On Line Continuous Monitoring, Detection, and Location of Partial Discharge and Dynamic Aging in Medium and High Voltage Electrical Insulation

Electric utility networks typically include a large amount of generation, transmission, and distribution plants and equipment. The maintenance of those plants and equipment is crucial to avoid unnecessary and expensive treatments or replacements. In order to properly perform that maintenance, it is necessary to have credible information on the condition of those assets. The optimal utilization of those assets can be achieved by devising suitable maintenance strategies; thus, their life expectancy can be predicted, which allows timely and properly planned replacement or refurbishment. The trend of expanding maintenance periods and increasing the assets lifetime, eg. switchgear, brings with it a need for non-invasive monitoring and diagnostic techniques. These techniques help in ensuring equipment endurance, and reliability [2]. The need for improved reliability and continuous service for a particular period, and optimal economic performance of electric grids has grown in importance over recent years. In particular, the high investment and operating costs of medium and high voltage switchgears justify the need for real-time monitoring as well as effective condition assessment and diagnostics. Such practices assist in extending equipment operation and in avoiding catastrophic failures of essential elements. Statistics indicate that 85% of equipment failures at medium and high voltages are partial discharge (PD) related. This highlights the importance of focusing on this fault toward obtaining more reliable power systems. Incipient faults, which usually evolve from PDs, cause major insulation degradation and lead to permanent faults in electrical power networks. The cost of not timely equipment maintenance or sudden failure is usually very high. Consequently, the insulation materials, which are known as the backbone of any electrical system, are essential elements and increasingly used in all electric power generation, transmission, and distribution systems in medium and high voltage power networks. Power cables, switchgears, splices, transformers, motors, generators, bushings, bus ducts, capacitors, and reactors are some devices where insulation materials are used to separate conducting parts and provide isolation from earthed components. Trends for modernizing the power grids focus on improving the grid availability and maintainability; however, particular attention is given to the reliability of existing electric grids across the three key areas, namely generation, transmission, and distribution. Grid reliability depends on the quality of fault management and fault prevention, even in the presence of several perturbations, such as unbalanced supply voltages, harmonics, and measurement noises. PD, which is the main cause of aging, insulation deterioration and failure in the insulated equipment in medium and high voltage systems, considerably affects the reliability of the operating power grid [5]. According to IEC 60270, PD is “a localized growth of dielectric breakdown in an area within solid or fluid dielectric insulation system under medium or high voltage stress”. PD activity takes place at any gap in solid, liquid, or gaseous insulation system, where the strength of electric field exceeds the strength of the insulation material breakdown point. Surface discharges, voids, corona forms, or floating electrodes degrade the insulation level of power network elements. Many factors, such as environmental conditions, e.g., temperature, humidity, voltage, and load, affect PD activity [6]. The reasons for PD faults in medium and high voltage insulation are numerous including contamination on the surface of the insulating material, material irregularities, voids, flaws, air bubbles in liquid insulation, floating particles in gas insulation and mechanical failure to the insulation material. Activities due to PD gradually affect the equipment and frequently lead the system from the incipient fault condition to the complete failure; thus, sudden outages of the power network are usually the consequences [7]. It is, therefore, essential to identify the developing PD activities at early stage. The development of an effective smart fault management system specified for PD activities can play a vital role in improving the system reliability and stability. Fault management requires unremitting real-time monitoring of the electrical power network elements, collecting information about the vital parameters and data pre-processing, removing inconsistencies and noise from the measured data, analyzing the received information, and taking appropriate actions to improve grid reliability and performance. Such a system can help in avoiding destructive consequences by timely warning the plant operator on PD activities and locations so that the faulty parts can be replaced or timely conserved before a complete failure occurs. The goal of this project is to develop and implement a novel on-line fault management system capable of identifying and locating PD activities in the insulation of medium and high voltage switchgears and cables. The proposed strategy does not require hardware reconfiguration or additional sensing equipment and will only use the available signals. The proposed online prognostication algorithms will be robust, accurate, and capable of detecting the presence and locations of PD activities in addition to the severity of the fault and will predict the remaining useful lifetime of the insulation system. The proposed solution will be effective in diagnosing the characteristics of PDs under both normal and abnormal conditions. It will also have a fault tolerance feature which will allow it to evaluate the possibility of operation in the presence of specific faults.

1- Develop insulation condition assessment algorithms for MV/HV insulation and conduct
comprehensive degradation and aging tests.
2- Develop online partial discharge diagnostics algorithms as plug-in tools particularly for switchgears and test their performance while running the equipment
3- Estimate the remaining useful time of electrical equipment insulation for more reliable and economical operation.
4- Develop tracking algorithms to detect PDs, track their evolution, locate them within
electric power system, and tolerate faults toward continued operation until providing
planned maintenance.
5- Estimate the average time to insulation breakdown.
6- Improve system reliability and avoid costly damages.
7- Analyze the nature and characteristics of partial discharge activity.
8- Develop/assist the maintenance, replacement, and renewal strategy of the electrical equipment in a smart grid.
9- Online monitoring of the physical state of electrical grid equipment.
10- Create new market and technology in generation, transmission, and distribution plants for electric utilities and for many industrial and commercial locations.
11- Provide an early indication of PD activities, diagnose problems, and prevent failures.
12- New standards and guidelines for fault detection.
13- Determine whether the grid equipment is in a suitable operation condition.
14- Diagnose the status of electrical power elements during and after partial discharge occurrence.