EUROPEAN INTERNATIONAL JOURNAL OF MULTIDISCIPLINARY RESEARCH
AND MANAGEMENT STUDIES
ISSN: 2750-8587
VOLUME04 ISSUE11
99
CALCULATION OF ELECTRICITY LOSSES IN RURAL POWER TRANSMISSION LINES WITH
6-10 KV VOLTAGE
Isakov A.J.
Doctor of Technical Sciences, Dean of Tashkent Institute of Irrigation and Agricultural Mechanization
Engineers” National
Research university, Uzbekistan
Khojayorov F.E.
PhD student of Tashkent state technical university, Uzbekistan
Saidxodjaev A.G.
Doctor of Technical Sciences, Professor of Tashkent state technical university, Uzbekistan, Uzbekistan
AB O U T ART I CL E
Key words:
Electricity losses, power
transmission lines, rural power supply, SAIDI,
SAIFI, reliability parameters, energy loss
modeling, step-down transformer, Qibray
substation, external factors.
Received:
13.11.2024
Accepted
: 18.11.2024
Published
: 23.11.2024
Abstract:
This study presents a detailed analysis
of electricity losses in rural power transmission
lines operating at 6-10 kV, using SAIDI and SAIFI
reliability indices for post-implementation
assessments. To proactively evaluate operational
efficiency, we model energy losses in the system’s
components, including substations, overhead
lines, cable lines, and step-down transformers.
The Qibray 35/6 kV substation is used as a case
study for calculating these losses. Our findings
highlight that additional losses are notably higher
than calculated losses, emphasizing the
importance of external factors in loss modeling.
This comprehensive approach offers insights into
enhancing system reliability and performance for
rural power distribution systems.
INTRODUCTION
coefficients requires a time interval of several months or even years after the system has been launched
[1,2]. However, to assess the operational efficiency of the power supply system in advance, it is
necessary to model the energy losses and evaluate these losses based on the developed model. The
higher the energy losses, the more the technical parameters of the equipment used in the power supply
VOLUME04 ISSUE11
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Pages: 99-106
EUROPEAN INTERNATIONAL JOURNAL OF MULTIDISCIPLINARY RESEARCH
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ISSN: 2750-8587
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system deteriorate, which, in turn, shortens their operational lifespan [3]. Based on this issue, this
section of the dissertation examines the problem of modeling electricity losses in the research object's
power supply system.
Figure 1. Schematic diagram of the 6 kV rural power supply system
It is known that the object of the study is supplied with electricity based on the scheme shown in Figure
1. Initially, electricity is transmitted to consumers through 6/0.4 kV transformers via substation feeders
and through overhead and cable lines. Based on this setup, electricity losses are calculated by dividing
the losses into the following parts [4]:
1.
Determining the electricity losses at the 35/6 kV substation
2.
Calculating electricity losses in the 6/10 kV overhead lines
3.
Calculating electricity losses in the 6/10 kV cable lines
4.
Calculating electricity losses in the 6/10/0.4 kV step-down transformers
5.
Calculating additional electricity losses in the 6/10 kV power supply system
Electricity losses for each stage in the research object are determined in three steps. Initially, the
electricity losses at each stage, along with the energy balance, allow for calculating the total electricity
losses as follows [5]:
∆𝑊 = 𝑊
𝑛
– 𝑊
𝑛+1
(1)
where:
∆𝑊
–
Total electricity loss
𝑊
𝑛
–
n
- Meter indicator
𝑊
𝑛+1
- Meter indicator
Substation
Electric
transmission line
6 kV
6 kV
0,4 kV
EUROPEAN INTERNATIONAL JOURNAL OF MULTIDISCIPLINARY RESEARCH
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ISSN: 2750-8587
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In the next stage, calculated electricity losses are determined using specific functional formulas. In the
final stage, an energy loss balance is created, and the value of additional electricity losses is determined
as follows:
∆𝑊
қ
= ∆𝑊– 𝑊
ҳ
(1)
where,
∆𝑊
ҳ
–
Electricity loss calculated based on the method of computational formulas.
Calculation of electricity losses (EE) is carried out based on the single-line diagram of the 35/6 kV
substation, by calculating EE losses in transformers, short transmission lines, switching devices,
electricity meters, and protective devices at the substation [6].
