Secondary Surge Arrester Series
Glossary


Transient
Transients are defined as power line disturbances that occur in less than 1/2 cycle (less than 8.33 milliseconds). They can occur anywhere on the AC sine wave and can be either positive (spike), or negative (notch). A Secondary Surge Arrester will protect against transients.

  Voltages Surges, Sags Or Brownouts

A surge is an increase in voltage that occurs over a period of time greater than 1/2 cycle (8.33ms). A voltage sag or brownout is the opposite of the surge and is a decrease in voltage that occurs over a period of time greater than 1/2 cycle. A Secondary Surge Arrester will not protect against surges, sags or brownouts.
Causes Of Transients
Demand power load switching by utility companies
Utility power load correction
Nearby lightning strikes
 Transient Duration In Relationship To Time
Second = 1.0 Microsecond = .000001
Millisecond = .001 Nanosecond = .000000001
Transient Voltage Surge Can Be:
(1) 300V peak or more but typically 1200V to 5600V in severity.
(2) 10 ns to 50 ms but typically are 1 µs to 1 second in duration.
Equipment Affected By Transient Voltage
Computers Dishwashers Micro-processors Washing Machines
Microwaves Clothes Dryers Copy Machines Medical Equipment
Dairy Equipment Modems Thermostat Controls Oil Field Equipment
Televisions Fax Machines Stereo Equipment Pumps
Refrigerators Air conditioners Microwves VCR's & Cable TV Boxes
What a Surge Arrester Should do
Clamp transients
Take repetitive hits
Operate in parallel with the load
Respond Rapidly Be maintenance free
ANSI/IEEE STANDARDS
C62.1 - 1989 Standard for Gapped Silicon-Carbide Surge Arresters for AC Power Circuits
C62.1 I - 1987 IEEE Standard for Metal-Oxide Surge Arresters for AC Power Circuits
C62.41 - 1991 IEEE Recommended Practice on Surge Voltages in Low-Voltage AC Power Circuits
Voltage Wave Form 1.2 x 50
Leading edge builds from 10% to 90% of peak in 1.2 microseconds (µs). Leading edge from 0% through peak and decrease to 50% in 50 microseconds. This is considered by many experts to be about the worst case transient a secondary surge arrester would typically experience.
Current Wave Form 8x 20
Leading edge builds from 10% to 90% of peak in 2.0 µs. Leading edge from 0% through peak and decrease to50% in 20 µs.
Joule
Unit of energy equal to one watt-second.
Leakage Current
The AC or DC current flowing from input to output and/or chassis of an isolated device at a specified voltage.
Lightning Arrester
See Secondary Surge Arrester
MCOV (Maximum Continuous Operating Voltage)
The maximum designated RMS value of power frequency voltage that may be applied continuously between the terminals of the arrester.
MOV (Metal Oxide Varistor)
Metal Oxide Varistor. A solid state component designed to handle large amounts of current which reacts in the low nanosecond time range. Shunts or directs large amounts of current to ground when voltage exceeds a threshold level above the MCOV.
Peak Value
Maximum (crest) value of a wave form, surge or impulse, reached during a specific particular cycle or operating time.
RMS Voltage
Applies to an AC sine wave, the RMS (Root Mean Square) is also known as effective voltage. i.e. 120 VAC 60Hz sinewave would have a peak voltage of 169.7 or 1.414 times the RMS voltage. Conversely the RMS voltage is 0.7071 times the Peak Voltage.
Surge Arrester
A protective device for limiting surge voltages on equipment by diverting surge current and returning the device to its original status. It is capable of repeating these functions as specified and is also called a lightning arrester.
Classification of Arresters (IEEE)
  1. Station - (Utility / Power Company)
  2. Intermediate - (Utility / Power Company>
  3. Distribution - (Utility / Power Company>
    bulletHeavy Duty
    bulletNormal Duty
  4. Secondary - 1, 2, 3a, 3b are designed for use by the Power Utility companies. Guardian Angel manufactures Secondary Surge Arresters for use on residential, industrial and farm electrical equipment.
IEEE C62.41
Category A
Description: Long branch circuits more than 10 meters (33 feet) from a Category B location.
UL Test: Ring wave with 6,000 volt, 200 Amps
Category B
Description: Main Feeder Circuits, short branch circuits, distribution panels, heavy appliance circuits plus receptacles than 10 meters (33 feet from a category C circuit.
UL Test: Ringwave of 6,000 volts and 500 amps plus impulse wave of 6,000 volts and 3,000 amps.
Category C
Description: Outside and service entrance main service panels and any overhead lines to separate structures (weatherhead).
UL Test: Impulse of 10,000V and 10,000 Amps.


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