Lightning Protection for Surveillance CamerasBy Ethan Ace, Published Aug 27, 2012, 12:00am EDT
Lightning strikes can cause significant damage and major expenses for surveillance systems. An unprotected camera hit by lightning cannot only kill the camera but lots of other devices connected to the camera (switches, recorders, etc.). In this note, we examine lightning protectors, their cost, usability, when they are needed, types to consider and how they should be installed.
Where Is It Needed?
Most commonly, integrators install lightning protection on cameras mounted near the tops of buildings, on poles, outbuildings, or other highly exposed locations. When located on a parapet mount atop a building, a camera essentially becomes a lightning rod. Cameras mounted lower on a multi-story building, they are not considered to be as exposed as higher cameras, but may still be subject to lightning-induced transient currents.
Some designers insist that lightning protection should be installed on all outdoor cameras, regardless of mounting location. However, given the cost of protectors, $50-100 per camera, which can be a ~10% increase per fixed camera, this is often not done in practice.
Checking lightning frequency maps can help make a more educated decision. Scientists track lightning strikes globally, compiling data on what area are the most prone to risk (see this world lightning frequency map [link no longer available]). Below is a detailed US map showing lightning strike frequencies:
Notice how Florida is ~16 more likely to suffer lightning strikes than NYC and how rare lightning strikes are in most of California. Reading such maps can help better gauge risks. And, of course, experience in a region with past cameras will provide an even more specific sense of the risk of lightning strikes.
Note that contrary to popular belief, lightning protection is not intended to prevent the camera or other connected device from being destroyed by lightning. If lightning strikes a camera, that camera is mostly likely going to be destroyed. Instead, the protector is intended to prevent connected electronics (switches, routers, NVRs, etc.) on the protected side from being damaged.
Types of Lightning Protectors
Lightning protectors are sold in single and multi-port configurations:
- Single-port: Protectors of this type are used for a single camera, typically located near the camera. Single-port protectors are used when only a small number of outdoor cameras are installed. Options are available for analog video over coax, IP cameras using PoE, or IP PTZs requiring UTP in addition to 12/24V power pairs. Single-port protectors generally sell for $50-100 USD online. This image shows a typical single-port protector:
- Multi-port: Multi-port surge protectors are typically capable of handling 12-16 cameras, resembling patch panels with multiple RJ45 ports. They are most often rack-mounted near network or recording equipment. Multi-port protectors are used when larger number of outdoor cameras are installed. Rack mount protectors sell for $400 and up, depending on port count and configuration. This image illustrates a typical rack-mount protector:
The single most important factor affecting lightning protectors is grounding. Without a good ground, the protector has no path to divert overage current to, rendering it essentially worthless. The surge protector should be grounded to one of the following points with a minimum #8 AWG copper wire:
- Building structural steel
- Electrical service ground
- Metallic cold water pipe
- Local receptacle ground wire
From a performance standpoint, it is normally preferable to install lightning protection closer to the camera, making the path to ground much shorter than the protected side of the cable run. If the cable run is too short, it may provide less resistance than preferred, reducing the effectiveness of the lightning protector.
Care must also be taken when installing single-port surge protectors, as electrical codes typically prohibit exposed connections in ceilings, so surge protectors must be installed in a separate enclosure. Mounting protection near the camera also requires more installation labor, as a grounding point must be found for each camera, which may or may not be readily available.
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