N. K. Roy

Partial discharge measurement of transformer with ICT facilities

Recent development in Information and Communication Technology (ICT) has drawn attention of scientists and engineers to develop ICT enabled laboratories. In this context development of an ICT enabled high voltage laboratory with facilities of remote operation is required because of its demand in the Engineering education as well as the assessment of insulation for continuous monitoring of the health of power equipment. The insulation of the power equipment is degraded due to the cumulative effect of the electrical, thermal, chemical and mechanical stress caused by the partial discharges (PD). Partial discharge detection and measurement constitute an important tool for quality assessment of insulation systems in high voltage (HV) power equipment. This paper reports on the development of ICT enabled remotely operated high voltage laboratory (ICTRHVL) for on-line measurement of partial discharges (PDs) of a model transformer. The remotely operated high voltage laboratory includes the partial discharge assessment facilities with ICT enabled technology will help the users to perform partial discharge tests and assessment on-line, in real time on real equipments, by sitting at their own place by local area network (LAN) as well as through the internet.

Microstrip patch antenna based UHF sensor for detection of Partial Discharge in High Voltage electrical equipments

High Voltage (HV) power apparatus are usually, the most critical and costly component in any power system. Sudden failure of such component leads to unwanted interruptions and catastrophic losses. Partial Discharges (PD) are reported as main reason for degradation of insulation system in any HV power apparatus. A successive occurrence of such discharges eventually leads to complete failure of the equipment. Therefore, it becomes important to monitor the PD in all HV power apparatus in order to detect incipient insulation problems, and to prevent further tragic failure. In the work, microstrip patch antenna has been designed in suitable manner for detection of Ultra High Frequency (UHF) signals, emitted due to occurrence of PD in HV power apparatus. An experimental study has been conducted in laboratory environment for testing of proposed sensors. Experimental results also correlated with the standard PD detection system (IEC60270). Result shows that, the proposed microstrip patch antenna can be effectively used as UHF sensor, and PD can be detected in the HV power apparatus in non-contact mode from a long distance. PD measurement with microstrip patch antenna is easy to install and also a cost effective solution for online condition monitoring of HV power apparatus.

Low cost RF sensor for partial discharge detection of high voltage apparatus

In-homogeneities, impurities, weakness within the insulating material or improper positioning of the electrode across insulator causes uneven electric field distribution into the localized area, which often creates partial discharge (PD) and are common mainly in high voltage power apparatus. After initiation of partial discharge into the localized region, it starts damaging the whole insulator with time. Thus detection of PD has become a major challenge for the researchers. This paper presents a method for design of low cost sensor for detection of PD, by detecting the radio frequency (RF) wave with the help of a patch antenna, which is simple and can be manufactured easily. A step by step approach has been described to develop the antenna for the detection of PD. Different analysis as required for the design parameter of the antenna has been simulated by ZELAND IE3D and presented in this paper. An experimental study has also been performed in the laboratory environment to validate the simulated results. The above study shows that, the indigenously made RF sensor is suitable to detect the partial discharge of a high voltage power apparatus and it is a cost effective tool in the field of online monitoring of partial discharge measurement.

Mineral oil based high permittivity CaCu3Ti4O12 (CCTO) nanofluids for power transformer application

Power transformer is the heart of the power transmission and distribution in an electrical system and its lifeblood is transformers insulating oil that acts as an insulation of the transformer. The physical and electrical properties of insulating oil mainly depend on the constituents of insulating oil and the properties of oil can be optimized by introducing nanofluid. Mineral oil based CaCu3Ti4O12 (CCTO) nanofluids with various volume percent of CCTO (0 to 0.05 vol %) have been prepared under ultrasonication. These nanofluids (before ageing) were evaluated for the critical parameters such as AC breakdown voltage (BDV), loss tangent, dielectric permittivity, resistivity, acidity, interfacial tension, flash and fire point as per the procedure outlined in the ASTM and IEC standards. The nanofluids (NF-0 to NF-3) showed improvement in the AC breakdown voltage, tan delta, flash and fire properties. The AC breakdown voltage increased as the CCTO volume percent increase in the mineral oil. The nanofluids were also subjected to accelerated ageing and the critical parameters, evaluated on the aged nanofluids (ANF-0 to ANF-3), were compared with that of fresh nanofluids. The nanofluids do not show any significant change in the viscosity, however, influences on the electrical properties were observed. The improvement in electrical properties can be attributed to the formation of insulating boundaries in nanomaterial which acts as insulation barrier that hinders the breakdown mechanism.

Intensity-Modulated Fiber Bragg Grating Sensor for Detection of Partial Discharges Inside High-Voltage Apparatus

The detection of partial discharges (PDs), inside high-voltage (HV) power apparatus, such as transformers, busing, switchgear, and so on, is important as it provides most early indication of failure. This paper presents a novel fiber Bragg grating (FBG)-based intensity-modulated fiber-optic PD sensor. The proposed sensor has been designed to be placed inside the HV equipment, and can detect high-frequency acoustic wave, as emitted due to the occurrence of PDs. For sensing, two pairs of FBGs with partial overlapping spectrum have been placed in full-bridge combination, on the opposite sides of a suitable designed elastic element of a high dielectric constant material. The proposed full-bridge combination modulates the intensity of the reflected light due to vibration of the elastic element. Thus, the proposed sensor does not require either a fiber Bragg grating analyzer or a narrowband tunable laser source, which is conventionally used in FBG-based sensors. Moreover, the proposed sensor also inherently eliminates the error due to large variation in the temperature of the HV equipment, operating at different parts of the world. The fundamental design equations and experimental results are presented in this paper. From this paper, it has been found that the proposed sensor has reasonable good dynamic responses, signal-to-noise ratio, and sensitivity.

