Energy and Power Engineering, 2013, 5, 980-985
doi:10.4236/epe.2013.54B188 Published Online July 2013 (
Modeling Simulation Technology Research for
Distribution Network Planning*
Huanghuang Liu, Dan Liu, Qianjin Liu
School of Electric Power, South China University of Technology, Guangzhou, China
Received January, 2013
This paper proposes to use the power system simulation software CYME to plan, model and simulate for an actual dis-
tribution network for improvin g the reliability and efficiency, enhancing the efficiency and capacity, simulating the ab-
normal condition of distribution network, and presenting operation program of safe, reliable and having simulation re-
cord statements. The modeling simulation results show that the software module has lots of advantages including high
accuracy, ideal reliability, powerful practicality in simulation and analysis of distribution network, it only need to create
once model, the model can sufficiently satisfy multifarious types of simulation analysis required for the distribution
network pl anning.
Keywords: Distribution Network Planning; Modeling Simulation; Load Flow Calculation; Reactive Power
Optimization; Load Balancing
1. Introduction
Distribution network is located in the end of the genera-
tion and transmission, and directly faces to the customers.
With the rapid development of the national economy in
recent years, power demand is increasing sharply, and
the distribution network structures are becoming more
and more complicated, the standard which customers
testing power supply has been increased from the de-
mand of quantity to th e satisfaction of quality. Facing the
grid criss-cross, load information ch anging over time and
a wide variety of power equipment, how to insure the
scientificity, efficiency and reliability of distribution
network planning, reduce network losses and improve
the security and economy of running power distribution
equipment is a major problem in the distribution network
transformation and planning [1-3]. At present, universi-
ties and research institutions have also developed a
number of professional urban distribution network plan-
ning software, and has been applied in the actual work,
but there are still existing two problems [4]: Firstly, some
of the software focused on the level of application man-
agement information systems, and lack a more compre-
hensive function in planning analysis; Secondly, with
low degree of automation, most software required more
manual interv ention and operation.
This paper proposes to use CYME software to perform
more comprehensive modeling and simulation in analysis
level, make use of the abundan t software functionality to
achieve the simulation planning studies for distribution
network. Canadian power system analysis software CYME
is a powerful, practical, advanced simulation tool to as-
sist the power engineers for distribution network plan-
ning in the transmission, distribution and industrial field.
The power grid analysis capabilities and program plan-
ning, case studies function equipped in CYME software,
not only can help power engineers to solve the existing
problems in the power grid planning and operation man-
agement, but also can accurately assess the system’s state
now or future, then improve and reconfigure the system.
CYMDIST package provides comprehensive modeling
and optimization tool for the entire distribution network
(including substations and sub-grid), not only can im-
prove system’s reliability and security, saving operating
and investment expenses, reducing network losses,
maximize the use of the equipment and extend asset life,
but also can provide quick solutions to grid fault or event,
improve planners’ collaboration and increase the plan-
ning capacity.
In this paper, CYMDIST module in CYME software is
used to planning modeling and simulation for an actual
distribution network, the modeling simulation results
show that CYMDIST module in CYME software has
highly accurate, well reliable, powerfully practical per-
formance in distribution network systems planning, op-
eration and analysis. The model which only needs create
once is sufficient to satisfy various types of simulation
analysis required for the distribution network planning,
Copyright © 2013 SciRes. EPE
H. H. LIU ET AL. 981
including balanced or unbalanced system phase voltage
drop calculation, fault calculation, load flow, allocation,
balancing and growth, capacitance placement, switch
optimization and so on.
2. Issues in Distribution Network Planning
The scale of grid investment is far less than the level of
developed countries in the developing process of power
industry, especially the distribution network is lagging
behind, so most distribution system’s net rack is weak [5].
With the continued economic development and people’s
living standard continues to improve, the distribution
system problem is even more severe. The distribution
network is an important part of the power system, the
proportion of investment accounts for about 40% in the
entire power grid investment, especially the urban distri-
bution network with underground cables has larger pro-
portion. Distribution network has low voltage, wide dis-
tribution and more network loss relative to the transmis-
sion grid, the highe st case can be up to 85% in the whole
network. Therefore optimizing planning and design, im-
proving planning efficiency, lowering investment and
operating cost has prominent economic significance.
