ABB REC670 Applications Manual page 525

1MRK 511 401-UEN A
Bay control REC670 2.2 IEC
Application manual
IEEE C57.96-1995 has suggested maximum temperature limits for the four types
of loading, see table 52.
Table 52: Suggested maximum temperature limits
Type of Normal life
temperature expectancy loading
Insulated winding 120
hot spot
temperature in °C
Top oil 105
temperature in °C
IEEE standard has also suggested the limits of temperature and load for loads
higher than transformer nameplate.
• For distribution transformers with 65°C hot spot temperature rise:
• 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.
Planned loading Long term loading
beyond nameplate
rating
130 140
110 110
Section 17
Monitoring
Short term loading
180
110
519