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The COPYRIGHT in the content of this brochure is owned by
Productions (Pty) Ltd
and is protected by COPYRIGHT LAW.
NO COPIES may be made of any of the drawings, designs, photographs or specifications of the products
featured in this brochure.
NO PRODUCTS may be manufactured by third parties utilising the drawings,
designs, photographs or specifications contained in this brochure or copies thereof.
WARRANTY
McWade Productions (Pty) Ltd. will make good,
•
by repair or,
•
at our option, by the supply of a replacement,
defects which, under proper use, appear in the goods, within a period of 12 months from the effective
date, after the goods have been delivered and arises solely from
•
faulty materials or
•
workmanship or
•
design,
provided that defective parts have been returned to us, if we shall have so required.
DISCLAIMER
Every effort has been made to ensure that the information contained in these data sheets are correct.
McWade disclaims responsibility for any action, proceedings, liabilities, claims, damages, costs,
losses and expenses in relation to or arising out of incorrect utilisation of this information.
McWade reserves the right to make changes to the data as and when required.
Page 1 of 45
Founded in 1961, McWade Productions has progressed in line with the growth of the Electrical Transmission Industry in
Southern Africa and is today a prime supplier of electrical components and accessory equipment to the African and
international Transmission and Distribution Electrical Industry.
The company has developed over the years a substantial manufacturing operation based in Olifantsfontein, Gauteng,
South Africa, operating to the requirements of ISO 9001-2000 and in accordance with local and international
specifications. On site facilities include a non-ferrous, sand and gravity die-casting foundry, machine shop as well as tool
and die-making facilities.
The company manufactures and offers a comprehensive range of equipment to meet both the market and customer’s
specific requirements. The products offered and detailed in this catalogue are summarised in the following product
ranges:
•
•
•
•
•
High Voltage Sub Station Inter Connecting Clamps up to 765kN
Insulators
Isolators
Compression Tooling
Transmission and Distribution Line Hardware
Design and consulting services are available to provide recommendations as to the most suitable type of equipment,
connections and installation procedures to suit customer requirements.
The
•
•
•
•
company’s customer relations policy is based on giving complete satisfaction to our clients and includes for:
In-house design
Documentation and technical back-up
Local and International sourcing of specialised equipment to suit the customer’s requirements
Manufacture, source and supply of full packages for sub stations and line projects
Page 2 of 45
CURRENT CARRYING CLAMPS FOR USE IN
ELECTRICAL SUB-STATIONS
INTRODUCTION
1.
McWade Productions (Pty) Ltd manufactures and markets a comprehensive range of both aluminium and copper alloy
clamps for use in all electrical conductor and/or tubular busbar applications. This range varies from small conductor
termination clamps used at less than 500 volts up to large diameter tubular busbar clamps suitable for use on
250mm diameter busbars at 765kV and rated in excess of 6 500 amps. The clamps are manufactured to the
company’s own designs and/or to meet specific customer requirements.
2.
When designing substations and, particularly when determining the type of current carrying clamp to be utilised,
the maximum continuous load rating and short circuit currents are critical factors to take into account. This is
particularly important with the high load factors now occurring in some power systems. Internationally, substation
design now tends towards the use of tubular bus systems as opposed to overhead strung conductor type busbars
where with current ratings in excess of 3 000 amps, strung busbars require more than 3 conductors per bus phase
with the resultant complications arising in the connection of these bundle conductors. Bundle conductor bus
systems are subject to bundle collapse under short circuit conditions which generate serious shock forces at
attachment points. At voltages in excess of 88/132kV tubular bus arrangements lend themselves more towards a
superior corona free design than do bundle conductor bus systems. Furthermore, the use of tubular bus systems
provides for a lower profile and more aesthetically acceptable substation design. When utilising tubular busbars,
short circuit forces between phases with relative small phase spacings, do present a problem and these forces must
be allowed for in the mechanical strength in the clamps and the post insulators used.
3.
The clamps, as detailed in this catalogue, are manufactured to comply with the requirements of the National
Electrical Utility of South Africa being Eskom as well as international specifications.
a.)
Aluminium Clamps
Aluminium alloy clamps are predominantly used for the connection of stranded aluminium conductors and/or
tubular aluminium busbars to each other and to hot dip tinned copper equipment studs and terminals. Where
corrosion is a prime factor, and the terminals not tinned, bi-metallic washers and/or sleeves should be fitted
to the copper terminals. All aluminium alloy clamps are supplied pre-greased if required.
b.)
Copper Clamps
Copper alloy clamps, which are hot dip tinned, are predominantly used in copper to copper applications. Where
corrosion is a factor to be considered, they are also used in copper to aluminium applications. Copper clamps
are supplied un-greased.
Page 3 of 45
TECHNICAL
CORROSION OF INTER-CONNECTOR CLAMPS
Two factors are associated with corrosion:
1.
Atmospheric action
2.
Galvanic action
For atmospheric action to result in corrosion there must be moisture and oxygen present.
Galvanic action results in corrosion when two dissimilar metals in the electrolytic series e.g. aluminium and copper are in
physical contact. In this case moisture acts as an electrolyte.
In such an instance the copper becomes the cathode and receives a positive charge. The aluminium becomes the anode
and receives a negative charge.
The resultant current flow attacks the aluminium leaving the copper unharmed.
Both factors described above are influenced by environmental conditions.
This occurs in rural areas to a lesser extent than in urban centres and more so in heavy industry locations – steelworks,
chemical plants, refineries etc.
The problem of the mechanical jointing of two dissimilar metals in physical contact with each other, such as aluminium
and copper stems from their difference in electrolytic potential.
The extent, or severity, of the corrosive action is proportional to distance or separation of the metals in the list i.e. the
magnitude of the difference in electrolytic potential of the two metals which, in the case of aluminium and copper is
quite considerable.
Aluminium to Aluminium Connections
No problem exists in the jointing of these conductors as electrolytic action is non existent. Nevertheless, care must be
taken to prevent crevice corrosion and to select an aluminium alloy connector body not liable to stress corrosion cracking.
Aluminium to Copper Conductor Connections
The best choice is an aluminium bodied connector since it is not subject to the galvanic attack of the more vulnerable
element – the aluminium conductor.
Nevertheless, it is good practice to use an inhibitor grease, on the aluminium connector body or on the aluminium
conductors and additionally where-ever possible to install the aluminium conductor above the copper to prevent pitting
from the galvanic action of copper salts washing over the aluminium connector and conductor when in a lower position,
alternatively a hot tin dipped copper alloy connector is to be utilised or an aluminium connector with a bi-metallic sleeve
placed over the copper conductor.
Page 4 of 45
Electrical Jointing of Aluminium
A particular phenomenon associated with jointing of aluminium conductors concerns the oxide film that forms rapidly on
the surface of freshly extruded or cleaned aluminium exposed to air.
This oxide film acts as an insulating medium and must be removed with a scratch steel brush or abrasive paper in order
to achieve a satisfactory and reliable electrical joint.
This problem with aluminium is that the freshly cleaned surface is liable to fast oxide formation, hence it is important to
coat the surface with an oxide inhibitor immediately after cleaning.
The function of a contact/compression compound is:
a) Firstly to act as an oxide inhibitor by preventing the ingress of moisture and air and to provide for continuing
protection against further corrosion of the electrical joint in its working environment.
b) Secondly, with certain compression greases under compressive force, its high content of sharp metallic particles
penetrates through any remaining oxide film to provide multi contact current carrying bridges.
Inter-strand resistance
The high contact resistance due to aluminium oxide on the strands of aluminium conductors may be responsible for the
poor distribution of current throughout the conductor strands. Thus some strands may carry much more than their
share of the current, with consequent overheating of the conductor.
The most effective way to overcome inter-strand resistance in aluminium conductors is by the use of compression
connectors filled with a compression-jointing compound.
Note: While oxide films on copper are conducting mediums, and more easily broken by contact pressure, it is a
recommended practice to clean badly tarnished old copper surfaces with a scratch brush.
Page 5 of 45
ALUMINIUM ALLOY BOLTED/COMPRESSION TYPE
CURRENT CARRYING CLAMPS
General Features
A current carrying clamp can only satisfactorily serve the function that it is designed for, which is the transferral of
current flow from one busbar to another, by the optimum design of the contact surface areas coupled with the contact
pressure exerted through the clamping covers and their associated clamping systems. Intensive research both in South
Africa and in Europe, has resulted in the design of the clamps detailed in this section, such clamps being designed for
use at 765kV and capable of carrying current loads in excess of 3 500 amps on a continuous basis. The clamps as shown
comply with the requirements of the West German specification number VDE. 0220 and the Eskom (SA) specification
number NWS1671. General features of these clamps are:
1.
The Compression Tube
The SABS report number 771/8322/R46, “Testing of Line Clamps” clearly shows the best method of making
electrical connections to multi-layer aluminium conductor to be the compression technique. In fact, the SABS
experiments yielded the following mean percentage increase in voltage drops over the entire aging test carried out
on a variety of different current carrying clamps.
Compression Tube
Three bolted clamping covers
Explosive wedge compression
Single bolted clamping cover
40.80%
48.50%
75.63%
182.60%
The compression tube incorporated in bolted compression clamps is specially produced for this application. It is
precisely dimensioned in accordance with the “compression efficiency formula” resulting from years of research in
Europe. To ensure correct installation, it is indelibly marked with the appropriate conductor size, the crimping die
reference number and the required points of compression. It is supplied with an internal coating of the correct
compression grease.
2.
Bolted Clamping Covers
Although compression tubes should be used for stranded conductor connections wherever possible and bolted joints
reserved for attachment is feasible, the nature of the tee clamp necessitates the use of a bolted connection on the
“run” conductor. Thus special care must be taken with this clamp half.
On installation, micro-contacts are formed between the clamp body and the conductor. The summated areas of
these individual micro-contacts make up the total actual contact area. This area only amounts to between 1% and
5% of the apparent, or overlap, surface. Thus, if the permissible current density is 10 amps/mm², this must be
interpreted as approximately 0.2 amps/mm² of overlap surface.
