Seconday Current during Power Transformer Energization
Seconday Current during Power Transformer Energization
(OP)
Hi,
We recently energized a 166MVA power transformer (230kV / 34.5kV --Grounded Wye / Grounded Wye thru resistance). We recorded currents on the primary and secondary side. The primary currents were as spected (~2000Amps) but I was surprised to see current on the secondary side, these currents aren't big in magnitude ~2-3Amps. Do these currents come from the capacitance of the secondary bus? The seconday CB was open so there was only about 15mts of insulated cable.
Cheers.
We recently energized a 166MVA power transformer (230kV / 34.5kV --Grounded Wye / Grounded Wye thru resistance). We recorded currents on the primary and secondary side. The primary currents were as spected (~2000Amps) but I was surprised to see current on the secondary side, these currents aren't big in magnitude ~2-3Amps. Do these currents come from the capacitance of the secondary bus? The seconday CB was open so there was only about 15mts of insulated cable.
Cheers.






RE: Seconday Current during Power Transformer Energization
RE: Seconday Current during Power Transformer Energization
With the exception of exciting current (which is very small, usually less than 3% of rated current), you shouldn't see any current on the primary if there's no current on the secondary.
Excluding exciting current, the following equation should hold true:
Vprimary*Ipimary = Vsecondary*Isecondary
RE: Seconday Current during Power Transformer Energization
RE: Seconday Current during Power Transformer Energization
RE: Seconday Current during Power Transformer Energization
RE: Seconday Current during Power Transformer Energization
Is this a constant 2-3 amps in question ? Or was it just momentary as per inrush current (12 cycles duration there about) ?
RE: Seconday Current during Power Transformer Energization
RE: Seconday Current during Power Transformer Energization
RE: Seconday Current during Power Transformer Energization
The 2000A primary sounds right for short time inrush. If you have oscillography, the waveform is interesting to look at.
2 - 3 amps secondary sounds off to me... Check to make sure the primary and secondary measurment leads you are using aren't close together or coiled around one another... possible its just induction you are reading. Was the measurment taking in a live switchyard?