ICT enabled high voltage laboratory: Cost effective tool for engineering education

Growing demand for use of Information and Communication Technology (ICT) in “technology for all” concept has been attracted the attention of all academician and engineers to develop an ICT enabled system for each and every field. In the field of education, ICT enabled high voltage (HV) laboratory is an effective educational tool for all of the institutes those offer Electrical and Electronic Engineering programs at undergraduate and post graduate levels. The students can access and familiarize themselves with operations of such facilities for conducting the laboratory experiments and for testing high voltage power apparatus by local area network (LAN) as well as through internet. At present more than thousand colleges provide engineering education in India. Approximately half of them offer undergraduate programs in Electrical and Electronic Engineering that include HV Engineering. It is mandatory as per the guidelines of the All India Council for Technical Education (AICTE) that the laboratory facilities are to be provided for the programs which are offered by the colleges. However, very few colleges have HV laboratory facilities due to the involvement of huge costs. A way to address this deficiency, the concept of cost effective HV virtual laboratory (HVVL) and ICT enabled remote HV laboratory (ICTRHVL) are introduced for engineering education at National Institute of Technology (NIT), Durgapur. In this paper, the HVVL and ICTRHVL modules are described where students familiarize themselves with the HV power apparatus, testing equipment as well as with testing of HV power apparatus.

Manganese doped Zinc oxide thin film hydrogen gas sensor at reduced operating temperature

During the past few decades, semiconductor metal oxide (SMO) gas sensors have become a prime technology in several domestic, commercial, and industrial gas sensing. The semiconductor properties of zinc oxide along with its dopant remain to be trapped fully in its application as gas sensor. With the advent of nanotechnology, miniaturization and high sensitivity happens to be a key issue in sensor fabrication. Most of the SMO gas sensors fabricated by nanotechnology process operate at high temperature. This paper gives a new insight to hydrogen gas sensor characteristics, by reducing the operating temperature of hydrogen (H2) sensor, fabricated from the nano particle of manganese doped zinic oxide(ZnO), synthesized by chemical precipitation method.

An unsupervised Gaussian mixer model for detection and localization of partial discharge sources using RF sensors

This paper presents an automated system for condition monitoring of power distribution utilities through detection and localization of partial discharge (PD) sources. Among the various outcomes of PDs, emission of Electromagnetic Magnetic wave mainly in the radio frequency (RF) and ultra-high-frequency (UHF) band, is an eminent phenomena. In the present work, a Gaussian Mixer Model (GMM) has been applied in an unsupervised manner, primarily for detecting presence of PD sources inside power system utilities, and thereafter for classification of PD events. Finally, time-delay-of-arrival (TDOA) based algorithm has been applied for localization of the PD sources. The proposed system has been tested in laboratory using different types of artificial PD sources and in different power distribution sub-stations. The obtained results were found to be reasonable encouraging.

Characterisation 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 (HV) power apparatus is the efficient diagnosis of partial discharge (PD). Many different methods have been proposed by researchers for detection and measurement of PDs in past, based on different outcomes of PD such as Chemical, Acoustic, Electrical, Optical and Electromagnetic (EM) wave radiation. Among these, detection of PDs by EM wave in the Ultra High Frequency (UHF) range could be an efficient method, as it is a noncontact type measurement method for PD detection. PD pulses are having life span of several nano-seconds, which can be detected by suitable wide bandwidth (BW) UHF sensor. In this work, a wide BW Microstrip patch antenna has been designed for detection of radiated EM wave in the UHF band due to PD activities in high voltage power apparatus. The proposed antenna is cost effective and having specific center frequency, capable of rejection of surrounding noise. PDs obtained from a model transformer presented here for characterizing the proposed sensor, made of Microstrip patch antenna. The characterization of the sensor has been presented by varying the PDs in the model transformer and also the distance of the sensor from PD source. The experimental result shows that the designed sensor having good sensitivity and can be used to detect PDs at a distance up to fifteen meters from the source of PDs. It is a cost effective and reliable tool for PD detection in HV power apparatus.

A New Method of Harmonic Current Extraction for Shunt Active Power Filters

Application of active power filters (APFs) towards the ever increasing problem of harmonic distortion in industrial power system, due to nonlinear loads, has become a reliable and flexible alternative. In this paper, a new method of harmonic current extraction based on charge balance principle, for shunt active power filter towards mitigation of harmonics and maintaining unity power factor both under steady state and transient operating conditions, is presented. This method involves simple mathematical calculations devoid of any iterative estimation process, so as to facilitate easy hardware implementation for industrial use. Finally simulation results for a comparative study between the proposed method and the popularly used Instantaneous PQ theory (IPQT) method is presented which reveals improved performance of the former with respect to performance, theoretical simplicity and required computation for improvement in power quality.