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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.


    Every ETOS® system is fully tested (hardware and software) in our factory before delivery.


    Control cabinet / Hardware

    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 3 different housing sizes available for each ETOS® design:
    S (height approx. 850)
    L (height approx. 1350)
    XL (height approx. 1800)

    You can find the exact dimensions in the corresponding operating instructions available in our download center.

    With regard to the functions and requirements you have chosen, we will select the right housing for you.


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


    Both the MR tap changer and the corresponding drive (TAPMOTION® or ETOS®) are designed to work for the entire service life of the transformer. Recommendations for maintenance intervals are noted in the respective operating instructions of the products.

    The following applies to the integrated ISM® electronics:

    • The ISM® electronics installed in the ETOS® are designed for the extreme conditions in the immediate surroundings of the transformer. The permitted ambient temperature range during operation is -25°C to +70°C; for ETOS® ED, lower ambient temperatures are also possible.
    • Based on experience in the field and comprehensive component testing, a reliable service life of 15 to 20 years can be guaranteed.
    • MR has been intensely focused on the automation of transformers for more than 40 years. This experience gained over many years is a major contributor to the reliability of the components installed in ETOS®.
    • The settings and data of the ISM® components can be backed up locally and remotely at any time. We recommend backing up the settings and data once a year, for example during inspection of the transformer/tap changer. This will ensure that your data is always available and can be restored as needed.

    If an ISM® component has to be replaced, for example because it is defective or as part of an upgrade, it is therefore easy to replace the respective assembly.


    The brightness of the display is measured in candelas per square meter (cd/m2). The higher this value is, the brighter the screen. During daylight hours or when the display is in indirect sunlight, a brightness of between 100 and 140 cd/m2 should be possible.

    The brightness of the integrated MControl touch display is 400-450 cd/m2, making it easy to read.

    Because direct sunlight can result in a brightness of 1000 cd/m2 and higher, we recommend providing a shade for the screen.


    Internal tests have demonstrated that the failure rate of the display is extremely low, even during continuous operation. Nevertheless, we recommend activating the integrated screen saver during continuous operation since this will significantly increase the service life of the display. In general, it is possible to use the display as a WTI and/or OTI replacement.

    Alternatively, if permanently visible display instruments are installed in ETOS®, we recommend an analog or digital circular instrument that is positioned so as to be visible from the ETOS®.


    The number of inputs varies greatly depending on the configuration. As a rule, there are 4 analog inputs and outputs. These are supplemented by 28 or 42 digital inputs and 15 or 20 digital outputs. Further inputs and outputs can be added depending on the scope and the respective application.

    Depending on the selected ETOS® functions, both digital and analog inputs and outputs may already be reserved.


    First, tell us what changes or added functions you are interested in along with the serial number of your device. We will then check which software/hardware versions you have, and based on this information, find an economic, simple option for implementing the desired additional functions.

    In the simplest case, this will only require a software update and perhaps a small amount of rewiring on location. If a new connection diagram is required, this will be included in the order.

    Naturally, our technical service team is happy to advise you in these matters.


    Depending on customer requirements, different types of clamps can be installed. Many common standard terminals are already available.


    Yes, ETOS® complies with the standards for power transformers applicable to the North American market. This also applies to integrated components in which ETOS® systems are housed (IEEE Std. C57.148 standard).


    Depending on the size of the housing, the following options are theoretically possible:

    Intelligent cooling system control (ISM® modules) for up to 4 cooling stages for conventional fans It is possible to combine various modules
    Intelligent cooling system monitoring (ISM® modules) for up to 6 cooling stages for conventional fans
    Integration of the power unit of a conventional cooling system (motor protection device, miniature circuit breakers) for 1 or 2 cooling stages. For more than 2 cooling stages, the space requirements must be analyzed.
    Frequency-controlled cooling system control (via ISM® modules)

    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)

    The values measured by all connected sensors are recorded in the ETOS® data logger. Depending on the type and scope of the measured data recorded, any chosen period data may be read out at a later date. The ETOS® data logger can record up to one million events such as, for example, an oil temperature limit value being exceeded.

    Depending on the settings, digital signals, such as the status of the Buchholz relay, can be recorded for 6 days (average interval 1 s) or even for up to 1,340 years (average interval 24 h).

    Analog signals (e.g. temperature values) can be documented for a period of up to 11 years (average interval 1 h). Depending on the version of ETOS®, the recording period can be even longer.


    ISM® technology forms the basis of ETOS®. Its modules are equipped with a durable operating system that has been optimized for use with energy technology. The system has been designed in accordance with the standards for state-of-the-art industrial automation. It includes:

    • 32-bit technology for fast signal processing cycle times
    • SNTP or IEEE1588 time synchronization
    • Web-based visualization based on the HTML 5 standard taking W3C recommendations into consideration
    • Multilingual user interface
    • Pre-installed documentation
    • HTML help

    A software update is required, for example, if the functions change or if there are relevant security updates. MR has its own CERT team that continuously monitors ISM® technology for weak points. The software can be updated directly on location via the USB interface or remotely via a remote interface.


    The various function packages, such as transformer monitoring and OLTC monitoring, are described on the MR website

    This includes, for example, a CPU assembly as well as modules for analog and digital measured values, measuring cards and protocol converters. The ISM® modules are flexibly and economically adapted to the desired function packages. The assignment of function to hardware depends on the specified configuration.


    No, the IEC 61850 communication protocol is optional and must be added separately (connection with RJ45 or fiber-optic cable).


    You can access the visualizations of the ISM® modules locally (MControl display or RJ45 interface with laptop) and remotely. No additional software is required.

    In order to carry out control functions or to set a parameter, the user must have corresponding authorizations in the system. Via an intuitive user management system, the different users can be assigned various roles with clearly defined system authorizations (e.g. authorization to change parameters or import or export data).

    When the MControl display is accessed remotely, manual control commands such as raise / lower (similar to those of a TAPCON® voltage regulator) can also be made from the visualization, depending on the role of the user.


    In terms of software, it is possible to reproduce signals/contacts with the TPLE function. Furthermore, digital and analog inputs and outputs can be programmed freely.


    Frequency-controlled cooling system control offers infinitely variable control of the cooling system based on the oil temperature and the load factor of the transformer. The fan speed is controlled by a configurable speed characteristic that is based on the oil temperature and load factor.


    • Effective temperature management with minimal noise emissions
    • Improved performance of the existing cooling system by exceeding the nominal speed by 50 Hz
    • Reduced volume of the cooling system
    • Allows for the installation of a larger active part with the same overall volume
    • Reduced auxiliary energy consumption
    • Reduced component wear

    All combinations of cooling methods are possible (ONAN, ONAF, ODAF, ODWF). Depending on the available space in the control cabinet, we select a suitable housing type for you.


    Generally, it is possible to connect sensors from MR or other manufacturers. Any sensor with standard Modbus RTU protocol can be connected to ETOS®. Up to 255 sensors can be connected via Modbus RTU.

    For example:

    • DGA sensors
    • Systems for bushing monitoring
    • Fiber-Optic temperature sensors
    • Partial discharge sensors
    • ...

    The standard user interface is a web-based visualization based on the HTML 5 standard. It can be accessed with any up-to-date web browser.


    For ETOS®, cloud is an option, but not mandatory. This means that ETOS® is fully functional even without a connection to the cloud, but if wireless communication is required, we will be happy to help you implement it.