Informatics Publishing Limited

Muhammed Faisal Rahman ¹, B. Nageshwar Rao ², Pradeep M. Nirgude ³

Affiliations
1 Senior Research Fellow, Cables and Diagnostics Division, Central Power Research Institute, Bangalore, IN
2 Additional Director, Cables and Diagnostics Division, Central Power Research Institute, Bangalore, IN
3 Joint Director, Ultra High Voltage Research Laboratory, Central Power Research Institute, Hyderabad, IN

Abstract

Corona discharge is one of the significant problem associated with power transformer and can occur due to sharp points or free conductive particles. The existence of sharp points at joints or terminals or conducting parts is very difficult to avoid completely during the manufacturing process of the transformer. The free conductive particles can arise from manufacturing process or can be developed during service period of the transformer. These free conductive particles can adhere to paper or pressboard insulation barrier or freely move in the bulk oil. In transformers highly non uniform fields are often present due to sharp points and free conducting particles, so detecting their effect on the transformer is very critical for the life of transformer. In the present investigation, to generate a high voltage corona in air or oil, a test chamber of dimension 50cm x 50cm x 50cm made from Perspex material and fitted with removable needle plane electrode arrangement has been used. The discharge measurements are carried out using Partial Discharge (PD) measurement technique according to IEC 60270. The results obtained are presented and discussed. Discharge pulse characteristics such as magnitude, rise time and decay time of different needle plane barrier configurations are analyzed. This paper also discussing pattern analysis and dominant frequency of discharges due to different needle plane barrier configurations.

Keywords

Corona in air, oil, pressboard barrier, partial discharge, pulse characteristics, pattern analysis.

Full Text

     

M. Prameela ¹, Radhakrishna G. Murthy ¹, Pradeep M. Nirgude ²

Affiliations
1 Vignan University, Guntur, Andhra Pradesh, IN
2 Central Power Research Institute, UHV Research Laboratory, Hyderabad, IN

Abstract

Sweep Frequency Response Analysis (SFRA) method is an effi cient method for predicting the geometric changes, and research on the optimum and unambiguous application is still in progress. In order to correlate integrity of transformer windings with changes in the frequency responses, a lot of measurements have to be performed and analyzed. The present work discusses special experimental investigations carried out on model transformer winding to study the various aspects of axial and radial winding displacements using SFRA test. The experimental results for axial and radial winding displacements are presented and analyzed. The analysis will help in understanding the health of an actual transformer and diagnosing it for any impending fault with respect to winding movements.

Keywords

Sweep frequency response analysis (SFRA), Transformer windings, winding displacements, Clamping pressure, Distribution transformer

Full Text

     

M. Prameela ¹, G. Radhakrishna Murthy ¹, Pradeep M. Nirgude ²

Affiliations
1 Vignan University, Guntur, Andhra Pradesh, IN
2 Central Power Research Institute, UHV Research Laboratory, Hyderabad, Andhra Pradesh, IN

Abstract

Frequency Response Analysis (FRA) is an emerging diagnostic tool to assess the mechanical integrity of the transformer. Proper guidelines on using FRA data for declaring the integrity of transformer windings or indicating the extent of displacement/deformations are not yet available. Interpretations of the Sweep Frequency Response Analysis (SFRA) data for diagnosing the condition of the transformer windings are not yet clear. Experimental investigations were carried out on a model transformer to obtain SFRA data for various simulated conditions like axial and radial displacements, winding displacements and deformation, core faults, etc. for different test configurations. The paper presents the results of these investigations and analyze them to form the guidelines in interpreting the SFRA data for various test conditions to detect various types of faults. It is observed from the analysis of results that SFRA with different test confi gurations needs to be applied to detect the type of fault and faulty phase winding. The information presented in the paper, from the simulated faults on transformers with SFRA measurements, will be useful in the interpretation of FRA results to assess and diagnose the condition of transformer windings and core.

Full Text

     

Pradeep M. Nirgude ¹, B. Gunasekaran ¹, R. S. Shivakumara Aradhya ¹

Affiliations
1 Central Power Research Institute, IN

Abstract

This paper presents the results of the study conducted on 400 kV, 800 kV and 1200 kV transmission line insulator strings and conductor–tower window geometries with an aim to optimize air insulation clearances. Laboratory investigations were carried out to evolve the switching impulse performance of phase–to–earth and conductor–window confi gurations in addition to the reference rod plane air gap lengths in EHV/UHV range. Tests were conducted on 400 kV, 800 kV and 1200 kV line confi gurations of I, Vee, double Vee, etc., by simulating the tower windows. The paper also presents results of the study on optimization of conductor-tower air insulation clearances for adoption in 1200 kV AC transmission lines using 8 bersimis conductor bundle carried out for establishment of 1200 kV Test Station at BINA, Madhya Pradesh, by Power Grid Corporation of India. Results of the tests and the data presented in the paper will be useful for design of phase-to-ground air insulation for adoption in EHV/UHV Transmission lines.

Full Text