Siemens SIPROTEC 5 7UT82 Transformer Differential Protection Relay

The Siemens SIPROTEC 5 7UT82 is a compact and cost-optimized numerical relay designed for transformer differential protection of two-winding transformers. Built on the SIPROTEC 5 Compact platform, it integrates protection, control, monitoring, and automation functions into a single reliable device.

The relay serves as the main protection for transformers, ensuring fast and selective fault detection while also offering additional protection functions for downstream equipment such as cables, lines, and reactors.

Its advanced differential protection algorithm ensures high sensitivity and stability, even during challenging conditions like transformer inrush currents, overexcitation, and CT saturation. With seamless integration into digital substations using IEC 61850 and configuration via DIGSI 5, the 7UT82 provides a future-ready and cost-effective protection solution.

The compact design, conformal coating, and built-in cybersecurity features make it suitable for utilities and industrial applications requiring high availability and reliable transformer protection.

Main Function

• Differential protection for two-winding transformers
• Suitable for standard and auto transformers
• Backup protection for connected equipment (lines, cables, reactors)

Tripping

• Fast and selective tripping based on the differential protection principle
• High-speed fault clearance for internal transformer faults

Inputs and Outputs

• Standard configuration:
  • Up to 8 current transformer (CT) inputs
  • 7 binary inputs
  • 6–7 binary outputs

Hardware Flexibility

• Compact SIPROTEC 5 design with fixed I/O configuration
• Single predefined hardware variant (cost-optimized)
• No expansion modules supported
• Configurable using the DIGSI 5 engineering tool

Housing

• Compact 1/3 × 19-inch housing
• Available with a small or large display
• Conformal coating for harsh environmental conditions

Function (Key Features)

• Transformer differential protection with stabilization
• Up to 2 restricted earth fault protection functions
• Adaptive to different transformer vector groups
• Inrush current and overexcitation detection
• Backup protection functions (overcurrent, overload)
• Fault recording and disturbance analysis
• Basic power quality monitoring
• IEC 61850 communication (digital substation ready)
• Cybersecurity features:
  • Role-based access control
  • Secure firmware & communication
• Time synchronization and event logging for analysis