was to try to calculate the value on the 13.2kV side. But it seems clear we can't.
Thanks

 

[krisys]

As far as the %ge harmonic current distortion is concerned, it is same at 415V and 13.2kV side.