Working of Ground Wires

Direct lightning strokes on transmission lines represent the major source of the failed power system. The objective of the good line design. Therefore, should be to reduce the number of interruptions due to lightning. This objective demands a two-point procedure-first, the incidence of direct strokes to the system should be minimum and secondly, the amplitude and steepness of the overvoltage arising out of the few strokes that will hit the lines should be kept to a minimum. On both the counts, ground wires are found to be suitable.

The earthing is provided with the following objectives

1. For the safety of equipment and personnel against lightning and voltage surges providing the discharge path for lightning arresters, gaps, and similar devices. Grounded neutral systems are provided by the ground connections.

2. The grounding of power systems is highly important. A substantial and adequate ground that will not burn off or permit a dangerous rise in voltage under abnormal conditions is essential. Extensive damage and danger arise when inadequate grounds have been provided.

In neutral earthing (or neutral grounding), the neutral points (star points) of star-connected 3-phase winding of power transformers, generators, earthing transformers are connected to low resistance ground. The major advantages of neutral earthing are:

(1) Each fault can be utilized to operate protective relays to isolate the fault.

(2)1nduced static charges are conducted to earth without disturbance.

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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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