The Online Journal on Power and Energy Engineering (OJPEE)
Vol. (2) – No. (1)
Impact of Power Factor Correction on the
Electrical Distribution Network
of Kuwait – A Case Study
Osama A. Al-Naseem and Ahmad Kh. Adi
Electrical Engineering Department, College of Engineering and Petroleum
Kuwait University, State of Kuwait
Abstract-The electrical distribution network in Kuwait
has undergone several improvements over the years to
ensure a higher capacity and efficient electricity service to
all consumers. Power factor correction (PFC) is one of the
techniques recently applied to the electrical distribution
network in Kuwait. Applying proper PFC methods
compensates the effect of reactive loads of the system and
hence improves the system’s overall efficiency. Such
improvement permits a reduction in the size of
switchgear, transformers and cables which imply lower
cost [1]. This paper presents a case study that shows the
advantages of power factor correction for the electrical
distribution network in Kuwait.
A switchgear factory is selected to perform the case
study in this paper. Measured data is taken on the factory
site before and after installing power factor correction
capacitors. The data includes power factor, active power,
reactive power, apparent power, and current. By
improving the power factor of the site from 0.75 to 0.95,
the kVA capacity of the distribution transformers
(supplying the factory) increases by 21.05%. Results are
then used as a model to reflect the estimated total kVA
savings in the electric power system in Kuwait. Analyses
of the results prove that PFC significantly reduces the cost
of electric power production in Kuwait and increases the
capacity and efficiency of the electrical power system.
I. INTRODUCTION
During recent years, increasing attention has been paid to
minimize the energy cost and inefficiency in electricity
generation, transmission and distribution [2].
When designing a compensation scheme, one should
attempt to achieve the most economical solution in which the
saving achieved in the equipment cost is significantly greater
than the procurement cost of the reactive power [3].
Different systems are available to produce reactive energy
and improve the power factor. Particularly, shunt capacitors at
the nearest point to the loads is a well established approach to
improve the power factor. Shunt capacitors are attractive
because they are economical and easy to maintain. Not only
that, but also they have no moving parts, unlike some other
devices used for the same purpose [4].
Connected equipment (transformers, motors, etc.) cause a
phase angle between current and voltage. When the current is
Reference Number: W10-0030
phase shifted, it takes more current to deliver the same
amount of active power [5].
Figure (1)
Figure 1 shows that prior to installation of capacitor bank,
all the reactive power (noted as Q1) of the facility is supplied
by the utility, so the apparent power (noted as S1) is high
because both the active and the reactive power have to be
supplied by the utility. The added capacitor bank supplies
reactive power (noted as Qcap) to the load, so the facility
doesn’t have to draw this reactive power from the utility, but
rather only the difference (Q1 - Qcap). A low demand of
reactive power translates into a low consumption of apparent
power to the utility, thus releasing the capacity in the system.
Reactive power is not used to do work, but is needed to
operate equipment. Many industrial loads are inductive such
as motors, transformers, etc. The current drawn by an
inductive load consists of magnetization current and power
producing current. The magnetizing current is required to
sustain the electro-magnetic field in a device and creates
reactive power. An inductive load draws current that lags the
voltage, in that the current follows the voltage wave form.
The amount of lag is the electrical displacement (or phase)
angel between the voltage and current (refer to Figure 2).
II. CASE STUDY
A Switchgear Factory was selected as a case study for this
paper. This factory is supplied with electricity from the
distribution utility through 1600 kVA, 11/0.433 kV
transformer feeding a Main Low Tension Board (MLTB).
The maximum demand of this factory is 1250 kVA at a power
factor of 0.75. A 300 kVAR Capacitor Bank was installed at
the MLTB bus in this factory to improve the power factor.
In this case study, the measurements of Power Factor (PF),
Active Power (P), Reactive Power (Q), Apparent Power (S),
and Current (I) were illustrated during 12 working hours
(from 06:00 to 18:00 hrs) in a day time before and after
operating the Capacitor Bank that was installed at the MLTB.
173
The Online Journal on Power and Energy Engineering (OJPEE)
Vol. (2) – No. (1)
Field Measurements:
TIME
(HRS)
6:00
Figure (2)
Figure 3 shows a general schematic diagram for the system
under this study.
