Power Research

Tapan M. Rami ¹, Dipak Mehta ²

Affiliations
1 Manager, Essar Oil Ltd., Refi nery Site, 39 KM, Jamnagar-Okha Highway, Vadinar - 361305, Gujarat, IN
2 Manager, Electrical Dept, Essar Oil Ltd., Refi nery Site, 39 KM, Jamngar–Okha Highway, Vadinar - 361305, Gujarat, IN

Abstract

Polarization and depolarization current (PDC) technique is an effective tool to assess the condition of insulation system in high voltage motors So far the PDC behaviors of insulation have been widely investigated. This Paper presents the assessment of insulation systems for high voltage induction motor through measurement of polarization depolarization current or charging and discharging current. However, with the increasing number of Motors choosing insulation , it is important to investigate the PDC characteristics of insulation to see whether the PDC technique can also be used to assess the condition of new insulation system using PDC accurately It is considered that the insulation systems are having different types and conditions of insulation aging. It demonstrates that the insulation resistance (IR) and polarization index (PI) can’t be used individually to judge insulation dryness and the combination of insulation resistance and PI. PDC analysis is better technique of insulation quality assessment than the insulation resistance alone. The PDC analysis is non destructive dielectric testing method for determining the conductivity and moisture content of insulation materials in high voltage motors. On the basis of this analysis, it is possible to take further actions like overhauling, drying process, and replacement of the winding of the motor. This paper also presents a description of PDC analysis technique with the practically and theoretical background and some results of PDC measurements on High voltage motor duration from 0–600 days.

Keywords

Insulation system, Insulation resistance (IR), Polarization index (PI), Polarization and depolarization current (PDC), Charge storage mechanisms and Aging

Full Text

     

Dipak Mehta ¹, Hitesh R. Jariwala ²

Affiliations
1 Manager, Electrical dept, Essar Oil Ltd., Refi nery Site, 39 KM, Jamngar–Okha Highway, Vadinar-361305, Gujarat, IN
2 Associate Prof., Department of Electrical Engineering, SVNIT, Surat, Gujarat, IN

Abstract

This paper presents analysis of power transformer insulation by one fundamental insulation power factor test, also known as Tan Delta. It is a routine test conducted at site to know the healthiness of insulation in transformers. Out of 108 transformers tested for research work, case studies were chosen for analysis purpose. Experimental data shows our experience on the measurement of Tan Delta techniques of earthing systems and dryness of insulation in transformers. Result shows that the Tan Delta testing method is very effi cient method.

Full Text

     

Dipak Mehta ¹, Hitesh Jariwala ²

Affiliations
1 Electrical Dept, Essar Oil Ltd., Refi nery Site, 39 KM, Jamnagar – Okha Highway, Vadinar-361305, Gujarat, IN
2 Electrical Dept., SVNIT, Ichchhanath, Surat-395007, Gujarat, IN

Abstract

Electrical insulating oils of petroleum origin are extensively used in transformers. The physical, electrical and chemical properties of such oils are subject to change due to environment and electrical stresses. For use in any electrical apparatus the oil has to comply with certain requirements and determination of these properties before fi lling the apparatus is of utmost importance. It is also equally important to monitor the condition of oil in service. Condition Monitoring of Insulating oil of power transformer is performed by oil contamination and dissolved gas analysis. In Oil contamination test comprise of breakdown voltage, water content, neutralization value, sediment & sludge, resistivity, dielectric dissipation factor, interfacial tension and fl ash point. DGA analysis is obtained by IEC ratio method, Rogers ratio method, Key gas method and Dual triangle method to distinguish the possible fault types by analyzing the amount of gases dissolved in the insulating oil. Total 108 no’s transformer tested for oil contamination test and dissolved gas analysis. Out of them 3 no’s case study chosen for analyzing Insulating oil condition. Also other 2 no’s case study is chosen from Different industries for analysis purpose.

Keywords

DGA analysis,IEC ratio method, Rogers ratio method, Key gas method and Dual triangle method.

Full Text