LIMITS OF TRANSFORMER TEMP. RISE

LIMITS OF TRANSFORMER TEMP. RISE
No.	Description	IEC60076-1, 2000 IEC60076-2, 1993 IEC60354, 1991		IEEE C57.91-1995 IEEE C57.12.00-2000		Conclusion	Remarks
1	Reference Temperature	-25℃ ∼ +40℃	clause 1.2.1 of IEC60076-1	-30℃∼ +40℃	clause 4.1.2.1 of IEEE C57.12.00 clause 6.4 of IEEE C57.91	Design temp is 40℃
2	Temperature Rise at Top-Oil	60K	clause 4.2 of IEC60076-2	65℃	clause 9.2.1 Table 8 of IEEE C57.91	Different
3	Temperature Rise at Winding	65K	For transformers identified as ON.. or OF.. clause 4.2 of IEC60076-2	65℃	clause 5.11.1.1 of IEEE C57.12.00	65℃ rise @40℃ (But 70℃ rise @OD.. cooling as per IEC)
		70K	For transformers identified as OD.. clause 4.2 of IEC60076-2
4	Winding Hot Spot Temperature	up to 110℃	clause 2.6.1 of IEC60354 Reference value is 98℃. But transformer with thermally upgraded insulation, the normal life expectancy is based on Hot Spot Temperature 110℃.	80℃ rise	clause 5.11.1.1 of IEEE C57.12.00 clause 9.2.1 Table 8 of IEEE C57.91	80℃ rise @40℃
5	Core, of electrical connections outside the windings or of structural parts in the tank	No numerical limit	clause 4.2 of IEC60076-2	Not excess of the winding hottest-spot temp. rise	clause 5.11.1.3 of IEEE C57.12.00	No limits