Product category:
Batteries, chargers and circuit protection
News Release from: Alcad | Subject: XHP FR
Edited by the Engineeringtalk Editorial
Team on 02 July 2004
Nickel-cadmium batteries for switch
tripping units
PB Design has fitted Alcad XHP FR rechargeable nickel-cadmium batteries in highly specialised 50 and 110V battery switch tripping units installed in 17 stations on London Underground's Northern Line.
Standby power solutions specialist PB Design has fitted Alcad XHP FR rechargeable nickel-cadmium batteries in highly specialised 50 and 110V battery switch tripping units installed in 17 stations on London Underground's Northern Line The battery switch tripping units have been installed on the Northern Line as part of Seeboard Power Link's 30-year power service contract for the operation, maintenance, finance and renewal of London Underground's high-voltage power distribution system
They provide a DC supply for the tripping and closing of circuit breakers on the substations which convert London Underground's 11 kV distribution supply to the 630 V supplied to the rails.
The contract for the battery switch tripping units called for PB Design to meet a number of specific requirements.
These included: all materials, including batteries, to be low smoke and zero halogen; equipment to be of the highest quality and reliability; ultra-low-ripple output to ensure compatibility with other equipment used on the network; and a comprehensive monitoring and fault finding system.
Paul Britton of PB Design said: "Nickel-cadmium batteries were the natural battery choice for this exacting application due to their high reliability factor".
"We also required a battery with high performance and low maintenance, together with flame retardant capabilities".
"Alcad's XHP FR range provided the ideal solution".
The battery switch tripping units automatically keep the batteries fully charged.
In the event of a mains power failure the batteries are required to provide a minimum of eight hours standby power after which they must still be capable of tripping and switching the circuit breakers.
Alcad sized the batteries to IEEE1115 to meet these criteria.
Depending on the installation batteries with capacities ranging from 52 up to 220Ah have been supplied.
Alcad XHP cells are designed specifically for high rate discharge duties.
They are ideally suited to replace valve regulated lead acid (VRLA) batteries for critical applications where a reliable source of back-up power is essential.
The key feature of the XHP cells is their sintered/plastic bonded electrode technology which is proven to need only minimal attention after installation, since their noncorrosive construction and highly efficient electrochemistry makes repeated checks for topping-up, recharging or replacement completely unnecessary.
This inherent reliability over a 20 year plus service life eliminates the fear of the unpredictable "sudden death" failure sometimes encountered with lead-acid batteries, as well as enabling the user to benefit from savings over regular replacement, maintenance and down-time costs.
A further advantage of the XHP cells is that they provide high power output within a narrow voltage "window" and can also provide very high currents of up to 20 times the battery's nominal capacity.
Compared with VRLA batteries, XHP batteries are also more tolerant of electrical abuse such as overcharging, deep or even complete discharge, and offer superior performance at extremes of temperature, with an operating range of -20 to +40C.
XHP cells are available in nominal capacities from 11 to 320Ah.
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