It is misguided to assume that just because a UPS is running; it is fully operational, fit for purpose and legal. A voltage variation or harmonic pollution can all impact power quality and while a power failure may only be incurred for minutes, the recovery and repair process can take weeks, if not months (not to mention the expense). Testing a UPS system is riddled with complexities and a potentially dangerous situation, with a variety of knock-on effects which if not done correctly can jeopordise the whole operation. Breaking down the testing process into achievable and realistic chunks, centred on the standard factory acceptance testing reveals just some of the complexities involved:
- Preventative maintenance – a physical review of the equipment using thermal imaging will locate potential hot-spots, by revealing any poor power connections where higher temperatures are being generated. The logged data then enables actual results to be compared to design specifications with susceptible connections checked and tightened including the diodes, capacitors, inverter gates, drive boards and obviously review of the power supply. System familiarity also gives an opportunity to eye-ball the unit and gauge whether there are any unusual aspects, such as capacitor cans which might be leaking.
- Protection settings and calibration – it may sound obvious and simple, but the regular checking of protection settings and calibration of the UPS unit can eliminate a myriad of issues later. It avoids having to instantly react to a situation, as you can have more of a time luxury to proactively assess what is going on. The review of voltage in a test environment ensures measures can be put in place to eliminate battery discharges continuing too long, currents becoming too high and temperatures causing equipment destruction.
- Functional load testing – involving many aspects of testing and measurement to ensure optimum operational efficiency, including:
o Steady-state load test to check input and output conditions (of voltage, current and frequency) at agreed varying percentages of load, to ensure currents are matching across all elements of the module and equally sharing the load.
o Harmonics should also be analysed at the agreed load percentages (typically 0%, 50% and 100%) to ensure consistent distortion across phases and modules.
o Filter integrity using thermal scans can pick up potential failure areas in resistors, inductors and capacitors. However in large systems where there can be 100s of capacitors this is obviously more difficult but checking filter integrity can narrow down the area to explore.
o Transient response testing involving recording oscillography enables reactions to load swings to be compared with original specifications.
o Multi module systems testing verifies the operation will continue to maintain critical load in a failure situation, ideally without any significant deviation of voltage or frequency.
o Battery rundown is the final stage and should involve observation of temperature, voltage and current under load conditions. Any variations will typically indicate that the battery has degraded.
Using a company with significant experience in UPS maintenance and testing is paramount.
As Jason Koffler, Managing Director at Critical Power says, “Every aspect needs to be addressed to maximise power quality. From factory witness testing to ensure the configured UPS system performs to specification prior to delivery, to full on-site integrated operational testing, testing will deliver more benefits than hinder. Having the ability to claim for component failure under warranty or maintenance contracts means the manufacture faces the cost rather than the user. Granted the process of UPS testing is costly and time-consuming, but the costs associated with an unanticipated loss of business and production will, without doubt, outweigh those incurred from testing.”
Jason Koffler
Managing Director, Critical Power
DDI : 01844 340122
Email : jason.koffler@criticalpowersupplies.co.uk
