8Multidisciplinary projects#
Addition of guidelines to consider for multidisciplinary projects to enhance electrical safety optimise design by combining systems where appropriate and reduce cost.
8.1Introduction#
The requirements of Sections 2, 3 and 4 are typical for road lighting, traffic signal and ITS installations when each is required as an individual system; however, on projects that consist of all three systems, additional considerations are required to optimise the design and provide a higher level of safety for maintenance personnel.
The following guidelines should be considered in the design.
8.2Electrical design#
Points of supply should be negotiated to minimise the actual number of connection points to the Electricity Entity network while addressing cable sizes and lengths, centres of load, and convenient locations for switchboards.
Drawings should show general boundaries within which electrical equipment is connected to the same point of supply.
Site wide single line drawings showing the Electricity Entity connection points clearly labelled and the integrated services connected to each point should be provided up to and including each switchboard, traffic signal controller and ITS field cabinet. Switchboards for the different disciplines should be located together wherever practicable, ensuring accessibility and maintainability. ITS and traffic signals may be serviced by the same link switchboard connected to the electricity network to minimise the number of connection points. Switchboards must be clearly labelled to differentiate usage. Switchboards, traffic signal controllers and ITS field cabinets should be clearly labelled with source of supply designation.
8.3Conduit and pits#
Using the requirements for individual road lighting, traffic signals and ITS can result in excessive overcapacity of conduits and pits in multidisciplinary projects, particularly where systems are running in parallel. At signalised intersections, the standard traffic signal installation should be used with only signals cables and road lighting cable for JUPs and CMAs within the signals conduits. This will also help minimise the number of pits in the already limited real estate of the intersection. Other cables should bypass the intersection as much as practicable to minimise intersection congestion and aid in construction and ongoing maintenance. Using combined road crossings for road lighting and ITS can minimise the conduits to two electrical and two communications, particularly if cable usage is accommodated adequately, as well as saving on pits. Where there are parallel road lighting and ITS conduit runs, consideration should be given to making the electrical conduits common use and optimising the overall numbers of conduits to suit the current cable design as well as allowing adequate capacity for potential future growth. This needs to be considered on a case-by-case basis as some areas may need more future-proofing than others. As the trend in communications cabling is away from copper and towards fibre, the spare capacity of communications conduits needs to be seriously considered.
8.4Presentation drawings#
On multidisciplinary projects, it is essential that integrated electrical single line drawings, clearly showing all the disciplines together, are provided. An overall single line drawing detailing where all connections to the electricity network are located, including transformer size and Electricity Entity identifier, and how switchboards and other major electrical equipment are supplied, improves the electrical safety of the installation. Also, the time for fault finding in the case of an outage can be reduced, allowing essential services to come back online with a minimum of delay. A combined set of road lighting, traffic signal and ITS pits, conduits and footing location drawings should be provided. This can greatly assist the constructor while providing Transport and Main Roads with one document to review the underground services. As this set would consist of electrical equipment, it is required that signoff would be by an electrical RPEQ. Where road lighting pole footing locations are being shown on a combined set with conduits and pits, road lighting design must be part of the road lighting drawings.