With the funds of the state investing the power grid
gradually increasing, the work in urban distribution net-
work planning ushers a new challenge. Firstly, grid plan-
ning constru ction and urban planning are in parallel w ith
each other, how to cooperate friendly is problem which
must be solved in urban network planning [6-8]. Sec-
ondly, the power company increasingly focused on the
economic benefits and return of investment, distribution
network planning work rises to a high position. Two
sides changing above not only provide urban network
planning favorable cond itions, but also make it an urgent
task. Therefore, combining with the current national situ-
ation to study in depth city grid planning theory, carry
out the city grid planning technology research, develop
and introduce professional distribution network planning
software to meet the actual requirements, is not only the
urgent needs of our city power grid planning and con-
struction, but also an important scientific means for sus-
tainable the development in the future. To sum up, a kind
of mature and comprehensive software which can be
used flexibly in planning is need to improve the effi-
ciency and reliability of distribution network, CYME
software is introduced into domestic in this context.
3. Features of CYME Software
3.1. Brief Introduction of CYME
The CYME software is a set of professional power engi-
neering software, it takes personal computer and Micro-
soft Windows(R) as operating platform with the conven-
ience and affinity, which is an advanced analysis soft-
ware combining with excellent analytical cap abilities and
advanced interface technologies for electric power dis-
tribution system, transmission systems and industrial
power system [9,10].
3.2. Function Module of CYMDIST
There are more than 250 CYMDIST users around the
world, its module provides integrated, comprehensive,
flexible and fast analysis tool for distribution system
modeling, simulation, and analysis package, which pro-
vides the mainstream GIS system software interface,
including user enterprise database common interface,
customizable user GIS system links, etc., can be ex-
tracted from the GIS database grid connection, and map-
ping to the CYMDIST model in all related equipment, is
widely used in North America for distribution system
planning. CYMDIST software modules have the follow-
ing features [11,12]:
1) It enables to analyze the primary and secondary dis-
tribution network, and its model is suitable for a variety
of distribution network architecture, including the bal-
anced /unbalanced three-phase power grid, two-phase
power grid, single-phase power grid as well as radial grid,
ring network and grid-shaped network.
2) For a same distribution network, it can set up and
manage the analysis in various scenes, where the results
can be customized; It is particularly powerful in the va-
riously hypothetical case, where to create/browse/ mod-
ify the various projects as time goes, so as to do a variety
of simulation and study how the project behaves in the
specified time period.
3) Optimal capacitor location and capacity can reduce
network losses, so as to improve voltage distribution;
Load balance reduces the net loss; load distribution fore-
cast can be predicted based on customers’ electricity
consumption, distribution transformer capacity, and the
actual power consumption or REA method; The motor
starts analyzing.
4) A flexible load model, including a distributed load
and centralized load, can create independent or mixed
load model for each section; The multi-year growth
forecast of the load and merging the functions on the
simulation of load transfer and optimization of grid con-
nection point (tie points).
5) Reliability analysis; Forecast accident analysis (load
recovery); Optimizing the re-election or reorganization
of leads automatically in the specified section; Inserting
distributed generation .
Therefore, combining with CYME software’s relative
advantages on the basis of planning and modeling tech-
niques on the city distribution network of CYME and
avoiding the disadvantages of the traditional urban dis-
tribution network planning method, greatly improving
the reliability of power supply of the power distribution
Copyright © 2013 SciRes. EPE
system, the study is carried out, which not only meets the
needs the reliability of power supply distribution system
in the different urban areas, and to protect the safe opera-
tion of the distribution network and reduce the losses
caused by the accident, ensuring the normal operation of
the modern city, but also improving user satisfaction in
investment savings to laid the basis of the basic theory
and engineering applications on the construction and
4. Planning Modeling and Simulation
4.1. Distribution Network Modeling
This template was designed for two affiliations. This
paper simplifies an under-10 kV distribution network,
where built models by CYMDIST module of CYME
software. The actually simplified distribution network
topology model of this area is shown in Figure 1.
