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Case Studies

WSD - Hong Kong

David Au, Engineering Manager of Multi Premium Engineering Ltd, says “We have an excellent working relationship with SSL, who have considerable experience and knowledge of the Brush Switchgear range of equipment.  In addition to being able to provide a complete range of spares, modifications and retrofits for this equipment, they provide an invaluable technical back up support service to assist ourselves and our customers”.

The Water Supplies Department (WSD) in Hong Kong is the only Government owned authority to provide potable water to the whole area with approximately a 7.5 million population. Their main task is to provide a reliable and adequate supply of wholesome potable water and sea water to the community in the most cost-effective way. 

The department also plans and maintain water resources, prepares outline proposals for new water supply schemes and improvements to the existing system to meet growth of demand in existing and developing areas, monitors the adequacy of water resources and installations and collates hydrological information necessary for the management and development of the waterworks.  They have built a very large pumping station to feed water to cover every part of Hong Kong.  The water pumps are mostly rated at 3.3kV and 11KV due to the large power ratings required.

The WSD network grew rapidly in the 1980’s and has an extensive HV network, comprising several hundred HV panels.  Many of these panels are Direct-On-Line (DOL) motor starters, at voltages from 3.3kV-11kV.  Traditionally, oil based switchgear was installed, followed by SF6 switchgear as oil manufacture was phased out, as WSD believed these were better suited to motor switching duties (less likelihood of transient voltages damaging the HV motors).  

In the late 1990’s, WSD recognise the limitations of their oil based switchgear in terms of increased maintenance (especially circuits that involved frequent switching), obsolescence of spares, loss of experienced personnel and the general trend towards removing oil from HV networks.  From the onset, we have been involved in providing guidance to WSD on the use of vacuum circuit breakers (VCBs) for High Voltage DOL motor starting.  They were particularly concerned, as are most customers with High Voltage motor applications, that motors in excess of 25 years old could be prone to insulation damage by the opening and closing operations of VCBs.  Approximately ten years ago, WSD finally accepted the use of VCBs on the understanding that surge arresters were supplied as part of the retrofit package.

As you would expect, the WSD has an onerous specification in terms of acceptable current chopping values (which are generally higher when switching inductive loads) and maximum permissible switching overvoltages.  Switchgear Support Ltd (SSL) have considerable experience in the retrofitting of the Brush Switchgear VSI range and in the design, supply and installation of surge arresters in this application.

It was therefore a natural progression that WSD would continue the phased replacement of their Brush Switchgear VSI OCBs, with the VCBs and surge arresters being supplied by SSL in conjunction with our local partner, Multi Premium Engineering Ltd, who conducted the installation and commissioning.

Dave Johnson, Director of SSL, says“Following numerous visits to Hong Kong, we have built a very strong relationship with our partner, Multi Premium Engineering Ltd, and our client, the WSD over the past 15 years.  We have a very clear understanding of their specification and ensure that our certified VCBs and surge arrester package are tailored exactly to meet WSD’s requirements”

Photos courtesy of the Water Supplies Department