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Supplier performance evaluation for 500 kV main transformer
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3rd International Conference on Green Energy and Sustainable Development
IOP Conf. Series: Earth and Environmental Science 651 (2021) 022020
IOP Publishing
doi:10.1088/1755-1315/651/2/022020
1
Supplier performance evaluation for 500 kV main
transformer
Yinghan Jiang 1, Litong Dong 1, Yinghua Chen 1, Yanqin Ge 1, Mingxue Wang 2,
Jinliang Zhang 2, *
1 Economics and Technology Research Institute, State Grid Jibei Electric Power Co.,
Ltd., Beijing 100038, China
2 North China Electric Power University, Beijing 102206, China
*Corresponding author e-mail: zhangjinliang@ncepu.edu.cn
Abstract. As an important state-owned energy backbone enterprise related to national
energy security and the lifeline of national economy, power grid enterprises are
responsible for ensuring the quality and safety of equipment and promoting the
development of equipment quality. Therefore, continuously improving the quality
evaluation of main transformer equipment is very important to improve the quality of
power grid main transformer equipment. This paper first constructs the main
transformer equipment quality evaluation index system from equipment procurement,
equipment installation, equipment use and equipment decommissioning and scrapping;
on this basis, the scoring method of each evaluation index is given, and the final main
transformer equipment quality evaluation score is calculated by combining subjective
and objective weight determination method; Finally, according to the evaluation of
500kV main transformer equipment of provincial power grid company price score, to
evaluate the performance of equipment quality provided by suppliers.
Keywords: provincial power grid enterprise; main transformer equipment quality;
supplier; performance evaluation.
1. Introduction
With the people's increasing demand for high-quality products, China's comprehensive implementation
of the quality strategy. As the largest state-owned energy backbone enterprise in the world, power grid
enterprises have been committed to continuously improving the overall and systematic work of quality
management. Power grid main transformer equipment is an important material basis for power
construction and safe and stable operation of the system, and an important guarantee for the smooth
development of engineering construction and safe and reliable operation of power grid. Therefore, in
the procurement process of main transformer equipment, the quality of main transformer equipment
should be continuously regarded as the key assessment object of supplier performance evaluation, so as
to ensure the quality of main transformer equipment, which is very important to improve the overall
equipment quality management level of power grid enterprises and implement the "rejuvenating power
grid with quality".
3rd International Conference on Green Energy and Sustainable Development
IOP Conf. Series: Earth and Environmental Science 651 (2021) 022020
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doi:10.1088/1755-1315/651/2/022020
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At present, domestic and foreign scholars have carried out relevant research on the evaluation of
power grid main transformer equipment suppliers. Sun Chaoyuan and Peng Qiyuan used
multidimensional grey comprehensive evaluation method to evaluate equipment suppliers from four
aspects of price, quality, delivery lead time and service level [1]. Dou Peng et al. Put forward the defect,
fault evaluation calculation method and nonlinear life evaluation method to eliminate the influence of
factors such as operation period and operation year, and build the product quality evaluation model of
transformer manufacturers based on this method [2]. Chen Meng constructs an evaluation index system
based on the supplier's enterprise environment, internal situation, service ability, delivery ability and
response ability to evaluate the comprehensive strength of equipment suppliers [3]. Li Yiwen designs a
supplier performance evaluation and risk early warning scheme covering the whole life cycle of assets
from the perspectives of integrity, quality and service, so as to provide quantitative reference for power
grid companies to select the best suppliers efficiently. According to the equipment life cycle
management and equipment quality problems, Jin Yongchuan constructed the power equipment quality
event life cycle link matrix [4]. Wu Wenbo conducts a comprehensive evaluation of power equipment
by modeling and quantifying the five dimensions of qualification performance, performance, economic
life, equipment quality and comprehensive credit [5]. Kiritsis uses ontology based technology to manage
the life cycle of equipment assets [6]. Raghavan et al. Proposed that the asset life cycle model combined
with reliability can achieve the level of equipment quality and solve the problem of low efficiency [7].
