ATS Systems

Imagine a facility relying on two separate power sources, the grid and a backup generator, needing something that can instantly and automatically detect the moment the grid fails, disconnect from it, and connect instead to the generator, all within seconds, without anyone physically flipping a switch, and then reverse the entire process automatically once grid power returns and stabilises. An automatic transfer switch, ATS, is that device.

An ATS sits between the utility feed and a facility's backup power sources, gensets and UPS systems, both covered elsewhere on this site, continuously monitoring incoming power quality and transferring load to backup power the instant an outage is detected, a function so fundamental to redundant power design that essentially every data centre power architecture diagram includes one.

As backup power sources diversify beyond diesel gensets alone, into gas gensets, fuel cells and on-site turbines, all covered elsewhere on this site, the ATS's job of correctly detecting a failure and switching cleanly between an increasingly varied mix of primary and secondary sources becomes correspondingly more sophisticated, and a mis-specified or slow-switching ATS is a commonly cited reason an otherwise well-engineered backup power system still fails to prevent an outage in practice.

This is a term a reader is likely to encounter buried inside a data centre's technical reliability documentation or an incident post-mortem, where the actual point of failure during an outage often turns out not to be a lack of backup power at all, but a transfer switch that did not perform its automatic handover correctly.