Journal of Renewable Energy, Electrical, and Computer Engineering

Journal of Renewable Energy, Electrical, and Computer Engineering, 1 (2) (2021) 79-84
Vol. 1, No. 2, September 2021, 79-84
e-ISSN: 2776-0049

Research Original Article

DOI: https://doi.org/10.29103/jreece.v1i2.5237

Analysis of the Effect of Loading on the Transformers Usage Time
Adi Syahputra Ritonga1, Muchlis Abdul Muthalib2, Muhammad Daud2, Hamdi Akmal Lubis3, Biswas Babu
Pokhrel4, Sudip Phuyal5, & Umakant B. Gohatre6
1 Renewable Energy Engineering Master's Program, Malikussaleh University, Bukit Indah, Lhokseumawe, 24351, Indonesia
2 Department of Electrical Engineering, Malikussaleh University, Bukit Indah, Lhokseumawe, 24351, Indonesia
3 Faculty of Civil Engineering, Geo-and Environmental Sciences, Karlsruhe Institute of Technology (KIT), Karlsruhe, Germany
4 Mid-Western University, Nepal
5 Kathmandu University, Nepal
6 SIGCE, Navi Mumbai, Mumbai university, Maharashtra, India

adiritonga01@gmail.com; muchlis.abd@unimal.ac.id; mdaud@unimal.ac.id; hamdi.lubis@kit.edu; pokharelbabubiswas@gmail.com;
sudip1@yahoo.com; umakantgohatre1@gmail.com


Corresponding Author: adiritonga01@gmail.com| Phone: +6285297395431

Received: September 8, 2021

Revision: September 21, 2021

Accepted: September 28, 2021

Abstract
The reliability and stability of the system in the operation of the electric power system is very important, in order to
provide comfort in service to consumers. The transformer is a very important component in the electric power system,
because it is used as a voltage adjuster for the load being served. This study discusses the effect of loading and
temperature on the life shrinkage of 36/60 MVA power transformers in block 3 and block 4 carried out at PT. PJB UBJ
O&M PLTMG Arun Lhokseumawe, Aceh. From the calculation results after 4 years the transformer operates, if the
transformer is given a 100% load, the transformer will experience an age difference of 2.52 p.u/day so that it has a
remaining life for of 10 years. As for the transformer that is given a load of 90%, the transformer will experience an
age difference of 1.44 p.u/day so that it has a remaining life to perform operations for another 18 years. Then for a
transformer that is given a load of 80%, the transformer will experience an age difference of 0.67 p.u/day so that it
will have a remaining life to carry out the operation again for another 38 years. From the above calculation, the origin
of the temperature obtained for the ONAN type of cooler in block 3 is 0.71 p.u/day and in block 4 it is 0.70 p.u/day.
While the ONAF type of cooler in block 3 is 0.004 p.u/day and in block 4 it is 0.005 p.u/day. This is in accordance
with the regulation SPLN50/1982 regarding transformer life shrinkage.
Keywords: electric power system; transformer; loading effect;

Introduction
The rapid development of electricity demand at this time must be followed by optimization of electrical power
system equipment so that electrical energy can continue to be distributed continuously and uninterruptedly to electricity
consumers(Pandapotan & Warman, 2016).One of the most important pieces of equipment in the distribution of electric
power is the power transformer. The function of this power transformer is to transform the voltage according to the
needs of the load (Sulasno, 2001).
The transformer is a very important component in the electric power system, because it is used as a voltage adjuster
for the load being served. Therefore, the quality of the transformer must be maintained so that it can last a long time
(Solikhudin, 2010).Many things affect the decline in age, such as the temperature of the transformer and the temperature
around the transformer, the worst loading occurs at the peak of 100% with a relatively low average life expectancy. With
the increase in the load factor and ambient temperature, the aging rate of the transformer increases and the life of the
transformer decreases with the operation of the transformer(Andika et al., 2018).
PT. PJB UBJ O&M PLMG Arun is a power plant with a capacity of 184 MW and supplies electrical power in the city
of lhokseumawe and its surroundings. Meanwhile, the increasing use of electrical power is increasing so that the effect of
loading the power transformer is also a problem during the period of using the transformer (Sigit et al., 2011).

