S. Karmakar, N. K. Roy, Andrew Nafalski , Pathik KumbhakarIn electrical power engineering education, it is advisable for students to be acquainted in laboratory courses with practical high voltage engineering knowledge. Because of high cost for setting up a high voltage laboratory, the laboratory is a potential cost effective educational tool for all the institutions that offer such programs at undergraduate or postgraduate levels. The laboratory provides an opportunity to share the teaching resources in terms of personnel and facilities. It has the opportunity to support all the learning objectives of the traditional high voltage laboratory in a remote setup. This work reports on the development of an ICT-enabled remotely operated high voltage laboratory at the National Institute of Technology, Durgapur, India, for online control of generation, measurement and analysis of steady state and transient high voltage phenomena. In the field of education, the laboratory is a potential tool for all institutions that offer electrical power engineering programs at undergraduate and postgraduate levels. The students can access and familiarize themselves with operations of the laboratory for conducting experiments and for testing high voltage power apparatus by using a local area network (LAN) as well as through the Internet. This work explains the approaches developed at the laboratory for experimentation in remote impulse voltage testing and online report generation. The laboratory can also be used for commercial high voltage tests for industries and utilities.
S. Karmakar, N. K. Roy, Pathik KumbhakarIn power systems, varieties of insulation materials are used to protect the high voltage power apparatus such as transformer, switchgear, current transformer, potential transformer etc. One of the most common liquid insulating materials used as a dielectric medium in transformers is the transformer oil. The transformer oil is degraded due to the combination of the ageing processes such as partial discharge (PDs), electrical arcing, and thermal ageing while it is under operation during its long period of service. In this work, the effects of different ageing processes on the optical absorption properties of insulating oil of a model transformer is studied using a UV-visible spectrophotometer diagnostic method which is presently becoming a popular method to identify the ageing of the insulating oil of high voltage transformers. It is found that the aged transformer oils exhibit optical absorption in 200– 400 nm wavelength regions. The optical quality of the transformer oil is mostly degraded due to PDs, and sharp and prominent absorption peaks appear at 293 nm,306 nm, and 324 nm wavelengths, for sample which is aged due to PDs. For other aged samples, the peak at 306 nm is absent and the optical absorption characteristics are almost similar to that of the new transformer oil.
Anjali Chatterjee, N.K. RoyThe Non-Destructive Evaluation of Power transformer by monitoring various parameters, to predict its in-service behavior, is very much necessary for operating engineer to avoid catastrophic failures and costly outages. Dissolved Gas Analysis (DGA) is an important tool for transformer fault diagnosis. It is observed that the result of DGA doesn’t have a perceivable change over a short period. For less population of data availability grey modeling is used. To apply probability theory, statistics, and fuzzy systems, there is a requirement for a large number of data, then only conclusion or some inference can be drawn. The advantage of using the grey system theory is that, it gives a fair accuracy in predicting the volume of the gases, expected to be generated after some time period, using a small sample of data. In this paper we have done a comparative study on the predicted results obtained by different model of Grey theory mainly whitened model, connotation model and modified grey model. It is found that the error generated from the prediction by all the three model are within the limit of 15% which is acceptable. Additional by linear regression we are establishing a correlation between the key gases. This helps us to detect the abnormality of the situation and diagnose the type of fault. Additional this work deals with the study on the behavior of the gas dissolved in the oil which has undergone filtration and the one without filtration. Through graphical means it has been clearly shown that filtration at periodic interval will extend the life of the transformer. It has been shown that the rate of gas generation also plays an important role to detect an active fault.
B. Sarkar, C. Koley, N.K. Roy, P. KumbhakarHigh voltage (HV) power apparatus determines the stability of any electrical power system. Failure of such apparatus is mainly due to damage of insulation normally caused by the Partial Discharge (PD). Therefore PD measurements are globally considered as most essential and favored testing procedure for most of the HV power apparatus. Online condition monitoring may help to take proper corrective action at proper time, which reduces unscheduled down time and can save money for electrical supply utilities. HV power transformers are being considered as heart of any electrical system and they have received much attention in recent years. In HV transformers, PD is one of the main reasons for degradation of insulation quality. Therefore its detection can provide early indication of the insulation failures of transformers. PD can be traced through direct measurement of current, electromagnetic radiation, chemical changes or acoustic emission. Electrical, acoustic, chemical and optical methods of PD measurement are the popularly accepted methods of PD detection in the high voltage (HV) power transformers.
The schematic diagram of combined electrical and optical PD measuring system
D. K. Mishra, C. Koley, N. K. RoyCharacterisation of Microstrip patch antenna based UHF sensor for detection of Partial Discharge; Major Prerequisite to overcome the problem due to the insulation breakdown in High Voltage power apparatus is the efficient diagnosis of partial discharge (PD). Many different methods have been proposed by researchers for detection and measurement of PD in past which are based on different outcomes of PD such as Chemical, Acoustic, Electrical, Optical and Electromagnetic (EM) wave radiation. Among these the detection of electromagnetic waves in the Ultra High Frequency (UHF) range could be an efficient method as noncontact type measurement of PD from a longer distance is possible. PD pulses are having life span of several nano-seconds, which can be detected by suitable designed wide bandwidth (BW) UHF sensor.
Schematic diagram of inset feed Microstrip patch antenna ; Schematic diagram of PD detection system with fabricated UHF sensor
R.T.Arun Ram Prasath, S.N.Mahato, N.K.Roy, P.Thomas
( A joint venture with CPRI, Banglore)
Prepared samples of Pure and Aged Mineral oil Based Nanofluids