This document presents research on upgrading the electrical distribution system in Chiang Mai province, Thailand from a radial to a loop configuration. The objectives are to analyze the effects on power loss reduction, voltage profile improvement, and reliability enhancement. Equations are presented to calculate the power loss, voltage deviation, and reliability indices for the radial and loop systems. Test results on an existing distribution system show that the loop configuration reduces power loss by up to 14.7%, improves the voltage profile, and enhances reliability compared to the radial configuration, especially under heavy loading conditions or load imbalance between feeders.

1. 1. Good Afternoon everybody. Today I would like to present my research Effect of
Upgrading Primary Feeders from Radial to Loop Arrangement on Electrical Distribution
system Performance
2. My Content are 7 topics as follow
1. Introduction
2. Objective of Research
3. Power loss reduction
4. Voltage profile improvement
5. Reliability enhancement
6. Case study and test results
7. Conclusion
3. Introduction
The existing 115 kV primary feeders A and B with an original radial arrangement, fed by two
power transformers that were located at Chiang Mai 3 substation.
>> The practical system data from an Electrical Geographic Information System or GIS
database were imported to the simulation using DIgSILENT-GIS-SCADA – file format.
>> Show in Figure 2
4. The Provincial Electricity Authority (PEA) of Thailand is now planning to reconfigure the
existing 115 kV distribution system in Chiang Mai province from its original radial
configuration to a normally closed-loop arrangement, especially in the metropolitan areas
where higher service quality is required.
>> In this upgrading project, the most important consideration is the impact on the original
system and customers, including power loss, voltage profile, and system reliability.
5. Objective of Research
1. Analyze primary feeders rearrangement from a radial to closed-loop in distribution
system

2. 2. Analyze effect of distribution system upgrading on system power loss reduction,
voltage profile improvement, and reliability enhancement
6. Power loss reduction
The total power loss radial system of the feeders A and B can be computed as in equation 1
>>Equation 1 Show Total power loss in radial system is summation of both total loss in
feeder A and total loss in feeder B
7. The total power loss after reconfiguration can be computed as in equation 2
>>Equation 2 Show Total power loss in loop system is summation of total loss in feeder A,
total loss in feeder B, and total power loss in Tie line.
8. Net power loss reduction in the system is the difference of power losses before and after
reconfiguration, which can be determined as in equation 3
>>Equation 3 Show Total power loss in loop system is summation of total loss in radial
system, total loss in loop system, and total power loss in Tie line.
9. Voltage profile improvement from system reconfiguration can be expressed in term of a
voltage deviation index, which is the difference between the nominal and the actual voltage
value registered during a comparatively slow change in operating conditions.
>> The voltage deviation in all buses of radial and loop systems can be computed as in
equation 4 and equation 5, respectively.
>>Equation 4 Show Voltage deviation in radial system is summation of voltage deviation in
feeder A and Feeder B. Equation 5 Show Voltage deviation in Loop system
>> Net voltage profile improvement in the system is expressed as the difference of the
voltage deviations before and after reconfiguration, which can be calculated as in equation 6.
>>Equation 6 Show Voltage deviation after reconfiguration is different of voltage deviation
in radial and loop system
10. In a distribution system, all equipment such as overhead lines, underground cables,
protective devices, transformers and loads are connected together.
>> Reliability evaluation of each load point focuses on the equipment that effect to the load
point when failure occurs.

3. >> For a series system, an average failure rate, an average annual outage time, and an average
outage time for a load point can be calculated as in equation 7 to 9
11. >> In this part, we compared the conventional radial structure and the loop structure to
explore the advantages from the perspective of system power loss reduction, voltage profile
improvement, and reliability enhancement.
>> An existing distribution system in Chiang Mai province of PEA was used as a test case.
>> The system was divided into 18 sections which were LineA1–LineA9 and LineB1–
LineB9 as shown in Figure 5
>> The two radial feeders were connected together using Tie circuit breaker at their receiving
ends, the radial structure could be upgraded to a loop structure
12. To assess the system performance under different loading conditions, loads in each feeder
were simulated as light and heavy loads, classified by 20% and 80% transformer loading
conditions, respectively as shown in Table 1.
13. Total power losses in each line segment under different system configuration and
transformer loading are summarized in Table 2.
>>Table 2 is compared power loss between radial and loop system.
Figure 6 Show power loss reduction compare with radial and loop system.
14. >>Figure 7 Show percent of power loss reduction. Loop systems have power loss less
than radial systems in every condition.
15. After the two feeders were tied together to form a loop system, currents in each line
segment would be varied.
>> The currents in the line segments of the relatively heavier loading side of the loop would
decrease while those on the lighter loading side increased, i.e. the current flowing from bus
DKA to MJU as illustrated in Figure

4. 16. In addition, currents would flow from the lightly loaded feeder to the heavily loaded
feeder as illustrated in Fig. 2 and 3. This process resulted in the currents in each line section
along the feeder becoming more uniform, and thus the line loss would be reduced.
>>Figure 10 and 11 Show Current flow, Lightly loaded feeder can be supply current to the
heavily loaded feeder
17. PEA is required to keep customer’s voltage profiles on feeders close to a specific rated
value under all load conditions.
>> Voltage deviation from the system upgrading summarized in Table 3. shows that the
voltage profile improvement of the system serving customers under heavy loading conditions
was greater than that of the system with light loading conditions.
>> Moreover, voltage profile improvement under imbalance loading conditions between the
two radial feeders was outstanding.
>> The greater difference in loading conditions, the greater the voltage profile improvement
was. It was obvious that tying the two radial feeders to form a loop system would
considerably improve the system voltage profile.
18. >> Figure 12 Show compares voltage deviation with radial and loop system
19. >> Figure 13 Show Percent of voltage deviation reduction
19. Reliability assessment of the system upgrading shown in Table 4. And Figure 14 indicates
that the system reliability indices of the loop system would be significantly improved in
comparison with the conventional radial system.
>>By system upgrading, customers would be able to receive power from two independent
transformers from the same substation of EGAT without adding additional devices. So in the
case of interruption or damage failure to one source, the second could handle delivering
power to the customers. Therefore, the total number of customer interruptions and customer
interruption durations could be reduced

5. 20. The analytical assessments of upgrading a distribution system from a radial to a normally
closed-loop arrangement were explored in this study.
>> The power loss reduction and voltage profile improvement under imbalance loading
conditions were outstanding. The greater the difference in feeder loading conditions, the
greater the system power loss reduction and voltage profile improvement were.
>> In addition, the major advantage of upgrading the system is reliability enhancement.
However, the significant changes in protection systems required to get the improved
reliability benefit will be addressed in other papers in the next phase of the study.