Kilsby and remenyte proposed to use life cycle cost to analyze and evaluate the asset management
strategy of overhead line equipment [8]. Bagdadee et al. Proposed using wireless sensor network model
to improve the quality of power grid equipment [9]. Gandomand et al [10]. Used flexible AC
transmission system to improve equipment quality [11].
2. Main transformer equipment quality evaluation index system
2.1. Determination of evaluation index weight
Due to the different importance of different indicators, it is necessary to give reasonable weight to each
evaluation index to improve the rationality of the evaluation results. In order to avoid the subjective or
objective weight of each index, this paper chooses the optimal combination weight method based on the
combination of subjective and objective weights to calculate the weight of each index. The subjective
weighting method and the objective weighting method select AHP and entropy method respectively,
and finally calculate the weight of each index through the optimal combination weight method.
(1) Analytic hierarchy process
Table 1. Main transformer equipment quality evaluation index based on life cycle
Target layer
Primary
indicators
Secondary
indicators
Third level
index
Standard
score
Calculation method or scoring rules
Quality evaluation
index of power grid
main transformer
equipment
Equipment
procurement
stage
Equipment
manufacturing
supervision
Key points of
quality
management
witness in
equipment
manufacturing
process
10score
In case of incomplete or wrong key points
in the manufacturing supervision task such
as manufacturing process and process, 2
points will be deducted for each case, and
the maximum 10 points will be deducted.
Factory test
Equipment
factory test
pass ability
10score
No point will be deducted if the factory
test passes once; 5 points will be deducted
if the delivery test
fails to pass the factory
test once and the retest after simple repair
does not affect the delivery date; 10 points
will be deducted if the factory test fails to
pass once and needs to be repaired for a
long time or fails to pass multiple retests.
3rd International Conference on Green Energy and Sustainable Development
IOP Conf. Series: Earth and Environmental Science 651 (2021) 022020
IOP Publishing
doi:10.1088/1755-1315/651/2/022020
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Equipment
installation
stage
Installation
process
Equipment
installation
process
10score
2 points will be deducted for each piece of
equipment in case of oil leakage (gas)
leakage; 2 points will be deducted for each
non-conforming part due to lack of
equipment installation and nonstandard
bolt installation; 2 points will be deducted
for each place without gasket installation
and obvious gap between equipment base
and foundation, with 10 points at most.
Equipment use
stage
Equipment
quality event
Number of
failures or
unplanned
outages caused
by equipment
quality
problems
10score
No point will be deducted for failure or
non-stop, or failure or non-
stop caused by
quality problem; 5 points will be deducted
for fault or non-stop once caused by
equipment quality; 10 points will be
deducted for failure or non-
stop for two or
more times caused by equipment quality.
Annual
familial
defects of
equipment
10score In case of occurrence, the score of this
item is zero
Equipment
operation
economy
Equipment
transportation
and inspection
cost
10score
If the transportation inspection cost is
located in [0, C], no point will be
deducted; if the transportation inspection
cost is located in (C, d), 5 points will be
deducted; if the transportation inspection
cost is located in [D, + ∞], 10 points will
be deducted.
Unplanned
outage loss 10score
If the unplanned outage loss is located in
[0, a], no point will be deducted; if the
unplanned outage loss is located in (a, b),
5 points will be deducted; if the
unplanned
outage loss is located in [b, + ∞], 10
points will be deducted.
Equipment
defects
Equipment
defect level 10score
No points will be deducted for defects not
caused by equipment quality; 5 points will
be deducted for general defects caused by
equipment quality problems; 10 points
will be deducted for serious defects
caused by equipment quality problems.
Equipment
decommissioni
ng / scrapping
stage
Reasons for
decommissionin
g / scrapping
Technical
economy of
equipment
decommissioni
ng / scrapping
10score
10 points will be deducted if the
equipment is decommissioned due to its
own quality problems and can not be
reused; 5 points will be deducted if the
equipment is decommissioned due to its
own quality problems and can be reused;
no points will be deducted for other
reasons of decommissioning.
Determine the evaluation object, construct the judgment matrix of the evaluation index, and establish
the judgment matrix according to the 1-9 scale principle.
