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text in Modelling of Phuntsholing LV distribution network and analyzing the technical losses using DIgSILENT power factory software.

Sanga Chophel, Pema Leyzom, Sonam Paldon Dorji, Pasang.

College of science and Technology. Royal University of Bhutan.

Abstract.

In this paper the LV distribution network of Phuentsholing is taken under consideration to analyze different technical losses associated with it. The major technical losses in the distribution and transmission networks are losses in transformer and the losses in power lines. Technical losses is the cause of inefficiency in power sector and thus it is important to study losses and analyze various technique to mitigate such losses in considerable amount. In this paper different technical losses in the network is theoretically calculated and also the losses are analyzed from network which is modeled in DIgSILENT power factory software. The battery storage is used to reduce technical losses in the system by sing the model in DIgSILENT power factory software.

Key words: - Technical losses, Loss mitigation, Battery storage, Distribution Network, DIgSILENT Power Factory.

Introduction.

Efficient use of energy has become one of the most effective methods to go for sustainable usage of already exhausted energy resources. Studies carried out to identify viable options to combat climate change have revealed that improving energy efficiency measures are more effective in preventing climate change than developing energy supply technologies (regional report).  

In power sector, it is the power losses that are there in both distribution and transmission which contribute in-efficiency of energy usage. The power loss is associated in the process of transferring the power to customer and performance of the utility largely depends upon the level of power loss in the network. The losses not only affect utility performance of customer but also reduces the income generation of respective company.

Thus in this paper the model of the LV distribution network of different LV feeder in Phuntsholing was developed in DIgSILENT power factory and technical losses occurring in the system was analyzed.  

Literature review.

The technical loss and its analysis in selected distribution network are performed using PSS/Adept program. In the evaluation of losses, the result of theoretical losses was compared with the result obtained from practical measurement. It was found out that low-voltage transformer and distribution line losses constitute maximum value at around 18.72% of the total losses [1]. The proper selection of distribution component and to investigate cost analysis is the major controlling factor in order to reduce those technical losses.

An analysis of technical and non-technical losses and its impact on the power sector was done in India owing to their power sector being characterized by inadequate and insufficient power supply [2]. The huge amount of energy is lost in the Transmission and distribution system by the technical and non-technical losses. Thus this paper analyzes technical and nontechnical losses and its impact on power system by case study and MATLAB Simulation in power system.

In India, due to continued rising trend of losses in distribution network, study on technical and non-technical losses done in Ambattur industrial Estate-SS distribution network (India) fed from a main intake of 110 KV which is fed to two main loads to zones of 33KV for Industrial User & 11KV for residential users using ETAP (Electrical transient analysis program) shows that there were total losses of 3.6kW of base losses and 9.52kW of studied losses. The technical losses caused by material properties and its resistance to the flow of electrical current in distribution was analyzed and simulated through electrical transient analysis program. It was also found out that transformer having the maximum losses of 8.9kW. Installation of capacitor banks, relocation of distribution transformers, ensuring a constant Power Factor to industrial users, avoiding overloading of transformers and resizing of conductors are some of the recommended mitigation techniques [3].  

A study [4]on technical and non-technical losses for loss reduction in distribution systems have been initiated in Mazoon Electricity Company (MZEC) due to the increasing cost of supplying electricity, the shortage in fuel with ever-increasing cost to produce more power, and the global warming concerns. Reduction of the technical losses were studied and the following projects were examined:(a) installing parallel feeders for overloaded feeders according to the approved security standard, (b) introducing transformer(s) for overloaded substation, (c) installing more capacitor banks at the primary feeder which will help in boosting the voltage and improving the power factor as well as reducing there active power losses, and (d) introducing more links between the feeders to facilitate load sharing. Results revealed that there was a little decrease in the active power but the reactive power decreases considerably. On the other hand, the losses were dramatically reduced and voltage profiles were improved to be within the standard tolerance ''6 %.

Their simulation results have shown that the implementation of these projects leads to a significant improvement in voltage profile, and reduction in the active and the reactive power losses.  The economic analysis was also done and had revealed that the implementation of the proposed projects in MZEC leads to an annual saving of about US$ 5 million. The study is still in progress to investigate the effect of using distributed generation (DG) on losses reduction before and after implementing the aforementioned projects.

