6.17Practical applications#

6.17.1General#

For any particular installation, a risk analysis should first be carried out. This should provide a good assessment of whether surge protection is required. The particular type of SPD that would provide appropriate protection can then be selected. The appropriate SPDs can then be specified. Particular attention then needs to be paid to the installation of the SPD and the earthing system. The SPD needs to be provided on each copper cable at the boundary of the equipment to be protected.

The following provides some guidance on particular Transport and Main Roads applications:

6.17.2Road lighting#

A MOV SPD is installed within the luminaire to protect the control gear. No further protection is generally required for standard road lighting installations.

6.17.3Traffic signals#

The TSC4 controller has a MOV SPD with IN rated at 20 kA and voltage protection level of <1450 V. No further protection would generally be necessary.

6.17.4Roadway CCTV installations#

Roadway CCTV installations would generally be expected to require surge protection on the power supply and copper communications cables, both at the camera and at the pole mounted equipment or the field cabinet and at the pole mounted equipment or field cabinet and external connections. Power and communications SPDs should be installed close together, if not in a combined unit, to ensure that the earth leads are very short. Good earthing is critical.

6.17.5Field cabinets#

Where fibre optic cables are used as the communications medium between field devices, no surge protection is required on the communications lines.

Where copper cables are used as the communications medium, the SPD appropriate for the particular cable and protocol is recommended at both ends of the line.

A power SPD is recommended on the power circuit at the entry to the cabinet.

In general, the SPD device is required on every copper cable that enters the field cabinet.

6.17.6Variable message signs on gantries#

Gantry mounted variable message signs would generally require a power SPD on the incoming power supply, and incoming communications if it uses copper medium. Communications SPDs would generally be required on both ends of communications cabling between the controller and the light modules. Power supply at the light modules may also need protection.