Section 7 Differential protection
7.1 Transformer differential protection
T2WPDIF and
T3WPDIF (87T)
IP14639-1 v3
7.1.1 Identification
M15074-1 v5
Function description IEC 61850
identification
IEC 60617
identification
ANSI/IEEE C37.2
device number
Transformer differential protection, two-
winding
T2WPDIF
SYMBOL-BB V1 EN-US
87T
Transformer differential protection,
three-winding
T3WPDIF
SYMBOL-BB V1 EN-US
87T
7.1.2 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
dif
ferential 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
1MRK 502 071-UUS A Section 7
Differential protection
Generator protection REG670 2.2 ANSI and Injection equipment REX060, REX061, REX062 133
Application manual
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