If you have ever worked with pole mount transformers, you have most likely run into both CSP and conventional types. Have you wondered what each name means and how the two types differ from each other? CSP, or Completely Self Protected transformers contain several safeguards to avoid issues that would cause overloading or damage to the transformer. Conventional transformers do not have any of these features which usually means they will need to be attached to a cut out switch.
The most recognizable component of a CSP transformer is the lightning arrestor. The arrestor protects against power surges caused by switching, lightning, or other high voltage sources. The lightning arrestor provides a path to ground to divert the high voltage surge rather than it passing through the transformer internals.
Another component CSP transformers are fitted with is the current sensing weak link on the high voltage side. If any part of the power distribution system fails, and too much current is being drawn, this weak link will open. It provides an internal fusing as a last result to limit the transformer windings from being damaged from overdrawn currents.
The last protective device on a standard CSP transformer is the low voltage breaker. This device typically has several different functions. A handle is attached to allow the breaker to be manually placed in an open or closed position. The breaker will also have a float which prevents operation under low oil conditions. To protect against overheating, a magnetic latch is placed within the breaker which is released when the temperature has reached the Curie point and the magnet losses its magnetic properties. Occasionally a low voltage breaker will have an emergency overload pathway to allow a percentage of power through the breaker to restore service when it is tripped open.
If you are needing protection of any kind on your pole mount transformer, make sure to look for a CSP transformer. If you do not need any protection other than a cutout, a conventional transformer will be perfect for your application.
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