Transformer Differential Protection T2Wpdif And T3Wpdif (87T) - ABB RELION RET670 Applications Manual

1MRK 504 163-UUS A
Section 7
7.1
7.1.1
7.1.2
Transformer protection RET670 2.2 ANSI
Application manual
Differential protection
Transformer differential protection T2WPDIF and
T3WPDIF (87T)
Identification
Function description
Transformer differential protection, two-
winding
Transformer differential protection,
three-winding
Application
The transformer differential protection is a unit protection. It serves as the main
protection of transformers in case of winding failure. The protective zone of a
differential protection includes the transformer itself, the bus-work or cables between
the current transformers and the power transformer. When bushing current
transformers are used for the differential IED, the protective zone does not include the
bus-work or cables between the circuit breaker and the power transformer.
In some substations there is a current differential protection relay for the busbar. Such a
busbar protection will include the bus-work or cables between the circuit breaker and
the power transformer. Internal electrical faults are very serious and will cause
immediate damage. Short circuits and ground faults in windings and terminals will
normally be detected by the differential protection. Interturn faults are flashovers
between conductors within the same physical winding. It is possible to detect interturn
faults if sufficient number of turns are short-circuited. Interturn faults are the most
difficult transformer winding fault to detect with electrical protections. A small
interturn fault including just a few turns will result in an undetectable amount of
Differential protection
IEC 61850 IEC 60617
identification identification
T2WPDIF
3Id/I
SYMBOL-BB V1 EN-US
T3WPDIF
3Id/I
SYMBOL-BB V1 EN-US
Section 7
IP14639-1 v3
M15074-1 v5
ANSI/IEEE C37.2
device number
87T
87T
M16722-3 v9
135