Re: Isolated ground plane
Ron, isolated ground planes are still in use today by switching equipment manufactures like Nortel, Lucent, Erricson, and Alcatel.
You are correct about the corruption problem, all the manufacture require a dedicated battery plant and MGB for their equipment, and only their personnel to install or modify the equipment to insure isolated ground plane integrity.
Each piece of equipment once delivered has a low and high voltage test performed after mounted to the floor. First a DMM is used to check for isolation between the battery return terminals and the equipment frame. It must be 2M-ohms or higher. Second the DMM is used to measure isolation between the equipment frame(s) and the MGB, again 2M minimum requirement. Third is the low voltage passes then a meggar is used on the bottom of the frame to prevent damage and isolation is again checked between the equipment frame and the local MGB. Only after the test are passed are the equipment frames connected to Frame Ground Bar fed from the MGB. Finally after all the equipment is turned on, connected, and commissioned, an clamp-on amp meter is used at various strategic points to confirm isolation by checking for any DC or AC current flow.
AS for the rest of the equipment in the office like transmission, multi-plexers, radios, etc they may be installed in their own isolated ground plane or integrated ground plane. Each telco has their own methods. One I currently use is similar to the test described above, and I use what is called a "Ground Fault isolation Monitor". The monitor is nothing more than a remote sensitive clamp on meter connected to a box with a readout, visual and audible alarms so if a corruption occurs during installation a loud horn sounds and scares the crap out everybody.
In cellular radio sites, IGZ is a must to prevent lightning currents from flowing in the equipment. Lightning is guaranteed to strike a cell site multiple times. Since the sites are small, built in a factory, IGZ is fairly simple to maintain.
Now the strangest thing happening with new VOIP equipment manufactures like CISCO and NORTEL, they are going back to the days of old using integrated ground planes with a new twist. They intentionally multi-ground the battery return circuit inside the equipment. This coupled with bonding everything (raceways, AC panels, cable ladder, SRG, water pipes, HVAC ducts, multiple connection to ground ring, multiple connection of equipment frames) causes DC load current to flow through everything in the building. I see real problem like holes in water pipes and corroding structural steel.
One manufacture in paticular, CISCO, insist there equipment be mounted on a conductive sheet of copper or galvanized steel, have the plates bonded multiple times to ground electrodes, in addition to all the above integrated techniques. They are nucking futs IMHO
You got my PM, give me a call if you wish
