Transformer differential protection

Transformer differential protection – SIPROTEC 7UT82


The SIPROTEC 7UT82 transformer differential protection has been designed specifically for the protection of two-winding transformers. It is the main protection for the transformer and contains many other protection and monitoring functions. The additional protection functions can also be used as backup protection for subsequent protected objects (such as cables or lines). In this process, you are also supported by the modular expandability of the hardware. With its modular structure, flexibility and the powerful DIGSI 5 engineering tool, SIPROTEC 7UT82 offers future-oriented system solutions with high investment security and low operating costs.

Features & functions

Transformer differential protection SIPROTEC 7UT82


Main function:

  • 1 differential protection function (standard or auto transformer) with additional stabilization; up to 2 restricted ground-fault protection functions

Usable measuring Points:

  • 2 x 3-phase current measuring points,
  • 2 x 1- phase current measuring points

Inputs and outputs:

1 predefined standard variant with 

  • 8 current transformers, 
  • 7 binary inputs, 
  • 7 binary outputs

Hardware flexibility:

  • The 1/3 base module is available with the IO103 module; it is not possible to add 1/6 expansion modules, available with large and small display

Width of housing:

  • 1/3 × 19 inches

As standard:


DIGSI 5 permits all functions to be configured and combined as required.

  • Transformer differential protection for two-winding transformers with versatile, additional protection functions
  • Transformer differential protection for phase-angle regulating transformers of the single core type
  • Universal usability of the permissible measuring points
  • Applicable from average up to extra-high voltage
  • Protection of standard power transformers, auto transformers and motors
  • Increased sensitivity with near-neutral-point ground faults through a separate restricted ground-fault protection
  • Flexible adaptation to the transformer vector group
  • Controlling closing and overexcitation processes
  • Safe behavior in case of current-transformer saturation with different degrees of saturation
  • Adaptive adaptation of the operate curve to the transformer tap position
  • Arc protection
  • Graphical logic editor to create powerful automation functions in the device
  • Single line representation in small or large display
  • Integrated electrical Ethernet RJ45 for DIGSI 5 and IEC 61850 (reporting and GOOSE)
  • Up to 2 optional pluggable communication modules, usable for different and redundant protocols (IEC 61850-8-1,IEC 60870-5-103, IEC 60870-5-104, Modbus TCP, DNP3 serial and TCP, PROFINET IO)
  • Serial protection data communication via optical fibers, two-wire connections and communication networks 
  • (IEEE C37.94, and others), including automatic switchover between ring and chain topology
  • Reliable data transmission via PRP and HSR redundancy protocols
  • Extensive cyber security functionality, such as role-based access control (RBAC), protocolling security-related events or signed firmware
  • Simple, quick and secure access to device data via a standard Web browser – without additional software
  • Time synchronization using IEEE 1588
  • Powerful fault recording (buffer for a max. record time of 80 sec. at 8 kHz or 320 sec. at 2 kHz)
  • Auxiliary functions for simple tests and commissioning.


Application templates are available in DIGSI 5 for standard applications. They contain basic configurations and default settings. These can be used directly or as a template for application-related adaptation. The available measuring points make varied applications possible.




Two-winding transformer basis

  • Differential protection
  • Overload protection, backup protection for the downstream power system

Two-winding transformer with restricted ground-fault protection (REF)

  • Differential protection
  • Restricted ground-fault protection on the neutral side
  • Overload protection, backup protection for the downstream power system
  • Circuit-breaker failure protection


  • Compact and low-cost transformer differential protection
  • Safety due to powerful protection functions
  • Data security and transparency over the entire lifecycle of the plant, saving time and money
  • Purposeful and easy handling of devices and software thanks to a user-friendly design
  • Increased reliability and quality of the engineering process
  • Cyber security in accordance with NERC CIP and BDEW Whitepaper requirements
  • Highest availability even under extreme environmental conditions by “conformal coating“ of electronic boards
  • Powerful communication components warrant safe and effective solutions
  • Full compatibility between IEC 61850 Editions 1 and 2