Whether you work in a utility, a solar firm or you are a resident who lost power, you probably heard someone mentioned the word “fault” or “short circuit” before; from the utility perspective, we design the system to withstand a certain fault current level; from a solar perspective, the discussion whether solar contributes to the fault or not is common and from a customer perspective, they probably lost power before due to a fault on the line (Mother nature to blame).
What is a fault? Fault is simply an “unwanted” flow of large amount of current (thousands of amperes, where, ampere is the unit of measuring electric current) from various sources to the fault location (i.e. the location where a tree branch fell on the distribution lines or the location when a construction worker dug thru utility cables). Voltage is the potential difference; at the fault location, the voltage is around zero, thus all nearby generators, transformers, etc. sees the zero electric potential and send “contribute” large amount of current to the fault location.
In summary, think of a fault location as a football player in the final game (Super Bowl) running as fast as he can toward the touchdown, with only few seconds left in the game; that player represent the zero electric potential; all the players in the other team will do their best to stop that player, thus sprinting to the tackle, all the players are directed to one specific location with one goal to reach that player as fast as possible and to produce damage (stop him from scoring a touchdown).