The quality and life of the connection is determined by the actual contact area formed on installation and the
preservation of such contact area. The contact area can reduce with time and one of the prime causes of this is
creep of the conductor material – particularly for large diameter conductors with four or more strand layers. The
covers fitted to these clamps are made of carefully selected alloys, gravity die cast or drop forged to yield the
ideal strength and elasticity characteristics so that a high residual contact pressure is maintained. The number of
clamping covers per connection depends on the current loads of the conductors and on whether stranded
conductors, tubes or studs are to be connected.
Page 6 of 45
3.
The Clamp Body
The clamp body is provided with a large conductor seating area, machine-grooved for penetration of the conductor
oxide layers and the creation of increased actual contact area. They further assist in the distribution of the bolt
forces over the entire clamp length. Bolts are locked into the clamp body, thus requiring tightening of the nut only.
The body is indelibly marked with the clamp type number and conductor size.
4.
The Welded Joint
Intensive research into welding techniques, both hand and machine methods, has resulted in joints of high quality.
Tests in South African and European laboratories show the connection to be physically, electrically and mechanically
sound. On-going quality assurance procedures adopted by McWade Productions guarantee that no problems will
arise in this area, or for the unit as a whole.
5.
Run And Tap Configuration
International understanding is that the RUN conductor (immaterial whether stranded or tubular conductors) is
always in the horizontal plane and that the TAP conductor (whether stranded or tubular conductor) is in the vertical
plane – see sketch below.
The K type cross clamp is specifically designed for use with a SOLID EQUIPMENT STUD and STRANDED
CONDUCTORS. The K clamp is manufactured in compliance with the Eskom NWS 1671 specification, which
specification calls for one half of the clamp having both the horizontal and vertical cross grooves smooth bored to
suit 26 or 38mm dia equipment studs – with the other half of the clamp having the horizontal and vertical cross
grooves either machined or cast serrated to suit stranded conductors of 16.3, 19.0, 21.0, 26.5 and 38.5mmdia.
These are the standard Eskom stud and conductor diameters and the McWade manufactured K clamps are
manufactured to suit these stud and conductor sizes where in all instances the stud is normally classified as the tap
side of the clamp, immaterial of whether the stud is vertically or horizontally mounted.
Where a standard K clamp is required to be used with either different conductor or stud sizes, the standard K
clamp as manufactured requires to be modified to suit these different stud/conductor sizes. It is required that
customers specify both the RUN size and the TAP size in each specific case.
Page 7 of 45
6.
Preferred South African Substation Conductors
A.)
ASCR Conductors to BS.215
Code Name
Wolf
Bear
B.)
Reference Area
Aluminium/Steel
mm²
160/40
250/40
No. & of ∅ of Wires
Aluminium/Steel
mm
30/7/2.59
30/7/3.35
Nominal
Diameter
mm
18.13
23.45
No. and Diameter
of Wires
mm
19/3.25
37/3.78
61/4.26
Nominal
Diameter
mm
16.25
26.46
38.34
kg
7.28
1219
Current Rating
Amps
70°C
90°C
371
482
504
665
Mass per
km
kg
433
1150
2397
Current Rating
Amps
75°C
90°C
365
470
647
860
986
1353
Mass per
AAC Conductors to BS.215
Code Name
Hornet
Centipede
Bull
Reference Area
mm²
150
400
800
NB.: Above current ratings are based on a wind speed of 1.6 kms per hour and at an ambient temperature of 40°C
(the 75 and 90°C temperatures in the above table refer to the conductor temperature).
Page 8 of 45
INSTALLATION PROCEDURE
All inter-connector clamps as manufactured by McWade Productions are designed to suit both the electrical transfer
current carrying capacity of the stranded/tubular busbar it is to be utilised with and the mechanical strengths
associated with the rated short circuit current.
All international manufacturers’ inter-connector clamps can only perform to their designed electrical and mechanical
functions subject to the correct on-site installation procedures being adhered to which are:
1.
Clamp Selection
The first step is to ensure that the clamp to be utilized is suited to the application in question. McWade clamps are
all stamped with both Type Number and Conductor sizes and these can be compared to those specified on the
installation drawings. It should be noted that types KC and YC are to be used solely for the compression connection
of conductors to equipment terminals. The only time a bolted connection is made to stranded Conductors is in the
case of TEE joints or tap-off where the clamp types T, TC or K are utilised.
2.
Cleaning Procedure
All clamps are supplied ex-factory in heavy duty heat-sealed plastic bags and the clamps should only be removed
from these plastic bags immediately prior to installation and after correct cleaning and preparation of the
installation connection area.
Aluminium alloys as utilised in stranded or tubular conductors are prone to immediate oxidisation after extrusion.
This oxide layer can achieve a maximum thickness of 500 – 1000nm and acts as an insulating medium. The dynamics
of an oxidised aluminium connection results in a very high resistance interface and causes thermal instability leading
to connection failure. To ensure proper contact between the busbar and clamping contact areas, it is necessary to
clean away the layer of aluminium oxide in the contact areas.
Preparation of Contact Surfaces
ALL CONTACT SURFACE AREAS must be strongly brushed with a steel-wire brush alternatively with an aluminium
oxide emery cloth grade 80 – 180 and then wiped clean with a dry cloth. Immediately thereafter the contact
surfaces of the stranded/tubular busbar and inter-connector clamp are to be greased with a high-melting point nonoxidant grease to a 0.25 – 0.5mm minimum thickness. This greasing process must be immediately followed up with
the application of the inter-connector clamp to the respective busbars.
Care should be taken that the contact surfaces, which have been cleaned and greased, are kept free of sand and
other foreign matter. In the case of accidental pollution these surfaces shall be cleaned with a suitable solvent and
the cleaning and greasing process repeated.
Equipment terminal studs and palms whether of aluminium or plated copper are to be cleaned in accordance with the
above procedure.
Certain compression compounds contain an aluminium grit and upon compression of the conductor sleeve on
conductor, the compressive force drives the grease, containing sharp metalgrit particles, between the conductor
strands, at the same time forcing the conductor strands into a semi hexagonal shape, this effect breaking down the
oxide film around the inner conductor strands and providing for a point-point contact.
Page 9 of 45
3.
Clamp Installation
When installing the inter-connector clamp, ensure that the conductor seating areas match those of the busbar that
the clamp is to be fitted to. In cases where the aluminium tubular busbar is slightly beyond the tolerances for
diameter and ovality, the clamp can be accurately bedded onto the tube by hammering around the outside of the
clamp body shell with a rubber hammer. This can only be done whilst the clamp is clamped onto the tubular basbar
and the bolts are to be re-set afterwards with a torque wrench.
4.
Clamping Sequence
Once the caps are correctly positioned, final bolt tightening is to take place according to defined sequences in
order to apportion correct stresses to the conductor/tubes as well as the inter-connector bodies.
5.
Positioning of the Caps
It is imperative that the clamping covers are tightened down in a parallel sequence so that the gap between the
clamp’s body and the clamp’s cover is equal on both sides.
6.
Bolt Tightening Torques
All clamps are fitted with bolts, nuts and washers of either:
a) 8.8 grade high tensile steel bolts (HDG),
b) Stainless steel grade A2/A4,
c) Aluminium alloy grade 7075 – P60.
All inter-connector clamps are designed to provide a maximum effective contact surface between the busbar and
the inter-connector clamp for the efficient transfer of electrical current. This maximisation of effective contact
surfaces can only be achieved by the correct contact pressures of >6N/mm² being applied to the clamp. This can
only be achieved by all bolts being tightened with a torque wrench to the required torque as stated below:
Bolt Tightening Torque (Nm)
Bolt Thread
Spanner
Width
Steel (HDG)
S/Steel
Bronze
Alum
5,6
8,8
A2
F60
7075 (p.60)
M8
13
-
15
20
15
10
M10
17
13
26
35
26
21
M12
19
23
45
60
45
36
M14
22
35
60
80
70
55
M16
24
56
75
110
-
70
Page 10 of 45
7.
Compression Joints
The conductor size to be compressed must correspond to the conductor diameter stamped on the compression tube.
The conductor is to be cleaned as stated above and then cut to the required length. It is inserted into the pregreased compression tube until the end is firmly against the clamping body stop. Compression is to be undertaken
using a suitable 30/45-ton rating power operated compression tool. Compression dies are to be checked to meet
with the following sizes:
Hexagon Type Crimped Connections
Conductor
Type
Die Ref.
No.
Tube O/D
(mm)
Die Size
(mm)
Bull
58
58
49
Centipede
42
42.5
36
Note:
Dimension
“A” (mm)
Max 51
Min 48
Max 37.5
Min 35.2
Die Bite
Width
25
40
These are the commonly used Conductors in Sub-stations in South Africa.
information is available on request.
For all other connections,
Dies reference numbers are to be checked to the number stamped on the compression tube. Compression of the
tube and conductor should commence from the conductor end towards the clamp body and compression must be
effected over the compression marks detailed on the tube.
Compression tools are to automatically bypass on complete compression and under no circumstances should the die
pressure be released before bypass is reached. After full compression the die numbers 42 or 58 will be imprinted
onto the tube and serve to indicate both satisfactory and complete compression.
Compression tools are to be treated strictly in accordance with the operating instructions supplied. A light film of
pure white Vaseline should be applied to the compression die faces after every 5 – 10 compressions in order to
extend die life and facilitate die slide over the compression tube surface. Any compression die flashes should be
removed with a file.
Upon completion of the clamp installation and checking that all bolts are correctly torqued surplus grease should be
wiped away.
Page 11 of 45
TUBULAR BUSBAR CLAMPS IN ALUMINIUM ALLOY
INTRODUCTION
The aluminium alloy tubular bus current carrying clamps depicted in this section are manufactured in certified aluminium
alloys, namely aluminium alloy grade LM-6 as a standard, alternatively in aluminium alloy LM-25 heat treated to a T6
temper where a clamp is required to comply with a higher strength rating.
