The “EAST 10-machine system” model is a simplified 10-machine model that is a prototype of the 50 Hz of the Japanese systems. It has the structural characteristics of the 500 kV loop and that of different voltage levels, the 500 kV, 275 kV loops.

In developing this system model, attention was given to the following points:

The frequency of the long period oscillations is almost similar to the average frequency of the real system, that is, about 2-4 sec.
The fault-to ground current of the 500 kV system should not exceed the allowable value (63 KVA).
The VAR compensator equipments are not directly taken into account, and the control of node voltage is done by the power factor of the loads.

Summary of the system model

Table 2.1 Outline of the IEEJ East 10-machine System Model
Table 2.2 Generator Data
Table 2.3 Calculation Results by Y-method
(Simulation results based on the Y-method in Fig.2.4 – Fig.2.6 and Fig.2.7.)
Fig.2.1 IEEJ EAST 10-machine System Model (Node No., Branch No., Disturbance Point)
Fig.2.2 IEEJ EAST 10-machine System Model (Impedance Map)
Fig.2.3 IEEJ EAST 10-machine System Model (Load Flow Map)

The daytime conditions are shown in Fig. 2.3(a). It can be seen that this is a very stringent system.

Long period oscillations of (about 2.5 sec.) occur following a 3 phase to ground fault (the fault at the point C) on a single line of the system loop made up of different voltage levels. It can be seen that our major objective has been achieved.

For the daytime power flow condition, all the generators operate at rated output power. However, the night power flow condition is 60% of the daytime condition. A part of the pumped storage plants is also considered as operating during the night.