TANZANIA BUREAU OF STANDARDS
DRAFT TANZANIA STANDARD
EEDC 3(3700) P3
Aluminium conductor, galvanized steel reinforced for overhead power transmission Specification.
(Draft for comments only)
0. FOREWORD
Overhead lines are the commonly means of transmitting and distributing power from generating stations
which are normally far from utilization point. Aluminium conductors provides comparable cheap
alternative for transmission than many other available conductors and hence the most used conductor
for transmission and distribution of power.
This draft Tanzania Standard is intended mainly to cover the technical requirements relating to
aluminium conductors steel-reinforced (ACSR) used for overhead transmission purposes.
This draft Tanzania Standard specifies requirements for aluminium and steel materials used to
manufacture ACSR conductor. It also specifies requirements for construction, packing and marking
sampling, inspection and testing.
1. SCOPE
This draft Tanzania Standard specifies the requirements for uninsulated stranded hard-drawn
aluminium conductors, steel-reinforced (ACSR) for overhead power transmission purposes.
2. REFERENCE
The following referenced document is indispensable for application of this draft standard.
TSZ 8:1979 – Specification for reels and drums for bare wires
3. TERMINOLOGY
For the purposes of this standard, the following definitions shall apply:
3.1 Aluminium conductor steel-reinforced
A conductor consisting of seven or more aluminium and galvanized steel wires built up in concentric
layers. The centre wire or wires are of galvanized steel and the outer layer or layers of aluminium.
3.2 Diameter
The mean of two measurements at right angles taken at the same cross-section.
3.3 Direction of lay
The lateral direction of inclination to the axis, either right hand or left hand, of the receding helix formed
by a wire of a stranded conductor.
NOTE - With right-hand lay, the wires conform to the direction of the central part of the letter Z when the conductor is held
vertically. With left-hand lay, the wires conform to the direction of the central part of the letter S when the conductor is held
vertically.
1
3.4 Defective
A reel or drum of stranded conductor that fails in one or more respects to comply with the relevant
requirements of the specification.
3.5 Lay ratio
The ratio of the axial length of a complete turn of the helix formed by an individual wire in a stranded
conductor to the external diameter of the helix.
3.6 Lot
Not more than 3 000 reels or drums of stranded aluminium conductor, steel reinforced, of the same
reference area, from one manufacturer, submitted at any one time for inspection and testing.
3.7 Reference area
The cross-sectional area to be used for designation and purchasing purposes.
3.8 Standard diameter of wire
The wire diameter on which the requirements for the mass and resistance per unit length
and the breaking strength of the wire are based.
3.9 Wire
Aluminium or steel of uniform diameter and circular in cross-section produced by drawing.
4. MATERIAL CHARACTERISTICS
4.1 Aluminium
The conductors shall be of aluminium. Aluminium from which the wires are drawn shall be in the H9
condition and shall comply with the requirements given in table 1 and its volume resistivity, density,
coefficient of linear expansion, and coefficient of variation of resistance with temperature shall conform
clause 4.1.1 to 4.1.4
4.1.1 Volume resistivity
The resistivity of aluminum wire depends upon its purity and its physical condition. For this standard
maximum permitted value is 2.8264 micro-ohm. cm at 20°C and this value has been used as the
standard resistivity for the purposes of calculation.
4.1.2 Density
3
At a temperature of 20°C the density of hard-drawn aluminum wire is to be taken as 2.703 g/cm
4.1.3 Coefficient of linear expansion
The coefficient of linear expansion of hard-drawn aluminum is to be taken as 23.0 x
is applicable over the range of temperatures from 0°C to 30°C
/°C. This value
4.1.4 Coefficient of variation of resistance with temperature
The coefficient of variation of the resistance with temperature, when measured between two potential
points rigidly fixed to the wire, the metal being allowed to expand freely: 0.00403 per °C;
2
TABLE 1 - Chemical composition of aluminium EN AW-1350 (99.5)
Content %
Element
minimum
Aluminium
99.5
*
Maximum.
–
Copper
–
0.05
Silicon
–
0.10
Iron
–
0.40
Zinc
–
0.05
Manganese
–
0.01
Chromium
–
0.01
–
0.03
Gallium
Impurities max.
+
*
The aluminium content of unalloyed aluminium not made by a refining process is
the difference between 100.00 % and the sum of all other metallic elements
present in amounts of 0.010 % or more each, expressed to the second decimal
place before determining the sum.
