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BEE3133 Electrical Power Systems
Distribution System: Radial and Ring Distribution
Laboratory 1
Fathimah binti Abdul Halim
EA09089
Faculty of Electric and Electrical Engineering
Universiti Malaysia Pahang
Email: tma_arit91@yahoo.com

Introduction

Generally, distribution system is part of power systems which distributes power to the consumers for utilization. That distribution system is the electrical system between the sub-station fed by the transmission system and the consumer meters. The distribution systems consist of feeders, distributors and service mains. A feeder is a conductor which connects the sub-station (or localised generating station) to the area where power is to be distributed. Basically no tappings are taken from the feeder so that current in it remains the same throughout. A distributor is a conductor from which tappings are taken for supply to the consumers. The current through a distributor is not constant because tappings are taken at various places along its length. A service main is generally a small cable which connects the distributor to the consumer’s terminals. In practice, the radial system and ring main system are used.

Experiment 1: Radial Distribution System

Introduction
Electricity suppliers normally use radial distribution in rural areas where the load is randomly distributed, separated by areas with little or no habitation, and back up supplies are normally not available. The length of feeder is typically limited to 500m or less. In the radial distribution system, feeders supplying the consumers are all fed from a central point (the substation) as shown in Figure 1. There is no looping of the feeders.

Figure 1: Radial System of Feeders

Objective
To demonstrate the principles of the commonly used radial system for low voltage distribution networks.

Schematic Diagrams:

Figure 2: Schematic diagram for Experiment 1 Procedure A

Figure 3: Schematic Diagram for Experiment 1 Procedure B

Figure 4: Schematic Diagram for Experiment 1 Procedure C

Results for Procedure A:

Table 1: Lamp Voltages
Load| Voltage|
Lamp 1| 23.0V|
Lamp 2| 18.0V|
Lamp 3| 14.0V|
Lamp 4| 11.0V|
Lamp 5| 9.0V|
Lamp 6| 8.0V|

Results for Procedure B:

Table 2: Results for Procedure B
Circuit Number| Lamp| Feeder|
| Measured Voltage| Measured Current| Voltage Drop|
1| 22.0V| 0.048A| 6.0V|
2| 17.0v| 0.055A| 12.0V|
3| 13.0V| 0.060A| 15.0V|
4| 10.0V| 0.062A| 18.0V|
5| 9.0V| 0.061A| 20.0V|
6| 8.0V| 0.060A| 21.0V|

Table 3: Calculated and Measured Resistor Currents and Voltages

Resistor Number| Calculated Current| Calculated Voltage Drop| Measured Voltage Drop| Error| 1| 0.846A| 8.0V| 6.0V| 25.00%|
2| 0.654A| 13.0V| 12.0V| 7.69%|
3| 0.500A| 17.0V| 15.0V| 11.76%|
4| 0.385A| 20.0V| 18.0V| 10.00%|
5| 0.346A| 21.0V| 20.0V| 4.76%|
6| 0.308A| 22.0V| 21.0V| 4.55%|

Table 4: Lamp Voltages

Lamp number| Calculated voltage| Measured voltage| Error| 1| 22.00V| 22.0V| 0%|
2| 17.00V| 17.0V| 0%|
3| 13.00V| 13.0V| 0%|
4| 10.01V| 10.0V| 0.10%|
5| 9.00V| 9.0V| 0%|
6| 8.01V| 8.0V| 0.12%|

Results for Procedure C:

Table 5: Separate Feeders
CircuitNumber| Lamp| Feeder|
| Measured Voltage| Measured Current| Voltage Drop|
1| 28.0V| 0.067A| 1.0V|
2| 26.0V| 0.066A| 3.0V|
3| 25.0V| 0.061A| 4.0V|
4| 24.0V| 0.061A| 6.0V|
5| 22.0V| 0.059A| 7.0V|
6| 21.0V| 0.057A| 8.0V|

Discussion:

The voltage across each lamp in procedure A, decreased as well as the brightness of the lamps due to the increase in the distance of the lamps from power supply.  As the current passes through a longer distance, more the value of voltage is "lost" (unavailable to the load), due to the voltage drop developed across the resistance of the conductor. In the...
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