2020 BURNDY Master Catalog

Reference

Introduction Basic Electrical Connections Principles

Introduction - Basic Electrical Connection Principles (continued)

Clamp vs. Compression: In general, a compression connection can be expected to be more corrosion resistant than a clamp connection. The high pressures applied to a compression connector more effectively seal the contact against the penetration of moisture. The tubular sleeve of a compression connector has no side openings such as exist in clamp connectors between the clamping members. On the other hand, the clamp connector can be made more corrosion resistant if the conductor grooves conform more closely with the conductor contour. Thus a clamp connector made to accommodate a wide range of conductor sizes cannot be expected to be as corrosion resistant as one designed for one specific conductor size. Nevertheless, the differences in effectiveness of various designs can be minimized if a good contact compound is used.

spray fog with only minor corrosive pitting adjacent to the copper conductor, as seen in Figure 5. In addition, the aluminum conductor was completely protected, and the joint resistance remained virtually unchanged. The test involved a wide variety of sizes and types of connectors showing the effectiveness for small service connectors as well as large power connectors. Figure 6 shows a large all aluminum clamp type T connector installed on 3-1/2” diameter copper run and 750 kcmil aluminum tap. The figure shows this connector which was opened up after 1,400 hours of the salt spray test. Note that the contact surfaces are bright and clean and the only evidence is minor pitting along the faces adjacent to the copper. *It should be empasized that a good compound should be used on the contact surfaces whether aluminum or copper is used in an aluminum connector. Position of Conductor: A properly designed aluminum connector for joining aluminum to copper must provide adequate separation between the conductors to prevent electrolytic attack on the aluminum conductor. Even then, it is good practice to install the aluminum conductor above the copper conductor if possible. This will prevent pitting of the aluminum conductor due to copper salts being washed over the aluminum. Plated Aluminum Connectors: Plating has been used as a means to make an aluminum connector suitable for copper conductor. Such platings as copper, zinc, tin and cadmium have been used. The plating of aluminum is much more critical than plating a more noble metal such as copper. In addition, a preplate, usually of copper or brass, must be applied, thus introducing numerous metals and further possibilities for galvanic corrosion. To be effective in reducing galvanic corrosion between the copper conductor and the aluminum connector, the plated metal must be closer in the Electrolytic Series to copper than is aluminum. It must therefore, be cathodic to aluminum. Since porosity and minor scratches are always present, galvanic action can be expected in the presence of moisture, resulting in attack of the aluminum under the plating. Corrosion tests reveal attack in the form of a mottled appearance and flaking of the plating. In addition, the presence of plated metal can cause galvanic attack of the aluminum conductor, thus reducing the protection offered to this conductor in an aluminum connector. Cleaning and the Use of Compound: It should be emphasized that when aluminum connectors or conductors are involved, proper cleaning of the aluminum and the use of a good connector compound, such as BURNDY PENETROX™ A, are essential for trouble-free service. BURNDY, as well as other manufacturers, provide the contact grooves with a coating to make it unnecessary to clean the connectors, but in all cases the aluminum conductor should be cleaned by means such as scratch brushing, and immediately coated with the connector compound. To simplify the application of the compound, and to assure its use, almost all BURNDY aluminum connectors, except the large clamp type substation connectors, are supplied factory filled with PENETROX™ compound. For the tubular compression connectors, the tubular barrels are sufficiently filled with PENETROX™ and capped. For other types, the contact grooves are filled with PENETROX™ and enclosed in plastic packaging in a process called ‘stripsealing’.

Figure 5 Negligible Corrosion of Severe Salt Spray on Compression Connector Joining Aluminum to Copper.

Figure 6 Large Aluminum Bolted Connector Joining Copper Run to Aluminum Tap After Severe Salt Spray Test.

1-800-465-7051 (Canada) 1-603-647-5299 (International)

O-5