By Michael Maiello
Today’s technologically pervasive world demands power that is free from disturbance. Yet, despite the growth of smart grids and more sophisticated technology, power problems can still plague businesses. Just consider what an outage of a day or two would cost your customers; even an hour can take a significant toll for some businesses.
Still, many service providers don’t completely understand all the various types of power disturbances that can threaten customers’ server rooms. While protecting against major events like hurricanes and floods is certainly important, there are many other, far more subtle ways in which power disturbances can wreak havoc on a business. Here are six of them:
Potentially the most damaging of all disturbances, transients fall into two subcategories: impulsive and oscillatory. Impulsive transients are the most common type of power surge or spike. These types of events can be categorized further by the speed at which they occur (fast, medium, and slow), ranging from very fast events measuring 5 nanoseconds (ns) rise time from steady state to peak, or short-term measuring less than 50 ns. Impulsive transients are caused by events like lightning, switching of inductive loads, utility fault clearing, and like issues – and often result in corrupt data and damaged equipment.
Oscillatory transients is a sudden change in the steady-state of a signal’s voltage or current (or both) at both the positive and negative signal limits – in other words, the power signal swells and shrinks rapidly. These transients often happen when a load, such as a motor or capacitor, is suddenly turned off. When oscillatory transients appear, they can be quite disruptive to electronic equipment.
An interruption is the complete loss of supply voltage or load current, with the following duration ranges:
- Instantaneous: .5 to 30 cycles
- Momentary: 30 cycles to 2 seconds
- Temporary: 2 seconds to 2 minutes
- Sustained: more than 2 minutes (sustained).
The causes of interruptions can vary, but are usually the result of some type of electrical supply grid damage, such as lightning strikes, animals, trees, vehicle accidents, destructive weather, equipment failure, or a basic circuit breaker tripping. While the utility infrastructure is designed to automatically compensate for many of these problems, it is not infallible. One common example of an interruption is when all electronic devices and lights go out in a house for a short period of time and then comes back in a few minutes. While this interruption is inconvenient in a home, a similar power loss in a business setting can be costly, as data can become corrupt or be lost entirely during the interruption.
3. Sag or Undervoltage
Usually caused by system faults or the switching on of loads with heavy startup currents, a sag is a reduction of AC voltage at a given frequency lasting for .5 cycles to a minute. This is akin to the drop in water pressure when multiple faucets in a single home are turned on. Sags can cause significant equipment damage over time.
Often referred to as a “brownout” (albeit incorrectly so), undervoltages are the results of long-term power consistency problems that create sags in the short term. Undervoltages can lead to the failure of non-linear loads such as computer power supplies.
4. Swell or Overvoltage
The opposite of a sag is a swell, caused by an increase in AC voltage lasting .5 cycles to one minute. Like sags, the damaging effects of swells – which include degradation of electrical contacts and semiconductor damage – usually go unnoticed for extended periods of time. However, immediate, more noticeable results are the flickering of lights and data errors.
Similar to undervoltages, overvoltages are the result of long term problems that create temporary power swells. Overvoltage conditions can create high current draw and cause equipment to overheat and become stressed.
5. Waveform distortion
A waveform distortion is any power quality variation affecting the wave shape of the voltage or current. There are five primary types of waveform distortion: direct current offset, harmonic distortion, interharmonics, notching and noise. To varying degrees, they can all cause damage or disruption to IT equipment.
6. Voltage fluctuations
A voltage fluctuation is a series of small, random changes in voltage caused by any load exhibiting significant current variations. A common symptom is the flickering of incandescent lamps.
Of course there are ways to protect against each of these types of power disturbances, often by using UPS systems, backup generators, surge protectors, power line conditioners conditioning, proper grounding and more. In my next blog post, I’ll explore some ways you can help customers protect against these common power disturbances.
Michael Maiello is Senior Vice President, Home and Business Networks for Schneider Electric and has served in this role since 2012.
Michael has been with APC and Schneider Electric for over 20 years. In that time he has held various positions in engineering, engineering management and general management. Prior to being named Senior Vice President of Home and Business Networks, Michael served as Vice President for the Business Power Solutions group and Director of OEM and Special Products. Over the last five years, Michael has lead the Business Power Solutions team, which focuses on single phase power products for the availability of business applications and includes world known brands, such as Smart-UPS® and Symmetra®.
Michael holds both Masters and Bachelor Degrees in Electrical Engineering from Brown University.