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APPENDIX
For current information see: 1206
Appendix
Glossary
machines and machine configurations operating together (machine
groups). The National Fire Protection Association is the
issuer of this important standard. NFPA 79 applies to all electrical and
electronic components in machinery with a maximum nominal voltage
of 600 V. NFPA 79 was revised in 2006. The aim of this revision was
to harmonise NFPA 79 with its European counterpart IEC/EN 60204.
Nominal voltage
The nominal voltage is the voltage to which the structure of the cable
relates in terms of its electrical properties. The nominal voltage is
expressed by specifying two AC voltages U0/U in V : U0 = Effective
value between an outer conductor and earth (non-insulating environ-
ment). U = Effective value between two outer conductors in a multi-core
cable or a system of single-core cables.
Norms
The German Federal Supreme Court gave the following statement on
engineering rules on 14.05.1998: Recognised engineering rules are
those that are recognised as correct by the theory and have demon-
strated their effectiveness in practice. By contrast, according to the
BGH DIN standards are only private engineering regulations with the
nature of recommendations, which do reflect the recognised engineering
rules but lag behind them or could actually be incorrect.
Numeral identification
See → Colour codes/Numerical identification
Numerical aperture
Sine of the maximum possible launch angle of a light waveguide.
NYM
These cables (standard cable for fixed installation) are designed for
installation above, on and below ground, in dry, damp and wet areas
and within walls and concrete, except for direct embedding in shaken,
vibrated or compressed concrete.
O
Ohmic resistance
The resistance per unit length records the losses in the metallic con-
ductors. The conductor dimensions, material and the temperature
determine the DC resistance Ro′. Because of skin effect, the conductor
resistance increases as the frequency rises. It also shows a linear
increase as the cable length increases.
ÖNORM-Format
Austrian format for invitations to tender.
Operating supplies
All objects needed when using electrical energy, e. g. switch, motors
and cables.
Operating temperature range
The range between the lower (lowest permissible temperature) and
upper (highest permissible temperature) limit temperature that may
be utilised by the operator.
Operating voltage
The actual voltage in a grid. This can fluctuate by up to 5%, caused by
the alternating use of consumers.
Opposite direction of lay
See → Stranding
Order length
The length of cable ordered by the customer.
OTDR
Measuring method for testing glass fibres for faults or transmission
quality. OTDR stands for Optical Time Domain Reflectometer.
Outdoor cable
Cables suitable for outdoor laying in the ground, in pipes, in the air,
in rivers and lakes, in mines, on ships, for interior spaces or the
most varied of industrial plants, etc. The design of the cable depends
on the electrical, thermal, mechanical and chemical laying and operat-
ing conditions.
Outer conductor
Conductors that connect current sources with consumables. For exam-
ple, C1, C2 or C3 in a three-phase system but not conductors come
from the midpoint or neutral point. The conductor is arranged concentri-
cally around the inner conductor of a coaxial pair.
Outer diameter
Diameter of the smallest circle that will enclose the surface of the
sheath.
Outer sheath
Enclosed cover for protection of the elements underneath.
Outer sheath
On the one hand, refers to the outer covering of a cable. On the other
hand, it is the entire optically transparent material in a light waveguide,
excluding the core.
Overcurrent
If the permitted ampacity is exceeded, this is referred to as overcurrent.
Overcurrent protection devices
Overcurrent protection devices break the current supply in case
of overcurrent. They include overcurrent protective switches and
safety fuses.
Oxygen index
Percentage oxygen content in the ambient air that is necessary to main-
tain combustion after removal of a flame. As the natural oxygen content
in the air is approx. 23%, materials with an oxygen index of greater than
24 are generally self-extinguishing when the flame is removed. This
term comes up primarily in connection with halogen free cables.
P
Pad
Non-conductive element made of insulating material (PVC) or textile,
used to fill up gaps in a strand group. Also known as a dummy core.
Pair
Two stranded → cores within a larger strand group (see → Element). The
inductive coupling of two parallel conductors is reduced by twisting the
two cores together as tightly as possible (→ twist length).
Panel mount base
Panel mount bases are designed for the feeding through of cables from
below. The panel mount base is mounted to control cabinet walls for
connecting control or power cables.