Energy and Power Engineering, 2013, 5, 1298-1302
doi:10.4236/epe.2013.54B246 Published Online July 2013 (http://www.scirp.org/journal/epe)
The Ultraviolet Detection of Corona Discharge in Power
Transmission Lines
Lan Chen1, Lin Lin2, Mimi Tian2, Xingming Bian1, Liming Wang1, Zhicheng Guan1
1Graduate School at Shenzhen, Tsinghua University, Shenzhen, China
2Jibei Electric Power Maintence Company, Jibei Electric Power Company, Limited, Beijing, China
Received April, 2013
ABSTRACT
Corona discharge is a common phenomenon in power transmission lines external insulation, and it may cause serious
defect if without effective detection. The ultraviolet (UV) imagery technology has been widely used to detect the corona
discharge in industry in recent years, but some influence factors’ functions are not definite. In this paper, the fracture
aluminum strands which is common in power transmission lines were used as the electrode model while a SuperB ul-
traviolet imager were utilized to detect, the photon count rate was detected with different detect distance, electric field,
aluminum strands length and UV gain were applied. Then the multivariate regression analysis (MRA) was taken to cal-
culate the function between the photon count and the factors.
Keywords: Corona Discharge; Transmission Lines; Defect Detection; UV Imager; Multivariate Regression Analysis
1. Introduction
With the development of Extra High Voltage (EHV) and
Ultra High Voltage (UHV), the electromagnetic envi-
ronment problem caused by corona discharge of conduc-
tor was paid attention increased [1-3]. The corona dis-
charge could generate the negative phenomenon such as
radio interference, audible noise, ozone-forming, elec-
trochemical reaction [4-6]. The detection of the defect of
the corona discharge has been added to the daily inspect
in transmission lines in recently years [7].
The corona discharge in the transmission lines often
occurred at the high voltage terminal of amour clamp,
split clamp, conductor surface and the end of fractured
aluminum strands caused by lightning stroke or conduc-
tor galloping. And the influence of fractured aluminum
strands is extra clear, it not only generate corona dis-
charge by distort the electric field at the end of the
strands, but also make a bad influence on the mechanical
behavior of the conductor, the defect would make serious
harm to transmission security if without fix timely [8].
So it is important to find and fix fractured aluminum
strands at the early stage in transmission lines patrol.
The traditional ovular estimate and infrared thermo-
graphy technology don’t have well effect on the fractured
aluminum strands detection. For the ovular estimate,
people may have different vision disparity and the corona
discharge could be find nearly only in intensity at night
[9]. While the infrared thermograph technology is able to
detect the defect with consecutive electrothermal effect,
but the corona discharge must be serious, so it is not
promptly for detection of little heat at the early corona
stage [10, 11]. So the infrared thermograph technology is
not widely used in the outdoor corona detection in trans-
mission lines.
The ultraviolent imaging technology is able to catch
the specific wavelengths photon of UV signal, and then
combine with the visible light to decide the corona dis-
charge point. And the strength of discharge is judge by
the photon counting rate.
The UV imager was researched and developed to de-
tect the discharge phenomenon by occident at the earliest.
It can find the discharge point with small temperature
rise at the early discharge stage, is currently one of main
methods of discharge detection in the world [12]. From
1980s, the EPRI attempted to utilize the UV imager to
test the discharge in the transmission lines [13-15], and
have got good achievements. In china it is also have con-
vinced performance in actual use.
The ref [16, 17] take the research of corona discharge
performance of insulator at different applied voltage, the
UV imager was used to measure the discharge. In ref
[18], several influence factor of UV imager was studied,
such as photon counting rate, detect distance, discharge
capacity. Refs [19, 20] have discussed the principle of
UV imager, and then the UV imager of SuperB was used
to detect the corona of electrical equipment in the trans-
mis- sion lines. In ref [21], the UV imager was used to
decide the corona inception voltage of the conductor un-

L. CHEN ET AL. 1299
der dry or rainy conditions.
In this paper, the UV imager type of SuperB, which
designed by Ofil company, was used to detect the corona
discharge at the top of fractured aluminum strands. And
the electric field, length of the strand, detection distance
and gain level were researched. Then the MRA was tak-
en to calculate the function between the photon count and
the factors.
2. Introduce of Experiment
2.1. Test System
The experiment was carried out in a shielding hall with a
size of 66 m × 30 m × 18 m, and the test model was
4×LGJ300/40, bundle space was 45 cm, height was 6.8
m, the model picture was showed in Figure 1. And the
temperature was 8.4℃~10.8℃，relative humidity was
35%~43%.
The UV imager with type of DayCor SuperB was
showed in Figure 2. And the 50 Hz source with maxi-
mum of 1000 kV and 1000 kVA was showed in Figure
3.
And the measurement system schematic diagram was
showed in Figure 4.
2.2. Fractured Aluminum Strands Information
The fractured aluminum strands (see Figure 5), was set
at one of the LGJ300/40 conductor, with different length
(see Fi g u r e 6).
Figure 1. Picture of test model.
Figure 2. UV imager of SuperB.
And the different strand length, detection distance, ap-
plied voltage, UV gain level were show in Table 1. The
electric field of the conductor surface (not the top of
strand) was calculated by ANSOFT for applied voltage
as 10.7 kV/cm, 13.6 kV/cm, 16.4 kV/cm, 19.3 kV/cm,
and respectively.
Figure 3. 1000kV transformer.
Figure 4. Measurement system schematic diagram.
Figure 5. The top of the fractured aluminum strands.
Figure 6. Schematic diagram of fractured aluminum
strands.
Table 1. Information of the factor.
Influence factor content
Length of strand (cm)2 4 6 8 10
Applied voltage (kV)150 190 230 270
Detection distance (m)7 9 11 13
UV gain 60 80 100 120