Literature Review
Transformer is an electrical equipment that is included in the classification of electric machines and serves to
distribute electrical power from high voltage to low voltage or vice versa, with the same frequency(Petra, 2017). In
operation, power transformers are generally grounded at the neutral point, according to the need for a safety or
protection system(Situmorang, 2011). For example, a 150/70 kV transformer is earthed directly on the neutral side of 150
kV, and a 70/20 kV transformer is earthed with a resistance on the neutral side of 20 kV. The basic theory of the
transformer is "If there is alternating electric current flowing through the iron core, the iron core will turn large and if the
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Journal of Renewable Energy, Electrical, and Computer Engineering, 1 (2) (2021) 79-84
magnet is surrounded by windings then at both ends of the winding there will be voltage. around the magnet, so that an
electromotive force (EMF) will arise(Bambang N & others, 2020).
Transformer oil is one of the liquid insulating materials used as insulation and coolant in transformers. As part of
the insulating material, oil must have the ability to withstand breakdown voltages, while as a coolant, transformer oil
must be considered capable of handling the heat generated, so with these two capabilities, the oil is expected to be able
to protect the transformer from interference (Putra & Murdiya, 2017).
Table 1. Transformer cooling type (Efendi, 2018)
Media
No Cooling System Type
Inside the Transformer
Outside the Transformer
Natural Circulation Forced Circulation Natural Circulation Forced Circulation
1
AN
Air
2
AF
Air
3
ONAN
Oil
Air
4
ONAF
Oil
Air
5
OFAN
Oil
Air
6
OFAF
Oil
Air
7
OFWF
Oil
Air
8
ONAN/ ONAF
Combination3 and 4
9
ONAN/ OFAN
Combination3 and 5
10
ONAN/ OFAF
Combination3 and 6
11
ONAN/ OFWF
Combination3 and 7
The IEC specifies a transformer life of 20 years or 7300 days, so the normal life loss is 0.0137% per day. Shrinkage
due to hot temperatures can be seen in table 2.

00C

80
0.125

∆1 day

Table 2. Transformer cooling type(Sulasno, 2001)
92
98
104
110
116 122
0.5
1
2
4
8
16

86
0.25

128
32

134
64

140
128

Materials &Methods
This study discusses the effect of loading and environmental temperature on shrinkage of 36/60 MVA power
transformers block 3 and block 4 conducted at PT. PJB UBJ O&M PLTMG ArunLhokseumawe, Nangroe Aceh
Darussalam.This research was conducted by direct observation to the field and the data obtained were in the form of
observational data on transformers which became the object of research as well as observations of the temperature
around the observation location. This study also uses quantitative data, namely data in the form of numbers such as
transformer loading data for 24 hours.
For certain rated power conditions: Natural oil circulation Increase in average coil temperature (measured by
resistance) = 600C.Top oil temperature rise (∆θ𝑤𝑜 ) = 550C.The increase in the average temperature of the oil (∆θ𝑏 )= 400C.
The difference between the average temperature rises of the coil and the average temperature rise of the oil (∆θ𝑤𝑜 )= 210C.
(Source: PT PJB UBJ O&M PLTMG Arun, 2019).
Hot spot temperature rise ((∆θ𝑐𝑟 ) is arranged as follows(Syahputri Marantika, 2016)(Siahaan, 2018)(Perera et al.,
2001) :
a.

1+𝑑𝐾 2

∆θ𝑏 = ∆θ𝑏𝑟 [
Information :

b.

