requirements of the electricity standards the customer earth resistance should be less than 70 ohms and the neutral resistance should be less than 1 ohm based on soil conditions it is hypothesised that the customer 39 s earth resistance is always greater than 5 ohms in order to solve this problem mathematically carson 39 s equations must be used carson 39 s equations model the behaviour of long parallel overhead conductors with a return path through ground due to the high reactance of the current travelling through the ground the majority of the current is forced to return through the neutral line using fig7 carson 39 s equations can be used to solve the above parallel lines assuming conductor q is a ground wire let conductor q be a ground wire in which case v q 0 since both ends of this conductor are connected to ground equation 8 cannot be used as it does not take into account the grounding resistance that exists within the system the above example is for a purely theoretical situation the customer 39 s earth probe has a finite surface area in contact with the ground therefore creating a finite resistance in order to simulate our system a ground resistance must be introduced into the system in order to simplify the equation the earth resistance at the source has been ignored as it is insignificant in comparison to the customer resistance this is based on the source earth resistance being cmen with multiple earths v a i a z a i n z an i a r l i e r e 9 v n i a z an i n z n i e r e 10 in the circuit diagram of fig6 i n is defined as flowing in.