PD Doctor: Improving Reliability and reducing Costs of Smart Grids

Offline forms of diagnostics that require downtime or have inherently low measurement frequency are being phased out. Online forms that operate continuously during normal plant operation are coming to the fore. This allows the development of a fault condition to be captured and intervention to be taken before it fully develops into a fault condition that would mean a longer-term failure. The online monitored parts of the distribution system can include MV cable connections, but also any electrical equipment – generators, electric motors, transformers, overhead lines or the substations and contact rooms themselves.

PD Doctor Analyzer: It is a high-speed measuring unit that captures, processes and evaluates partial discharge activity. The evaluation takes advantage of the fact that on an electrical device, each partial discharge generating phenomenon has its own unique and characteristic pattern.
The measured discharge activity data together with information about the surrounding environment (temperature, humidity, pressure) is sent via a modern industrial M2M protocol.

One of the most important aspects for the successful operation of any electrical equipment is the condition of its insulation system. The equipment cannot be operated when a limit state is reached – breakdown of the insulation system (electrical short circuit). Insulation degradation is caused by various mechanisms (thermal, chemical, mechanical, poor manufacturing processes, etc.), but always involves the coincidence of partial discharges.

As the degradation of the insulation condition progresses, both their frequency and size increase. And it is by measuring them continuously and permanently online that not only the progress of the degradation itself can be monitored, but above all the need for intervention can be indicated in time and repairs can be better planned.

A modern tool in this area is the PD Doctor system. This unique and patent-protected solution based on an interdisciplinary basis combines disciplines such as power engineering, applied physics, electronic control and cybernetics.

The system provides precise and reliable diagnostics and monitoring of insulation conditions of MV lines and equipment in substations and transformer stations. It improves the reliability of power supply by online detection of power failures and instantly identifies and reports anomalies of operating conditions. The system stores online data and thus also acts as a “black box”, where the history of operating conditions can be analysed, including events just prior to a fault.

The PD Doctor system also enables the reduction of previously necessary prophylactic costs. In the case of a conventional substation, this is a saving of thousands of euros per year. It also contributes to minimizing field interventions. Online monitoring helps to protect any electrical equipment in the wide range of 230 V to 400 kV.

Predicting the technical lifetime of existing equipment is another benefit of PD Doctor. This allows the cost of installing new equipment to be significantly reduced and older equipment to be operated safely and reliably until the physical (and not just theoretical and statistical) end of life.

František Steiner, head of the Diagnostics and Testing Group at the RICE Research Centre of the University of West Bohemia in Pilsen, who together with the members of the group collaborated in the development of this system, says: “The use of new diagnostic methods clearly leads to the prevention of faults and increased reliability of power distribution systems and equipment.”

The positive effects of the deployment of the PD Doctor system on the reduction of CO2 emissions appear to be interesting and, above all, important from the point of view of the present and future needs of sustainable development with emphasis on the environment and quality of life. By online monitoring of partial discharges on electrical equipment, it is possible to locate critical areas where losses are at their maximum, replace the damaged part of the equipment or lines there, and make a significant contribution to reducing losses by at least 20 percent, which corresponds to a reduction of 6.5 t CO2 per substation per year. The PD Doctor system thus contributes to a reduction in technical losses (by early detection of corona losses), reduces the operation of metering vehicles of electricity distributors or prevents fires on electrical equipment and the associated release of CO2 and toxic gases into the air. Moreover, the PD Doctor system has been recommended by the Electrotechnical Association of the Czech Republic as a solution with high user and societal utility for online monitoring of partial discharges on HV and MV systems.