Surge Protection for ITS Cabinets
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| Traffic Signal Light |
Overview of ITS Cabinets
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.
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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 Surge Protective Device (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.
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| 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 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 UL 1449 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 UL 1449 5th Edition, UL 497B and UL 497E. 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 UL 96A Master Label.
Recommended SPD for Main Service Panel
| Location | Equipment | System | Surge Protector Model# | Link |
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| Main Service Panelboard | 120/240 V ac | M50-120T-A |
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Recommended SPDs for ITS Cabinet
| Location | Equipment | System | Surge Protector Model# | Link |
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| Power Panel | 120 V ac | DS72US-120S/G-F-ASSM |
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| Cabinet Power Supply | 120 V ac Power Input | DAC102US-120S |
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| Cabinet Power Supply | 24 V dc Cabinet Power Supply Output | DS220S-24DC |
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| Cabinet Power Supply | 12 V dc Cabinet Power Supply Output | DS220S-12DC |
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| Vehicle Detection Camera | POE+ | MJ8-POE-C6A |
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| Serial Interface Unit (SIU) | 24 V | DD15-24V |
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References
| # | Title |
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| 1 | ANSI C62.41, Low-Voltage AC Power Circuits |
| 2 | UL1449 4th Edition, Surge Protective Devices |
| 3 | UL1449 5th Edition, Surge Protective Devices |
| 4 | UL497B, Surge Protectors for Data Lines and Fire-Alarm Circuits |
| 5 | UL497E, Antenna Lead-in Conductors |
| 6 | IEC 61643-11, Low-Voltage Surge Protective Devices - Part 11: Surge Protective Devices Connected To Low-Voltage Power Systems - Requirements And Test Methods |
| 7 | IEC 61643-21, Low Voltage Surge Protective Devices - Part 21: Surge Protective Devices Connected To Telecommunications And Signaling Networks - Performance Requirements And Testing Methods |
| 8 | IEC 61000-45, Electromagnetic Compatibility (EMC) - Part 4-5: Testing And Measurement Techniques - Surge Immunity Test |
| 9 | CSA 22.2 |
| 10 | NOM-001-SCFI, Standard for Electronic Equipment |
| 11 | NOM-003-SCFI, Electrical Products - Safety Requirements |
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SPDs for ITS | |