(1)

∆θ𝑐𝑟 = ∆θ𝑏 + 1,1 ∆θ𝑤𝑜

Top oil temperature rise

1+𝑑

d
x
x
x
∆θ𝑏𝑟
K

𝑥

(2)

]

= high ratio
= constant
= 0,9 (ONAN and ONAF)*
= 1,0 (OFAF and OFWF)*
= suhu
= load factor (load supply/load rating)

Hot spot temperature rise
(3)

θ𝑐 = θ𝑎 + ∆θ𝑜𝑛 + ∆θ𝑡𝑑
Information:

= ambient temperature
= increase in top oil temperature
= temperature difference between hot spots and top oil

θ𝑎
∆θ𝑜𝑛
∆θ𝑡𝑑

1+𝑑𝐾 2

∆θ𝑐 = ∆θ𝑏𝑟 [

1+𝑑

] + (∆θ𝑐𝑟 − ∆θ𝑏𝑟 ) 𝐾 2𝑦
80

(4)

Journal of Renewable Energy, Electrical, and Computer Engineering, 1 (2) (2021) 79-84
Information:

c.

∆θ𝑐𝑟
y
y
y
∆θ𝑏𝑟 r

= hot spot temperature rise
= constant
= 0,8 (ONAN and ONAF)
= 0,9 (OFAF and OFWF)
= increase in top oil temperature

Counting aging
t2

h

∫t1 V dt = 3 {V𝑜 + V𝑛 + 4 (V𝑜𝑑𝑑 ) + 2 (V𝑒𝑣𝑒𝑛 )} =

h
3

{2V𝑛 + 4 (V𝑜𝑑𝑑 ) + 2 (V𝑒𝑣𝑒𝑛 )} (5)

Characteristic curve V, V0 = Vn
Information :
h
=constant (1)
T
= time
V𝑜𝑑𝑑 , V𝑒𝑣𝑒𝑛 = relative thermal aging rate

Results and Discussion
Calculations For Constant Load
Calculations are carried out to obtain the effect of various kinds of loading on the power transformer. Then the
magnitude of the load is made constant which can be seen in the following table.
Table 3. Types of Loading
Transformer Load
100
90
80

No
1
2
3

After calculating using the existing equations, it can be seen the value of the life loss on the power transformer and
the remaining operating life based on each loading percentage can be seen in Table 4below:

No
1
2
3

Table 4. Shrinkage and remaining life of transformers of various kinds
Load
Loss of Age (p.u/day)
Age (Years)
100
2.52
10
90
1.44
18
80
0.67
38

Effect of Ambient Temperature

No
1
2
3
4
5
6
7
8
9
10
11
12
13

Table 5. Effect of Ambient Temperature on Constant Load
Life Loss (p.u/day) at Stable Load
Suhu (0C)
80%
90%
20
0.26
0.57
21
0.30
0.64
22
0.33
0.72
23
0.37
0.81
24
0.42
0.91
25
0.47
1.02
26
0.53
1.15
27
0.59
1.29
28
0.66
1.45
29
0.74
1.62
30
0.84
1.82
31
0.94
2.04
32
1.05
2.29

100%
1.00
1.12
1.26
1.41
1.59
1.78
2.00
2.25
2.52
2.83
3.18
3.56
4.00

The calculation results can be seen in table 5 above, the temperature change from the lowest to the highest is namely
200C to 320C makes the age loss at each load change. For loading of 80% the life shrinkage on the transformer is at 0.26
p.u/day to 1.05 p.u/day. And for loading of 90% the life shrinkage on the transformer is at 0.57 p.u/day to 2.29 p.u/day.
While for loading of 100% the life shrinkage on the transformer is at 1.00 p.u/day to 4.00 p.u/day. From the results of the
analysis, it can be explained that the difference in age loss for each load is the same because the transformer has a
constant load. So based on the SPLN 50/1982 regulation regarding the life loss of the transformer in accordance with the
calculation results obtained.

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Journal of Renewable Energy, Electrical, and Computer Engineering, 1 (2) (2021) 79-84

Figure 1. Effect of Ambient Temperature on Constant Load
Based on Figure 1.above, it is explained that the effect of ambient temperature greatly affects a constant load. It can
be seen in Figure 4.1 that the greater the temperature given to the power transformer, the life loss obtained will be even
greater by being given a high load, this can be proven at a high load, namely 100% of the resulting life loss is very large,
which is 4 pu/days given the high temperature of the transformer, which is 320C.

