In the event of a bolted fault, a large amount of thermal energy and magnetic force can be produced. In accordance with various standards, protective devices and current-carrying components are to be properly rated to withstand and interrupt the fault.
As seen in Figure 8.1, fault current can “flow” down or up a circuit when a short is created. The current flowing from the utility (the larger amount) is represented by the arrows pointing in the direction of the motor, and the contribution returning from the motor (the smaller amount) can be seen in the arrows pointing back toward the utility. The reason for this back contribution is that the spinning rotor of the motor will not instantaneously stop, and the magnetic field will remain for a short number of cycles. This occurs even though the voltage in the event of a bolted fault would theoretically equal zero (0).
The danger is that if equipment is not properly rated for the available fault current, catastrophic failure can occur. Through the use of specialized software and the associated equipment libraries, Electrical Power and Safety Company can help advise if your existing electrical infrastructure is rated to handle a worst-case scenario bolt fault. Please keep in mind that with an ever-changing electrical grid and utility power supply, the worst-case bolted fault can vary over time.
