Application Guide
Three Phase Sectionalizer
2
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Sub ect: Load Break Switch in Sectionalizing Applications
ENTEC Product: Solid Dielectric Load reak Switch with Vacuum Interrupter (L S)
Sectionalizer Description Sectionalizers are used in tandem with upstream protective
devices such as reclosing breakers or reclosers to automatically isolate faulted sections of
distribution lines. The sectionalizer senses current above a pickup value and counts when the
upstream device de-energizes the circuit. After meeting a predetermined count, and while the
circuit is de-energized, the sectionalizer opens. This allows for a section to be isolated without
locking out the entire circuit by the upstream device. Sectionalizers do not interrupt fault
current, hence they are coordinated with an upstream recloser or breaker.
Three Phase Sectionalizer Advantages:
• A sectionalizer easily coordinates with any protective device; they do not require time-
current curves. This is an advantage in high fault zones or deeper within a feeder
behind multiple curves having tight coordination.
• Single phase damage is avoided with a three phase sectionalizer making it superior
versus fuses. When operated, all three phases simultaneously open.
• Without a time-current curve, sectionalizers placed between reclosers and fuses provide
additional points of separation for strategic isolation.
• Using state-of-the-art voltage restraint, the L S sectionalizer will function between
reclosers. Utilities can now protect PME’s without introducing another time-current curve
even with a recloser on the customer side.
• L S is equipped with a Schweitzer relay (SEL-751) and patent pending technology for
dependable, smart sectionalizing control. SEL-751 includes metering and superb
analysis tools familiar to SEL customers.
• Sectionalizers cost significantly less than reclosers.
• The L S can be switched manually or automatically and supports Scada.
Solution to Issue:
Reclosers cycle repeatedly for permanent faults eventually locking-out an entire distribution
system to isolate faults. These events often impact a significant number of customers and
result in extensive outages. Interruptions and downtime negatively impact reliability metrics
such as SAIFI, SAIDI, CAIFI and CAIDI.
