Consider the following statements summarized from a description of a “recent” blackout:
• Needles on meters in utility control centers were swinging wildly.
• There was a large power surge that suddenly reversed itself and headed north, cascading through grid, as hundreds of generators and transmission lines tripped offline, one by one.
• It happened too fast for the control room operators to coordinate the response over the phone
• The blackout, which affected six states and Ontario, occurred in late afternoon and lasted into the next day in many parts
• The Canadians fixed the blame to the south, and utilities in upstate New York insisted they were not at fault. Claims on the origin kept changing on the hour. Some feared sabotage.
• A federal commission was formed to find the cause and prevent it from happening again.
• Slowly, section by section of the distribution system was switched backed on, after the generators were brought back online, to prevent overloading them and shutting them down again.
These statements are summarized from a book produced by the staff of the New York Times, and they are referring to the “recent” blackout of the Northeast in 1965. The similarities to the blackout of August would lend credence to views of some who suggest that we have not learned our lesson after the multistate, cascading blackouts in the Northeast in 1965 and the West in 1996. There was even the suggestion that the United States has a “Third World grid.”
A few brief facts might put things in perspective before proceeding. During August’s blackout, over 60,000MW were lost. That is more than total yearly consumption of 168 of the 200-plus countries listed on the CIA 2002 World Factbook Web site’s energy consumption report. The United States’ consumption is over six times the consumption of all third-world countries combined, and it uses over 25 percent of the 14 TeraWattsHours consumed in the entire world. Hence the amount of generation, transmission and distribution of such of the electricity within the U.S. grid is unparalleled by any industrial or even developing country.
In the United States, there are more than 6,000 generators, about 500,000 miles of interconnected transmission lines (approximately the distance to the moon and back) and 50,000 distribution substations, each with feeders sending power out to consumers from each substation. All of this power is coordinated and precisely synchronized together so that clocks in Key Largo running off the 60Hz waveforms of the power system of North America keep the same exact time, day after day, as those in Green Bay. This is hardly a Third World system!
So what lessons can be learned from all of this? First, we’ll leave the “fixing of the grid” (whatever that entails) to those commissioned and employed to do such. Massive blackouts are very infrequent, yet there are disruptive events occurring every day that can wreak even more havoc on a facility’s system. They originate from lightning strikes, vehicle accidents, animals and equipment failure on the electric utility distribution system.
More frequently, however, they come from within the facility itself, such as large loads turning on simultaneously, improper wiring and grounding practices and “electronic” equipment that can be both a source and victim of power quality phenomena. These disturbances can interrupt production lines, cause damage to products and equipment, result in lost orders or transactions, corrupt data communication and storage and cause an overall decrease in productivity in today’s global economy. Estimates put power quality-related losses at $50 billion to $150 billion annual in the United States alone. Downtime in some facilities is measured in millions of dollars per second.
It doesn’t take something as large scale or long in duration as the blackout to affect the reliability of electrically supplied systems. A very short power quality disturbance, called a transient (also called impulses or glitches or spikes) can destroy a semiconductor wafer in a microsecond, or change a data bit on a memory device. A motor starting up on the factory floor can result in a sag or decrease in the voltage (See Figure 2 in sidebar) for just a few cycles (a cycle is 16.66 milliseconds long at 60Hz) that results in the plastic having to be scrapped out of the extrusion machine that shut down, or a weld to be sub-par on a car being built on the assembly line. High levels of distortion, from currents that have frequencies that are integer-multiplies of the 60 Hz fundamental frequency called harmonics, can overload the neutral conductors of wye circuits (which have no protective breakers), or cause false trips on some types of breakers.
The first step to improving a system’s reliability is often to conduct a power quality audit of the facility and monitor the incoming power at the service entrance, as well as at critical loads within the facility. Comparing the power quality information gathered over a week by a monitoring program with the susceptibility of the equipment within the facility provides you with a good starting point as to what to fix and where. It may turn out that the biggest problem can be fixed with a relatively small investment, such as when a relay coil is not able to maintain the contacts in the proper state, triggering incorrect information into the programmable logic controller that shuts down the system. Relocating equipment that draws large inrush currents on energization, such as motors, VFDs, copy machines or even laser printers, onto different circuits than the susceptible equipment may be a more cost-effective alternative than a UPS.
The next step is to see that the equipment and systems perform as expected. There are numerous examples of times when critical loads were not connected to the circuits fed by the back-up generators, and remained undiscovered until a situation like the August blackout. According to the Associated Press, Mike Brown, the new head of the Federal Emergency Management Agency, said he was “surprised to see some large-city water supplies taken down by the outage two weeks ago, and has ordered a nationwide review to identify similar infrastructure weaknesses around the country.” Test before, instead of scratching your head in the dark.
It is a pretty safe bet to say that blackouts will happen again. On one episode of the TV show “M*A*S*H,” a character said, “Rule 1—young men die in war. Rule 2—doctors can’t change Rule 1.” As long as the laws of physics still apply, there will be a series of events that will result in a blackout to some portion of the grid, as the system (as designed) protects itself from potential damage. Equipment and procedures will continue to evolve to reduce the probability of the occurrence, but there will still be situations that can be prevented from compromising the reliability of the system. The lesson (to be) learned is what should you be doing in your facility now to minimize the daily events that can disrupt your process, improve up time and productivity, and not spend your efforts worrying about the “hundred-year storm.” EC
BINGHAM, a contributing editor for power quality, can be reached at 732.287.3680.