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Parallel Feeder.

A parallel feeder consists of duplicate feed system having two-radial feeders running in parallel.The two feeders may originates from the same or different secondary substations.Each feeder supplies...

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Design of Seocondary Network.

The best method is to use a calculating board because the network characteristics can not be easily determined by analytical methods.It is necessary to have adequate information about loads,available...

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Lamp Flicker.

The voltage regulation on a system has two aspects.One is the normal drop in voltage from no load to full load.The other is the momentary sudden change of voltage due to a change of load.This sudden...

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Types of Flicker.

Lamp flickers may be classified as cyclic high frequency flicker,cyclic low frequency flicker,non-cyclic frequent flicker and non-cyclic infrequent flicker. Cyclic high frequency flicker:The flicker...

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Short Circuit Capacity.

An important aspect of power systems is its short circuit capacity which is the product of system voltage and fault current.Since the system voltage is assumed to be 1 pu and fault current is the ratio...

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Design of earthing grid.

The following steps should be followed for the design of an earthing grid. Data needed for design. Substation ground area. Soil resistivity at the site. Fault clearing time. Maximum grid current....

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Concrete Encased Electrodes.

Concrete,being hygroscopic,attracts moisture.When concrete is buried in earth it behaves as a semiconductor medium having a resistivity of 30 to 90 ohm.In medium and high resistivity soils a rod...

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Tower Footing Resistance.

The effectiveness of a ground wire depends to a large extent on the tower footing resistance.The tower top potential depends on this resistance to a large extent.A low value of tower footing resistance...

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Isolated neutral or ungrounded system.

The main feature of an unrounded neutral system is its ability,in some cases,to clear ground faults without interruption.This self clearing feature disappears when the length of line becomes...

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Measurement of Earth Resistance.

The measurement of earth resistance of any electrode is done by the fall of potential method.E is the earth electrode under test.Two auxiliary electrodes P and C are placed at suitable distances from...

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Measurement of Soil Resistivity.

Soil resistivity is measured by four electrode method suggested by F.Wenner.Four metal rods whose diameter is small as compared to length are driven into earth at equal distances.A known current I is...

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Impulse Behavior of Earthing systems.

The degree of protection provided by an earthing system under lightning discharge conditions depends on its impulse impedance and not the power frequency resistance.The impulse impedance is different...

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Effectively Earthed System.

The term 'effectively grounded' has replaced the older term 'solidly grounded'.A transformer neutral may be connected to earth directly without any impedance between neutral and earth.However, the...

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Resistance Earthing.

When neutral is grounded through a resistance,arcing grounds are eliminated.The value of resistance should be such that ground fault current is less than 3-phase short circuit.This is necessary so that...

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Reactance Earthing.

As per IEEE definition reactance grounding means grounding through impedance the principle element of which is reactance.This grounding is used when the zero sequence reactance of system is so low as...

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Grounding Transformer.

Sometimes the neutral of a power transformer is not available for grounding.In such situations a special small size y-delta transformer is solely used for grounding.This transformer is known as a...

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Present Practice in Neutral Earthing.

When power systems were small low voltage systems,they were operated with neutral isolated.However as systems grew in size and voltage level.the earthing of neutral became necessary.The arc suppression...

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Corrosion.

Corrosion is the deterioration of metals and alloys by electrochemical reactions with their environments.The essential phenomenon is the same in all metals and alloys but the degree is different in...

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Theory of Corrosion.

The condition necessary for corrosion to occur are:presence of electrolytic and presence of anode and cathode.an electrolyte is any liquid having ions.One drop of rain water contains billions of...

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Factors Governing Corrosion of Metal Buried in Soil.

The corrosion of metal buries in soils depends on the intrinsic properties of the metal type of dissimilar metals which are in the soil where the earthing conductor is buried,areas of anode and...

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