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Research for Shielding Effect of 3-Phase Air-Core
Reactors in Substation by Using Different Materials
Tao Wenbiao1, Wang Jinhao1, Ma Zhenguo1, Duan Weinan2, Wang Wei1
1. State Grid Shanxi Electric Power Research Institute, Taiyuan, Shanxi, P. R. China
2. The University of New South Wales, Sydney, Australia
*twb1989@sina.com
Key words: magnetic field interference; air-core reactor; shielding method; limited element method.
different materials and different laying mode were analyzed.
Typical lines were set up in the model, and the inhibitory
effects of different modes on the voltage induction of near
lines were also analyzed.
Abstract
To research the magnetic field interference on cables nearby
3-phase air core reactors and the shielding effect of different
materials, this paper analyzed the influence on spatial
magnetic field by using high conductivity materials and high
permeability materials after the basis of three- dimensional
electromagnetic simulation model, and analyzed the causes.
Furthermore, the induced voltage in different shielding
methods is calculated and discussed by using magnetic vector
potential resulted from the finite element method. From the
result, to achieve a satisfying effect, the shields under 3-phase
reactors need connect when using high permeability.
Moreover, a large number of magnetic leakages on the edge
of shield can aggravate the magnetic field interference in
surrounding areas. Therefore, the distribution of onsite cables
in substation need be considerate when using high
permeability.
1
2
Simulation analysis
2.1 The simulation model for three phase reactor
A 3D electromagnetic model of air-core reactor was
established by COMSOL multiphysics software based on real
parameters, as shown in Figure 1. The rated current, rated
voltage and rated inductance value is 2 000A, 36.5kV and
28.26mH respectively.
Air
Introduction
Control room
In recent years, flexible AC transmission has become the key
technology to improve the power quality. As the main
equipment for regulating and stabilizing the load, the air-core
reactor are widely used on flexible AC transmission lines.
However, the working current of large capacity air-core
reactors can reach 2000A~3000A[1]. The magnetic field
becomes strong under the action of large current, which may
cause the serious magnetic field interference to the secondary
equipment in substation[2].
Ground
Three phase reactor
Fig.1 The 3-phase air core reactor in simulation
The magnetic field value at any point in the space is affected
by three-phase reactors. In cylindrical coordinates, the vector
magnetic potential of a space point has only circumferential
components. According to the Maxwell equations, the
magnetic field basic equation of the solution area is as
following.
Aiming at the problem of magnetic field interference by aircore reactors in substation, researchers put forward a variety
of measures to reduce the coupling efficiency of facilities and
magnetic field, such as raising the air-core reactor[3],
adjusting the cable channel[4], transforming the main
grounding grid structure[5] and so on. These methods have
obvious effect in the engineering. But the concrete method
should be designed according to the environment, and they
are not universal[6-7]. In fact, the magnetic interference of
the air-core reactor is mainly reflected in the strong induction
voltage on the nearby lines. Researches in the past focused on
the optimization effect of magnetic field, but ignored the
direct influence on the lines[8-9]. The problem of magnetic
leakage of three phase reactor remains to be further studied.
2Ai
r i 2
+
Ai
A
Ai
− i2 +
= − J i
r i r i
ri
zi 2
（1）
In the equation, Ai is the vector magnetic potential component
under the action of phase i reactor. μ is the permeability of
material. Ji is the current density of phase i reactor. ｒi、zi is
radius coordinate axis and height coordinate axis respectively
in the cylindrical coordinate system with phase i reactor as
the center.
2.3 The magnetic field distribution of three phase reactor
The tetrahedron mesh is used to divide the model into 69140
smallest computing units in COMSOL Multiphysics software,
and the three-dimensional space was calculated and solved by
In this paper, the simulation model of three-phase air-core
reactor was established. The magnetic field changes by using
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frequency-domain solver. The spatial magnetic field
distribution of the three phase air-core reactor is shown in
Figure 2. The strongest magnetic flux area can reach 2000mT
at the center of reactor. The magnetic field lines diffuse from
the center of reactor to the space, which keeps a high
magnetic field in the nearby space. The magnetic field
distribution under reactors 1m is shown in Figure 3. The
magnetic field in the central area of three phase reactor is
strongest, while the magnetic field in other areas far away
from reactor is weaker.
