The fundamentals of Dissolved Gas Analysis for power transformers Application guide | Team ECOSENSE® Contents Abstract 3 1 DGA (Dissolved Gas Analysis): Background and information 1.1 Problems with transformers – Why 4 do you need transformer monitoring? 1.2 The importance of monitoring 5 hydrogen, carbon monoxide, and moisture in DGA analysis 1.3 Gas values and their interpretation: 8 How to interpret DGA values? 1.4 The ECOSENSE® ROI calculator: 9 When the investment pays off 2 ECOSENSE® ACTIVE PART 10 Upgrade your transformer fleet's performance References 12 Abstract Transformers are crucial for ensuring a reliable power supply for production, and for the operation of critical infrastructure, with the electrical power supply one of the most important infrastructures of modern society. Since many transformers worldwide were built in the 1950s-70s, they are aging rapidly and could potentially benefit from the retrofitting of sensors. Continuous monitoring of these expensive assets is of great importance. Unfortunately, critical transformers are often rarely subjected to a health check, and even less often to ongoing data analysis through, for example, an online DGA (Dissolved Gas Analysis) sensor. Studies by CIGRE indicate that 45% of transformer failures are due to faults in the active part.⁸ Continuous monitoring of the active part by using an online DGA monitoring device to measure gas accumulations can make an important contribution to the monitoring and maintenance of transformers. Welcome to this introduction to dissolved gas analysis (DGA) and its importance for detecting faults and improving the safety of power transformers. In this document, we will discuss the issues caused by gases in the oil of the transformer and explain how measuring three components can help detect faults. We will also introduce ECOSENSE® ACTIVE PART as a tool for assisting with DGA and offering greater insight into the health status of transformers. By understanding the significance and use of DGA, we can improve the safety and availability of transformers. © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 3/13 1 Dissolved Gas Analysis: Background and Information 1.1 Problems with transformers: Why transformer monitoring is necessary This section provides a basic overview of the subject. It explains why you need DGA monitoring, as well as the benefits and importance of monitoring the active part of the transformer. Our electrical energy networks are being pushed to their limits by a number of factors, including aging transformer fleets, rising energy demand, increasing complexity, loss of competence due to generational changes, and increasing volatility. As a result, new solutions in operational and strategic asset management are required. For transformers, the identification of dissolved gases in the transformer oil is generally considered to be the first indication of potential failures. Multiple international standards including IEEE Std C57.104TM-2008, IEC 60422, IEC 60567, and IEC 5991-4 highlight the relevance of this testing procedure. The power grid as well as numerous industrial processes rely heavily on transformers as essential components. Monitoring of transformers decreases the risk to a company in several ways: + + + + + + Providing improved safety for employees and the general population Minimizing unexpected failures Minimizing the number of unplanned outages Reducing operational expenses through early intervention in the event of a failure Lowering insurance premiums Minimizing the risk of environmental contamination By gathering data and delivering alerts to the user if something appears abnormal, transformer monitoring systems actively check a transformer’s health to ensure appropriate operation. A variety of transformer monitors are available which monitor such factors as the cooling system, the on-load-tap-changer, dissolved gas in oil, bushing power factor and capacitance, partial discharge, oil levels, pressure, and temperatures, and can thus detect the indications of transformer failure. This introduction paper focuses on the active part of a power transformer, which includes the windings, cores and pressed parts that are subject to voltage and current stress, because these components are crucial to the proper functioning of transformers. © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 4/13 1.2 The importance of monitoring hydrogen, carbon monoxide, and moisture Accurate measurement of CO, H2 and moisture is essential for DGA, and a three-gas sensor offers many advantages over other types of gas sensors. In this section, we will explore the significance of these components and the benefits of using a three-gas sensor. The community commonly refers to three-component DGA as three-gas DGA, even though one of the components – water - is not necessarily in gaseous form. The three-gas DGA sensor ECOSENSE® ACTIVE PART detects three components in the insulating transformer fluid: hydrogen, carbon monoxide, and water. DGA sensors are also available which can measure five or more components, but these are also significantly more expensive. For such sensors, it is critical to assess whether the benefits of measuring the additional components outweigh the additional costs. However, before making this estimate, we need to discuss the significance of CO, H2 and moisture for DGA analysis. – Hydrogen H2 is produced under most fault-causing conditions. The challenge is to determine whether the H2 concentration corresponds to the normal behavior of the transformer or is increased due to an error. – Carbon monoxide CO is generated during the degradation of paper insulation from the windings in the active part and strongly affects the transformer lifetime. In most situations, replacing the paper insulation is too expensive, and the transformer must be permanently taken off the electricity grid and scrapped. Accelerated aging is therefore a financial and safety issue. – If water gets into the transformer, the relative moisture in the oil increases. Transformer oil acts as an electrical insulator and its quality depends on the oil's moisture content. At 40% relative moisture, breakdown voltage can be reduced by 50%⁵. This means that water molecules of only 25 ppm at 20° C or 68° F cause immediate insulation weakening and resulting difficulties. Early