Power Research

K. Mallikarjunappa ¹, Chandrashekar D. Keri ¹, V. Vaidyanathan ¹, T. R. Afzal Ahmed ¹, Dillip Kumar Puhan ¹

Affiliations
1 Diagnostics cable & capocitres division, Central Power Research Institute, Bangalore - 560 080, IN

Abstract

In this era of reformation, liberalization and unbundling of electricity markets, asset management in power sector has assumed greater prominence. Power transformers are key components in any transmission & distribution network and loss of a transformer can have an enormous impact on reliability and availability of power supply and on cost. As society is more and more dependent on electricity for development, the utilities are under pressure to meet the ever-growing demands for reliable power supply. Economic factors are the main consideration and in order to minimize capital expenditure on new equipment, it is a common policy among utilities to maximize the use of existing networks by operating at their design capability. This can be achieved by according importance to the maintenance practice. A survey of the literature indicates that there are more failures of transformer due to poor maintenance, improper operation, severe weather conditions and manufacturing and design defects than due to insulation ageing. The utilities shall have a systematic O & M practice that include diagnostic tests for condition assessment and health checkup of the equipment. The objective of the condition monitoring tests is to detect the first symptoms of incipient faults, ageing development or other problems and monitor their evolution to enable the operator to take appropriate action to avoid major failure. The paper reviews the results of various diagnostic tests including dielectric response methods for condition assessment of power transformers.

Keywords

Transformer, Diagnostic, Frequency, Moisture, Polarisation Spectrum, Dielectric spectroscopy, Partial discharge

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Dillip Kumar Puhan ¹, Rajat Sharma ¹, Thirumurthy ¹, K. P. Meena ¹

Affiliations
1 Cables and Diagnostics Division, Central Power Research Institute, Bangalore – 560080, Karnataka, IN

Abstract

A huge capital investment goes for power cables in an electric power system. Reliability and life expectancy of serviceaged power cables can be assured by systematic field testing and condition assessment program. Very Low Frequency (VLF) ac Testing proved effective for field testing and condition assessment of shielded Power Cable System. Central Power Research Institute (CPRI), Bengaluru, a premier institute for Indian Power Sector has been conducting diagnostic testing on medium voltage power cable systems to assess the healthiness of the power cable systems and cable system components. In this paper application of VLF testing for withstand and other diagnostic tests and measurements are discussed. Few case studies based on the data obtained from the field testing on MV Power Cable System are presented.

Keywords

Very Low Frequency (VLF), VLF Dielectric Spectroscopy (VLF-DS), VLF Differential Tangent Delta (VLF-DTD), VLF Monitored Withstand Test (VLF-MW), VLF Partial Discharge (VLF-PD),VLF Tangent Delta (VLF-TD), VLF Tangent Delta Temporal Stability (VLF-TDTS).

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