This paper [5] considers different loads (residential, commercial and industrial), using calculations through load factor improvement and simulation (DIgSILENT) methodologies in order to develop accurate and authentic results. The results were further analyzed to develop an optimum solution. Those solutions are mainly aimed at improving the load factor with battery energy storage by peak shaving. It focuses on improving technical losses caused by circulating current (I2R), thereby improving the overall energy efficiency when a battery energy storage is involved. The battery energy storage system has indicated positive response and the load factor have shown improvement.

Implementation of DG at the different location and the variation of power losses with changed in location has been simulated and analyzed using DIgSILENT PowerFactory software in Turkey [6]. It was observed that the DG in the network and other power source can improve the losses in the network significantly thereby increasing its efficiency.

Theoretical analysis has been carried out to estimate the losses involved in transformers in Pune, India and found out that total losses due to transformer in the feeder is 8.57% of the total input to the substation [7]. An assessment and minimization of distribution transformer loss is done in detail with help of ETAP software simulation from the past data in MAMBALAM substation and found out the total losses due to transformer in the feeder is 0.71% of the total input to the substation [8]. A proper maintenance and a lower kVA ratings of the transformer can save the losses occurring in the network.

This paper [9] aims to reduce the distribution losses in a commercial section. The first step that they have used in power loss minimization procedure is loss calculation as it is a common tool to optimize the design, operation and planning of the electrical network. They have used these two methods and compared for power loss calculations between field measurement and simulation results. Here the technical loss was minimized by complete removal of low voltage network and considered that the reduction of power loss as the proper planning of network. It has observed that the distribution losses as 23.17 % and after adopting various mitigation techniques the losses was reduced to 3.85%.

The paper [10] is for optimal planning and reduction of technical loss in distribution network. In this paper the selection of optimal conductor size and the placement of capacitor in radial distribution network was considered to be practical planning. Here the technical operational constraints are available conductors and capacitors, voltage limit, maximum permissible carrying current of conductors. It uses particle swarm optimization (PSO) to solve power loss minimization.  By applying this method, they have observed reduction in final cost of network planning, losses and their cost are considerably reduced and improved voltage profile was achieved.

The [11] capacitor placement and distribution network reconfiguration (DNR) are two useful methods in reducing the power losses of distribution networks. This paper proposes a selective particle swarm optimization (SPSO) to solve the optimal capacitor placement problem, the optimal feeder reconfiguration problem, and the problem of a combination of the two. The problem is posed as an optimization problem with an objective to maximize the loss reduction and improve the voltage profile. The proposed method has been implemented on two distribution systems published in the literature. The simulation results have indicated that the proposed method is reliable, easy to implement and can be used as an advantageous alternative in the comprehensive optimization for power loss reduction in distribution networks. Furthermore, when simultaneously account both feeder reconfiguration and capacitor placement, the loss reduction is much higher than considering them separately.

The above presented papers and other related papers has given us profound ideas in understanding different technical losses that are present in distribution networks. Moreover it has provided us with different methodologies to calculate technical losses with much efficient and accurate way. Furthermore, we were gained lot of knowledge to reduce or mitigate various technical losses that are present in existing distribution networks. Thus those literature has helped us in understanding more about our project topic and thus help us to proceed further with our project.

Technical losses

The amount of power (kW or MW) that is lost in the distribution network either during transportation or during delivery is known as the power loss. The factors on which the power losses depends are network configuration, power factor, load profile, power factor, and materials of the network and the length of network. Power loss can be also transformed to the energy loss as kWh, MWh or GWh and it indicates the power lost over the period of time.

Except for the fixed load, current flowing through the line/network changes with the change in load. The loss in the network, therefore, varies with the current. For the varying load, Average Technical Loss can be determined from the Peak Load by considering LOAD FACTOR and LOSS LOAD FACTOR as explained hereunder.

Distribution Line losses

The line losses depend on the types of conductor being used and the load that are there on the feeders. The line loss is directly proportional to the product of square of current and the resistance of the conductor. The current in the line increases with the increase in the load and vice versa and thus the line losses varies throughout the day. Though line lasses in the network are also contributed by other factors like inductance of the line and extra, this project only considers the line losses that are contributed by current and conductor resistance. The equation given below are adopted to estimate the line losses that are there in the network.

