Connecting LV Mobile Generator to a HV Transformer
Connecting LV Mobile Generator to a HV Transformer
(OP)
Hi all. I have a 2MW, 480VAC mobile generator that we commonly use in conjunction with our 2500kVA Multi-Tap VanTran Transformer (see attached picture). The voltage rating for the transformer is 2400(delta) x 720(delta)-480(Y)/277; 4160(GRDY)/2400 x 12470(GRDY)/7200-480(Y)/277. We use this combination with utility companies as a stand alone system or to parallel to the utility to peak shave/baseload. My question is, when is it necessay to run in a 480(Y) configuration? Usually, the utility connects the concentrics of the HV cable from H1, H2, & H3 to the HO bushing (which is typically bonded to the grounding system). On the 480V side, we usually lift the bond from XO bushing to the system ground and leave the neutral-ground bond in the generator connected.
This question ALWAYS comes up when we use this combination and ANY advice would be GREATLY appreciated!
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This question ALWAYS comes up when we use this combination and ANY advice would be GREATLY appreciated!
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RE: Connecting LV Mobile Generator to a HV Transformer
With power flow from a delta to a wye in a wye-delta transformer has no such issues.
Bill
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"Why not the best?"
Jimmy Carter
RE: Connecting LV Mobile Generator to a HV Transformer
RE: Connecting LV Mobile Generator to a HV Transformer
Don't confuse grounds and neutrals.
With a wye:wye transformer connection, the voltages and currents are reflected from one side to the other.
If the supply side neutral is floating you have the three phase variation of the open neutral condition.
The most familiar open delta scenario is a residential installation in North America (120/240 Volt utilization with shared grounded neutrals for our IEC friends.)
If a shared neutral goes open the voltages are in inverse proportion to the load impedances on both the affected circuits.
On a three phase transformer bank, transformer saturation and phantom delta effects may act to moderate the voltage shifts.
Bill
--------------------
"Why not the best?"
Jimmy Carter