Tubular Busbar
Standard South African busbar tubes are supplied in either the alloys 6101-A and/or 6261-TF which are both suitable
for electrical purposes. The 6261-TF alloy has better mechanical properties, but somewhat poorer electrical properties
than the 6101-A. However, for application of HV yards, where long spans are essential, the 6261-TF alloy with superior
mechanical properties is preferred. All imported Aluminium Alloy Tubular Busbar are in the grade 6101-BT6.
Alloy Type
6101-A
6261-TF
6101-BT6
Max Yield Strength
MPa
170
240
160
Electrical Resistivety
at 20°C in mm²/m
0.03133
0.037
0.0333
Page 12 of 45
Busbar Temp.
mm
80
100
120
150
160
200
250
85°C
A
Max. Length which
can be supplied
Permanent
Electrical Load
± Tolerance in outer
diameter incl. deviation
from roundness
Weight
Cross Section
Wall Thickness
Outer Diameter
Standard Tubular Busbar
Maximum sag (cm) due to own weight, 2 supports,
(for 3 supports multiply listed values by 0.415)
Support spacing (m)
mm
mm²
kg/m
65°C
A
mm
m
6
8
10
12
14
4
955
2.58
1,400
1,860
0.6
19
0.9
2.8
6.8
14.1
26.1
16
18
20
22
5
1,178
3.18
1,560
2,070
0.6
0.9
2.9
7.0
14.4
26.8
45.6
6
1,395
3.77
1,690
2,240
0.6
0.9
3.0
7.1
14.8
27.5
46.8
8
1,810
4.89
1,920
2,550
0.6
1.0
3.1
7.5
15.5
28.8
49.1
10
2,199
5.94
2,110
2,790
0.6
1.0
3.2
7.9
16.4
30.3
51.8
4
1,206
3.26
1,690
2,240
0.7
0.6
1.8
4.3
8.9
16.4
28.0
5
1,492
4.03
1,880
2,490
0.7
1.8
4.3
9.1
16.7
28.5
6
1,772
4.78
2,040
2,710
0.7
1.8
4.4
9.2
17.1
29.1
46.6
8
2,312
6.24
2,320
3,070
0.7
1.9
4.6
9.6
17.8
30.3
48.75
73.9
10
2,827
7.63
2,540
3,360
0.7
2.0
4.8
9.9
18.4
31.4
50.3
76.7
4
1,458
3.94
1,950
2,580
0.7
1.2
2.9
6.1
11.3
19.2
30.8
5
1,806
4.88
2,170
2,880
0.7
1.2
3.0
6.2
11.4
19.5
31.2
47.6
6
2,149
5.80
2,370
3,140
0.7
1.2
3.0
6.3
11.6
19.8
31.7
48.3
8
2,815
7.60
2,700
3,580
0.7
1.3
3.1
6.5
12.0
20.4
32.7
49.9
73.1
10
3,456
9.33
2,960
3,920
0.7
1.3
3.2
6.7
12.4
21.1
33.9
51.6
75.6
12
4,072
10.99
3,130
1.4
3.3
6.9
12.8
21.8
35.0
53.3
78.0
4
6
8
1,835
2,714
3,569
4.95
7.33
9.64
4
1,960
5.29
5
2,435
6.57
6
2,903
7
25
25
0.4
24
26
28
30
45.6
4,150
0.7
2,900
3,500
4,000
1.0
1.0
1.0
25
2,520
3,330
1.0
25
1.6
3.3
6.2
10.6
16.9
25.9
37.8
2,790
3,700
1.0
1.6
3.4
6.3
10.7
17.2
26.2
38.3
54.3
7.84
3,060
4,050
1.0
1.7
3.4
6.4
10.9
17.4
26.5
38.3
55.0
3,365
9.08
3,270
4,330
1.0
1.7
3.5
6.4
11.0
17.6
26.8
39.3
55.6
8
3,820
10.31
3,490
4,630
1.0
1.7
3.5
6.5
11.1
17.8
27.2
39.8
56.4
10
4,712
12.72
3,830
5,070
1.0
1.7
3.6
6.7
11.4
18.3
27.9
40.8
57.8
12
5,579
15.06
4,060
5,380
1.0
1.8
3.7
6.9
11.7
18.7
28.5
41.8
59.2
4
2,463
6.65
3,030
4,010
1.2
0.4
1.0
2.1
3.8
6.7
10.8
16.4
24.0
34.0
5
3,063
8.27
3,410
4,520
1.2
0.4
1.0
2.1
4.0
6.8
10.9
16.5
24.2
34.3
6
3,657
9.87
3,720
4,920
1.2
0.4
1.0
2.2
4.0
6.8
11
16.7
24.5
34.6
47.7
63.8
8
4,825
13.0
4,270
5,660
1.2
0.4
1.1
2.2
4.1
7.0
11.2
17.0
24.9
35.3
48.6
65.4
86.1
10
5,969
16.1
4,680
6,200
1.2
0.4
1.1
2.3
4.2
7.2
11.4
17.4
25.4
36.0
49.6
66.8
88.0
12
7,087
19.1
4,990
6,610
1.2
5.0
1.1
2.3
4.3
7.3
11.6
17.7
25.9
36.7
50.6
68.0
89.6
5
3,848
10.4
4,140
5,490
1.5
25
0.3
0.7
1.4
2.5
4.3
6.9
10.5
15.4
21.8
30.0
40.3
53.1
6
4,599
12.4
4,520
5,990
1.5
25
1.4
2.5
4.3
6.9
10.6
15.5
21.9
30.1
40.5
53.4
25
1.9
1.9
2
0.2
0.1
0.1
0.7
47.3
8
6,082
16.4
5,190
6,870
1.5
25
1.4
2.6
4.4
7
10.7
15.7
22.2
30.6
41.2
54.3
10
7,540
20.4
5,700
7,560
1.5
25
1.4
2.6
4.5
7.2
10.9
16.0
22.7
31.2
42.0
55.4
12
8,972
24.2
6,100
8,080
1.5
25
1.4
2.7
4.5
7.3
11.1
16.2
23.0
31.6
42.5
56.1
14
10,380
28.0
6,420
8,500
1.5
23
1.5
2.7
4.6
7.4
11.3
16.5
23.3
32.1
43.2
57.0
16
11,762
31.8
6,640
8,800
1.5
19
1.5
2.8
4.7
7.5
11.5
16.8
23.8
32.7
44.0
58.0
Page 13 of 45
INSTALLATION PROCEDURE
When installing full or half expansion inter-connector clamps, care must be taken for the allowance of the thermal
expansion of the relevant basbar tube, be it aluminium or copper. An estimate of the expansion of various tubes due to
thermal expansion at various temperature changes is given in the tables below:
1.
Calculation of Thermal Expansion in Aluminium Tubes in mm
Length
of Tube
in
Meters
2.5
Temperature Difference UT. in °C
10
20
30
40
50
60
70
80
90
100
0.6
1.2
1.8
2.4
3.0
3.6
4.2
4.8
5.4
6.0
5.0
1.2
2.4
3.6
3.0
6.0
7.2
8.4
9.6
10.8
12.0
10
2.4
4.8
7.2
9.6
12.0
14.4
16.8
19.2
21.6
24.0
20
4.8
9.6
14.4
19.2
24.0
28.8
33.6
38.4
43.2
48.0
30
7.2
14.4
21.6
28.8
36.0
43.2
50.4
57.6
64.8
72.0
40
9.6
19.2
28.8
38.4
48.0
57.6
67.2
76.8
86.4
96.0
50
12.0
24.0
36.0
48.0
60.0
72.0
84.0
96.0
108.0
120.0
Temperature Co-efficient of Linear expansion (temp. range -20° + 200°C
Aluminium: 23 x 10-6 (0,000023 per centigrade degree)
Example of the Calculation of Thermal Busbar Expansion:
Aluminium basbar tube, length
Temperature difference
Assembly temperature
=
t=
=
t=
=
10m
Max. Op. Temperature – Min. Op. Temperature
(+80°C) – (-20°C)
100°C
+20°C
For complete expansion length refer to table = 24.0mm.
Temperature difference between the final temperature (+80°C) and the assembly temperature (+20°C) is therefore
60°C. Referring to the above table, the corresponding expansion difference will be 14,4mm. The clamp must
therefore be mounted in such a way that a shift of at least 14,4mm in the direction of the clamp centre is
guaranteed. A shift in the opposite direction in accordance with the temperature difference of (+20°C) assembly
temperature and (+20°C) being the lowest final temperature - 40°C. Referring to the above tables, this value is
given as 9.6mm.
2.
Short Circuit Forces on Clamps
Notes:
Tube
Size
Current
Rating
Phase *
Spacing
Short
Circuit
mm
80 x 8
100 x 8
120 x 8
150 x 8
200 x 8
250 x 8
Amp
2 300
2 800
3 300
4 000
5 200
6 300
m
2.3
2.3
2.3
4.5
4.5
4.5
kA
16
25
25
50
50
50
Transverse Short
Circuit Forces on Clamps
and Post Insulators
kN
4
6
6
16
16
20
* Indicates the phase spacing at which maximum short circuit forces occurs.
Clamps are designed to have a factor of safety of 2:1 with respect to the specified load. Unless the min. mechanical load
is specified, the standard strength LM-6 alloy clamp, is supplied.
Page 14 of 45
3.
Busbar Tube Vibration Damping
Aluminium tubular busbars are subject to wind-generated vibration and oscillation. Because of the low self-damping
of tubular busbars very slight excitation forces will suffice to excite the tubes to vibrations amplitudes of the
order of the tube diameter, when there is a resilience of the excitation force with a natural frequency of the tube.
These high amplitudes produce additional dynamic stresses inside all structural parts and it is often necessary to
dampen this tube oscillation by the insertion of AAC conductor into the busbar. The increased self damping
provided by the insertion of damping conductor delays the onset of resilience build-up and this limits the maximum
amplitudes created by a given excitation force.
Recommended Damping Cables
As a rule it is normally sufficient to insert one conductor
into a tube, but in order to increase the safety and to
maintain maximum damping effect it is advisable to insert
two conductors into the tube (one at each end running for
2/3 of the tube length). The following table shows
recommended damping conductor sizes. A drain hole of
10mm diameter should be drilled at bottom centre point of
tubes to facilitate drainage of condensate moisture.
