Each year as the Super Bowl approaches, the conversations around power quality begin to peak. Well, maybe not every watercooler conversation goes along the line of power quality, but if you watched Super Bowl XLVII in February 2013, when the Baltimore Ravens and San Francisco 49ers faced off, you know that in the third quarter half of the lights in the New Orleans Mercedes-Benz Stadium went dark for 34 minutes, and you might wonder if that could happen again.
During the “Blackout Bowl,” services other than lights were impacted too. Elevators filled with fans eagerly returning from half-time stopped, the point-of-sale registers were down, and vendors could not sell their goods or refreshments. Television viewers were left with confusion and more commercials – some of which took advantage of the unexpected situation. (Remember Oreo’s Power Out? No problem. You can still dunk in the dark. social media spots?)
Officials blamed the outage on an “abnormality” in the power system that triggered an automatic shutdown. And while most utilities are not faced with a power quality event matching the exposure of the one that occurred during the Blackout Bowl, every utility is faced with power quality events with similar impacts and outcomes.
The financial impact on the consumer comes in the form of losses, damage, and downtime, whether the consumer is industrial, commercial or residential. The utility feels the impact in the customer relationship, lost revenue opportunities, and community or media backlash.
It’s safe to say power quality is an everyday concern to utilities and their customers, so let’s learn a little more about how to avoid the impacts of power quality events – before they occur.
Defining Power Quality
Blackout. Blink. Brownout. Bump. Clean ground. Clean power. Dirty ground. Dirty power. Surge. Wink. Glitch. Outage. Interruption. Power surge. Raw power. Spike. Have you used any of these terms to describe anomalies in the power system?
All these events are caused by a reduction in power quality. But how is power quality defined?
IEEE 100: Authoritative Dictionary of IEEE Standard Terms defines Power Quality as, “the concept of powering and grounding sensitive equipment in a manner that is suitable for the operation of that equipment and compatible with the premise wiring system and other connected equipment.”
So, as a general concept, power quality is a measure of the successful operation of electrical equipment by an electrical supply system. Some may consider this definition equivalent to reliability, but power quality can be much more than just the classical measure of outages and momentary interruptions that a utility is accustomed.
Power quality is a relationship
Inherent in the definition of power quality is the relationship of the end use equipment (consumer) and the supply system (utility). In physics, this relationship is represented by a simple mathematical equation named after German physicist Georg Ohm, who described it in 1827.
Ohm’s law: I=V/R.
Where current (I) through a conductor between two points is directly proportional to voltage (V) over resistance (R), where R is a proportional value independent of current.
Looking at the relationship between voltage (V) and current (I) in Ohm’s law, we find that the electricity consumer is primarily responsible for current. No lamp – no current; no motor – no current.
Voltage (V), on the other hand, is fundamentally the utility’s realm. No generation – no voltage; no delivery system – no voltage.
The proportional value in Ohms Law, resistance (R) or impedance, is a combination of the resistance on the wires, the transformers, the cables and all the connections that provide the unique path of the supply from the generation terminal down to the socket or terminals of the end load, as well as the electrical characteristics of the load.
The relationship between current, voltage and resistance described by Ohm’s law defines the magnificent network of real-time supply. Load drops – generation lowers instantly. Load increases – generation rises instantly.
Which value is at fault?
This simple relationship that bonds the utility and consumer is at the core of any power quality event or issue. As an example, when there is a blink, or momentary interruption, in power supply, a manufacturers process line may stop unexpectedly.
But is the utility voltage at fault or is the sensitivity of the adjustable speed drive (ASD) in the manufacturing process at fault? Before the manufacturer went to ASDs, its process likely used large motors with spinning mass that would simply “ride through” the same utility blink in days of the past. On the other hand, the manufacturer may perceive the utility may have changed the frequency of “blinks” over time.
Consider also, why is manufacturing stopped, but the offices didn’t notice anything? Or why is one manufacturer affected and not the neighboring facility? The neighbor experienced basically the same blink because it shares the same distribution network.
The answer is that various end devices experience the momentary interruption differently. Individual pieces of equipment react based upon the electrical and electronic design of the device.
Consumer and utility-side fixes
Equipment manufacturers recognize the imperfections of the power supply. For example, the classic harbinger of an outage, the digital clock, was adapted by adding a 9-volt battery or small capacitor to ride-through that middle of the night storm and every other momentary that occurred during storms or under blue-skies.
Suppliers of ASDs, commonly found in industrial processes and commercial/institutional ventilation systems, provide options to desensitize the undervoltage protection of the equipment. In another example, Coca-Cola Co. recently filed a US Patent for an intermittent power-grid-ready display cooler that uses a material that freezes while powered and maintains the chilled conditions when power is lost. Each of these cases represents an adaptation of a device sensitive to the supply system to a device that compensates for the supply system’s dynamics – or hardened.
Sometimes the utility must take the lead in fixing problems. For example, if hundreds of homes experience a recurring bright and dim cycle of their home lighting, the utility might find the root cause is voltage fluctuations on the distribution network caused by a manufacturer installing a new piece of equipment or a set of utility line capacitors which are misoperating In both these cases, the solution lies with the utility to negotiate terms with the manufacturer or fix the line equipment.
Answers are in the data
If confronted with a power quality issue, detailed data is crucially important to get past the early emotional reaction and search for who’s at fault and who’s fixing the problem. The tools are available to find the answers and solutions.
For example, AMI meters with voltage recording and sag/swell event capture will provide the information needed to detect issues like low voltage or correlate issues like voltage sags that correspond to a customer process alarm. Also, grid monitoring devices such as smart grid line sensors will monitor the dynamics of the voltage and current on the distribution network, and identify potential issues like intermittent line faults, or tracking down active issues such as tracking down the location of the offending welder or capacitor bank.
As you enjoy the next Super Bowl, don’t fret over will a power quality issue occur. Simply consider, do you have the information available to understand the cause and find a solution?
