4) Contact surfaces finished with rough abrading have proven to have an appreciably lower contact resistance as compared to smoothly machined surfaces. Thus serrations can be made in the connector contact surface area can effectively increase the contact area particularly when splicing conductors.
5) In case of overlapping bolted joints current lines are generally distorted at the joints due to streamline effect. As a rule of thumb, the minimum overlap should be 8 to 10 times the bar thickness provided the current density in the contact surface does not exceed 1/3 or 1/4 of the current density in the bus bar cross section. At this value of overlap the current distortion is minimized and the current lines become parallel. If the current density is more, increasing the width of the contact surface will prove beneficial than increasing the length.
6) Cutting of slots in the bus bar can reduce the contact resistance to an extent of 30- 40 % of the contact resistance without slots. The sectioning of bus bars proves beneficial as it helps in uniform distribution of contact pressure under the bolt, which in turn will increase the contact area.
7) When two dissimilar metals are bolted and where the service temperature is expected to exceed 30 degree Celsius, Mechanical device such as a combination of Belleville washers (fig shown below) on top of a thick flat washers shall be used under the bolt head or nut to assure satisfactory mechanical and electrical integrity of bolted joints under current cycling and stress relaxation conditions. The Belleville washers have the ability to elastically absorb deformation caused by an outside load. To comply with space limitation imposed by the geometry of the bolted joint, the washers should be made as small as possible and from materials having high tensile strength and high elastic limit. Spring load characteristics is one of the most important characteristic of this hardware as it is a measure of the ability of the washer to elastically absorb deformation caused by an outside load and to compensate looseness developed as a result of thermal expansion. When these washers are used with bus bars, it is preferable to use two washers as this configuration enhances the joint elasticity and reduces the permanent deformation of the bars in the contact zone.
8. If use of Belleville washers, application of compounds or grinding of Aluminum surfaces to be avoided transition washers shall be used as it easily penetrates the Aluminum and copper oxides.
9. The clamping element should ensure contact with all the strands of the conductor.
10. If more than one clamping element is involved, the heads of all the clamping elements are placed on the same side of the connector to allow for easy installation.
11. The bolts shall be located as close to the conductor as possible to reduce the effective length of the moment arm which helps in minimizing the internal stress and thereby minimizing the stress corrosion.
12. One of the clamping elements should be captured so that it does not rotate during tightening.
1. Generally the mechanical connector components assure satisfactory degree of resilience, which minimize the stresses produced on the connection due to thermal variations.
2. These connectors can be installed with simple tools, which doesn’t require much of personnel training or high installation skill set.
3. As these connectors do not cause any deformation or damage of the conductors, can be easily uninstalled with the same tool used for installation and in many cases the same connectors can be reused.
1. The clamping force applied should assure low resistive electrical path between the joining conductors as well as the strength of the connection without damaging the conductors which is largely dependent on the installation personnel and which in many cases is questionable.
2. These types of connections involve periodic maintenance
3. Due to the asymmetrical geometry of these connections it is relatively difficult to insulate or tape them.
3 Hot line clamps:------------
Hot Line Clamps are used for connecting Bare Aluminum Conductors, Aluminum alloy Conductors, ACSR Conductors and Copper Conductors with or without armor rods The range of conductors we deal with are:
Helically formed Aluminum Armour rods on ASCR
• Helically formed Aluminum Armour rods on AAC/AAAC
• COPPER CLAD STEEL
• COPPER STRAND
• COPPER SOLID
• ALUMINUM CABLE.
• ALUMINUM CLAD STEEL.
Supreme has a range of Hot line clamps. They are also equipped to customize the clamp by using different combinations of compatible parts. Customers may kindly specify the main/ tap cable details and any special requirement that they may have. Supreme on receipt of such request will provide a suitable engineered design drawing for approval.
We provide two kinds of Hot Line clamps namely:
- Protected threaded clamps
- Bail Clamps (Stirrup Clamps).
- Protection of threads :
- Against Corrosion: The Eye screw threads are fully housed in an enclosure. This guarantees anticorrosion property as the enclosure is filled with a lubricant, which prevents corrosion.
