Informative video from ABB on developments in DC Power Transmission and distribution. It also touches on some of the advantages of DC over AC
Deep Cycle Batteries
Deep Cycle Batteries are batteries which can be discharged to very low levels. These batteries are generally used where continuous use of the battery is required such as in battery operated vehicles such as golf carts, floor sweepers and forklifts.
The deep cycle battery differs from other batteries in its construction. The plates of the battery are thicker as compared to the sponge type plates of other batteries.
The use of solid plates with lower surface area in the deep cycle battery means that the battery cannot give sudden pulses of high current as may be required for batteries used in applications vehicle starting. The deep cycle battery is designed to provide a high current over a long period.
Deep Cycle batteries are widely used in the field of renewable energy. They can be used to store energy from solar panels during the day and can be discharged during the night. Deep Cycle batteries usually have a higher C rating (refer article on C rating). This enables them to be discharged over many hours.
Deep Cycle batteries are widely used in the field of renewable energy. They can be used to store energy from solar panels during the day and can be discharged during the night. Deep Cycle batteries usually have a higher C rating (refer article on C rating). This enables them to be discharged over many hours.
Peak Load Shaving
Peak Load Shaving refers to operating certain generators specifically to address peak demands in the load cycle of a utility. The load cycle tends to peak in the mornings and falls during the noon. It again rises in the evening and the night.
Managing these peaks in the load cycle is an important function of distribution systems. Peak Load Shaving, as this process is known, is done by starting certain power sources specifically to offset this peak demand. These are usually sources with higher generating costs like diesel generator sets. These power sources are run only during periods of peak loads or in times of emergency.
Managing these peaks in the load cycle is an important function of distribution systems. Peak Load Shaving, as this process is known, is done by starting certain power sources specifically to offset this peak demand. These are usually sources with higher generating costs like diesel generator sets. These power sources are run only during periods of peak loads or in times of emergency. Another method of peak load shaving is by providing incentives to customers to reduce consumption during times of peak demands. This levels the load cycle curve and enables optimum loading of power sources.
Synchronous Compensators
Synchronous Compensators are synchronous motors which are run without any load. These motors are used to generate or absorb reactive power from the system. Generally located near large loads, these motors, running in the overexcited condition provide reactive power according the the load demand.
In large transmission lines, the line capacitances generate excessive capacitive line charging current which can lead to a rise of voltage in the system. In such a scenario, the synchronous compensator can run underexcited and absorb the excess reactive power. This is particularly true in EHV (Extra high voltage systems) where the capacitive line charging is higher than the magnetizing power of the load even during loaded conditions.
While static reactors and capacitors can be used in reactive power regulation in lines, sychronous compensators have the advantage of quick responses and fine control depending on the excitation.
In newer installations, static compensators with thyristor controls have replaced synchronous compensators owing to their low maintenance and running costs.
In large transmission lines, the line capacitances generate excessive capacitive line charging current which can lead to a rise of voltage in the system. In such a scenario, the synchronous compensator can run underexcited and absorb the excess reactive power. This is particularly true in EHV (Extra high voltage systems) where the capacitive line charging is higher than the magnetizing power of the load even during loaded conditions.
While static reactors and capacitors can be used in reactive power regulation in lines, sychronous compensators have the advantage of quick responses and fine control depending on the excitation.
In newer installations, static compensators with thyristor controls have replaced synchronous compensators owing to their low maintenance and running costs.
Thyrite Arrestors
Thyrite is a material obtained by a special type of clay mixed with carborundum (Silicon Carbide). Thyrite is used widely in lightning arresters. Thyrite is a non-linear resistor. i.e. it has high resistance at low voltages and low resistance at high voltages. A two times increase in voltage causes the current to increase by nearly 12 times. Hence, heavy currents can be discharged during voltage strikes and other surges. This heavy discharge of current enables quick reduction of the surge voltage preventing flashovers. The Thyrite arresters are usually arranged in parallel with the primary winding of the Transformer. The Thyrite inside the arrester is arranged in the form of discs. The sides of the discs are metal plated to decrease resistance between the discs.
Once the surge has been discharged, the Thyrite quickly returns to its high resistance state.
Slow Blow Fuses
Slow Blow fuses are fuses which have an inherent time delay. These fuses are widely used in motor protection circuits. These fuses help discriminate between the high inrush current of motors and a high current caused by a fault.
The time delay in the fuse is achieved by designing the fuse element with a higher mass for the same current rating. This higher mass causes the element to heat gradually in the event of an overcurrent. Thus, the fuse element takes time to heat and melt to isolate the current.Kraft Paper Insulation
Kraft Paper is a special paper used in electrical insulation. Kraft paper is just plain paper from which the alkaline salts have been removed. It is usually impregnated with mineral oil, jelly or wax to improve its dielectric properties.
Kraft paper is made thermally resistant by applying a diamond patterned epoxy resin to both sides. This is known as thermally upgraded Kraft paper which finds wide application in oil filled transformers for coil layer insulation.
Paper capacitors are also made using Kraft paper as the dielectric.
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