IEC 60099-6-2019 pdf free.Surge arresters—Surge arresters containing both series and parallel gapped structures—System voltage of 52 kV and less.
housing external insulating part of an arrester，which provides the necessary creepage distance andprotects the internal parts from the environment.
Note 1 to entry: A housing may consist of several parts providing mechanical strength and protection against theenvironment.
impulse unidirectional wave of voltage or current which，without appreciable oscillations, rises rapidlyto a maximum value and falls,usually less rapidly, to zero with small, if any, excursions ofopposite polarity,with defining parameters being polarity, peak value,front time and time tohalf-value.
insulating base a short insulator (or set of insulators) on which the arrester is mounted to provide a means ofconnecting a current monitoring device between the base of the arrester and earth.
internal grading components of an internally gapped arrester grading impedances,connected in parallel with the internal gap(s), to control the voltageacross the gap section.
internal parts Mo resistor with supporting structure and internal grading system, if equipped.
lightning current impulse 8/20 current impulse with limits on the adjustment of equipment such that the measuredvalues are from 7 us to 9 us for the virtual front time and from 18 us to 22 us for the time tohalf-value.
lightning impulse discharge an approximately sine half-wave current impulse having a time duration within 200 us to 230us during which the instantaneous value of the impulse current is greater than 5 % of its peakvalue.
lightning impulse protection levelLIPL or Upl the maximum residual voltage of the arrester for the nominal discharge current.
long-duration current impulse rectangular current impulse which rises rapidly to maximum value，remains substantiallyconstant for a specified period and then falls rapidly to zero，with defining parameters beingpolarity,peak value,virtual duration of the peak and virtual total duration.
mean breaking loadMBL the average breaking load for porcelain or cast resin-housed arresters determined from tests.
mechanical unit portion of an arrester in which the MO resistors within the unit are mechanically restrainedfrom moving in an axial direction.
Note 1 to entry: An arrester may contain more than one mechanical units within an electrical unit (see Figure 5)Note 2 to entry: A mechanical unit may have more than one electrical unit (see Figure 5).
mounting bracket means by which a distribution class arrester is physically attached to a pole or other structure.IEC 60099-6 pdf download.