Glossary of Terms

AC – Alternating Current
Electrical current that continually reverses direction, with this change in direction being expressed in Hertz, or cycles per second.

Ampere
Quantitative unit of measurement of electrical current. Abbreviated as Amp or A.

ANSI C62.41-1991
A technical Standard dealing with the electrical powerline surge environment and originally published by the Institute of Electrical and Electronic Engineers (IEEE) as IEEE 587 in 1980, updated in 1991 and now recognized as an American National Standard.

CID
The Federal government develops CIDs (Commercial Item Descriptions) for purchasing commercially available products. In 1996, they issued a CID for the purchase of powerline surge suppressors.

Capacitor
An electrical component which stores electrical voltage, and also resists electrical voltage changes.

Certification
The Federal government, UL and other agencies establish Standards of safety and performance. Testing labs such as ETL and UL can Certify said performance, endurance, and safety.

Clamping Level (Clamping Onset Level)
This generally is used to describe the voltage level which causes the surge diversion device to start to divert surge energy. A related, but more important parameter is the Suppressed Voltage.

Clamping Time
The response time it takes a surge suppressor to go from its “off” condition to “on” condition in clamping or diverting surges when a surge voltage exceeds the clamping onset level.

Class 1, Class 2, Class 3
Let-through voltage, or Suppressed Voltage Rating (SVR) performance Classes defined by the Federal government CID in their powerline surge suppressor specification. Class 1 products have a SVR of 330 volts (the best rating). Class 2 products have a SVR of 400 volts, and Class 3 have a SVR of 500 volts. The Class of a given product may change depending on the Grade it is tested to, since the test conditions are different for different Grades, and this may influence the SVR, hence the Class.

Combination Pulse
A high energy test pulse specified by ANSI C62.41-1991. Also called a “unipolar pulse”.

Common Mode Voltage
A voltage on the neutral wire of the power wiring, compared to the ground wire, where the ground wire is assumed to be the reference.

Current (expressed in units of amperes, or simply amps)
Current is the electrical equivalent of water flow. Current will flow in a circuit when the applied voltage exceeds a certain level, as dictated by the various components in the electrical circuit.

DC – Direct Current
Electrical current which flows in one direction.

Degradation
Undesirable performance changes.

Disruption
Undesirable disturbance.

EMI – Electro-Magnetic Interference
Electrically induced noise or transients.

Energy (expressed as joules or watt-seconds)
1 joule = 1 watt-second. This measure of energy is the product of electrical power and time. A 60 watt light bulb turned on for 1 second expends 60 joules of energy.

Fault
A fault is a wiring problem such as a broken wire, or wires touching typically due to storm damage, requiring physical repair.

Filter
An electronic device that allows only certain frequencies to pass.

Frequency
Voltage can be continuous (Direct Current or DC) or alternating (AC). The frequency of alternating voltage is the number of times per second that it changes polarity from positive to negative. Most power voltage in the US is delivered at 60 Hertz (60 changes from positive to negative per second).

Grade A, Grade B, Grade C
The Federal CID defined three grades of surge suppressors based on endurance testing at several surge test levels.

  • Grade A is for 1,000 surge endurance with 6,000 volts, 3,000 amperes applied.
  • Grade B is for 1,000 surges with 4,000 volts, 2,000 amperes.
  • Grade C is for 1,000 surges with 2,000 volts, 1,000 amperes applied.

Ground
For safety reasons, electrical systems in the USA have a wire connected to earth ground at the service entrance. This “ground” wire is run along with the two current carrying wires. Most electrical equipment is electrically connected to this wire when a three wire plug is used to connect the equipment to the electrical power receptacle. This third, non current carrying conductor which is connected to earth ground at the service entrance of a building is often referred to as “ground”.

Ground Contamination
The designers of electrical equipment assume that equipment connected to the electrical ground wire are at “ground potential”, that is, all at the same voltage. When equipment is electrically interconnected with audio, video, or data cables, and surges or other noise is injected into the ground wire, ground contamination occurs.

Hertz
Unit of measure of the frequency of alternating current.

IEEE 587-1980, ANSI C62.41-1991
A technical Standard originally published by the Institute of Electrical and Electronic Engineers (IEEE) in 1980, updated in 1991, and now recognized as an American National Standard.

Impedance
Similar to electrical resistance since it is a measure of the opposition to the flow of electricity. Impedance is meaningful only for alternating current, and changes value as the frequency of the electricity changes.

Inductor
An electrical component which opposes the flow of electric current. An inductor has the property of impedance, the opposition to the flow of electric current. Impedance changes value with the frequency of the applied electricity.

Interconnected Equipment
Equipment which shares at least 1 common electrical connection other than the power wires. A printer and a computer share a “printer cable” for instance.

Joules
A unit of energy, also known as watt-seconds. Some suppressors are rated in joules, meaning that if a surge exceeds the joule rating, the suppressor will likely be damaged. The joule rating of many suppressors deteriorates with use.

LAN – Local Area Network
An interconnection of computers, printers and other peripherals permitting the sharing of hardware and software resources.

