ABB ret650 - Section 6 Differential Protection; Transformer Differential Protection T2 WPDIF and T3 WPDIF; Identification; Application

Section 6 Differential protection
6.1 Transformer differential protection T2WPDIF and
T3WPDIF
IP14639-1 v3
6.1.1 Identification
M15074-1 v5
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Transformer differential protection, two-
winding
T2WPDIF
3Id/I
SYMBOL-BB V1 EN-US
87T
Transformer differential protection,
three-winding
T3WPDIF
3Id/I
SYMBOL-BB V1 EN-US
87T
6.1.2 Application
M16722-3 v9
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 earth 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 current until it develops into an earth or phase fault. For
this reason it is important that the differential protection has a high level of
sensitivity and that it is possible to use a sensitive setting without causing
unwanted operations during external faults.
1MRK 504 169-UEN A Section 6
Differential protection
Transformer protection RET650 2.2 IEC 75
Application manual