- When applied to a conductor means that the conductor has:
(i) A white or natural grey covering; or
(ii) A raised longitudinal ridge or ridges on the surface of the extruded
covering on certain flexible cords, either of which indicates that the conductor
is either a grounded conductor or a neutral; and
- When applied to other electrical
equipment means that the terminals to which grounded or neutral conductors
are to be connected have
been distinguished for identification by being tinned, nickel
plated, or otherwise suitably marked.
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
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.
- When applied to a room or compartment means that the room or
compartment is sufficiently remote from access or so placed or
guarded that unauthorized persons cannot inadvertently enter
the room or compartment.
- When applied to electrical equipment
means that the electrical equipment is covered by the structure
or finish of the building
in which it is installed or maintained, or is sufficiently
remote from access or so placed that unauthorized persons cannot
touch or interfere with the equipment.
Indicating Switch - see definition for Switch.
Industrial Establishment - A building or part
of a building (other than office or exhibit space) or a part of
the premises outside of the building where persons are employed
in manufacturing processes or in the handling of material, as distinguished
from dwellings, offices, and like occupancies.
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.
Inspection Department - An organization legally
authorized to enforce this Code and having jurisdiction over specified
Inspector - Any person duly appointed by the
inspection department for the purpose of enforcing Code.
Insulated - Means separated from other conducting
surfaces by a dielectric material or air space having a degree
of resistance to the passage of current and to disruptive discharge
sufficiently high for the condition of use.
Insulating as Applied to Non-Conducting Substances -
Means that they are capable of bringing about the condition defined
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
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.
Intermittent Duty - see definition for Duty.
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,
Intrinsically Safe - Means that any spark or
thermal effect that may occur in normal use, or under any conditions
of fault likely to occur in practice, is incapable of causing an
ignition of the prescribed flammable gas, vapour, or dust.
Isolating Switch - see definition for Switch.
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