UPS Commissioning Testing
What is involved in UPS testing?
As part of the commissioning procedure for a UPS, several tests are carried out in order to determine the correct operation of the UPS under both steady state and transient operating conditions. A typical commissioning test would include the following: –
- Steady State Testing
- Harmonic Analysis
- Transient Response Testing (including)
- Shock Loading
- Mains Failure
- UPS Module Failure
- Static Transfer Switch (STS) testing
Steady State Testing
The input and output parameters such as voltage, current, power and frequency are tested at various power levels to ensure that they remain within specification throughout the test.
Where there are multiple UPS units operating in parallel onto a common busbar, it is essential that the load is shared equally between the modules. Monitoring this load sharing forms an essential part of the steady state testing.
Effectively part of the steady state testing, harmonic analysis will provide a detailed breakdown of the harmonic content of both voltage and current resulting from the operation of the UPS. It is important that the analysis is carried out at various levels of power as the highest harmonic production may not occur at full load.
The results of the harmonic analysis will be assessed against the specification of the UPS installation. This may be a bespoke set of harmonic limits or a recognised standard / engineering recommendation such as IEC 61000-3-4 or ENA EREC G5/5.
This test involves imposing step changes of load onto the UPS and monitoring the resultant minimum / maximum load voltages and recovery time to within 1% of the nominal voltage.
Figure 1 shows an example of a voltage recovery test carried out by PureSine during UPS Commissioning testing. During this test a shock load change of 0 to 100% of the UPS rating was applied to the UPS which resulted in a load voltage dip, the duration of which was limited by the ability of the UPS to dynamically adjust its output voltage. Generally, a test script will specify a time within which the UPS should recover to within 1% of the nominal voltage.
Figure 2 shows an example of a voltage recovery test carried out by PureSine during UPS Commissioning testing. During this test a shock load change of 25 to 0% of the UPS rating was applied to the UPS which resulted in a load voltage swell, the duration of which was limited by the ability of the UPS to dynamically adjust its output voltage. Again, the time that the UPS takes to regulate the voltage to within 1% of the nominal voltage is generally specified.
Figure 1 – Example of 0 to 100% loading shock loading under voltage recovery test
Figure 1 – Example of 25 to 0% loading shock loading under voltage recovery test
Static Transfer Switch Testing
In any resilient power system, there will be multiple sources of supply for a protected busbar. In order to ensure that the correct source is connected to the load, a static transfer switch will be used to transfer from a primary supply to a backup supply in the event that the primary supply fails.
Often the primary and secondary supplies are fed from UPS systems, each of which could be an N+1 system and each of which fed by both mains and generator supply, offering multiple layers of resilience.
Part of the UPS commissioning may include a static transfer switch test that involves deliberately failing the primary supply and monitoring the output of the STS to ensure that the transfer time from the primary supply to the secondary supply is within that specified.
Figure 3 shows a transient voltage capture during STS testing that captured the exact moment of supply transition in very high resolution, allowing the transfer time to be determined to an accuracy of 100ths of a millisecond.
Figure 3 – Example of STS transfer test waveform capture
How can we help?
PureSine, in conjunction with load bank suppliers, can carry out all of the above tests, offering a comprehensive service for all UPS testing requirements. In addition to this, PureSine can also offer mitigation solutions should the need for same be identified during testing, e.g. the provision of active harmonic filtration should the harmonic distortion measured prove problematically high.