Electrical Surge Protection - Tower Site

With the presence of a communication tower, the potential for damage to sensitive electrical equipment is increased both from direct and nearby lightning activity since the tower acts as a lightning rod and the antenna feeds from the tower provide a means of surge entry into the building.  In addition, surges may enter through the normal power system and signal/data lines such as cable, phone, satellite and LAN or DSL feeds.  A review of the current controls should be conducted to assure that the risk to equipment, property and personnel is limited.

As a general guideline, the control of surge exposures is a three-step process.  The first key to reducing this exposure is to ensure that the building has a single point grounding system – that is, all earth ground connections within the building are properly bonded together (tower, RF coax, CATV, phone, AC power, etc.).  The second key is to ensure that the grounding system offers a low-resistance path to ground.  Code requirements typically specify a level of 25 Ohms of resistance or less, but the recommended practice where sensitive equipment is involved is generally 5 Ohms.  Your local power supply company should be able to provide you with code requirements for your area and may be able to test the current resistance level on your grounding system.  If not, your radio or communications tower vendor may be able to help out. 

The third key is the use of surge protection devices (SPDs) for AC power conductors and low voltage signal lines, such as phone, data, CATV and radio coax.  Protection against AC power surges should begin at the main panel and work down to the individual piece of equipment with a plug-in SPD.  As a general rule, we recommend plug-in SPDs should have a visual indicator to show that it is functioning properly, built in short circuit protection, a correct wiring indicator (for the outlet into which it is plugged) and be UL 1449 listed (3rd ed.).  Many of the retail units sold as surge protection are actually listed as a multi-tap outlet and do not meet the more stringent testing and performance requirements of a true SPD. SPDs for the electrical distribution system should be listed by an approved testing agency such as UL, and should be designed/selected for the surges that they will be expected to handle and installed by a qualified contractor.  Low voltage signal lines require SPDs that are specifically designed for the type of signal they handle.  These SPDs should be located as close to the line’s entry point as possible and have a short, direct and properly-sized grounding connection.  The vendor or service provider for each system using a low-voltage signal line should be able to assist you in selecting and installing the proper SPD.