20
1MRS755225
Transformer Terminal
Technical Reference Manual, General
RET 54_
4. Instructions
4.1.
Application
RET 541/543/545 transformer terminals are designed to be used for the protection,
control, measurement and supervision of two-winding power transformers and
generator-transformer blocks in distribution networks. RET 54_ terminals can also
be used in harsh environments e.g. in heavy industry, marine and off-shore
applications.
The main protection function is three-phase current differential protection with
stabilized and instantaneous stages for fast and selective winding short-circuit and
interturn protection. Besides 2nd and 5th harmonic restraints, the stabilized stage
also includes a waveform recognition-based blocking-deblocking feature. Reliable
operation even with partially saturated current transformers, that is, short operate
times at faults occurring in the zone to be protected and high stability at external
faults are achieved. Increased sensitivity can be obtained by automatic adaptation to
the position changes of the on load tap changer. Interposing current transformers are
not needed: Any vector group matching and CT ratio corrections in a wide range are
numerically implemented as well as zero-sequence current elimination, which
prevents unwanted trips at earth faults occurring outside the protected area.
In addition to the differential protection, the Basic version terminals incorporate the
following protections: Restricted earth fault protection with stabilized numerical or
high impedance principle, unbalance and thermal overload protections, three phase
overcurrent and directional or non-directional earth fault back-up protection with
definite and IDMT characteristics on both sides of the transformer.
The Multi-version terminals, including further overvoltage and undervoltage,
residual overvoltage, underfrequency and overfrequency, overexcitation, directional
overcurrent and underimpedance line back-up protections, fulfil the most
demanding application requirements.
With the optional automatic voltage regulation function, RET 54_ transformer
terminal can be applied as a comprehensive integrated transformer management
terminal. The voltage regulator can be applied for a single transformer or for parallel
transformers with Master-Follower, Negative Reactance or Minimizing Circulating
Current principles.
A special Control version terminal with just voltage regulator and control functions
can be applied, when integration of voltage regulation and protection is not allowed.
For an example of an application with basic functions, see Figure 4.1.-1.
Содержание RET 54 Series
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