Siemens SIPROTEC 5 7SS85 Busbar Protection Relay

The Siemens SIPROTEC 5 7SS85 is an advanced numerical relay designed for centralized busbar protection in medium-, high-, and extra-high-voltage power systems. Built on the powerful SIPROTEC 5 platform, it provides fast, selective, and reliable protection against busbar faults, ensuring system stability and minimizing equipment damage.

The relay operates based on the differential protection principle, enabling accurate detection of internal faults and rapid isolation of faulty sections. Its high-speed tripping capability significantly reduces fault-clearing time, enhancing operational safety and network reliability.

Designed for modern digital substations, the 7SS85 supports both centralized and distributed protection architectures. It can function as a central unit while integrating seamlessly with bay units and merging units via IEC 61850 communication. This flexibility allows it to adapt to complex substation configurations and evolving grid requirements.

With DIGSI 5 engineering support, modular hardware design, and advanced cybersecurity features, the SIPROTEC 5 7SS85 is an ideal solution for utilities, industrial plants, and infrastructure systems requiring dependable busbar protection.

Technical Specifications / Features

Protection Functions

• Busbar differential protection (87B)
• Phase-selective fault detection
• Disconnector-independent check zone protection
• High-speed fault detection and tripping (<7 ms)
• Stable operation during external faults and CT saturation

System & Application Features

• Suitable for MV, HV, and EHV systems
• Supports multiple substation configurations:
  • Single, double, and triple busbars
  • Breaker-and-a-half schemes
  • Ring bus and mesh configurations
• Can be used as:
  • Centralized busbar protection
  • Distributed busbar protection (with bay units)

Hardware & Configuration

• Modular SIPROTEC 5 architecture
• Supports large system configurations:
  • Up to ~20 current measuring points
  • Up to ~26 bays and multiple bus zones
• Expandable and flexible I/O configuration
• Adaptable to complex protection schemes

Communication & Integration

• Full IEC 61850 compliance (process bus & station bus)
• Supports GOOSE messaging and Sampled Values
• Seamless integration with digital substations
• Compatible with the DIGSI 5 engineering tool
• Supports centralized, decentralized, and hybrid architectures

Performance & Reliability

• Ultra-fast tripping for minimal fault impact
• High stability even under heavy fault currents
• Proven SIPROTEC algorithms for reliable operation
• Maintains system stability during disturbances

Cybersecurity

• Role-based access control
• Secure firmware with digital signatures
• Compliance with modern cybersecurity standards (IEEE 802.1X, logging)

Additional Features

• Integrated monitoring and control functions
• Event and disturbance recording
• Scalable for future system expansion
• Flexible engineering using DIGSI 5