Reconfiguration and Load Balancing By Software Simulation In A Real Distribution Network for Loss Reduction

8/9/2019 Reconfiguration and Load Balancing By Software Simulation In A Real Distribution Network for Loss Reduction

1/6

Canadian Journal on Electrical and Electronics Engineering Vol. 2, No. 8, August 2011

386

Reconfiguration and Load Balancing By Software

Simulation In A Real Distribution Network for Loss

ReductionH. Bagheri Tolabi , M. Gandomkar and M. Bahreyni Borujeni.

Abstract — To get the distribution network to operate at its

minimum loss optimum performance, reconfiguration was

been proposed and researched. Considering, however, that

optimum performance implies minimum loss, no overloading

of transformers and cables, correct voltage profile, and

absence of phase voltage and current imbalances, network

reconfiguration alone is insufficient. It has to be

complemented with techniques for phase rearrangement

between the distribution transformer banks and the specific

primary feeder with a radial structure and dynamic phase andload balancing along a feeder with a radial structure. This

paper contributes such a technique at the medium-voltage

level of a distribution network with reconfiguration. This

paper introduces a CYMEDIST based analysis for the phase

balancing/loss minimization problem. An application example

of the proposed analysis has been applied to Khorramabad

city's MV distribution network.

Key Words — load balancing, power loss, reconfiguration, MV

distribution system.

I. INTRODUCTION

studies show that a considerable part of the losses in powersystems is related to the electricity distribution network . There

are several ways to reduce losses in distribution system . Many

of methods need the new equipment installed within the system

in addition to the financial burden for companies, it is possible

new errors produce in network and due to disturbances in their

services .

One of the ways of reducing losses in the distribution

network is reconfiguration of MV distribution network .

reconfiguration is a simple and cheap way for loss reduction in

distribution systems because we don’t need to invest capital

and set up new equipment in system . we can reduce the losses

only by change the state of existing switches. there are many

goals for reconfiguration of distribution systems such as :1- reconfiguration in order to loss reduction.

H.Bagheri tolabi, with Islamic Azad university Khorramabad branch,Iran (e-mail: [email protected]).

M.Gandomkar is currently lecturer of Islamic Azad university Savehbranch , Iran.

2- reconfiguration in order to load balancing.

3- reconfiguration in order to increase stability and improving

voltage profile .

4- reconfiguration in order to increase reliability of network .

5- reconfiguration in order to minimizing the times cutting off

electrical current for services and …

II. PROBLEM DESCRIPTION AND FORMULATION

The distribution system is the final stage in the transfer of

power to individual customers. Typically, it commences from

the secondary of the sub-transmission station transformers, andnormally consists of two levels – primary distribution or

medium voltage (MV) level, and the secondary distribution or

low voltage (LV) level.

There are two types of switch in primary distribution

systems:

normally closed switch which connects line sections, and

normally open switch on the tie-lines which connects two

primary feeders, or two substations or loop-type laterals.

Network reconfiguration(or feeder reconfiguration) is the

process of altering the topological structures of the distribution

feeders by changing the open/close status of the sectionalizing

and tie switch [1]. In general, distribution loads show different

characteristics according to their corresponding distributionlines and line sections.

Therefore, load levels for each time period can be regarded as

non identical. In the case of a distribution system with some

overloaded and some lightly loaded branches, there is the need

to reconfigure the system such that loads are transferred from

the heavily loaded to less loaded feeders. The maximum load

current which the feeder conductor can take may be considered

as the reference. Nevertheless, the transfer of load must be

such that a certain predefined objective is satisfied. In this

case, the objective is to ensure the network has minimum real

power loss. Consequently, reconfiguration may be redefined as

the rearrangement of the network such as to minimize the total

real power losses arising from line branches. Mathematically,the total power loss can be expressed as follows [7]–[9]:

∑=

+ L

i i

ii

i

V

QPr

1

22

(1)

V V V iiimaxmin

≤≤

where ir ,i

P ,i

Q and V iare respectively, the resistance, real

power, reactive power, and voltage of branch , and L is the


2/6


387

total number of branches in the system. The aim of this study

is to minimize the power loss represented by (1) subject to the

following constraints. The voltage magnitude of each node of

each branch must lie within a permissible range. Here a branch

can be a transformer, a line section or a tie line with a

sectionalizing switch.

III. The information needed to design 20kv khorramabad

single line diagram in CYMDIST software environment

For simulation MV distribution network of Khorram Abad

in software environment and attention to the equations (1) in

previous section, the necessary information are included

details of local and electrical conditions of feeders , stations

and substations , the impedance of lines , load of transformers,

and … .

we received them from Electricity Distribution Company of

Lorestan . Due to the large volume of the information ,as an

example the limited information from a station listed in table

1.