Table 2. 1-9 scaling method
Scale
meaning
1
It shows that the two factors are equally important
3
It shows that the former is slightly more important than the latter
5
It shows that the former is more important than the latter
7
It shows that the former is more important than the latter
9
It shows that the former is more important than the latter
3rd International Conference on Green Energy and Sustainable Development
IOP Conf. Series: Earth and Environmental Science 651 (2021) 022020
IOP Publishing
doi:10.1088/1755-1315/651/2/022020
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(2) Check the consistency of judgment matrix
RI
CI
=CR
(1)
Cr is the random consistency ratio of the judgment matrix. When CR < 0.1, the judgment matrix
meets the consistency requirements, otherwise, the judgment matrix needs to be modified until CR <
0.1 is met. RI is the random consistency index, and the specific values are shown in Table 3.
Table 3. RI value table
Order
1
2
3
4
5
6
7
8
9
RI
0
0
0.52
0.89
1.12
1.26
1.36
1.41
1.46
(3) According to the judgment matrix, the eigenvector corresponding to the maximum eigenvalue is
calculated, that is, the weight coefficient of each index.
2.2. Entropy method
Entropy method is to calculate the information entropy of the original data to reflect the impact of
different indicators on the system. The greater the numerical difference of the same index, the greater
the information entropy and the greater the weight, otherwise, the smaller the weight. The specific steps
of entropy method are as follows:
1) Is the entropy value of the jth evaluation index, then
∑
=
−=
n
i
ijijjff
n1
)ln(
ln
1
ε
(2)
Where
j
ε
is the proportion of J index in all time of the j evaluation index at the n time.
2) Suppose that the entropy weight of the j-th evaluation index is as follows:
),
,2,
1(
1
1
nj
n
wn
j
j
j
j⋅
⋅⋅=
−
−
=
∑
=
ε
ε
(3)
2.3. Combination weight
In order to make the evaluation results more realistic, not only the subjective experience but also the
objective situation of the equipment itself should be considered in the weighting process of each index.
Therefore, the combination weighting method of subjective and objective weights is selected in this
paper, and its expression is as follows:
να
αµ
)1( −+=w
(4)
Among them, is the weight calculated by the i-th weighting method, and is the weight calculated by
the j-weighting method. And are the weight coefficients of the i-th weighting method and the j-weighting
method respectively. Finally, the combined weight vector of each index can be determined according to
the value.
2.4. Final score value of main transformer equipment
(1) The revised score based on Wilson confidence interval
Generally speaking, if the number of samples is small, the equipment quality will be low. In the
quality evaluation of main transformer equipment, the evaluation results are beneficial to the suppliers
with less supply, which is unfair to some extent. Therefore, we need to consider the influence of the
number of samples. According to the initial score value of main transformer equipment quality and the
3rd International Conference on Green Energy and Sustainable Development
IOP Conf. Series: Earth and Environmental Science 651 (2021) 022020
IOP Publishing
doi:10.1088/1755-1315/651/2/022020
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number of equipment, the lower limit of Wilson confidence interval of the initial score of main
transformer equipment is calculated, and the lower limit value is taken as the revised score value of main
transformer equipment quality rating. The modified score value is calculated as follows.
22
2
2
(1 )
24
1
down
z PP z
Pz
n nn
Pz
n
−
+− +
=
+
(5)
Among them:
P—initial quality score of main transformer equipment;
N—the number of samples;
Z—represents the Z statistical constant with the corresponding confidence level of 1 - α (the
confidence level is usually taken as 95%, and the Z statistical constant is 1.96);
Pdown—lower limit of Wilson confidence interval of initial score of main transformer equipment
quality.
(2) Initial rating principle
According to Wilson's confidence interval correction score value, it is divided into different grades
from high to low: if it is divided into 5 levels, it is a, B, C, D, e, accounting for 10%, 20%, 40%, 20%,
10%; if it is divided into 4 levels, it is a, B, C, D, accounting for 30%, 40%, 20%, 10%; if it is divided
into 3 levels, it is a, B, C, accounting for 30%, 40%, 30%; if it is divided into 2, it is a Grade B,
accounting for 50% and 50% respectively.