Distribution Line Losses(kWh)=Loss factor ''Line Losses''period

Where                              

    Loss Factor=0.33LF+'0.67LF'^2                             

    Load factor (LF) =(Average Load(kWavg))/(Peak Load (kWpeak))

Power transformer losses.

The two main components of transformer are no-load losses and load losses. Every kind of transformer has such kind of losses despite their different applications and rating.

Though there are other losses such as losses created by harmonics in larger transformer and also the losses caused by its auxiliary parts.

 No load loss or Core loss

No-load losses are present in the transformer core whenever the transformer is energized. No load losses are also known as iron losses or core losses. This losses constant despite varying load.

No-load losses are composed of: Hysteresis losses, Eddy current losses.

Load loss or Winding Losses

These losses are known as copper losses or short circuit losses and it vary with the variation of transformer loading.

The winding losses are estimated by using the equation given below.

Winding Losses=('MVA'^(2 )''Load Losses''Loss Factor)/('MVA'^2 peak )

Loss factor=K''LF + 0.8LF2

Where K = constant and the value for K are:

0.2: for distribution system and

0.3: for transmission system.

Load losses= Copper Losses from the report test    

The above standard transformer losses for different rating was used in the theoretical calculation of transformer losses. It is standard approved by international organization like ISO and other. The losses for transformer which are not there in above are obtained by interpolation and the extrapolation of above data and the transformer losses are calculated.

TABLE for STANDARD of TRANSFORMER LOSSES

SL.No kVA rating At 100 % Loading

Wi (Watt) Wc (Watt)

1 10 70 190

2 16 75 300

3 25 125 425

4 50 210 1250

5 100 340 2150

6 200 570 3600

7 250 610 4450

8 315 720 5460

9 400 850 6450

10 500 1000 7800

11 630 1200 9300

12 800 1420 11000

13 1000 1750 13500

14 1250 2100 16400

15 1600 2550 19800

'

Overview of 66/33/11kV Phuentsholing substation.

Phuentsholing under Chhukha Dzongkhag is one of the biggest city in Bhutan and has people working in different private and government organization. It is also the biggest business center for both commercials as well as the industrial. It is therefore very important to study and analyze the distribution network. The Phuntsholing city is supplied power through a 66/33/11 kV substation located at Dhamdara.

The feeders which are taken into consideration are as listed below.

PWD feeder.

Ashay Bungalow.

Ramitey Feeder.

Water Booster feeders.

Tading Rural feeder.

BPC colony (Pepsi-Bhutan dairy feeder) feeder.

Average peak load in January 2015.

Water Booster Feeder.

Likewise we modelled all other feeder in DIgSILENT power factory.

SL.No. Feeder  name Losses From DIgSILENT (kW) Theoretical Losses (kW)

1 BPC Colony    17.26 16.18189

2 Tading Rural Feeder 19.98 19.47128

3 Ashi Bungalow 8.28 8.19380

4 Ramitey Feeder 17.01 15.23194

5 PWD feeder 22.53 25.77693

6 Water booster 25.04000 22.71972

Losses obtained from DIgSILENT power factory software and theoretical calculation.

Table 2: Comparison between losses obtained from theoretical and from DIgSILENT power factory.

The load details of every feeders are taken from the PBIS report of January month of 2015 and during this calculation the load are taken as the average peak load of that month. The percentage loading of each transformer are considered to be equal depending upon their ratings. The losses obtained from different methods are as given in the table below. The losses include both transformer and line losses.

METHODS TO REDUCE TECHNICAL LOSSES OF DISTRIBUTION SYSTEM IN PHUENTSHOLING.

There are many methods which can be applied in distribution network to reduce technical losses to considerable magnitude. One of the most durable mitigation technique which we can adopt in such network is by placing the energy storage battery in different locations. We can also analyze the losses reduction by replacing the conductors with one which has lowest resistances.

Placing energy storage battery in the network.

In this project, we placed different rating of energy storage battery in different location in distribution network model which was developed in DIgSILENT power factory. The battery capacity of 0.02 to 0.2 MW with reactive power ranging from 0.02 to 0.2 MVAR was implemented. The battery increases the voltage in different node and reduces the technical losses which are there in the network.

The storage may be charged from main grid during base load generation which is when the load demand is low and is typically during early hour of the day and towards midnight of that day as indicated by available load profile of different feeders as given in figure below.

