We all remember the catastrophic power outages over the last two years. Increased demand for better and more reliable power supply systems could be heard on every street corner. Not only here in the U.S., but also in Europe and other parts of the globe, engineering and utilities are searching for a more advanced and reliable supply.
The main reasons for these failures were miscalculation in the power grid, aging power lines, and more. However, these are not the only causes for power grid failures. Non-linear loads such as computers, motor controls for fans, pumps, etc, variations in the load demand all have significant influence on power quality and on our daily routine.
The estimated cost for the power failure in the U.S. and Canada on August 14, 2003 was several billion U.S. dollars. The losses in July 2003 were $130 billion U.S. Denmark and the UK experienced similar failures.
The chart below shows the effect of the recent power failures in the U.S. and Europe.
Worldwide Power Failure- Italy -- June 26, 2003 -- Multiple Cities
- USA/Canada -- August 14, 2003 -- 50-60 Million Residents
- Great Britain -- August 28, 2003 -- 410,000 Residents in London
- Denmark/Sweden -- September 23, 2003 -- 4 Million Residents
- Italy -- September 28, 2003 -- Over 50 Million Residents
Source: Association of German Utilities, 10/10/03
The problem is more severe and costly than one may think. Even during power outages of short durations, the cost of lost production, damaged goods, machine failures, and repairs is reaching millions of dollars.
Estimated Cost in U.S. Dollars of Power Losses
Industry Segment / Typical Cost per Outage in U.S. Dollars- Semiconductor -- $ 4.9 Million
- Financial Industry -- $ 7.8 Million/per hour
- Data Processing -- $ 975,000
- Telecommunications -- $ 390,000/per minute
- Steel Manufacturing -- $ 455,000
- Glass Manufacturing -- $ 325,000
Source: The Cost of Poor Power Quality, Copper Development Association 2003
What Are Harmonics and What Creates Them?
Harmonics are deviations from the sinusoidal fundamental ac line voltage and current. Most electrical power in North America operates at a frequency of 60 hz. A harmonic frequency is an integer multiple of this fundamental frequency. In a 60 hz system, the second harmonic would be 120 hz, the third would be 180 hertz, and so on. The addition of any harmonic to the sinusoidal fundamental current or voltage will create distortion. The greater the amplitudes the harmonics present, the greater the distortion in the electrical waveform.
This phenomenon is affecting not only controllers in various industrial applications but has been increasingly evident in residential applications. Examples include clocks showing the wrong time, computers having unexplainable failures, and dimmer switches failing.
The ideal waveform of the voltage and current is a sinusoidal as shown in Fig #1, above.
In such a case, there will be no harmonics. With the ever-increasing use of faster electronic components and systems, higher frequencies allowed the designer to complete control tasks at a much faster rate. The problem is that when we switch power we can create harmonics. Such fast switching can be found in industrial control systems, factory automation, HVAC, pumping stations, fans, production and assembly lines, and steel mills. Our residences develop power problems with TVs, computers, appliances, washing machines, and the list goes on. For the term "fast-switching" devices, we are referring to electronic power supplies, UPSs, variable frequency drives, etc. These loads are also referred to as non-linear loads whereas the current waveform is not sinusoidal. See Fig #2, above.
A non-linear load can be described as a load which does not draw a sinusoidal current even though it has a sinusoidal voltage waveform.
Uncontrolled harmonics can cause system failure, limit the lifespan of machinery, create hazardous conditions, and reduce system efficiency, thereby wasting valuable energy.
What Solutions Are Available?
Let''s take a look at our power generation and distribution network. The power generated by the utilities is "clean", i.e., sinusoidal without any harmonic distortion. The power is distributed via the power grid through various transformer stations and finally to the industrial site and to our homes.
The harmonics are created by the end user and find their way back into the grid through the distribution network. Needless to say, these will affect other users connected to the grid who then experience system failure and other strange phenomena.
BLOCK has designed numerous Harmonics Filter Modules based on the LCR network. These filters are available in different power ranges which meet harmonic distortion limits as outlined in IEEE 519.
Harmonic Voltage Limits for Low-Voltage Systems
Application / Maximum THD (%)- Special Applications -- hospitals and airports : 3.0%
- General System: 5.0%
- Dedicated System -- exclusively converter load: 10.0%
Table 2 - From IEEE STD 519-1992, Table 10.2
The performance of the highly advanced harmonic filters were completed in the BLOCK Development and EMC Laboratory. Testing and approval of these new BLOCK HFM filters were performed under actual operating conditions. These filters are available for power ranges from 3 kW (4 hp) up to 630 kW (840 hp) to fulfill today''s industrial demands. With a power factor of 0.99, losses are kept to a minimum. These filters conform to the UL 508 and EN 61558 standards.