Toshiba GR200 Series Instruction Manual page 826

Split-synchronism-check element (SyncRy1-θ=0, SyncRy1-θless)
(ii)
With regard to the connection of asynchronous networks, it is necessary to use the technique
of split synchronism to avoid the occurrence of cycle-slip on the system. The technique consists
of three parts: (1) calculation of the synchronization point (SyncRy1-θ=0), (2) check for slip
cycle (SyncRy1-θless), and (3) advance time for issuing the closure command.
Calculation of synchronization point
Issuing a closure command for the CB is appropriate when the variance of Vr and Vi is
small. Hence, the timing of when it should be issued is calculated in the SyncRy1-θ=0 element
so that the prediction of coincident timing between the running, (Vr) and the incoming, (Vi)
voltages can be introduced. Figure 4.6-6(c) shows the coincident point (zero point).
Check for slip cycle
Checking the decrease in Δθ is a suitable means for controlling the issue of a closure command
to a CB at the requisite timing. The SyncRy1-θless element calculates the for reducing Δθ; it
assists in the computation of the SyncRy1-θ=0 element.
Advance time
The user shall consider the actual device operation time. For an asynchronous network, the
issue of the CB closure command should be initiated such that it is coordinated with the actual
closing. Figure 4.6-6 shows the advancing time; it is introduced with setting [SyncRy1-TCB],
closing time (Tcb) and compensation time:
where,
α: Operation time of the element
β: Compensation (i.e., tolerance) time
Tcb: Closing time of CB
Setting[SyncRy1-TCB] = α + T
- 803 -
6F2S1914 (0.49)
(4.6-14)
+ ��
CB
GRL200 (Soft 033 & 037)