Lightning Problems

[Gator1]

Steve:
I manage a telecommunications program for a federal government customer. We are using telecommunications hardware from Dialogic (DMV and HDSI PCI boards) to provide outbound local and long distance calling services. I have systems deployed nationwide. Our PBX is providing dial tone to phones in multiple locations of a campus-like environment. We have installed 75V surge supression devices manufactured by CIRCA that are housed in a 3M 4688 Entrance Terminal between the 66 block and the Dialogic Station Interface Box (SIB). There is a grounding cable from teh Entrance terminal to the building ground rod in the phone room. My problem is that lightning has repeatedly blown stations on numerous SIBs over the past six months in multiple locations around the country. I need help resolving this issue.
thanks.

 

[quogueelectric]

Google Heary brothers

Google Heary brothers

Call them and they should be able to help you/.. It is not going to be cheap however.

 

[don_resqcapt19]

Is the building ground rod in the phone room tied to the electrical grounding electrode system?
Don

 

[EV607797]

My concern is that you are using 75 volt modules for station port protection. Aren't these ports carrying traditional ringing voltage? In using 75 volt modules where perhaps 96 volt ringing current is present, you are effectively shorting the ring voltage to ground which will certainly place undue stress on the station line circuits on the cards. Most systems use ringing voltages between 77 and 105 volts AC at 30 Hz.

The 3M terminals should be equipped with primary protective devices, such as gas tube modules. These terminals and modules are designed to provide property and personnel protection only. These should be bonded to the building's EGC in accordance with NEC requirements. These tereminals should also be located as near as practical to the cable's entry point into the building. Also, the aluminum shield of the cable's jacket must be bonded using an appropriate sheath bonding clamp (3M #4462 for example) to the harness included inside the 4688's incoming splice chamber.

Most modules rated at 75 volts and below aren't designed to provide property and personnel protection. They are not capable of withstanding direct hits or simply surges associated with lighting activity. For a properly-installed telecommunications protection system, you must have primary AND secondary protection means installed.

Behind the primary protective devices, and prior to connection to the station line circuits, secondary protection should be installed. These should be installed as close as practical to the PBX itself. Typical units would be those made by Porta Systems, ITW Linx, etc. These units ARE designed to provide the appropriate protection of the electronics associated with the line card ports. There are also options in these modules that will provide sneak current protection which is likely the cause for the failures that you are experiencing.