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Power outages: blackout vs brownout

What is the difference between a blackout and a brownout?

Quite simply, a blackout is when the power is completely shut off. During a blackout, no electricity, whatsoever, comes through the lines. In other words, all electrical equipment and appliances work the same as if they were unplugged.

In a brownout, there is still electricity coming through the lines, just not as much as usual. In this case, the voltage is reduced. This is a little like using a flashlight with a battery that’s almost dead. When this happens, appliances may or may not work.

While it may seem that some electricity is better than none–particularly if some appliances continue to work—a brownout can actually be more problematic than a blackout. The problem is that some appliances require a very specific voltage. If the voltage in the lines is too much or too little, some appliances can be damaged. If there’s no voltage, the equipment is just turned off; the wrong voltage can make it function incorrectly.

Brownouts and voltage sags

Brownouts are events that can last several minutes or even hours, but there can be times when essentially the same thing happens for just a few seconds. Often, this happens when a large piece of machinery starts up. If you’ve ever seen the lights dim for a couple seconds when equipment is powering up, you’ve experienced what is called a voltage sag.

Voltage sags can be prevented by installing an inverter drive. Electrical engineers recommend these to make large motors start up gradually. This reduces the sudden load and prevents the voltage sag.

The causes of brownouts

Brownouts can happen across a large area—throughout your neighborhood or city—or they can be localized, affecting just your building. A brownout that only affects one building is likely the result of internal electrical issues. Often the root cause is the same—too much demand and not enough supply. However, in this case it is happening with individual circuits in the building.

The larger events are usually caused by a problem with the electrical grid. These usually happen at times when the grid is taxed beyond what it can handle. The generation stations cannot produce enough energy to keep up with the local demand, so there is not enough electricity to go around.

When this happens, electric companies have two options, cutting off power entirely for some customers (so the rest can have electricity), or reducing the voltage so that everyone gets a little energy. The first solution is a rolling blackout. The second is a brownout.

When the grid can no longer keep up with demand, utilities have to weigh the options carefully. Brownouts might not be as unpopular as rolling blackouts, but brownouts can cause more damage. Ultimately, both choices are last resorts, and the utility will only implement them to prevent a widespread and prolonged power outage.

The effects of brownouts

When people hear about brownouts, they typically just think of the lights dimming–and this is indeed where the term “brownout” comes from. While this may be annoying, it is unlikely to cause any harm.

Space heaters, too, will simply decrease their output during a brownout. Because of the relationship of electrical resistance and power consumption, it only takes a small change in voltage to cause a significant decrease in output.

Other equipment, however, can be damaged by the low voltage of a brownout. Motors, in particular, can overheat because the reduced voltage causes them to draw extra current. Even if this doesn’t cause any problems that are immediately noticeable, it can drastically reduce the life expectancy of the equipment. Likewise, electronics can also malfunction from low voltage. In minor cases, this can be a matter of the equipment not functioning properly. In extreme cases, the circuitry can short out.

Blackouts don’t cause the same problems because the power is off entirely. However, some of the same problems can happen when electricity is turned back on suddenly. The sudden surge can be harmful to some devices.

Protecting your equipment and appliances

Even if the device has a standby mode for when it is not in operation, it can still be susceptible to outages. To protect your electrical equipment and appliances, therefore, you should always unplug them when not in use–or just at the start of the interruption.

Sometimes, however, this is not practical.

An uninterruptible power supply (UPS) is one solution to this. In addition to providing battery backup in case the electricity goes out, these devices can also make up the difference when voltage gets too low. Likewise, an undervoltage relay will shut off the current entirely if the voltage drops too much. These can be costly solutions, but either will protect the equipment in your home during a brownout.

For motors, you can install thermal protectors that detect dangerous temperatures. When temperatures reach an unsafe level, the system will shut off the motor to save it from damage. Throttling the equipment can also help if shutting down is not an option.

Who do you call when there’s an outage?

In the event of an outage–a brownout or a blackout–you should report it to your utility. If you are unsure, they can tell you if the problem is with the grid (or if it’s just something within your building) as well as provide you with whatever information they have on when the power might be restored.

Most utilities will also allow you to sign up for email or text notifications about scheduled outages. This is an easy way to stay informed about potential problems so that you can prepare as best as possible.

Does your provider affect how quickly power will be restored?

People who shop electricity plans or natural gas plans often hear the myth that, in the event of an outage, power will not be restored as quickly if they change providers. This is simply not true. First off, the provider isn’t the one who handles outages; that is the job of the utility. Second, the utility can’t legally show preference to customers of one provider over another. Most importantly, the people in your neighborhood could each use a different provider. There’s just no way the utility could single out customers of one provider to show them preference.

If you shop natural gas or electricity plans, you don’t have to worry that the new provider will make any difference in an outage.