Arc Phenomenon is the term given to the unexpected voltage spikes produced by two or more conducting materials connected in a circuit. When a voltage spikes the material being connected distributes the charge energy over its surface resulting in a brief interruption of the current flow. Short circuits are formed when the short circuiting device, usually an isolation bridge, connects the two sources and these are called short-circuits.
Short-circuits occur at random and sometimes the distribution of charge energy is random, but often it occurs within a well-defined range of ranges which can be described as safety parameter. The probability of such occurrences is related to the design of the circuit breaker. The safety parameters are set so that the chances of short-circuit are very less and the control of the risk is more effective. There are some factors which can increase the risk of short-circuit like; poor insulation, poor coupling, proximity of contacts to each other and the interconnection of dissimilar metals, which leads to electrostatic attraction and can result in short-circuit. Hence, when you install circuit breakers in your home, make sure that they are placed in an area, which is away from all metallic objects.
A circuit breaker can be manual or automated. It depends upon the working mechanism of the breaker. Manual circuit breaker has inputs attached to terminals and contacts and these contacts are selected based on their present position and the voltage drop across them, while an automated circuit breaker has input terminals and various sensors for measuring the changes in the voltage across them and an output indication device for controlling the circuit either manually or automatically.
When arc Phenomenon happens, the voltage that appears across the contacts of the circuit breaker increases suddenly and abruptly. This sudden change in the input voltage may be caused by an overload, by short-circuiting or even by chemical reaction. What generally happens in such cases is that the circuit is cut-off and there is a drop in the input voltage. The reason why voltage that appears across the contacts of the breaker increases suddenly is that when the circuit breaker is closed, the circuit gives very high resistance.
Once the circuit breaker is open, the variation in the input voltage across the contacts of the circuit breaker creates a small current that remains in the circuit. This current is known as induced arcing. Due to the arcing, the current stays in the circuit for a longer duration and this results in a rise in the measured arc voltage. The difference in the measured arc voltage along with the induced arcing becomes a function of the contact resistance. If there is a greater resistance, it implies that more arc voltage is produced.
If the arcing occurs at the contacts, the resistivity at the center of the circle determined by the current will be low and will not allow any rise in the voltage. However, the resistivity will be high on the outer sides of the arc. It means that the current will create a slight voltage across the contacts when the circuit is closed. As the circuit opens, the current will create a sudden surge and the induced voltage will be high. If the circuit is closed, the current will again create a sudden surge and the arc voltage will reduce.
It has been found that the most common cause of this phenomenon is the presence of p.d. ions on the contacts of the circuit breaker. These ions are produced due to the deposition of mercury across the contacts. The presence of p.d. ions will result in a rise in the resistance value of the circuit and will reduce the arc voltage.
To fix this problem, it is important to remove the mercury from the contacts and place them in a non-insulated box. Then connect the ends of the wires to the contacts and then make an indentation at the top of the box. Place the box over the contacts and then fill in the indentations with some silicone glue. This should fix the problem.