An agreement on common terms to describe electrical overstress has largely eluded the industry; however, the Institute of Electrical and Electronic Engineers (IEEE) and the American National Standards Institute (ANSI) refer to "Surge Voltages" and "Switching Transients" in their discussions of recommended practice for protection of electronic equipment in an AC power and Data line environment.

Blackout: Extended zero voltage conditions caused by lightning, generator failure, transformer failure, and ground faults.

Breakdown Voltage: Voltage at which active device conduction begins (See I Test).

Brownout: Long term under-voltage caused when peak demand exceeds generating capacity.

Capacitance: Capacitance between two terminals measured at specified frequency and bias.

Category or Zone Protection: Category A: long branch circuit (more than 30 feet from a category B location). Category B: Major feeders and short branch circuits (distribution panels, industrial bus/feeder, heavy equipment service location) Category C: outside service entrance (main service panel and overhead lines to separate structures).

Clamping Action Turn-On: Threshold voltage at which the suppression device starts to conduct or turn-on. Protection starts at this level; however true protection is specified by the maximum clamping voltage.

Clamping Voltage: The Peak voltage appearing across the device when measured at conditions of specified pulse current amplitude and specified waveform(8/20). It is usually the same as "suppression voltage". "Caution"; however, some companies (Not CCI) use the term to mean the breakdown voltage at very low current (1 milli-Amp). Be certain performance specs state current/voltage waveforms and values.

Combination Wave: ANSI/IEEE waveforms of open circuit surge voltage and short circuit current. The combination wave is supplied by a generator that applies a 1.2/50 microsecond voltage wave across an open circuit and an 8/20 microseconds current wave into a short circuit.

Discharge Current: Maximum peak current or transient current at specified waveform (with line voltage applied) without causing device failure.

EMI/RFI: (Electro Magnetic Interference / Radio Frequency Interference) Inductive or Radio Frequency electrical noise commonly occurring which can create erratic behavior in electronic circuits.

EMI/RFI Noise Rejection: Most suppressors are poor filters of EMI/RFI noise. This is because if any filtering is added it is just a capacitor and then usually an inexpensive and ineffective one with high ESR value (Internal Impedance at RFI levels or poor dv/dt response). A few companies like CCI offer true balanced dual L-C networks designed for filtering.

Expected Life: Number of years of expected service based on probable exposure to known electrical stress, usually lightning activity since this is the worst case threat.

Failure Mode: The status of protected equipment in the unlikely event of a surge suppressor failure (due to surges of over-voltages beyone the suppressor's rated capability). Equipment can either be left operating but unprotected, or be removed from service (the suppressor will intentionally cause loss of power or signal by tripping/clearing a system breaker/fuse). CCI manufactures suppressor devices with both types of failure modes.

Glitch: A transient over-voltage.

I Test or I t: DC current used to measure the breakdown voltage at which conduction occurs, changing the conduction characteristics of the TVSS from the leakage region (static resistance) to avalanche (dynamic resistance). It is recommended that the test current (It) to be at 1mA to ensure a device avalanche conduction and minimum change due to any thermal effects.

Joule Rating: Peak energy rating at 10/1000us wave shape applied (along with rated rms. voltage) without causing device failure. The higher the joule rating the longer the expected life of the device. In some devices joule rating will effect clamping voltage performance.

Latent Failure: Damaging electrical overstress (transients) can cause upset or go undetected yet degrade electronic equipment. A known phenomena where equipment that has been exposed to electrical overstress typically fails within 6 months. Generally components within damaged equipment continue to fail at an unpredictable rate.

L-G: Line to Ground.

L-N: Line to Neutral.

L-L: Line to Line

MCOV (Maximum Continuous Operating Voltage): Maximum system operating voltage which may be applied to the suppressor.

Maximum Transient Current: Maximum peak current (see Surge Current) that may be applied to a device using an 8/20 micro seconds current waveform without causing device failure.

Maximum Transient Voltage: Maximum Voltage (see Surge Voltage) that may be applied to a device at a specified waveform without causing device failure.

Modes of Protection: Common mode means lines compared to ground. Normal (Differential) mode means across the lines. For most AC circuits, CCI protects four modes: Line to Ground, Line to Neutral, Line to Line and Neutral to Ground.

N-G: Neutral to Ground.

Noise: Various high frequency impulses ranging from a few mill-Volts to several volts in amplitude.

Operating Line Voltage: DC voltage or rms voltage normally expected to be applied to a device.

Operating Line Voltage Rating: Maximum continuous sinusoidal rms voltage which may be applied to a device.

Peak Power: Peak voltage x Peak current. Used to specify maximum power a suppressor will handle in Watts.

Response Time: This has become a game among transient suppressor suppliers as A nano-second is several times faster than any transient commonly found in the real world. It is the time between the point at which the wave exceeds the clamping voltage level and the peak of the voltage overshoot.

Reverse Leakage: Current flow through a suppressor in the reverse bias or normal operating circuit configuration. High leakage can shorten life or interfere with protected electronic equipment.

Reverse Standoff Voltage: The applied reverse voltage to assure a non-conductive condition.

Sag: Short term under-voltage occurring when peak demand exceeds generating capacity sometimes caused by lightning when primary gas suppressors fire.

Sine Wave Tracking: ANSI/IEEE, UL and the International Standard IEC does not make recommendations regarding this method of suppression. This is because the Peak suppressed Voltage (combination of the operating voltage plus suppressed transient) value is the performance criteria for protection. High speed noise contained within a waveform is best eliminated through good filtering design.

SPD: Surge Protective Device (See TVSS)

Spike: A transient over-voltage.

Suppression Voltage: The maximum peak voltage that will be seen across the active terminals of a suppressor at a specified waveform and source current. It is the "Let through" or remnant voltage the suppressor allows to be applied to protected equipment, a key criteria in performance specification.

Surge: Transient over-voltage with a duration of less than 8.3 mS (one half cycle of the normal mains waveform).

Surge Current: ANSI/IEEE C62.41.2-2002 provides test waveform recommendations for evaluating surge suppressors. Test waveform is (8 x 20 micro-seconds) 8 milli-seconds rise time and 20 micro-seconds from rise time start to 50% of fall (decay) time applied as a current wave into a short circuit.

Surge Voltage: Test ANSI/IEEE C62.41.2-2002 waveform is (1.2 x 50 micro-seconds). Rise time of 1.2 micro-seconds and 50 microseconds to 50% decay time.

SVR (UL Suppressed Voltage Rating): Determined through testing by regulatory agency (UL, CSA, VDE, Etc.) or independent laboratory to specifications of IEEE/ANSI, IEC and UL. For permanently connected devices UL performs tests using a combination waveform 500 Amps/6000 volts.

Transient: See Surge

TVSS: (Transient Voltage Surge Suppressor) A protective device used on electronic equipment to absorb transient energy entering the electronics through power, data, communication or ground lines. (See SPD)