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A resistor removed from a high voltage tube circuit shows damage from voltaic arcing on the resistive metal oxide layer. Resistors can fail open or short, alongside their value changing under environmental conditions and outside performance limits. Examples of resistor failures include: Manufacturing defects causing intermittent problems.
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.
Overhead power lines are easiest to diagnose since the problem is usually obvious, e.g., a tree has fallen across the line, or a utility pole is broken and the conductors are lying on the ground. Locating faults in a cable system can be done either with the circuit de-energized, or in some cases, with the circuit under power.
In an electrical grid, the short circuit ratio (or SCR) is the ratio of: the short circuit apparent power (SCMVA) in the case of a line-line-line-ground (3LG) fault at the location in the grid where some generator is connected, to: the power rating of the generator itself (GMW).
A transient fault is a loss of power typically caused by a fault on a power line, e.g. a short circuit or flashover. Power is automatically restored once the fault is cleared. A brownout is a drop in voltage in an electrical power supply. The term brownout comes from the dimming experienced by incandescent lighting when the voltage sags.
Lack of overcurrent capability (low short circuit ratio) of a weak grid creates a multitude of problems, including: [2] transients during the large load changes will cause large variations of the grid voltage, causing problems with the loads (e.g., some motors might not be able to start in the undervoltage condition);
Electromigration can also cause the atoms of a conductor to pile up and drift toward other nearby conductors, creating an unintended electrical connection known as a hillock failure or whisker failure (short circuit). Both of these situations can lead to a malfunction of the circuit.
The special cases of open circuit and short circuit lines are of particular relevance to stubs. Reflections cause standing waves to be set up on the line. Conversely, standing waves are an indication that reflections are present. There is a relationship between the measures of reflection coefficient and standing wave ratio.