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February 3, 1999 Reliability is key to battery choice for critical control system back-up: Nickel-cadmium technology preferred to lead-acid for Cyprus power station.
February 3, 1999 - Nickel-cadmium technology preferred to lead-acid for Cyprus power station. Alcad nickel-cadmium (Ni-Cd) batteries are being shipped to Cyprus as part of a standby power supply that will provide emergency power to the control system at the Vasilikos power station on the island. The equipment consists of duplex chargers and microprocessor-controlled distribution to provide absolute load security. PB Design chose Ni-Cd batteries because they have greater reliability over a ten-year life compared with conventional lead-acid batteries.
Lead-acid batteries can suffer from "sudden death" failure when internal components age or corrode. For this reason, nickel-cadmium batteries are usually considered a more reliable choice for critical applications such as control system back-up. They are more tolerant of extreme environmental conditions and overcharging, and in many applications have a lower total cost over a typical 20-year life than lead-acid batteries.
The Vasilikos power station emergency power supply, which will be installed during the autumn of 1998, incorporates a special charger and dual-redundant batteries, each one consisting of 92 Alcad HB705P cells. The design duty pattern requires the battery to deliver 50A for up to ten hours to provide emergency power to the control system, after which it must be able to trip various switchgear. High-discharge-rate "H" type cells were specified for the 705 ampere-hour (Ah) battery because of the high switch tripping current of up to 900A needed at the end of the duty pattern.
PB Design and Alcad engineering staff calculated the size of the battery according to the recommendations of the IEEE 1115 standard, which takes into account the effect of a prolonged float charge. Designers of standby and emergency power supplies are increasingly being asked to ensure that batteries are sized according to the IEEE standard's recommendations because it takes into account the way most Ni-Cd batteries are used in these applications, namely, infrequent discharge and "float" charging at constant voltage.
In response to this, Alcad has changed the way it presents the performance data for its industrial nickel-cadmium (Ni-Cd) cells, to show the effect of a prolonged "float" charge. A battery sizing software package for customer use, currently under development at Alcad, will also use the IEEE 1115 method in its standby power calculation module.
PB Design and Developments has also won a second major power supply contract for the Vasilikos power station, which will incorporate several different Alcad Ni-Cd batteries, ranging in capacity from 145Ah to 625Ah.
Alcad nickel-cadmium batteries are used for critical standby power applications throughout industry. Alcad will collect old batteries at the end of their life, and recycle the materials. Around 30 per cent of the cadmium in each new Alcad battery has been recycled at Alcad's own facilities. The company's products, systems and services are available worldwide through a network of sales offices and agents.
Press contacts: Reader inquiries to: Picture shows.... Alcad Contact Catharina Soderlund: tel: +46 491 68100; fax: +46 491 68110 Contact Danny Dicks: tel: +44 (0) 1628 487222; fax: +44 (0) 1628 487223.
Picture shows.... Alcad Contact Catharina Soderlund: tel: +46 491 68100; fax: +46 491 68110 Contact Danny Dicks: tel: +44 (0) 1628 487222; fax: +44 (0) 1628 487223.
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