Generator protection

Generator protection – SIPROTEC 7UM85


Modular SIPROTEC 7UM85 generator protection relays for the protection of generators and power plant units contain all necessary main protection functions and a large number of other protection and monitoring functions.

Generator protection SIPROTEC 7UM85

Features & functions

With its modular structure, flexibility and the powerful DIGSI 5 engineering tool, SIPROTEC 7UM85 offers future-oriented solutions for protection, control, automation, monitoring and PQ basic. For motors in explosive environments, the SIPROTEC 7UM85 is also available with EN 60079-14 or Verband der Elektrotechnik, Elektronik und Informationstechnik 0165, Part 1 (ATEX) certification


Main function:

  • Typical generator protection functions
  • Certification for use in explosive environments (EN 60079-14 or Verband der Elektrotechnik, Elektronik und Informationstechnik 0165, Part 1, ATEX)
  • SIL2 certification of hardware and software for generator reverse protection EN 61508

Inputs and outputs:

5 predefined standard variants with

  • up to 16 current transformers and 
  • 8 voltage transformers, 
  • 7 to 15 binary inputs,
  • 9 to 20 binary outputs
  • 4 fast measuring transducer inputs (10 V or 20 mA)

Hardware flexibility:

  • Flexibly adjustable and expandable I/O quantity structure within the scope of the modular SIPROTEC 5 system; 1/6 expansion modules can be added, available with large or small display, or without display

Width of housing:

  • 1/3 × 19 inches to 2 × 19 inches

As standard:


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

  • Short-circuit protection (overcurrent protection, impedance protection, differential protection)
  • Stator ground-fault protection (90% non-directional or directional, 100% with 3rd harmonic, real 100% protection with 20-Hz voltage interference)
  • Rotor ground-fault protection with different measuring methods (ground current or ground-resistance monitoring)
  • High-precision reverse-power protection and universal power protection
  • Underexcitation and overexcitation protection
  • Unbalanced-Load Protection
  • Overload protection and temperature supervision via external RTD unit (with PT 100, for example)
  • Out-of-Step  Protection
  • Rotor and stator overload protection with cold gas consideration (coolant temperature)
  • Power-plant disconnection protection
  • Shaft-current protection (in particular with hydropower applications)
  • Universal overvoltage and undervoltage protection with different measuring methods
  • Overfrequency and underfrequency protection, frequency change protection and monitoring of dwell time in frequency bands as turbine protection (protection against abnormal frequencies)
  • Protection functions for network decoupling (voltage and frequency protection, directional reactive power undervoltage protection (QU protection) and vector-jump protection)
  • Inadvertent energization protection to detect incorrect activation of the circuit breaker
  • Circuit-breaker failure protection
  • Point-on-wave switching
  • Circuit breaker reignition monitoring
  • Single-channel parallel connection function (synchronization) with adjustment commands for rotational speed (frequency) and voltage
  • Graphical logic editor to create powerful automation functions in the device
  • Integrated electrical Ethernet RJ45 for DIGSI 5 and IEC 61850 (reporting and GOOSE)
  • Up to 4 pluggable communication modules, usable for different and redundant protocols (IEC 61850-8-1, IEC 61850-9-2 Client, IEC 60870-5-103, IEC 60870-5-104, Modbus TCP, DNP3 serial and TCP, PROFINET IO, PROFINET IO S2 redundancy)
  • Virtual network sharing (IEEE 802.1Q - VLAN)
  • Reliable data transmission via PRP and HSR redundancy protocols
  • PQ-Basic: voltage unbalance; voltage changes: overvoltage, dip, interruption; TDD, THD and


  • Extensive cybersecurity functionality, such as role-based access control (RBAC), protocolling security-related events, signed firmware or authenticated network access IEEE 802.1X
  • Simple, quick and secure access to the device via a standard Web browser to display all information and diagnostic data, as well as vector diagrams, single-line and device display pages
  • Phasor Measurement Unit (PMU) for synchrophasor measured values and IEEE C37.118 protocol
  • Time synchronization using IEEE 1588

  • Capturing operational measured variables and protection function measured values for the evaluation of the system, to support commissioning, and to analyze faults

  • Frequency tracked protection functions over a wide frequency range (10 Hz to 80 Hz) and the option to assign the protection functions in a single device to different frequency tracking groups.

  • 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

  • Flexibly adjustable I/O quantity structure within the scope of the SIPROTEC 5 modular system



  • Protection of generators in busbar connection of different power, with directional stator ground-fault protection.

  • Protection of generators in unit connection of different power (using the 100% stator ground fault (20 Hz) with larger generators)

  • Protection of power plant units with one device per protection group. In the generator transformer variant, the 7UM85
    implements both generator and transformer protection.

  • In more complex power plant units (unit connection with generator circuit breaker and several auxiliary transformers),
    additional SIPROTEC 5 devices are used, – for example, 7UT8x, 7SJ82 or 7SJ85 and 7SA, SD, SL86, at the upper-voltage side of the generator transformer.

  • Using motor and generator protection functions (underexcitation protection, for example) to protect synchronous motors.
  • Acquisition and recording of power quality data in the medium voltage and subordinate low voltage network.




  • Safe and reliable automation and control of your systems
  • Purposeful and easy handling of devices and software thanks to a user-friendly design
  • Cybersecurity in accordance with NERC CIP and BDEW Whitepaper requirements
  • Highest availability even under extreme environmental conditions by “conformal coating“ of electronic boards



Downloads and services

Retrofit and enhancement services

Retrofit and enhancement services

Extend the lifespans of your energy system and thereby significantly reduce your costs of ownership with our retrofits and enhancement services for energy automation.

Power Academy training services

Power Academy training services

Our goal is to prepare you for new professional challenges in power transmission and distribution. We offer professional training courses with different training methods like Virtual Classroom Training, Classroom Training, WBTs, Webinars and Blended Learning. You can choose between open enrollment training courses, customized training courses, workshops or long-term trainings (curricula).

Energy Automation and Digital Grid Newsletter


Receive news about the Digital Grid and Energy Automation portfolio and offerings!

Energy Automation Webinars

Energy automation webinars

Learn more in one of our energy automation webinars for protection and substation automation engineers and experts.