TABLE I INITIAL INFORMATION OF SAMPLE STATION

IV. simulation of 20kv network in CYME software

environment

First considering received information such as the kinds of

impedances, peak load of buses, properties of lines, distances,

switches and …,the single line diagram with all details was

designed, which can be seen in figure 1 .

A. power flow analysis and calculate the losses before

reconfiguration

with complete information of network in the software

environment, after power flow analysis on feeders, the total

amount of losses under the title "losses before reconfiguration"

calculated that was nearly equivalent to 4066 kw. Due to large

number of feeders ,for example one report loss of the

"goldasht" feeder is shown in table 2 . its loss is about 196.8

kw.

Figure 1. 20kv single line diagram of khoramabad in software

environment

TABLE 2

REPORT OF LOSSES FOR A SAMPLE FEEDER IN THE

SOFTWRAE ENVIRONMENT

B. reconfiguration for network Initial Results

The network reconfiguration operates with opening and

closing 4 suitable switches.

Beginning with opening the 14408NH 47320 key and

closing 14408 SB 46020 key, some of load would be

transferred from one feeder to another, and losses will be

reduced a little. finally with the opening 12403NH53610 key

and closing 1240NH53530 key losses reduce about 116 kw .

Entirely, in this reconfiguration amount of loss reduction is

about 2.87 percent .the results are shown in tables 3 and 4 .the

proposed keys schematic on single line diagram can be seen inin figures 2 and 3 .

TABLE 3

REPORT OF SWITCHES POSITION IN INITIAL

RECONFIGURATION

stationfeeder

Peak

of

load

(A)

Total

length

(KM)End of line

ghaziabad

20 MVA

shagayeg2108.5

charahban

k

saheli1655.7parkeshahr

maicrowave1105.6ostandari

goldasht17017

Goldashte

gharbi

poshteh1904.7poshteh

koyefelstin1204.7ghaziabadshariati703.5meidan


3/6


388

TABLE 4

REPORT OF INITIAL RECONFIGURATION AND REDUCTION OF

LOSSES

Figure 2. schematic of 1 and 2 keys in the initial reconfiguration

Figure 3. schematic of 3 and 4 keys in the initial reconfiguration

TABLE 5

REPORT OF SWITCHES POSITION IN RENEWED

RECONFIGURATION

C. Renewed reconfiguration with proposed keys by the

software

With a renewed reconfiguration and put 20 number of

proposed keys by the software

in new positions ,the amount of total losses will be reduced.

the proposed keys in the table 5 and report of loss reduction inthe table 6 are shown. with renewed reconfiguration the loss

will be minimized and reduced about 6.34 percent .

you can see the complete report in the appendix of this

article. due to a large number proposed keys on single line

diagram ,we ignore showing all of their schematics and the

keys 3 ,4 ,5,16 and 17th

will be represented in figures 4 and 5.

TABLE 6

REPORT OF RENEWED RECONFIGURATION AND REDUCTION

OF LOSSES

Figure 4. schematic of 4 and 16 keys in the renewed reconfiguration

Figure 5. schematic of 3, 5 and 17 keys in the renewed reconfiguration


4/6


389

V. Optimum reconfiguration and load balancing in the

network

We can see load imbalance of phases in Abnormal

Conditions report before reconfiguration.

After the optimal reconfiguration and power flow analysis

the load imbalances and consequently total losses will be

reduced . as an example , you can see the condition of"Parkesaheli" feeder before and after load balancing in tables

7, A and B. after reconfiguration in this feeder, the number of

overloads and low voltages consecutive will be decrease from

8 and 6 to 6 and 4 numbers, and total losses will be reduce

about 4.58 kw.TABLES 7 (A AND B)

REPORT OF LOAD IMBALANCES AND RELEVANT LOSSES IN

PARKSAHELI FEEDER

A) before reconfiguration

B) After reconfiguration

VI. CONCLUSIONS

In this paper, we study and simulate the Khorramabad MV

distribution network in CYMDIST software and calculate total

losses and load imbalance by power flow analysis before and

after optimal reconfiguration .results show that the total losses

and load imbalances will be reduced by suitable switch

optimization .With a renewed reconfiguration and put the 20 number of

proposed keys by software in new positions ,the amount of

total losses will be reduced maximally .


5/6


390

APPENDIX

Full report of renewed reconfiguration by the software proposed keys relevant IV.C part.