Table (1): Before PFC
P
Q
S
I
PF
(KW) (KVAR) (KVA) (A)
0.77 188
156
244 326
8:00
0.77
272
225
353
471
10:00
0.74
328
298
443
591
12:00
0.75
303
267
404
539
14:00
0.75
303
267
404
539
16:00
0.74
286
260
386
515
18:00
0.76
283
242
372
497
TIME
(HRS)
6:00
Table (2): After PFC
P
Q
S
I
PF
(KW) (KVAR) (KVA) (A)
0.94 188
68
200 267
8:00
0.96
272
79
283
378
10:00
0.94
328
119
349
465
12:00
0.95
303
100
319
425
14:00
0.94
303
110
322
430
16:00
0.95
286
94
301
401
18:00
0.94
283
103
301
401
POWER FACTOR vs. TIME
0.80
0.60
PF (Before PFC)
0.40
PF (After PFC)
0.20
18:00
16:00
14:00
12:00
10:00
8:00
0.00
6:00
POWER FACTOR
1.00
TIME (HRS)
Figure (4)
REACTIVE POWER vs. TIME
0.500
Qx1000 (Before PFC)
(KVAR)
0.300
0.200
Qx1000 (After PFC)
(KVAR)
0.100
18:00
16:00
14:00
12:00
10:00
8:00
0.000
6:00
QX1000 (KVAR)
0.400
TIME (HRS)
Figure (5)
Figure (3)
Reference Number: W10-0030
174
The Online Journal on Power and Energy Engineering (OJPEE)
APPARENT POWER vs. TIME
0.500
SX1000 (KVA)
0.400
Sx1000 (Before PFC)
(KVA)
0.300
0.200
Sx1000 (After PFC)
(KVA)
0.100
18:00
16:00
14:00
12:00
10:00
8:00
6:00
0.000
Figure (6)
CURRENT vs. TIME
0.600
0.500
0.400
0.300
0.200
0.100
0.000
Ix1000 (Before PFC)
(A)
18:00
16:00
14:00
12:00
10:00
8:00
Ix1000 (After PFC)
(A)
6:00
IX1000 (A)
Distribution Losses:
Distribution losses in a facility can be reduced by the addition
of capacitors and the resulting increase in power factor. These
losses are estimated by summing estimates of the
transformers losses and cable losses. This reduction is due to
the decrease in current flowing through the distribution
system and is sometimes referred to as “I2R” losses [4]. This
relationship is given by the following equation:
P = I 2R
TIME (HRS)
TIME (HRS)
Figure (7)
From Figure 4 to Figure 7, it is clearly shown that:
1) The average power factor improved by 21% as it was
0.75 before PFC and became 0.95 after PFC.
2) The average loading on the transformer released by
26% as it was 372 kVA before PFC and became 296
kVA after PFC.
3) The losses of the cable reduced by 36% as the average
current passing through the cable was 497 A before
PFC and became 395 A after PFC.
4) The capacitor compensated 61% of the consumed
reactive power as the average was 245 kVAR before
PFC and became 96 kVAR after PFC.
System Capacity:
Power factor correction permits additional loads to be added
and served by the existing system. In case if the transformers
or cables get overloaded, improving the power factor will be
the most economical way to reduce the current and therefore
eliminate overload condition.
From the above field’s measurements, the power factor was
improved from 0.75 to 0.95, and due to this improvement, the
demand decreased and can be calculated using equation 1:
PFinitial
(1)
S new =
× S old
PF final
S new =
Vol. (2) – No. (1)
0.75
×1250 = 986.84 kVA
0.95
By improving the power factor from 0.75 to 0.95, the capacity
of the transformers released by 21.05%, which is equivalent
to 263.16 kVA.
Reference Number: W10-0030
(2)
Reducing the current in a distribution system therefore
reduces power losses in wire conductors and transformers.
Although, the economic benefit from distribution losses alone
may not be sufficient to justify the installation of capacitors, it
is an additional benefit, especially in the facilities with many
transformers and long feeder that serve low power factor
loads.
