1 2 3 4 A - SIPROTEC

Functions
2.9 Thermal Overload Protection
Cooling Method and Insulation Data
236
Set in address 4231 METH.COOLING which cooling method is used: ON = Oil Natural for natural cooling, OF =
Oil Forced for oil forced cooling or OD= Oil Directed for oil directed cooling. The definitions under margin
heading „Cooling Methods“ in the function description of the hot-spot calculation.
For hot-spot calculation, the device requires winding exponent Y and the hot-spot to top-oil gradient H gr, that
can be set under 4232 Y-WIND.EXPONENT and 4233 HOT-SPOT GR. If the corresponding information is not
available, it can be taken from the IEC 60354. An extract from the corresponding table of the standard with the
technical data relevant for this project can be found hereinafter.
Table 2-9 Thermal characteristics of power transformers
Cooling method:
Additional Thermal Overload Protection Function
Distribution
transformers
Medium and large power
transformers
ONAN ON.. OF.. OD..
Winding exponent Y 1.6 1.8 1.8 2.0
Insulation temperature gradient H gr 23 26 22 29
In the aforementioned description, the first thermal overload protection is described respectively. The
differences in the parameter addresses and message numbers of the first and second thermal overload
protection are illustrated in the following table. The positions marked by x are identical.
Parameter addresses Message no.
1. thermal overload protection function 42xx 044.xxxx(.01)
2. thermal overload protection function 44xx 204.xxxx(.01)
SIPROTEC, 7UT6x, Manual
C53000-G1176-C230-2, Release date 06.2012