4.
Tube-Ø
mm
Al-cable
mm
63
80
100
120
160
200
250
120
150
240
300
500
625
625
Permissible spacing
between supports
without damping cables
m (nominal values)
3.0
3.5
4.5
5.5
7.5
9.5
12.0
Nominal Linear Expansion of Tubular Busbars
Temperature
°C
20
30
40
50
60
70
80
Expansion in mm/Per Meter
Aluminium
Copper
0.69
0.51
0.92
0.68
1.15
0.85
1.38
1.02
1.61
1.19
1.84
1.36
2.12
1.58
Page 15 of 45
COPPER CLAMPS
INTRODUCTION
The copper current currying clamps as depicted in this section are manufactured from the material grade LG 2 in
accordance with BS 1400.1969. All clamps are supplied hot tin dipped and can be supplied silver plated if required.
1.
Calculation of Thermal Expansion in Copper Tubes in mm
Length of Tube
in Meter
Temperature Difference UT. in °C
10
20
30
40
50
60
70
80
90
100
2.5
0.42
0.85
1.3
1.7
2.2
2.6
3.0
3.4
3.9
4.4
5.0
0.85
1.7
2.6
3.4
4.3
5.2
6.0
6.8
7.7
8.6
10
1.7
3.4
5.1
6.8
8.5
10.2
11.9
13.6
15.3
17.0
20
3.4
6.8
10.2
13.6
17.0
20.4
23.8
27.2
30.6
34.0
30
5.1
10.2
15.3
20.4
25.8
30.6
35.7
40.8
46.2
51.6
40
6.8
13.6
20.4
27.2
34.0
40.8
47.6
54.4
61.2
68.0
50
8.5
17.0
25.5
34.0
42.5
51.0
59.5
68.0
76.5
85.0
Temperature Co-efficient of Linear expansion (temp. range -20° + 200°C
Copper: 17 x 10-6 (0,000017 per centigrade degree)
2.
Nominal Linear Expansion of Tubular Busbars
Temperature
°C
20
30
40
50
60
70
80
Expansion in mm/Per Meter
Aluminium
Copper
0.69
0.51
0.92
0.68
1.15
0.85
1.38
1.02
1.61
1.19
1.84
1.36
2.12
1.58
Page 16 of 45
Electrical Jointing of Aluminium
A particular phenomenon associated with jointing of aluminium conductors concerns the oxide film that forms rapidly on
the surface of freshly extruded or cleaned aluminium exposed to air.
This oxide film acts as an insulating medium and must be removed with a scratch steel brush or abrasive paper in order
to achieve a satisfactory and reliable electrical joint.
This problem with aluminium is that the freshly cleaned surface is liable to fast oxide formation, hence it is important to
coat the surface with an oxide inhibitor immediately after cleaning.
The function of a contact/compression compound is:
c) Firstly to act as an oxide inhibitor by preventing the ingress of moisture and air and to provide for continuing
protection against further corrosion of the electrical joint in its working environment.
d) Secondly, with certain compression greases under compressive force, its high content of sharp metallic particles
penetrates through any remaining oxide film to provide multi contact current carrying bridges.
Inter-strand resistance
The high contact resistance due to aluminium oxide on the strands of aluminium conductors may be responsible for the
poor distribution of current throughout the conductor strands. Thus some strands may carry much more than their
share of the current, with consequent overheating of the conductor.
The most effective way to overcome inter-strand resistance in aluminium conductors is by the use of compression
connectors filled with a compression-jointing compound.
Note: While oxide films on copper are conducting mediums, and more easily broken by contact pressure, it is a
recommended practice to clean badly tarnished old copper surfaces with a scratch brush.
Page 17 of 45
Page 18 of 45
Section Lengths Available
McWade strain and suspension insulators are available in lengths appropriate for 11kV through 132kV.
shorter lengths can be produced for special projects. Length increments are approximately 38mm.
Longer or
Insulation Co-ordination
The operating performance of a transmission line depends on its insulation level. It must not flash over under practically
any operating condition. Several methods of co-ordination of line and station insulation have been proposed. Generally,
the best method is to establish a definite common insulation level for all the station insulation and then match that level
with the line insulation. With this approach, the task is limited to three fundamental requirements:
1.
2.
3.
selection of Basic Insulation Level (BIL),
specification of insulation with flashover characteristics equal to or greater than the selected BIL and
the application of suitable over voltage surge protection.
Satisfactory performance is generally achieved with an insulator which has a dry 60Hz flash over of three to five times
the phase-to-ground voltage and a leakage distance approximately twice the shortest air gap (strike) distance.
Corona Performance
McWade suspension and strain insulators are RIV and corona free through 132kV, by the use of integral Stress
Distribution Disk (SDD). The table below details the rings necessary for voltages equal to or exceeding that listed in
the column header.
Insulator
Orientation
Strain/
Suspension
Top
Bottom
Top
Bottom
Line Post
SDD
Up to 66kV
None
None
None
None
66kV –
132kV
None
SDD
None
None
Page 19 of 45
INSTRUCTIONS FOR HANDLING, STORAGE AND CLEANING OF POLYMER INSULATORS
Handling
While these insulators are remarkably resistant to damage, care should always be taken to avoid dragging on the ground,
or against structural numbers.
The insulators will accept moderate bending or twisting, but severe bending or torsional loading should be avoided.
Bending loads are sometimes easily applied to ball or socket fittings, watch especially for ball shank bending and/or
socket cotter crushing.
If rings are to be added, follow manufacturer’s recommendations for position and orientation. This information is
provided by a small drawing/tag attached to each ring.
Installation
Always examine insulators for handling and shipping damage.
Install insulators so that moisture will drain from the sheds, the shed angles make this easy in standard line
construction. If unique construction requirements – e.g. “uphill deadends”, result in sheds which will not drain, reverse
the insulators or use special insulators with inverted sheds. A good rule when the insulator must be installed with
upward-sloping sheds is to make sure the insulator position is within 45 degrees of horizontal.
For safety reasons and to prevent insulator damage, crews MUST AVOID climbing on, walking on, or hanging ladders
from the insulator surfaces.
Storage
Store insulators in an area free of standing water. Avoid direct contact with transformer oil, hydraulic oil, or other
similar petroleum derivatives.
The light weight of the insulators permits storage on light duty floors and foundations. Suspension insulator design
encourages vertical storage (hanging or standing), reducing the floor area required. For long units standing vertically, a
simple rack may be useful to provide support.
Cleaning
McWade Insulators normally require no cleaning, washing, or other routine maintenance. Chalking of the rubber
weathersheds surfaces that are exposed to sunlight is normal and helps protect the polymer surface from the sun’s UV
rays. Thus, chalky white surface film need not be removed by cleaning.
Washing or cleaning may be required if the insulators are installed in areas of severe environmental contamination and
where there are indications of abnormal leakage currents or scintillation on the insulator surface due to fog, mist, or
other conditions of light wetting.
In the event that washing or cleaning is required, the procedures are outlined in ANSI/IEEE 957 “Guide for Insulator
Cleaning”.
Page 20 of 45
INSULATOR PART NUMBER MAKE UP
7 0 0 6 0 2
Example, Part No.:
70
06
1.
50 – 120Kn Earth Wire
& Arch Horn
60 – 70kN Earth Wire
& Arc Horn
70 – 40kN
80 – 2 Disc Equiv.
81 – 70kN
82 – 120kN
83 – 1-1/4 Post
2.
70, 81 or 82
Total number of
Weathersheds
0, 1 or 2
Number of large
weathersheds
(Alternating)
For 31mm/kV creepage
Insulators – first two
Digits indicate number
of large dia. w/sheds
0
3.
0 – No SDD < 66kV
2 – SDD > 66kV
4 – Steel fittings for
Post Insulators
6 – Twin SDD
Suffix on insulator codes
indicates type of rubber
used for weather sheds
Blank - ESP
W – Silicon
2
4. (40/70kN)
1 – Socket/Ball 16mm
2 – Clevis/Tongue
3 – Clevis/Tongue-Twisted
82 = (120kN)
1 – Socket/Ball 20mm
3 – Y Clevis/Tongue
4 – Socket/Ball 16mm
8 – Clevis/Tongue in-line
9 – T-Top Long
0 – T-Top Short
A – Clevis/Tongue 90 Deg
I – Ball/Socket 16mm
(reverse duty)
K – Y-Clevis/Tongue (in-line)
L – Tongue/Clevis
83 = Post Insulators
1 – 2 Hole Stress Base/F-Neck
4 – 2 Hole Stress Base/Clamp-Top
5 – 2 Hole Stress Base/2 Hole
Blade
6 – M20 Stress Base/F Neck
Page 21 of 45
GLASS DISC – COUPLED PERFORMANCE
Flashover and Withstand values on Insulator Strings, tested in accordance with SABS 177, B.S. 137 and I.E.C. 383.
U70 – 80 & 100 BL;U70CL & U120BS/20
All these insulators have a nominal connecting length of 146mm and a shell diameter of 254mm
Insulators
per string
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
Dry
Flashover
130
188
244
292
340
390
438
484
530
575
615
660
700
740
780
820
860
895
935
970
1 010
1 040
1 080
1 120
Power-frequency voltage
Wet
Withstand
Flashover
118
82
173
120
220
158
264
196
306
232
352
264
394
300
434
336
475
370
515
405
555
440
595
475
630
505
665
540
700
570
740
605
775
635
810
670
845
700
880
735
915
765
945
800
980
830
1 010
860
Withstand
72
107
144
180
214
248
282
316
346
380
410
440
470
500
530
560
585
615
640
670
700
730
755
785
Positive
Flashover
206
300
384
465
545
625
700
770
845
920
990
1 060
1 130
1 200
1 260
1 330
1 400
1 470
1 530
1 600
1 660
1 720
1 790
1 850
Impulse Voltage
Negative
Withstand
Flashover
194
220
286
316
368
402
450
490
525
570
605
650
680
735
750
815
820
890
890
965
960
1 040
1 030
1 110
1 100
1 190
1 170
1 260
1 230
1 340
1 300
1 410
1 360
1 480
1 430
1 560
1 490
1 630
1 560
1 710
1 620
1 780
1 680
1 850
1 740
1 920
1 810
1 990
Withstand
208
300
388
465
550
625
705
780
855
930
1 005
1 080
1 150
1 230
1 300
1 370
1 440
1 510
1 580
1 650
1 720
1 790
1 860
1 920
All the above values were determined at an altitude of 1 400 meters above sea level, at the South African Bureau of Standards
Laboratory – Pretoria and are given as Correct to Standard Atmospheric conditions (kV n.t.p.).