Let-Through Voltage
The peak voltage that is let through a surge protection device from a surge to the protected equipment. The theoretical lower limit is about 180 volts peak for standard 120 volt AC power. Lower is better. Also called SV (Suppressed Voltage) by UL. An important measure of suppressor performance.

Load
An electrical device connected to a power source.

MOV – Metal Oxide Varistor
A component which behaves like a low value resistor when a certain voltage threshold is exceeded. These components “wear out” with use and should be replaced periodically.

Mode
Mode 1 and Mode 2 are used by the Federal surge suppressor CID purchase specification. Mode 1 is the ground wire protection mode (no surge diversion to the ground wire). Mode 2 permits ground wire contamination, and is sometimes referred to as “all mode” suppression, or ground contamination mode.

Neutral
One of the wires used in the USA to distribute power within a building. The neutral wire is generally connected to earth ground at a building service entrance, but unlike the ground wire, the neutral wire also carries load current.

Noise
An undesirable signal that is irregular and is riding on top of the desired signal.

Normal Mode Voltage
Voltage on the Line or Hot wire of the power wiring, compared to the neutral wire.

NRTL
Nationally Recognized Testing Laboratory, one example of which is Underwriters Laboratories, Inc. (UL).

Oscilloscope
A measuring instrument which gives a visual display of voltage, current, or power waveforms.

Oscillogram
A picture of a voltage, current or power waveform taken from an oscilloscope.

Peak Current
The maximum current value as measured from a reference in a given period of time.

Power (expressed in units of watts)
Power is the product of volts and amps. A circuit that will draw 1 ampere of current when 100 volts is applied will dissipate 100 (volts) X 1 (amp) = 100 watts.

Pulse
A pulse is generally a unipolar voltage or current with defined characteristics, which occurs infrequently.

RFI
Radio Frequency Interference. High frequency interference that can appear on power wires.

Resistance
A property of electrical conductors or electrical insulators which characterizes their ability to conduct or resist the flow of electricity.

Ringwave
A low-energy test waveform specified by ANSI C-62.41-1991.

SPD
Surge Protection Device.

SV
Suppressed Voltage, see Let-Through Voltage.

SVR
Suppressed Voltage Rating. A series of discrete voltages used by UL to designate the performance of a surge suppressor. 330 volts is the lowest (best), 400 volts is the next category, 500 volts is a third category. The SVR of a product to UL 1449 testing will likely be different from the SVR for the Adjunct Classification testing, since this UL 1449 Adjunct testing is at higher current levels, where the performance of a product may be different. When asking about SVR, be sure to specify whether the SVR is for UL 1449, or the UL 1449 Adjunct Classification testing.

Sacrificial
A term used to describe MOV based surge suppressors since they “wear out” with use.

Series Mode
Describes filter technology which opposes surge current and voltage while filtering off surges and noise, as opposed to shunt mode which diverts surge current and clamps surge voltage.

Service Life
The number of surges of given magnitude that can be suppressed by the suppressor, a measure of reliability. The Federal CID specifies minimum service life using a Grade A (best), Grade B, and Grade C classification method, with performance certified by a NRTL such as UL.

Shunt Mode
A form of surge suppression which diverts surge current and clamps surge voltage.

Sinewave
A fundamental waveform produced by periodic, regular oscillation that expresses the sine or cosine of a linear function of time and space or both.

Single Phase
The portion of a power source that represents only a single phase of the three phases that are often available.

Spike
See surge

Surge
A brief burst of high level, high frequency voltage and current in an electrical circuit lasting for less than 1% of the power wave cycle duration.

Swell
A momentary voltage increase of the power voltage, lasting up to several seconds.

TVSS
Transient Voltage Surge Suppressor.

Transient
An abnormal and irregular electrical event, such as a surge.

Transient Attenuation
The reduction of a transient’s magnitude.

UL
Underwriters Laboratories, Inc.

UL 1283
The safety testing Standard for filters.

UL 1449
A safety testing specification for powerline surge suppressors, originally developed by UL.

UL 1449 Adjunct Classification
Since the UL 1449 specification is a safety specification, and not a performance specification, and since the need exists for performance qualification, UL is offering an optional testing service to manufacturers as an adjunct (addition) to their UL 1449 Safety Listing. The Federal government is using this UL 1449 Adjunct Classification to define various endurance and performance levels for their powerline surge suppressor needs, in their surge suppressor CID.

Unipolar Pulse
A high energy test pulse specified by ANSI C62.41-1991. Also called a “combination pulse”.

Voltage (expressed in units of volts)
The quantitative measure describing electrical force or potential. Voltage is the electrical equivalent of water pressure. Electrical voltage can initiate damage to electrical devices, just as water pressure can burst pipes if the pressure is too high. Below certain voltage levels, no damage will occur. Above certain voltage levels, damage can occur.

Voltage Reference
A voltage point from which a measurement is taken.

Voltage Threshold
The voltage which causes the connected circuit to change its response.

Watts
The unit of measure of actual power. Watts are the product of volts times current.

Waveform
The graphic form of an electrical voltage, current or power.

WVR
Wide Voltage Range. A filter technology that tracks powerline voltage over a very wide voltage range, maintaining effectiveness over that range.