The impact of Superstorm Sandy is, unfortunately, a perfect illustration of an unreliable electrical distribution infrastructure. Without power, little else works—from the cellular communications that have replaced landlines for many people to heating that depends on electricity to operate blowers.
Most people think of the public electrical infrastructure first—the local utility companies that operate the transmission and distribution networks. In many disasters, such as ice storms or wind storms, it is these lines that are impacted; and when they are repaired, power is restored to residences.
Sandy presented a more severe form of damage. In addition to the public electrical infrastructure, there was widespread destruction of the private electrical infrastructure that exists within each house or building. When this damage occurs, recovery is usually much more difficult because:
- The damage is much more diffuse—in many different buildings rather than concentrated in key lines and substations
- The damage is likely to be hidden and inaccessible within the structure of a building.
- The individual owners of the buildings are unlikely to have the technical knowledge employed by the utility. This lack of knowledge can lead to unwise and unsafe recovery actions.
Electrical Equipment Safety
Safety is a significant issue when recovering from the flooding that occurs during a storm like Sandy. Electrical and electronic equipment that has been submerged should never be re-energized without being thoroughly inspected by competent technical personnel. Equipment that has been submerged is likely to have debris and damaged electrical insulation that can cause fires and shock hazards when the devices are energized.
This applies as much to electrical equipment as it does to the wiring of a building. All manufacturers of circuit breakers, for example, require that those devices be replaced after being submerged. The corrosion and dirt left behind affects their calibration and ability to trip, leaving them ineffective for their critical protective functions. The enclosures that hold the circuit breakers can sometimes be cleaned and refurbished by factory service personnel, but this is usually only cost effective for the largest gear. For smaller load centers, replacement will usually be less expensive.
If the infrastructure within a building has not been damaged, there is still the issue of providing electrical power until utility service is restored. Hospitals and other critical facilities have long had onsite standby generators. As electricity has become more vital to leverage other energy sources, more facilities are required to have at least some level of standby generation. For example, Florida requires some gas stations to have generators to run the pumps in the event motorists need to fuel up for an evacuation.
Backup generation is becoming just as important in emergency preparedness as having a three-day stockpile of food and water. Approximately two percent of U.S. homes now have some backup generation capability, and this percentage is growing. Most often the generation capacity is not enough to replace the utility completely, but it is enough to operate HVAC blowers for heat, charge phones, and run refrigerators so food won’t spoil.
Standby generators can range from small portable units to larger machines that are permanently wired to the building. In all cases, there are a few key concerns that must be addressed:
- There must be a means of transferring the load from the normal utility source to the generator. For a portable unit, this can be as simple as unplugging an appliance from a wall outlet and plugging it into the generator, but for a larger generator that is wired into a building electrical system, some type of transfer switch will be needed. This may be a manual transfer switch that requires someone to physically operate the switch or an automatic transfer switch that will switch power to the generator when it is running and then back to the utility when it is restored. No human action is needed to make these switches. The transfer switch also includes an interlock that keeps the generator from back feeding power to the utility.
- It is essential that generators only be connected to a building electrical system using a listed transfer switch installed by a knowledgeable electrician. If a user connects a generator to the facility wiring without disconnecting the utility, dangerous conditions can result. First, power going out on the utility lines causes them to become energized; this can electrocute line workers. Second, when power is restored it will be out of phase with the generator and will likely cause catastrophic destruction of the unit, e.g., a fire or flying shrapnel.
- More sophisticated transfer switches can warn of overload conditions or even rotate power among loads to optimize use of the generator. Some building owners or homeowners opt to install generators large enough to completely replace their utility feed, but in many cases this expense is not warranted. Smaller generators can be used to operate only key loads; however, it is possible to overload those generators if too many appliances are switched on. While the generator will have circuit breakers or shutdown devices that will intervene to prevent damage to the unit, this will cause another power disruption and key loads, such as freezers, may be left without power.
- Obviously, there must be enough fuel to operate the generator for the intended standby period. Depending on the type of engine on the generator, this may be gasoline, diesel, propane, or natural gas. If natural gas is used, an evaluation of the stability of the gas main during a widespread outage must be made.
There are two more electrical system upgrades that building owners and managers should consider. These further protect the building and the appliances and loads within.
The first is premises-wide surge protection. Surge protectors are typically installed in an enclosure with circuit breakers to protect loads, especially sensitive ones like TVs and computers, from damaging electrical pulses. Pulses are often caused by lightning or switching transients generated by reclosers or feeder switches in the utility system. During power restoration, surge protectors continue to guard from electrical surges created as work is done on the utility lines.
The second improvement is the addition of advanced arc-fault and ground-fault protection for circuits that supply power within the building. This protection is provided by circuit breakers that contain new electronic sensing technology that was not available 10 or 15 years ago. The improved protection can sense broken wires or damaged electrical insulation and remove power from a circuit before a fire begins. In most new residential construction, devices offering this higher level of protection are required by code, but they can also be retrofitted into older homes and businesses. Such a retrofit should be considered as a means of hardening the building electrical infrastructure.
Preparing for Generator Use
To assure you are prepared in case of a disaster, follow these next steps:
- Evaluate the size of generator needed based on key loads required to run during an extended outage.
- Decide if the generator will be fixed mount or portable.
- Decide on the type of engine and fuel it will use.
- Look at the physical placement options for the generator. This is clearly needed for fixed mount units, but there must also be a plan for portable units. Indoor operation is never an option as it is extremely unsafe.
- Consider how the generator will be connected to appliances. If existing building wiring is used, decide on the correct type of transfer switch—manual or automatic—and the features required.
- Look at the connection point in the building electrical system. Determine if it is possible to electrically isolate and connect to a point that is higher than any anticipated flood waters.
- Find a qualified electrical contractor that will install the transfer switch and generator and see that it is inspected as required by local codes.
- Verify adequate fuel supply and test the generator and transfer switch on a regular basis to verify correct operation.
- Consider adding premises-wide surge protection at the circuit breaker enclosure.
- Consider adding arc-fault and ground-fault circuit protection in the electrical infrastructure.