6.2.1.2 Description of configuration B30
This configuration is used in applications with two winding transformers in multi-
breaker arrangement on one or both sides. The tripping is three poles and includes also
a synchronism check function for manual closing of the low voltage side breaker. The
high voltage breaker is foreseen to always energize the transformer and be interlocked
with an open LV side breaker. High voltage circuit breaker synchronism check
function is optional for system where synchronism check is required to close the bays/
rings.
The Differential protection is the main function. It provides fast and sensitive tripping
for internal faults. Stabilization against through faults, inrush and overexcitation are
standard features. The function is provided with six stabilized inputs which allows all
CT sets possible with multi-breaker arrangements on several of the windings to be
possible.
Restricted earth fault protection of low impedance types are provided for two windings
with an optional one for the last winding for cases where this winding is directly
ground. The low impedance type allows mix of the function on the same core as other
protection functions.
The tripping from transformer auxiliaries such as pressure relief devices/buchholtz,
temperature devices are linked through the binary inputs which are stabilized against
unnecessary operations due to capacitive discharges.
Back-up protection for faults inside the transformer but mainly for system faults are
provided by the phase and ground overcurrent functions provided on each winding.
A thermal overload function is available to supervise abnormal service.
Breaker failure protection is provided for each of the involved breakers.
Voltage protection functions are available as voltage level supervision.
The necessary auxiliary functions such as fuse failure supervision are also included.
The necessary trip logic is provided to trip the circuit breakers.
Measuring functions S, P, Q, I, V, PF, f are available for local presentation on the local
HMI and/or remote presentation. The availability of analog inputs allows connection to
separate metering cores and a built-in calibration on the analog inputs allows
calibration at site to very high accuracy, then involving the instrument transformer
errors and voltage drops in secondary cabling.
1MRK504116-UUS C Section 6
Configuration
857
Application manual
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