L. CHEN ET AL.
1300
3. Results and Analysis
With the different influence factor applied on the strands,
the corona phenomenon was detected by the UV imager.
Limited by the paper length, one of them was showed in
Figure 7.
We noticed in Figure 7 that the photon counting rate
would increase with the rise of the applied voltage, such
as applied voltage was 150 kV ( with conductor surface
electric field is 10.7 kV/cm) while the photon counting
was 7620, with the voltage increased to 270 kV ( with
field 19.3 kV/cm) the photon counting rise at 22660.
3.1. Influence of Voltage (Electric Field)
With the applied voltage of 150kV, 190kV, 230kV,
270kV, the electric field was 10.7kV/cm, 13.6kV/cm,
16.4kV/cm, 19.3kV/cm, respectively, one part of result
of experiment was show in Figure 8.
(a)10.7 kV/cm (b)13.6 kV/cm
(c)16.4 kV/cm (d) 19.3 kV/cm
Figure 7. Corona discharge at the top of fractured strand
with different voltage applied (length of strand is 10cm,
detection distance is 9 m, UV gain is 100).
11 12 13 14 15 16 17 18 19
10000
15000
20000
25000
30000
35000
40000
45000
Photon counting rate
Electric field of conductor surface （ kV/cm ）
2cm
4cm
6cm
8cm
10cm
UV gain 120
Distance 9m
Figure 8. Influence of electr ic field.
3.2. Influence of Detection Distance
With the different detection distance of 7 m, 9 m, 11 m,
13 m, the results were partly showed in Figure 9.
3.3. Influence of UV Gain
With the different UV gain was set in the experiment, the
results were partly showed in Figure 10. However, the
UV gain character is most related to the signal processing
module of the UV imager designer, so it may different
from other UV imager.
3.4. Influence of Length of the Strand
With the different length of strand applied on the con-
ductor, the results were partly showed in Figure 11.
4. Multivariate Regression Analysis
MRA was developed from one dimension regression
analysis and used to investigate the connection between
dependent variable and several independent variables.
MRA is considered as an effective mathematical method
to solve practical engineering problem.
789 10111213
10000
15000
20000
25000
30000
Photon counting rate
Detection distance （ m ）
2cm
4cm
6cm
8cm
10cm
UV gain 100
Electric field 19.3kV/cm
Figure 9. Influence of detection distance.
60 70 80 90100110120
0
5000
10000
15000
20000
25000
30000
Distance 9m
Electric field 16.4kV/cm
Photon counting rate
UV gain
2cm
4cm
6cm
8cm
10cm
Figure 10. Influence of UV gain.

L. CHEN ET AL. 1301
The multiple regression prediction equation about the
photon counting rate was:
2
012 3 4
/PELK    s (1)
In the equation, electric field was set as E, kV/cm; de-
tection distance was set as L, m; UV gain was set as K;
length of strand was set as s, cm.
And the significance test was taken, including R, F and
T test , showed in Equation (2) ,(3) and (4).
2
11
ˆ
()(
nn
ii
ii
Ryyy

 

2
)y
(2)
2
1
2
1
ˆ ()
~(, 1)
ˆ ()( 1)
n
i
i
n
ii
i
yy m
FF
yy nm







mnm
(3)
2
1
() ~( 1)
ˆ ()( 1)
jj jj
jn
ii
i
bc
T
yy nm






t
nm
L
(4)
The results of MRA and significance test were display
in Table 2.
The result of significance test is well, so the regression
equation about photon counting rate is:
2
5798049.29101230 /
347.7754.4
PE
Ks
 
 (5)
246810
4000
8000
12000
16000
20000
UV gain 100
Distanc e 9m
Photon counting rate
Length of strand （ cm ）
10.7kV/cm
13.6kV/cm
16.4kV/cm
19.3kV/cm
Figure 11. Influence of stran d length.
Table 2 . Mra about photon coun ting rate and signif icance test.
R F T
R F β0 β1 β2 β3 β4
Value 0.934 1080 -57980 49.29 101230 347.7754.4
α --- <0.001 <0.001 <0.001 <0.001 <0.001 <0.001
5. Conclusions
In this work, the fractured aluminum strands was taken
for the test model to research the corona discharge detec-
tion of UV imager. The influence detect distance, electric
field, strands length and UV gain were investigated while
the MRA was utilized to summarize the regression equa-
tion about the photon counting rate. These conclusions
have good contribute to expand UV imaging technology
in practical transmission lines patrol of corona discharge.
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