RECLOSER OF POWER SYSTEM CIRCUITS BASIC INFORMATION

What Are Reclosers? What Is Its Purpose and How Recloser Works?

The increasing electrical loads on distribution lines caused by increasing demand, particularly in the suburbs, have caused utilities to raise their operating voltages. Voltages are now being distributed at 13.8, 23, and 34.5 kV and higher .

This higher voltage has led to the formation of smaller service regions or more sectionalizing to\ minimize the impact of an electrical outage in parts of each region. Ironically, the probability of fault occurrence has increased as operating voltages have increased because of the combination of higher voltages and longer distribution lines.

These have made the lines more susceptible to outages on lower-voltage, shorter lines because of the higher probability of transformer bushing flashovers, falling tree limbs, lightning strikes, and other causes.

Early in the last century conventional disconnect switches met the requirements for sectionalizing, but this is no longer true. The switching capability of a disconnect, while marginal at 2.4 to 4.8 kV, is completely inadequate at 13.8 kV and higher.

To isolate a section of distribution line by opening a disconnect, the entire feeder must first be dropped, and this adds to the extent of the outage. Moreover, during emergency conditions the probability of the occurrence of a disconnect caused by operator error increases proportionally.

Many different kinds of switches are now available to meet a wide variety of applications economically. The single-pole switch and side-break switch are intended for pole-top installation on distribution feeders, while the vertical-break switch was designed for distribution substations or feeders.

These switches perform all of their switching duties without causing external arcing, and they also provide the reliable isolation of a visible air gap. A few examples of their versatility and use are the following.

# During emergency situations requiring fast response, a modern interrupter switch can drop the load without complicated circuit breaker and switch sequencing.

# There is no need to drop individual loads because the switch can drop the entire load.

# Lines can be extended and additional load accommodated (within the rating of the switch) without affecting switching ability.

# A loaded circuit can be dropped inadvertently (through an error or misunderstanding) with no hazard to the operator or to the system.

# Interlocking is not required between the primary switch and the secondary breaker in transformer operation.

Because of the no-external-arc feature of most modern interrupter switches, phase conductor spacing can be much less than that established for the older horn-gap switch. On the secondary side of the substation there are more feeders and more heavily loaded and longer transmission lines.