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  Stress and Strength Insulating materials used in electrical equipment have dielectric strength. It is subjected to dielectric stress during its service in electric circuit. Material is safe and perform as insulation till dielectric stress (alias electro static field or potential gradient) is lower than its strength during service. But may breakdown when service stress imposed is more than material strength. Afterward it cannot perform as insulator and discarded. Materials used in structure have tensile, compressive and shearing strength. It is subject to one or more of stresses due to load in different working conditions. Component is safe and continue as active member of structure till stresses are lower than respective strength. But it may break, crimp or rupture when working stress exceeds the respective strength. Such failed component is no more useful in structure. All persons have physical strength. They are subject to external physical stress under different situatio...

 

 

 

  Flexible HVDC National Power Grid: Our country is wide spread over North to South and East to West. So daytime in eastern side area is about 2 hours ahead of western side area. Power requirement varies according to local day night period. This time diversity of demand is favorable to manage local peak and off peak demands. Similarly climatic variations particularly in temperature from northern to southern area is favorable to manage local seasonal demand. Higher heating load is in winter but no cooling load in summer in northern area but contrary in southern area having no heating load in winter but higher cooling load in summer. Maximum hydro power is available during monsoon from runoff river projects whereas is available at fag end of monsoon whilst dam is overflowing in case of irrigation liked projects but is available at onset of summer in northern area due to melting of ice. Thermal generation is hampered during monsoon due to lumpy coal/lignite feeding. Thermal generatio...

  Black Start Procedure  Introduction: Modern power system is operated in grid mode. Various interconnected power systems operating in synchronous. Grid mode operation is stable due to large system bias and high inertia. Also seasonal and daily diversity in load and generation pattern is favorable for optimum utilization of resources and cost of power. However operational coordination is a task. Indian grid is monitor and control by SLDC, RLDC and NLDC at appropriate levels. Grid system operating within limit of angular stability, voltage stability and frequency is secure. Operation near or beyond the limit is highly risky. System downfall starts with generator cascading or network cascading and ends in total collapse having total power failure in large area. Electricity is used for various purposes like heating, cooling, pumping, lifting, moving, cutting, polishing, lighting and so on.  But use for lighting is most common by mass. Hence practically word LIGHT become...