Minimum Oil Circuit Breaker

These types of circuit breakers also utilize oil (transformer oil) as an interrupting medium. Unlike bulk oil circuit breakers, these designs place the interrupting units in insulating chambers at the live potential. This feature of the design of MOCBs reduces the requirement of oil and these breakers are therefore known as minimum oil circuit breakers. These I designs are available in voltages ranging from 1000 V to 765 kV using the multi-break technique. A typical view of 36 kV MOCB indicating the main parts is shown in figure 4.24.

This type of breaker is Widely used in transmission and distribution networks. In an oil circuit breaker, they are drawn across the contacts are contained inside the interrupting pot and thus the hydrogen bubble, formed by the vaporized Oil (gas) is also contained inside the chamber. As the contacts continue to move and When the moving contact rod separates itself from the orifice at the bottom of the chamber, an exit similar to a nozzle becomes available for exhausting the hydrogen that is trapped inside the interrupting chamber

It is well-known that minimum oil circuit breakers are sensitive to high TRV peak and prone to restrikes during switching capacitor banks. However, this problem has been effectively countered by pressurizing the interrupter heads with dry nitrogen.

These types of breakers were found to be more suitable for applications in countries with very low ambient temperatures like Canada, Russia, and Finland, where the gas blast circuit breakers become more sensitive to icing and liquefaction problems.

Due to their cross blast designs, minimum oil HV circuit breakers suffer from a few major inherent problems such as sensitivity to high peak voltage and the effects of pre-arcing. Usually, the out of phase switching test is the most difficult, test on MOCBs, which generally dictates the number of interrupters to be used in series for a particular voltage class. The energy released due to pre-arcing is very high and high strength insulating materials are required to enable cross jet pots and jet plates to “withstand high-pressure surges. The number of breaks per pole also depends upon the ability‘of the arc interrupting chamber to withstand the energy released due to PRC-arcing, which is a function of current in the arc and voltage per break.

Presently this technology is considered outdated due to the advent of VCB technology medium voltage and SF6 technology m the high voltage range.

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Limitations of Terzaghi Theory

Limitations of Terzaghi Theory The value of the coefficient of consolidation has been assumed to be constant. The distance d of the drainage path cannot be measured accurately in the field. The thickness of the deposit is generally variable, and an average value has to be estimated. There is sometimes difficulty 1n locating the drainage face, and sometimes thin previous seams that can act as good drainage faces are missed in the boring operations. The equation is based on the assumption that the consolidation is one-dimensional. In the field, the consolidation is generally 3-dimensional. The lateral drainage may have a significant effect on the time rate of consolidation. The initial consolidation and secondary consolidation have been neglected. Sometimes these form an important part of the total consolidation. In actual practice, the pressure distribution may be far from linear or uniform.

Types Of Current Collector

Current Collector A current collector is a device used to collect electrical current from a moving conductor, such as a train or a trolley. It is typically used in electric vehicles, such as trains and trams, to transfer power from an overhead power source to the vehicle's electric motor. The current collector consists of a sliding contact, which is often made of carbon or copper, that makes contact with an overhead power source, such as an overhead catenary wire or a third rail. The sliding contact is mounted on the vehicle and is typically in the form of a pantograph or a trolley pole. The pantograph is a device with a metal frame and a spring-loaded arm that presses against the overhead power source. It is raised and lowered by the operator of the vehicle, and as it moves along the overhead power source it maintains contact and collects the electrical current. The trolley pole is a vertical pole that is mounted on the roof of the vehicle and has a horizontal arm that extends out

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