Hi John:
> In the CB Scheme "National Differences" document, Danish and Norwegian > requirements (in 6.3.3.1 and 6.2.1.2, respectively) make reference to > "equipotential bonding". Can anyone tell me exactly what equipotential bonding > is? I assume that it is some form of grounding...would having a permanent > connection to protective earth satisfy this requirement? "Equipotential bonding" is the name given to the general case, while "grounding" or "earthing" are the names given to a specific case of equipotential bonding. Equipotential bonding is a scheme of protection against electric shock. All conductive parts in the local environment, e.g., a room, are bonded together to create an equipotential environment. If there is no potential difference in the environment, then there is no possibility of electric shock. (This is the principle behind bonding all conductive parts within electrical equipment together.) In practice, all conductive parts in the environment cannot be bonded together. Instead, all conductive parts of electrical equipment are connected to ground via the protective conductor in the power cord. Likewise, all other conductive parts in the room, e.g., plumbing, heating ducts, etc., are connected to ground via some other means. This is not a perfect equipotential environment, but it is functional and practical. The flaw is that during a fault to the equipment metal, there is a voltage drop across the resistance of the protective conductor that can allow the voltage on the equipment metal to be as high as 1/2 the mains voltage (with respect to other grounded parts) until the overcurrent device operates -- which can be as long as 2 minutes. So, an electric shock condition could exist for those 2 minutes. If a true equipotential environment was established with local (i.e., in the same room) bonding, then the voltage drop across the protective conductor would not create a potential difference between the equipment and the remainder of the environment (because they are all bonded together within the room). So, no electric shock condition would exist. Best regards, Rich ------------------------------------------------------------- Richard Nute Product Safety Engineer Hewlett-Packard Company Product Regulations Group AiO Division Tel : +1 619 655 3329 Effective 6/12/99: +1 858 655 3329 16399 West Bernardo Drive FAX : +1 619 655 4979 Effective 6/12/99: +1 858 655 4979 San Diego, California 92127 e-mail: ri...@sdd.hp.com ------------------------------------------------------------- --------- This message is coming from the emc-pstc discussion list. To cancel your subscription, send mail to majord...@ieee.org with the single line: "unsubscribe emc-pstc" (without the quotes). For help, send mail to ed.pr...@cubic.com, j...@gwmail.monarch.com, ri...@sdd.hp.com, or roger.volgst...@compaq.com (the list administrators).