Distribution system losses are proportional to the current
squared, and since current is reduced in direct proportion to
power factor improvement, the losses are inversely
proportional to the squared of the power factor. The following
formula applies:
% Loss Re duction = [1 − (
PFinitial 2
) ] × 100
PF final
(3)
Taking into account that PFinitial = 0.75, and PFfinal = 0.95,
% Loss Re duction = [1 − (
0.75 2
) ] ×100 = 21.05%
0.95
Due to power factor improvement, the new current through
the cable can be calculated using equation 2:
I new =
I new =
S new
(4)
3V
986.84
= 1315.83 A
3 x 0.433
The load current dropped from 1666.72 A to 1315.83 A.
Simple Payback Period:
PFC system combined of Fixed Cost and Running Cost. The
Fixed Cost of the installed capacitor with its accessories is
KD 5,676/-. The Running Cost is the annual maintenance cost
for this capacitor. However, for calculating the simple
payback period, the fixed cost will be considered as total
invested cost. Also, the life period for the capacitors is 15-20
years.
Released in kVA = 1250 – 986.84 = 263.16 kVA
Approximate cost for 1 kVA equal to KD 10/Total cost for the released kVA = 263.16 * 10 = KD 2,630/-
175
The Online Journal on Power and Energy Engineering (OJPEE)
Simple Payback Period =
Invested Cost
Saving Cost
5,676
=
= 2.16 years
2,630
(5)
III. CONCLUSIONS AND RECOMMENDATIONS
From the cast study on the Switchgear Factory, it has been
found that in order to have good performance for the
electricity supply system, it is important to optimize the
power factor between 0.9 and 0.95. This will eliminate waste
in electrical energy and increase the output without the need
to install additional transformers and cables.
PFC in distribution system will indeed release generation
and transmission capacities. Moreover, due to tightly
interconnected nature of the system, the exact benefit due to
capacity release in these areas is quite difficult to compute.
Capacity releases in generation and transmission levels is
probably more relevant in compensation studies at these areas
and hence are left out from the economic analysis of
capacitors application in distribution system.
Improved power factor result in:
a) Released system capacity.
b) Improved plant efficiency.
c) Reduced overloading of
switchgear, etc.
cables,
transformers,
The implemented investigation had shown that the
capacitor pay itself usually within a couple of years. The
positive impacts of improving the power factor in industrial
sector represented in saving money and in improving the
system efficiency.
Recommendations for improving the power factor rates are
presented hereunder.
It is noticed that some plants in Kuwait are not using any
type of PFC systems. Hence, it is recommended to impose
low power factor penalty clause in billing system to force the
consumers to improve the average power factor to acceptable
limits.
Vol. (2) – No. (1)
A harmonic study should be performed before installing the
capacitors in the distribution network. The presence of
harmonics can affect the proper operation of the existing
machinery which will lead to a techno-economic impact.
It is advisable to install the capacitors in the distribution
network rather than the transmission network as the effect
will be extended to the upstream networks. Also, the cost of
LV capacitors is extremely less than the cost of the HV ones.
Co-operation between distribution and transmission sectors is
vital in this field, so that the cost and the benefits can be
shared in between.
There are no immediate environmental benefits because
increasing the power factor does not result in reduced
electricity consumption. However, it does contribute to a
reduced need to construct new power stations which bring
benefits to the environment in the long term.
REFERENCES
[1] OMEISH Taufik & OMEISH Faraj “Effect Of Low
Power Factor In Libyan Electrical Distribution System”
CIRED. May 2003
[2] Mohamed A. EL-HADIDY, Samir A. EZZ EL-ARAB,
Dalal H. HELMI, & Mohamed T. IBRAHIM “The
Impact Of Capacitor Bank Installation On The
Performance Of Distribution Systems – A Case Study”
CIRED. May 2007
[3] S.O .Onohaebi, O.F. Odiase, & S.I. Osafehinti
“Improving The Efficiency Of Electrical Equipment By
Power Factor Correction – A Case Study On Medium
Scale Study In Nigeria” Journal of Mathematics and
Technology. April 2010
[4] Ramasamy Natarjan “Power System Capacitors” Taylor
& Francis. 2005
[5] T. Miller “Reactive Power Control In Electric Systems”
John Wiley & Sons. 1982
[6] Imad H. Ibrik & Marwan M. Mahmoud “Energy
Efficiency Improvement By Raising Of Power Factor At
Industrial Sector In Palestine” Pakistan Journal of
Applied Sciences. 2002
Also, appointing a third party for periodically measurement
of power factor and checking the power factor compensation
equipment is recommended.
Reference Number: W10-0030
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