In recent years, Public Service Electric & Gas (PSE&G; Newark, New Jersey, U.S.) has installed an average of 1.5 million ft (457 km) of secondary cable per year. Several connection failures on the PSE&G underground secondary system spurred PSE&G engineers to look for alternative methods to taping connectors that would provide a waterproof seal and eliminate the corrosion that is the source of most failures.

PSE&G was averaging about 3000 secondary failures a year and more than US$2 million a year in repair costs for time and materials — nearly $700 per failure on average. Furthermore, the problem was almost always a connector failure. PSE&G connectors are hand taped, first with a mastic tape and then with a rubber or vinyl covering. No matter how well the taping is done, eventually water is going to make its way through the layers and cause corrosion and connection failure. The utility needed was a product or method that would totally seal the secondary.

Why Search for a New Technology?

PSE&G methodically tracks its underground primary failures: It knows when failures occur; why they fail; when and how repairs are made; and when the failed item is put back in service. Failures on the secondary system are too numerous to track in any organized way. PSE&G usually just locates the failure, does the repair and restores service, all without recording any data that could be later analyzed. However, with secondary failures increasing, the utility decided to try to understand failure history by studying trouble crew work orders for secondary system repairs over 12 months.

Considering Alternatives

In the search for a waterproof connector system, PSE&G considered using cold shrink tubing, heat shrink tubing and premolded connector covers. The heat shrink or cold shrink tube must be slid onto the cable before it is installed, which requires additional space in the manhole of a conventional underground system, or larger excavations in direct buried systems, to accomplish the installation of the tubing. For these reasons, PSE&G considered the Tyco Electronics' Raychem PowerGel brand products. After a thorough investigation of available methods and trials, PSE&G adopted the Raychem gel products for all repair and new connections. The gel completely envelopes the connector, eliminates water ingress and provides the waterproof connection the utility requires.

One problem PSE&G encountered was that it needed a product that would cover from No. 2 up to 750 mcm connections, and the wraparound gel cover was only rated up to 500 mcm. PSE&G discovered the manufacturer rating was based on aluminum cable and connectors. Since PSE&G was using 750 copper cable with copper connectors (which have smaller diameters relative to aluminum cables and connectors) the utility asked if the product use range could be extended. The products were tested and proved to meet the requirements of standard ANSI C119.1. Now one GelWrap provides protection for compression connectors from No. 2 to 750 copper, meaning the utility does not have to stock seven different GelWraps, it needs only one.

Field Crew Acceptance

A major consideration of adapting any new product or method is field crew acceptance. After trying the different methods, PSE&G field crews agreed working with the wraparound-type products was best. Because much of the utility's work is done energized, having a solution that is easy to install while wearing insulating gloves is important. The crews like working with the gel products because of the ease of installation compared to taping in tight spaces. As is evident in the manhole photos, the cables are typically in very close proximity to the wall and each other. Working on live secondary requires additional care and makes any installation more difficult. Reducing the number of times an installer has to place his hands into or around the cable bundle not only makes the job less difficult, but also safer. Streetlight crews also appreciate the ease of the push-on covers for the same reasons.

Use on the PSE&G System

The gel products PSE&G selected consist of the GILS splice kit, which has a straight mechanical connector in it; the GTAP Splice, a four-way tap connector; the GelCap-SL, a stub connection cover with connector for street light applications and the GelWrap, a wraparound splice cover that fits from No. 2 to 750 kcmil copper. The mechanical GTAPS connectors can be used with a conductor range from No. 14 to 2/0. The GILS kit can be used with a conductor range from No. 2 to 4/0.

Each gel-based product consists of an abrasion, UV and impact-resistant cover, which is pre-filled with gel or sealant. This sealant, called PowerGel, consists of chemically cross-linked silicone elastomer and silicone oil. It was specifically formulated for use with power cables and completely encapsulates the splice area to prevent corrosion. After making the connection, the installer simply wraps the cover around the connector and snaps it shut. The gel is displaced by the connector, completely filling all voids, providing a watertight, insulated seal.

The wide range of use of gel products has enabled PSE&G to reduce inventory of stocked connectors and covers. PSE&G now uses the Raychem gel products for most new and repair installations on the secondary system. This work is being done in coordination with a new insulated secondary bus designed so that the entire secondary system will be totally sealed. The secondary bus is made of copper with eight cable tails attached to it, to which PSE&G attaches its secondary cables. The secondary bus takes the place of a ring bus in the manhole. Once the compression connection to the cable tails is made, PSE&G seals and insulates it with the GelWrap. The goal is seal the entire secondary system. The bus is molded and sealed at the factory.

Previous connection methods worked for 10 to 15 years before the utility encountered problems. PSE&G is confident the GelWraps and bus will provide greater longevity. Through the use of its work management system, to date, PSE&G has had no failures of the GelWrap products except one that it attributed to improper installation. Undoubtedly, these gel products are the present and future at PSE&G.

In addition to use on the underground secondary system, the gel products are also being used to seal current limiters on the spot network system and on streetlight circuits. The current limiters are installed just as you would a splice in the cable. So, like a splice, you have to seal over the limiter.

Also, the gel products take less time to install than the previous taping method. It takes about 20 minutes to tape a secondary connection, whereas, it takes only about five minutes with the gel product. The product is an easier installation than taping in a crowded manhole, or in a trench application where the workers do not have to make a bigger trench. They just place the GelWrap around the connector and snap it shut. Obviously, this method is labor saving, but it is also cost saving. PSE&G anticipates cost savings of $125,000 a year, which will come mostly from cost avoidance. With the size and number of connections in secondary systems, failures are going to occur. The utility is convinced that replacing failed connectors with the gel product will result in higher reliability and lower costs — not a bad combination.

Timothy J. McLaughlin is a supervising engineer in technical and operational support with PSE&G. McLaughlin is the team lead in the electric underground area, where he handles the budget, develops work plans, supervises personnel and coordinates work. McLaughlin previously served as technical specialist, providing technical solutions for material/equipment problems in support of the operating divisions. He has developed technical standards and specifications for underground material and equipment, and has significant field experience in construction and maintenance of underground distribution systems. McLaughlin received the BS degree in business management from Thomas Edison State and a MA degree in organizational management from the University of Phoenix. He is a member of IEEE and a NEETRAC technical advisor. He also participates in EPRI-funded projects.
Timothy.McLaughlin@pseg.com