+
Except that in aluminums of designation other than EN AW-1350 other
impurities shall be permitted provided that the content of an individual impurity
does not exceed 0.03 %. In addition, in none of the aluminium shall any impurity
that is not specifically limited be present in an amount that is generally accepted as
having an adverse effect on the product.
4.2 STEEL WIRE FOR REINFORCING
The steel wires for reinforcing shall be galvanized. The galvanized steel wires shall have density and
coefficient of linear expansion as given in 4.2.1 and 4.2.2 respectively, and the mechanical properties as
given in table 4, appropriate to the standard diameter of the wire.
The quality of the galvanizing shall be such that:
1) the mass of the zinc coating, determined in accordance with G.1, shall conform to the
appropriate value given in table 2,
2) the wire, when tested in accordance with G.2, shall withstand the appropriate number of
dips in the copper sulphate solution given in table 2 without showing adherent red copper
deposits on the base metal, and
3) the coating, when tested in accordance with G.3, shall show no sign of flaking or cracking.
4.2.1 Density
3
At a temperature of 20°C the density of galvanized steel wire is to be taken as 7.85 g/cm .
4.2.2 Coefficient of linear expansion
In order to obtain uniformity in calculations, the coefficient of linear expansion of galvanized steel wires
used for the cores of aluminum conductors, steel-reinforced is to be taken as 11.5 x
/°C.
3
TABLE 2 - Minimum mass of zinc coating and number and duration of dips.
Standard diameter
of wire
Mass of zinc
2
coating, g/m
Number of dips in copper
sulphate solution at 20 ± 2 °C
mm
1.57
(minimum)
1-minute dips
½ -minute dips
195
2
-
2.36
2.59
2.79
230
245
245
2
2
2
1
1
1
3.00
3.18
255
255
3
3
-
3.35
3.66
265
265
3
3
-
4.72
280
3
1
5. DIMENSIONS AND CONSTRUCTION
5.1 Wire
The wires that form a stranded conductor shall, before stranding, comply with the following
requirements:
a) Diameter. The diameter of a single wire, measured in accordance with A.1.1, shall
i) in the case of aluminium wire, be within the appropriate limits given in table 3, and
ii) in the case of galvanized steel wire (measured over the zinc coating and subject to a
tolerance of ± 2 %) conform to the appropriate value given in table 4
b) Freedom from defects. The wires shall be smooth, uniform in quality, free from spills, splits, and
other defects, and any departure from circularity of the cross-section shall not exceed 1 % of the
mean diameter.
c) Physical properties. Aluminium wire shall be hard-drawn, and aluminium and galvanized steel
wire shall, except as allowed in terms of 5.2.1 and 5.2.2, comply with the relevant of the
following requirements:
i)
Resistance. The resistance of aluminium wire, determined in accordance with Annex
B, shall not exceed the appropriate maximum given in table 3.
ii)
Breaking strength. The breaking strength, determined in accordance with C.1, shall be
at least equal to the appropriate minimum given in table 3 for aluminium wire and the
appropriate minimum given in table 4 for galvanized steel wire.
Note – Table 3 and 4 gives the breaking strength based on standard diameter, therefore the breaking
strength so determined by Annex C shall not be below the minimum breaking strength for diameter range
within which the measured diameter lie.
iii) Elongation at break or ductility when twisted of galvanized steel wire. Galvanized steel
wire shall comply with one of the following requirements:
4
a) the elongation at break, determined in accordance with C.3.1, shall be at least 4
% or, alternatively
b) when tested in accordance with E.1, the wire shall withstand at least 18 twists
in a gauge length of 100 times its standard diameter.
iv)
Ductility when lapped. Ductility shall be such that when the wire is tested in accordance
with Annex D, it shows no signs of cracks (when examined by unaided normal vision) or of
breaking in the case of galvanized steel wire.
v)
Load at 1 % elongation. The load at 1 % elongation for galvanized steel wire, determined
in accordance with Annex F shall be at least equal to the appropriate minimum given in
table 4.
TABLE 3 - Hard-drawn circular aluminium wires for aluminium,
steel-reinforced, overhead conductors
Nominal
mass
1
per km
Wire diameter
mm
Standard Maximum Minimum
1
2
3
kg
Resistance per km at
20 °C
Breaking
1
strength
Ohms
3
2
Standard Maximum N. min.
