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Phase and Ground Distance Relay

The SEL-321-5 Relay is designed especially for EHV and HV applications on 50 Hz systems. The relay provides enhanced single-pole tripping, phase and ground distance, directional overcurrent, negative-sequence overcurrent, and fault locating. The SEL-321-5 Relay contains all the protective elements and control logic necessary to protect, monitor, and control overhead lines.

Starting At

$5,600 USD

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50 Hz EHV and HV applications.

Designed to meet stringent single-pole tripping requirements.

Contains all the protective elements and control logic necessary to protect, monitor, and control any noncompensated overhead line.

The unique adaptive directional element chooses between negative- and zero sequence quantities based on signals generated by a disturbance.

Power-swing blocking is provided during the single-pole-open period immediately following a single-pole trip.

Use acSELerator QuickSet SEL-5030 Software to manage your relay settings.

Use acSELerator Team SEL-5045 Software to automatically gather relay event reports on your PC and manage them with a database.

Use synchroWAVe Event Software to display oscillograms and vector diagrams to analyze event reports.



  • Four zones of phase and ground distance protection.
  • Quadrilateral (and/or mho) characteristic for ground distance protection.
  • Adaptable directional element selects best measurement technique (negative-sequence or zero-sequence impedance).
  • Independent timers for phase and ground distance time-delayed trips.
  • Any zone may be set forward or reverse.
  • Patented Mirrored Bits technology for communications-aided tripping schemes (eight independent channels in each relay).
  • Flexible communications and RTU features including three independent ports; ASCII, multidrop, and binary protocols; compressed ASCII commands; Fast Meter/Fast Operate support; Remote control bits for SCADA/RTU functions.

Minimum QuickSet Version

Product Certifications