Protection for digital substations

High-performance protection makes your power supply future-proof

Protection is essential for network operators, electricity suppliers, and industrial enterprises in every sector. For over 100 years, Siemens has been offering successful and always innovative protection technologies. This means long-term user satisfaction with the products and solutions, with services, and with a partnership with a genuine global player. Siemens is the ideal partner for overcoming the challenges of the digital future.

Highlights, technical applications and product updates for substation automation and protection engineers.

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Protection products - Secure and efficient network operation



With modularly designed hardware and software and its high-performance DIGSI 5 engineering tool, the SIPROTEC 5 product family of field devices is perfect for protection, control, monitoring, and measuring applications in electrical energy systems. SIPROTEC 5 offers a wide product range with modular elements for every application and requirement.



We are committed to high technology development and manufacture with full use of the latest software at all stages of product development, manufacture and testing. This can be seen in the latest digital products that REYROLLE offer and is continuing with new innovations as part of the Siemens group.



Perfectly suited for protection in distribution systems and industry, with minimal space requirement SIPROTEC Compact devices provide a comprehensive range of functions in a surprisingly compact and space-saving housing. Whether as main or as backup protection, a single SIPROTEC Compact device provides protection functionality for every conceivable fault. And it can do even more – it supports the control, automation, and monitoring functions in the substation.



SIPROTEC 4 leads the way in integrating protection, control, measurement, and automation functions in one device. The homogenous system platform, the unique DIGSI 4 engineering program, and extensive experience of more than a million successfully operating devices in the field worldwide – thanks to these unique advantages, SIPROTEC 4 enjoys top recognition among users worldwide.



SIPROTEC and REYROLLE devices can be simply, reliably and safely engineered, adjusted, controlled, automated and evaluated with state-of-the art software.



Siemens offers a comprehensive selection of accessories for its protection technology products. This allows further expansion of the application possibilities and the performance.

New features in SIPROTEC 5 Version 7.8


Modular, flexible, intelligent

With SIPROTEC 5, Siemens is offering the most comprehensive protection portfolio in the industry.

SIPROTEC 5 sets the benchmark for protecting, automating, and monitoring your network. As an incomparably modular, flexible generation of intelligent digital field devices, SIPROTEC 5 offers a comprehensive product family with modular elements for every application and requirement that can be precisely configured to your application.

SIPROTEC 5 delivers maximum protection and flexibility throughout the entire lifecycle. Take advantage of the leading provider in the field of protection, a global partner that supports you every step of the way.

Learn more about SIPROTEC 5

Online configurator

Design your perfect solution with SIPROTEC 5 using our online configurator. You’ll have your solution of choice, in just a few mouse clicks.

Online configurator

Reyrolle Protection Relays

Protection Relay and Control technology

Reyrolle continues its tradition of quality protection relays and control devices.

Uncompromising to achieve maximum performance: We are committed to high technology development and manufacture with full use of the latest software at all stages of product development, manufacture, and testing. This can be seen in the latest digital products that Reyrolle offers and is continuing with new innovations as part of Siemens.

Learn more about Reyrolle protective relays

Innovation highlights

Performance that moves you forward

A new flexible generation of innovative and intelligent field devices. Learn more about how SIPROTEC 5 can support you in your work.
Other highlights

Protection devices for your success

For over a century, innovative protection relay and control technology from Siemens has ensured a reliable power supply as well as secure and efficient grid operations. The comprehensive range of products and solutions meets all conceivable requirements. Here are some examples.

Transient Ground Fault Function

Low-impedance ground faults are generally managed reliably with protection devices like the SIPROTEC 7SN60. The high sampling rate of SIPROTEC 5 devices allows for the integration of new, sensitive digital procedures for the reliable detection of high-impedance ground faults. The parts of the signal which are caused by the discharging and charging of the ground capacitances of the grid are of particular interest here. The active power in the zero-sequence system is a good criterion to detect the direction of the ground fault. As the charging takes place over a longer period of time with high-impedance ground faults, this part of the active power is available during this time period and can be integrated right from the ignition of the fault. This results in the active energy in the zero-sequence system. 

Radial systems do not pose a problem for determining the direction. In meshed systems, operational zero-sequence currents can falsify the resulting direction. These operational zero-sequence currents are eliminated by the new algorithm in order to determine the correct direction.