During the modeling in this region, substation of 110
kV or 220 kV is simplified into the equivalent outlet
power of 10kV, which is shown in Figure 1, the node 1,
22, 38 is the power supply po int, which simplified by the
equivalent substations. The remaining nodes are load
nodes. It will be easy for the power distribution network s
to calculate if it uses the power cable of model YJV22-
3*300 when setting up in CYME software module. After
integrating the distribution transformer capacity, average
load is chosen for each load node to start load flow cal-
culation. The following simulation study is about analy-
sis calculation of load flow, capacitance optimal alloca-
tion and load balancing in the CYMDIST module plan-
ning perfo rmance of CYM E sof tware.
Figure 1. Simplified nodes structure diagram of distribution
network in an area.
4.2. Steps of Load Flow Analysis
The load flow analysis was designed to assess the steady-
state performance of distribution network under various
operating condition. It is the basis for planning, design
and operation analysis of any power system, including
power distribution systems, transmission systems and
industrial power systems. Actual distribution network
model of a district in Guangdong power grid is to be built
by the CYMDIST module of CYME software in this
paper, which will make the load flow analysis of the en-
tirely regional distribution network power come tru e .
1) Parameter election
To change the default, adjust the template as follows.
In this example, unbalanced voltage drop iterative method
is used to calculate, setting the convergence error to be
0.01%, and the maximum number of iterations is 60. All
constraints was considered in th e flow calculation to take
into account all the reactive power output of the power
generation equipment constraints, as well as regulating
transformers connector adjustment range constraint. Ad-
justment factor of all load and power generation equip-
ment are set by definition to make load, motor and en-
gine not to be adjusted, that is, the amount of active and
reactive power input device settings will be used in the
trend analysis. ZIP load model is used, which is equiva-
lent to the load model of nP and nQ power function, the
threshold voltage Vz is to set by 80% of rated voltage for
all load types.
2) System and control election
Selecting equivalent powers of all substations which
are belong to this area in system and control election
cards. Choosing all capacitors, generators, motors and
normal operation for transformers tune joint control in
control option card.
3) Load/voltage limit electio n
In this example, planning cond itions is selected for the
limitation category. When the corresponding load capac-
ity limitation column is activated, it enables to input the
respective load capacity limitation into the respective
devices for the grid. The rated condition is turn into
summer, it means that all the summer rated data will use
in the devices. Then voltage limitation is set into the
planning condition, which is of 105% rating over the
voltage limitatio n, or of 95% rating under voltage limita-
tion. After the above settings finish ed for the model, then
starting running, the load flow analysis comes true. The
basic flowchart of the settings can be seen in Figure 2.
4) Simulation load flow analysis results
Within the iterative reporting options, a variety of
load-flow-result statements are pick out, which is re-
quired to display when the simulation ends. These fol-
lowing output statements are selected in this example,
including Abnormal Voltage Areas, Detailed, Feeder
loading, Overloaded conductors and Summary Report.
Copyright © 2013 SciRes. EPE
H. H. LIU ET AL. 983
The electricity price is 0.9635 yuan/kWh according to the
commercially electric degree from 1 to 10 kV, which can
be converted to 0.1547 $/kWh in CYME software units.
Because of the space limitations, this paper only lists 2
load flow consolidated statements as shown in Tables
Figure 2. Flow chart of load flow analysis.
Table 1. Total summary rep ort of load flow.
Total Summary kW kVAR kVA PF (%)
Sources (Swing) 34182.45 20582.03 39900.63 85.67
Total generation 34182.45 20582.03 39900.63 85.67
Load read
(Non-adjusted) 34182.5 21184.41 40214.7 85
Load used
(Adjust) 34182.32 21184.27 40214.48 85
Total loads 34182.32 21184.27 40214.48 85
Cable capacitance 0 602.44 602.44 0
Table 2. Economic loss report.
