Here’s a neat article written by our friends at APC: Powercuts during summer months may damage data, albeit a confusing title for what the article is about.
They bring up a valid point about overvoltage leading to damage of equipment. Your normal mains supply is designed to operate at 230V±10%, which means a maximum voltage entering your building of 253V. However, the substation providing this voltage has to be able to do so during full power loading. Let’s say you’re on an industrial park and the substation is providing power to all the buildings – the IT infrastructure, the telecom systems, the lighting, the air conditioning, elevators, escalators etc. The load can be quite substantial, but let us take a figure of say, 1000Amps (equivalent to 10 houses). If the impedance on that line was half of one tenth of an Ohm – 0.05Ω the voltage drop across the cable using good old Ohm’s law would be 50V. This means that the substation needs to set its output voltage to around 280V so that when the power reaches your building it is 230V and within limits. However, if the load is suddenly removed – all the air conditioners are switched off, the buildings are empty and nobody is at home, all of a sudden you are hit with 280V, as the lower current causes less voltage to be dropped across the supply cables.
Some people call this a surge and think that surge suppression devices will protect them against it. In fact, this is not a surge but rather a voltage swell or overvoltage condition. (A surge is an overvoltage condition too, but of short duration -usually µseconds), and in order to safeguard your equipment you need to have some form of overvoltage protection. The only way to achieve this is by the use of either voltage regulators or by the Uninterruptible Power Supply (UPS).
A voltage regulator is a (usually mechanical) device that incorporates a tap changing, or continually variable transformer to keep the output voltage to a tight tolerance.
The Uninterruptible Power Supply, however will also provide overvoltage protection by keeping the voltage within limits. How well it does this depends upon the type of technology used:
- The Offline Uninterruptible Power Supply will provide overvoltage protection by dropping to battery as soon as the mains voltage is out of limits. This will protect your equipment but if this happens regularly or for prolonged periods, the UPS battery will drain and you will lose power.
- The Line Interactive Uninterruptible Power Supply will provide overvoltage protection by incorporating some voltage regulation. When the mains goes to high, the UPS System will “buck” the voltage downward by changing taps on a transformer. This has the benefit over the Offline UPS System in that there is no dropping to battery for marginal overvoltage conditions.
- The Online Uninterruptible Power Supply, (aka Online Double Conversion Uninterruptible Power Supply) provides the best possible overvoltage protection. It has a very wide input voltage window, which means it can take very high voltages (as well as very low voltages) without reverting to battery. What’s more the voltage supplied to your system is constant and unchanging regardless of what is happening to the input voltage.
It’s another string to the Uninterruptible Power Supply bow, as not all power problems are as obvious as the power cut. Give your equipment overvoltage protection with a Uninterruptible Power Supply from UPSMart.