Generally, correction factors for air density and temperature are of the order of d – 0.85 @ 1 400m and d = 0.81 @ 1 800m.
Information, with regard to the co-ordination of insulation in South Africa may be found in SABS 0120 insulation Co-ordination”.
The values above 750kV R.M.S. and 1 800kV Impulse, were obtained by extrapolation, using the empirical formula U = U◦ xnУ
Page 22 of 45
COMPRESSION FITTINGS
Page 23 of 45
BIMETAL 4 CRIMPING TOOL
State of the Art – No Dies Required
Double Acting Hydraulic 4 way Indentation Compression Tool for use on Aluminium, Copper and Bimetal Compression Fittings for
Electrical Over-Head Transmission & Distribution Lines
Aluminium head rotates through 180 degrees
for ease of use, with Rapid closing, 9 pump action
Aluminium conductor sizes: Squirrel, Fox, Rabbit, Mink, Hare and Hornet
Copper conductor sizes: 16, 25, 35, 50, 70, 95, 120, 150, 185mm²
Fitting Sizes: 10mm – 33mm out-side diameter
Bimetal Copper & Aluminium Connectors
Round
Shaped
Oblong
C Connectors
Yellow Hot-Line (live line) handles, tested to 22kV
Total weight: 4kg
Black Rubber Grips
Handle rotates for releasing jaws
2 YEAR GUARANTEE
Extra: Compression head can also be rubber lined for
380 volt live line work
Bimetal Crimper
Supplied in Steel carry case
Pressure Gauge
10, 500 PSI 700 Bar
for maintenance and
checking hydraulic
oil pressure
Type: High Spin 32
By Pass cartridge
for setting pressure
to be applied to
connectors
Quick Release
Page 24 of 45
DEFINITIONS
STATE OF THE ART
- The most up-to-date method of manufacture,
material and testing.
NO DIES REQUIRED
- The tool has a 4 way indention.
Nibs are always concentric, on fitting.
No loose dies to lose or replace.
DOUBLE ACTING
- These tools have a low and high pressure valve
to enable the tool to close rapidly on low pressure
and to exert high pressure at the nib face.
MATERIALS TO CRIMP
- Aluminium, Copper or Bimetal fittings,
manufactured to suit “Bimetal 4 E” system.
TYPES OF FITTINGS TO BE CRIMPED
- Round, shaped, oblong and C connectors –
Aluminium or Copper
APPLICATION IN TOOL
- The Bimetal 4 E system is designed with
locating grooves down the length of
the fitting to enable the operator to align
the tool head.
YELLOW HOT-LINE HANDLES
- These handles are made of fibre glass
and tested to 40kV DC. The crimping head
may also be insulated with rubber.
PRESSURE (OPERATING)
- All tools operate at 10, 500 PSI or 700 bar. or 64 kPA.
and can be checked by means of a pressure gauge.
OIL
- All tolls use hydraulic oil high spin 32.
BY PASS CARTRIDGE
- The method of setting the pressure is unique and carries
a worldwide patent. Situated externally for easy access.
CARRY CASE
- All tools are supplied in a steel carry case for extra
protection and safe keeping.
Page 25 of 45
FITTINGS FOR BIMETAL 4 E SYSTEM
1)
All raw material is checked for hardness, elongation, malibility before any fittings are manufactured.
2)
All fittings are locally made with 100% local content.
3)
All fittings are de-oxidized and cleaned before being dispatched, to remove an oxidation in and outside the tube.
4)
All fittings are marked as follows:
a)
b)
c)
5)
Manufactures name-CCL
Type of material
- Aluminium
- Copper
- Bimetal
Fitting type
- Non tension joint
- Tension joint
- Angle tap connector
- Tee tap connector
- Lugs (1 hole lugs)
- Jumper terminal (2 hole lugs)
- Tee flag connector
- Repair sleeve
- C Connector
- Bi-metal lugs & Ferrols
- Dead ends
d)
All fittings are designed exclusively to fit and operate the “Bimetal 4” Compression system. With the
following sizesRange of Conductors
0 = Squirrel
4,0-7,0
1 = Fox
6,0-8,5
2 = Mink/ Pine
8,0-11,3
3 = Hare/ Oak
10,0-14,00
4 = Hornet
12,0-16,00
e)
f)
Size of tap connector
What tooling to be used and where to crimp
All fittings have a manufacturers code build-up from the above description. i.e.: VCAT 1.2 (code 1022)
Aluminium
1
6)
tension joint
02
for mink
2
All fittings are pre-greased with 159 grit grease before being capped and packed in see-through plastic packages,
hermetically sealed to prevent air and moisture gaining access to the fittings.
Page 26 of 45
APPLICATION OF CONNECTOR ON CONDUCTOR
Check list
1)
Hydraulic tool (No leaks, in good working order)
2) Fitting (Size is correct)
3) Conductor size
4) Wire brush
5) Grit grease 159 G
6) Cable cutter
1)
The conductor should first be cut off square and clean, then straightened by hand (no hammer etc.) as all
conductors have a curve built-in, due to it being placed on a drum. Should you not straighten the conductor it will
lead to this curving (bananing) when crimped.
To make a perfect joint
CUT the conductor leaving a clean square end.
2)
Now clean the area where the fitting is to be attached by means of the wire brush, even if the conductor is new,
it will already have oxidized and it is for this reason that the grease is applied, to prevent oxidation. Apply grit
grease after cleaning.
CLEAN the conductor
3)
Select compression fitting, remove from packaging and remove plastic caps insert conductor, and revolve fitting
to apply grit grease to both surfaces.
PUSH the conductor fully into the connector and
revolve fitting.
REVOLVE FITTING
4)
Now follow instruction on fitting with regard to crimping procedure and how many crimps. (Crimp between lines)
all fittings which are required to join two conductors in line will have a center stop, so that the operator will not
over crimp one and under crimp the other. CCL fittings are crimped in the middle for this purpose and to act as
a guide as to how deep the indent should be, if a conductor is inserted and crimped. Should the conductor be
able to pass through the indents, the conductor diameter is in fact too small for that particular fitting.
Page 27 of 45
OPERATING “BIMETAL 4 E” HYDRAULIC TOOL
1)
Remove tool from case checking there is no oil leaking in the case (if oil is present check pressure with gauge).
2)
Hold unit in both hands, and pump handle 9 times, at this stage all 4 nibs should be touching each other, release
pressure by rotating pump handle anti clockwise and closing handles together, this action will engage the release
mechanism at the base of the handle and the 4 nibs will open. “Repeat twice”
3)
Now we are ready to exert high pressure on the tool with all the operating parts and “O rings” lubricated.
4)
Pump unit to close nibs (9 pumps) pressure will automatically change over to high pressure with a high pitched sound,
now 2½-3 pumps should enact by-pass valve and the pressure will fall away, should the tool not reach by-pass stage,
do not crimp any fittings as they will be under crimped. If in fact the tool takes 4-6 pumps to by-pass it will over
crimp.
5)
All tools should be checked by an appointed representative (i.e. safety office) every six months for oil leakages and
general tightening up (Screws etc.) All tools must be serviced every 12 months. (Oil changed and pressure set) by
the supplier.
6)
Danger: Do not engage in repairs and services without first-hand knowledge of hydraulic tools as this could lead to
a very expensive repair at a later stage.
7)
Placing the fitting in the tool pump handles until the fittings is firmly held in place, making sure that the fitting is
held by all 4 nibs and that the fitting has not slipped between two nibs.
8)
On all joints, crimp from the outside towards the middle-stop, making sure you do not crimp that extreme ends.
9)
Remove cap and insert or apply fitting to conductor (after cleaning and straightening) now pump handles until tool
by-passes, you will first feel resistance to your pressure applied and at by-pass, no resistance to you pumping the
handles together. Move tool to next set of marks and repeat operation, until all demarcations have been crimped.
10) If you have not straightened your conductor before you crimp it, and it does banana, do not try to straighten it by
hitting it with a hammer, or the like, leave it alone. You will only do more harm than good.
11)
Always make sure that the opening of the fitting throat faces out of the crimping head towards the line so that the
line can enter straight in.
Open throat connectors
All OPEN THROAT connectors are located in the tool head as shown in
the adjacent illustration. The tool nibs are advanced to lightly grip the
connector profile at the position where the first crimp is to be made.
Subsequent compressions are made by sliding the tool head along the
connector.
12) The “Bimetal 4 E” Hydraulic tool has been designed exclusively for overhead line fittings, to let it help you take a
rest when up the ladder. Hang the tool on the conductor over the fitting when resting.
13)
After completing crimping your compression fitting onto the line “Do not drop” the tool onto the ground, but let
it down slowly or carry it down the step ladder.
14)
Always replace the crimping tool in the steel carry case after use.
Training courses for the correct operation of the tools as well as installation procedure of Crimp Fittings can be
arranged either on site or at our offices. Please liaise with your sales representative to schedule this training.
Page 28 of 45
ISOLATING SWITCHES
The Isolating Switches as detailed in this catalogue are designed for use in sub-station and distribution lines and
categorised as either outdoor 3 phase rocking type and single phase isolators or three phase centre rotating double side
break isolating switches.
1.
OUTDOOR THREE PHASE ROCKING TYPE AND SINGLE PHASE ISOLATORS
The following switches are manufactured in accordance with IEC 60265-1 and are used in the voltage ranges 11, 22
and 33kV. For each voltage range manufactured we are able to supply a switch with a current rating of 400A up to
1200A depending on the customer’s requirements. The short time (3 second) current ratings for these switches
are as follows: 13kA up to 600A & 7.5KA for 800A & 1200A.
