Online DGA Technology-Increasing Grid Reliability
In my earlier blog "Grid Should Not Die", I had discussed about two new technologies (Advanced Distribution Management System and WAMPAC- wide area monitoring, protection and control) that are expected to play key role in creating a "self-healing" grid.
In this blog, I will discuss on 'Online DGA technology' that will also play a key role in increasing reliability of Grids. Though there are other technologies available for improving the reliability, in this blog I will focus on 'Online DGA technology' its benefits.
For years DGA (Dissolved Gas Analysis) technology has been extensively used by utility engineers to determine the condition of Power Transformers in Grids. The oil samples collected from transformers were sent to laboratory for details analysis of all the critical gases, dissolved in transformer oil. Based on the outcome of DGA and comparison with historical values, the condition of the transformer was assessed by experts for further course of actions.
This approach has many practical issues-
1. The DGA of transformer oil is generally scheduled as part of the 'periodic maintenance'. This approach does not prevent outages that could occur in between the scheduled inspections and also result in unnecessary inspection costs if the transformer was in good operating condition
2. Certain kind of faults, like partial discharge, arcing etc. can develop suddenly inside transformer oil, when the transformer is in service, ultimately leading to transformer failure. Such failures cannot be prevented with the traditional "periodic maintenance" processes.
3. Periodic inspections are also not cost effective as these are typically scheduled periodically and not based on the condition of the equipment.
Today, "Online gas analyzers" are available, which provides real time values and ratios of key gases required to be monitored to get a picture of transformer health, when the transformer is in service. These values can be integrated in a centralized monitoring and diagnostics system for 'online condition monitoring' of transformer. This real time monitoring of transformer health, can reduce 'transformer failure rate' significantly and thereby reducing the outages due to same. This Online DGA not only benefits the customers by reducing outages due to transformer failure, but also helps utilities save money by avoiding unnecessary inspections. This also increases the life of a transformer by early detection of issues prior to failure. This online DGA is a part of a modern "Online Condition Based Monitoring" technology, which is becoming popular, slowly but surely.
While these monitoring & diagnostics systems come at a cost, they may still provide a good ROI particularly for large power transformers. At the end of the day, we need to remember that, 'transformer' is the costliest equipment in a T&D utility and the lead time to repair a transformer is significantly high compared to other equipments used in utility.