What is a Surge?

Surges, or transients, are brief overvoltage spikes or disturbances on a power waveform that can damage, degrade, or destroy electronic equipment within any home, commercial building, or manufacturing facility. Transients can reach amplitudes of tens of thousands of volts. Surges are measured in microseconds.

Every piece of electrical equipment is designed to operate at a specified nominal voltage such as 120v ac, 240v ac, 480v ac, and so on. Most equipment is designed to handle minor variations in their standard nominal operating voltage; however, surges can be very damaging to nearly all equipment.

Sources of Surges/Transients

A common source for surges generated inside a building is devices that switch power on and off. This can be anything from a simple thermostat switch operating a heating element to a switch-mode power supply found on many devices. 

Transients can originate from inside or outside a facility:

Inside: 

• Inductive coupling
  Whenever electric current flows, a magnetic field is created. If this magnetic fields extends to a second wire, it will induce a voltage in that wire.  This is the basic principle by which transformers work, where a magnetic field in the primary induces a voltage in the secondary.
  

  • Examples include: Elevators, heating ventilation and air conditioning systems (HVAC with variable frequency drives), fluorescent light ballasts, variable speed drives, welders, or compressors, can all create transients within a facility. 
    

• Magnetic coupling
  Wires that run adjacent to one another in a building can magnetically couple transients.
  

• Static electricity.

Outside:

• Utility grid switching.

• Magnetic coupling - lightning.

• Direct lightning strike.

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Are All Power Quality Problems Surges?

No. Surges, or transients, do not explain all of the voltage related power quality issues in the world today. 

• Drops in voltage that last from a fraction of a second to as much as a few seconds are known as voltage sags.
  

• Drops in voltage that last from several seconds to minutes are known as brownouts. Both sags and brownouts are more damaging to motor loads than they are to microprocessor based equipment. 
  

• Sustained over-voltages are known as voltage swells and can last from a few seconds to several minutes. Sustained over-voltage conditions can be very damaging to many types of equipment, but are not nearly as frequent as transients or surges.

Power outages are another type of power quality issue that can last from several seconds to hours or even days. Transient voltage surge suppressors do nothing to prevent the harm that can be caused by power outages. 

Equipment can be protected from the damaging effects of power outages by utilizing either uninterruptible power supplies (UPS systems) or standby power generating equipment. 

Many hospitals and businesses will incorporate surge suppression equipment on panels that are being fed by a standby generator or a UPS system.

Many other power quality issues exist that all users must be aware of. A partial list of these problems includes:

• Harmonics

• Circulating ground currents

• Noise

• EMI/RFI interference

Power quality products cannot cure all of these issues. Proper diagnosis is the key to good power quality and the minimization of lost productivity.

Since it is impossible to prevent voltage surges from entering a building or  occurring inside a building, surge protection was invented. The function of the surge protector is to stop or limit the effects of less-than-perfect power quality on solid state electronic devices.

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