Protection of units with adjustable-blade turbines from racing

Conclusions

To increase the operating safety of units with adjustable-blade turbines in transitional regimes, it is necessary to carry out the following measures and investigations:

• 1. At hydrostations equipped with quick-closing gates, it is necessary to disconnect the simultaneous action of protective systems with a triggering setting of 140–170% of the rated rotational speed on the start-stop member of the speed governor and on the emergency closing valve, leaving the action only on the quick-closing gates.

• 2. At hydrostations where there are no quick-closing gates and emergency closing valves are used for protecting the unit from racing, it is necessary to disconnect the simultaneous action of the protective systems with settings of 115% and 140–170% on the start-stop member of the governor, leaving the action only on the EVC. The time of closing the guide vanes from the ECV should be set in conformity with the recommendations of the turbine manufacturer.

• 3. The action on the stopping relay for the purpose of automatic performance of the operations of slowing and stopping the unit should be done only after complete closing of the guide vanes. For this purpose, the contact of the signaling device, which closes upon complete closing of the guide vanes, should be connected in the circuit of the output protective relay in series with the contact of the racing protection relay, or the signal should be sent to the normal stopping circuit after a decrease of the rotational speed to the rated.

• 4. It is necessary to conduct additional investigations to refine the safe time of closing the guide vanes of turbines and time of turning the blades during racing of the unit.