ABB REC670 Applications Manual page 518

Section 17
Monitoring
512
Based on the settings TrafoRating and TrafoType, transformer parameters are
selected for temperature calculations. Both IEEE and IEC standards defines the
transformer parameters based on three categories of transformer rating.
In the case of three phase transformers:
• If the transformer rating is less than 2.5 MVA, the function considers this as a
distribution transformer.
• If the transformer rating is less than 100 MVA, it is considered as a medium
power transformer.
• If the transformer rating is above 100 MVA, it is considered as a larger power
transformer.
In the case of single phase transformers:
• If the transformer rating is less than 0.833 MVA, the function considers this as
a distribution transformer.
• If the transformer rating is less than 33.3 MVA, it is considered as a medium
power transformer.
• If the transformer rating is above 33.3 MVA, it is considered as a larger power
transformer.
NoOfWindings: This setting is used to set the number of windings in the
transformer. The options are :
• Three winding: The function considers the given transformer as three winding
transformer.
• Two winding: The function considers the given transformer as two winding
transformer.
Based on the setting NoOfWindings, hot spot temperature of the winding 3 is either
calculated or assigned as zero.
ConstSelection: This setting is used to select the transformer parameters taken
either from IEC 60076-7 standard or IEEE C57.96-1995 standard. The options are:
• IEC: Transformer parameters like constants, winding and oil exponents will be
taken from IEC 60076-7 standard for temperature calculations.
• IEEE: Transformer parameters like constants, winding and oil exponents will
be taken from IEEE C57.96-1995 standard for temperature calculations.
CurrSelectMode: This setting is used to select the current determining method
which is used for the load factor calculation. The function takes phase currents of
each winding as input. From each winding, only one phase current is considered
for load factor calculation. The options are:
1MRK 511 401-UEN A
Bay control REC670 2.2 IEC
Application manual