Surge Protection for Weigh In Motion Systems (WIM)

Fleet of trucks on a highway.
Weigh In Motion System

Overview of Weigh In Motion Systems

The Weight In Motion systems (WIM) operate on municipal roads, federal highways and bridges. Reliability is necessary to ensure safety of drivers by keeping roadways from overstress, vehicles entering and exiting to weigh stations and the cost of the weigh station itself. With the growing demand and more equipment is being inserted into the remote cabinets, they are very susceptible to damaging overvoltages resulting from lightning strikes and switching transients.

Truck passing over in motion weight station.

Threat to WIM Systems

These are exposed applications that face a very significant threat from direct (conducted) and indirect (induced) effects from lightning strikes. The damage can be caused by a variety of source transients which affect sensitive components within the cabinet and connected in the network. As a result of the disconenction of vital equipment, places drivers, roads and critcal operations are placed at risk. It is important to develop a surge mitigation strategy like the box concept. Simply draw a box around the roadside equipment cabinet and any wire that enters or exits the box is vulnerable to transient surges. Place a Surge Protective Device (SPD) at each vulnerable point to ensure equipment is safe and protected.

Weigh In Motion System
WIM Sensor

The solution for Weigh In Motion Systems

CITEL recommends the use of parallel SPDs for the AC input, to ensure that once the SPD reaches the end of life scenerio it will not cause a power loss and thus keeping equipment connected. This reduces the risk of down-time resulting in loss of revenue and frustration among users. 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 Roadside Equipment 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 Weigh In Motion Systems (WIM)

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

LocationEquipmentSystemSurge Protector Model#Link
Main Service Panelboard120/240Vac M50-120T-A M50-A

Recommended SPD for Roadside Equipment

LocationEquipmentSystemSurge Protector Model#Link
Roadside Equipment
120Vac AC Input DS72US-120S/G-F-ASSM

Power Supply120Vac
AC Power Input
DS72US-120S/G DS72US-120S/G

DC Power Output
to Data Logger
DS220S-24DC DS220S-24DC

Ethernet SwitchEthernet Cat 6A MJ8-C6A MJ8-C6A

Vehicle Detection CameraPOE+ MJ8-POE-C6A MJ8-C6A

Serial Interface Unit (SIU)24V DD25-24V

Contact us to develop a surge mitigation solution for your application

Where to purchase Citel SPD's


1ANSI C62.41, Low-Voltage AC Power Circuits
2UL1449 4th Edition, Surge Protective Devices
3UL1449 5th Edition, Surge Protective Devices
4UL497B, Surge Protectors for Data Lines and Fire-Alarm Circuits
5UL497E, Antenna Lead-in Conductors
6IEC 61643-11, Low-Voltage Surge Protective Devices - Part 11: Surge Protective Devices Connected To Low-Voltage Power Systems - Requirements And Test Methods
7IEC 61643-21, Low Voltage Surge Protective Devices - Part 21: Surge Protective Devices Connected To Telecommunications And Signalling Networks - Performance Requirements And Testing Methods
8IEC 61000-45, Electromagnetic Compatibility (EMC) - Part 4-5: Testing And Measurement Techniques - Surge Immunity Test
9CSA 22.2
10NOM-001-SCFI, Standard for Electronic Equipment
11NOM-003-SCFI, Electrical Products - Safety Requirements