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A short circuit is an abnormal connection between two nodes of an electric circuit intended to be at different voltages. This results in an electric current limited only by the Thévenin equivalent resistance of the rest of the network which can cause circuit damage, overheating, fire or explosion.
The short circuit ratio (SCR) is an indicator of the strength of a network bus about the rated power of a device and is frequently used as a measure of system strength. A higher SCR value indicates a stronger system, meaning that the impact of disturbances on voltage and other variables will be minimized.
A different form of short-circuit testing is done to assess the mechanical strength of the transformer windings, and their ability to withstand the high forces produced if an energized transformer experiences a short-circuit fault. Currents during such events can be several times the normal rated current.
Current limiting is the practice of imposing a limit on the current that may be delivered to a load to protect the circuit generating or transmitting the current from harmful effects due to a short-circuit or overload. The term "current limiting" is also used to define a type of overcurrent protective device.
In a "ground fault" or "earth fault", current flows into the earth. The prospective short-circuit current of a predictable fault can be calculated for most situations. In power systems, protective devices can detect fault conditions and operate circuit breakers and other devices to limit the loss of service due to a failure.
It is also known as short-circuit test (because it is the mechanical analogy of a transformer short-circuit test), [1] locked rotor test or stalled torque test. [2] From this test, short-circuit current at normal voltage , power factor on short circuit, total leakage reactance , and starting torque of the motor can be found.
The effect of too high short-circuit current is discussed in the previous section. The short-circuit current should be around 20 times the rating of the circuit to ensure the branch circuit protection clears a fault quickly. Quick disconnecting is needed, because during a line-to-ground short circuit the grounding pin potential on the power ...
In a synchronous generator, [1] the short circuit ratio is the ratio of field current required to produce rated armature voltage at the open circuit to the field current required to produce the rated armature current at short circuit. [1] [2] This ratio can also be expressed as an inverse of the saturated [3] direct-axis synchronous reactance ...