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Frequently asked questions


ETOS® stands for "Embedded Transformer Operating System" and is an integrated system solution from MR for all automation and monitoring functions on a power transformer. In addition, ETOS® is our response to all of the challenges relating to concepts from reliability and data security for components to end-to-end consideration for the value chain – from ordering and commissioning to operations management.

  • ETOS® is the first open operating system for power transformers.
  • ETOS® is manufacturer independent.
  • ETOS® is a control and monitoring concept on the transformer.
  • ETOS® is a data integrator and a central communication interface.
  • ETOS® is a control cabinet for optimizing the value chain at the OEM and for function integration.
  • Modular control-cabinet concept. Unrestricted component selection.
  • ISM® (Intelligent Smart Modules) hardware and software architecture. Proven and intelligent industrial electronics.
  • Intelligent sensors and accessories
  • Strong global logistics performance.
  • MR as partner: Always local anywhere in the world for all services.

An operating system is a combination of various programs that manages the components (OLTC, bushing, etc.) of equipment (power transformer) and makes it available for applications.

Thus, the operating system forms an interface between the components and the application through the user or the user software. The heart of ETOS® consists of our ISM® software architecture. It manages the subsystems (DGA, cooling, etc.) and assemblies of the transformer and makes special programs available or manages the customer-specific applications.

The tasks include user communication, loading, executing, pausing and ending programs, ensuring system stability, management and operation of the connected devices and applications, as well as protective functions (such as access restrictions and cyber security).


ETOS® is the real-world expression of our conviction that power transformer automation and communication are the answer to future questions about grid management and operations management given that power transformers are such crucial equipment.


Many different sensor and monitoring systems are getting pushed onto the global market. Clarification of the specification, connection and integration at the power transformer poses major challenges for manufacturers. Sensor systems and automation tasks are not normally integrated or have only sporadic integration at best. Sensor signals frequently even have to be recorded several times.

Power transformers today still communicate through wires in many cases. So far it has not been possible to take advantage of the potential provided by data integration and local intelligence as is common in other industries. Neither has it been possible to use the dynamic (real) data and models of the equipment or to optimize operations or asset management using simulations and forecasting. There is immense hidden potential here.


In asset management, standardization in everyday equipment handling is very important. The basis for this is provided by data in digital form, collected from the time of power transformer acceptance at the installation site (SAT) up to final shutdown. This ranges from operation to troubleshooting and repair to stock-keeping and availability of spare parts. With ETOS® we offer an open standard that transcends manufacturers. We are available as your dependable, long-term partner in all of these challenges as we head into the future.

Power transformers today still communicate through wires in many cases. Using state-of the-art communication technology (fiber optics) leads not only to a significant cost reduction (CAPEX), but also to more reliable communication and considerably easier upgradability. In very simplified terms, the existing protocol conversion moves a bit closer to the equipment.

In addition to a function for easy data integration and monitoring, ETOS® offers numerous optional functions for evaluating your equipment in asset management. You can access interpreted information (such as a health index) or access all the data and carry out your own data analyses. That can reduce service work, assist with troubleshooting and make investment decisions easier.

We are convinced that the availability of information and dynamic models (simulation, digital twin) offers high potential for grid management. This has already been addressed many times in the course of discussions related to grid automation and utilization. Initial talks with manufacturers of control systems and grid simulation tools have confirmed this high potential. Topics such as attaining temporary overload capability through combining forecast data as well as proactive cooling are the first signs of things to come.


Customer diversity in conjunction with the relatively small world market (20,000 – 50,000 power transformers/year) make it difficult for an individual transformer manufacturer to develop a systematic solution from an economic point of view. This leads to singular solutions, high rates of change and a suboptimal value chain overall.

ETOS® is system-cost neutral for you. This means that, thanks to economies of scale at MR and by concentrating on your own areas of expertise in producing and evaluating transformers, you have a significant advantage in your value chain and costs as a whole also do not increase (process optimization). In addition, the concept provides significant differentiation potential through in-house systems and/or software functions (based on the ETOS® tool kit) and enables individualized digital business models.


There are still network operators who have concerns about electronics in transformers. They use the justification that electronics cost a lot of money, provide unusable data, offer hardly any added value and create more problems than benefits during their (short) service life.

In reality, however, there are basically no control cabinets in the field which operate without any electronics at all (measuring transducers, power supply units, etc.). Even in primary substations, electronic components have long been the state of the art. The problem was and is the use of unsuitable industrial components, which do not withstand the conditions in which they are used on power transformers. The industry is coming out of a pioneering phase in which numerous companies tried out many approaches based on available technology. To some extent there were and still are no defined standards regarding service life, environmental conditions, communication and data structures, range of functions, and methods. Many companies had hardly any experience at all in developing and manufacturing electronics. This led to the situation today where the term "monitoring" is viewed very critically.

In the meantime, standards committees have been tightening their rules and there are now defined standards and application rules for data standards, communication and numerous monitoring functions. The gap has also been closed in terms of hardware requirements. We offer 45 years of experience with electronic systems on transformers as well as operating experience from several thousand intelligent systems.

The development of ETOS® represents the first successful approach to a system solution that does not increase the overall system costs of the transformer. Our innovative housing concept and trusted ISM® technology allow us to overcome the environmental conditions on the transformer and ensure the reliability and lifespan standards in primary substations without any problems.


Control cabinet

Yes, that is possible without any difficulties in most cases. If, for example, you are looking for a combination of tap-changer drive, automatic voltage regulation and a monitoring function for the transformer, you could easily implement these with ETOS®. In individual cases (or on request), functions are allocated to several control cabinets.


Yes, that is possible. We can suggest a viable connection diagram or you can simply provide us with a template to use in configuring ETOS® for you.


There are currently 4 housing sizes; other versions are to follow. You can find the exact dimensions in the data sheet available in our download center.


There are corrosive classes available up to CX (in accordance with ISO 12944-9). Further information can be found in the data sheet available in our download center.


Functions / Software

Once you have selected a smart monitoring function (e.g. OLTC monitoring or DGA monitoring) or smart cooling system control/monitoring, ETOS® always includes "Transformer Monitoring" in the standard scope.


We have more than 45 years of experience with electronic field devices. The security of our components is an integral part of our philosophy and we take extensive measures to safeguard our field device (e.g. integrated firewall, encrypted communication, logs, role-based access control, external auditing). In addition, our CERT team is available if you have any questions.

You can find more information on cyber security here


Yes, the TPLE function lets you do this yourself without difficulty. The corresponding programming function is separate from the actual field-device function and optionally available. Inputs and outputs can be connected using a simple combination of function blocks.


  • Calculation of differences of analog signals (e.g. temperature difference between transformer and tap changer)
  • Warnings or alarms for individual inputs, e.g. inserted OLTC hand crank, open door of the motor drive or the control room (door sensor to be provided by customer)
  • Signals for different oil levels
  • Invert signals (NO -> NC, NC -> NO)
  • individual filters for unstable signals
  • Doubling of digital signals (e.g. for additional signal lamps)
  • Creation of individual AND / OR controls (e.g. for collective signals for different sensors)