ABB REC670 Applications Manual page 564

Section 17
Monitoring
558
ExpectedLife: The transformer expected insulation life in hours can be set by this
setting. As per IEEE C57.91-1995 the normal life expectancy at a continuous hot spot
temperature of 110 ̊ C is 180,000 Hours.
AgeingRateMeth: This setting is used to select the method to be used for transformer
insulation relative ageing rate calculation between IEC standard method and IEEE
standard method. It has the following options:
• IEC: Transformer insulation age calculation based on IEC standard method.
• IEEE: Transformer insulation age calculation based on IEEE standard method.
ThermalUpgrade: This setting is used to select the transformer insulation paper type
between thermally upgraded insulation and normal insulation. It has the following
options:
• Upgraded: The function considers the given transformer has thermally upgraded
paper insulation.
• Normal: The function considers the given transformer has normal insulation.
TimeToUpdate: This setting is used to set the time interval for updating the transformer
insulation loss of life calculation outputs LOLINDAY and LOLINYRS. It can be
selected as 1 hour/ 2 hour/ 4 hour/ 8 hour/ 12 hour/ 24 hour depending on user
requirement.
Two settable warning levels are available for hot spot temperature with separate
outputs. If warning level exceeds for the set time, an alarm is generated.
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 temperature Normal life
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:
Planned loading Long term loading
beyond nameplate
rating
130 140
110 110
1MRK 511 401-UUS A
GUID-B170CF21-839E-4246-A607-55A8999FAD07 v1
Short term loading
180
110
Bay control REC670 2.2 ANSI
Application manual