The different storage incorporated in the distribution feeders are as given in the following figures.

BPC colony Feeder.

Figure 5: Battery storage installed in BPC colony feeder.

Likewise the battery storage in different feeder was placed in different location with different number.

Feeder Losses Before (kW) Loss after Battery Bank(kW) Percentage Saving

BPC Colony 17.26 17.1 0.92%

Tading Rural 19.98 12.62 36.84%

Ashi Bungalow 8.28 7.37 10.99%

Ramitey 17.01 13.89 18.34%

PWD 22.53 15.47 31.34%

Water booster 25.04 24.87 0.68%

RESULTS.

It is observed that the technical losses can be reduced by installing battery storage system in the network. When battery storage in installed in network, the reduction of current is observed and thus the technical losses values are also reduced. The reduction of losses improves further with the increase in the number of battery storage in the system. The result obtained is given in the table 3 as compared to the result obtained without the battery storage.

Figure 6: Graph showing comparison of loss after and before mitigation.

Table 3: Table showing losses comparison between before and after installing the battery bank in the system of different feeder.

Conclusion.

The theoretical technical losses of the LV Phuntsholing distribution network was calculated in this paper. The distribution network was also modeled in the DIgSILENT power factory software and technical losses is analyzed. The theoretical technical losses and the losses obtained from the modelled network in DIgSILENT was compared the theoretical results. The battery storage was used for losses minimization and it was observed that the losses in the distribution network can be reduced by installing battery storage in network.

References

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[2] J. Navani, N. Sharma and S. Sapra, "A Case Study of Analysis of Technical and Non Technical," International Journal of Advances in Engineering Science and Technology.

[3] M. Mahmood, O. Shivam, P. Kumar and G. Krishnan, "Real Time Study on Technical Losses in," International Journal of Advanced Research in Electrical, Electronics and Instrumentation Engineering, vol. 3, 2014.

[4] Y. Al-Mahroqi, I. Metwally, A. Al-Hinai and A. Al-Badi, "Reduction of Power Losses in Distribution Systems," International Journal of Electrical, Computer, Energetic, Electronic and Communication Engineering, vol. 6, 2012.

[5] S. Bakana, "Investigation and mitigation of electric power," 2015.

[6] A. AKSOY, "The Effects of Distributed Generation on System Power Losses," Afyon Kocatepe University Journal of Science and Engineering, 2016.

[7] V. A. Kulkarni and P. K. Katti, "Estimation of Distribution Transformer Losses in Feeder," International Journal of Computer and Electrical Engineering, vol. 3, 2011.

[8] Tamizharasi.P, Anuradha.R and Ayshwarya.A.R, "ANALYSIS OF DISTIRIBUTION TRANSFORMER LOSSES IN FEEDER CIRCUIT," International Journal of Innovative Research in Advanced Engineering (IJIRAE), vol. 1, no. 1, (March 2014).

[9] A. KHAZAEE and M. GHASEMPOUR, "DISTRIBUTION LOSS MINIMIZATION: A CASE STUDY IN A COMMERCIAL SECTION," in 22nd International Conference on Electricity Distribution, Stockholm, 2013.

[10] L. Mohammadian, M. T. Hagh, E. Babaei and S. Khani, "Using PSO for Optimal Planning, and Reducing Loss of Distribution Networks".

[11] T. M. KHALIL, A. V. GORPINICH and G. M. ELBANNA, "COMBINATION OF CAPACITOR PLACEMENT AND RECONFIGURATION FOR LOSS REDUCTION IN DISTRIBUTION SYSTEMS USING SELECTIVE PSO," in 22nd International Conference on Electricity Distribution , Stockholm, 2013.

[12] A. Aguila, Carri''n and L. Ortiz, "Analysis of power losses in the asymmetric construction of electric distribution systems," IEEE LATIN AMERICA TRANSACTIONS, vol. 13, 2015.

[13] M. Madrigal, J. J. Rico and L. Uzcategui, "Estimation of Technical Energy Losses in Electrical," vol. 13, 2015.

[14] C. N. G. Lozano, J. F. R. Diaz, G. Gutitrrez and C. Olarte, "Loss Reduction in Distribution Networks using Concurrent Constraint Programming," 8* International Conference on Probabilistic Methods Applied to Power Systems, Iowa Stale University, Ames, Iowa,, 2004.

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