Power Research

K. P. Meena ¹, R. Arunjothi ¹, Thirumurthy ¹, G. K. Raja ¹, B. Nageshwar Rao ¹

Affiliations
1 Diagnostic, Cables and Capacitors Division, Central Power Research Institute, Bangalore-560 080, IN

Abstract

Flexible PVC Cables form the major part of Power distribution system within residential buildings, industrial buildings, and other commercial institutions. The ampacity of power cable depends upon the cross sectional area of conductor and the laying and installation of the cable in service. Generally two or more number of PVC cables are bundled together and inserted as a bundle in a conduit pipe for connecting to various load points. As the bundling of cables produce more heat than a single PVC Cable, and dissipation of heat is poor, the ampacity of these cables reduces considerably. Hence the exact selection of sizes and no. of cables are essential to avoid overheating of those cables and the resulting fire havocs.

PVC House wiring cables consists of copper conductor extruded with PVC insulation and are installed generally through a conduit pipe in a bundled manner. The steady state current rating of these cables depends on the way the heat generated in the cable due to current and the heat transmitted to the cable surface & then dissipated to the surroundings. The maximum conductor temperature is limited by the type of insulating material used. In this paper theoretical and experimental results of steady state ampacity ratings of bundles of house wiring PVC Cables laid in conduit pipes are compared.

Keywords

Ampacity, house wiring cables

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B. Nageshwar Rao ¹, K. P. Meena ¹, Thirumurthy ¹, G. K. Raja ¹

Affiliations
1 Central Power Research Institute, Bangalore-560080, IN

Abstract

Over the years both due to demand and technological advancements there has been a continuous transition from smaller operating voltages of 6.6. kV to higher voltages of 500 kV. The conventional technology like taping or fi eld moulding are in vogue and new technology like pre-moulded slip on cable accessories are gaining importance for jointing of polymeric high voltage cables up to voltages of 500 kV. The fl ammability characteristics of polymeric materials used in cable insulation and jacketing have been of great importance over the years. Evaluation techniques have become more stringent and both short term and long term tests are conducted in order to ensure the quality of materials used, the manufacturing processes, workmanship and reliability. In this paper the recent advances in HV and EHV power technology is summarized and the experiences in testing and evaluation of 220 kV cables is presented and discussed.

Keywords

Taping, Pre-moulded slip, High voltage (HV), Extra high voltage (EHV) polymeric cables.

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R. Arunjothi ¹, Thirumurthy ¹, P. V. Satheesh Kumar ¹, G. K. Raja ¹, K. P. Meena ¹

Affiliations
1 Central Power Research Institute (CPRI), Bengaluru – 560080, Karnataka, IN

Abstract

In this paper the fire and smoke properties of special application cables such as instrumentation cables, control cables, fibre optic cables and flat travelling cables are compared for their better fire performance. The various outer sheath materials of these cables have been evaluated for its fire performance and as well as smoke performance. In case of zero halogen outer sheath materials of special application cables, only the smoke property is given importance and the fire retardant properties are not being given much importance. Hence the significance of fire retardant property is highlighted in this study.

Keywords

Flammability, Halogen, Instrumentation Cable, Smoke Release, LSZH

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Dillip Kumar Puhan ¹, Rajat Sharma ¹, K. P. Meena ¹, B. Nageshwar Rao ¹

Affiliations
1 Central Power Research Institute (CPRI), Bengaluru – 560080, Karnataka, IN

Abstract

Power transformers are key components in the substation/switchyard and failure of transformer can have an enormous impact on reliability and availability of power supply and has financial implications. As there is ever increase in demand of power, the reliability of power equipment assumes high importance. 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 power transformers by operating at their design capability. This can be achieved by periodic diagnostic testing and adopting condition based maintenance practices. In this paper various condition assessment techniques for oil filled transformers are discussed and few case studies are presented.

Keywords

Condition Assessment, Generator Transformer, Insulation Diagnosis, SFRA

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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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Moumita Naskar ¹, H. M. Dharmendra ¹, K. P. Meena ¹

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

Abstract

A rapid test method based on a logarithmic degradation model for the lifetime assessment of ethylene-vinyl acetate (EVA) used as encapsulants in Photovoltaic (PV) module is proposed. In general, encapsulants are used in widely varied conditions. However, factors such as voltage stress, irradiation, mechanical shock and vibration, environmental conditioning and chemical contamination should be evaluated. In the present study evaluation is carried on the dumbbell specimens of encapsulating material itself and is based on the percentage of reduction in the property i.e elongation percentage, which is a destructive test. Dumb-bell specimens as per ISO 37:2011(E) standard are employed. Adequate number of test specimens were subjected to thermal aging at three different temperatures 35 °C, 45 °C and 55 °C. The conditioned specimens after removing from oven were stored in decicator prior to testing i.e. while the specimens were attaining room temperature. The constant factors of the life time line a and b were calculated, and finally, the lifetime values were estimated.

