2Road lighting requirements#

2.1Introduction#

Refer also to Section 1.

The objective of road lighting is to provide an illuminated environment, which is conducive to the safe and comfortable movement of vehicular and pedestrian traffic at night, and the discouragement of illegal acts (AS/NZ 1158 Lighting for roads and public spaces).

Where lighting has been installed on roads, it has been deliberately designed to achieve the objectives of AS/NZ 1158. The electrical system is an integral part of maintaining the illuminated environment.

Consequently, road lighting design must balance the electrical safety requirements with traffic safety requirements. Every effort must be made to ensure that the lighting installation remains operational, safely.

There are four main unmetered lighting tariffs available for public area lighting:

• Rate 1 Lighting: Public lighting supplied, installed, owned and maintained by the Electricity Entity. Electricity Entity design requirements are applicable.
• Rate 2 Lighting: Public lighting supplied and installed by a Public Body, owned and maintained by the Electricity Entity. Electricity Entity design requirements are applicable.
• Rate 3 Lighting: Public lighting supplied, installed, owned and maintained by the Public Body. Public Body and AS/NZS 3000 design requirements are applicable.
• Rate 8 Lighting: Public lighting supplied, installed, owned and maintained by a customer who is not a Public Body. Customer and AS/NZS 3000 design requirements are applicable.

For Queensland, the Electricity Entities are Energex and Ergon, now known as Energy Queensland.

The Public Bodies are Transport and Main Roads and local Councils.

It is essential during the early stages of a road construction project involving road lighting that representatives of Transport and Main Roads, the local Council (if applicable) and the local Electricity Entity agree on the ownership of the relevant parts of the final lighting installation and the applicable standards to be used; then the design can be carried out in accordance with the appropriate requirements.

Rate 3 road lighting should typically be restricted to motorways, motorway entry and exit ramps up to the intersection, the motorway overpass between entry / exit ramp intersections, and state-controlled high-speed / high-volume roads where the Electricity Entity will not maintain the installation.

2.2Design philosophy#

Electrical designs must consider the most effective means of providing safe and reliable road lighting.

For single phase, the two-wire multiple earthed neutral (MEN) system must be used. For three-phase, the four-wire MEN system must be used. The steel reinforced concrete pole footing embedded directly in the soil is the earth electrode.

For lighting installations on bridges and structures, a separate earth conductor of minimum size equal to the cross-sectional area of the active conductor, must also be installed with the two-wire or four-wire cable (refer to SD1707 Road lighting – Base plate mounted pole mounted on bridges wiring details).

Where three-phase circuits are used, the luminaire load must be balanced across the phases as evenly as possible. The electrical connection for luminaires must be such that, in a three-phase connected system, luminaires on adjacent poles must not be on the same phase.

In critical areas, such as motorway entry and exit ramps, three-phase circuits should be used.

2.3Electrical design requirements#

Electrical designs must consider the most effective means of providing safe and reliable lighting.

2.3.1Design voltage and frequency#

The design voltage is 230 V ac.

The design frequency is 50 Hz.

2.3.2Design current and power factor#

Manufacturers’ data must be used for the selected luminaires. The following design currents at 0.85 power factor must be used for the high pressure sodium luminaires.

The design currents that must be used for LED luminaires are included in TN158.

2.3.3Design spare capacity#

The consumers’ mains, submains and sub-circuit design must optimise both the available earth fault loop impedance (EFLI) and voltage drop. Unless otherwise specified in the project-specific requirements, or as follows, no spare design capacity is required.

2.3.4Maximum demand#

The maximum demand for each road lighting cable will be the connected load, unless otherwise directed. The running current on any HID lighting circuit must not exceed 80% of the fuse rating. The running current on any LED lighting circuit must not exceed 50% of the fuse rating.

2.3.5Discrimination#

As road lighting is a road safety system, it is essential that any electrical fault is cleared by the protection closest to the fault, while leaving other parts of the installation operational. The Electricity Entity fuse at the point of supply is normally 80 A. The fuse in the switchboard at the start of the submains cable is rated at 20 A, 25 A or 32 A depending on the circuit maximum demand. The fuse in the re-openable joint adjacent to the road lighting pole is rated at 10 A. With this configuration discrimination is achieved for both overload and short-circuit faults for high rupture capacity (HRC) fuses complying with AS 60269.

2.3.6Disconnect time#

Clarification of the types of equipment and relevant disconnect times.

The maximum disconnect time for fuses protecting cables (including consumers mains cables) directly connected to metal-enclosed electrical equipment (that is, top mounted switchboards, metered switchboards, road lighting poles, structure mounted underpass lighting, and the like) is 400 ms.