Calculations for Power Transformer Loading
The magnitude of the rated power of the power transformer at PT. PJB UBJ O&M PLTMG ArunLhokseumawe,
Nangroe Aceh Darussalam used is 32/60 MVA (ONAN/ONAF). The power transformer load for block 3 on 20
November 2019 at 19:00 is 34.88 MW 5.76 MVAR, while the power transformer load for block 4 on 20 November 2019 at
19:00 is 34.30 MV 7, 78 MVARs.

Figure 2. Calculation of thermal aging block 3 at each hour (ONAN)
Figure 2.above is the calculation of thermal aging in block 3 every hour on the ONAN cooling system. from the
picture it can be explained that at 19.00 hours has the highest life loss in every analysis and calculation carried out this is
because the value of MW and MVAR in the power transformer in the ONAN cooling system is higher at 19.00 so that the
resulting life loss is greater at 19.00 is 13.97 years.

Figure 3. Calculation of thermal aging block 4 at each hour (ONAN)
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Journal of Renewable Energy, Electrical, and Computer Engineering, 1 (2) (2021) 79-84
Figure 3.above is the calculation of thermal aging in block 4 each hour in the ONAN cooling system. From the
picture above, it can be explained that at 19:00 hours it has the highest life loss, because the MW and MVAR values in the
power transformer in the ONAN cooling system are higher at 19:00 so the resulting life loss is greater at 19 hours. :00 of
13.05 years.

Figure 4. Calculation of thermal aging block 3 at each hour (ONAF)
Figure 4.above is the calculation of thermal aging in block 3 at each hour in the ONAF cooling system. From the
picture above, it can be explained that at 19:00, the age loss is the highest in every analysis and calculation carried out.
This is because the value of MW and MVAR in the power transformer in the ONAF cooling system is higher at 19:00 so
that the resulting life loss is greater at 19:00 by 0.033 years.

Figure 5. Calculation of thermal aging block 4 at each hour (ONAF)
Figure 5.above is the calculation of thermal aging in block 3 at each hour in the ONAF cooling system. From the
figure, it can be explained that at 19:00, the age loss is the highest in every analysis and calculation carried out. This is
because the value of MW and MVAR in the power transformer in the ONAF cooling system is higher at 19:00 so that the
resulting life loss is greater at 19:00 by 0.032 years.
From the analysis, the age loss caused by ambient temperature was obtained for the ONAN type of cooler in block 3
of 0.71 p.u/day and in block 4 of 0.70 p.u/day. While the ONAF type of cooler in block 3 is 0.004 p.u/day and in block 4
it is 0.005 p.u/day.

Conclusions
The conclusions that the author can draw from the research that has been done based on the results of calculations
and analyzes carried out are as follows:
1. The effect of temperature on the calculation of the age loss is every increase in temperature starting from the
lowest temperature of 200C to the highest temperature of 320C in Indonesia, at each load of 80%, 90% and 100%, a
very rapid increase in age loss is obtained, namely for a load of 80 % from the lowest 0.26 to the highest 1.05
pu/day and for the load 90% from the lowest 0.57 to the highest 2.29 pu/day and for the load 100% from the
lowest 1.00 to the highest 4.00 pu/ day.
2. From the calculation results at 80%, 90% and 100% constant loading, the age loss value is obtained, respectively,
namely 0.67 p.u/day; 1.44 p.u/day and 2.52 p.u/day and for the remaining life of the power transformer,
respectively, namely 38 years, 18 years and 10 years.
3. The transformer life loss value is based on loading data on November 20, 2019, namely the ONAN type cooling
network in block 3 of 0.71 pu/day and in block 4 of 0.70 pu/day while on the ONAF type cooling network in
block 3 of 0.004 pu/day and in block 4 of 0.005 pu/day. This is in accordance with the regulation SPLN50/1982
regarding transformer life shrinkage.
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Journal of Renewable Energy, Electrical, and Computer Engineering, 1 (2) (2021) 79-84

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