(3) Calculation of main transformer equipment quality score system
According to the correction results of equipment quality rating and the corresponding correction
score value, linear function mapping interpolation is carried out to calculate the equipment quality rating
hundred point system score. The mapping interval of level a is 93-100, that of level B is 85-92, that of
level C is 77-84, that of level D is 69-76, and that of level E is 60-68. The latest interpolation calculation
of linear function mapping is shown in formula (6).
min max min
min
max min
( )( )
downi down
i
down down
P P UU
RU PP
−−
= + −
(6)
Among them:
Pdowi—equipment quality correction score;
Pdownmax-——the maximum value of equipment quality correction score;
Pdownmin—the minimum value of equipment quality correction score;
Umax——the maximum value of the score range of the hundred mark system;
Umin——the minimum value of the score range of the hundred mark system;
Ri—is the score of equipment quality rating system.
2.5. Example analysis
Taking 500kV main transformer as the research object, this paper evaluates the equipment quality of
main transformer equipment suppliers (A B, C, D, F, G main transformer equipment suppliers) of six
provincial power companies in a regional power grid area, so as to determine the supplier level and
make guidance for the performance rating and selection of suppliers in the future. Among them, the data
is from t provincial power company. Six suppliers will provide 106 main transformers for t provincial
power company in 2019. Firstly, the importance of indicators at all levels of the index system is
compared, and the judgment matrix is constructed according to the attention degree of each index in the
region. Then, the maximum eigenvalue and corresponding eigenvector of the judgment matrix are
solved by the square root method. The established judgment matrix is as follows:
Therefore, the comprehensive score of 106 main transformer equipment is calculated, and Wilson
confidence interval score is corrected, and then combined with the quintile method to determine the
3rd International Conference on Green Energy and Sustainable Development
IOP Conf. Series: Earth and Environmental Science 651 (2021) 022020
IOP Publishing
doi:10.1088/1755-1315/651/2/022020
6
supplier level and mine the characteristics of suppliers. The application results show that the evaluation
results are more scientific and the proposed method is reasonable and effective. As a result, the supplier's
equipment classification results are shown in Table 4:
Table 4. Supplier equipment classification
Spplie
Grade A
Grade B
Grade C
Grade D
Grade E
total
Chongqing supplier
3
11
22
8
7
51
Japanese suppliers
2
4
4
2
1
13
Jinan supplier
2
2
4
4
0
12
Shenyang supplier
2
1
3
1
2
9
Changzhou supplier
1
2
6
2
1
12
Baoding supplier
0
2
4
3
0
9
total
10
22
43
20
11
106
The five grades were assigned 5-1 points respectively, and the total scores of 6 suppliers were
calculated, which were 148, 43, 38, 27, 36, 26. The average scores were 2.90, 3.31, 3.17, 3.0, 3.0, 2.89.
Therefore, it can be determined that the grade of six suppliers is about C, but the main transformer
equipment of Japanese suppliers is better, and Baoding is the worst. It is suggested that different
cooperation strategies should be adopted for suppliers with different sub positions and different safety
types. Suppliers in a and B levels can give priority to continue cooperation; suppliers in sub C can
continue to cooperate. It is suggested that differentiated quality sampling and operation inspection
strategies should be formulated for such suppliers to do well in equipment quality inspection and strictly
prevent quality control; for D and e grade suppliers, cooperation should be given priority The supplier
of low-quality equipment needs to re evaluate its qualification, strictly control the equipment quality, or
consider replacing the supplier.
3. Summary
In this paper, based on the provincial power grid main transformer equipment quality, supplier
performance is proposed. Due to the gradual strengthening of power grid safety awareness, in order to
ensure safe operation, the equipment quality should be strictly controlled in the material department.
According to Wilson confidence interval, the final score of main transformer equipment is modified to
divide the equipment grade, and the supplier is judged according to the equipment quality provided by
the supplier, so as to determine the average grade of the equipment provided by the supplier, so as to
provide decision support for the procurement of main transformer equipment in t provincial power grid
in the future.
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IOP Publishing
doi:10.1088/1755-1315/651/2/022020
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