The maximum disconnect time for fuses protecting cables (including consumers mains cables) directly connected to non-metal, insulated enclosed electrical equipment (that is, pillar mounted switchboards, dome junction box adjacent to a light pole, and the like) is 5 s.

2.3.7Cable operating temperature#

Cable operating temperature standardised to 75°C for all cable calculations.

The cable operating temperature of 75°C should be used in all cable electrical calculations.

2.3.8Voltage drop#

Total voltage drop in road lighting circuits must allow for consumers mains, submains and sub-circuit voltage drops including spare design capacity where required, the sum of which must be no greater than 5%, using the maximum demand currents. Length of cable used in calculations must include a 2 m coil at each end of each cable segment to allow the re-openable joint to be lifted clear of the pit for maintenance. In a three-phase design, as the lighting load is reasonably balanced across the phases, use a balanced three-phase voltage drop calculation. Voltage drop calculations must be carried out for the worst case run of each circuit connected to the switchboard. Voltage drop in the consumers mains must be based on the higher of 40 A or the actual connected load up to the maximum allowable of 63 A. Refer also to Section 7.

2.3.9Earth fault loop impedance#

EFLI calculations must be carried out to demonstrate that the design is compliant for the worst-case protection and cable length for each of consumers’ mains, submains and final sub-circuits. The assumed ratio of 20% external and 80% internal impedance has been found not to be valid for road lighting installations and must not be used. Obtain the supply transformer and distribution cable parameters from the Electricity Entity and include these in the calculations. Where exact network data are not available or measurement of supply characteristics is not practicable, the designer must make an assessment of the relevant parameters and clearly document these in the design calculations. Refer also to Section 7.

2.3.10Point of supply#

Points of supply must be agreed with the Electricity Entity to allow the Electricity Entity to carry out any necessary network modifications. Where practicable, road lighting and traffic signals should be connected to different points of supply. Traffic signal controllers must not be connected to road lighting switchboards. Road lighting circuits must not be connected to a traffic signal controller.

ITS circuits may be connected to road lighting switchboards on separate fuses upstream of the lighting contactor.

Unless otherwise agreed with the Electricity Entity, consumers' mains (distance from point of supply to switchboard) should be no longer than 30 m.

2.3.11Switching of road lighting#

In automatic mode, road lighting submains are activated by a standard photocell, located on the top mounted or metered switchboard or on a pole adjacent to the pillar mounted switchboard, which controls contactors at the start of each circuit. A Day / Night (photocell bypass) switch provides manual or photocell operation; hence, submains are live only under manual operation or at night time. The photocells are designed to fail in the 'On' mode.

Control of individual luminaires by a photocell within the luminaire is not acceptable on Transport and Main Roads Rate 3 installations (note: should a Central Management Lighting Control System (CMLCS) be installed with the lighting, this requirement may not be applicable; this is to be confirmed with the Director (Intelligent Transport Systems and Electrical)).

2.3.12Road lighting on bridges or over railway structures#

The bridge cables must be connected to the first pole off the bridge on the supply side in accordance with SD1707 Road lighting – Base plate mounted pole mounted on bridges wiring details.

Where a bridge passes over a railway overhead wiring network, the lighting equipment may need to be bonded to the railway traction earthing system. This system and the MEN earthing system need to be segregated (note that lighting installations in the vicinity of railway traction systems may require isolation transformers). Liaise with the rail system owner and the local Electricity Entity for its particular requirements.

2.3.13Road lighting on underpasses#

Where lighting is mounted on underpasses and similar structures, refer SD1637 Road lighting – Underpass lighting wiring details. Note that a 400 ms disconnect time is required for lights mounted on underpasses and structures.

Typically a two-core 4 mm² cable with a separate 6 mm² earth is required. Alternatively, single-core 4 mm² cables with 6 mm² earth may be used.

2.3.14Road lighting and traffic signals#

Where Rate 3 road lighting is connected on a JUP or CMA, design in accordance with SD1677 Traffic signals / Road lighting – Joint use pole / combination mast arm electrical wiring schematic Rate 3.

2.4Electrical components#

2.4.1General#

Refer to SD1699 Traffic signals / Road lighting / ITS – Parts list, which provides details of standard electrical equipment items. Items approved by ITS and Electrical must be used.

2.4.2Switchboards#

Metered and unmetered switchboards available for road lighting.

Road lighting switchboards are:

Use top mounted or metered switchboards to MRTS228.

Only where the Electricity Entity network characteristics are such that the 80 A fuse will not activate within 400 ms to clear an active-to-earth fault at the top mounted or metered switchboard may a pillar mounted switchboard be used; however, this should be used only when other cost-effective design options are not available.

