Full resolution (JPEG) - On this page / på denna sida - The Öresund Power Cable of 1958, by Anders Bergman, Wilhelm Carlshem and Gottschalk von Geijer - Tidskrift om det fasta tillståndets elektronik - Inverkan av strålning på halvledare
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signal cable runs out through the back end. Cable
lengths up to some hundred metres may be used.
With this casing observations may be carried out
down to water-depths of 60 metres. The capacity of
the diver presents a certain limitation which, with
an ordinary air supply and a frogman’s equipment,
is encountered at a depth of 35 metres. An alarm
device is installed which indicates whether water
has penetrated into the camera housing for any
reason.
The electric current supply consists of a
petrol-driven, voltage-regulated motor generator for 220 V,
2 kW. Notwithstanding the fact that a type giving
the best possible voltage- and frequency stability is
employed, the picture cannot be fully compared
with the results obtained when the supply is taken
from a power network.
The diving equipment used is provided with a face
mask so that telephone communication can be
maintained with the personnel in the following boat. One
advantage of this type of mask is found in the fact
that the whole of the face is protected against cold
when working in water at low temperatures. The
resistance to breathing offered by the mask is low.
While diving is in progress an ample supply of air
is available in the assistant boat, so that the diver
can concentrate on the investigation without
concerning the control of the air supply; he also carries
spare air tubes on his back.
Observations of the divers
At one point approximately 1 200 metres from the
Swedish shore a cable span some 25 metres in length
was discovered in the course of the investigation
as in fig. 8. The cable was very slack at this point
but did not make contact with the bottom. The
current running at 2 knots at the time of
investigation set up lateral oscillations in the cable. There
is a risk that these oscillations may give rise to
fatigue in the lead sheath. Representatives for the
participants investigated the span by means of
underwater television, and decided the cable to be
moved a few metres to the south where the bottom
was smoother. This work has now been undertaken.
On the Danish side the bottom consists of fine
sand, and here the cable is being gradually covered
over. At one point 300 metres from the shore the
cable rested on a large block. This part of the cable
has been moved to smooth bottom with the help
of the diver’s boat.
Excellent assistance was obtained from the
frogman’s equipment in the provision of shore
protection for the cable. Consequently, certain parts of
the work on the Swedish side were accomplished
by workmen clothed in rubber suits. Owing to the
low depth is was not necessary to use face masks.
Conclusions
Summing up, it may be said that the proposed
objects in connection with the work of laying the
cable have been fully achieved. Laying was carried
out in accordance with a method which is
particularly favourable with respect to the strength of
the cable. Moreover, an advantageous cable route
has been obtained. The amount of slack is great
enough to facilitate any subsequent raising of the
Fig. 8. The cable resting on a large block creating a span.
cable. It has been possible to determine the correct
length of the cable by careful measurements. The
methods adopted for control purposes, in which
frogmen and television were employed, have been
completely successful.
The experience gained in using the Decca
navigator system for the cable-laying operation in Öresund
fully confirms its usefulness in cable-laying over
long distances. In cases where one has to rely on
Decca measurements only, it may be necessary to
use two equipments with separate power supplies.
A thorough examination of fixed and random errors
in the area will be necessary and special charts
must also be prepared. In certain cases it may be
necessary to employ a local Decca chain using mobile
radiotransmitters in order to obtain sufficient
coverage and accuracy. Marking of the cable must be
done in such a manner as to avoid ambiguity e.g.
by making every tenth mark in a different colour.
Painted marks are to be preferred. Sufficient distance
must be allowed between the marks. Experience
shows that at a speed of 1 knot, 100 metres between
marks is sufficient; during the roughest part of the
crossing only every second mark was used. The
overall error is reduced by increasing the number
of marks, but it is essential that sufficient time
should elapse between marks to prevent the work
from becoming unnecessarily wearisome.
The use of the Decca system as a navigational aid
needs little comment. Following a pre-drawn
zigzag route on the track plotter chart may be difficult,
however, especially in rough weather, and
considerable practice is essential for the captain and
helmsman due to the distortion of angles on the chart.
Tidskrift om det fasta tillståndets elektronik. Från
januari 1960 kommer genom Pergamon Press Ltd. 4 & 5
Fitzroy Square, London W. 1. att utges en
månadstidskrift, kallad Solid State Electronics. Syftet med denna
tidskrift är att publicera originaluppsatser inom
halvledar-området och inom övriga delar av det fasta tillståndets
elektronik.
Inverkan av strålning på halvledare. Frågan om hur
radioaktiv strålning inverkar på material som används
inom elektrotekniken och därmed på de elektriska
systemens funktion blir alltmer aktuell i olika sammanhang
(se t.ex. Elteknik jan. 1959 s. 16). I Gatlinburg, Tennessee,
USA, hölls den 6—9 maj 1959 en fysikerkongress över
inverkan av strålning på halvledare. Journal of Applied
Physics har utformat sitt augustinummer 1959 som ett
specialhäfte och publicerar däri alla de 32 föredragen
från kongressen jämte tillhörande diskussionsinlägg.
ELTEKNIK 1959 1 127
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