Siemens SIPROTEC 5 7SL86 Line Differential & Distance Protection Relay

The Siemens SIPROTEC 5 7SL86 is an advanced modular protection relay that combines line differential and distance protection in a single device. Designed for medium- and high-voltage transmission systems, it provides fast, selective, and reliable fault detection to ensure maximum grid stability and operational safety.

Built on the powerful SIPROTEC 5 platform, the 7SL86 supports multi-end line protection (up to 6 ends), making it ideal for complex power networks such as ring and mesh systems. Its adaptive differential protection algorithm ensures high sensitivity and stability even under challenging conditions like current transformer saturation and transformer errors.

With a minimum tripping time of ~9 ms, the relay ensures rapid fault clearance and minimizes system disturbances. The modular and expandable I/O architecture allows flexible configuration based on project requirements, making it suitable for modern digital substations.

Main Function

• Line Differential Protection
• Distance Protection (backup or main protection)

Tripping

• 3-pole tripping
• Minimum tripping time: ~9 ms

Technical Specifications

Protection & Functional Features

• Combined line differential + distance protection
• Suitable for:
  • Overhead lines
  • Underground cables
• Supports multi-end protection (up to 6 line ends)
• Adaptive differential protection ensures:
  • Stability during CT saturation
  • Immunity to transformer errors
  • Reliable operation under disturbances
• Distance protection provides:
  • Backup protection
  • Flexible protection schemes
• Detects:
  • Phase faults
  • Ground faults

Hardware & Modular Design

• Fully modular and expandable I/O configuration
• 12 predefined standard variants available
• Typical configurations:
  • CT/VT: 4/4 or 8/8
  • Binary inputs: 5 to 31
  • Binary outputs: 8 to 46
• Flexible I/O scaling within SIPROTEC 5 platform
• Conformal coating for harsh environmental conditions
• Scalable for future system expansion

Communication & Protocols

• IEC 61850 Edition 2 compliant
• GOOSE messaging for high-speed communication
• Supports:
  • PRP / HSR redundancy
  • Modbus TCP
  • Up to 4 communication modules
• Enables full digital substation integration

Engineering & Software

• Configurable via DIGSI 5 engineering tool
• Graphical logic configuration (CFC)
• Integrated protection, control, automation, and monitoring
• Simplified commissioning, testing, and diagnostics

Advanced / Latest Features

• Web-based user interface for monitoring and diagnostics
• Advanced cybersecurity:
  • Role-based access control
  • Secure firmware and communication
• Digital Twin support for simulation and testing
• Process bus ready (Sampled Values support)
• High availability with redundant communication architecture

Applications

• Transmission line protection (HV/EHV/MV)
• Multi-terminal line protection (up to 6 ends)
• Ring and mesh network protection
• Utility substations
• Industrial power systems