METHODS
To calculate electricity losses in rural 6-10 kV power transmission lines, a systematic modeling
approach was employed. The study segmented the power system into its primary components:
substations, overhead lines, cable lines, and step-down transformers. Losses at each stage were
calculated through theoretical formulas and operational data analysis. The methodology incorporated
the evaluation of idle and short-circuit power losses, factoring in external influences such as load
variation and environmental conditions. For substations, calculations were based on parameters like
power consumption in idle and short-circuit modes, using data from the Qibray 35/6 kV substation as
a case study. Overhead and cable line losses were computed using resistance, load, and line length data.
Transformer losses were assessed with detailed load curves and equipment specifications. Additionally,
an energy balance analysis was conducted to determine total and additional losses, enabling the
identification of discrepancies due to external factors. This comprehensive approach ensured accurate
modeling and evaluation of electricity losses in rural distribution systems.
RESULTS AND DISSCUSSION
Determining electricity losses at the 35/6 kV substation. The "Qibray" 35/6 kV substation in the
research object is equipped with a 4000/35 TMN transformer, manufactured in 1982. The main
parameters of the installed transformer are provided in Table 2.3.
Table 1.
Parameters of the Main Step-Down Transformer of the Qibray 6/35 kV Substation
EUROPEAN INTERNATIONAL JOURNAL OF MULTIDISCIPLINARY RESEARCH
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Types
S
кВА
𝑈
н
, кВ
Connec
tion
diagram
∆𝑃
, кВт
𝑈
қ.т
,
%
𝐼
салт
ТМН
4000/35
ЮК
ПК
Y/∆
-11
c
алт
қ.т.
7.5
0.00
3
4000
3
5
6
5,
6
3
3,5
It is known that the main electricity losses at the substation occur in the main step-down
transformer. Therefore, the annual energy loss is calculated as follows [7]:
∆𝑊
пс
= ∑ 𝑛
𝑖
∙ 𝑃
салт
∙ Т
𝑖
+ ∑(
1
𝑛
∙ 𝑘
ю.ю
2
∙ 𝑃
қ.ю
′
∙ 𝑇
𝑖
+
1
𝑛
∙ 𝑘
ю.п
2
∙ 𝑃
қ.п
′
∙ 𝑇
𝑖
)
(2)
where:
n
–
Number of elements
𝑃
салт
–
Power consumption in idle mode
Т –
Operating time.
к
ю
- Load factor (HL
–
high voltage, LL
–
low voltage)
𝑃
қ
′
–
Power consumption in short-circuit mode (SC-HV
–
high voltage, SC-LV
–
low voltage)
(
1) The coefficients and unknown terms in the formula are determined as follows:
1.
Determining active power losses in idle mode.
It is known that active power loss in idle
mode is determined as follows [10]:
𝑃
салт
= ∆𝑃
салт
+ к
𝑢
∙ 𝑄
салт
(3)
In that case:
к
𝑢
−
Power loss variation coefficient, which characterizes the relationship between
reactive power consumption and active power consumption in idle mode. Considering that in idle mode
𝑄
салт
=
𝐼
𝑐
;%
100
𝑆
ном.т
expression (3) takes the following form:
EUROPEAN INTERNATIONAL JOURNAL OF MULTIDISCIPLINARY RESEARCH
AND MANAGEMENT STUDIES
ISSN: 2750-8587
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𝑃
салт
= ∆𝑃
салт
+ к
𝑢
∙
𝐼
𝑐
;%
100
𝑆
ном.т
(4)
2.
Determining active power loss in short-circuit mode.
To determine active power loss in
short-circuit mode, reactive power variation is also considered, as was done for active power loss in
idle mode, and is calculated as follows [86]:
𝑃
қ
′
= 𝑃
қ
+ к
𝑢
∙ 𝑄
қ
(5)
Here, considering that the reactive power loss in short-circuit mode
𝑄
қ
=
𝑈
қ
%
100
∙ 𝑆
ном.т
expression (5)
changes as follows:
𝑃
қ
′
= 𝑃
қ
+ к
𝑢
∙
𝑈
қ
%
100
∙ 𝑆
ном.т
(6)
Calculation of electricity losses in 6/10 kV overhead and cable transmission lines.
The
research object consists of overhead and cable lines. The total annual electricity losses in the overhead
transmission lines are determined as follows [87,88].
∆𝑊
ҳл
=
𝑃
ҳл
2
+𝑄
ҳл
2
10
3
∙𝑈
ҳл
2
∙ 𝑟
𝑜
∙ 𝐿
ҳл
+ ∆𝑃
салт.ўз
∙ 𝐿
ҳл
∙ Т
(7)
where:
𝐿
ҳл
- Length of overhead lines
𝑟
𝑜
- Specific active resistance of overhead lines.
