Originally posted by Bill Addiss:I notice the requirement in the CEC is for 10 Ft ground rods. Is there also a requirement for a second rod if certain resistance measurements cannot be proven? (Down here (US) We are supposed to be at 25 ohms or less.)
The CEC deals with this problem by design rather than state a specific resistance. For low voltage ie. less than 750 volts, as per section 10-500 "the bonding and grounding conductors will, without becoming damaged, carry the fault current efficiently enough to allow the prompt functioning of overcurrent devices and the voltage rise due to the fault will be limited to a safe level"
In other words fault currents are predicted for worst case conditions and the bonding/grounding system designed to suit.
High voltage ie. over 750 volts has a section (36) dedicated specially to controlling or guarding against dangerous fault conditions to protect equipment and personelle.
Grounding and bonding is a particularly critical subject and is dealt with at an engineering level to attain the best possible safety conditions. Every situation is different and requires due consideration.