New Hawker Siddeley Switchgear SafeBond DC Switchgear Provides a Safer Option of Track Isolation

Hawker Siddeley Switchgear currently manufactures a range of DC circuit breakers and switchgear that is supplied to rail transport systems worldwide; HSS Lightning Switchgear. Hawker Siddeley Switchgear are now pleased to introduce the new SafeBond, the next generation of the Lightning DC switchgear range. SafeBond is designed to contribute to improving safety and reducing lead times for track maintenance periods. 

Automated bonding switch.

To isolate tracks for staff access, the current practice is for staff to manually apply straps between the conductor system and running rails to make it safe for track maintenance. The manual application of bonding straps is hazardous and requires lengthy procedures to ensure that the line-side staff who apply the straps are safe; all trains are stopped and power isolated whilst the straps are attached, the permissions must be obtained from power, control and signalling centres, etc.  Also, emergencies requiring the evacuation of a train may require the driver to apply a shorting bar directly onto the conductor system which may be energised, an action that can put the driver at risk of injury.

SafeBond allows for isolation of the track from the track feeder circuit breaker panel, which means there is no longer a need for track side staff to go out to track to isolate it. This obviously improves the safety of trackside workers and the speed of track isolation, reducing outage time as well as maximising the available time during a maintenance possession.

SafeBond draws on the standard practice used on Medium Voltage, Fixed Pattern AC switchgear to provide enhanced safety for trackside workers.  By including a two-position motorised Disconnector on the busbar side of the circuit breaker, the SafeBond may be used to either feed the track for normal service or bond the conductor system to earth (or negative) for safety.  SafeBond is fully interlocked to prevent unsafe operation and protection relays are automatically disabled when bonding the track, including the option of disabling the Direct Acting Trip within the Circuit Breaker.

“The greatest benefit of SafeBond is that all load and fault switching is performed by a High-Speed Circuit Breaker, which enhances operator safety when compared to traditional earthing switches and manual bonding methods which can expose operators to danger if closed onto a live system,” said Lyn Jones, Hawker Siddeley Switchgear’s Senior DC Applications Engineer.  “All operations may be carried out from the front of the SafeBond panel, with the Circuit Breaker behind a closed door, and optional remote operation allows switching to be undertaken from a central location to allow absolute flexibility in the use of SafeBond on all systems”.

Bonding Switch and Breaker in one panel.

Where separate switchgear is used for providing the bond, there can be high capital costs because of the value of the additional equipment, the amount of civil works required to add the equipment into the operational railway environment and the addition of cabling and installation costs. Space needs to be found adjacent to the track or a substation to locate the additional equipment, and where this space is not available the cost of obtaining land may be prohibitive.

SafeBond no longer requires a separate bonding switch as the SafeBond incorporates a bonding switch and breaker into the footprint of a standard Lightning panel meaning that the SafeBond panel is a direct replacement for a Lightning panel, which already has one of the smallest footprints on the market. This is a significant advantage for urban metro and underground systems where substations are often small and in locations with high land value, meaning that there is no space for additional switching equipment.

NDC Circuit Breaker

SafeBond incorporates the NDC High-Speed Circuit Breaker. Combining innovation with 50 years of DC circuit breaker design and manufacturing experience the NDC High-Speed Circuit Breaker offers optimal safety, reliability and high-speed performance. Incorporating Hawker Siddeley Switchgear’s “Fit and Forget” technology the NDC High-Speed Circuit Breaker utilises the patented and award winning magnetic actuator technology and Arc transfer coil. The magnetic actuator and silver tungsten carbide contacts minimise the amount of maintenance required on the circuit breaker and designed to exceed a 30-year service life.

Our patented, single coil magnetic actuator and arc transfer coil innovations have been widely acclaimed, groundbreaking developments, which have provided Hawker Siddeley Switchgear with a world leading edge in circuit breaker technology. The patented Magnetic Latch mechanism provides the primary means of ‘high speed’ tripping of the circuit breaker. Working in conjunction with the Magnetic Actuator, the latch directly holds the circuit breaker contacts closed. The Cold Cathode Arc Chute Assembly dissipates all arcs whilst the transfer coil provides additional magnetic flux across the contact gap, assisting with the interruption of low currents that would otherwise lead to long arcing times. Whilst the patented arc transfer system prevents internal contamination of the circuit breaker compartment and cubicle.

Independently recognised by the Royal Academy of Engineering and the prestigious Queen’s Award for engineering excellence, the actuator coil is energised in one direction to 'power close' the circuit breaker and in the opposite direction to open it by de-latching the holding force.  This unique feature of the actuator design is used in Hawker Siddeley Switchgear’s 'Fit & Forget' range of products and ensures reliable tripping operation.

There are over 50,000 actuator breakers in service across Hawker Siddeley Switchgear’s DC and AC ranges and the NDC High-Speed Circuit Breakers can be found worldwide including, London Underground, Dubai Metro and New York Metro. 

More information

For more information on SafeBond please contact – sales@hss-ltd.com or call 01495 223001

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