Static Transfer Switches

Static Transfer Switches:

^ü   The static transfer switch (STS) is an electrical device that allows instantaneous transfer of power source to the load. If one power source fails, the STS to backup power source.

^ü   A static transfer switch used to switch between a primary supply and a backup supply in the event of a disturbance. The controls would switch back to the primary supply after normal power is restored.

Classification of STS

^Ø   Low voltage STS (Vt Up to 600Vt, Ct rating from 200 amps to 4000 amps)

^Ø   Medium voltage STS (Vt from 4.61 KV to 34.5 KV)

^ü   Fast acting STS’s that can transfer between two power source in four to zero milliseconds are increasingly being applied to protect large loads and entire load facilities from short duration power disturbance.

^ü   These products use solid state power electronics or static switches as compared to electromechanical switches, which are slow for the application.

The basic STS unit consists of three major parts

^Ø   Control and Metering

^Ø   Silicon controlled rectifier

^Ø   Breakers/ Bus assembly