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Present-day high-voltage CL: installation and maintenance experience. Part 1
Present-day high-voltage CL: installation and maintenance experience
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Alexandra Rakovska
Electrical Power Engineering Institute
of Poznan Polytechnic
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Yan Shtefoonyk
“Kiev energy construction company”
Group “SVS-Dnipro"
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On the given moment a lot of cable lines, laid both directly into ground, and also on seabed are commissioned all over the world. And in addition the more modern and improved methods are
used for their laying.
High-voltage lines with paper insulationsoaked with oil and starting from the second half of 90-th the cable lines with cross-linked polyethylene insulation - XLPE are constructed in Ukraine. At present there are in operation the cable lines on voltage of 110kV , including the line that was laid on the bottom of Kagul lake in Odesskaya region (the length of water part is about 1000м), lines on voltage of 150 kV in Dnepropetrovsk city and the first cable line on voltage of 330 kV is under construction process. The organizations that are engaged in operation of cable lines due to the short term of high-voltage lines operation have not large experience of their operation therefore we hope that world experience in this field will be interesting.
In order to evaluate such experience on operational use of the increasing lengths of cable lines of high and super-high voltages, the data of such kind are collected all over the world. Among them is registered in Holland the International organization KSANDR - responsible for testing and training in the issue of the networks control and for estimation of reliability the elements of electrical power systems. This organization collects the data on accident rate on electrical power networks all over the world, but these data basically concern the experience on operation of cable line of average voltage. The attempts on collection such data were also undertaken within the framework of CIGRE activity in committee B1 (the table 1). At present within the framework of block "SC B 1 Electric-power cables" several working groupsare functioning, among them is also WG B1.10 Update of service experience on underground and submarine cables. The data for analysis were collected on cable lines for the voltage of 60 kV and higher.
In the technical booklet where the data transferred from all over the world are collected and analyzed, the structures and used cable fittings (1, 2) are presented in a sense of review. Collected data are related to the experience of operation for the period of five years for cables, laid in ground, and fifteen years for cables, laid on seabed. In both cases the final date of analyzed data is the end of 2005.
In general, the analysis of operation of cable lines laid directly in ground - 33 000 km in conversion into one electric circuit, and 7 000 km for cables, laid on seabed (the table 1) was made. Unfortuna-tely, these data do not include all cable lines existing all over the world, since the answers for all distributed questionnaires were not received (in some cases the answer was not received for the whole country). But the volume of received data allows assuming that these results could be referred to all lines and on this base it is possible to define the existing directions of development.
Table 1. Lengths of cable lines, for which the analysis of statistical data was made (1).
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Level of voltages (kV)
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Length of cable lines according to different analyses, in km
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CIGRE
B 1-10 2008
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Electra 137 1991
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Worldwide EHV 2006
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CIGRE
B 1-07 2007
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European Commission
2003
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60-109
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18 000
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3 646
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0
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24 859
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0
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110-219
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9 500
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717
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0
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22 406
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16 000
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220-314
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4 500
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1 591
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2 000
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5 555
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1 720
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315-500
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1 000
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230
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200
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1 586
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120
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>500
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0
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2
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0
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0
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0
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Sum
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33 000
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6 195
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2 200
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54 406
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17 840
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The analysis of usage experience of the cable networks 33 000 km by length in comparison with data published by CIGRE in 1991, shows that cabledesign in "cross-linked" polyethylene - XLPE and "paper soaked with oil" insulation of low pressure (the table 2) takes dominant position.
In total there were 32 917 km of such cables in comparison with 6 195 km by the analysis for 1991 that shows the significant dynamics of growth. Amongst the cable lines of voltage up to 220 kV laid at period from 2000 till 2005 about 90% these are the cable designs in "cross-linked" polyethylene - XLPE insulation. Among these types of cable increasingly more used the cable with longitudinal and transverse compaction, and amongst cable fittings – the most popular are prefabricated structures (3).
Table 2. Lengths of ac voltage cable lines as per the end of 2005.
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Cable type
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Cable sheathing/ compaction
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Nominal voltage
(kV)
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60-109
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110-219
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220-314
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315-500
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SCOF – low pressure oil
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-
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3 300
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4 116
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2 342
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724
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HPOF- high pressure oil
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-
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121
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474
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579
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24
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DC (direct current)
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-
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68
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592
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-
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-
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PILC (oil soaked paper)
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-
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522
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-
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-
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-
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EPR - ethylene-propylene rubber
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metal sheathing
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11
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137
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1
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-
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without compaction
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-
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16
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-
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-
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PE (polyethylene)
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metal sheathing
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497
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60
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397
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1
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without compaction
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125
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7
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-
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-
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Compaction of Al foil
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9
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-
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-
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-
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XLPE (“cross-linked polyethylene”)
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metal sheathing
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3 161
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2 609
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1 114
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229
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without compaction
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4 480
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415
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1
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-
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Compaction of Al foil
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5 683
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1 057
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23
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21
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Total number of cable lines
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32 917
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17 978
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9 483
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4 457
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999
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% of cable with polymer insulation
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61
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78
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45
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34
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25
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% of cable with paper insulation
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39
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22
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55
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66
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75
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756 km of DC voltage cable lines were laid to the end of 2005. 59% of them - was a cable in insulation of extruded polymer - in insulation of "cross-linked" polyethylene. And lines with cable in «paper-oil» insulation constituted 41% and as for the lines of voltage 220 kV and above the given insulation occupy the dominant position (the table 3).
Table 3. Length of DC voltage cable lines that were in operation on the end of 2005.
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Cable for DC voltage
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Nominal voltage (kV)
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60-109
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110-129
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220-134
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315-500
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Paper-oil insulation
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-
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134
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20
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158
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Extruded insulation with radial
seal
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265
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181
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-
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-
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Mounted cable in total
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758
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265
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315
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20
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158
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% of cable with XLPE
insulation
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59
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100
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57
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0
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0
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% of cable with paper
insulation
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41
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0
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43
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100
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100
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Continuation of the article
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