Protection Functions - ABB RET630 Product Manual

Transformer Protection and Control
RET630
Product version: 1.0
Table 2. Supported functions, continued
Functionality
Residual voltage measurement
Sequence-current measurement
Sequence-voltage measurement
Power monitoring with P, Q, S, power factor, frequency
Metering
Pulse counter for energy metering
Disturbance recorder function
Analog channels 1-10 (samples)
Analog channel 11-20 (samples)
Analog channel 21-30 (samples)
Analog channel 31-40 (calc val)
Binary channels 1-16
Binary channels 17-32
Binary channels 33-48
Binary channels 49-64
1) Optional functions, to be specified at ordering

4. Protection functions

RET630 features transformer differential
protection with instantaneous and stabilized
stages to provide fast and selective protection
for phase-to-phase, winding interturn and
bushing short-circuits including most phase-to-
earth faults. Besides second harmonic
restraint an advanced waveform-based
blocking algorithm ensures stability at
transformer energization and fifth harmonic
restraint ensures stability at moderate
overexcitation.
Sensitive restricted earth-fault protection
(REF) completes the overall differential
protection to detect even single phase-to-
earth faults close to the earthing point of the
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transformer. Either the conventional high-
impedance scheme or a numerical low-
impedance scheme can be selected for
protection of the windings. If the low-
impedance REF protection is used neither
stabilizing resistors nor varistors are needed
and as a further benefit the transforming ratio
of the earthing point current transformers can
differ from those of the phase current
transformers. Due to its unit protection
character the REF protection does not need
any time grading, and therefore a fast
protection operating time can be achieved.
The IED also incorporates thermal overload
protection to prevent an accelerated aging of
the transformer isolation. Multiple stages of
short-circuit, phase-overcurrent, negative-
phase-sequence and earth-fault back-up
protection are separately available for both
1MRS756788 A
Issued: 15.09.2009
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