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8/10/2019 Corona Ring Design of 800kV DC Composite Insulator Based on Computer Analysis
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Corona Ring Design of 800kV DC Composite Insulator Based on Computer Analysis
Wenxia Sima, Kun Wu, Qing Yang, Caixin Sun
Key Laboratory of High Voltage Engineering and Electrical New Technology, Ministry of Education
College of Electrical Engineering, Chongqing University, Chongqing, China
Abstract: This paper presents a 3D electric-field
calculation model of the 800kV DC transmission line
composite insulators based on finite element method.
With this 3D model, this paper introduces the effect ofthe tower, transmission lines and the parameters of the
corona rings on the potential and e-field distribution
along the composite insulators, and optimizes thecorona ring design in order to control the maximum e-
field along the insulator surface and corona ring surface.
Introduction
The e-field distribution around the ultra high voltage
transmission line insulators, under dry conditions isgoverned by the geometry and the capacitance
distribution along the insulator. In the case of ceramicinsulators formed by a string of discs, which have a
large capacitance, the voltage has a graded distribution
along the insulator string. This phenomenon helps to
avoid high electric field strength at or near the ends of
the string. However, in the case of non-ceramic outdoorinsulators, the permittivity of the material and the shapeof the insulator result in a non-uniform potential
distribution along the insulator, which produces the high
e-field strength in the vicinity of both line and ground
ends[1]-[2].
Corona rings are used to improve the performance ofthe insulator in a multiple of ways. They can reduce
corona and the associated audible noise and radio
interference(RI) and television interference (TVI).
Corona rings can adjust the voltage distribution along
the insulator near the ends of the insulator, thereby
reducing the maximum e-field[3]-[4]. More importantly,
they can eliminate corona degradation of non-ceramic
materials. But there are few standards for corona ring
design up to now. The UHV 800kV transmission line
is to be built in China. The composite insulator is
chosen to be the line insulator of this transmission line.Therefore, it is necessary to optimize the corona designof the UHV composite insulator.
Basis of the 3D E-field Calculation Model
There are many factors that influence the e-field
distribution of the transmission line composite
insulators. The most important factors include:
1. Geometry of composite insulator, both weather-shed systems, fiberglass rod and electrodes.
2. Electrical properties of the silicon-rubber and
fiberglass rod material.3. The dimension and position of the corona rings as
well as the attachment method.
4. The geometry and relative positions of theattachment hardware, for example, conductor
bundles, tower and shielding lines.
Each of these factors needs to be taken into accountwhen determining the e-field distribution of composite
insulators. These factors may have more or less effecton the e-field distribution of composite insulators. Fig.1
gives the section planes of the model used in the
simulation. The factors mentioned above are all taken
into consideration.
Fig. 1 The section planes of the model used in the simulations
With a commercial finite element software, COMSOL
Multiphysics, the calculation of the potential and e-fielddistribution along the composite insulator is to solve the
Possions equations in the whole domain as
= Vr0 (1)
The boundary condition between two dielectrics is
1-4244-0547-5/06/$20.00 2006 IEEE
2006 Annual Report Conference on Electrical Insulation and Dielectric Phenomena
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8/10/2019 Corona Ring Design of 800kV DC Composite Insulator Based on Computer Analysis
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8/10/2019 Corona Ring Design of 800kV DC Composite Insulator Based on Computer Analysis
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corona ring are considered, which are the R, r and hshown in Fig.5
Fig.5Corona ring parameters in the model
Fig.6 and Fig.7 present the potential and e-fielddistribution along the composite insulator with and
without corona rings. It can be seen from Fig.6 andFig.7 that the potential and e-field distribution along thecomposite insulator is uniform with the corona rings,
and the maximum fields near both ends are reduced
rapidly.
0 2 4 6 8 100
200
400
600
800
Distance from the energized end fitting [m]
Potential[kV]
With corona rings
Without corona rings
Fig.6 Potential distribution along the composite insulator with and
without corona rings
0 2 4 6 8 100
5
10
15
20
25
Distance from the energized end fitting [m]
Electric
field[kV/cm]
Without corona rings
With corona rings
Fig.7 E-field distribution along the composite insulator with and
without corona rings
The purpose of the corona ring optimization is to reduce
the corona ring size when the maximum e-field on the
insulator surface and the maximum e-field on the corona
ring surface are controlled below 4.5kV/cm (the coronainception e-field strength of the insulator) and 22kV/cm
sepearately (the corona inception e-field strength of the
corona ring).