𝑃
ҳл
ва 𝑄
ҳл
, Т
–
Active and reactive power flowing over a time interval.
𝑈
ҳл
–
the time interval is assumed to be 0.5 hours.
𝑃
сол.из
−
Power loss in the insulator is calculated and determined by the following formula [8,9]:
∆𝑃
𝑐ол.из
=
1000∙𝑃
𝑜
365∙24
(8)
where:
𝑃
𝑜
–
taken as 0.011 kW/km for the 6 kV line, it estimates the power loss per unit distance of
the insulator.
Electricity losses in cable lines are determined using the following formula [91]:
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∆𝑊
А
= 3К
э
∙ 𝑅
Σ
𝑡(𝐼
мин
2
+ (𝐼
макс
2
− 𝐼
мин
2
)𝛽) ∙ 10
−3
(9)
where,
𝑅
Σ
–
Active resistance of the transmission line.
К
э
–
Equivalence coefficient of the distribution network resistance. This coefficient is determined
based on the graph.
𝑡
- Calculation period (excluding line outage time), in hours;
𝐼
мин
ва
𝐼
макс
- maximum and minimum load values from annual load graphs taken on a daily basis, in
amperes (A);
𝛽
–
form factor.
Calculation of electricity losses in 6/0.4 kV step-down transformers. In calculating electricity losses in
6/0.4 kV power transformers, primary data such as the transformer's type, capacity, rated current, idle
and short-circuit losses (from specification data), operating time, and average and maximum current
values from the load curves are used. Based on this primary data, electricity losses in the 6/0.4 kV
transformer are determined using the following formula [11,12]:
∆𝑊 = ∆𝑃
𝑐алт.𝑖
𝑡 + ∆𝑃
қ.т.𝑖
𝜏
2
к
ю
2
(10)
where
𝑡
- Operating hours of the transformer;
𝜏
- time of maximum losses (the conditional time during which losses in the active resistance of the
network element under constant maximum load are equal to the energy losses in the same element
calculated over the actual load schedule in the time interval), in hours;
∆𝑃
𝑐алт.𝑖
,
∆𝑃
қ.т.𝑖
- power losses in idle and short-circuit modes, in kW;
к
ю
- annual maximum load factor of the transformer, which is calculated as follows [13,14]:
к
ю
=
𝐼
𝑐р.макс
𝐼
н.𝑖
(11)
where,
𝐼
𝑐р.макс
–
Average maximum current value of the transformer's daily load graph, in amperes
(A);
𝐼
н.𝑖
- Rated current of the transformer, in amperes (A);
EUROPEAN INTERNATIONAL JOURNAL OF MULTIDISCIPLINARY RESEARCH
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Considering the time of maximum load, the time of maximum losses is determined as follows [15,16]:
𝜏 = (0,124 +
𝑇
10
4
)
2
∙ 8760
(12)
Calculation of additional electricity losses in the 6/10 kV power supply system. Based on the provided
data of the research object (see Section 1.2 of the dissertation), the losses outlined in the previous
subsections are calculated to identify additional losses in the research object. By determining the
difference relative to the total losses, additional electricity losses in the 6/10 kV power supply system
are estimated. The calculation results are presented in Table 2.
Table 2. Electricity loss calculation table for the research object
№
Date
Total EE losses
(
млн. кВт ∙ соат
)
Calculated EE
losses
млн. кВт ∙ соат
Additional
EE losses
млн. кВт
∙ соат
1
2021
99,2
22,4
79,8
2
2022
104,5
82,1
3
2023
93,54
71,14
The results presented in Table 2.2 indicate that additional losses are significantly higher compared to
the calculated losses, highlighting the need to consider external factors in modeling electricity losses.
Therefore, in the next subsection of the dissertation, electricity loss modeling was carried out, taking
into account additional electricity losses.
CONCLUSION
The study reveals that the primary sources of electricity losses in rural 6-10 kV power transmission
systems stem from various system components, particularly at substations and transformers.
Calculations conducted for the Qibray 35/6 kV substation indicate significant additional losses beyond
theoretical estimates, primarily due to external factors such as environmental conditions and
equipment wear. These findings underscore the need for comprehensive modeling that integrates both
EUROPEAN INTERNATIONAL JOURNAL OF MULTIDISCIPLINARY RESEARCH
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inherent system parameters and external influences. Future research should focus on developing
adaptive modeling techniques to predict and mitigate losses effectively, ensuring greater operational
efficiency and longevity of rural power supply infrastructure.
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