Electrical

Generation of High DC Voltages Application of HVDC : Testing of cables : HVDC is used for testing HVAC cables of long lengths as these have very large capacitance and would require very large values of currents if tested on alternating voltages. In industries it is being used for. Electro-static precipitation of ashing in thermal … Read more

Ageing and Breakdown Due to Accumulative of Charges on Insulation Surface During discharges of solid or liquid or solid gas or solid-vacuum interfaces certain quantity and charge (electron) gets deposited on the solid insulator surface. Charge deposited can stay there for long durations (days and weeks) and presence of two charges increases the surface of … Read more

Solid Dielectric Used in Practice These dielectric materials are discussed in brief. 1. Organic materials Paper The dielectric constant is between 3.3 to 3.5. It is generally used for insulation purpose. The paper absorbs water, moisture rapidly i.e. it is hygroscopic, hence it is impregnated with mineral oil. The dielectric breakdown strength of paper is … Read more

Difference between Internal and External Partial Discharge Sr. No. Internal Partial Discharge External Partial Discharge 1. This occurs mainly due to presence of voids or occlusions. This occurs mainly due to atmospheric conditions, the outer surrounding air gets ionized. 2. This is not visible to naked eye. This is easily visible in the form of … Read more

Partial Discharge in Solid Insulation The partial discharge (PD) is originated in voids/cavities, cracks or inclusions within a solid dielectric. Since the discharge is for only limited portion/area, it is known as partial discharge (PD). Causes of voids/cavities In case of epoxy material, gas-filles voids are caused due to air leaking into mould during curing … Read more

Breakdown Due to Treeing and Tracking Tracking is the formation of a permanent conducting path across the surface of an insulation. The spreading of spark channels during tracking in the form of the branches of tree is called treeing. The conducting film is usually moisture from the atmosphere absorbed by some form of contamination such … Read more

Discharge And Breakdown Due to Internal Discharge And Errosion Breakdown In practice it is difficult to produce a continuous homogeneous solid dielectric block. Usually voids or cavities are present in a solid dielectric or at the boundaries between dielectric and electrodes. They are of various shapes and sizes and volumes. These voide contain gas or … Read more

Thermal Breakdown No solid is perfect electrical insulator, hence under an electric field small conduction currents always flow in a solid. This flow of current causes local area’s and heating created by the collision of electrons with the lattice by I2R losses. Under A. C. voltage by the energy absorbed by the solid in an … Read more

Electrochemical Chemical Breakdown These are much related to ‘thermal’ breakdown. Temperature rise in an insulating material (due to losses etc.) accelerates the chemical deterioration. Electrochemical deterioration is due to the presence and mobility of ions is the insulation which are responsible for leakage current and energy loss in the material. In the presence of air … Read more

Electromechanical Breakdown When a dielectric material is subjected to an electric field electrostatic compressive stresses are developed, charges of opposite nature are induced on the two opposite surfaces of the material and hence a force of attraction is developed and the specimen is subjected to electrostatic compressive forces and when forces exceed the mechanical withstand … Read more