ABB RELION RET670, Applications Manual

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Section 2 Application
2.1 General IED application
M16637-3 v14
The Intelligent Electronic Device (IED) provides fast and selective protection,
monitoring and control for two- and three-winding transformers, autotransformers,
step-up transformers and generator-transformer block units, phase shifting
transformers, special railway transformers and shunt reactors. The IED is designed to
operate correctly over a wide frequency range in order to accommodate power system
frequency variations during disturbances and generator start-up and shut-down.
The IED has a fast, low-impedance differential protection function with very low
requirements on the CTs. It is suitable for differential applications with multi-breaker
arrangements with up to six restraint CT inputs. The differential protection function is
provided with a 2nd harmonic and waveform-block restraint feature to avoid tripping
for CT saturation and transformer inrush current, and 5th harmonic restraint to avoid
tripping for transformer overexcitation.
The differential function offers a high sensitivity for low-level internal faults by using a
sensitive differential protection feature based on an amplitude measurement and
directional comparison of the negative sequence components.
Multiple low impedance restricted ground-fault protection functions are available as a
sensitive and fast main protection against winding ground faults. This function
includes a internal/external fault discriminator for additional security.
Additionally, a high impedance differential protection function is available. It can be
used for different applications including restricted ground fault protection as winding
protection, autotransformer differential protection, shunt reactor protection, T-feeder
protection, busbar protection and generator differential protection.
Tripping and alarm signals from pressure relief, Buchholz and temperature devices can
be sent directly to the IED via binary input channels for alarm and back-up purposes.
The binary inputs are highly stabilized against disturbances to prevent incorrect
operation due to, for example, DC system capacitive discharges or DC ground faults.
Distance protection functionality is available as back-up protection for faults within the
transformer and in the connected power system.
1MRK 504 163-UUS A
Section 2
Application
Transformer protection RET670 2.2 ANSI 43
Application manual