What is a sectionalizer ? Where is it used ?

A sectionalizer is a current monitoring device which isolates faulty sections of electrical systems.  It is generally used alongside other protective devices such as breakers and reclosers.  The sectionalizer contains a current monitoring device which senses the current.  

The sectionalizer trips by both sensing the current and sensing the absence of voltage when the upstream breaker has tripped.  

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When the breaker closes and the supply resumes, the sectionalizer in the faulty line remains open.  The supply is thus resumed to the other healthy feeders.  

The sectionalizer is not a interrupting device. It cannot interupt a circuit.  It can only isolate a de-energised circuit.  Hence, it is is always used in conjunction with the immediate upstream breaker.  Sectionalizers are relatively inexpensive equipment used to isolate and localise a fault.  

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