Full resolution (JPEG) - On this page / på denna sida - 1958, H. 4 - An Insulated Cable for Heavy Power Transmission, by Bror Hansson
<< prev. page << föreg. sida << >> nästa sida >> next page >>
Below is the raw OCR text
from the above scanned image.
Do you see an error? Proofread the page now!
Här nedan syns maskintolkade texten från faksimilbilden ovan.
Ser du något fel? Korrekturläs sidan nu!
This page has never been proofread. / Denna sida har aldrig korrekturlästs.
Fig. 10. Life curve for cable.
It should be noted from fig. 9 that the viscosity of
the oil is 8 times lower at a working temperature
of 70°C.
For the figures in table 3 it is presumed that the
oil pressure difference betwreen the inflow and
outflow is 10 kp/cm2. The table gives the flow in one
direction only, thus the figure given for the flow
in the central channel is the flow which we would
have if no shunt flow, i.e. through the dielectric,
existed.
While it is allowable to use 10 kp/cm2 and more
in the central channel and radially through the
dielectric, it would be preferable not to use so high
an oil pressure in the channels under the relatively
weak lead sheath.
Table 3 shows that for a cable length of about
500 m the flow resistance axially through the central
channel and radially through a 28 mm dielectric
built up of 130 n thick, porous papers, are about
the same. It is also seen that for a 500 m long cable
both the dielectric losses and the copper losses are
about the same, 10 kW. The oil flows, both axially
and radially, are capable of taking away respectively
the copper and the dielectric losses which were both
10 kW.
The table also shows that the flow resistance of the
channels under the lead sheath is entirely too high
and that for such a long cable it wrould be necessary
to use either a surrounding or a parallel pipe to take
the oil to the terminal or the reservoir.
Mr. Bengt Bjurström has contributed to this paper
by comparing the costs for equipment and losses for
a 1 000 m, three-phase, 425 kV and 1 200 amp. line,
designed as alt. 1 an ordinary oil filled cable, and
as alt. 2 and 3 this new cable with dynamic oil flowr,
alternatively with 900 and 550 mm2 copper cross
sections. Table 4 shows the results of this calculation
made in Swedish crowns.
This comparison indicates that even at 425 kV and
1 200 amps the new design as such, economically
compares favourably with present 425 kV designs.
If the fact that the new cable may be used for more
current and higher voltage or with reduced
insulation thickness and reduced conductor cross section
Table Calculation of costs for cables of different designs in thousand Swedish crowns.
Cable design Alt. 1 Alt. 2 Alt. 3
Conductor, mm2...................... 900 900 550
Insulation composed of .............. 50 [x papers near 130 ft papers 130 fi papers
the conductor throughout throughout
up to 100 n
under lead
Insulation thickness, mm ............. 28 28 28
Type of oil system ................... (Söderåsen type) Dynamic oil Dynamic oil
flow cable flow cable
Type of expansion vessels ........... Pirelli type with Vacuum tank Vacuum tank
metal cushions
Costs for equipment for 3 X 1 000 m cable
For cable, terminals and joints ....... A A —9.6 A — 9.6—37.5
For expansion tanks with accessories . . 55.0
For vacuum tank with oil............ 4.5 4.5
For vacuum pump with motor ........ 4.0 4.0
For oil pump with motor............. 3.0 3.0
For pipe line ........................ 3.0 3.0
For accessories ...................... 1.5 1.5
Costs for equipment.................. A + 55.0 A + 6.4 A —31.1
Capitalized costs for losses Losses Capitalized
kW value, cr/kW
In conductor ....................... 3 X 34 800 81.6
In segment conductor................ 3 X 32 800 76.8
3 X 52 800 124.8
Dielectric losses..................... 3 X 15 2 200 99.0
3 X 11 2 200 72.3 72.3
Pumps 10 kW ...................... 2 200 22.0 22.0
Total costs ......................... A + 235.6 A + 177.5 A + 188.0
ELTEKNIK 1958 1 56
<< prev. page << föreg. sida << >> nästa sida >> next page >>
