Feeder Terminal REF 541, REF 543, REF 545.
1MRS750443-MBG
4
Application The REF 541, REF 543 and REF 545 feeder
terminals are designed to be used for protec
-
tion, control, measurement and supervision of
medium voltage networks.
They can be used with different kinds of
switchgear including single busbar, double
busbar and duplex systems. The protection
functions also support different types of net
-
works such as isolated neutral networks, reso-
nant-earthed networks and partially earthed
networks..
Fig. 2 Distributed protection and control system
based on REF 54_ feeder terminals.
Application area also covers protection func-
tions for a large variety of applications, e.g.
frequency and voltage based protection,
motor protection, thermal overload protec
-
tion, capacitor bank protection and synchro-
check/voltage check function.
In addition to protection, measurement, con-
trol and condition monitoring functions, the
feeder terminals are provided with a large
amount of PLC functions allowing several
automation and sequence logic functions
needed for substation automation to be inte
-
grated into one unit.
The data communication properties include
the following communications: SPA bus,
LON bus, IEC 60870-5-103, IEC 61850, Pro
-
fibus-DPV1, DNP 3.0 or Modbus communi-
cation with higher-level equipment. Further,
LON communication, together with PLC
functions, minimizes the need for hardwiring
between the units.
Design The feeder terminals REF 541, REF 543 and
REF 545 differ from each other regarding the
number of digital inputs and outputs avail
-
able. Please, refer to section “Ordering” for
more details.
The REF 54_ feeder terminals incorporate a
wide range of feeder terminal functions:
• Protection functions
• Measurement functions
• Disturbance recorder
• Power quality functions
• Control functions
• Fault locator
• Condition monitoring functions
• General functions
• Communication functions
• Standard functions
The function blocks are documented on the
CD-ROM “Technical Descriptions of Func-
tions” (1MRS 750889-MCD).
Protection functions
Protection is one of the most important func-
tions of the REF 54_ feeder terminal. The
protection function blocks (e.g. NOC3Low)
are independent of each other and have e.g.
their own setting groups and data recording.
The non-directional overcurrent protection
includes e.g. the three stages NOC3Low,
NOC3High and NOC3Inst, each with inde
-
pendent protection functions.
Either Rogowski coils or conventional cur-
rent transformers can be used for protection
functions based on current measurement.
Correspondingly, voltage dividers or voltage
transformers are used for protection functions
based on voltage measurement
For further information about functionality
levels and the protection functions included
in them, refer to the table “Functionality lev
-
els, protection functions” in section
“Ordering”.
Measurement functions
The measurement functions include three-
phase currents, neutral current, three-phase
voltages, residual voltage, frequency, active
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