REFERENCES

[1] S. Civanlar and J. J. Grainger, “Distribution feeder reconfiguration forloss reduction,” IEEE Trans. Power Del., vol. 3, pp. 1217–1223, Jul.

1988.

[2] T. H. Chen and J. T. Cherng, “Optimal phase arrangement of distribution

transformers connected to a primary feeder for system unbalance

improvement and loss reduction using genetic algorithm,” IEEE Trans.

Power Syst., vol. 15, no. 3, pp. 994–1000, Aug. 2000.

[3] C. C. Liu, S. J. Lee, and K. Vu, “ Loss minimization of distribution

feeders: Optimality and algorithms,” IEEE Trans. Power Del., vol. 4,

no. 2, pp. 1281–1289, Apr. 1989.Authorized licensed use limited to: University of Newcastle. Downloaded on July 09,2010

at 18:31:16 UTC from IEEE Xplore. Restrictions apply.

2540 IEEE TRANSACTIONS ON POWER DELIVERY, VOL. 22, NO. 4, OCTOBER

2007

[4] C. B. Alexandre, A. Carlos, and Newton, “Main chain representation

for evolutionary algorithms applied to distribution system reconfiguration,”

IEEE Trans. Power Syst., vol. 20, no. 1, pp. 206–212, Feb. 2005.

[5] M. E. Baran and F. F.Wu, “Network reconfiguration in distributionsystems

for loss reduction and load balancing,” IEEE Trans. Power Del.,

vol. 7, no. 2, pp. 1401–1407, Apr. 1989.

[6] M. Siti, A. A. Jimoh, and D. Nicolae, “Load balancing in distribution

feeder through reconfiguration,” presented at the IECON, Raleigh, NC,

Nov. 6-12, 2005.

[7] M. Siti and A. A. Jimoh, “Reconfiguration circuit loss minimization

through feeder reconfiguration,” presented at the SAUPEC Conf.,

Stellnbosch, South Africa, 2004.

[8] Ukil, M. Siti, and J. Jordaan, “Feeder load balancing using neural

network ,”presented at the Int. Symp. Neural Networks, Chengdu, China,

May 28-31, 2006.

[9] Matlab Documentation – Neural Network Toolbox MathWorks,

Natick, MA, 2002, 0.180913a, Release 13, 6.5.

[10] C. S. Chen and M. Y. Cho, “Energy loss reduction by critical switches,

of distribution feeders for loss minimization,” IEEE Trans. Power Del.,

vol. 4, no. 3, pp. 1246–1253, Jul. 1992.

[11] X. Yang, S. P. Carull, and K. Miu, “Reconfiguration distribution

automation

and control laboratory: Multiphase radial power flow experiment,”

IEEE Trans. Power Syst., vol. 20, no. 3, pp. 2156–2166, Aug.

2005.

[12] A. Auguglio, L. Dusonchet, and M. Giuseppe, “Minimum losses

reconfiguration

of MV distribution networks through local control of

tie-switches,” IEEE Trans. Power Del., vol. 18, no. 3, pp. 762–771,

Jul. 2003.

[13] H. Salazar, R. Gallego, and R. Romero, “Artificial neural networks andclustering techniques applied in the reconfiguration of distribution systems,”

IEEE Trans. Power Del., vol. 21, no. 3, pp. 1735–1742, Jul.

2006.

[14] H. Kim, Y. Ko, and K.-H. Jung, “Artficial neural-network based feeder

reconfiguration for loss reduction in distribution systems,” IEEE Trans.

Power Del., vol. 8, no. 3, pp. 1356–1366, Jul. 1993.

BIOGRAPHIES


6/6


391

Majid. Gandomkar:He was born in the Saveh from IRAN. He is PHD

degree of Electrical Engineering from Science and Research Branch of

Islamic azad university.his research interests are distribution systems, DG

systems ,optimization and etc. Now, he is assistant professor at Islamicazad university, Saveh branch.

Hajar.Bagheri Tolabi: She was born

in the Khorramabad from IRAN. Shereceived her B.Sc. degree Electrical

Engineering field in 2005 of the Bu-Ali

Sina University and M.Sc on power

engineering of Saveh branch Azad

University in 2009. Her researchinterests are included distributionsystems, optimization , renewableenergy.

Mohammad.Bahreini Borujeni: He is electricalengineer and now the Director of Electricity

Distribution Company of Lorestan. his research

interests are distribution systems and power

systems.

Documents

Reconfiguration and Load Balancing By Software Simulation In A Real Distribution Network for Loss Reduction