impulse sparkover voltage. The highest value of voltage attained by an impulse of a designated wave shape and polarity applied across the terminals of an arrester prior to the flow of discharge current.
surge breakdown voltage. See impulse sparkover voltage.
impulse breakdown voltage. See impulse sparkover voltage.
sparkover. A disruptive discharge between electrodes of a measuring gap, voltage control gap, or protective device.
glow voltage. The voltage drop across an arrester during glow current flow. It is sometimes called the
glow mode voltage.
glow current. The current that flows after breakdown when the circuit impedance limits the follow current to a value less than the glow-to-arc transition current. It is sometimes called the
glow mode current.
follow current. The current from the connected power source that flows through an arrester during and following the passage of discharge current.
discharge current. The current that flows through an arrester when sparkover occurs.
dc holdover. In applications where dc voltage exists on a line, a holdover condition is one in which a surge-protective device continues to conduct after it is subjected to an impulse large enough to cause breakdown. Factors that affect the time required to recover from
the conducting state include the dc voltage and the dc current.
dc holdover voltage. The maximum dc voltage across the terminals of an arrester under which it may be expected to clear and to return to the high impedence state after the passage of a surge, under specified circuit conditions.
breakdown. The abrupt transition of the gap resistance from a practically infinite value to a relatively low value. In the case of a gap, this is sometimes referred to as sparkover or ignition.
breakdown voltage, dc. The minimum slowly rising dc voltage that causes breakdown or sparkover when applied to the terminals of an arrester.
breakdown voltage, ac. The minimum rms value of a sinusoidal voltage at frequencies between 15Hz and 62Hz that result in arrester sparkover.
arc current. The current that flows after breakdown when the circuit impedance allows a current that exceeds the glow-to-arc transition current. Sometimes called the
arc mode current.
glow-to-arc transition current. The current required for the arrester to pass from the glow mode into the arc mode.
arc voltage. The voltage drop across the arrester during arc current flow. Sometimes called
arc mode voltage.
discharge voltage. The voltage that appears across the terminals of an arrester during the passage of discharge current.
transition time. The time required for the voltage across a conducting gap to drop into the arc region after the gap initially begins to conduct.
current turnoff time. The time required for the arrester to restore itself to a non conducting state following a period of conduction. This applies only to a condition where the arrester is exposed to a continuous specified dc potential under a specific condition.