FERCon July 21 adopted a proposal requiring small generating facilitiesinterconnecting with the grid to be able to "ride through abnormalfrequency and voltage events."
Generatorswith capacity of 20 MW or less traditionally have been allowed to disconnectduring abnormal frequency and voltage events because their doing so had minimalimpact on a transmission provider's electric system. But FERC in Marchproposed to revisethe agency's pro forma small generator interconnection agreement to essentiallymandate that those resources executing agreements after the revisions go intoeffect have the same ride-through capability required of large generators.
Thenumber and impact of small generating facilities connecting to the grid haveincreased significantly since mandatory ride-through requirements were lastconsidered, FERC reasoned. Moreover, new technology, such as smart inverters,has become available that allows newly interconnecting small generators toremain connected during frequency and voltage disturbances. Holding small andlarge generators to different standards with respect to ride-through capabilitytherefore may have become unduly discriminatory or preferential, according toFERC.
Virtuallyevery party weighing in on the proposal agreed that the move would increase the reliability ofthe power system in light of the increasing number of small resources that areconnecting with the grid. However, some worried that FERC's plan forimplementing the changes may be too ambitious for some regions.
TheJuly 21 final rule, Order 828,largely adopted the proposed rule's provisions. In doing so, the agencyrepeated many of the same justifications outlined in the proposal, includingthat not subjecting small generators to the same ride-through requirements thatapply to larger generators would be unduly discriminatory.
Inaddition, the commission noted that new engineering standards allow smallgenerating facilities more leeway to ride through disturbances. It also saidthe absence of ride-through requirements for small generating facilitiesincreases the risk that an initial voltage or frequency disturbance may cause asignificant number of small generating facilities to trip across a particulararea or interconnection, further exacerbating the initial disturbance andcreating reliability issues.
FERCacknowledged that some areas have a greater penetration of distributedresources than others, but said the proposed reforms are neverthelessappropriate on an industry-wide basis now and that deferred action would not beappropriate. The agency also stressed that the rule allows ISOs and RTOs toseek "independent entity variations" from the new requirements.
Thecommission therefore said newly interconnecting small generating facilities maynot disconnect automatically or instantaneously from the system during abnormalfrequency or voltage conditions. In addition, the transmission provider mustcoordinate the small generating facility's protective equipment settings withany automatic load shedding program, and that the specific ride-throughsettings must be consistent with Good Utility Practice and any standardsapplied to other generating facilities on a comparable basis.
Thenew requirements will apply to new interconnection customers that execute orrequest the unexecuted filing of a small generator interconnection agreement onor after the effective date of the final rule. They will also apply to existinginterconnection customers that request a new or modified small generatorinterconnection agreement on or after that effective date.
Order828 will take effect 65 days after its publication in the Federal Register.(RM16-8)