Siemens SIPROTEC 5 6MD85 Bay Controller, Protection & Control Unit

The Siemens SIPROTEC 5 6MD85 is a powerful and modular bay controller, protection, and control unit designed for medium-, high-, and extra-high-voltage substations. It integrates control, automation, monitoring, and protection functions into a single device, making it a key component in modern digital substations.

Built on the SIPROTEC 5 platform, the 6MD85 provides flexible and scalable solutions for a wide range of applications, including feeder control, switchgear automation, and substation bay management. It supports extensive protection functions from the SIPROTEC library and allows application-specific I/O configuration.

The device enables reliable operation of power systems by combining bay control with protection functions, ensuring safe switching operations, interlocking, and system monitoring. With DIGSI 5 engineering and IEC 61850 communication, it offers seamless integration into digital substation architectures.

Main Function

• Bay Control
• Protection & Control
• Substation Automation

Tripping / Control

• Control of switching devices (circuit breakers, disconnectors)
• Backup protection tripping
• Interlocking and synchrocheck functions

Technical Specifications

Protection & Functional Features

• Integrated bay controller with protection functions
• Supports:
  • Feeder protection
  • Backup protection schemes
• Controls up to ~20 switching devices
• Includes:
  • Switchgear interlocking
  • Synchrocheck functionality
• Enables:
  • Safe switching operations
  • Reliable automation of substations
• Provides:
  • Fault recording
  • Measurement and monitoring functions

Hardware & Modular Design

• Fully modular and expandable I/O configuration
• 5 predefined standard variants available
• Typical configurations:
  • CT inputs: 4
  • VT inputs: 4
  • Binary inputs: 11 to 75
  • Binary outputs: 9 to 41
• Flexible I/O scaling within SIPROTEC 5 platform
• Conformal coating for harsh environmental conditions
• Scalable for future expansion

Communication & Protocols

• IEC 61850-8-1 / 9-2 compliant
• GOOSE messaging for high-speed communication
• Supports:
  • PRP / HSR redundancy
  • Multiple communication modules (up to 4)
• Enables seamless integration into digital substations

Engineering & Software

• Configurable via DIGSI 5 engineering tool
• Application templates for:
  • Standard feeder applications
  • Switchgear interlocking
• Graphical logic configuration (CFC)
• Simplified commissioning, testing, and diagnostics

Advanced / Latest Features (2024–2026 Update)

• Web-based access for monitoring and diagnostics
• Advanced cybersecurity:
  • Role-based access control
  • Signed firmware & secure communication
• Digital Twin support for simulation and testing
• Integrated PMU (Phasor Measurement Unit) functionality
• Power Quality monitoring (PQ Basic)
• High availability with redundant communication architecture

Applications

• Substation bay control (HV/EHV/MV)
• Switchgear automation systems
• Feeder bay control and protection
• Double busbar and 1½ breaker schemes
• Utility substations
• Industrial power systems