Proceedings 2002/2003 - IRSE

134 WESTERN SECTION
Scotland. (Attendance 14 members, 4 visitors)
For the fourth paper of the session, took place in
Hyder’s offices in Bristol and the paper was entitled
“TPWS Experience” by Andy Scarisbrick of Amey
Rail.
Andy started by outlining the reasons for train
control and demonstrated this by detailing a list of
SPAD accidents. He followed this through with a
detailed explanation of the Great Western automatic
train control (ATC) system the British Rail (automatic
warning system (AWS) and the Great Western Main
Line automatic train protection (ATP) system.
The Railway Safety Regulations of 1999 mandates
a train protection system to be in place by 1st June
2004 which prevents SPADs by the use of a train
stop at a stop signal, over speed sensing on
approach to a stop signal and overspeed sensing on
approach to a permanent speed restriction or a
buffer stop. The driver cannot override the system or
cancel the system whilst the train is in motion.
Andy then went on to the descriptions of the
equipment using system architecture diagrams and
photographs of both the train borne equipment and
the track mounted equipment. The frequencies used
are between 64 and 66kHz, the actual frequency
being dependant on the direction and whether being
used as a train stop sensor (TSS) or an overspeed
sensor (OSS). The distance between the loops and
the distance to loops is critical and are shown on the
track plan for any relaying work.
Using line diagrams the fitment principles were
explained with the following emphasis. Emergency
crossovers – Ground Frames – do not require fitment
but ground frames for traffic purposes do require
fitment. The safe operating distances range from
125m at 21mph to 550m at 70mph with an OSS
always being required at speeds over 70mph.
Pictures were shown of the failure indication unit
used in the mechanical signalboxes which demonstrated
how the TPWS was monitored in mechanical
areas. Failure modes which give an indication are
power failure, incorrect frequency being generated
and absence of the loop. On NSKT lines the TPWS
was driven by the token machine. A special indicator
was provided for the driver to show that
suppression of the TPWS had been achieved. A
special UPS had been designed and built for most
guaranteed supply areas.
Some figures showing the activation of the TPWS
were shown. In August 2002 there were ten activations,
in September six activations, in October 20
activations and in November 2002 there were 12
activations. (Attendance 17 members, 10 visitors)
The February paper was again held in WRSL’s
offices in Chippenham, was entitled “High Speed
Trains for the West Coast Mainline” and was
presented by Mr John Evans of Alstom. This was a
joint meeting with the local IEE Section.
Mr Evans started by saying that his paper would
be looking at the 1980s locomotives, the 1990s
locomotives and those currently being built and
tested for Virgin – the Pendolino.
The type introduced in the 80s made use of a
thyristor controlled DC motor and was powered in
one of two ways – a low voltage 750V or 1500V DC
high current supply or a 25kV AC low current supply.
The former was used on metro and suburban trains
and the latter on long distance high speed trains
such as the class 91 loco used on the ECML.
The next generation introduced in the 90s made
use of the gate turn off (GTO) thyristor which was
initially used on DC chopper circuits such as those
on the class 319 units. These were more powerful
devices than those of the 80s and led to propulsion
inverters being both affordable and practical. The
advantages of the GTO is that control is always
maintained, it has a high transient current, it works
up to 500Hz and fails into a known state – short
circuit. The use of a propulsion inverter led to
variable voltage variable frequency being fed to AC
motors. The application was the Eurostar train that
has input capability of 750V DC, 3kV DC and 25kV
AC, has a top speed of 300kph and was powered by
12 synchronous motors in the two power cars and
first trailer cars. All the systems were duplicated.
The current generation makes use of insulated
gate bipolar transistor (IGBT) technology which is a
large power switching device. The advantages of
IGBT are simple equipment design, high reliability,
fast switching, voltage controlled simple gate
device, a simple mechanical construction and is
available up to 1800A and 6kV. The application is is
in the 1700V 800A Juniper units, the Virgin Cross
Country Voyager units and for high frequency
operation the Pendolino Britannico.
The Pendolino has a high level of customer
specification, improved journey times, improved
reliability and improved customer ambience. The tilt
technology is from Fiat who have used it extensively
in Europe where it was adapted from the 70s
APT tilting technology. The traction drives are the
same as the Juniper equipment and thus can carry
over the safety case. The power equipment is distributed
with a feeder system along the roof. The
maximum speed is 140mph and it entered service in
July 2002. It has twelve body mounted traction
motors driving through a 10-foot Cardin shaft The
use of tilt allows faster speeds through corners
without the customer noticing. Fiat had 12 fleets of
tilting technology in service when the Pendolino
order was placed. The tilt mechanism is electrical
not hydraulic (only Fiat’s second) and because it is
mounted on the bogie/body interface, the traction
motors have to be body mounted. The tilt mechanism
allows a 35% increase in speed.
The vehicles are built and completed in Fiat’s
workshops but fitted out in Alstom’s workshops in
Birmingham. Each has 363 seats, is 23m long, is
pressure sealed and has a noise of less than 65dBA.
The reliability will be six times better than now and
as Alstom have to maintain them for 12 years, there
is an incentive to get them reliable. In 2004 there will
be 11 Pendolino Britannico leaving Euston per hour.
(Attendance 17 members, 17 visitors)
The final paper of the session was as usual a joint
paper held with the South Wales PWI in Newport.
This was entitled “Trams – Light and Heavy Rail” and