These switches can be mounted either horizontally or vertically and are normally supplied with manual insulated
operating mechanisms. Motorised or spring operating mechanisms are available on request.
The main characteristics and components of these switches are as follows:
Current Carrying Components
Contacts
Manufactured from high conductivity copper. Fixed contacts are spring backed to ensure high contact pressure.
Surfaces on both fixed and moving contacts are nickel plated. (Silver plating is an optional extra up to 600A and
standard for 800 and 1200A).
Current Transfer
Current paths with flexible cables which carry current from the fixed insulator (load end) to the tilting centre
insulator are supported within a mild steel pantograph.
Main Terminals (connector pads)
Comprise copper pads for acceptance of conductors as specified. The complete assembly is nickel or silver plated
depending on the current rating.
Saddle type clamps are provided as standard up to 600A. For 800A and 1200A, pads are drilled to accept
compression or bolted type terminals (optional extra).
Arcing Contact
The main moving contact (isolator blade) incorporates an arcing tip which serves to protect the main contacts from
burning on closing the isolator, i.e. the arcing contacts close before the main contacts are engaged. The arcing
contacts do not carry current when the isolator is fully closed.
Hinge
The centre tilting insulator assembly hinge which is designed to run dry for long periods of maintenance free
operation, comprises non-ferrous bearing points and galvanised ferrous surrounds.
Base
Each phase base is manufactured from mild steel channel which is hot dip galvanised to ISO 1461 after fabrication.
Mounting holes to suit standard mounting arrangements are provided.
Operation Mechanism
An operating handle of the reciprocating type is supplied. Adjustment of the vertical connecting pipe is easily
accomplished by means of a turnbuckle.
Facilities exist for padlocking the isolator either in the open or closed position. Interlocks can be fitted.
The vertical rod between the operating mechanism and the isolator inter phase operating tube is supplied in suitable
lengths to facilitate installation, with insulating insert.
Installation Instructions
See the technical section for the installation and operating instruction.
Page 29 of 45
Optional Extras
- Flicker arc horns for interrupting small load currents.
- Arc interrupter heads for interrupting full load current.
- Compression and bolted connectors
- Auxiliary contacts.
2.
-
Silver plated contacts.
Earth switch.
Interlocks
3 PHASE CENTRE ROTATING DOUBLE SIDE BREAK ISOLATING SWITCHES
A range of centre rotating switches is manufactured from 11 – 66kV. These switches can be supplied with a current
rating up to 1600A. The short time (3 seconds) current rating for these switches is 25kA.
These switches are mounted horizontally and are normally supplied with manual operating mechanisms. Motorised
operating mechanisms are available on request.
The main components of these switches are as follows:
Current Carrying Components
Contacts
Manufactured from high conductivity copper. Contacts are spring backed to ensure high contact pressure. Contact
surfaces on both fixed and moving portions are nickel plated. (Silver plating is an optional extra up to 600A and
standard for 800 and 1200A).
Main Terminals (connector pads)
Comprise copper pads for acceptance of conductors as specified. The complete assembly is nickel or silver plated
depending on the current rating.
All pads are drilled to accept compression or bolted type terminals (optional extra).
Base
Each phase base is manufactured from mild steel channel which is hot dip galvanised to ISO 1461 after fabrication.
Mounting holes to suit standard mounting arrangements are provided.
Operation Mechanism
An operating handle of the rotational type is supplied. Adjustment of the vertical connecting pipe is easily
accomplished by means of a turnbuckle.
Facilities exist for padlocking the isolator either in the open or closed position. Interlocks can be fitted.
The vertical rod between the operating mechanism and the isolator inter phase operating tube is supplied in suitable
lengths to facilitate installation.
Installation Instructions
See the technical section for the installation and operating instruction.
3.
GENERAL
Metal Treatment
All ferrous components are hot dip galvanised to ISO 1461. Current carrying non-ferrous components are nickel
plated, alternatively silver plated where applicable.
Type Designation
A metal nameplate detailing the isolator type and rating is affixed to each isolator base.
Packing
Each isolator is suitably packed in wooden crates to protect against damage during transport and storage.
Type Test
To substantiate ratings, type test reports are available on request.
Page 30 of 45
FORMULAS AND EQUATIONS
3-Phase Formula
1.
Voltage drop
= 1.72 x 1 x R
Where 1
= Line current per phase
R
= Resistance of one core only
NB: For large 3-core cables carrying high alternating currents, the
increased AC resistance due to skin effect must be allowed for.
2.
kW
kW
=
=
kW
=
Horse Power x 746
1 000 x Efficiency
kVA
=
kW
Power Factor θ
kVA
=
Line Amps x Line Volts x 1.732
1 000
kVA
=
Horse Power x 746
1 000 x Efficiency x Power Factor
Line Amps
=
kW x 1 000
Line Volts x 1.72 x Power Factor
Line Amps
=
kVA x 1 000
Line Volts x 1.732
Line Amps
=
kW x 1 000
Line Volts x 172 x Power Factor x Efficiency
3.
4.
kW = KiloWatt
kVA x Power Factor
Line Amps x Line Volts x 1.73 x Power Factor
1 000
kVA = KiloVolt Amps
Power Factor = Cos θ
Physical Constants
Acceleration of gravity
Atmospheric pressure
Avogadro’s number
British thermal unit
Curie
Faraday
Gas Constant (air)
Gram-calorie
Gram-mole of gas
Planck’s constant
Velocity of light
=
=
=
=
=
=
=
=
=
=
=
=
=
=
32.2ft/sec²
9.8m/sec²
14.7psi
760mm Hg = 101.3 kilopascal
6.024 x 1023/gm mol
1 054.8 joules
3.7 x 1010 disintegrations/sec
9.65 x 104 coulombs
8.32 x 107 ergs/°C gm mol
4.19 joules
22.4 litres @ 0°C and 1 atm
24.45 litres @ 25°C and 1 atm
6.626 x 10-27 erg sec
2.9978 x 1010cm/sec
Page 31 of 45
Geometric Formula
Circle
Sphere
C = πD
S = 4πr²
A = πr²
V = (4/3) πr³
Trigonometric Functions
sin A
=
a/c
cos A
=
b/c
tan A
=
a/b
cot A
=
b/a
Mechanics
F
F1d1
v
s
v²
KE
PE
p
F
W
Gas Law
PV
=
=
=
=
=
=
=
=
=
=
B
c
A
a
b
C
µN
F2d2
vo + at
vot + (at²)/2
v0² + 2as
(mv²)/2
mgh = (kx²)/2
mv
ma
mg
=
TWA’s
TWA
=
[T1C1 + T2C2 +… + TnCn]/Ttotal
Electricity
E
P
Rseries
1/Rparrallel
=
=
=
=
IR
EI
R1 + R2 + … + Rn
1R1 + 1/R2 + … + 1/Rn
Ventilation
Q
V
V
TP
=
=
=
=
AV
4005 (VP)¹ ²
4005Ce (SPh)¹ ²
SP + VP
Radiation
S=6CE
I2
=
I1 x [(d1)²/(d2)²]
Noise
LI
Lp
T
=
=
=
10 log (I/I0) dB
20 log (p/p0) dB
8/ (2[L-90)/5])
Heat Stress
WBGT
=
WBGT
=
nRT
0.7WB + 0.3 GT
0.7WB + 0.2 GT + 0.1 DB
Unit Conversions
Temperature
tk
=
tc
=
tc + 273.16
(tf – 32)/1.8
Density of Water
1gm/cm³
=
1.94 slugs/ft³
(weight density = 62.4lbs/ft³)
Radiation
1 Curie
1 Rad
1 Rem
=
=
=
3.7 x 1010 Becquerel
10-2 Gray
10-2 Sievert
Angles
1 radian
=
180°/π
Concentrations of Vapours and Gases
ppm
=
mg/m³ x 24.45/MW
Light
1 lumen
1 footcandle
=
=
=
Magnetic Fields
1 Teasla
=
1 candela
10.76 candela/m²
10.76 lux
10, 000 Gauss
Page 32 of 45
CONVERSION FACTORS
Great care must be exercised in the use of units as the application of incompatible units probably constitutes the major
cause of errors in calculation. This section gives some conversion factors to facilitate the expression of units on a
common correct base.
Use of the International Standard (SI) units has become mandatory in the R.S.A. in terms of the Measuring Units and
National Measuring Standards Act No. 76 of 1973 from the 5th of July 1974 as noted in Government Gazette No. 4326.
This system must, therefore, be adhered to on all drawings, specifications, enquiries, contracts and orders.
The SI units consist of:
Base Units
Quality
Length
Mass
Time
Electric current
Temperature
Amount of substance
Luminous intensity
Supplementary Units
Quality
Plane angle
Solid angle
a.)
b.)
c.)