Keywords

: Elongation Percentage, Ethylene-Vinyl Acetate (EVA), Lifetime Estimation, Photovoltaic Solar Cell

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R. Arunjothi ¹, Thirumurthy ¹, K. P. Meena ¹

Affiliations
1 Central Power Research Institute, Bangalore - 560080, Karnataka, IN

Abstract

Fire Resistant cables are designed to maintain the circuit integrity of the cable even during fire conditions. In general, the fire-resistant cables are made up of flame retardant zero halogen materials, so that the fire hazard such as flame propagation and smoke release of these cables are controlled. However, one more fire hazard of these fire-resistant cables is nothing but the heat released from these cables during a fire. Heat release of these cables depends upon the fuel loading of the cables and the energy available in the materials of these Fire Resistant or Fire Survival (FS) cables. In this paper, the heat release of FS cables is measured for various construction of the FS cables.

Keywords

Fire Resistant Cables, Glass-Mica Insulation, Heat Release, Silicone Insulation.

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

Affiliations
1 Central Power Research Institute, Bengaluru - 560080, Karnataka, IN

Abstract

Power Cable System is a vital asset in Electrical Power System. Now a days power cables are used in transmission and distribution of electric power at MV, HV and EHV levels. Reliability and availability of power supply depends greatly on insulation condition of the power cable system. Therefore, power cable asset management is vital for taking decision on future course of action to minimize capital expenditure, maximize reliability and avoid forced outages. In this paper, how to deploy power cable asset management is discussed using Health Index based on diagnostic test data.

Keywords

: Asset Management, Condition Assessment, Diagnostic Testing, Health Index

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K. P. Meena ¹, Thirumurthy ¹, G. K. Raja ¹, R. Arunjothi ¹, P. V. Satheeshkumar ¹

Affiliations
1 Central Power Research Institute, Bengaluru – 560080, Karnataka, IN

Abstract

With the development of XLPE cables and associated accessories up to 500 kV voltage level, XLPE Cable Systems are becoming the main back bone of the Power Distribution and Transmission system. The basic requirement of power cable is that it shall withstand the electrical, thermal, mechanical and environmental stresses imposed on it during its expected life of 25 to 35 years. Generally the development of cable for EHV applications is achieved through increased stress design, which demands very stringent quality requirements during production of cables and development of accessories. Since different designs are available for cables and accessories, it is essential to carry out long duration test to establish their compatibility and reliability. IEC 62067 for extra High voltage Cable accessories have incorporated the pre-qualification tests to check the long term reliability of the cable system in service before installation. This paper highlights the details of Pre qualification test on 220 KV Cable system conducted at CPRI for the first time in India.

Keywords

EHV XLPE Cable, Electrical Stresses, Mechanical Stresses, Pre Qualification Test, Thermal Stresses

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Moumita Naskar ¹, K. P. Meena ¹

Affiliations
1 Cable and Diagnostics Division, Central Power Research Institute, Bangalore, IN

Abstract

Components of Medium Voltage (MV) cable network are very much vulnerable under operational stresses and ageing. Heat Shrinkable Anti-Tracking Tube (HSATT), an integral part of the Joints and terminations of the MV cable network system is used to cover and safeguard the power cable joints. In cable system joint and termination are the weakest but the critical part and fail easily under stress. The most threatening source of HSATT failure is electrical tracking. Electrical tracking develops when a conducting path across the HSATT formed under electric stress due to surface discharge. Arcs created from this surface discharge phenomenon burn the HSATT and create carbonized tracks in the long run. This paper reports the electrical tracking performance of three commercially available HSATT samples. Crosslinked polyethylene (XLPE) is the key ingredient for heat shrinkable materials. Electrical tracking using the inclined-plane tracking (IPT) method develops from surface discharge activity followed by erosion under wet and contaminated conditions. So, the material under IPT test faced electrical, environmental and thermal stresses. Among these three HSATT samples two samples failed to withstand these three dimensional stress factors. Dielectric breakdown strength and volume resistance tests were carried out to cross examine the IPT results and the results are identical. The morphology has been studied to understand the failure mechanism of HSATT samples. A morphological model is presented to scrutinize the IPT test failure mechanism and the rate of erosion propagation in the HSATT samples.

Keywords

Dielectric Breakdown, Heat Shrinkable Anti-Tracking Tube, Inclined-Plane Tracking Strength, Morphology.

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