Narui Jibao's first 1GW hydro unit with dead-zone-free generator protection commissioned
On May 4th, Nanrui Jibao, an executive director unit of the China Electricity Council, officially put into operation the first domestically developed digital generator protection without dead zones for a million kilowatt hydropower unit at the Baihetan Hydropower Station. This achievement solves the long-standing problem of dead zones in the main protection of million kilowatt hydropower units and is also the first application of fully digital generator protection in large-scale units.
As the only hydroelectric power station in the world equipped with a single unit capacity of one million kilowatts of water turbine generator units, the Baihetan Hydropower Station adopts a stacked winding design for its left bank generator units. Although it effectively suppresses rotor eccentric vibration, the sensitivity problem of stator winding small turn short circuit protection is prominent. The original "two vertical and one horizontal" main protection scheme has a certain internal fault dead zone, which threatens the safe operation of the unit.
Based on its profound technical accumulation in the field of generator and transformer protection, as well as its outstanding advantages in flexible optical current transformer technology, Nanrui Jibao has conducted in-depth research on the non dead zone main protection scheme for multi branch stacked hydro generator sets. It has proposed a new criterion for branch loop incomplete differential protection based on a hybrid of optical CT and electromagnetic CT, and for the first time achieved high-sensitivity protection for stator winding 1-turn short circuit faults, completely eliminating the dead zone of main protection for million kilowatt hydropower units.
The successful application of the first domestic digital generator protection without dead zone in the Baihetan million kilowatt hydropower unit has solved the problem of dead zone in the main protection of the hydro generator unit. On the other hand, it has laid a solid foundation for the digital transformation of relay protection in power plants by adopting technologies such as SV sampling and GOOSE communication.