Base units
Supplementary units
Derived units
Name
metre
kilogram
second
ampere
kelvin
mole
candela
Symbol
m
kg
s
A
K
mol.
cd
Name
radian
steradian
Symbol
rad
sr
Delivered Units
Some of the relevant derived units are:
Quality
Name
Symbol
Capacitance
Conductance,
Admittance,
Susceptance
Electric charge
Electric resistance,
Impedance,
Reactance
Electric potential
Force
Frequency
Inductance
Magnetic flux
Magnetic induction
Power
Pressure, stress
Work, energy
Area
Density
Kinematic viscosity
Second moment of area
Speed
Volume
Dynamic viscosity
Torque
Permeability
Permittivity
Resistivity
farad
F
Expressed in terms of
SI Units
C/V
Siemens
S
A/V
coulomb
C
A.s
ohm
Ω
V/A
Volt
newton
hertz
henry
weber
tesla
watt
pascal
joule
Pascal second
-
V
N
Hz
H
Wb
T
W
Pa
J
m²
Kg/m³
m²/s
m4
m/s
m³
Pa.s
N.m
H/m
F/m
Ωm
W/A
kgm/s²
S-1
Wb/A
V.s
Wb/m²
J/S
N/m²
N.m.
m²
Kg/m³
m²/s
m4
m/s
m³
Pa.s
N.m
H/m
F/m
Ωm
Page 33 of 45
Specific heat
Thermal conductivity
-
J/kgK
W/mk
J/kgK
W/mk
Page 34 of 45
Conversion Factors
Multiply by
To convert from
to
to
to convert from
Multiply by
Multiply by
To convert from
to
(i) Area
to
to convert from
Multiply by
(v) Force
0,155
0,00155
10,7639
43560
sq. inches
sq. inches
sq. feet
sq. feet
sq. centimetres
sq. millimetres
sq. metres
acres
6,4516
645,16
0,0929
0,00002296
0,40469
0,0001
1,196
0,00197
hectare
hectare
sq. yard
circular mil
acres
sq. metres
sq. metres
µm²
2,471
10 000
0,83613
506.707
0,7376
8,8507
0,102
0,102
1000
(ii) Bending Moment
100000
0,102
0,102
0,2248
Dyne
Kilogram force
Kilopond
Pound force
Newton
Newton
Newton
Newton
0,00001
9,807
9,807
4,448
Foot pounds
Inch pounds
Newton metres
Newton metres
1, 3558
0,113
Kilogram metres
Kilopond metres
Newton mm
Newton metres
Newton metres
Newton metres
9,807
9,807
0,001
(vi) Torque
0,7376
pounds feet
newton metre
1,3558
8,851
0,102
0,102
1000
pounds inch
kilogram metre
kilopond metre
newton millimeter
newton metre
newton metre
newton metre
newton metre
0,113
9,807
9,807
0,001
0,3937
39,37
inches
inches
centimetres
metres
2,54
0,0254
16,018
27,679
0,03937
3,2808
0,62137
1 x 107
inches
feet
miles
angstrom unit
millimetres
metres
kilometres
millimetres
25,4
0,3048
1,60934
1 x 10-7
1000
1 x 106
39,37
39,37
1,0936
micron
millimicron
thou
mil
yards
millimetres
millimetres
millimetres
millimetres
metres
0,001
1 x 10-6
0,0254
0,0254
0,9144
grams
grams
kilograms
metric tonnes
short ton
long ton
kilograms
grams
28,349
31,103
0,45359
0,0004536
0,0005
0,0004464
1000,0
0,0648
(iii) Density
0,06243
0,036128
pounds/cu.ft.
pounds/cu.inch
kilogram/cu.metre
grams/cu.cm.
(iv.) Energy, Power
1,341
56,879
3,4129
Horsepower
BTU/min
BTU
kilawatts
kilowatts
Watt-hrs
0,7457
0,01758
0,2930
0,9863
0,000948
1,0
0,948
0,2387
0,102
0,2778
Horsepower
BTU
watt seconds
BTU
calories
kg metre
kilowatt hour
metric horsepower
joules
joules
kilojoules
joules
joules
mega joules
1,0139
1054,6
1,0
1,0546
4,19
9,807
3,6
(vii) Length
(viii) Mass
0,035275
0,03215
2,20462
2204,62
2000,0
2240,0
0,001
15,432
ounces (av)
ounces (troy)
pounds
pounds
pounds
pounds
metric tonnes
grains
Page 35 of 45
Conversion Factors Continue
Multiply by
To convert from
to
to
to convert from
Multiply by
SI Prefixes and Symbols for Multiples and Submultiples of SI Units
(ix) Pressure
2,242
1
0,06805
0,96784
14,2233
0,01
10,0
0,0075
0,102
0,145
0,001
cm. mercury
atmospheres (metric)
atmospheres (std)
atmospheres (std)
pounds/sq.inch
bars
bars
mm. mercury
mm.water
pounds/sq. inch
newtons/sq.mm
ft. water
kg/sq.cm.
pounds/sq. inch
kg/sq.cm.
kg/sq.cm.
kilopascals
newtons/sq.mm.
pascals
pascals
kilopascals
kilopascals
0,4461
1
14,6959
1,03323
0,0703
100
0,1
133,322
9,8064
6,8948
1000
(x) Volume
0,061
0,0353
35,3145
0,2642
0,22
0,00176
1,7598
cubic inches
cubic feet
cubic feet
gallon (U.S.)
gallon (imp.)
pint
pint
millitres
litres
cubic metres
litres
litres
millilitres
litres
16,387
28,31
0,02832
3,7853
4,5456
568,261
0,5683
Numerical Factor
1012
109
106
103
102
10
10-1
10-2
10-3
10-6
Verbal Factor
Billion
Millard
Million
Thousand
Hundred
Ten
Tenth
Hundredth
Thousandth
Millionth
SI Prefix
tera
giga
mega
kilo
hecto
deca
deci
centi
milli
micro
SI Symbol
T
G
M
k
h
da
d
c
m
µ
10-9
10-12
10-15
10-18
Milliardth
Billionth
Billiardth
Trillionth
nano
pico
femto
atto
n
p
f
a
Page 36 of 45
INSTRUCTIONS FOR ERECTION AND MAINTENANCE OF
3 PHASE CENTRE ROTATING, OUTDOOR TYPE ISOLATOR
Page 37 of 45
List of Components – HK Isolators
Description
1.
Quantities
Hand Operating Mechanism………………………………………………………………………………………………………………………………………………………………. 1
NB.: The box may contain an auxiliary switch and/or captive key lock(s).
2.
Vertical Coupling Pipe…………………………………………………………………………………………………………………………………………………………………………. 1
3.
Phase Channel Bases……………………………………………………………………………………………………………………………………………………………………………. 3
4.
Turntables…………………………………………………………………………………………………………………………………………………………………………………………….. 3
5.
Insulator Support Spacers…………………………………………………………………………………………………………………………………………….6 (66kV – 24)
6.
Insulators………………………………………………………………………………………………………………………………………………………………………………………………. 9
7.
Fixed Contact/Terminal Pads……………………………………………………………………………………………………………………………………………………………..6
8.
Moving Contact/Double Blades…………………………………………………………………………………………………………………………………………………………..3
9.
Bearing Support Plate…………………………………………………………………………………………………………………………………………………………………………..1
10.
Coupling Assembly and Drive Rod……………………………………………………………………………………………………………………………………………………… 1
11.
Inter-phase Coupling Rods………………………………………………………………………………………………………………………………………………………………….2
12.
Centre Pivot Assembly………………………………………………………………………………………………………………………………………………………………………… 1
NB.: Due to development modifications, the details may vary slightly from the drawing.
Unpacking
The isolators are packed in sub-assemblies, one complete isolator per skeleton crate. The 3-phase sub-assemblies
consist of Items 3, 5, 6, 7 and 8, mounted on their phase channel bases (3). In addition items 1, 2, 9, 10 and 12 are
strapped to the side of the crate.
Inspect and check the existence of all the above parts and advise supplier immediately of any shortages or damage (see
addendum for any additional optional parts).
Installation
1.
The contact pressure is factory set. Open moving contacts and close again until contacts just touch. Check that
the fixed contact blade is positioned in the centre of the two moving contact blades. If not satisfactory, slacken
off M8 screw with spring nearest to the centre insulator. Adjust blades up or down to suit and re-tighten the M8
screw.
2.
Mount and align each phase sub-assembly in position on the structure (supplied separately or by others) at the
phase centres indicated on the drawing and secure.
3.
Position the hand operating mechanism (1) on the structure.
4.
Position the bearing support plate (9) on the structure.
5.
With the isolator phases in the closed position, fit the inter-phase coupling rods (11) between the centre phase
centre pivot assembly (12) and the outer phases turntable levers (4). Adjust their length to ensure simultaneous
opening and closing of all 3 phases.
Page 38 of 45
6.
Fit the vertical coupling pipe (2) in position through the bearing.
7.
Fit the coupling assembly and drive rod (10) between the coupling pipe crank and centre phase lever.
8.
With the phase contacts closed and the hand operating mechanism (1) in the CLOSED position, couple the vertical
coupling pipe (2) to the hand operating mechanism (1) by means of the M10 set screw and lock in position.
9.
Operate the switch and check that the contacts are fully closed with the handle in the fully CLOSED position. If
necessary, adjust by slackening the u-bolts on the drive rod (10), adjust length and re-tighten the u-bolts.
10.
Open and close isolator a number of times to ensure smooth and correct operation.
11.
After the conductors have been secured to the terminal pads, check contact alignment.
12.
All contacts will have been cleaned and greased before despatch. Only if necessary, clean contact surfaces and
apply recommended contact paste.
13.
Check any secondary wiring, terminals and fixing screws for tightness.
14.
Note spaces, item 13 to mount items 1 and 9 to the structure as supplied as standard 76 x 38 channel.
Maintenance
These isolators require very little maintenance. However, it is recommended, dependant upon the environmental
conditions, to attend to the following, once in 3 to 5 years.
1.
Grease all bearing points via nipples provided.
2.
Clean main contacts with transformer oil and recoat with recommended contact paste.
3.
Operate isolator several times to check smooth operation and operation of auxiliary contacts.
settings if found to be necessary.
Only re-adjust
Page 39 of 45
INSULATORS
Polymer Insulators
Elbroc polymer insulators have been ergonomically designed and shaped to make use of the environment and its
changing conditions to create insulators that are:
Self washing
Light weight
Easy to use
There are more of this design of composite insulators in service than all other makes combined.
Elbroc polymer insulators were first installed in SA on a 132kV line in the Nelspruit area in 1979. Some of these were
subsequently taken down for examination and testing, and were found to be in perfect working order. Random checking
over the years has confirmed the reliability of Elbroc polymer insulators.
This reliability helps you to satisfy your customer’s need for uninterrupted power supply.
Field use has proved that Elbroc composite insulators are the cost effective, high performance solution to the ongoing
maintenance and construction problems encountered in the distribution of power.
Elbroc polymer insulators, which are marketed under the trade name “Thiel-Lite”, are manufactured under licence to the
world-renown Ohio Brass Company of America who are leaders in polymer technology. Our licence agreement ensures
that all new product developments are immediately incorporated into the local product.
