Solar Energy Myths Busted - Utility Lineworkers' Safety is Compromised by Grid-Tied PV
Posted: Tuesday, March 30, 2010
by Ray Boreham
Ivy Enterprises, LLC
There is much skepticism around concerning solar and renewable energy, and this skepticism gives rise to a lot of myths and misinformation. A myth that is very pervasive, but still a myth, nonetheless, asserts that utility lineworkers' safety is compromised when their work brings them into contact with grid-tied PV. A strong assertion, but can it be substantiated? Let's take a look.
When referring to lineworkers' safety being compromised by grid-tied PV, what's specifically being referred to is the inverter, the piece of equipment that converts the DC (direct current) electricity produced by the solar panels into household-friendly AC (alternating current) electricity. Alternating current electricity is the most commonly used form of electricity since it is easier to transport over longer distances, and, as a result, most modern appliances and devices are designed to operate using alternating current.
Direct current and alternating current are basically incompatible, so a method of converting DC to AC must be employed to form a bridge between the two, hence the inverter.
What's In An Inverter?
First of all, why "inverter" and not "converter", since, basically, that's what an inverter does - convert DC electricity into AC? And that's precisely why it's called an inverter as opposed to a converter, because, according to the IEEE (Institute of Electrical and Electronics Engineers) definition, an inverter can only mean one thing, a system, machine or device that changes direct current into alternating current electricity. The basic function, then, of the inverter is to convert DC power from PV panels and batteries (which can only store DC power, and which are used in off-grid and grid-tied systems with battery backup) to AC power that can then be either fed back into the grid or used to power AC loads.
Inverter Types
There are 3 types of inverter - square wave, modified square wave and sine wave. Square wave inverters provide little output and are only appropriate for small loads. Modified square wave inverters can handle large surges and can operate a wide variety of loads, but can be problematic with certain electronic devices, clocks and microwave ovens running on digital timekeepers (which may run fast or slow) and battery packs for cordless tools.
Sine wave inverters are most commonly used in residential solar electric systems since they produce little in the way of harmonic distortion and can run even the most sensitive equipment. This is the only inverter type suitable for grid-tied systems.
Safety First
Inverters have the most safety features of any component in residential systems. They are certified by many of the same organizations that certify most appliances and are required by the IEEE, UL and NEC to automatically disconnect from the grid under various conditions, including inverter malfunction, power outage, voltage irregularities, etc. Not only do inverters have safety devices built into their electronics, but, when working around PV electric systems, utility workers are trained to be extremely safety conscious, and, when conducting line maintenance, are required to ground any conductors, as may be found in inverters, providing an additional safety blanket when it comes to dealing with inverters.
Many households use generators to provide electricity to their homes during outages. If not properly equipped with a transfer switch, the generator may feed electricity back into the grid producing very high voltages. This type of situation has resulted in the death of lineworkers, and one of the reasons for their rigorous safety procedures.
The Record Speaks For Itself
The safety record of inverters is second-to-none, so it's probably safe to assume that in years to come they'll be an accepted and standard part of home electrical systems. There are many dangers facing utility and lineworkers performing their jobs, but inverters and grid-tied PV is not one of them.
No danger in this myth!
If you're ready to get involved in the Green Revolution, and want more information and/or help getting started, including a FREE report, Ray Boreham invites you to click through to http://www.all-you-need-is-solar.com/the only solar power resource you'll need. You'll find a wealth of information and tips on solar and renewable energy at http://www.all-you-need-is-solar.com/
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