Utility Unbalance loads
Utility Unbalance loads
(OP)
What is the maximum allowable utility unbalance loads at distribution level(25KV)? There are single phase loads and three phase loads.
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RE: Utility Unbalance loads
RE: Utility Unbalance loads
Traditionally, many utilities set an arbitrary goal of reducing unbalance to less than 10% as measured at the substation. Sometimes regulators will have specific requirements.
As noted by PHovnanian, a practical constraint is economic (higher losses for heavily loaded unbalances).
From a customer perspective, current unbalance is not important, but voltage unbalance for 3-phase customers is very important (don't want more than about 2% voltage unbalance).
So, who is asking about the 'maximum'?
- your regulator?
- your shareholders?
- your customers?
RE: Utility Unbalance loads
RE: Utility Unbalance loads
When you float the wye point, you my be subject to switching transients. I would not choose a wye primary/delta secondary transformer arrangement for power applications.
Wye primary/delta secondary may be used for protection and ground detection, and even for system grounding but these applications often use a broken delta secondary and the open corner on the delta avoids the circulating currents.
Note to our IEC friends; Nema- broken delta = IEC open delta.
NEMA open delta = IEC "V" connection.
Bill
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"Why not the best?"
Jimmy Carter
RE: Utility Unbalance loads
RE: Utility Unbalance loads
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Utility Unbalance loads
That 10% figure is a rule of thumb for load balance, not voltage. For a 10% load imbalance on a system with 5% Z, the voltage unbalance will only be 0.5% (an overly simplified example).