Annual Cost of System Losses kW MW-h/year k$/year
Cable losses 0.13 1.1387 0.1762
Total losses 0.13 1.1387 0.1762
4.3. Reactive Power Optimization Allocation
Reactive power optimization can install capacitor bank in
the optimum position of feeders to obtain the optimal
load flow distribution with the minimum active power
loss or improvement of system voltage. For the lower
Cable impedance, capacitive compensation test should
not be done. As a result, with the line cable where the
load nodes 34, 35, 36, 37 lyin g replaced by the overhead
line of model JKLYJ-240, the line will appear low volt-
age fault when running the load flow analysis. In order to
solve the problem, it is necessary for capacitor layout to
have an optimized analysis so as to improve voltage dis-
tribution. Under-voltage limitin g value is set as the rating
of 97.5 percent, the threshold voltage is 0.98 kV and tar-
get voltage is 10 kV. When feeder voltage is less than
threshold voltage value, the capacitor analysis program
will be started; Minimum switched capacity is 1 kVAR/
phase, maximum is 200 kVAR/phase, and capacity in-
crement is 1 kVAR/phase. Moreover, the capacitor bank
is installed in one place only. The feeder load level set-
ting is based on the display value under the load level
election card.
After running the analysis of the optimal capacitor
placement, the results card will recommend the optimal
installation site of the cap acitor bank in a tree list, that is,
capacity of the capacitor bank, active power number of
net loss, voltage increment and power factor correction
etc. In addition, when the recommended capacitor bank
installed, the problem of under-voltage on the feeder is
solved after running the load flow analysis again. CYM-
DIST analysis program automatically generates capacitor
bank installation information as shown in Table 3, the
voltage distribution of feeder different from the power
supply point to the caudal section before and after the
capacitance optimization placement, as shown in Figure 3.
Comparing the two graphs in Figure 3, the three-phase
voltage will decrease to the under-voltage limitation as
the distance between the feeder and the power supply
Table 3. Installation information of capacitor.
Information kVAR total kW total %
Fixed capacitance 192.0
Switched capacitor 99.0
Capacitance size /phase 97.0
Loss reduction 0.7
Ideal power factor 90.0
Power factor correcti on 86.6
Voltage increment 2.36
Copyright © 2013 SciRes. EPE
Copyright © 2013 SciRes. EPE
Figure 3. The feeder voltage profile before and after capacitance optimization placement.
Table 4. Load balancing re-phasing suggestion.
ID A phase re-phasing
(kVA) B phase re-phasing
(KVA) C phase re-phasing
40 to C 500 No change to A 0
41 to B 500 to A 0 No change
Table 5. The contrast of load balancing parameters before and after phase sh ifting.
phase A
(A) Phase B
(A) Phase C
(A) Ineutral
(A) Total Losses
(kW) Average kVA
Unbal. Current Unbal .
Factor Voltage Unbal.
Before 832.24 572.45 572.45 259.81 0.06 26.28% 26.28% 0.00%
After 745.64 572.45 659.04 150 0.05 13.14% 13.14% 0.00%
Before 745.64 572.45 659.04 150 0.05 13.14% 13.14% 0.00%
After 659.04 659.04 659.04 0 0.05 0.00% 0.00% 0.00%
point before running the capacitor optimization configu-
ration. In contrast, after running the capacitance optimi-
zation configuration, the variation of feeder three-phase
voltage is maintained within 1% in spite of the increase
in that distance, thereby, it will eliminate the feeder un-
der-voltage fault.
4.4. Load Balancing Analysis
According to the user-defined goal, load balancing will
identify the imbalanced fault of three-phase load to im-
plement conductor commutation or load commutation.
The load node 39, 40, 41 are set to be the A-phase load in
this example, of which the three-phase load will be im-
balance when S39A=S40A = S41A =500 kVA. The balance
current is selected as the objective function, the mini-
mum balance current is 1A, and the smallest current un-
balance factor is 2%. When load balanced analysis func-
tion runs, the program instruction will automatically
identify all possibly executed commutation conductor
with all results displayed on the interface, in addition,
each commutation step includes specific amount of load
transfer and the amount of total net impoverishment.
