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Present-day high-voltage CL: installation and maintenance experience. Part 2
First part of the article
The experience of usages according to collected data, allows to carry out the objective estimation of the chosen cable design. The total amount of damages for special types of cable lines with division into damages of cable itself or damages of cable fittings (connecting and terminal boxes) are designated in the Table 4.
Table 4. The quantity of the ac voltage cable lines damages (without taking into account lines laid on seabed) within the period from 2000 up to 2005 (1).
|
Cable type
|
Type of damage
|
Place of damage
|
|
cable
|
connec-
tion box
|
termina-tion box
|
other сom-ponent
|
uncertain place
|
Total
|
|
XLPE
|
internal
|
26
|
40
|
28
|
2
|
-
|
96
|
|
external
|
47
|
13
|
17
|
2
|
-
|
79
|
|
uncertain
|
3
|
6
|
5
|
0
|
-
|
14
|
|
total
|
76
|
69
|
50
|
4
|
0
|
189
|
|
Paper + oil
|
internal
|
21
|
12
|
11
|
6
|
-
|
60
|
|
external
|
63
|
6
|
9
|
1
|
-
|
68
|
|
uncertain
|
3
|
3
|
4
|
0
|
-
|
10
|
|
total
|
77
|
20
|
24
|
7
|
0
|
128
|
|
polyethylene
|
internal
|
9
|
1
|
21
|
0
|
-
|
31
|
|
external
|
33
|
3
|
6
|
0
|
-
|
42
|
|
uncertain
|
3
|
0
|
6
|
0
|
-
|
8
|
|
total
|
45
|
4
|
32
|
0
|
0
|
81
|
|
Paper + oil
of high pressure
|
internal
|
13
|
6
|
3
|
7
|
-
|
29
|
|
external
|
19
|
7
|
2
|
7
|
-
|
35
|
|
uncertain
|
1
|
0
|
1
|
2
|
-
|
4
|
|
total
|
33
|
13
|
6
|
16
|
0
|
68
|
|
Gas + paper
|
internal
|
10
|
1
|
3
|
1
|
-
|
15
|
|
external
|
4
|
0
|
6
|
4
|
-
|
14
|
|
uncertain
|
0
|
0
|
2
|
2
|
-
|
4
|
|
total
|
14
|
1
|
11
|
7
|
0
|
33
|
|
EPR (ethylene-propylene rubber)
|
internal
|
0
|
0
|
2
|
0
|
-
|
2
|
|
external
|
4
|
0
|
0
|
0
|
-
|
4
|
|
uncertain
|
0
|
0
|
0
|
0
|
-
|
0
|
|
total
|
4
|
0
|
2
|
0
|
-
|
6
|
|
PILC (oil soaked paper)
|
internal
|
244
|
9
|
4
|
1
|
1
|
269
|
|
external
|
49
|
1
|
2
|
4
|
-
|
56
|
|
uncertain
|
0
|
0
|
1
|
0
|
-
|
1
|
|
total
|
293
|
10
|
7
|
6
|
1
|
316
|
|
DC (oil + paper)
|
internal
|
0
|
18
|
0
|
0
|
-
|
18
|
|
external
|
0
|
0
|
0
|
0
|
-
|
0
|
|
uncertain
|
0
|
0
|
0
|
0
|
-
|
0
|
|
total
|
0
|
18
|
0
|
0
|
0
|
18
|
|
AC voltage cable of uncertain design
|
internal
|
0
|
0
|
1
|
0
|
-
|
1
|
|
external
|
3
|
4
|
1
|
0
|
-
|
8
|
|
uncertain
|
4
|
1
|
0
|
0
|
2
|
7
|
|
total
|
7
|
6
|
2
|
0
|
2
|
16
|
|
Total quantity of damages
|
549
|
130
|
134
|
39
|
3
|
855
|
In total, within 5 years (from 2000 till 2005) it was registered 855 cases of damages in the high and ultrahigh voltage cable lines that are laid overland (without taking into account the cable laid on seabed). 316 damages are registered for cable lines with the use of cable design with oil soaked paper insulation, which is also called "traditional". But it should be noted that cables of such type are in usagefor many years and most of them already exceeded the warranty period of operation.
Besides, 189 damages are registered for cable lines with the use of cable in insulation of “cross-linked polyethylene” XLPE. In addition it also should be noted that 55% of damages for the cable of this type are internal damages. In total, as to the ac voltage cables it was registered that 33% of damages were caused by internal influence, and 67% of damages caused by external factors. General data of damages during operation for the cable lines of more than 60 kV are represented in tables 4 and 5.
Table 5.Percentage of damagesthe ac voltage cable lines (without taking into account lines with cable with oil soaked insulation) with division into the types of internal and external factors and indication the places of their laying (1).
|
Voltage
|
Cause of damage
|
%% of the given type damages to the total sum of damages
|
|
trestle
|
soul
|
air
|
channel
|
overpass
|
underpass
|
sum
|
|
60-219
|
External – abnormal environmental conditions
|
0
|
2
|
0
|
0
|
0
|
0
|
2
|
|
External – other extreme conditions
|
0
|
7
|
2
|
3
|
1
|
0
|
10
|
|
External – mechanical damages
|
0
|
24
|
0
|
2
|
2
|
0
|
28
|
|
Internal
|
0
|
21
|
3
|
0
|
4
|
4
|
32
|
|
Total
|
0
|
54
|
5
|
2
|
7
|
4
|
72
|
|
220-500
|
External – abnormal environmental conditions
|
0
|
1
|
0
|
0
|
0
|
0
|
1
|
|
External – other extreme conditions
|
0
|
3
|
0
|
0
|
0
|
0
|
3
|
|
External – mechanical damages
|
0
|
6
|
0
|
0
|
1
|
0
|
7
|
|
Internal
|
0
|
13
|
0
|
1
|
1
|
2
|
16
|
|
Total
|
0
|
23
|
0
|
1
|
2
|
2
|
28
|
|
60-500
|
Total sum
|
0
|
77
|
5
|
3
|
9
|
6
|
100
|
For no-failure operation of the cable line it is important to provide not only the quality of cable itself, but also the quality, correct mounting and usage of cable fittings - connecting and terminal boxes, that should always be kept in mind. Therefore, the development and production of such cable fittings is obligatory in order that a possibility of error arising during its installation was minimal and performing of the operational procedures was maximally simplified. Due to such properties cable fittings fabricated by assembly technology (technologies of semi-finished goods) become more and more popular. Example of such cable box for 400 kV voltages is shown on drawing 1, and installation of cable box for 330 kV voltage in Dnepropetrovsk - on drawing number 2.
Damage ratios of the ac voltage cable lines based on the collected data – internal causes taking into account all registered damages are shown in the tables 6 and 7. The comparison of damage ratios for the cable itself and for cable fittings taking into account damages of connecting and termination boxes is quite interesting.
Drawing 1. Installation of cable box for 400 kV (4).
Table 6. Damage ratios of cable lines with elements distribution in correlation to the amount of damages for 100 km. Internal 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
|
0,027
|
0,067
|
0,030
|
0,014
|
0,107
|
0,041
|
|
Connection box
|
0,005
|
0,026
|
0,005
|
0,002
|
0,010
|
0,004
|
|
Terminal box
|
0,006
|
0,032
|
0,007
|
0,005
|
0,015
|
0,009
|
Drawing 2 – Installation of cable box for 330 kV voltage in Dnepropetrovsk.
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