GENERAL
10
NA011 - Manual - 05 - 2022
2 G E N E R A L
2 G E N E R A L
Preface
The relay type NA011 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.
The NA011 protection relay may be shipped with traditional CTs or low power (LPCT) current inputs;
for both versions, the residual overcurrent protection can use the measured (CTs or balanced trans-
former) or the calculated residual current.
Following input circuits are available:
Phase current inputs
Traditional CTs
• Three phase current inputs with secondary nominal currents independently selectable at 1 A or 5 A
through DIP-switches.
Low power CTs
• Three phase current inputs with primary nominal currents independently selectable through
DIP-switches and software.
Residual current input
Measured residual current
• One residual current input with secondary nominal current selectable at 1 A or 5 A through DIP-
switches.
Calculated residual current
• Residual current is calculated by the vector sum of the three phase currents, measured by three
1 A or 5 A CTs or by three LPCT type sensors.
Setting, programming and reading operations must be effected by means of Personal Computer with
ThyVisor software or by means of remote communication interface (RS485 bus); all operations must
be performed through MMI.
The NA011 hardware case is suitable for flash and rack mounting
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