The electrical systems are one of the most important assets of any plant and they have a great impact on the end product. Furthermore, their management and production costs are quite high and any failure leads to massive losses for the business. These days, most assets managers face serious challenge of exploiting their old electrical infrastructure without the competent technical resources from the company, decreased maintenance budgets and sterner worker safety regulatory requirements. However, asset managers now have a new approach of improving performance and reliability of their critical electrical infrastructure through the advancing technology, particularly through Partial Discharge Testing.
Definition of the partial discharges or PD
A partial discharge is basically an electrical discharge that normally occurs in the insulation mechanism of high and medium voltage electrical installations. It is usually caused by imperfections and discontinuities in the insulation system. These discharges usually erode the insulation and will eventually lead to failure.
Where does PD occur?
PD occurs at different points of the insulation system for instance, spaces in the insulation medium, gas bubbles in the liquid insulation or interfaces between the insulation layers. PD activity may also be witnessed in high‑voltage equipment whose insulation has declined with age or has been hastily aged by electrical or thermal over-stressing or improper installation.
How does PD develop?
Once in progress, partial discharge develops into electrical surface tracking and trees. This eventually leads to breakdowns between earth and phase or between the different parts of a 3-phase system. A failure can usually occur in a few hours to even several years. This mainly depends on the imperfection type, discontinuity and its location in the system. Some discharges can be quite detrimental to the insulation system for instance discharges within cable accessories and polymeric cables. However, other discharges are benign. This is why, the main significance of partial discharge measurement and diagnostic testing is mainly geared at differentiating the various types of PD that occur.
Benefits of Partial Discharge Testing and Monitoring
The data that you will get from the partial discharge monitoring can offer critical information defining the quality as well as the reliability of the insulation and how it impacts the overall health of the equipment. Since the activity of partial discharge is available even before any insulation failures, it is possible for the asset managers and other responsible parties to accurately monitor this so that they can make more informed decisions regarding the replacement or repairs of the electrical assets.
Partial discharge analysis also helps organizations to prioritize their MRO and capital investments before any unexpected outage can occur. PD testing results will also assist in predicting future reliability and performance of critical electrical infrastructure such as splices, terminations and cables, bushings and power transformers, switchgear, generators and motors.
Failures are not always limited to equipment aged by service. Testing in newly installed machinery will also build reliability from the start. Testing will help verify the original manufacturers testing data and identify any damages insulation caused by poor design, poor workmanship and improper installation during and after installation. It will also detect premature failures to ensure maximum returns on the investment.
Partial discharge testing plays a vital role in guaranteeing maximum uptime of electrical assets. it also offers asset managers critical data that enables them to target maintenance to parts that need most attention. With this kind of analysis, companies can improve their worker safety and operational efficiency.