Lousy Power and Electronics Don't Mix

Today's fueling stations and c-stores require sophisticated electronic equipment to provide the operators with access to detailed site information, both on site and remotely, that allow them to operate their businesses at optimal levels and serve their customers more efficiently. INCON's Rick Sales examines how power quality is critical to making equipment run at the highest possible performance levels.

Electricity needs to be managed and controlled

It’s the middle of the summer. It’s hot outside and people are out and about. Traffic at your stores is good. People are gassing up and buying soda, chips and ice—non-stop. Everything is as it should be . . .

. . . Except for the last hour you’ve had problems authorizing credit card transactions. It’s been sporadic, and mostly annoying, but several stores have reported the problem. You don’t know it yet, but in five minutes power is going to go out in the south end of town, leaving 10 of your stores in the dark. It won’t be out for long this time—only five minutes. Just enough time for everyone at your stores to leave. When the power comes back, a voltage spike will knock out two dispensers and one point of sale device, generating a series of emergency to-do items for you. Until tomorrow, that is, another hot summer day. . ..

How likely is this to happen to you? Ten or 15 years ago, highly unlikely. However, many fear that, today, the quality of our electric power is declining and will continue to deteriorate. Much of the problem is caused by the process of deregulating the electric power industry. In fact, in the February 13 edition of The Wall Street Journal, an article entitled “Electric Power Grids’ Reliability Erodes” talks about deregulation and its impact on power quality. The article expresses serious concerns about the lessons learned from last summer’s major electricity outages in the US, and the fact that little has been done to fix the underlying problems.

The paper makes reference to a study conducted for the Department of Energy, that evaluated eight “power reliability events” last summer. It notes that deregulation efforts, underway in 25 states, have made it harder for power companies to respond to periods of peak power demand. Furthermore, it points out that partly because of deregulation, little attention has been paid to fixing aging power distribution systems that are not big enough to bear today’s traffic.

Finally, the short article brings home the possible risk of serious economic impact caused by deregulation of the power industry. It notes that our increasing reliance on electronic gear makes the economy much more sensitive to power outages and fluctuations.

What about our reliance on electronic gear? Today, your convenience stores are filled with electronic devices, some of which perform critical functions for you, and many of which need to communicate with other devices as part of their everyday function. Throughout the industry, the same is true. Computers, fax machines, modems, video cameras and lotto machines talk to one another while they engage in their version of electronic commerce..

Therefore, we can conclude that our industry has an increasing requirement for reliable, stable, clean power, but can expect to operate in an environment where dirty power and/or unstable and unreliable power may be supplied to us with increased frequency.

Fortunately, you can take steps to protect your assets and shield yourself from some of the negative economic side effects of deregulation. If you are building new stores, you should give serious consideration to the issue of surge protection and power conditioning in designing your stores’ electrical system. Many electrical contractors can integrate excellent panel-mounted solutions that can provide you with partial- or full-site coverage suited to your individual needs.

If you operate one of the already existing 180,000 convenience stores and retail fueling points in the US and Canada (many of which were designed with no consideration given to the effects of eroding power quality), you can choose from several retrofit devices that will provide you with excellent protection—without the need to re-design your electrical system.

The Power Sentinel. Coutesy of INCON

The technology
Surges and spikes are individual, one-time “events” that take place on the voltage “waveform.” Lightning strikes, switching transients and equipment starts can all cause changes in voltage many times the amplitude of the normal waveform.

Not only is the convenience store full of electronic devices today, but, as an industry, we are continuing to ask for, develop and market smarter and more accurate electronic devices to improve our company’s competitiveness.

The requirement we place on our power generation and distribution system is clear: we don’t just need more power to operate our business; we need clean power to operate the types of devices that we use today to run our business.

Surge protection devices frequently use metal-oxide varistors (MOVs) as their main protection component. MOVs are placed in a variety of configurations, depending on the system’s phase and voltage characteristics. The MOVs act as resistors whose current increases sharply as you near Maximum Continuous Operating Voltage (MCOV). As a result, MOVs are fast and can shunt large amounts of energy.

In its most basic description, an MOV is made of a ceramic material (that under normal conditions does not conduct electricity), “sandwiched” in between two metal plates. The INCON Power Sentinel™, for example, uses MOVs in parallel with the load to protect a site from the damaging effects of externally generated spikes and surges. In parallel means that electricity flows into the protective unit and your load simultaneously. Under normal voltage, the MOVs act as open circuits in parallel with the load, and, therefore, have no effect in the circuit.

As the voltage across the load begins to rise during a surge or spike, the MOV initially remains an open circuit. Once the voltage reaches the MCOV threshold, the ceramic material begins to conduct electricity, and the MOV becomes, in essence, a short circuit. By acting as a short circuit, the additional current generated by the voltage spike is channeled through the short, and the voltage increase is essentially stopped at a level that is low enough to prevent damage to downstream equipment. This can happen slowly (a voltage surge) or instantaneously (a voltage spike). In either case, the MOV can respond in as little as 10 nanoseconds.

Another way of configuring surge protection devices is to use MOVs in an in-series configuration with the load. In-series means that the electricity flows through the unit before it gets to your load. This type of configuration can provide protection from internally, as well as externally generated surges. However, due to cost and complexity, series installations are generally limited to a handful of circuits. Moreover, in the event that an incoming voltage spike is large enough to permanently disable the MOVs, the parallel installation allows you to have power after the spike, where the series installation leaves the protected circuits without power until the MOVs are replaced.

Let’s set surges and spikes aside for a moment and talk about power noise and harmonics. Noise and harmonics are undesirable additions to the power voltage/current waveform that generally tend to be random in nature. Noise can be continuously generated, or, depending on the condition of the power grid, it can be the result of periodic disturbances.

In general, large inductive motors are not affected by moderate amounts of noise in their power supply. However, small amounts of noise can affect the operation of some electronic equipment, such as computers and embedded electronics. These devices need a stable power source to operate reliably. In the convenience store, the most common manifestation of power noise becomes evident in the form of communication errors. Noisy power tends to interfere with all types of communications, not just the ones that take place over power lines. Modems, in particular, can be very sensitive to noise and fluctuations in voltage.

Different equipment vendors’ technologies achieve noise suppression and harmonics reduction in different ways. The INCON Power Sentinel unit achieves this via four mechanisms:

• Primary Power Factor Capacitors
• Secondary Capacitors installed to provide low  impedance to high frequency noise
• Filtering Inductors
• MOVs for surge suppression

These mechanisms allow the unit to effectively smooth out the voltage/current waveform and filter out other noise. The resulting waveform provides considerably less noise to the circuit than before processing.

The bottom line
Power surges, spikes, noise and harmonics have been with us since the inception of the North American power grid. They are on the rise because of the lack of upgrading of some of the more aging parts of our power generation and distribution network. They are even more relevant today because of our increased dependence on electronic devices for commerce.

The bottom line is that for today’s convenience store and gas station operator, power quality is a real issue with real economic implications. Fortunately, well-understood and commercially viable technology exists today to help protect your investment from changes in the quality of your electric service.

Solutions available in the market today vary in complexity, level of protection and costs. Some solutions tend to be more suitable for retrofitting existing sites while others provide real benefits to new installations. Depending on your power quality environment, many of the available systems provide for a quick payback, and all of them give you more protection than the alternative—hoping that the deregulation of the electric power industry does not affect you.

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