SEL-321 Phase and Ground Distance Relay
The SEL-321 Relay delivers outstanding EHV protection, performance, and features—at a price practical for all voltage levels and with the features you need for system integration.
- Comprehensive and Secure Distance Protection
Four zones of phase and ground mho elements plus four zones ground distance quadrilateral elements,each reversible,with independent phase and ground timers for complete distance protection. Positive-sequence memory voltage polarization with long memory time constant for three-phase fault directional security. Negative-sequence impedance directional element polarization for sensitive and secure operation during unbalanced faults. - Extensive Supplemental Protection Elements and Logic
Four residual and negative-sequence overcurrent elements with negative-sequence directional control. Phase,sequence,and ground time-overcurrent elements for backup protection. Out-of-step elements for power swing blocking and tripping. Phase and sequence under-and overvoltage elements. Load encroachment logic to protect against false operations during heavy load conditions. Single-pole tripping logic. Built-in communications-assisted tripping scheme logic. SELogic® control equations for custom scheme logic. - Multiple Settings Groups
Six settings groups,for maximum protection scheme flexibility, allow application with bus-tie breakers or for remote system reconfiguration. - Fault Locating
Use the built-in fault locator to efficiently dispatch line inspection and repair personnel. - Communications
Patented Mirrored Bits® Communications and communications-assisted tripping schemes.
- Apply the SEL-321 Relay for primary and/or backup single-or three-pole trip transmission line protection,including series-compensated lines.
- Use the advanced single-pole tripping logic with phase selection, open-pole interval protection,and phase discordance logic with three-pole trip to protect against excessive single-pole-open events.
- Choose from among the many communications-assisted tripping schemes available (POTT, DCUB, DCB, PUTT, DUTT, and DTT) including unique Mirrored Bits communications.
- Select the load-encroachment feature to prevent operation of three-phase elements under high load conditions.
- Use the time-overcurrent elements to provide current-dependent, time-delayed fault detection along the protected line and backup protection for remote terminals.
- Use weak-infeed logic to rapidly clear both line terminals for internal faults near the weak terminal.
- Select the SEL-321-5 Relay for enhanced performance on 50 Hz systems, including single-pole tripping.
- Use SEL-5040 Power System Report Manager Software to automatically gather relay event reports on your PC and manage them with a database.
- Use SEL-5010 Relay Assistant Software to manage your relay settings.
- Use SEL-5601 Analytic Assistant Software to display oscillograms and vector diagrams to analyze event reports.
- Chassis available for one additional interface I/O board.
- I/O boards with contact sensing inputs and standard control outputs, high-current interrupting outputs,or high-speed,high-current interrupting outputs. Connectorized® (plug-in connectors).Vertical or horizontal,panel-mount or rack-mount hardware packages (panel-mount available in Connectorized version only).
- Extra long time event reports, including oscillography, available in the SEL-321-2 Relay.
SEL provides options to help you efficiently and safely commission and test these relays.
When access to the back of panels and cabinets is allowed, use a Connectorized® version of this relay for fast installation and testing.
Flyers
Data Sheets
Instruction Manuals
Settings Sheets
Application Guides
Improvements to the Loss-of-Potential (LOP) Function in the SEL-321 - Use SEL-321 and SEL-311 Relays Where Two Different Systems Are Required for Primary and Backup Protection
- Applying the SEL-321 Relay on Series-Compensated Systems
- Use SEL-421, SEL-321, and SEL-311 Relays Where Different Systems Are Required for Primary and Backup Line Protection
- LOG Input Considerations When Implementing a DCUB Scheme Using Mirrored Bits™ Communications in the SEL-321, SEL-311C, SEL-311L, and SEL-421 Relays
- Recommended Ways to Detect Loss-of-Potential (LOP) Conditions in the SEL-321, SEL-421, and SEL-311 Series Relays
- Using the SEL-2126 Fiber-Optic Transfer Switch and the SEL-321-1 in Bypass-Breaker Mirrored Bits Communications-Assisted Tripping Schemes
- SecuControl Test Block and Plug Standards for SEL Relays
- REJO Application Guidelines
- Applying the SEL-321 Relay to Directional Comparison Blocking (DCB) Schemes
- Testing Frequency Shift Carrier From a Single End Using the SEL-321 Relay
- The SEL-321 Relay Load-Encroachment Function Setting Guidelines
- SEL-321 Zone 1 Extension Logic Description
- Multiple Reclosing Functions in the SEL-321 Relay Using SELogic® Control Equations
- SEL-221B/121B, SEL-221C/121C, SEL-221G/121G, SEL-221H/121H, SEL-221S/121S, SEL-121-10, SEL-2PG10/PG10, SEL-321-1 Fast Meter Command Processing
- SEL-221G-3/SEL-321 Relay Setting Equivalency Sheet
- SEL-221G-5/SEL-321 Relay Setting Equivalency Sheet
- SEL-221H/SEL-321 Relay Setting Equivalency Sheet
- SEL-221F/SEL-321 Relay Setting Equivalency Sheet
- SEL-321-1 Compressed ASCII Commands
- Fast Operate Command Processing
- Select the Best Reclosing Method for Your Application
- SEL-321-1/SEL-321-2 Configuration and Fast Meter Messages
- SEL-321 Relay Breaker Failure Protection
- Applying the SEL-321 Relay to Permissive Overreaching Transfer Trip (POTT) Schemes
- Using SEL Relays to Provide Primary or Backup Bus Protection
- Implementation of a New Communication-Aided Tripping Scheme Using the SEL-321 Relay Mirrored Bit Function
- Applying SEL Distance Relays on Lines with Power Transformers or Open Delta VTs
- Three-Terminal Line Protection Using SEL-321-1 Relays With Mirrored Bits™ Communications
- A Breaker Simulator in the SEL-321 Relay for Three-Pole Tripping Applications
- Applying the SEL-321 Relay to Directional Comparison Unblocking (DCUB)Schemes
- SEL-321-2 Relay Compressed ASCII Commands
- Using the SEL-321 Relay and SEL-221G Relay as Primary and Backup Transmission Protection
- Three Terminal POTT Protection Using the SEL-321 Relay
- Single-Pole/Three-Pole Autoreclose Function for Single Breaker Applications in the SEL-321 Relay Using SELogic® Control Equations
- Using SELogic® Control Equations to Provide Separate Trip Coil Monitor (TCM) Alarm Outputs in the SEL-321 Relay When Applied to Two-Breaker Line Terminals
- Using the SEL-321 Relay and SEL-221F Relay for Primary and Backup Transmission Protection
- Setting the Zero-Sequence Compensation Factors in SEL-321 Relays to Avoid Overreach in Mutual Coupled Lines
- Testing the SEL-321-1 Relay-to-Relay Digital Logic Communication Time Delay
Case Studies
Access drawings via the Online Product Configuration link in the Ordering Information box at the top right of this page (below the product photo).
From the Product Configuration page, configure your product or enter your part number via the Universal Part Number Reverse Lookup. Then download custom .dwg or .pdf files specific to your product.
You may also go directly to the Product Configuration page to make a product selection.