Siemens SIPROTEC 5 7SK85 Motor Protection Relay

The Siemens SIPROTEC 5 7SK85 is a high-performance modular motor protection relay designed for protecting motors in industrial and utility power systems. Built on the advanced SIPROTEC 5 platform, it provides fast, selective, and reliable protection to ensure safe and efficient motor operation.

The relay is specifically engineered to handle all types of motors, including asynchronous (induction) motors, synchronous motors, and high-voltage motors. It offers comprehensive protection against electrical and thermal faults, ensuring maximum equipment safety and reduced downtime.

With its modular and expandable I/O architecture, the 7SK85 allows flexible configuration tailored to specific applications. It integrates protection, control, automation, monitoring, and power quality functions into a single device, making it ideal for modern digital substations and industrial automation systems.

Engineered using DIGSI 5 and supporting IEC 61850 communication, the relay enables seamless system integration, advanced automation, and enhanced cybersecurity for future-ready operations.

Main Function

• Motor Protection

Tripping

• 3-pole tripping
• Fast fault detection and isolation

Technical Specifications

Protection & Functional Features

• Comprehensive motor protection for:
  • Induction motors
  • Synchronous motors
  • High-voltage motors
• Protection functions include:
  • Thermal overload protection
  • Overcurrent protection
  • Earth fault protection
  • Negative sequence (unbalance) protection
  • Stall and locked rotor protection
  • Underload/loss of load protection
• Ensures:
  • Safe motor startup and operation
  • Protection against overheating and mechanical stress

Hardware & Modular Design

• Fully modular and expandable I/O configuration
• Flexible configuration based on motor size and application
• Typical configurations:
  • CT/VT inputs configurable
  • Binary inputs: ~5 to 31
  • Binary outputs: ~8 to 46
• Scalable design for future expansion
• Conformal coating for harsh environments

Communication & Protocols

• IEC 61850 Edition 1 / 2 / 2.1 compliant
• GOOSE messaging for high-speed communication
• Supports:
  • PRP / HSR redundancy
  • Modbus TCP, DNP3
• Enables seamless integration into digital substations and industrial systems

Engineering & Software

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

Advanced / Latest Features (2024–2026 Update)

• Web-based user interface for monitoring and diagnostics
• Advanced cybersecurity:
  • Role-based access control (RBAC)
  • Secure communication and firmware
• Digital Twin support for simulation and testing
• Process bus ready (Sampled Values support)
• Power Quality monitoring (PQ Basic)
• PMU functionality for advanced monitoring

Applications

• Industrial motor protection (HV/MV motors)
• Oil & gas industries
• Power plants
• Manufacturing industries
• Pumps, compressors, conveyors, and large drives