External transients are considered "impulse" type surges and are severe and instantaneously damaging. These surges originate outside a given facility or home. These surges account for about 20% of transient related electrical damages.
These transients come in on unprotected power, data or telephone lines of your business or home. They can range from several thousand to tens of thousands of volts and amperes (grid switches, system faults) up to hundreds of thousands of volts and amperes (lightning).
2) Utility Grid Switching
Utility grid switching is a major power quality issue that can cause powerful external transients.
Power generating utilities break the distribution of power into grids.
The electric companies distribute power to each grid in a steady stream at all possible times, regardless of fluctuations in demand.
Unfortunately, this can cause problems for customers.
Each customer's power needs are constantly changing, thus constantly changing the overall grid needs.
Instead of adjusting the power generating equipment output for each changing power demand situation, the electric companies adjust by switching the supply of power from one grid to another grid.
When the grid supply is switched, very large surges are created. These transients can reach as high as 25,000 Volts.
3) Power System Faults
Power System Faults are essentially a sudden disruption in a normal electrical system or grid caused by a short or open circuit.
Shorts or open circuits can occur in power distribution equipment like transformers, transmission lines and generators. These faults can be very destructive.
Typical causes of power system faults:
The resulting voltage surges from system faults can be in the tens of thousands of volts and amperes.
If your business or home is on the receiving end of one of these external surge events - it's going to be a very long and expensive day especially when the damage could have been prevented or at the very least mitigated.
Don't take chances with external transients. Take preventative measures.
Remember - It only takes one hit.
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