Case Study: Imperial Irrigation District improves multiterminal generation protection with Schweitzer Engineering Laboratories (SEL)

Case Study of a Multiterminal Generation Interconnect Scheme

Imperial Irrigation District needed a way to safely integrate 90 MW of geothermal generation from Ormat Technologies across three nearby plants into its 92 kV transmission system, while supporting multiple operating configurations, weak-infeed conditions, and high reliability during switching between a dedicated line and a tapped line. The existing relays at the remote substations were mostly vintage devices with limited logic flexibility, and the project also required a scheme to prevent instability by shedding generation when load was lost at the Highline transformer.

Schweitzer Engineering Laboratories (SEL) worked with IID to implement a multiterminal protection and system integrity protection scheme using microprocessor relays, a logic processor, DTT, POTT with weak infeed, Zone 1 step distance, breaker failure logic, and SIPS functionality. SEL’s solution automated settings-group selection, coordinated communications between substations, and enabled reliable fault clearing without false trips; commissioning was completed successfully with no outages to operating geothermal units. The installed scheme has performed as intended, including a successful POTT clearing on the Highline line, and SEL also outlined a future upgrade path that would reduce SIPS operating time from about 15 cycles to about 10 cycles using synchrophasor-based protection.

Imperial Irrigation District

Joel Lopez

Imperial Irrigation District