By Rich Heidorn Jr.
In a victory for wind energy advocates, FERC last week rejected SPP’s proposed method for measuring generators’ reactive power, saying it said would result in excessive and unnecessary costs (ER17-107).
The commission rejected the RTO’s October compliance filing in response to Order 827, which revised the pro forma large and small generator interconnection agreements to add reactive power requirements for all newly interconnecting nonsynchronous generators.
Although the order required grid operators to ensure compliance by measuring reactive power at the “high-side” of the generator substation, SPP sought an “independent entity variation” allowing it to conduct measurements at the point of interconnection.
SPP said the variation was justified because its transmission system is dispersed over a wide geographic area and that many interconnection customers use longer generator lead lines to the point of interconnection to reach optimal parts of the transmission system.
The RTO said that measurements at the generator substation will not reflect “the charging or impedance” on the generator lead lines between that substation and the interconnection, creating a risk of excessive high and low voltages on the transmission system. SPP said that reliability standards would require the installation of reactive power compensation devices, at additional cost to transmission customers.
The proposal brought protests from several renewable generators and the American Wind Energy Association, which said the commission had considered the potential for long generator lead lines in their deliberations on Order 827. They also said SPP was not unique in having high-voltage nonsynchronous generator lead lines of 20 miles or longer.
The commission agreed, noting that Order 827 found that “requiring fully dynamic reactive power capability at the point of interconnection may result in significantly increased costs for nonsynchronous generators.”
Although setting reactive power requirements at the point of interconnection “would provide the greatest amount of reactive power to the transmission system,” the commission said, “the costs associated with providing that level of reactive power do not justify the added benefit to the transmission system.”
“In Order No. 827, the commission carefully considered the appropriate point at which to measure reactive power and ultimately found that ‘measuring the reactive power requirements at the high-side of the generator substation reasonably balances the need for reactive power for the transmission system with the costs to nonsynchronous generators of providing reactive power.’”
FERC also said SPP was not unique in its geography and had failed to provide information to support its reliability concerns. “Like SPP, other ISOs/RTOs have nonsynchronous generation interconnecting with the generator terminals located a significant distance from their point of interconnection. Similarly, SPP faces the same growing penetration of nonsynchronous generators as other ISOs/RTOs that in part resulted in the commission issuing Order No. 827,” the commission said.
It ordered the RTO to submit an additional compliance filing within 30 days.