Our manufacturing and marketing policy includes a quality assurance programme that is in accordance with our listing in
terms of SABS ISO 9001 code of practice, ensuring that our products conform to the high standards demanded by the
industry we serve.
More than 500 000 units sold in the first 14 years.
Basic Construction
The
1.
2.
3.
insulators consist of three basic components:
Weathersheds
Fibreglass rod
Metal end-fittings
The weathersheds are assembled over the fibreglass rod, the centre hole in the weathersheds being smaller than the
rod to ensure a tight fit. The inner surface of the weathersheds hole forms two O-rings per centimetre and the
reservoirs between these O-rings are filled with a special silicone grease to produce a continuous, permanent “living”
seal.
The end fittings are attached by crimping them to the fibreglass rod.
When assembled, the end-fittings maintain the entire stack of weathersheds under axial compression, which
adequately compensates for the slight elongation of the fibreglass rod under tension or when temperature changes
occur.
A wide range of products for 11 to 765kV are available to fit all existing hardware. Applications stretch from the subzero temperatures of Alaska to the harsh UV conditions of the Namibian desert.
Page 40 of 45
Local manufacture gives you:
•
Custom design. We manufacture to your needs (all configurations from 11 to 20mm socket/ball and clevis/tongue).
•
Better deliveries because there are no long shipping times.
•
Superior local knowledge of polymer insulator design and construction.
•
Price flexibility.
•
Production flexibility.
•
Direct replacements for existing strings.
•
No change in ground clearances.
•
Reduced down time and fewer outages.
•
Less fault tracing.
•
Cheaper transportation.
•
Improved productivity.
•
No repetitive line inspections. Once a McWade insulator is installed you never need worry again. “Put it up and
leave it”.
•
Maintenance down time is costly. McWade polymer insulators help you save money.
Forged steel end-fittings
•
•
Superior quality
Consistent strength
Hot dip galvanized
•
•
Non-corrosive
Long lasting
•
•
•
•
•
•
•
Specially formulated silicone alloy material
Hydrophobicity of silicone
Strength and electrical superiority of EPDM
Surface water breaks up into droplets
Broken conductive pathways
Reduced leakage currents
Sediment forms on insulator, silicone molecules migrate through
sediment causing water film to break up into droplets and so break
conductive path
•
•
Allows for wind cleaning and water run-off
Suitable for vertical and horizontal installation
•
•
•
•
Silicone alloy weathersheds – no breakages
High mechanical strength
Absorbs impact
Flexible weathersheds combat vandalism
Compact design
•
Allows for increased creepage without increasing the coupling length
O-rings
•
•
Filled with silicone grease, forming a continuous seal along the insulator
Eliminates the risk of puncture
High strength fibreglass ring
•
•
•
Glass content exceeds 70 per cent
Continuous strands of fibre
As strong as 070M55 (En9) steel
Integral corona ring
•
•
Prevents corona on rubber surface
Insulators are RIV and corona free up to 161kV
Long rod style insulator
(class A type)
•
•
•
•
No metal between end-fittings
Longer creepage
Less chance of flashover
Puncture-proof
Weathersheds
Hydrophobicity
Pollution
Smooth aerodynamic profile
Vandalism
Page 41 of 45
HARDWARE
McWade Productions manufactures and supplies a comprehensive range of hardware fittings utilised in the make-up of
complete insulator string sets for both LV/HV transmission lines and substations up to an operational voltage of 800kV.
All forged steel hot dipped galvanised fittings are manufactured in compliance with IEC specification number IEC120.
The catalogued range of compression connectors provides for service and heavy duty “T” connections from Main Lines.
Connectors are available for COPPER ALUMINIUM and BI METAL interconnections between Main Line conductors and
branch cable. Live Line bails are included in the range, since these provide for disconnectable features at Overhead Line
section points, or any situation where live clamp tapping of the conductor is desirable.
The types of connector designs available ensure the complete requirements of HV and LV tapping are catered for with a
minimum number of “Range Taking” compressed with the “Bimetal 4” No Die Crimping Tool.
Accessory equipment such as:
•
Tensioning Machines
•
Lifting Apparatus
•
Hot Line Working Tools
•
Grounding/Earthing Equipment
•
Cover up equipment
•
Working Platforms
etc. are sourced from both local and internationally recognised suppliers.
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INSTALLATION AND OPERATING INSTRUCTIONS
OUTDOOR, RURAL PATTERN ROCKING LOAD BREAK TYPE ISOLATORS: 11, 22 & 33kV
List of Components
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On receipt of equipment compare components against the following checklist. Notify supplier immediately of shortages
or damage.
Description
Quantities
1.
Complete isolator as per drawing……………………………………………………………………………………………………………….. Three phases per unit
2.
Interphase coupling tube – 38mm square tube…………………………………………………………………………………………………………………. 1 length
3.
Vertical operating rods: 20mm bore pipe x 2m lengths……………………………………………………………………………………………….. 3 lengths
4.
Operating lever assembly…………………………………………………………………………………………………………………………………………………………………… 1
5.
Operating rod insulating insert…………………………………………………………………………………………………………………………………………………………. 1
6.
Reciprocating operating handle assembly……………………………………………………………………………………………………………………………………….. 1
7.
Flexible earthing strap……………………………………………………………………………………………………………………………………………………………………….. 1
8.
Rod Guides……………………………………………………………………………………………………………………………………………………………………………………………….1
Note:
In cases where arc chutes have been removed for transportation, refit one to each
Phase as described under load break units.
Installation
Each isolator is factory aligned before dispatch, but to ensure years of trouble free operation, follow these instructions
carefully: 1.
Place individual phases in position on the mounting framework. In the case of 11kV and 22kV isolators, ensure that
the isolator pole fitted with adjustable hinge stops is mounted in the center phase position. This is important as the
open and closed positions for all three phases are set by this phase.
2.
Holding down bolts can be inserted, but not secured.
3.
Loosen U-bolts on center hinge assemblies on each phase – removal is not necessary.
4.
Position interphase coupling tube through square apertures in hinges, ensuring alignment with operating handle
position and/or equal overlap through outer phase hinges.
5.
Tighten U-bolts finger tight.
6.
Open isolator, i.e. separate the main moving contact and the fixed contacts by pulling upwards on the main contact
blade. All three contacts will open.
7.
Close slowly, letting the moving contacts rest in the fixed contacts. Do not close completely.
8.
Leaving the phase coupling tube free, align the three phase bases, and tighten the holding down bolts.
9.
Tighten U-bolts on all phases.
10. Close isolator until the center phase moving contact is parallel to the base. Adjust the appropriate stop if
necessary. Lock in position. At this point, ensure that the interrupter moving contact (Load break head, item 4) is
not making contact with the arc chute internal contacts. It should not be necessary to adjust the open position
stop.
11. Open the isolator slowly, checking that the arcing moving contacts have properly latched below the arc chute
contacts, and remain below them until the main moving contacts are well clear of their fixed contacts.
12. Close the isolator slowly, checking that the arcing contacts on all phases latch below the arc chute contacts and
once fully closed, do not touch them or the bottom of the arc chute. This setting is made by means of the eccentric
stop.
13. Clamp the operating lever in the desired position on the phase coupling tube.
14. Place the operating mechanism handle in position, screw up bolts finger tight.
15. Fit rod guide in position on the structure
16. Attach one length of vertical operating pipe to the operating mechanism turnbuckle. Fit insulating insert to
operating pipe.
17. Close operating mechanism.
18. Fit remaining operating rods, cutting top section to suit if necessary. Use pipe sockets and U-bolts on operating
lever to secure.
19. Align operating mechanism handle and tighten fixing bolts.
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20. With isolator in closed position and operating handle in the “ON” position, check that the center hinge is against the
closed stop.
21. Tighten the operating mechanism turnbuckle until the operating pipe is taut. Secure in position with lock nuts.
22. Check all fasteners for tightness.
23. By means of operating mechanism, open and close the isolator a number of times to ensure a positive action exists.
24. Secure the operating mechanism earthing strap to the mechanism mounting base.
25. Secure incoming and outgoing conductors as required.
Maintenance
•
•
At approximately 6-monthly intervals – particularly if the isolator has not been operated for an extended period,
the isolator should be opened and closed several times to “wipe” the contacting surfaces, verify that the operation
is correct, and ensure that the isolator and operating mechanism remain in good condition.
Every two years – or shorter intervals under adverse atmospheric conditions, remove the isolator from service and
perform the following operations: -
1.
2.
3.
4.
5.
Visually examine all contacts and replace damaged components if required.
Clean all contacts, removing all dirt and old grease. Regrease the main contact surfaces only – arcing contacts
should be left clean and dry.
Lubricate operating mechanism and isolator hinge points.
Clean the insulators.
Check alignment of contacts, following the procedure set out in items 10, 11 and 12 of the installation
procedure.
Load Break Units
When load break heads are fitted, these are pre-set before dispatch from the factory and should require no further
adjustment. However, it is possible that the settings could be upset as the result of knocks received during transportation
or unpacking. In this event, checks and adjustment should be carried out as follows after assembly of the three phases of
the isolator on its structure: -
•
•
•
•
•
•
Ensure that all cardboard separation pieces are removed from the arc chute slot.
If any of the stainless steel arcing blades have been bent, carefully straighten them by hand, or disassemble them
for repair.
Slip the blade into the arc chute, and using the M8 stainless steel setscrews supplied, fasten the arc chute to the
pre-assembled galvanized bracket, with one flat washer under the setscrew head, and the other underneath the
spring washer and nut, against the bracket.
Ensure that the blades are centred within 3mm of the centerline of the arc chutes as they enter the chamber.
With the isolator fully closed, ensure that the blades have properly latched below the chamber contacts, but do not
touch them or the bottom of the chamber. This setting is made by means of the eccentric blade stop.
Minor differences in the opening time of the three blades are permissible. If adjustment is necessary, slacken the
insulator to base mounting channel mounting bolts and set as required, ensuring that the main moving contact
remains centred between the main fixed contacts.
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