Surge Protection Device (SPD) Specification Glossary

Maximum Operating Voltage:
Maximum allowable continuous sinusoidal voltage (RMS) at 50-60hz. If suppressor is exposed to a continuous voltage higher than RMS voltage stated in specification, the suppressor may suffer damage.

Measured Limiting (Let-Through) Voltage:
The maximum magnitude of voltage that is measured across the terminals of the SPD during the application of impulses of specified waveshape and amplitude.

Input Power Frequency:
Frequency range in which the suppressor operates without causing damage to suppressor or equipment, or interference with the power signal. Applicable to AC circuits.

Peak Surge Current:
Maximum current allowed for a single 8X20 microsecond waveform,µs impulse waveform with continuous voltage applied. The higher the number, the stronger the unit.

Filter Frequency Range:
The range of frequency in which a filter operates. This is usually dictated by the 3db points on the low and high ends of the frequency scale.

Frequency (Noise) Attenuation:
The range of attenuation for a given frequency range. A larger negative number indicates a greater attenuation.

Energy:
Maximum allowable energy for a single impulse on a 8x20 US current waveform. Indicative of the maximum amount of energy that the suppressor can dissipate. This energy is transitory and is dependent upon three (3) variables: 1. voltage, 2. current, and 3. time. Any variation of the three will effect this figure.

Response Time:
The time in which a suppression device responds to a transient.

Protection Modes:
Protection mode indicates suppressor's ability to protect different paths of transient activity. Normal mode = line to ground and/or neutral to ground.

Physical Dimensions:
The length, width and height or depth of the suppression device. When considering space constraints in any application, this specification affords quick determination of acceptability.

Dynamic Measured Limiting Voltage Test:
Test conducted with normal operating voltage applied. (formerly known as "let-through" voltage)

Static Measured Limiting Voltage Test:
Test conducted with no normal operating voltage applied; eg: neutral-to-ground, which has no voltage normally applied. formerly known as "let-through" voltage)

Positive or Negative Polarity:
Indicates direction in which the surge occurs.

Transient Phase Angle:
The point on the sine wave at which a transient occurs. IEEE states that transients can occur at any phase angle. It is important to be able to see suppression device response to transients at varying phase angles.

Peak Transient Voltage:
The peak transient voltage which is applied to unit under test according to ANSI/IEEE C62.41 1991, section 4.1: ". . this 6 kV level, therefore, can be selected as a typical cutoff for the occurrence of surges in indoor power systems."

Surge or Transient Amperage:
IEEE has developed wave form guidelines for testing. In this guideline, discharge currents (surge currents) are given as 200A, 5OOA, and 3000A. These values, when combined with the appropriate transient waveshape represent possible transient activity according to ANSI/IEEE C62.4 1 - 1991.

Lead Length:
The length of leads, whether integral to the unit or added to effect field connection, extending from the suppression device enclosure on a hard wire panel unit. This is an important factor in testing as specifications should reflect actual installation application.

- Delta Configuration.
Y - Wye Configuration.
W + G - Description of connection for application, i.e. 2W + G means 2 wires + ground.

Weight:
Weight of suppression device. Useful in determining application and installation requirements.

Listings:
Statement of independent laboratory testing, for safety and/or performance.