2.36
2.59
2.384
2.616
2.336
2.564
11.82
14.24
6.461
5.365
6.600
5.474
770
906
2.79
3.00
3.18
2.818
3.030
3.212
2.762
2.970
3.148
16.53
19.11
21.47
4.623
3.999
3.559
4.717
4.080
3.631
1030
1190
1310
3.35
3.66
3.95
4.72
3.384
3.697
3.990
4.767
3.317
3.623
3.911
4.673
23.82
28.44
33.12
47.30
3.207
2.686
2.306
1.615
3.271
2.742
2.353
1.648
1450
1750
2035
2780
Based on standard diameters.
These resistances are based on standard diameters and a volume
Resistivity of 2.826 4 micro-ohm. cm at 20 °C.
These resistances are based on minimum diameters.
5
TABLE 4 - Mechanical properties of circular galvanized steel wires for aluminium,
steel-reinforced, overhead conductors
Standard diameter
of wire
mm
Nominal mass per
km
Load at 1 % elongation Breaking strength for
for standard wires
standard diameter wire
kg
kN, min.
kN, min.
1.57
15.10
2.28
2.55
2.36
2.59
34.12
41.09
4.99
6.01
5.78
6.95
2.79
3.00
3.18
47.69
55.13
61.95
6.97
8.06
8.74
8.06
9.30
10.47
3.35
3.66
4.72
68.75
82.06
136.48
9.70
12.00
19.86
11.62
13.87
23.07
5.2 Joints in wire strands.
5.2.1 Aluminium wires
In aluminium conductors, steel-reinforced containing any number of aluminium wires, joints in individual
aluminium wires are permitted in addition to those made in the base rod or wire before final drawing
provided that there are no more than four joints per 1000 m and, no two such joints shall be less than 15
m apart in the complete stranded conductor. Such joints shall be made by resistance or cold-pressure
butt-welding. Joints shall, subsequent to welding, be annealed over a distance of at least 200 mm on
each side of the joint. The joint shall not increase diameter of the stranded conductor. The section of
wire containing a joint shall be exempt from the requirements given in table 3.
5.2.2 Galvanized steel wires
There shall be no joints, except those made in the base rod or wire before final drawing, in steel wires
forming the core of an aluminium conductor, steel-reinforced, unless the core consists of seven or more
galvanized steel wires. In the latter case joints in individual wire are permitted, in addition to those made
in the base rod or wire before final drawing, but no two such joints shall be less than 15 m apart in the
complete steel core. Joints in the wires shall be made by resistance butt-welding and shall be protected
against corrosion by re-galvanizing. The joint shall not increase diameter of the stranded conductor. The
section of wire containing a joint shall be exempt from the requirements given in table 4.
5.3 Stranding
5.3.1 General
The number and diameter of the wires in a steel reinforced aluminium conductor shall conform to the
values given in table 7 appropriate to the reference area specified by the purchaser. The wires in each
layer shall be evenly and closely stranded and, when so specified by the purchaser, a suitable corrosion
inhibitor shall be applied, evenly throughout the length of the conductor, to the centre wire and to the
wires in specified layers. The stranding shall be such that:
a) the overall diameter of the stranded conductor complies with the requirements of 5.4.1.
6
b) the diameter, determined in accordance with A.1.2 of individual wires taken from the stranded
conductor does not differ by more than 1 % from the appropriate values given in table 3 and table
4.
c) the mean and the minimum breaking strengths, determined in accordance with C.2 of
individual wires taken from the stranded conductor are at least 95 % and 90 % respectively of
the appropriate minimum value given in table 3 or table 4, as relevant
d) the elongation at break, determined in accordance with C.3.2, of individual galvanized steel wires
taken from the stranded conductor, is at least 3.5 %; and
e) when tested in accordance with E.2, individual galvanized steel wires taken from the stranded
conductor will withstand at least 16 complete twists on a length equal to 100 times the diameter of
the wire before breaking occurs..
Note – Stranding / configuration other than those specified in table 7 are allowed subject to purchaser order, such
configuration shall conform to relevant requirements of this draft standard
5.3.2
In all constructions, successive layers of a stranded conductor shall have opposite directions of
lay, the outermost layer being right-handed. The wires in each layer shall be evenly and closely
stranded.
5.3.3
The lay ratio of the different layers shall be within the limits given in table 5. In aluminium
stranded conductors having multiple layers of wires, the lay ratio of any layer shall not be
greater than the lay ratio of the layer immediately beneath it.
5.3.4
Steel wires shall be formed during stranding so that they remain inert when the conductor is cut.
TABLE 5 — Lay ratios for aluminium conductors, steel reinforced
Lay ratios for
steel cores
Number of wires in
conductor
Aluminium
6
6
30
54
Steel
1
7
7
7
Lay ratios for aluminium layers
6-wire layer
6-wire layer 12-wire layer 18-wire layer 24-wire layer
Max.
Max.
Min.
Max.
Min.
Max.
Min.
Max.
14
14
–
–
10
10
–
–
–
–
16
17
–
–
10
10
–
–
14
16
–
–
10
10
–
–
–
14
–
28
28
28
Min.
–
13
13
13
Min.
–
–
–
10
5.4 Completed conductor
The completed conductor shall be free from dirt, grit, excessive amounts of drawing oil and other foreign
deposits having the properties given in table 7:
5.4.1 Overall diameter
The overall diameter of a conductor, determined in accordance with A.2 shall not exceed the appropriate
maximum given in table 7.
7
5.4.2
Resistance
The overall resistance of a conductor, determined in accordance with Annex B using a single aluminium
wire to be used in the constructing the stranded conductor and multiplied by the appropriate constant
given in table 6 shall not exceed the appropriate maximum value given in table 7.
5.4.3 Breaking strength
The overall breaking strength of a conductor, determined in accordance with H.4 of Annex H shall not
exceed the appropriate minimum value given in table 7.
TABLE 6 — Stranding constants for aluminium,
steel reinforced, overhead conductors
Stranding constants
Number of wires in
conductor
Mass
Aluminium
Steel
6
6
30
54
1
7
7
7
Aluminium
6.091
6.091
30.67
55.23
Electrical
resistance
Steel
1.000
7.032
7.032
7.032
0.1692
0.1692
0.03408
0.01894
TABLE 7 — Hard-drawn aluminium, steel reinforced, overhead conductors
Stranding and wire
diameter
Calculated
breaking
load
Calculated d.c
resistance at
20°C per km
aluminium only
kN, Min.
Ω, Max.
Aluminium
Steel
Approximate
overall
diameter
mm
mm
mm, Max.
mm
25
30
40
6/2.36
6/2.59
6/3.00
1/2.36
1/2.59
1/3.00
7.08
7.77
9.00
30.62
36.88
49.48
106
128
172
9.61
11.4
15.2
1.093
0.9077
0.6766
50
60
100
6/3.35
6/3.66
6/4.72
1/3.35
1/3.66
7/1.57
10.05
11.09
14.15
61.70
73.65
118.5
214
255
394
18.4
22.50
32.7
0.5426
0.4639
0.2733
150
175
30/2.59
30/2.79
7/2.59
7/2.79
18.13
19.53
194.9
226.2
726
842
69.2
79.8
0.1828
0.1576
200
260
400
30/3.00
30/3.35
54/3.18
7/3.00
7/3.35
7/3.18
21.00
23.69
28.62
261.5
326.1
484.5
974
1214
1621
92.2
111.4
131.9
0.1363
0.1115
0.06740
Reference
area
mm
2
Total
sectional
area
2
Approximate
mass per km,
kg
NOTES - The sectional area is the sum of the cross-sectional areas of the relevant individual wires.
8
5.5 Lengths and variations in lengths
Unless otherwise agreed between purchaser and manufacturer conductors shall be supplied in the
manufacturer's usual production lengths and with a permitted variation of five per cent in the length of
any one conductor lengths. Additionally, it shall be permissible to supply not more than five per cent of
the length on any one order in random length provided that no random length is shorter than one-third of
the appropriate production length. The actual length of the conductor on a drum or reel shall not differ
from the nominal length by more than 1 %.
6. PACKING AND MARKING
6.1 Unless otherwise specified by the purchaser the conductor shall be wound in reels or drums
conforming to TZS 8 legibly and indelibly marked with the following:
a) Trade name, if any,
a) Name of manufacturer,
b) Size and type of conductor,
c) Length of conductor,
d) Country of origin,
e) Gross mass in kg, and
f) Year of manufacture.
Unless otherwise acceptable, each continuous length of a stranded conductor shall be packed
individually. The conductor may also be marked with TBS Certification Mark.
NOTE— The TBS Certification Mark may be used by manufacturers only under license from TBS.
7. SAMPLING, INSPECTION AND TESTING.
7.1 Sampling
The following sampling procedure shall be applied in determining whether a lot complies with the
appropriate requirements of the specification. The samples so drawn shall be deemed to represent the
lot for the respective properties.
7.1.1 Sample for inspection
From the lot take at random a sample of the size given in table 8
7.1.2 Sample for testing
After inspection (see 7.2) of the sample taken in accordance with 7.1.1 cut off and discard the first
300 mm length of the outer end of the wire or conductor on each reel or drum and then cut the length
required for the test pieces.
Table 8 — Sample sizes for stranded conductors
Lot size, coils,
reels or drums
1 – 30
31 – 500
501 – 800
801 – 1 300
1 301 – 3 000
Sample size, coils
reels or drums
Number of
defectives
All
30
0
40
55
2
2
75
3
1
Note - This section applies to the sampling for inspection and testing before acceptance or rejection of single lots
(consignments) in cases where no information about the implementation of quality control or testing during
manufacture is available to help in assessing the quality of the lot. It is also used as the procedure for adjudicating in
9
cases of dispute. The cost of sampling, inspection and testing is a matter for agreement between manufacturer and
purchaser.
7.2 Inspection
Inspect the sample taken in accordance with 7.1.1 for compliance with the requirements of 5.5 and
section 6.
7.3 Testing
Before testing the sample taken in accordance with 7.1.1 check each length for compliance with the
requirements of 5.3 and 5.4
The test samples shall then be subjected to the tests for compliance with the requirements of 5.4.1 to
5.4.3
7.4 Place of testing
Unless otherwise agreed between the purchaser and the manufacturer at the time of ordering, all tests
and inspections shall be made at the place of manufacture prior to shipment..
7.5 Compliance
If after inspection and testing of the samples taken in accordance with 7.1.1 the number of defectives
found does not exceed the appropriate number given in table 8, the lot shall be deemed to comply with
the relevant requirements of the specification.
8. CERTIFICATE OF COMPLIANCE
The manufacturer shall, if requested, furnish the purchaser with a certificate giving the results of the
tests made on samples taken in accordance with 7.1.1
10
ANNEX A
Normative
Measurement of Diameter
A.1 Measurement of wire diameter.
A.1.1 Measurement of wire diameter before stranding.
Take at random, about 10% of the total number of wires (300 mm long) to be used to construct the
conductor and determine the diameter of each wire with a micrometer by taking two measurements at
right angles to each other at the center of the wire.
Take the average of all the measurements as the wire diameter.
A.1.2 Measurement of wire diameter after stranding
From each sample, take at random wire specimens (300 mm long each) as given in table A. Careful
straightens them not to stretch and determine the diameter of each specimen with a micrometer by
taking two measurements at right angles to each other at the center of the wire.
Take the average of all the measurements as the wire diameter.
TABLE A – Selection of test specimens
Number of wires
in conductor,
aluminium/steel
6/1
30/7
54/7
number of specimens per layer of completed
conductor
Centre
1
1
1
st
1 layer 2
3
1*
1*
nd
rd
th
layer 3 layer 4 layer
–
2
2
–
3
3
–
–
4
* Steel wires.
A.2 Measurement of overall diameter of a conductor
From each sample, cut a 300 mm long test specimen and careful straightens them not to stretch.
Determine the diameter of each specimen with a micrometer by taking two measurements at right
angles to each other at the center and near each end of the specimen. All measurements of a stranded
conductor shall be made over the strands and not at the interstices.
The overall diameter of a conductor shall be the average of the six measurements
Note – The micrometer used for diameter measurement should have flat surfaces on both the anvil and the end of
the spindle, with a resolution of 0.01 mm or better.
11
ANNEX B
Normative
Resistance measurement
Take at random, about 10% of the total number of wires to be used to construct the conductor. , the
wires shall be kept in the test area for sufficient time to ensure that its temperature has reached a level
which permits an accurate determination of resistance using the correction factors provided.
Measure and record the d.c. resistance of each wire together with the ambient air temperature. Convert the
measured values to standard values, in ohms per kilometre, using the equation
Rs = R × 1 000 kt /L
Where
Rs is the standard value of resistance, in ohms per kilometre;
R is the measured resistance, in ohms;
kt
is the temperature correction factor given by the exact formula
L
the temperature of the wire at the time of measurement in
is the measured length of the wire in metres.
Take the average of all the measurements as the resistance of a wire.
12
. Where t refers to
ANNEX C
Normative
Measurement of Breaking Strength
C.1 Measurement of breaking strength of the wire before stranding
C.1.1 Take at random, about 10 % of the total number of wires to be used to construct the conductor
(350 mm each). Measure and record diameter of each wire (see A.1.1) and make two thin gauge marks
symmetrically about the mid-point and 250 mm ± 1.0 mm apart.
C.1.2 Clamp each wire in turn in the tensile testing machine that the gauge marks are between, but just
clear of, the jaws. The load shall be applied gradually and the rate of separation of the jaws of the testing
machine shall be not less than 25 mm/min and not greater than 100 mm/min.
C.1.3 Elongate the specimen until it breaks. If a break occurs outside the gauge length or within 25 mm
of either gauge mark, discard the result and repeat as above until the specified number of breaks is
obtained within the prescribed portion.
C.1.4 Record the force required for breakage. The average of all the measurements shall be taken as
being the breaking strength of the wire.
C.2 Measurement of breaking strength of the wire after stranding
C.2.1 Stress wire as in C.1.2 to C.1.4 above to determine the breaking strength of wires taken in
accordance with table A above from each stranded conductor. The wire specimens shall not be
straightened other than as needed to ensure a materially straight pull between clamps.
C.2.3 Discard the lowest result, and record the mean and the lowest of the remaining results as the
mean and the minimum individual breaking strengths respectively of the wires of the stranded
conductor.
C.3 Measurement of elongation at break of steel wire
C.3.1 Measurement of elongation at break of steel wire before stranding
C.3.1.1 Take at random, about 10 % of the wire to be used to construct the conductor (350 mm each)
and proceed as in C.1.2 to C.1.3 above.
C.3.1.2 Lay the broken specimen on a smooth flat surface. Fit the fractured ends together as close as
possible and in a straight line. Measure the distance between the gauge marks to the nearest 0.5 mm.
C.3.1.2 Calculate the percentage elongation at break (E) for each specimen from the equation bellow
[(
)]
Where
E is the percentage elongation at break;
L1 is the gauge length after testing, in millimetres;
Lo is the gauge length before testing, in millimetres.
13
C.3.1.3 The average of all the measurements shall be taken as being the percentage elongation of the
steel wire before stranding.
C.3.2 Measurement of elongation at break of steel wire after stranding
C.3.2.1 Elongate the wire as in C.3.1.1 to C.3.1.2 above to determine the percentage elongation of
steel wires (350 mm each) taken in accordance with table A above from each stranded conductor. The
wire specimens shall not be straightened other than as needed to ensure a materially straight pull
between clamps.
C.3.2.2 The average of all the measurements shall be taken as being the percentage elongation of the
steel wire after stranding
NOTE - The elongation at break can also be determined by means of an automatic recording device attached to, or supplied as an
integral part of, the testing machine.
14
ANNEX D
Normative
Lapping Test
D.1 Take at random, about 10 % of the total number of wires (each 500 mm long) to be used to
construct the conductor.
D.2 Tightly wind each wire at a time, nine turns round a mandrel of diameter equal to wire diameter to
form a close helix. Unwind six turns and again wind these six turns closely in the same direction as in the
first winding. Wind and unwind the wire at a rate of approximately one turn per second. Keep the portion
that is being winded or unwinded under uniform tension, especially during unwinding, and at
approximately 90° to the longitudinal axis of the mandrel on to which it is being winded.
D.3 The wire shall not show any signs of cracks or of breaking.
15
ANNEX E
Normative
Twisting Test
E.1 Twisting test of the steel wire before stranding
E.1.1 Take at random, about 10 % of the total number of wires (150 mm each) to be used to construct
the conductor and make two thin gauge marks symmetrically about the mid-point and 100 mm ± 1.0 mm
apart.
E.1.2 Mount each wire in turn on two chucks, with their axes in the horizontal plane, the first axis being
free to rotate, and the second axis being fixed but able to slide backwards and forwards along the
common axis.
E.1.3 Grip the wire in the chucks such that the gauge marks are between, but just clear of, the jaws.
Apply an axial load to the second chuck; the load shall be just sufficient to prevent the specimen from kinking.
E.1.4 Rotate the free chuck at a speed not exceeding one revolution per second until the number of turns
required are reached or until the specimen breaks. All wires shall withstand the required turns. See 5.1 c (iii (b))
and 5.3.1 e
E.2 Twisting test of the steel wire after stranding
Twist the wire as in E.1.1 to E.1.4 above for steel wires taken in accordance with table A above from
each sample of a stranded conductor (150 mm each).
16
ANNEX F
Normative
Load at 1 % elongation
Take at random, about 10 % of the total number of wires to be used to construct the conductor (350 mm
each). Measure and record diameter of each wire (see A.1.1) and make two thin gauge marks
symmetrically about the mid-point and 250 mm ± 1.0 mm apart..
Clamp each wire in turn in the tensile testing machine such that the gauge marks are between, but just
clear of, the jaws. Apply the initial load given in table F appropriate to the standard diameter of the wire
and attach the extensometer, adjusted to the appropriate initial setting as given in table F. Then increase
the load uniformly until the extensometer indicates an extension of 2.50 mm and note the load Lo.
Calculate the corrected load, L, as follows:
The mean value of all measurement shall not be less than the appropriate value given in table 4.
Note - An extensometer shall be designed to measure the extension of small round wires.
TABLE F — Initial load and extensometer settings
for determination of load at 1 % elongation
Standard
diameter of
wire
mm
Initial load
Initial setting of
extensometer
2.36
2.59
0.86
1.03
0.125
0.250
2.79
3.00
3.18
1.20
1.39
2.03
0.250
0.250
0.375
3.35
3.66
4.72
2.60
3.09
5.14
0.375
0.375
0.375
1.57
2.37
0.19
0.86
0.125
0.125
kN
(mm)
17
ANNEX G
Normative
Mass, uniformity and adhesion of zinc coating.
G.1 Mass zinc coating
G.1.1 Take at random, about 10 % of the steel wire (100 mm) to be used to construct a stranded
conductor, straighten the specimens to a reasonable extent by hand. Ensure that the zinc coating is not
damaged in any way
G.1.2 Prepare a stripping solution of hydrochloric acid with a concentration of 1.13 g/ml to 1.19 g/ml by
density. Then dissolve 3.5 g of hexamethylene-tetramine (C6H12N4) in 500 mL of concentrated
hydrochloric acid ( =1.19 g/ml). Dilute this solution to 1000 ml with distilled water.
G.1.3 Clean each specimen by dipping them into a paraffinic hydrocarbon solution or other suitable
organic solvent then rinse with alcohol. Remove the specimens from the solution and dry them
thoroughly with a clean, soft cloth or tissue.
G.1.4 Determine the mass of the test specimen to the nearest 0.01 g.
G.1.5 Strip the zinc coating by immersing the test specimen completely in the stripping solution at
ambient temperature and left until the coating dissolves completely. A sufficient quantity of solution shall
be used to limit any changes in the composition of the stripping solution. After stripping, the test piece
shall be rinsed under running water and, if necessary, brushed to remove any loose substances which
may be adhering to the surface. It shall then be plunged into alcohol or any other appropriate solvent
and rapidly dried.
G.1.6 Determine the mass of the stripped specimen, to the nearest 0.01 g.
G.1.7 Measure the diameter d (in millimetres) of the stripped wire to the nearest 0.01 mm, by taking the
average of two or more readings.
G.1.8 Calculate the mass of the zinc coating, in grams per square metre using the following formula:
Where
2
is the coating mass per unit area, in grams per square metre (g/m )
is the mass loss of the sample by the chemical stripping, in grams (g)
is the mass of the sample before chemical stripping, in grams (g);
is the mass of the sample after chemical stripping, in grams (g);
2
is the coated surface area of the sample, in square millimeter (mm ) given by
18
Where
d is the diameter of the chemically stripped wire in millimeter (mm)
l is the length of the sample, in millimetres (mm)
Mass of the sample after stripping can be expressed as
(
)
which gives
where
is the density of
steel wire
Thus
may be written as
Substituting the value of density of steel then
1.9625
-3
10 g/mm
3
2
Converting to gram per square metre (g/m ),, it become;
1962.5 (g/m2)
G.1.9 The average of all the measurements shall be taken as being the mass of the zinc coating of the
steel wire.
Note - The same solution may be used repeatedly until the time required for stripping becomes inconveniently long.
G.2 Uniformity of zinc coating
G.2.1 Prepare a saturated copper sulphate solution by dissolving 360 g of copper sulphate crystals
.
(CuSO4 5H2O) in 1 litre of distilled water at a temperature of 23 . The solution shall under no
circumstance be heated. To prevent the reaction from taking too long, partition and crush the crystals to
be dissolved and then reduce bit by bit by successive amount of water to be used. Once the crystals
have dissolved completely the various solutions which have been prepared separately are mixed
together and stirred. Small amount of crystals shall remain undissolved at the bottom of the container as
the proof of saturation.
G.2.1 Neutralize the solution by adding 1 g of pure copper oxide or copper hydroxide in 1 litre of the
solution. Shake well and allow the solution to stand for at least 24 h before it is filtered or decanted for
use.
G.2.2
Do not test more than six specimens with the same solution.
G.2.3 Take at random, about 10 % of the steel wire (250 mm) to be used to construct a stranded
conductor, straightened them ensuring the coating is not damaged in any way. Clean the specimens by
dipping them into a paraffinic hydrocarbon solution or other suitable organic solvent then rinse with
alcohol. Remove the specimens from the solution and dry them thoroughly with a clean, soft cloth or
tissue. After cleaning the specimen shall only be touched at the end which is not to be dipped.
G.2.4 Pour the copper sulfate solution into the container (having internal diameter at least 60 mm) to a
depth of 200 mm and maintain the temperature of the solution at 23 °C ± 2 °C.
19
Subject the specimen to the relevant number of successive dips of exactly one minute or half a minute
as detailed table 2. Immerse only one specimen at a time. Do not disturb the specimen or agitate the
solution during the immersion. Withdraw the specimen after each dip, rinse it in clean, running water,
wipe it dry with a clean, soft cloth, and proceed immediately with the next dip. Carry out the one minute
dip first then half minute dip.
After final rinsing and drying, examine the specimen for any adherent red deposits of metallic copper on
the base metal. Disregard any deposits that have formed on the edges or within 25 mm of the end of any
specimen. All wires shall not form any red deposits. See 4.21(b)
G.3 Adhesion of zinc coating
Take at random, about 10 % of the steel wire to be used to construct a stranded conductor. Wrap each
wire specimen in turn round the mandrel to form six tight helical turns. The mandrel shall have diameter
of four times the nominal diameter of the wire specimen in the case of wires of diameter up to and
including 3.8 mm and five times the nominal diameter of the wire specimen in the case of wires of larger
sizes. Examine the zinc coating for flaking and cracking and note whether any zinc can be removed by
rubbing with the bare fingers. All wires shall not show sign of flaking and cracking. See 4.2 (c)
Note - The specimen shall be selected such that its length is enough to make six helical turns depending on the size
of the mandrel used.
20
ANNEX H
Informative
NOTES ON THE CALCULATION OF CONDUCTOR PROPERTIES
H.1 Effect of lay ratio on stranding
When straightened out, each wire (other than the central wire of the conductor) in any particular layer of
a stranded conductor is longer than the stranded conductor by an amount depending on the lay ratio of
that layer. This has a corresponding effect on the resistance and mass of the conductor.
In calculating the constants in table 6, the mean lay ratio, i.e. the arithmetic mean of the relevant
maximum and minimum values given in table 5, has been assumed for each layer.
H.2 Resistance of a stranded conductor
In aluminium conductors, steel reinforced, the conductivity of the steel core is neglected and the
resistance of the conductor is calculated with reference to the resistance of the aluminium wires only.
The resistance of any length of stranded conductor is the resistance of the same length of any one
aluminium wire multiplied by the appropriate constant given in table 6.
H.3 Mass of a stranded conductor
The mass of each wire (other than the central wire) in a length of stranded conductor will be greater than
that of an equal length of straight wire by an amount depending on the lay ratio of the particular layer.
The total mass of any length of conductor is obtained by multiplying the mass of an equal length of
straight wire by
1) the appropriate constant for aluminium given in table 6; and
2) the appropriate constant for steel given in table 6 and then adding the masses of the
aluminium wires and the steel core so calculated.
H.4 Calculated breaking strength of a stranded conductor
The breaking strength of a stranded aluminium conductor, steel reinforced, in terms of the strengths
of the individual component wires, is the sum of the strengths of the aluminium wires before stranding ,
plus the sum of the strengths of the steel wires calculated from the appropriate value of the minimum
load at 1 % elongation
.
21
BIBLIOGRAPHY
BS 215-2:1970 -:Specification for aluminium conductors and aluminium conductors, steel-reinforced for
overhead power transmission. Aluminium conductors, steel-reinforced
SANS 182-3:2003 - Conductors for overhead electrical transmission lines, Part 3: Aluminium
conductors, steel reinforced
ISO 7989-1:2006 - Steel wire and wire products — Non-ferrous metallic coatings on steel wire — Part 1:
General principles
ISO 7989-2:2007 - Steel wire and wire products — Nonferrous metallic coatings on steel wire — Part
2: Zinc or zinc-alloy coating
22