| Ampere
| Unit of current. |
| ANSI
| American National Standards Institute. |
| Basic Insulation Level (BIL)
| The voltage that an insulation is able to withstand. This is measured using a 1.2 x 50 microsecond wave. |
| Clamping Device
| A component which is activated and deactivated by predetermined voltages. |
| Clamping Voltage
| See “Let-Through Voltage.” |
| Conductor
| A material that permits a very free exchange/movement of electrons from one atom to another. |
| Current
| The flow of electrons in the same direction from atom to atom. |
| Delta
| A motor connection arrangement where each winding is wired end to end to form a completely closed loop circuit. |
| Frequency
| The number of cycles in one second of alternating current. Expressed in hertz (Hz). For example, 60 Hz is 60 cycles in one second. |
| Grounding Path
| The path in an electrical system that electrical power will follow to ground. |
| Harmonics
| Multiples of the AC power fundamental frequency. When added to the fundamental frequency, a distorted waveform is produced. |
| IEEE
| Institute of Electrical and Electronics Engineers. |
| Impedance
| The apparent opposition of current flow with application of voltage. |
| Let-Through Voltage
| The portion of a transient which is not suppressed by an SPD and is let through to the load. |
| Maximum Continuous Operating Voltage (MCOV)
| The turn on voltage when the MOV starts to shunt current to ground. |
| Metal Oxide Varistor (MOV)
| A solid-state surge suppression component that can handle large amounts of current and react within nanoseconds. |
| NEC
| National Electrical Code. |
| NFPA
| National Fire Protection Association. |
| NLSI
| National Lightning Safety Institute. |
| Noise Distortion
| An unwanted disturbance superimposed on a useful signal. |
| Overvoltage
| A swell lasting more than one minute. |
| Panelboard
| A wall-mounted electrical power distribution device for use in commercial and industrial applications. It provides circuit control and overcurrent protection for light, heat or power circuits. NEC defines it as a single panel or group of panel units designed for assembly in the form of a single panel; including buses, automatic overcurrent devices, and equipped with or without switches for the control of light, heat, or power circuits; designed to be placed in a cabinet or cutout box placed in or against a wall or partition and accessible only from the front. |
| Power Quality
| A general term referring to many different type of disturbances and distortions to a power signal. IEEE defines it as “The concept of powering and grounding sensitive equipment in a manner that is suitable to the operation of that equipment.” |
| Radio Frequency Interference (RFI)
| A type of system noise caused by communication system components. |
| Resistance
| The restriction to the flow of electrons. |
| RMS
| Root Mean Square current. Also referred to as effective current. It is the square root of the average of all the instantaneous currents (current at any point on a sine wave), squared. |
| Sag
| A decrease in RMS voltage lasting from half a cycle to a minute. |
| Selenium Cell
| An early surge suppression device made up of metallic rectifiers. This device was replaced by the MOV in the 1980s. |
| Service Entrance
| The point at which electrical power enters a building. |
| Shunt
| A low-resistance parallel circuit used to divert current. |
| Silicon Avalanche Diode (SAD)
| A solid-state surge suppression component which is extremely fast, but lacks the ability to handle heavy current. It is not commonly used in AC applications. |
| Spike
| See “Surge.” |
| Standards
| Guidelines and regulations for the manufacturing of electrical equipment. |
| Surge
| A single, non-repeating voltage distortion of less than 0.5 cycles in duration. (Also called “Spike,” “Transient,” or “Voltage Impulse.” |
| Surge Current Capacity
| The maximum 8/20 us surge current pulse the SPD device is capable of surviving on a single impulse basis, without suffering either performance or degradation of more than 10 percent deviation of clamping voltage. |
| Surge Protective Device (SPD)
| A device used to protect electronic equipment from harmful variations in power quality. |
| Swell
| An increase in RMS voltage lasting from half a cycle to a minute. |
| Switchboard
| A floor-standing electrical power distribution device for use in commercial and industrial applications. It divides large blocks of electrical current into smaller blocks of current used by electrical equipment. NEC defines it as a large single panel, frame, or assembly of panels on which are mounted, on the face or back, or both, switches overcurrent and other protective devices, buses and usually instruments. |
| Transient
| See “Surge.” |
| Transient Voltage Surge Suppressor (TVSS)
| See “Surge Protective Device.” |
| Transformer
| A device used to raise (step up) or lower (step down) a voltage level. |
| UL
| Underwriters Laboratories. |
| Uninterruptable Power Supply (UPS)
| A system designed to automatically provide power, without delay or transients, during any period when the normal power supply is incapable of performing acceptably. |
| Voltage
| The force applied to a conductor to free electrons, causing electrical current to flow. |
| Voltage Impulse
| See “Surge.” |
| Watt
| The basic unit of power, indicating the amount of work accomplished when one volt causes one ampere to pass through a circuit. |
| Wye
| A motor connection arrangement where one end of each of the three-phases is connected to the other phases internally. The remaining end of each phase is then brought out externally. |