The road lighting switchboard is built with three, three-phase circuits with space for an additional two, three-phase circuits (or single-phase equivalent). To minimise the loss of operations in the event of a failure, the maximum number of circuits per switchboard is five, three-phase or equivalent number of single-phase or combination of single- and three-phase circuits. The additional circuits are typically used for low wattage ITS equipment.

The maximum connected load for road lighting switchboards must not exceed 63 A three-phase.

2.4.3Main switch#

The main switch must be a labelled, three-phase switch disconnector, lockable in the open position, with minimum utilisation category AC 22 A, 100 A capacity, and complying with AS/NZS IEC 60947.3.

2.4.4Fuse switches and fuselinks#

Electrical protection for road lighting circuits must be provided by single- or three-phase fuse switches complying with AS/NZS IEC 60947.3, with minimum utilisation category AC 22A, complete with HRC fuselinks complying with AS 60269 and utilisation category gG.

Use only the standard fuselinks as follows:

Do not use fuselinks with ratings less than 10 A for road lighting.

2.4.5Switch disconnectors#

Within each slip base and base plate mounted pole a double pole 20 A switch disconnector, with minimum utilisation category AC 22 A, complying with AS/NZS IEC 60947.3 must be installed between the incoming cable and the 2.5 mm² luminaire cable.

2.4.6Residual current devices#

RCDs must not be used in road lighting circuits. Nuisance tripping with consequent failure of the lighting system can be a greater hazard to road users than the potential leakage current.

Protection for persons is provided by:

• designing for a 400 ms disconnect time at the pole, and
• periodic monitoring and maintenance of the network.

Refer also to Section 5.

2.4.7Photocell#

Photocells must have low power consumption, have UV-stabilised window, be minimum IP56 rated, be suitable for switching HID and LED luminaires, suitable for mains operating voltage, and with recommended switching levels 30 lux ± 25% ON and 18 lux ± 25% OFF.

2.4.8Contactors#

Contactors complying with AS/NZS IEC 60947.4.1 with minimum utilisation category AC 5a, enclosed rating 32 A minimum, coil 240 V ac, must be used to control lighting circuits.

2.4.9Earth and neutral bars#

Earth and neutral bars must be suitable for 25 mm² cables.

2.4.10Cables#

For standard road lighting cables, refer MRTS256.

Cables up to and including 6 mm² must comply with AS/NZS 5000.2.

Cables 16 mm² and larger must comply with AS/NZS 5000.1.

Direct buried cables, SDI cables (except as noted previously), neutral screened cables, steel wire armoured cables, and the like must not be used for road lighting circuits.

Cables, where installed underground or surface mounted, must be installed in an electrical conduit and pit system.

Where large size cables are used, particularly on long consumers’ mains runs, the cables may be joined to a suitably sized tail:

• within the switchboard, and
• using a suitable (minimum IP67) waterproof joining method in the pit

2.4.11Conduits and pits#

Conduit for both electrical and communications systems must be heavy duty UPVC or high density polyethylene (HDPE) complying with AS/NZS 2053 or AS/NZS 61386.

Where there is no specific design for ITS equipment included in the project, road crossings and concrete barriers must include communications conduits and pits / barrier voids for future use.

Where conduit is installed above the ground and subject to potential damage, for example surface mounted in a pedestrian underpass, the conduit shall be suitably protected with a metal guard, or rigid or flexible metal conduit complying with AS/NZS 2053 or AS/NZS 61386 shall be used.

The following table details the conduit and pits requirements for road lighting installations:

2.5Design documentation#

In addition to the requirements of DDPSM, for each design submit to Transport and Main Roads, a copy of the electrical design calculations, and an Electrical Design Certificate completed and certified by a practising profession electrical engineer currently registered with the Queensland Board of Professional Engineers (RPEQ).

The calculation sheet must clearly show all design inputs and calculation results, along with compliance check so that the design can be easily verified. Include the following:

• project name / description
• lamp / module type installed (for example, S250, L175)
• lamp / module currents used in calculations
• cable operating temperature used in calculations
• segment identification (for example, station 1 to 3)
• segment cable size (for example, 16 mm²)
• segment cable route length
• segment current
• segment voltage drop
• total voltage drop per phase
• total load current per phase
• circuit protection fuselink value (that is, 20 A, 25 A, 32 A)
• Electricity Entity network data used, including consumers’ mains fuse and disconnect time, measured external EFLI, or assessment data used (indicated as assessed), and
• calculated total EFLI at the end of the longest run of each circuit including external EFLI.

2.6Schedule of road lighting design information#

The following information must be completed by Transport and Main Roads and included in road lighting tender documentation for electrical design: