BURNDY
®
Canada: 1-800-387-6487 www.burndy.com US: 1-800-346-4175
Reference
Introduction
Basic Connection Principles
Hardware Data
DURIUM™ Steel/Aluminum Tightening
Torques
DURIUM™ Hex Bolts Data
UL Tightening Torque UL486
Recommended Clamping on Bolted
Connectors
Cable Data (Tables)
Copper Cable
Copper Tube
Solid Copper Wire
Compact Stranded Copper Cable
Stranded Copper Cable
Flexible Copper Stranded Cable
Aluminum and ACSR Cable
Aluminum Tube
Aluminum 1350 Cable Bare -
Classes AA and A
Aluminum 1350 Cable Bare - Class B
ACSR Cable
High Strength ACSR Cable
Compact Aluminum 1350 Cable
Aluminimum Alloy 5005 Cable
Aluminum 6201 Cable
Aluminum Alloy 8000 Series “O”
Temper Cable
Compact ACSR Cable
ACSR/TW Cable (Trap Wire)
AAC/TW Cable
(All Aluminum Trap Wire)
ACAR Cable
SSAC Cable
Steel Conductors
Copperweld Cable
Copperweld - Copper Cable
Galvanized Steel Cable
Aluminum Coated Steel Cable
TABLE OF CONTENTS
O-2 - O-5
O-6
O-6
O-7, O-8
O-9
O-10
O-11
O-11
O-12, O-13
O-14, O-15
O-16
O-17
O-18
O-19
O-20
O-21
O-22
O-22
O-23, O-24
O-25
O-25, O-26
O-26
O-27
O-27, O-28
O-29
O-29, O-30
O-31
O-32
O-32
O-33, O-34
O-35
O-36, O-37
O-38 - O-48
O-49
O-49
O-50
O-51
O-52 - O-99
O-100 - O-101
Terminal Stud Size Chart
AWG vs. Metric Wire Sizes
Inches - Millimeters
Conversion Chart
BURNDY Conductor Numbering
System
Present Installation Tool Index
Color Coding for Overhead
Conectors
Color Coding for AL/CU
Connectors
Color Coding for Copper
Lugs and Splices
Product/Trade Name Index
Alpha-Numeric Index
Terms and Conditions
O-1
BURNDY
®
US: 1-800-346-4175 www.burndy.com Canada: 1-800-387-6487
Reference
Introduction - Basic Electrical Connection Principles:
Basic Factors:
The basic factors which inuence the design and
performance of pressure wire connections are as
follows:
1. Creep
2. Surface Oxide
3. Corrosion
A fourth factor, known as thermal effects, is also a
consideration, but due to the technical nature and
length of this topic, it will not be discussed in this
publication.
At the outset it should be pointed out that these
factors give rise to much more difcult problems
in connections involving aluminum conductors
than those encountered in copper to copper
connections.
Creep (Cold Flow)
Creep is the cold ow of the metal under pressure
and it continues until the pressure reduces to a
value at which any further creep is negligible.
Creep properties depend on the particular metal
or alloy and on its hardness; alloys having less
creep than pure metals, and harder metals
have less creep than soft metals. In a typical
connection, the conductors are generally of pure
metal and often of soft temper and therefore,
subject to considerable creep. In addition, the
condition is further exaggerated when aluminum
is the conductor as compared to copper, since its
creep rate is many times that of copper.
Effect of Creep: Figure 2 shows typical curves
of total contact resistance plotted against total
contact force. Curve A shows how the contact
resistance continually decreases with increasing
contact force. When the full contact force F1 is
reached, the contact resistance reaches the low
value of R1. In general, the full tightening force on
a connector greatly exceeds the maximum force
for which there is no appreciable creep. Therefore,
the force will gradually settle down to a value after
which there will be no further signicant creep.
Fortunately, however, the resistance does not
climb back up along curve A, the tightening curve,
but instead it follows a new curve B, the relaxing
curve, along which the resistance changes very
little until the force relaxes to a value such as F2.
Admittedly, the point of “no appreciable creep”
is difcult to dene. For pure metals, especially
in the soft state, there is always some creep,
even at very low pressures at room temperature.
However, we do know that the pressure required
to produce the same creep rate is several times
greater for copper than for aluminum. Thus, to
permit the same contact force F2 for aluminum
and copper, the contact area A required for
aluminum can be expected to be considerably
greater than that required for copper. This
explains why the contact areas for connectors for
aluminum must be considerably greater than for
copper and why many light duty connectors for
copper are entirely inadequate for aluminum, even
when specially plated and when recommended
compounds are used on the contact surfaces.
Relaxation: Relaxation of pressure due to creep,
or for any other reason, would be a much more
difcult factor in a pressure connection were it not
for the relationship of contact pressure to contact
resistance on the relaxation curve as shown
in Figure 2. It is frequently observed that some
time after the bolts of a clamp type connector
are tightened, the bolt tensions are relaxed
appreciably. The question arises as to whether it
is necessary to retighten the bolts to the original
torque value. In a properly designed connector,
retightening is unnecessary since the contact
resistance should increase very little due to the
relaxation of pressure, as shown by the relaxation
curve of Figure 2.
This fact is largely responsible for the successful
operation of a compression connector. The
application of the compression tool applies very
high pressure, establishing very low contact
resistance. The removal of the compression
tool releases a very large proportion of this
pressure, and creep further relaxes this pressure.
Fortunately, the contact resistance increases very
little due to this pressure relaxation.
Contact Force: The previous analysis shows
that the total contact force largely determines the
contact resistance. Thus, to achieve the desired
low value of contact resistance, the proper size
and number of bolts in a clamp type connector
must be supplied, and the compression tool
must apply the proper force to a compression
connector. In addition, the connector must be
designed with sufcient structural strength,
contact area, and resilience, to assure that the
contact force cannot relax beyond the point where
contact resistance begins to rise appreciably, as
shown in Figure 2.
Surface Oxide
The contact of pure metallic surfaces cannot
be assured in practical connections. Surface
contamination must be expected, especially
surface oxidation. These surface lms are
insulators as far as contact resistance is
concerned, and they must be broken to achieve
metal to metal contact to make an adequate
electrical connection. The difculty of breaking
the lm depends on the nature of the lm, its
thickness, and the metal on which it is formed.
Copper oxide is generally broken down by
reasonably low values of contact pressure. Unless
the copper is badly oxidized, good contact can be
obtained with very little or no cleaning.
Silver oxide is even more easily broken down
by the contact pressure; and since silver oxide
forms less readily at elevated temperatures, silver
contact surfaces are preferred over copper when
used for high temperatures. For this reason,
it is considered good practice to silver plate
copper contact surfaces that must operate at
temperatures over 200˚ C.
On the other hand, aluminum oxide is a hard,
tenacious, high resistance lm that forms very
rapidly on the surface of aluminum exposed to air.
In fact, it is the toughness of this lm that gives
aluminum its good corrosion resistance. The
oxide lm that forms after more than a few hours
is too thick and tough to permit a low resistance
contact without cleaning. The aluminum oxide
lm is transparent so that even the bright and
clean appearance of an aluminum connector is no
assurance that the low contact resistance can be
attained without cleaning.
In addition to the necessity for cleaning the oxide
from aluminum, the surface should be covered
with a good connector compound to prevent
the oxide from reforming. Common practice
is to clean the surface with a wire brush or
emery cloth. The compound should be applied
immediately after cleaning, or the compound
should be put on rst and the surface scraped
through the compound. Present practice is to
scratch brush dry and to apply the compound
immediately thereafter. This allows a more
thorough job of cleaning the conductor.
Contact Compounds: Petrolatum or No-
Oxid are good contact surface compounds for
aluminum, but BURNDY
®
PENETROX™ A, a
petroleum type compound containing zinc dust,
has the additional advantage of assisting in the
Figure 2
O-2