Toshiba GR 200 Series, Instruction Manual

Page: 232 / 1563

6F2S1915 (0.46)
GRZ200 (Soft 031 & 032)
- 211 -
Thermal overload function (THM)
Apparatus such as cables, transformers, generators and others can become overheated when
overloaded beyond their respective design limits due to excessive demands being placed on the
system. The thermal overload function (THM) works by determining the temperature rise in
an item of primary equipment by monitoring the current in order to detect the thermal
overload of the apparatus.
THM has an exponential characteristics in accordance with the IEC 60255-149 standard.
THM determines both the
I
2
R
loss and the cooling effect of the coolant simultaneously; THM
also determines the pre-load condition and signals a trip signal when an overload condition
arises.
THM issues a trip signal in accordance with an alarm stage that reflects the temperature
of the thermal overload condition. The alarm stage is configured using a setting; hence, the
user should determine the appropriate setting so that a trip signal can be issued before the
apparatus is overheated
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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
Appendix: Ordering
.
Table 2.8-1 Comparative table in respective ordering numbers
Sec. Feature
Ordering No. at “G&T”
31 32
– Main features
✓ ✓
✓
: Applicable NA: Not applicable