detection of moisture is therefore crucial for preventing these issues and ensuring the proper functioning of the transformer. © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 5/13 Hydrogen monitoring is an effective tool for detecting all potential transformer faults because these faults often produce large amounts of hydrogen as a byproduct of the breakdown of transformer oil. Figure 1 shows the gases produced by various fault types (which are explained below the figure). Hydrogen (blue) is the only gas produced across the entire range, making it suitable as an alarm gas for all shown fault types. The other gases (CH4, C2H2, C2H4, and C2H6) are not necessary for detection, but they can help with more precise identification of the defect type. These gases are typically analyzed in a DGA in the laboratory. By monitoring hydrogen levels, it is therefore possible to detect the early stages of these faults, which can help prevent significant damage to the transformer, thus improving transformer safety, efficiency and reliability, and increasing service life. Figure 1: Distribution of gas formation patterns at various temperatures at the point of gas formation in power transformers. ⁶ Power transformer faults can develop for a variety of reasons: – Cold plasma and catalytic faults can occur when there is a breakdown in the transformer oil, leading to the formation of a plasma discharge. This type of fault is often difficult to detect and can lead to significant damage if not addressed quickly. – Thermal faults can develop when a transformer overheats, which can be caused by a variety of factors including high load conditions, poor ventilation, or faulty insulation. These faults can be more easily detected than cold plasma and catalytic faults and can be addressed by reducing the load on the transformer or improving its ventilation. – Partial discharges, discharges in transformer oil, and arcing faults are three types of electrical faults that can cause transformer and equipment damages such as insulation degradation, short circuits, explosions, and fire. Poor maintenance, deteriorating insulation, oil contamination, and poor connections are the main reasons for these types of fault. © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 6/13 Continuous online monitoring of hydrogen and carbon monoxide as well as relative humidity enables early detection of potentially hazardous trends. As soon as defined warning limits are exceeded, additional analyses can then be performed and early countermeasures can be initiated. Costs for immediate action are typically much lower than for correcting the damages caused at a later time, or even after a transformer failure with the resulting follow-up costs. The online DGA system was created for this purpose. It continually monitors hydrogen and carbon-monoxide gas concentrations, as well as oil moisture, and sends warnings or alarm signals when defined gas or moisture concentrations are reached. It also indicates if increase rates are too fast because not only the absolute value of the gas concentration must be considered but also the development of the gas concentration over time. Three-gas DGA sensors often compete with multi-gas sensors which measure five or more transformer oil components. However, the latter are generally more expensive and have more parts which could potentially fail, thereby reducing their lifespan and increasing their maintenance requirements. Furthermore, such sensors are commonly unnecessary because when a fault is detected, a laboratory oil analysis is generally performed in which breakdown voltage, interfacial tension, electrical parameters, and density are analyzed to reliably identify the relevant components in detail. The three main components (CO, H2 and moisture) are therefore usually sufficient for an early warning system. i For more information please see the corresponding blog article "Why measuring only three gases is enough and saves you money" © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 7/13 1.3 DGA values and their interpretation DGA sensors thus provide data on gas concentrations in the insulating liquid of the active part. However, the interpretation of DGA sensor data is not always straightforward, as not all transformers can be treated in the same manner. When interpreting DGA values, it is therefore necessary to take into account the transformer's characteristics as these may influence the gas concentration and alter the interpretation results. The following are the most significant influences in this regard: – Load - Frequently, a highly loaded transformer will have increased gas values. This is influenced by current and temperature. – Volume - If two transformers are otherwise equal but one has more oil, its gasses are more diluted. The gasses are more diluted and DGA results are thus affected. – Insulating liquid - Numerous varieties of transformer oil are available and the type and quality can influence a transformer. For instance, at the same temperature, the ratio of the decomposition products in paraffinic and naphthenic oils is slightly different. – Inhibitors - The inhibitor's purpose is to prevent oxygen from reacting with the oil, thus slowing the aging process of the oil and the solid insulation. In order to compensate for the reduced CO content in transformer oil with inhibitors, the CO value must be adjusted accordingly. – Passivators - Transformer oil passivators reduce oil-on-metal contact. Passivators can increase gas values, especially for the hydrogen gas value H2. If your transformer oil contains passivators, a compensation must be made in the DGA interpretation for the H2 value. In case the above-mentioned criteria of influence can explain gas measurements, there is no cause of concern. The interpretation of DGA values requires considerable effort: Multiple factors must be addressed and several explanations for measured data must be explored. However, when you do, you are rewarded with a deeper understanding of your assets. You need to evaluate gas generation rates if your absolute gas concentrations are slightly elevated, but you are uncertain about the severity. You should be alarmed if there is a rapid upward trend that implies your concentrations will escalate significantly in a few months. i Please see our articles "The ultimate