Line 2
Air-core reactor
0.1948
T
0.18T
Line 1
0.16T
0.14T
0.12T
Fig.4 The secondary cable nearby reactors
0.10T
0.08T
0.06T
3
0.04T
0.02T
Discussion
3.1 The effect of shielding on the magnetic field
Aluminum plates and silicon steel sheets are widely used in
various magnetic shielding researches as high conductive
materials and high permeability materials respectively [69,11]. Aluminum plates and silicon steel sheets were set in
the model. The the parameters of two materials are shown in
Table 1.
4.2996
×10-5T
Fig.2 The magnetic field distribution of 3-phase reactors
Tab.1 parameter setting of shielding material
Fig.3 The magnetic field distribution under reactors 1m
l
A
dl
t
Conductivity
ζ（S/m）
Relative
permittivity εγ
Relative
permeability μγ
Aluminum
plates
3.774×107
1
1
Silicon
steel
9.843×10-4
1
7000
Silicon steel sheet is a high permeability material. If we use
the integrated structure to shield, there will be large induction
current inside the shield. Laminated structure of silicon steel
sheets can ensuring the magnetic path and avoiding large
induction current as well. Therefore, the electrical
conductivity of the silicon steel sheet in the material is equal
to the electrical conductivity of the inter stack insulating
material. A 1cm thick shield with a total area of 10×18m2
was set on the ground surface in the model. The magnetic
field distribution under reactors 1m by shielding is shown in
Figure 5.
Many studies have found that the magnetic leakage of large
capacity air-core reactor can directly affect the stable
operation of surrounding lines with forming larger
interference voltage or induced current[2,5,10]. In this paper,
two simulated secondary lines were set under ground 0.8m in
simulation model, as shown in Figure 4. Line 1 under the
reactor is 10×10m2. Line 2 is 46m and is the black solid line
in Figure 4. In the model, the induced voltage ε of line 1 can
be figure out by formula (2). The induction voltages of line 1
and line 2 is calculated to be 24.81V and 11.88V respectively.
=
Materials
23mT
（3）
2
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(a) Aluminum plate shielding
40.5mT
Fig.6 Induced current under different shielding methods
(b) Silicon steel sheet shielding
From the effect of two shielding materials in Figure 6, we can
see that the induced voltage can be significantly reduced with
the increase of shielding area. But when the shielding area
reaches a certain level (such as mode 3), the shielding effect
is no longer significantly improved. In addition, the shielding
effectiveness is not good when three-phase shields of silicon
steel sheet were laid on the bottom of the reactor
independently. However, when the three-phase shields are
connected together as a whole (mode 2), the induction
voltage drops to 1.9V. Although a large number of magnetic
lines can be restrained in the high permeability material, there
will still be a large number of magnetic lines passing through
the edge of the material (edge effect) to cause induction
voltage on the line, as shown in Figure 7(a). But the threephase magnetic field will be brought together in the same
shielding body when the three-phase shields are connected as
a whole. Three-phase magnetic field can offset each other in
the enclosures and the shielding effect obvious, as shown in
Figure 7(b).
Fig.5 The magnetic field distribution under reactors 1m by shielding
Compare with figure 4, due to the induced reverse magnetic
field by aluminum plate, the magnetic field distribution under
the reactor is more uniform and the strongest region
decreased from 35mT to 23mT. But the magnetic field
around the reactor become bigger and the magnetic field
region above the reactor is expanded. In contrast, in the
model of silicon steel sheet shielding, the magnetic field
above the reactor is reduced, because the magnetic field lines
are bound in the bottom of the reactor.
3.2 The influence of shielding on the induced voltage
The areas of different shields were set up and the influence
on the induced voltage of the adjacent lines was studied. The
shielding areas were divided into four kinds.
(1) Mode 1. A 2×2m2 square shield with a thickness of 1cm
was laid on the bottom of each phase reactor, and the three
phase shields were not connected to each other.
