V.I.P. Dasanayake_electrical Distribution

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8. What are the advantages and disadvantages of radial and ring distribution?

RADIAL DISTRIBUTION SYSTEM

Radial Power System is a system in which power flows in the direction from the distribution

substation to an individual customer. Radial system looks like a branch of a tree with a main line

connected to a series of a smaller circuit. From the smaller circuit, the circuit will branch off to

contain the customer need. Radial system will have one source of power or a group of power sources

in the same area, So Radial system is the least reliable in terms of continuous service since there is no

back up distribution system connected to the single power source.

Advantages: -

1) Radial distribution system can be installed easily

2) Installing the system is relatively cheap

3) The maintenance is easy

4) Can be used in remote areas

5) Radial system can be expanded

6) This distribution system needs least amount of conductance

7) Minimum duration of interruption and maximum security of supply.

Disadvantages:-

1) If there is a power failure, short circuit, down the power line will cause disruption to

the system

2) And the system cannot be restored until the fault is fixed.3) There will be heavy voltage fluctuation at the end of each line.

4) Consumer line which is near to the feeding point is heavily loaded and consumers

who are far away from the feeding point has heavily fluctuated voltage.

5) The entire line has to be fixed before restoring power

RING DISTRIBUTION SYSTEM


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Ring distribution system is very popular today. The major reason for that

would be though power failure is occurred in one power source, that wont be a problem as

there are many power sources connected to the ring. This distribution system has overcome

several problems that occurred in radial distribution system.

Advantages:-

1) Voltage fluctuation at consumers terminal would be less2) As there are several feeders though power failure occur in one feeder wouldnt

affect for continuity supply

3) As this is a ring system there wont be heavy voltage fluctuations

Disadvantages:-

1) Ring distribution system cant be expanded

2) Due to additional power lines and a grater circuit complexity, this is very

expensive method to install

3) It is very difficult to maintain the system

4) Justification of the loop in requierd areas is tedious

9. What are the methods that can be used to improve the voltage profile in thedistribution system?

1. Use feeder conductor which has large cross section area.

2. Use feeder conductor which has high conductivity, so voltage drop would be

minimum.3. Application of shunt capacitors on the primary feeders.

4. Installing of new primary feeders and substations

5. Install optimal size of capacitor so it would cause achieve voltage profile

improvement with minimum power losses.

6. Introduce voltage regulators out on the primary feeders and in the distribution

substation.

7. Balance the loads on the primary feeders and transfer the load to new feeders

10. Compare and contrast the underground cable distribution system and overhead line

distribution system.


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As the standard construction for utilities because over time it has been the

most cost-effective design, Overhead service was established. Alternatives like underground

cables are requested by the developers, or mandated by cities, the customer benefiting from

the alternative design pays the additional cost.

Safety: - underground cable distribution system is much safer than overhead line distributionsystem, because all underground cable distribution wiring is placed underground,

there is only little chances of any hazard.

Cost: - installing underground cables are very expensive while installing overhead cables are

relatively cheap. The initial cost of an underground system may be five to ten times

than that of an overhead system. (Because we have to use special cables, water proof

equipments, etc)

Maintaining: - maintaining underground cable would be much difficult, compared to the

overhead cables. And complex repair requirements will be needed forunderground cables. The other thing is if fault occurs in underground cable it

is very difficult to find that. But repairing an overhead cable would be much

easy compared to the underground cable

Maintain cost: - The maintenance cost of underground system is very low as compared with

that of overhead system because of fewer chances of fault and service

interruptions from wind, ice, and lightning as well as from traffic hazards.

Current capacitor: -An overhead distribution conductor has higher current carrying

capacity than an underground cable conductor of the same material and cross-

section. On the other hand, underground cable conductor has much lower

inductive reactance than that of an overhead conductor because of closer

spacing of conductor.

Shunt capacitances: - underground system cannot use over long distance due to shunt

capacitance because spacing of conductor. While over head cables

have shunt capacitance in little

Life time: - lifetime of an underground cable is much higher than the overhead cable. An

overhead system may have a useful life of 25 years, while an

underground system may have a useful life of more than 50 years.

Susceptible damage: - while underground facilities are not as susceptible to wind and

debris-blown damage, they are more susceptible to water intrusion

and local flood damage, which can make repairs more time

consuming and costly.

Flexibility: - The overhead system is much more flexible than the underground system. In

the latter case, manholes, duct lines etc., are permanently placed once installed

and the load expansion can only be met by laying new lines. However on an

overhead system, poles, wires, transformer etc., can be easily shifted to meet the

change in load conditions.


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Interference with telephone lines: - overhead system causes electromagnetic interference

with telephone lines, while underground cables dont.

General appearance: - The general appearance of an underground system is better as all the

distribution lines are visible. This factor is exerting considerable

public pressure on electric supply companies to switch over tounderground system.

Occurring of problems: - Overhead cables give problems in short periods of times but

underground cables wont give problems for a long period of time.

Damage and corrosion of underground electrical systems often

shows up days or even months later, causing additional outages

and inconvenience to customers.

Problem from the wind and storms: - winds can damage both types of systems. Overhead

systems face outages resulting from trees. Underground systemsface outages the underground system is more expensive due to the

high cost of trenching, conduits, cables, manholes, and other

special equipments. So the initial cost of an underground system

may be five to ten times than that of an overhead system.

The graph between theoretical and measured voltage values with the length when feedthe cable at a voltage

225V at one end

The graph between theoretical and measured voltage values with the length, when feed

the cable at a voltage 225V at both ends

Length(m)Theoretical

values(V)practicalvalues(V)

0 225 225

57.143 220.54 222

114.286 216.77 219.75

171.429 213.68 218

228.571 211.28 216.75

285.714 209.57 215.5

342.857 208.54 215400 208.2 214.25


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length(m)Theoretical

values(V)practicalvalues(V)

0 225 225

57.143 222.94 223

114.286 221.37 221

171.429 220.88 220.5

228.571 220.88 220.5

285.714 221.57 221

342.857 222.94 223.5

400 225 225

V.I.P. Dasanayake_electrical Distribution

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