• Top oil temperature = 120°C
• Hot spot winding temperature = 200°C
•
Short-time loading (1/2 h or less) = 300%
• For power transformer with 65°C hot spot temperature rise:
• Top oil temperature = 110°C
• Hot spot winding temperature = 180°C
• Maximum loading = 200%
Settings related to warning and alarm are:
WrnHPTmpLev1: This setting is used to set the level 1 value for hot spot temperature
warning.
WrnHPTmpLev2: This setting is used to set the level 2 value for hot spot temperature
warning. This should be more than the WrnHPTmpLev1 setting.
tDelayToAlarm1: This setting is used to set the time delay for the level 1 hot spot
temperature alarm. This time setting can be less than the winding time constant. For
example if the winding time constant is 420 sec, this setting can be 400 sec.
tDelayToAlarm2: This setting is used to set the time delay for the level 2 hot spot
temperature alarm. This should be less than time setting in tDelayToAlarm1.
18.11.3 Setting example
18.11.3.1 Transformer Rated Data
GUID-B3AE440F-CC5E-4742-9483-8D6448A476C8 v1
Table 73: Transformer Rated Data
Parameter Value Note
Frequency 50 Hz
Rated Power 500 MVA / 500 MVA / 20 MVA
Voltage ratio 415 kV / 230 kV / 20 kV
Tap changer ±9 1.67% of 230 kV
Winding 1 rated current 696 A
Winding 2 rated current 1255 A
Winding 3 rated current 577 A
Connection Type YNyn0d1
Cooling ONAF
p.u. Impedance 0.120
At Base 500 MVA
Table continues on next page
1MRK 504 163-UUS A Section 18
Monitoring
Transformer protection RET670 2.2 ANSI 913
Application manual
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