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NA11 - Manual - 02 - 2009
GENERAL
2 GENERAL
Preface
The relay type NA11 can be used in radial networks as feeder or power transformer protection.
In solidly grounded systems the residual overcurrent protection can be used on feeders of any length,
while in ungrounded or Petersen coil and/or resistance grounded systems, the residual overcurrent
protection can be used on feeders of small length in order to avoid unwanted trippings due to the
capacitive current contribution of the feeder on external ground fault.
Beside to the phase and residual overcurrent protections, the automatic reclosing function is pro-
vided.
Following input circuits are available:
Three phase current and one residual current inputs with nominal currents independently select-
able at 1 A or 5 A using DIP-switch.
Two binary inputs.
One block input (logic selectivity).
In addition to the main protection element, the breaker failure (BF), CT monitoring (74CT), Trip Circuit
Supervision (TCS), Programmable Logic Controller (PLC) and automatic reclosing function (79) are
also provided.
Setting, programming and reading operations must be effected by means of Personal Computer with
ThySetter software or by means of remote communication interface (RS485 bus and Ethernet net-
work); all operations must be performed through MMI.
According to the hardware confi gurations, the NA11 protection relay can be shipped in various case
styles depending on the required mounting options:
Flush.
Projecting mounting.
Rack.
With separate operator panel.
Other options are:
Auxiliary power supply operating range.
Communication protocols.
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