Protection Functions - ABB Relion 630 Series RET630 Product Manual

ABB
Transformer Protection and Control
RET630
Product version: 1.1
Table 2. Functions used in preconfigurations. Column 'n' shows the total number of
available function instances regardless of the preconfiguration selected., continued
Functionality
Binary receive
Double point receive
Interlock receive
Integer receive
Measured value receive
Single point receive
1) Optional function, 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
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 overexcitation protection is used to
protect generators and power transformers
against an excessive flux density and
saturation of the magnetic core.
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
windings. The three-phase underimpedance
protection, based on impedance values from
voltage and current phasors, provides backup
protection against short-circuit faults. Earth-
fault protection based on the measured or
calculated residual overvoltage is also
available.
To detect reversed power flow or circulating
currents at parallel power transformers
RET630 also offers directional overcurrent
protection. Further, overfrequency and
underfrequency protection, overvoltage and
undervoltage protection and circuit-breaker
failure protection are provided.
1MRS756978 D
Issued: 2011-05-18
A B n
- - 10
- - 32
- - 59
- - 32
- - 62
- - 62
9