Traffic Signal Light

Overview of ITS Cabinet

The ITS cabinet hosts many components needed to operate local intersections, control signs and ramp meters. Reliability is necessary to ensure safety of drivers as well as pedestrians. With the growing demand and more equipment is being inserted into the traffic cabinet.

Threat to ITS Equipment

A "dark" intersection is the worst case scenario for traffic signal cabinet. The interruption of power can be caused by transients which affect sensitive components within the cabinet. As a result of the disruption of power, drivers and pedestrians are placed at risk. Although traffic cabinets may use a SPD to protect the system, if the SPD is series installed using a internal fuse upstream for additional protection, the SPD itself can cause the loss of power.

Traffic at Main Intersection

Solutions for ITS Cabinets

CITEL recommends the use of parallel installed SPDs, to ensure that once the SPD reaches the end of life scenario it will not cause the power loss. This reduces the risk of the "dark" intersection. Surge protection plays a vital role in preserving the integrity of equipment and, more importantly, protecting the lives of personnel.

The installation of Surge Protective Devices (SPDs) within the ITS Cabinet is a measure that will not only extend the life of the circuit components but also increase the reliability of the system as a whole.

Selecting an SPD for ITS Cabinets

NEC/NFPA 70 require that Surge Protective Devices (SPDs) shall be UL1449 Listed . This means selecting a surge protector is easier than it has ever been. There are only a few choices available for SPDs that are UL Listed for any of the most commonly used surge standards including UL1449 5th Edition, UL497B, and UL497E, in addition, only UL Listed Surge Protectors are acceptable for facilities that will install a Lightning Protection System (LPS) certified to either NFPA 780 or the UL96A Master Label.

Recommended SPD for Main Service Panel

Location	Equipment	System	Surge Protector Model#	Link
	Main Service Panelboard	120/240Vac	M50-120T-A

Recommended SPD for ITS Cabinet

Location	Equipment	System	Surge Protector Model#	Link
	Power Panel	120Vac	DS72US-120S/G-F-ASSM
	Cabinet Power Supply	120Vac Power Input	DS72US-120S/G
	Cabinet Power Supply	24Vdc Cabinet Power Supply Output	DS220S-24DC
	Cabinet Power Supply	12Vdc Cabinet Power Supply Output	DS220S-12DC
	Vehicle Detection Camera	POE+	MJ8-POE-C6A
	Serial Interface Unit (SIU)	24V	DD25-24V

References