Whether in an industrial or utility application, power transformers are among the most critical assets of any power system required to maintain the reliable and efficient flow of electricity. Condition and risk assessment of these valuable assets is needed more than ever. With the average age of a transformer fleet over 40 years and new transformer fleets experiencing a greater-than-expected failure rate, a proactive approach to transformer monitoring is required. With 52% of transformer failures caused by insulation degradation, ageing and electrical abnormalities such as through faults, extending the life of these devices through early detection or even prediction of these failure models has become a top priority for power system engineers
Integrated Approach to Asset Protection
These critical assets require more than just electrical measurement for protection and control; a transformer’s insulating oil must also be monitored for abnormal conditions. Historically, this type of chemical monitoring involved asset management teams dispatching a technician to each transformer to take oil samples.
These samples were sent to a lab for analysis and a condition report was issued. As the technology evolved, online dissolved gas analysis (DGA) devices were introduced, capable of drawing oil samples on their own on a regular basis. These devices get connected to communication networks, allowing asset managers to remotely collect and monitor the transformer’s health condition.
Applying Monitoring and Diagnostic Capabilities to a Wide Range of Transformers
Transformer monitoring and diagnosis are scalable, depending on the type of transformer. For small dry-type transformers, essential monitoring is likely all that is required, including breaker monitoring, harmonics, THD and RTD. For medium-sized oil-filled transformers, there’s a need for more standardized IEEE®/IEC®-based modelling of hot spot temperature, ageing factor or degradation of life in the transformer.
However, for larger-size mid-to-high-end power transformers, distribution transformers, and critical assets, operators require all standard monitoring, plus additional elements. These include historical records, energization characteristics, transformer health reports and transformer models, as well as integrated DGA analysis.
Again, the additional functionalities available in today’s Multilin 845 can provide this more comprehensive data collection, allowing greater scalability of the monitoring and diagnostic solution.
The applications that can be built on this more holistic, integrated approach include electrical models, DGA models, energization records, integrated fault reports and health reports.
Electrical Models
In addition to continuously measuring voltages and current, protection relays such as the 845 measure numerous critical electrical parameters, including over-excitation and flux conditions.
This allows operators to see loading imbalances and averages, including seasonal averages, average loading from one particular condition to another, or average loading for parallel or unparalleled conditions. For each of these different operational scenarios, the 845 relay captures the electrical characteristics of the transformer and stores this data for a short- or long-term view. Data can be stored for up to one year of data within the relay, creating a repository of transformer behaviour and modelling it.
These models depict specific behaviours and help in correlating various electrical data sources to identify trends.
EnerVista and Perception® Software
Transformer monitoring software systems such as GE’s Perception help in the condition-based monitoring of transformers with large volumes of historical data. They are used for the long-term health assessment of transformers, fleet monitoring, risk analysis and maintenance scheduling using historical data.
GE’s Perception Fleet provides a holistic approach to transformer fleet management assessments for utility and industrial applications. Designed as a standards-based software system, the application utilizes real-time DGA data from monitors/sensors in the field to evaluate the condition of each asset and establish its risk of failure.
The software tool is then able to prioritize and rank each asset within the fleet to enable a proactive maintenance approach that is targeted and more cost-effective. This ensures the customer focuses limited resources where they are needed most, reducing operational expenses.
For short-term health assessment of transformers, a system such as EnerVista should fulfil the following:
helps with fault analysis after a major or critical event
assists with commissioning
provides time-synchronized data correlation between electrical, thermal and mechanical parameters for proactive transformer condition monitoring
performs historical events analysis
Conclusion
Today’s power engineers and asset managers need transformer monitoring and diagnostics solutions that provide clear, actionable intelligence through a combination of electrical, chemical and thermal data. In unifying these different types of data, the Multilin 845 protection relay provides a holistic view into multiple aspects of transformer health, including overloading and gassing, over-voltage and bushing problems, hotspots and DGA, and tap changer and cooling system monitoring...
