The relay type NA90 can be typically used in radial or meshed MV and LV networks as feeder or power transformer protection:
• On radial, ring and parallel feeders of any length in solidly grounded, ungrounded, Petersen coil and/or resistance grounded systems.
• On parallel connected generators and transformer on the same busbar.
• For ground fault protection on both sides of power MV-LV transformers.
Moreover undervoltage and overvoltage functions are provided.

Applications
• Feeder
• Generator
• Motor
• Transformer
Protection functions
• Pt100 thermometric probes (26)
• Undervoltage (27)
• Thermal image (49)
• Phase overcurrent (50/51)
• Measured residual overcurrent (50N(1)/51N(1))
• Measured residual overcurrent (50N(2)/51N(2))
• Calculated residual overcurrent (50N(Calc)/51N(Calc))
• Overvoltage (59)
• Residual overvoltage (59N)
• Phase directional overcurrent (67)
• Ground directional overcurrent (67N)
• High impedance restricted earth fault (87NHIZ)
• Breaker failure (BF)
Monitoring and control functions
• CB diagnostic
• Cold Load Pickup (CLP)
• CTs monitoring (74CT)
• Digital Fault recording (DFR)
• Fault and event logging (SER & SFR)
• Logic selectivity
• Multiple setting profiles
• Programmable Logic Controller
• Second harmonic restraint
• Self-test
• Trip circuit supervision (74TCS)
• VTs monitoring (74VT)
Hardware
• 2 binary inputs + 6 output relays + 8 LEDs
• Auxiliary power supply 110-230 Vac/dc
• Auxiliary power supply 24-48 Vac/dc
• Flush, projecting, projecting, rack, with separate MMI
• Network module with Ethernet FX port (optical fiber)
• Network module with Ethernet TX port (copper RJ45) + RS485 port
• Nominal current 1/5 A selectable by DIP-switch
• RS485 port (unavailable with Ethernet FX port)
• Standard CT amperometric inputs 1/5 A
Communication
• Modbus RTU RS232 protocol
• Modbus RTU RS485 / IEC 870-5-103 / DNP3 protocol
• Modbus TCP/IP protocol (network board must be provided)