IRSE News 140 Dec 08.pdf

TECHNICAL
IRSE
These rules formed the basis for an
Excel spreadsheet developed by ALSTOM,
the Parameter Data List (PDL), containing
the composition of the ERTMS packets for
the Havenspoorlijn. The designer had only
to enter the variables that varied
according to the location of the signal, as
all fixed values for the Havenspoorlijn
were already filled in. The spreadsheet for
the messages from the infill balises was
linked to the spreadsheet for the balise
group at the signal. This meant that only
15% of the variables had to be filled in to
obtain a full set of messages.
There were two design teams, one
from Movares and one from ALSTOM, and
each team drew up the same sets of PDLs.
The PDLs generated by the two teams
were compared automatically. Where
there were discrepancies, each team had
to review its own PDL and make
corrections until both teams obtained the
same result. If this proved impossible, the
problem was submitted to the joint team.
LEU/interlocking interface
The LEU/interlocking interface was
produced in accordance with current
practice; the Dutch ATB-NG system uses
encoder units similar to LEUs. As for other
ProRail electronic interfaces, B-relays are
used. The same relays control the signals,
ensuring that the messages that the balise
group transmits correspond to the signal
aspect.
Figure 6: PDL engineering process
CONSTRUCTION
Cable laying
The biggest construction task was the
laying of the cables for all the switchable
balises. In total, over 800 km of cable
were laid, tested and connected in
approximately seven months. To achieve
this, it was necessary to work at several
locations simultaneously. At the peak of
the cable-laying operation, 70 people were
engaged just on laying and burying cables.
There was an additional challenge, in that
some of the cables could not be buried
during the winter. This was the case on
that part of the line which runs along the
sea dike, which protects the Netherlands
against the highest tides. The cables for
this section could not be buried until the
spring.
Surveying the balise locations
The infill balise locations calculated from
Geo_data ERTMS were surveyed-in using
GPS devices. In each case, the balise was
fitted to the first sleeper following the
position given by the GPS coordinates. The
balises at the signals were sited using a
tape measure, taking the distance from the
signal and the joint. All locations were
checked using GPS. This allowed the work
of the measuring team to be verified.
Once the balises had been installed at
the locations indicated, their positions
were re-checked by an independent team.
The as-built positions were compared with
the values from Geo_data ERTMS.
Deviations were evaluated and corrected
where necessary.
Schedule for the changeover from the
existing signalling system
Because setting up a Level 1 system was
new territory for all involved, and in order to
avoid major disruption to traffic on the
Havenspoorlijn, the decision was taken to
start with the simplest tracks. The changes
to the existing system were less significant
on running lines between sidings. On the
eastern part of the Havenspoorlijn,
however, an interlocking layout
modification had to be implemented at the
same time as the Level 1 project. It was
decided to start at the western end of the
Havenspoorlijn and work towards the east.
Following initial construction work, an
enhancement suggestion was made
regarding the installation of the cables
linking the LEU and the balise. The details
of the cable to be used were only known
three months after engineering work
started, and the cable proved substantially
less flexible than the cables used by
ProRail hitherto. The enhancement
proposal was immediately implemented for
designs in progress, and the rest of the
design process caused no further problems
as far as cable installation was concerned.
Switchable level transition
The balises could be installed without
problems, as the train-borne equipment
ignores balise messages so long as Level
STM-ATB is active. The exceptions are
those balises responsible for initiating
transition; when a train receives a message
from one of these balises it will make the
transition, in this instance to Level 1. In
principle, therefore, the “transition balises”
should not be installed (or activated) until
the system is taken into service. However,
it is necessary to carry out test runs
beforehand, and these have to include
realistic transitions from Level STM-ATB to
Level 1 and vice versa. To enable these
test runs to take place, the transition
balises were activated and de-activated
using a keyswitch installed in a relay box.
This made it possible to activate the
transition function for test runs and then
de-activate it again. As a result, normal
trains could pass the transition balise
undisturbed, and as the train remained in
Level STM-ATB it could also ignore all other
balises.
The switchable transition balises will
also be used for approvals testing of trainborne
equipment. It is possible to test the
transition to Level 1 during the day, as no
equipment has to be installed on the track
or removed from it.
10
Issue 140 December 2008
IRSE
NEWS