IEC
- International Electrotechnical Commission.
IEEE - Institute of
Electrical and Electronics Engineers.
Impedance
- The obstruction to the flow of current in an ac circuit. The
transformer impedance is made up of the internal resistance and
reactance which creates a voltage drop caused by current flowing
in the windings. Impedance losses are a combination of heat (I2R) losses in the conductor, eddy
current loss, and losses in other parts of the transformer caused
by stray currents.
Impulse
- A current surge.
Impulse
Tests - Tests which ensure a satisfactory level of insulation
and the ability of a device to withstand, within certain limits,
overvoltage surges (such as lightning strikes) that may occur in
service.
Inrush
Current - The initial momentary surge current demand before a
load resistance of impedance increases to its normal operating
value.
Inrush
Restraint - A restraint feature that can make the fault
indicator inoperable to inrush currents.
Insulation
- A material having a high resistance to the flow of electric
current; insulation over underground conductor is made of either
EPR or XLPE material.
Insulation
Coordination - The review of the protective level of the
arrester and the insulation level of the equipment to be
protected to ensure that the arrester is adequately protecting
the equipment.
Insulation
System - A balanced combination of materials (kraft paper,
oil, porcelain, etc.) which provides dielectric strength to a
device.
Insulator
- Any material which does not allow electrons to flow through it.
Intermediate
Class Arrester - A classification of 3-120 kV rated arresters
with higher energy handling capability and durability compared to
a Distribution Class Arrester. In addition, pressure relief
capability is required.
Interrupter
- An element designed to interrupt specific currents under
specified conditions.
Interrupter
Switch - An air switch, equipped with an interrupter, for
making and/or breaking specified currents. NOTE: The nature of
the current made or broken, and/or both, may be indicated by
suitable prefix; that is, load interrupter switch, fault
interrupter switch, capacitor current interrupter switch, etc.
Isolation
Link - A small metal link used in series with a Bay-O-Net
link or MagneX interrupter. During transformer failure, the
isolation link will melt so the opened primary circuit of a
faulted transformer cannot be re-energized by the line crew. An
isolation link has melt characteristics, but no fault clearing
capabilities.
Isolator™
- CPS's trademark for the arrester disconnector.