Nikola Tesla Institute
Đorđe Jovanović
Hydrogenerator maintenance – Case studies from practice / Permanent Monitoring of Partial Discharges: Experiences In Complex Generator Diagnostics
ABSTRACT: Hydrogenerator maintenance – Case studies from practice
This presentration is dealing with preventive electrical testing for condition assessment of rotating machines (turbo- and hydro-generators, HV motors) which are regular practice of Specialized Laboratory for Insulation System Testing as a part of Laboratory for Testing and Calibration in Electrical Engineering Instutute Nikola Tesla, acredited according to ISO/IEC17025. These are off line elekctrical testing performed on generators and motors at standstil during yearly overhaul period according to valid relevant IEC/SRPS standards and technical recommendation of Electrical Power Company of Serbia (EPS). Rotating machines in electrical power system of Serbia are in prectice of regular preventive testing since 70s of 20th Century. These electrical test are performed on rotating machines, turbo- and hydro-generator and HV motors instald in EPS in regular intervals – Time Based Condition Assessment (TBCA) with the aim of assessing and monitoring the service condition and timely detection of possible defects that could cause breakdowns and outages during operation. Since year 2008 special test data base is established in IEE Nikola Tesla. Since 2008, ETI Nikola Tesla has created a special database in which all the results of off-line field tests are stored as well as results of all older test report whice was entered manualy. In this way, all data was systematized and the basis was created for the improvement and introduction of tools for monitoring trends and evaluating individual operating parameters of the stator or rotor electrical insulation system (EIS) and windings of rotating machines, which is neccessery for transition to Condition Based Maintenance. Several characteristic case studies from the practice of off-line testing hydrogen generators will also be given.
Keywords: Condition Based Maintenance
ABSTRACT: Permanent Monitoring of Partial Discharges: Experiences In Complex Generator Diagnostics
Permanent monitoring of generators during operation is essential for effective facility management and energy production control. The most commonly monitored variables include temperature and vibrations of various generator components. Partial discharge (PD) monitoring is particularly important for assessing the condition of the generator stator’s insulation system. Various stress and aging factors contribute to increased PD activity over the generator’s operational lifespan. If left unchecked, PDs can lead to insulation defects and potential failures. However, they also provide valuable insights into the condition of the insulation system and, indirectly, the overall state of the generator. The advantages of implementing a PD monitoring system are numerous. Firstly, it ensures high-quality data collection, including a large volume of PD data under different operating conditions, synchronized online data from multiple sources, and multi-channel data acquisition. This allows for trend analysis and correlation identification, facilitating the early detection of potential issues due to data coherence. One key benefit of PD monitoring is the automatic alarm notification system, which alerts operators when PD activity reaches or exceeds predefined thresholds. Additionally, remote access allows for configuration adjustments, real-time data review, and trend analysis. The system also enables comprehensive data collection for post-event analysis. By analyzing PD data alongside complex diagnostics results, the risk of failure can be assessed, and maintenance strategies can be optimized. This paper presents practical experiences in diagnosing the condition of generator stator insulation systems, with a significant focus on PD monitoring. The study examines correlations between PD activity and other variables such as vibration, temperature, active and reactive power, among others. Identifiable or confirmable generator conditions include loose coil rods, poor coil head connections, accelerated insulation aging (due to overheating), contamination of insulation surfaces, and other dielectric disturbances.
Keywords: partial discharges, correlations, diagnostics, generator
Biography of the presenter
Đorđe Е. Jovanović born 1966 in Belgrade, where he finished his primary and electro technical high school „Nikola Tesla“. In year 1995 graduated on the Faculty of Electrical Engineering, University of Belgrade, Electrical Power Systems division. Since 1996 has been employed in the Laboratory for Insulation System testing, Department for Electrical Measurement, Electrical Engineering Institute Nikola Tesla. Almost 30 years of experinece in research of liquid and solid dielectric behaviour, preventive controle field testing of electrical power objects – rotating machines, power transformers, HV instrument transformers. Currently chairman of CIGRÉ Serbia SC A2 – Power Transformers and member of SC A1 – Rotating machines. As author and co-author participated in the preparation of dozens of technical papers presented at domestic and foreign professional conferences.
