Fast valving of 1,000 MW turbine at Temelin nuclear power plant

''Close'' three-pole short circuits at the 400 kV switching station at Kocin are analyzed taking into account experience from abroad. In order to avoid the danger of loss of stability and asynchronous running at the 1000 MW reactor unit of the Temelin NPP, the fast valving (FV) system must be engaged. The effect of FV can be best assessed from the behavior of the load angle of the 1000 MW alternator. For operation involving 4 or 5 lines (Xe = 0.15 u.) and one permitted slip, the maximum time of a three-pole short circuit at the switching station and at the beginning of the lines (up to 20% length of the line from the Kocin switching station) is calculated to be 220 ms. This is consistent with the requirement of a minimum short circuit period of 180 ms in case of failure of the 400 kV switch at the switching station. The following is recommended for use to initiate the FV automatic system: signals from the distance protection of the 300 kV line at the Kocin switching station, REZ 1 and RELZ 100 type protection, bus-bar protection of the RADSS type at the Kocin 400 kV switching station, two alternator distance protections of the D15X1 type in the GTX1 system, and two undervoltage protections adjustable starting from 0.2 Un with an action period up to 50 ms. There exist 3 different ways of control of the actuating units. It is supposed that their combination would be applied, perhaps during a mere pulse unloading - control through a pair of EHO14 electrohydraulic transducers. Installation of an ELIN manufactured MSTAB microprocessor protection against loss of stability with a load angle sampling frequency of 25 or 12.5 Hz with periodical data saving for a time of approximately 15 s is recommended for monitoring the performance of the FV system in the information system of the 1000 MW unit. (author). 8 figs