(2) Mode 2. Based on mode 1, the gap between the three
phase reactors were connected together to form a 2×13m2
whole.
(3) Mode 3. Based on mode 2, the area of the shield was
expanded to form a 10×18m2 rectangular shield.
(4) Mode 4. Based on mode 3, The area of the shield was
further expanded to form a 15×23m2 rectangular shield.
(a) Edge effect
(b) Magnetic field convergence
Fig.7 The change of magnetic line of force by using silicon-steel sheet
On the contrary, the shielding measures of silicon steel make
the induction voltage of line 2 greater in mode 1 and mode 2,
as shown in Figure 6. Because the edge of shielding in mode
3 and mode 4 is close to line 2, the inducted voltage on line 2
turn stronger as well as the magnetic field around the line 2.
Therefore, although the shielding effect of silicon steel sheet
is better than aluminum plate, it is also affected by the layout
of space. The line located at the edge of silicon steel
shielding body may be subjected to more serious magnetic
field interference.
Induced currents of line 1 and line 2 under different shielding
methods is shown in Figure 6.
4
Conclusion
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1) The high conductivity shielding material represented by
aluminum plate can effectively shield the induced voltage
near the reactor, and shielding effect turns better gradually
with the increase of shielding area. However, when the
shielding area reaches a certain level, the shielding effect is
no longer significantly improved.
2) Three phase Independent laying of silicon steel sheets can
not achieve good shielding effectiveness. It is better to
connect three phase silicon steel sheets as a whole.
3) There is a strong partial magnetic field on the edge of high
permeability material., which may cause more serious
magnetic field interference to the lines in this area.
5
References
[1]
Zhao Xunjun . New design method of sub-synchronous oscillation damping
controller in VSC-MTDC. Technology and Engineering, 2016; 16(30):
243—248.
[2] Wen Caiquan, Song Yongjia, Zhao Shilin, et al. Simulation of
electromagnetic compatibility of air-core reactor in large scale SVC and
measure of reducing induced current in substation grounding grid. Southern
Power System Technology, 2015; 9(9): 76—80.
[3] Zhang Jie, Tan Xiangyu, Wang Ke, et al. Application of distributed fiber
bragg grating sensor system in dry-type air-core reactor. Science
Technology and Engineering, 2015; 15(16): 160—164,180.
[4] [4]Terciyanli A, Ermis M, Gultekin B, et al. EMC considerations in the
design of a unified relocatable SVC for open-cast lignite mining in turkey.
Electromagnetic Compatibility, 2003. EMC'03. 2003 IEEE International
Symposium on. IEEE, 2003; 2: 991—994.
[5] Li Ning, Wen Caiquan, Song Yongjia, et al. Grouding system design to
reduce magnetic interference of air-core reactor in substation. Southern
Power System Technology, 2017; 11(5): 1—5.
[6] Zhang Ning, Li Lin. Research analysis of the optimal inhibition of power
frequency magnetic field of 35 kV air-core reactor. High Voltage
Apparatus, 2015; 51(8): 125—130.
[7] Li Yongmin, Xu Luwen, Yu Jihui, et al. Intensity control of power
frequency magnetic field under 35kV dry-type air-core reactor. Power
System Technology, 2010; 36(12): 2960—2965.
[8] Lv Yiling, Zhang Xiaoming, Chen Guobin, et al. Research on magnetic field
amplification characteristics of magnetic flux concentration structure. Power
Science Technology and Engineering, 2015; 35(35): 6—10.
[9] [9]Lee S Y, Lim Y S, Choi I H, et al. Effective combination of soft
magnetic materials for magnetic shielding[J]. IEEE Transactions on
Magnetics, 2012; 48(11): 4550—4553.
[10] Tong Linghua, Zhen Jianzi. Influence of 35 kV dry-type air-core reactor on
induced current of secondary cable shielding layer. Zhejiang Electric Power,
2008; (5): 54—56.
[11] [12]Morozionkov J, Virbalis J A. Shielding of electric reactor magnetic
field. Elektronika ir Elektrotechnika, 2015; 96(8): 15—18.
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