  • Enhances availability, conserves equipment
  • Cost savings thanks to integration in SIPROTEC 5
  • Very high sensitivity - detection of high impedance faults with fault resistances of up to 5 kOhms
  • Detection of very short ground faults of few milliseconds
  • Ideally suited for closed loops or meshed systems, as not impacted by operational zero-sequence currents
  • Easy setup of the function

Arc Protection

Arc fault protection is a relatively new technique employed for the fast clearance of arcing faults on busbars and within metal clad switchgear & associated cable boxes. The arc is detected using an optical sensor & the signal input to a protection device which also monitors the load current on the system. Conventional current based protection techniques are at times challenged by the nature of arcing faults, and can result in slow protection clearance times. Slow protection clearance times increase the risk to nearby personnel and increase the degree of damage to plant and equipment. By employing an optical detection technique, Arc Fault Protection results in fast clearance of arcing faults.


Phasor Measurement Units (PMUs) and its measured synchrophasors make a valuable contribution to the dynamic monitoring of transient processes in energy supply systems. Phasor Measurement Units (PMUs) measure current and voltage by amplitude and phase at selected stations of the transmission system. The high-precision time synchronization (via GPS) allows comparing measured values (synchrophasors) from different substations far apart and drawing conclusions as to the system state and dynamic events such as power swing conditions. 

All SIPROTEC 5 devices can be used as a Phasor Measurement Unit. When selecting the option “Phasor Measurement Unit”, the devices determine current and voltage phasors, provide them with highly accurate time stamps and transmit them for analysis together with other measured values (frequency, speed of frequency change) using the IEEE C37.118 communication protocol, which are typically sent to the control center.

SIGUARD PDP (Phasor Data Processor) is a system for Wide Area Monitoring and Grid Monitoring that, as its measured variables, uses synchrophasors from phasor measurement units serving as sensors. It helps with quick recognition of the current network situation and indicates both power swings and transient phenomena, transparently as well as instantly. Replication of the respective network topology is not required. The tool supports control center personnel in assessing critical grid situations and contributes to the taking of suitable action. As all measured results are stored, power system disturbances can be promptly analyzed.

Process bus with SIPROTEC

Measurement of voltages and currents is necessary for protection. Currently sensors, delivering analog values, are directly wired to the protection devices. Since the relays in a substation are normally situated in a central building this wiring has to cover a distance. In an EMC critical area like a high-voltage substation this demands high power signals resulting in big copper cables. For conventional instrument transformers this is proven technology.

In process bus a new approach is used. Instead of wiring the protection devices to the sensors a Merging Unit is placed near the sensor. The Merging Unit digitalizes the analog values and sends them via a Sampled Measured Value stream to one or more protection devices. The Sampled Measured Value stream is transmitted using fiber optical Ethernet, where EMC is no issue. As an additional advantage this enables new sensors that are not capable of generating high power signals. The relays no longer have to sample the analog values but directly use the digital values out of the Sampled Value Stream.

Today's conventional instrument transformers provide an analog signal representing the high voltage signal. This is interoperable by definition. Measurement is done directly in the relays. In process bus the interoperable interface is generated by the Merging Unit. The Merging unit works as a converting device. It converts proprietary sensor outputs to a standardized Ethernet based output. This additionally supports non-conventional instrument transformer.

To fashion interoperable devices in Energy Automation systems IEC 61850 was created. The standard not only covers message interchange based on IEC 61850-8-1 which is nowadays state of the art technology. In IEC 61850-9-2 the digital representation of analog values is standardized. This standard is the base for an interoperable process bus. Siemens supports IEC 61850-9-2 interface and focuses on interoperable solutions.


  • Minimize wiring by measuring directly at the sensors, operating at a central position and use of fiber optical Ethernet
  • Enhanced safety by avoiding open wire condition at relays
  • Easier extension / maintenance, adding a device only connection to the network necessary. No direct connection to the sensors required
  • Maximum network reliability, through seamless redundancy protocols
  • Interoperability ensured, standardized in IEC 61850-9-2
  • Merging Units for conventional CT/VT offer process bus advantages without change in primary equipment

Capacitor Bank Protection

Reliably detect errors in capacitor banks while protecting the filter circuit. Protect your capacitor banks and thereby maintain grid stability.

Engineering Software DIGSI 5

DIGSI 5 is the versatile engineering tool for parameterization, commissioning and operating all SIPROTEC 5 devices. Its innovative user interface includes context-sensitive user instructions. Simple connection to the device via USB enables you to work with a device easily and efficiently. The full capabilities of DIGSI 5 are revealed when you connect it to a network of protection devices: Then you can work with all of the devices in a substation in one project.

DIGSI 5 offers superior usability and is optimized for your work processes. Only the information you actually need to carry out your tasks is shown. These can be reduced further using expanded filter mechanisms. The consistent use of sophisticated, uniform mechanisms in the user interfaces requires less training.


Protection technology – proven worldwide

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