CLP provides power to a large area of Hong Kong, including the busy shopping and commercial districts of the Special Administrative Region. A robust, efficient communications network is therefore vital to ensure reliable power supplies.

Electric utilities need to transfer processing data in real-time between substations to support a wide range of applications, including telecontrol, security and metering and other SCADA (supervisory control and data acquisition) transmissions. Power stations send continuous measurement and status signals to control centres. Alarm signals are also sent from power stations to the control centres in case of malfunction or for security alerts.

A central network management system is vital to ensure cost effective and uninterrupted network operation by monitoring and managing all these different applications. The utility’s infrastructure also needs to support heterogeneous services for voice and data transmission (both analogue and digital), and must also be capable of remote control and signalling operations. In addition, system and link redundancy is critical in ensuring continuous operation.

China Light & Power (CLP), a utility with over two million subscribers based on Hong Kong’s Kowloon Peninsula, has deployed a comprehensive data and telecommunications access solution from RAD Data Communications that achieves all these objectives.

Minimum downtime

Located across from Hong Kong Island’s Victoria Harbour, Kowloon is one of the most densely populated places on the planet. More than two million residents crowd fewer than 50 km2. Given that many of the hotels and shopping arcades in the Hong Kong Special Administrative Region (SAR) are located there, Kowloon also attracts a hefty flow of tourists and visitors. The bright neon signs of the Nathan Road commercial district compete with each other to light up the evening sky. The uninterrupted flow of electricity to Kowloon’s consumers is, obviously, a foremost priority that obliges a dependable data and telecommunications access network that keeps ‘downtime’ to a minimum.

CLP holds the concession on Kowloon’s vertically integrated electrical generation, transmission and distribution. Its mission is to provide a safe and reliable electricity supply at reasonable cost to residential and commercial customers in Kowloon, as well as in the New Territories and most outlying islands, which together account for the bulk of the SAR’s territory and population. CLP operates three power stations, at Castle Peak, Black Point and Penny’s Bay, and it is the sole off-taker for the electricity generated at these facilities. CLP also solely owns a transmission and distribution network that is more than 10 800 km in length, along with 11 398 substations.

Figure 1. The ASMi-51 2-wire modem uses multirate single pair digital subscriber line (MSDSL) technology
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Variety applications

The RAD equipment that has been deployed provides CLP with a multiservice access solution that connects power substations throughout the utility’s concession area to its operations centre. A variety of applications are served, including the transmission of low speed SCADA and high speed data transfer, as well as Local Area Network (LAN) traffic and a limited amount of ‘hotline’ voice connections between substation technicians. Between the sites, data and voice traffic are primarily transported over leased lines, but radio links are also employed. The RAD solution incorporates 18 of the company’s Megaplex-2100 modular multiservice access multiplexers, several hundred ASMi-51 MSDSL modems and four Kilomux-2100 sub-rate access multiplexers. Supplemental access equipment will be added over the next several years as the demands of the applications develop.

The majority of the applications are point-to-point, but point-to-multipoint applications exist as well. To accommodate CLP unique communications requirements, RAD customised its ASMi-51 modem for this specific application with V24 and G703 co-directional 64 kbps interfaces. The modems also support 24 V and 48 V DC power, which was a requirement in this application.

Figure 2. The RAD equipment provides CLP with a multiservice access solution that connects power substations to its operations centre
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Network operations

“CLP provides power to the largest service area in Hong Kong, both in terms of demography and geography, and that’s a responsibility that precludes any downtime in its communications network,” explained Jeremy Zimman, director of operations for Greater China at RAD Data Communications. “The Megaplex-2100 is an ideal product for this particular application precisely because of its high reliability,” Zimman continued. “It also boasts a rapid upgrade time for software downloads with no effect on service, making it a future-proof solution for network operations, especially if feature enhancements are to be introduced at a later date.”

RAD’s multiservice solution is an integrated access platform that performs both multiservice traffic groo-

ming and concentration. The products employed in this solution maximise use of the access infrastructure to reduce operating expenses and enable fast payback of equipment outlays. They also help enterprise users like CLP reduce communications expenses and build affordable private networks that address specific applications and bandwidth needs. The equipment is also well suited to easily withstand the rigours of Hong Kong’s hot and humid climate in the spring, summer and autumn. All RAD products are tested to be heat resistant to temperatures as high as 70°C, whether under direct sunlight or in locked, unventilated cabinets.

The Megaplex-2100 multiservice access multiplexer is a flexible, modular product that enables the integration of a wide range of multiple voice, data, LAN and even video services directly over four full E1/T1 links per chassis. The Megaplex splits the voice and data channels and redirects the traffic to separate trunks, maximising efficiency by directly connecting each trunk to the appropriate service. The product offers high port density and a wide variety of analogue and digital voice connections – including PCM, ADPCM, G.723.1, BRI ISDN and digital E1 interfaces for a variety of network architectures, including resilient failure-safe ring and star topologies. Tail-end modems and up to four E1/T1 main link ports with built-in digital cross connects can distribute different services over the same infrastructure or split them at the carrier’s point of presence (POP). The Megaplex is especially suitable for use at substations as an economical, compact remote distribution node. It is standards compliant, ensuring compatibility in multivendor environments. The control and monitoring needed in large networks is provided by the HP OpenView-based RADview network management.

The ASMi-51 2-wire modem extends the data transmission range by using multirate single pair digital subscriber line (MSDSL) technology. MSDSL provides an extended transmission range of up to 8.2 km. The product supports integrated voice and data and offers 15 different data rates for symmetrical transmission from 64 kbps up to 2.048 Mbps. MSDSL’s scalability up to E1/T1 rates enables bandwidth usage to be increased in the future without any additional cost. Moreover, MSDSL has less than half a millisecond framing delay. The delay factor is essential for voice, alarm, and the other delay-sensitive applications that are so typical in the power industry.

Figure 3. The uninterrupted flow of electricity to Hong Kong’s bustling commercial and residential districts is a priority for CLP
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Modular construction

The Kilomux time division multiplexer provides an efficient and cost-effective solution for integrating data, voice, fax and LAN traffic over digital data services, leased lines, IP, ISDN and other services. Access to the various services is provided over a variety of standard interfaces at data rates ranging from 9.6 kbps to 1.536 Mbps. The modular construction of the Kilomux is ideally suited to implement system designs according to specific applications and to provide easy upgrading. The redundant power supply and link interface options increase system reliability.

The Kilomux maximises bandwidth utilisation through low overhead, which, together with voice compression, ensures quality of service. If it is to run effectively over data circuits whose speed is substantially less than that required internationally for toll-quality voice transmission, the voice signals must be compressed. Aided by echo cancellers and powerful processors that ameliorate the effects of transmission delay, voice compression fully enables the integration of voice and data over what would otherwise be pure data networks. For utilities like CLP Power, data-voice integration reduces communications costs and helps meet the ever-increasing demand for extra bandwidth capacity.

Macroview Telecom, a RAD distributor partner in Hong Kong, provides installation and commissioning services to CLP for this project.