Single & Three Phase Tap Lines in Rural Distribution System – from the viewpoint of loss minimization ⚡️ Part #2

This blog is a continuation of “Single & Three Phase Tap Lines in Rural Distribution System” series, previous part of this article can be found HERE.

the image is used for thumbnail purpose, courtesy of pixabay..!

In a power distribution system, the physical properties of the component causes technical loss.

The power loss is proportional to the total line resistance of the conductor and the square of current flowing through that portion of line. Mathematical expression for the technical power loss can be expressed as,

The ratio of average power delivered to the peak load of a certain period. The load factor for a 11 kV feeder of the Rural Distribution System varies between 40% to 60%.

Cost considered :

🔸 Cost of technical loss

The total cost for technical loss is calculated multiplying the technical loss unit (kWh) by electricity billing rate. This applies for whole life period of the instrument.

🔸 Cost of distribution line construction

The construction of distribution line cost includes material costs and labor costs. This applies once in its lifetime.

🔸 Cost of maintenance

The maintenance cost of lines is the expense needed to keep the line in working condition. This includes repairing, right of way clearing, etc. This cost also occurs over whole life of the line.

Case Study 📝

For the purpose of this research work, we assume a distribution line feeding from a substation. This line is three phase backbone line. The line is constructed by #4/0 ACSR conductor and the line to line voltage of this line is 11 kV. The load distributed by the backbone line is 1.6 MW. The study is to identify the effects of system loss of the tap line for three phase and single phase system.

🌟 When All Taps are Single Phase 🌟

Let us consider the length of the backbone line is 10 km. The current feeding from the starting point for R-phase, Y-phase and B-phase is 110 A, 80 A and 74 A respectively. The system will be unbalanced for the single phase taps in this system. Phase balancing becomes critical for this single phase tap as it is long and loaded.

R-phase contains two single phase taps. First tap is 3 km and second tap is 9 km apart from starting point. The first tap contains 33 A current and the second tap carries 66 A current.

Y-phase contains two single phase taps. First tap is 5 km and second tap is 10 km apart from the starting point. The first tap contains 33 A and the second tap contains 42 A current.

In B-phase, there is also two single phase taps. The first tap is 4 km and the second tap is 8 km apart from the starting point. First tap carries 36 A and second tap carries 33 A of current. The connection is shown in the Fig. 1.

Fig. 1. Three phase system with single phase tap.

For simplicity of the calculation, the load factor is considered as 0.5 for all over the line.

Also considering both the single phase and three phase taps are constructed by #3 ACSR bare conductor. From the equation, the value of RP and RT is 0.3522 Ohm and 1.3946 Ohm respectively which is the value for resistance per km per phase of #4/0 ACSR & #3 ACSR. The cost of electricity is considered 14.71 cent(€) per kWh.
So,

Sample calculation for Section-1, Tap-1 is discussed below,

R-phase, Section-1 :

R-phase, Tap-1 :

Similarly calculation for other sections and taps has been carried out to find the total cost of the proposed Single Phase model.

References

Muhammad Usman, Fabio Bignucolo, Roberto Turri, Alberto Cerretti, “Power Losses Management in Low Voltage Active Distribution Networks”, iEEE Xplore, accessed on 25th February, 2018.

The next part of this series will include the calculation and analysis for Three Phase system and the comparison among the two RDS.

An apology for using Screenshots in terms of expressing equations. I'm trying to use Latex and hopefully will be using from next post. 🌝

~Tennis Girl 🎾🎾