distribution systems in India and their problems

7/27/2019 distribution systems in India and their problems

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ELECTRICAL & ELECTRONICS ENGINEERING

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Contents To Be Covered: Definition

Classification Of Distribution System

Distribution System Losses

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Introduction: Distribution system is a part of power system, existing

between distribution substations and consumers.

It is further classified on the basis of voltage

Primary distribution system- 11 KV or 6.6 KV or 3.3 KV

Secondary distribution system- 415 V or 230 V

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Classification Of Distribution

System: It can be classified under different considerations as;

1. Type Of Current:

a) AC Distribution Systemb) DC Distribution System

2. Type Of Construction:

a) Overhead System

b) Underground System

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3. Type Of Service:

a) General Lighting & Power

b) Industrial Power

c) Railway d) Streetlight etc

4. Number Of Wires:

a) Two Wireb) Three Wire

c) Four Wire

5. Scheme Of Connection:a) Radial Distribution System

b) Ring or Loop Distribution System

c) Interconnected Distribution System

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Radial Distribution System: Most distribution systems are radial. Only one path is connected between each customer and

substation. Electrical power flows along a single path. If interrupted, results in complete loss of power to the

customer.

Advantages: Low cost . Simple planning.

Disadvantages : Low reliability factor. Distributor nearer to feeding end is heavily loaded.

Consumers at far end of feeder would be subjected to series voltage fluctuations. 6



Ring or Loop Distribution System:

It consists of two or more paths between power sourcesand the customer.

It is selected to carry its normal load plus the load of the other half of the loop also.

Advantages: Less conductor material is required.

Less voltage f luctuations.

More reliable.

Disadvantages:

It is difficult to design as compared to the design of radial system.

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Interconnected Distribution

System: It is supplied by a number of feeders. Radial primary feeders can be tapped off from the

interconnecting tie feeders.

They can also serve directly from the substation.

Advantages: Increases the reliability of supply

Losses are less

Quality of service is improved.

Disadvantages: Its initial cost is more.

Difficult in planning, design and operation.

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DC Distribution:

Voltage drop along distributor is considered as a mainfactor while designing a distributor.

It depends upon the nature of load and also on

feeding, whether it is fed at one or both ends.

According to loading, a distributor can be classified as:

i. Feed at one end.

ii. Feed at both ends.

a) With equal voltages.

b) With unequal voltages.

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Ring Distribution:

It is a distributor which is arranged in the form of aclosed circuit.

Can be fed at one or more points.

In a ring distributor any two load points are joined by

means of a connector also called interconnector. Purpose of connector is to reduce voltage drop in

various sections.

Advantages Of Using Interconnector :

Increased security of service.

Reduction in number of standby plants.

Total capital cost and running cost can be reduced by

dividing the total load. 10



Stepped Distributor: It is also known as tapered distributor.

It is necessary to design distributor with minimum

volume of conductor material. Load when tapped from any distributor changes the

current along the length of the distributor.

Various sections of stepped system should be

proportional to the square roots of appropriatecurrents.

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AC Distribution: All methods used for solution of DC distributors will

apply equally for AC.

Ring or radial, stepped, fed from one end, fed from boththe ends

The resistances have to replaced by impedances.

Current and voltage in various sections is the vectorsum and not simply arithmetic sum.

In three-phase systems, all calculations should becarried out on a single-phase basis and final resultscan be given in line values.

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Distribution System Losses:

70% of the total losses occur in the primary and

secondary distribution system.

Distribution losses amount to 15.5% of the generation

capacity.

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Factors Affecting Distribution-

System Losses: Inadequate Size of Conductor.

Feeder Length.

Location of Distribution Transformers. Low Voltage.

Use of Over-Rated Distribution Transformers.

Low Power Factor.

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Methods For The Reduction Of Line

Losses:

1. HV Distribution System.

2. Feeder Reconfiguration.3. Reinforcement Of The Feeder.

4. Grading Of Conductor.

5. Construction Of New Substation.

6. Reactive Power Compensation.

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Thank you

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distribution systems in India and their problems