|
Present-day high-voltage CL: installation and maintenance experience. Part 3
Second part of the article
Table 7. Damage ratios of cable lines with elements distribution in correlation to the amount of damages for 100 km. All registered damages (1).
|
Line’s component
|
Lines with XLPE (kV) insulation
|
Lines with paper-oil insulation (kV)
|
|
60-219
|
220-500
|
Total
|
60-219
|
220-500
|
Total
|
|
Cable
|
0,085
|
0,133
|
0,088
|
0,109
|
0,248
|
0,149
|
|
Connection box
|
0,007
|
0,048
|
0,004
|
0,0065
|
0,014
|
0,006
|
|
Terminal box
|
0,011
|
0,050
|
0,013
|
0,014
|
0,028
|
0,019
|
Besides, the time for damages removal was also analyzed. Different conditions had been examined.
For instance, for the cable lines of ac voltage from 60 up to 219 kV in other words the most interesting segment of voltages for the power engineering specialists, up to 90% of damages had been removed during the period up to one month, but 5% of damages for the cable in paper-oil insulation the period of damages removal was more than three months. Comparison of time for damages removal in the cable lines with extruded insulation and cables with paper-oil insulation for the whole spectrum of voltages are represented on drawing 3. The time of damages removal in the ac voltage cable lines is shown in table 8 and on drawing. An average time of repair for the cable lines with XLPE insulation makes 20 days, but for the cable lines with low pressure paper-oil insulation - 29 days.
|
|
|
120
|
|
|
|
100
|
|
Row 1
|
|
80
|
|
Row 2
Row 3
|
|
60
|
|
Row 4
|
|
40
|
|
|
|
20
0
|
|
|
|
Insulation made of artificial plastic Paper insulation
|
|
Row 1 - less than 1 week
|
Row 2 - from 1 week up to 1 month
|
|
Row 3 - 3 months
|
Row 4 - more than 3 months
|
|
|
|
|
Drawing 3 - Percent distribution of time duration for repair the cable lines laid overland with paper insulation and insulation made of artificial plastic.
Table 8. Average time of repair in days for different design of the cable for high and extra-high voltage.
|
Voltage level (kV)
|
Cable design
|
|
Paper insulation + oil
internal pressure
|
Extruded insulation
(elastrons)
|
|
From 60 up to 219
|
20
|
15
|
|
From 220 up to 500
|
38
|
25
|
At analysis of the cable lines damage cases we examined only the time of repair, for the cases when this period was not less than 1 day and no more than 6 months. The cases outside of these time limits were not taken into account. For the cable lines with voltage up to 220 kV the difference of average time for repair is equal to 5 days for two the most popular designs, used today for cabling into soil. But in case of higher voltage it requires longer period of time, and difference is already equal to 14 days. The time for damages elimination in the analyzed cable lines is equal to from 1 day up to 6 months. Anaverage time, expressed in the amount of days required for repairing of cable lines laid overland, by two most often used methods of cabling is shown in table 9. For the voltages up to 210 kV practically there are no differences, but at higher voltages this time period in average is for 20 days more at cabling in channels, underpasses, piped passages. But here we can dispute grouping of such cable damages cases at cabling in piped passages and underpasses.
Table 9. Average time in days depending on methods of cabling.
|
Voltage level (kV)
|
Laying of cable line
|
|
Directly into ground
|
Pipes, channels, underpass
|
|
from 60 up to 219
|
14
|
15
|
|
from 220 up to 500
|
25
|
45
|
Comparison of data regarding accident rate of cable lines collected from different documents is represented in table 10. Received data seems too optimistic, since following years include greater number of lines in the network.
Table 10. Comparison of data regarding accident rate of cable lines for the period since 1991 up to 2008 (1).
|
Publication
|
CIGRE article
2-07 1991
|
CIGRE article
2-07 1991
|
CIGRE WG
B1-10 2008
|
|
Period of analysis
|
1950-1980
|
1980-1990
|
1990-2005
|
|
Length of cable lines
|
3 610
|
no data
|
7 100
|
|
Number of damages
|
154
|
116
|
49
|
|
Damage ratio
|
0,32
|
no data
|
0,12
|
|
Average time of line disconnection
|
37
|
70
|
60
|
Conclusion
The development of cable lines is an accomplished fact. We are observing dynamic increase of the amount of cable lines which are under construction, not only due to the need of increasing the amount of delivered electric power to greater number of the users, but also as the achievement of results on assurance of reduction the influence of energy facilities on environment.
Literature (1) Rosevear R.D., Choquette, Fairhurst M., Jorgensen H.J., Larsen J.E., Mampeay B., Rakowska A., Tricoli S., Waschk V. Update of service experience of HV underground and submarine cable systems, CIGRE TB 379, April 2009, ISBN 978-2-85873-066-7, s. 1-84.
(2) Swingler S., Barber K., Daly J., Award R., Antic J., Zenger W. Statistics of AC underground cables in power networks, CIGRE TB 338, WG B1-07, December 2007.
(3) Rosevear R.D., Choquette, Fairhurst M., Jorgensen H.J., Larsen J.E., Mampeay B., Rakowska A., Tricoli S., Waschk V. Update of service experience of HV underground and submarine cable systems, ELECTRA, No 245, April 2009, CIGRE, pp. 53-57.
(4) Kobayashi S., Tanak S., Suetsugu M. Development of factory-expanded cold-shrinkable joint EHV XLPE cables, JICABLE 2003, paper A5.1
|
