Automatic Transfer Switch (ATS) Electrical Testing

An Automatic Transfer Switch (ATS) is a device that automatically transfers power supply from one source to another in the event of a power outage or failure. It is commonly used in standby power systems to ensure continuous power supply to critical loads, such as hospitals, data centers, telecommunications facilities, and emergency services.

Testing an Automatic Transfer Switch (ATS) is important to ensure its reliability and proper operation during power outages or switching power from one line to other.

Automatic Transfer Switch (ATS) Mechanical Inspection

Mechanical inspection of an Automatic Transfer Switch (ATS) is essential to ensure its structural integrity, proper functioning, and reliability during power transfer operations.

1. Inspect for physical damage.
2. Compare equipment nameplate information and connections with single line diagram and report any discrepancies.
3. Check switch to insure positive interlock between normal and alternate sources.
4. Check tightness of all cable connections and bus joints.
5. Perform manual transfer operation.
6. Transfer switch and compartment are clean and dust free.
7. Verify all vendor control cable wiring.
8. Check terminations and tagging.

Automatic Transfer Switch (ATS) Electrical Testing.

Electrical testing of an Automatic Transfer Switch (ATS) is very important to ensure its proper functioning, reliability, and compliance with safety standards.

1. Perform insulation resistance tests phase to phase and phase to ground with switch in both alternate and source positions.
2. Perform electrical insulation and contact resistance tests as referenced.
3. Set and calibrate the Voltage Sensing relays.  Contact PDD for settings.
4. Set and calibrate the Transfer Time delay relay.  Contact PDD for settings.
5. Perform automatic transfer by simulating loss of normal power.
6. Perform automatic transfer by return to normal power.
7. Monitor and verify correct operation and timing of Normal Voltage sensing relays.
8. Monitor and verify correct operation and time delay upon transfer.
9. Monitor and verify correct operation and timing of Alternate voltage sensing relays.
10. Monitor and verify correct operation and timing of Automatic transfer operation.
11. Monitor and verify correct operation and timing of mechanical and electrical interlocks and limit switches.
12. Monitor and verify correct operation and timing, of time-delay and retransfer upon normal power restoration.

Electrical Field Testing.

1. Insulation Resistance Test: Measure the insulation resistance between conductive parts and ground with the ATS in both normal and alternate power positions. Verify that insulation resistance values meet specified standards.
2. Contact Resistance Test: Measure the contact resistance of the ATS contacts to ensure proper electrical conductivity and minimal voltage drop across the contacts.
3. Voltage Sensing Relay Calibration: Set and calibrate the voltage sensing relays to detect voltage levels accurately and initiate transfer operations when necessary.
4. Transfer Time Delay Relay Calibration: Set and calibrate the transfer time delay relay to ensure the appropriate delay between detecting a power outage and initiating the transfer of power sources.
5. Automatic Transfer Testing: Simulate a power outage by disconnecting the normal power source or simulating a fault condition. Monitor and verify that the ATS automatically transfers power to the alternate source within the specified time frame.
6. Return-to-Normal Testing: Restore power to the normal source and monitor the ATS to ensure it returns the load to the normal source smoothly and without interruption.
7. Verification of Voltage Sensing Relays: Monitor and verify the correct operation and timing of the voltage sensing relays during automatic transfer and return-to-normal operations.
8. Verification of Mechanical and Electrical Interlocks: Monitor and verify the correct operation and timing of mechanical and electrical interlocks, limit switches, and safety features during transfer operations.
9. Retransfer Testing: Monitor and verify the correct operation and timing of time-delay relays and retransfer mechanisms upon restoration of normal power.

By conducting thorough mechanical and electrical testing of the ATS, you can ensure its reliable operation and compliance with safety standards and regulatory requirements. Regular testing and maintenance are essential to prevent unexpected failures and ensure uninterrupted power supply during critical situations.