THD in 20 kV side of 20/0.4 kV Transformer, 3000 kVA, Dyn-5, Year 2019

[JonoJakarta]

Dear expert,

I found in THD our PM5500 meter on our SM6-24 switchboard showing around 50%-52%, I was surprised.
Is this coming from load side (LV/0.4 kV) or on HV side?
Then, I switch off ACB on LV side of Transformer , it's mean our transformer on no-load condition
I checked PM5500 meter on our SM6-24,there is showing THD still there but decrease to 45%-48%, current 689,86 mA, Voltage, 20.4 kV.
My question:

1. Why is there still THD on the HV side(20 kV) even though the LV side is off/no load?
2. What is caused?
3. Is the transformer on healthy condition?

Any comments are welcome.
Your prompt reply will be highly appreciated.

Thank you,
Best Regards,
Jono

 

[bacon4life]

Are you measuring THD in current or voltage? THD measurements in small amounts of current may not have much practical meaning.

 

[scottf]

Where is the current and voltage input to the 20kV side meter coming from? Traditional CTs and PTs? Do you know what their frequency response is?

 

[JonoJakarta]

Dear bacon4life,

THD in current

Dear Scottf

I think traditional CTs and PTs, There is not mention the manufacture but the data of CT's is :CT, 100-200/5-5A 16kA 30VA cl 0.5 7.5VA 5P15 and for PTs :VT, 15-20kV/V3:100V/V3;cl0.5 30-50VA.
About frequency response, i dont have information

 

[Tony Tonon]

I'm new to this forum so hope this goes thru.
You may want to connect a load on the LV side and then take your measurements. Try to avoid a n0n-linear load.
Open circuit (unloaded) readings of THD may be meaningless in your application.