Fig.7 shows that there are four peak e-field strengths
along the insulator surface. The e-field strength nearenergized end is always larger than that of the ground
end. Therefore, only 3 e-field strengths are considered
in this paper, which are the e-field strength at the joint
of the insulator and the energized electrode, the peak e-field strength along the sheds near the energized end andthe maximum e-field strength on the corona ring of the
energized end.
In order to explore the effect of the three different
parameters, the e-field was computed at different values
of R, r, and h, as shown in Figures 6, 7 and 8. Twoparameters were fixed while the other vary in a practical
range. (O stands for the e-field strength at the
connection of the insulator and the energized electrode, stands for the e-field strength along the sheds near the
energized end and stands for the maximum e-fieldstrength on the corona ring of the energized end)
0.7 0.8 0.9 1 1.1 1.2 1.3 1.40
1
2
3
4
5
6
The corona ring diameter(R) [m]
Electricfie
ld[kV/cm]
Fig.8 The three e-field strengths with variation of R (r=0.4m and
h=0.2m.)
0.2 0.3 0.4 0.50
1
2
3
4
5
6
The semidiameter of the ring tube(r) [m]
Electricfield[kV/cm]
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8/10/2019 Corona Ring Design of 800kV DC Composite Insulator Based on Computer Analysis
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Fig.9 The three e-field values with variation of r. (R=1m and h=0.2m)
Fig.10 The three e-field strengths with variation of h ( r=0.3m and
R=1m)It can be concluded from Fig.8 to Fig.10 that :
1. the e-field strength at the joint of the insulator andthe energized electrode increases with the increaseof R, decreases with the increase of r, increases at
the beginning and then decreases with the increaseof h.
2. the peak e-field strength along the sheds near the
energized end increases with the increase of R. Ithas nothing to do with the other two parameters, r
and h. When R 0.3m, this e-field strength can be
controlled below 4kV/cm.
3. the maximum e-field strength on the corona ring of
the energized end is mainly associated with r. It
increases with the increase of r, and keep at the
same value with the varition of Rand h. When r
0.05m, this e-field strength can be controlled below
20kV/cm.To be uniform with the practical situation, the
parameters R, r and h, utilizing the results above, the
optimal parameters of the corona ring of the 800kVDC transmission line composite insulators are R=0.3m,
r=0.1m, and h=0.08m. From Fig. 11, it can be found
that the maximum electric field on insulator surface is
4.16kV/cm(Fig.3.7) and that on the surface of the
corona ring is 18.4kV/cm .
Fig.11 E-field distribution along the insulator when R=0.4m
r=0.14m and h=0.2m.
Conclusions
1. A 3D potential and e-field calculation model of
800kV DC transmission line composite insulatorsis established in this paper. The calculation results
of the 3D model is more accurcate than that of the
traditional 2D axial symmetry model because there
are many fators affecting the e-field distribtion.2. The e-field distribtion of the 800kV DC
transmission line composite insulators is non-uniform. In the energized side, 20% of the arc
distance sustains about 50% of the applied voltage.
The corona rings can help the e-field distribution
of the composite insulator to be uniform,especially near the ends of the insulator.
3. The parameters of the corana rings play an
important role in the e-field distribution along theinsulator. With the help of the optimizationcalculation in this paper, the optimized corona ring
could ensure the safety requirement of the
electrical performance.
References:
[1] Chen Shuting, Li Rilong. The application of composite
insulators[J]. Insulators and surge arresters, 2004,199(3):8-10.
[2] W. Sima, F. P. Espino-Cortes, Edward A. Chemey et al.
Optimization of corona ring design for long-rod insulators using
FEM based computational analysis[C]. Conference Record of
the 2004 IEEE International Symposium on Electrical
Insulation. Indianapolis, IN USA, 2004,9:19-22
[3] Weiguo Q, Stephen A.S.Electric field and potential distributions
along dry and clean non- ceramic insulators[J]. IEEE CNF,
2001, 10: 437-440
[4] Mao Fenglin, Wang Xuesong. E-field distribution influence of
corona ring on composite insulator[J]. High voltage technique,
2000, 26(4):29-42
Author address: Wenxia Sima, Key Laboratory ofHigh Voltage Engineering and Electrical New
Technology, Ministry of Education College of Electrical
Engineering, Chongqing University, Chongqing, China.
Email: [email protected]
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