Transmission Line Protection - Doing it Right

Author: Simon Chano, HQT


The Hydro Québec Transmision Grid
Hydro-Québec TranÉnergie (HQT) operates the most extensive transmission system in North America. The system comprises 32,826 km of lines at different voltages ranging from 765 kV to 69 kV or less that deliver reliable power from 508 transmission substations and 18 interconnections to customers in Québec, other parts of Canada and the United States. Extreme long 735 kV transmission lines of more than 1,000 km from James Bay and the Manic-Outardes complex deliver a winter peak load of 36,251MW in 2007 mainly from 54 hydroelectric generating stations. Almost 96% of the installed system capacity is from hydroelectric generation serving customers throughout a territory of 850,000 sq. km. To offset the effects of distance between generating facilities and load centers, and maintain in the mean time a reliable and secure system, HQT has installed series compensation on many strategic 735 kV lines to enhance the system robustness. Today, HQT uses different modes of reactive power compensation to control the voltage and employs a multi-terminal direct current link from northern Québec to NEPOOL over a distance of 1200 km.

Hydro-Québec TransÉnergie within a regulatory context
For the bulk system, HQT must meet all regulatory requirements as per the North American Electric Reliability Council (NERC) and the Northeast Power Coordinating Council (NPCC). NERC sets operating and planning criteria to ensure reliable power system operation. On the other hand, NPCC of which Hydro Quebec is a member, establishes reliability criteria for all power systems in the Northeast. HQT coordinates its activities with the "Régie de l'énergie du Québec" (RÉQ) which has the role to establish or adjust transmission rates and conditions, authorize the acquisition, construction or disposal of transmission assets and study customer complaints regarding application of transmission tariff.

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