guide to DGA Interpretation" and "Two ways to calculate DGA trends" for more information on this challenging topic © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 8/13 1.4 The ECOSENSE® ROI calculator: When the investment pays off Return on investment (ROI) is a metric or business indicator that provides information about whether an investment is profitable, and when that investment has paid off. For DGA, this means that the benefits of online monitoring must outweigh the associated expenses. Implementing an online monitoring system using our method of analysis produces the following benefits: – Early fault detection – Undetected faults can cause a transformer to fail completely, resulting in potentially long delivery times and high re-procurement and delivery costs. In the event of catastrophic failures, follow-up costs such as environmental clean-up or compensation for bodily injuries may arise. Online monitoring helps spot defects early, thereby reducing or avoiding maintenance, repair and replacement costs or even compensation payments. – Reduced production losses – A transformer’s principal function is lost when it fails. This can result in contractual penalties or lost business, depending on the transformer application. Detecting emerging issues early can replace lengthier unplanned outages with shorter scheduled outages, thus lowering production losses. A device’s return on investment (ROI) can be determined by quantifying and calculating these benefits over a device’s lifetime and then deducting acquisition and installation costs. Even if no online-DGA system is implemented, offline DGA measurements should be carried out routinely. The advantage of online DGA systems in this regard is the reduction or elimination of offline measurements and the related cost savings. i For a more detailed description of determining ROI, including numbers, see: reinhausen.com/de/roi-calculator © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 9/13 2 ECOSENSE® ACTIVE PART Upgrade your transformer fleet's performance with ECOSENSE® ACTIVE PART Revitalize your transformers with the advanced technology of ECOSENSE® ACTIVE PART. This online sensor utilizes a three-gas DGA system that is quick and easy to order and install. By continuously monitoring your transformers, you can be notified of any issues before they become critical, giving you peace of mind and saving you valuable resources. With ECOSENSE® ACTIVE PART, you can maintain your transformer fleet without incurring excessive costs. Upgrade to the smart and cost-effective solution for transformer maintenance today. Affordable transformer equipment: The BUY ONLINE ONLY series of Maschinenfabrik Reinhausen The new product series BUY ONLINE ONLY offers a number of benefits to you as a customer. With our BUY ONLINE ONLY product series, you can equip your transformers for better reliability and reduced probability of faults and failures, while also saving valuable time and money. Our easy handling, optimized customer interactions, and global availability make the entire process stress-free. Our high-quality sensors start from just €3,900 (Price List: https://www.reinhausen.com/productdetail/sensors/ecosense-active-part) and can be easily installed with the help of our free instructional videos. Plus, our digital customer service is available around the clock for your peace of mind. i Price list https://www.reinhausen.com/productdetail/sensors/ecosense-active-part © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 10/13 Your journey with ECOSENSE® ACTIVE PART Installation & Commissioning Unpack and install via Plug & Play. 2 1 Order prozess Easy online ordering and fast worldwide shipping. 3 Continuous monitoring ECOSENSE® ACTIVE PART supports the early detection of transformer faults by means of continuous gas-in-oil analysis (Online DGA). 4 Gas limits exceeded If gas values are exceeded, the asset manager is informed via the Modbus protocol. 5 Oil analysis & result interpretation The early warning means that an oil sample can now be taken and an extended analysis can be carried out in the laboratory. Herewith it is possible to to carry out the correct measures on the transformer. 6 Continued operation with online DGA The early warnings of the DGA sensor, targeted oil analyses and, if necessary, quick repairs ensure the regular continued operation of the transformers without incurring high procurement and subsequent follow-up costs. Transformer good, everything good! © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 11/13 References [1] "IEEE Std C57.104TM-2008: IEEE Guide for the Selection of Instrument Transformers for Power and Power Measurement Systems." Institute of Electrical and Electronics Engineers, 2008. [2] IEC 60422: Insulated bushings for alternating voltages above 1 kV up to and including 36 kV." International Electrotechnical Commission, 2003. [3] IEC 60567: Insulating liquids - Determination of the breakdown voltage at power frequencies - Test methods." International Electrotechnical Commission, 2006. [4] IEC 599: Insulating liquids - Determination of relative permittivity, dielectric dissipation factor and d.c. resistance." International Electrotechnical Commission, 1997. [5] CIGRE (International Council on Large Electric Systems). (n.d.). 53 CIGRE TB 738: Papieralterung in Transformatoren. Technical report. Received from https://www.cigre.org/publications/technical-brochures/53-cigre-tb-738-paperageing-in-transformers [6] CIGRE Working Group JWG D1/A2.47, Advances in DGA interpretation, CIGRE Brochure 771, July 2019 [7] Duval, J. "Triangle for Diagnosing Overheating and Aging in Insulating Liquids." IEEE Transactions on Electrical Insulation, vol. 14, no. 4, 1979, pp. 502-509. [8] CIGRE WG A2.34, „Guide for Transformer Maintenance“ presented at the WG A 34, 2011, Vo. 445 © MR, Application guide The fundamentals of dissolved gas analysis for power transformers 12/13 Maschinenfabrik Reinhausen GmbH Falkensteinstraße 8 93059 Regensburg Germany +49 941 4090-0 info@reinhausen.com reinhausen.com Please note: The data in our publications may differ from the data of the devices delivered. We reserve the right to make changes without notice. The fundamentals of dissolved gas analysis for power transformers uw – 04/22 – ©Maschinenfabrik Reinhausen GmbH 2023 THE POWER BEHIND POWER.