- Against Arcing:
The arcing is primarily caused by the charging currents during the application and removal of the clamps on the hot line. The body of the clamp is designed in such a way it protects the threads from these charging currents and ensures protection against arcing.
2. Protection of Conductor:
Against Over heating and Heavy Surges
Better contact always assure improved conductivity, uniform current distribution which in turn avoids Overheating and heavy surges. Our range of Clamps guarantee good contact as the jaws of the clamps are engineered in such a way to make the maximum contact with the strands of the conductor.
Against Vibration Fatigue
The Clamp’s Jaws and the contact surfaces are designed to provide uniform distribution of stress and to avoid bending of conductors beyond the point which can cause damage.
3.Protection of Clamp:
Against Mechanical failure
The Mechanical reliability and durability of the clamp is assured through different Material and Mechanical testing in well equipped in-house testing labs as well as in the government approved laboratories.
The structure of Hot line clamps comprises of :
- Body and Keeper made out of Aluminum alloy
- Eye screw made out of Copper alloy or Aluminum alloy
- Tap Eyebolt made out of Suitable Copper alloy
- Spring Washer(s), if any, made out of Stainless Steel.
- Eyebolts made out of Copper alloy or Aluminum alloy or Eye nuts made out of Aluminum alloy.
- Bail made out of suitable Copper alloy.
For Tests, refer the testing section of our catalogue.
Auto mid span joints:
Automatic Mid-span Connector is a kind of full tension mechanical connectors. The principle on which these connectors work involves, use of tapered groove jaws inside the sleeve for the purpose of gripping the conductor when the tensile load is applied. As the conductor is pulled away from the sleeve, the jaws tend to clamp the conductor even more strongly. As more and more tensile load is applied to the conductor, the wedge action of the clamp also increases.
- Easy installation and moderate skill set required.
- Automatic connectors assure relatively good quality full tension connections.
This is not suitable for non-tension joints. Unless the tension does not exceed 15% of the rated braking strength of the conductor, they cannot function effectively. Hence these connectors would not be applicable for tap and other non tension applications.
Insulation piercing connectors provides connection between main and derived Cable by perforation of insulation. It is provided with piercing teeth of copper for high-conductivity connection. The teeth may be tin plated to limit bi-metallic reaction with Aluminum cores. Bolt is fully insulated with a Thermoplastic shear head and this provides safe live line working. Piercing of main and derived is simultaneous with one action. Piercing teeth and pierced cables are protected from water entry by in-built seals around the conductor teeth and if desired by a special grease filled end cap on conductor ends.
- Bolts shall be provided with a Thermoplastic shear head which functions as a torque-controlling device.
- A2 or A4 grade stainless Steel bolt or high strength galvanized steel bolts shall be used.
- Insulated jackets shall be specialized UV resistant fiber glass reinforced thermoplastic.
- The dielectric strength of the insulating material shall be 3/4/6 KV maximum when energized under water
- The installation of IPC requires tightening of the bolt with the basic wrench and as the Shear head is designed to break at the rated torque, the installation cost is greatly reduced and the problems that may arise due to Over torque or Under torque is eliminated.
- As the Connector’s teeth are designed to pierce the insulation of the conductor to make electrical contact and are pre-filled with an oxide inhibiting compound, the cost of stripping the conductor at the site and the cost of application of the oxide inhibitors are considerably reduced.
- The body of IPC is of insulated material, which avoids the use of tape or special insulation cover.
- As all the active parts of the cable and the connector are fully enclosed in an insulated enclosure and no contact of installation tools with any of the active parts is required installation without de-energizing the line is possible.
- IPC assures safety of the installation personnel as the connectors body is fully insulated to withstand 3/4/6 KV and the enclosures are regularly tested for protection degree ratings.
- Hook type Line tapping is not possible with IPC
- The use of IPC is limited to LV applications and MV applications, which involve only unscreened conductors.
- The use of IPC is restricted to non-tension applications