Toshiba GR200 Series Instruction Manual page 309

Out of step tripping protection by distance relay (OSTZ)
System faults, line switching and the loss of application of large blocks of loads will induce the
change of electrical characteristics at any time at which the output of the generator and the
input of the load remain constant relatively in the system. As a result, the system will be
required to adjust itself to continue operation and service. If the changes are large, the system
may face instability; and several portions lost their synchronism in the system. The system
should be carried out separation of the faulted portion upon the occurrence of synchronism
being lost. This occurrence is termed "Out-of-step"; and the out-of-step-tripping by distance
relays (OSTZ) is provided to make separation of the system.
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Note: The implementation of particular features is dependent upon the selection of
hardware and the configuration of functions. Several IED models do not support certain
features. To determine whether a particular feature has been implemented within an IED,
identify the IED ordering number; and check the order number for the "G&T position" whilst
referring to the comparison table below. For more information, see
Table 2.18-1 Comparative table in respective ordering numbers
✓: Applicable
Sec. Feature
– Main features
NA: Not applicable)
- 288 -
Ordering No. at "G&T"
31 32
✓ ✓
6F2S1915 (0.46)
(2.55.0)
Appendix: Ordering
.
GRZ200 (Soft 031 & 032)