The sectionalizer is a self-contained, circuit-opening device used in conjunction with source-side protective devices, such as reclosers or circuit breakers, to automatically isolate faulted sections of electrical distribution systems. Power to operate the control circuitry and the mechanism is obtained from the line through the sensing-current transformers. No auxiliary power supply, external connections, or external equipment is required.
The sectionalizer senses current flow above a preset level, and when the source-side protective device opens to de-energize the circuit, the sectionalizer counts the overcurrent interruption. Sectionalizers are an economical method of further improving service on distribution lines equipped with reclosers or reclosing circuit breakers. They isolate permanent faults and confine outages to smaller sections of line.
Since the sectionalizer does not require a time-current base for its operation, it is easily coordinated with other protective devices on the system. It provides an additional step of protection without adding a coordinating step to the protective scheme. Sectionalizers can be used in place of fuses or between the reclosing device and a fuse without setting changes to other devices.
A sectionalizer has distinct application advantages:
- It can be applied between two protective devices having operating curves, which are close together. This is a vital feature in a location where an additional step in coordination is not practical or possible.
- It can be used on close-in taps where high available fault current prevents coordination with fuses.
- It has fault close and latch capability for any fault-closing operations.
Major classifying features of sectionalizers are as follows:
- Single-Phase Hydraulic
- Three-Phase Hydraulic
- Three-Phase Electronic