Tech Briefs Magazine - October 2021 - MD-12

Improving Overhead Equipment Devices for a New
Era of Railway Transportation
The railway network is the backbone of
the transportation system in India,
connecting remote villages and towns
with metropolitan cities across the country.
Recent government initiatives aim to
revamp and modernize the entire network
by 2030 and the past couple of
years have brought many changes to the
rail system.
From a technological perspective, two
notable changes can be expected to
Indian railways: the introduction of electric
and solar-powered trains and an in -
crease in the operating speeds of trains
from 100 km/h to 160-220 km/h. To
support these plans, suitable modifications
must be made to the existing infrastructure
and components such as the
overhead equipment (OHE) including
catenary and contact lines as well as pantograph
assemblies.
Raychem RPG, which provides energy
solutions for various sectors, has a dedicated
team working on products that can
meet the challenging requirements of the
evolving railway network. The team of scientists
and researchers, led by Ishant Jain,
used multiphysics simulation to improve
the designs of autotensioning devices
(ATD) and modular cantilevers (MC) -
two of the most critical components of the
railway's overhead equipment.
Protecting Railway OHE Lines
In an electric rail system, power is supplied
by overhead lines that run along
the entire length of the railway track.
This power is transferred to the train by
means of the pantograph, which is a current
collector mounted on top of the
locomotive. The ATD (Figure 1, left)
pro vides a mechanism for automatic tensioning
and serves as a termination
point for the contact lines. Tensioning is
needed on the contact lines due to the
variation in their lengths: Contact lines
are primarily made from copper-based
alloys that are prone to expansion and
contraction due to variations in atmospheric
temperature.
The conductors of overhead lines are
installed with a very specific tension
value. This tension is variable over time
and is closely dependent on the ambient
temperature. The absence of tensioning
causes the overhead lines to sag or tighten,
leading to pantograph entanglement
or snapping of the overhead equip ment
(OHE) lines.
Similarly, overhead MCs are designed
to support the assembly of overhead
power transmission wires - i.e., catenary
(1000/1200 kgf tension), contact
(1000/1200 kgf tension), and droppers
- to transfer the overall bending, transverse,
and vertical loads to the mast via
insulators (Figure 1, right). The quintessential
cantilever is lightweight and
robust enough to support the currentcarrying
assembly with train speeds up
to 250 km/h. In addition to these functional
requirements, ease of maintenance,
transportation, handling, and
aesthetics also need to be considered.
Design Challenges for Railway
Components
To ensure the safety of rail passengers
at high speeds, the ATD has stringent
design requirements. To determine
the correctness and efficiency of
an ATD design experimentally, a pullout
test is performed. A large experimental
setup is required for such a test,
which is not practically feasible at all
times. The team at Raychem RPG,
working out of the Raychem Innovation
Centre (RIC), was tasked with designing
an ATD that is both lightweight and
highly sensitive to temperature fluctuations,
while providing ease of service,
assembly, and maintenance.
In addition, the MCs that can be im -
ported from European and American
markets are bulky and include many
ancillary components. As part of the
" Make in India " government initiative,
the Raychem team's objective was to
come up with a novel design to eliminate
these ancillary components while
ensuring structural integrity by efficiently
using material, which ultimately
saves costs and reduces weight. To
achieve both design goals, the Ray -
chem team used TRIZ, a theory for
coming up with innovative solutions to
problems, for generating and conceptualizing
various ideas. They then
turned to COMSOL Multiphysics®
software
from COMSOL for optimization
and design validation as per the railway's
standards.
Stay tube
Insulator
Register arm
Figure 1. Autotensioning device (left) and diagram of the modular cantilever assembly (right).
12
Cov
ToC
Motion Design, October 2021
Mast
Insulator
Catenary wire
Bracket tube
Contact wire

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Tech Briefs Magazine - October 2021

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