The Japanese 60 Hz systems are linked to each electric power company by 500 kV transmission lines. The long trunk line from the east to the west is over 1,000 km. Therefore, the systems present a typical longitudinal structure that stretches from east to west (tandem type system).
The "WEST 10-machine system" model described in this section is a 10-machine tandem model that is a prototype of the Japanese 60 Hz systems. It presents the long time oscillation characteristics of a tandem system. In developing this system, attention was given to the following points:
(1) The frequency of the long period oscillations is almost similar to that of the real system.
(2) The system capacity is also virtually the same as that of the real system.
(3) The length of the tie-line is almost the same as that of the real system.
(4) The system was developed to have as much as possible a simple tandem structure.
(5) The VAR Compensator equipments are not directly considered. The difference of their operation states during the daytime and nighttime is controlled by the power factor of loads.
(6) For a single load flow condition, the power flow condition is divided into stable and unstable depending on the fault location.
Table 3.1 Outline of the IEEJ West 10-machine System Model
Table 3.2 Calculation Results by Y-method
Fig.3.1 IEEJ WEST 10-machine System Model (Node No., Branch No., Disturbance Point)
Fig.3.2 IEEJ WEST 10-machine System Model (Impedance Map)
Fig.3.3(a) IEEJ WEST 10-machine System Model (Load Flow Map : Daytime Condition)
Fig.3.3(b) IEEJ WEST 10-machine System Model (Load Flow Map : Nighttime Condition)
Fig. 3.3(a) shows the load flow diagram in daytime condition. Besides the data associated with the generators of this system model, the rated capacities and rated output powers are also shown in the load flow diagram. The other data listed below are common to all the generators.
Fig. 3.4-6 and Fig. 3.7 show the waveforms of the internal angle oscillations when a 3LG fault occurs (for 70 ms) on a single line. These Figures are obtained for a constant current load characteristic, that is, NLT = 2. It can be seen from these results that there are long period stable or unstable depending on the fault location. Thus our major objective has been achieved.
For the nighttime condition, it is assumed that the number of generators operating in the real system (daytime) is reduced, and the rated capacities, rated output powers of all the generators are set to be 60% of the daytime condition.