Automatic Transfer Switches: safe, reliable, robust solutions
23 February 2016
Wherever there is a backup or secondary power supply there must be a means of transferring from one source to the other. Automatic Transfer Switches (ATS) combine the mechanical changeover switching device and the control system, which will monitor both supplies and change the switch from one position to the other automatically.
The mains (or primary) supply is constantly monitored and should it fail or fall outside of preset values (i.e voltage too low/high) the ATS will send a signal to start the generator and then switch the load to the backup source when it is available. In highly critical environments the ATS will more likely be switching between two mains supplies which are supplied through a UPS (uninterruptable power supply).
Automatic Transfer Switches (ATS) are covered by IEC 60947-6-1 which states that the ATS must be a single complete manufactured product (as opposed to switching device and separate control circuit). Up until recent years it was common to use a means of switching (contactors, ACBs, MCCBs or changeover switch) with a separate control circuit which combined timers, phase failure relays and contactors.
The problem with this solution is that there is no standard way to assemble the control circuit, meaning that upon failure of the circuit (usually at the worst possible time when transfer to the backup supply is required) an engineer may have trouble fault-finding and fixing the problem. During this time there may be no possibility to change to the backup supply.
Socomec’s new ATyS range meet and exceed the IEC 60947-6-1 standard
Socomec’s new ATyS range meet and exceed the IEC 60947-6-1 standard. They combine a switch, motor and control module into one single off the shelf product, which is ready for installation into an enclosure or distribution board.
ATSs not only handle the switching of supplies in the event of failure, there are also other situations where the automatic transfer of supplies is necessary. In some cases the supplies may need to be periodically alternated (i.e sharing the load equally between two generators) or the use of the backup generator is incentivised (a utility company may offer an incentive to reduce their load at peak times). For this level of automation you will need an advanced ATS.
In a critical environment it is important to install the best possible ATS. Socomec’s ATyS P not only monitors the voltage and frequency of the supply but also the current and power (through external CTs). When fitted with an ethernet module you can access its on-board webserver to view power measurements, a history of time-stamped events, and also schedule or instantly command the switch to change position or perform an on-load or off-load test.
All of this information can also be sent to a Building Management System (BMS). There is also a load-shedding feature. This is used in situations where the backup supply does not have the capability to supply the entire load (usually an undersized generator). Before switching to the backup supply a signal is sent and the non-essential loads are isolated.
The ATyS P has a self-diagnosis feature, which will flag and communicate any component issues with its motor or control module. In the event of an issue, both the motor and electronic module can be replaced without the need to disconnect the supply, the ATyS can still be operated manually during this time. An ATyS is a fully interlocked isolation device. Both supplies can be isolated and the switch padlocked in the ‘Off’ position for building maintenance.
Single Phase and Three Phase versions are available from 40A to 6300A. Contact John Weldon in Garo Electric Ireland for more information or a demonstration.http://www.engineersjournal.ie/2016/02/23/automatic-transfer-switches-safe-reliable-robust-solutions/http://www.engineersjournal.ie/wp-content/uploads/2016/02/aaagaro1.jpghttp://www.engineersjournal.ie/wp-content/uploads/2016/02/aaagaro1.jpgSponsoredenergy