Running load balance analysis to generate specific
statements as shown in Tables 4-5.
5. Conclusions
This paper uses the CYMDIST module of CYME soft-
ware to plan and model for distribution network, and
achieves three simulation function of load flow, capaci-
tance optimal allocation, load balancing. The application
results show that the software only needs create once
model, it is enough to satisfy various types of simulation
analysis required for the distribution network planning.
CYME software has strong distribution network planning
analysis function, the load flow of distribution network,
including voltage and current, active and reactive power,
network loss can be carried accurate computational analy-
sis. It can carry out the appropriate capacitor compensa-
tion optimized allocation, load balance change equal;
system loss including line loss and transformer loss such
H. H. LIU ET AL. 985
as the annual economic losses can be carried quantify the
estimates. Summary, CYME software brings the facili-
ties for distribution network planning, improves the reli-
ability and enhance the efficiency and capacity of distri-
bution network planning, laying a solid foundation for
the future distribution network to be intelligent and effi-
[1] L. J. Liu, R. Hu, Y. Fu, et al., “Comprehensive Evalua-
tion of Resource Economy Based Distribution Network
Planning Scheme,” Power System Technology, Vol. 32,
No. 16, 2008, pp. 66-70.
[2] T. Kong, H. Z. Chen and T. Y. Xu, “Urban Me-
dium-voltage Distribution Network Planning Based on
ComGIS Network Analysis and Multi-objective Genetic
Algorithm,” Proceedings of the CSEE, Vol. 19, No. 28,
2008, pp. 49-55.
[3] T. Kong, H. Z. Chen, G. Li, et al., “ Review of Power
Distribution Network Planning,” Power System Technol-
ogy, Vol. 19, No. 33, 2009, pp. 92-99.
[4] Q. H. Liu, J. H. Yang and P. Yang, “Distribution Network
Planning and Reconstruction Software Based on GIS
Component,” Power System Protection and Control, Vol.
38, No. 4, 2010, pp. 106-109.
[5] W. H. Yang, Q. R. Gu and X. Z. Hang, “Attention on the
Distribution Power Network Planning During New Pe-
riod,” Power System Technology, Vol. 30, No. S2, 2006,
pp. 588-590.
[6] D. T. C. Wang, L. F. Ochoa and G. P. Harrison, “Modi-
fied GA and Data Envelopment Analysis for Multistage
Distribution Network Expansion Planning Under Uncer-
tainty,” IEEE Transactions on Power Systems, Vol. 26,
No. 2, 2011, pp. 897-904.
[7] C. S. Wang, S. Y. Wang, “The Intelligent Planning of
Urban Mid-voltage Distribution Network Based on Spa-
tial GIS Part one Automatic Routing of Radial Network,”
Automation of Electric Power Systems, Vol. 28, No. 5,
2004, pp. 45-50.
[8] J. A. Peralta, F. de Leon and J. Mahseredjian, “Unbal-
anced Multiphase Load-Flow Using a Positive-Sequence
Load-Flow Program,” IEEE Transactions on Power Sys-
tems, Vol. 23, No. 2, 2008, pp. 469-476.
[9] Cooper Industry and Power System Division, “CYME
Power Engineering Analysis Simulation Software and
Solutions,” Cooper Electric (Shanghai) co., LTD, 2011.
[10] M. A. Salam, Koh Ming Jen and M. A. Khan, “Measure-
ment and Simulation of Grounding Resistance with Two
and Four Mesh Grids,” Proceedings of IEEE Conference
on Power Electronics and Drive Systems (PEDS), Singa-
pore, 2011.
[11] CYMDIST Version 5.02 Reference Manual, Canada:
CYME International T&D Inc., 2010.
[12] H. K. Karegar and M. Arabi, “New Wind Turbine
Grounding System to Reduce Step & Touch Voltage,”
Proceedings of IEEE Conference on Power and Energy
(PECon), Kuala Lumpur, Malaysia, 2010.
Copyright © 2013 SciRes. EPE