Thirty years ago, Hancock-Wood Electric Cooperative (HWEC), North Baltimore, Ohio, U.S., installed two submarine power cables in Lake Erie to connect Kelley's Island to the town of Lakeside, 3 miles (4.8 km) away on the Ohio shore. These three-phase, 1/0 submarine power cables were both 19,200-ft (5.85-km) long.

Lake Erie is approximately 30-ft (9-m) deep where the cables are submerged, and this area freezes solid during the winter. In addition to normal wear, years of dragging and shifting caused by ice and tidal movement had diminished the cables' reliability. HWEC feared that these water-damaged cables would soon become too unreliable and would be unable to meet the island's projected load growth. These factors made it necessary for HWEC to consider replacing or rejuvenating these cables.

In 1998, the estimated cost for replacing these cables was approximately US$4 million. But the cost to use UTILX Corp.'s CableCure/XL technology was only US$600,000. CableCure/XL technology would address both HWEC objectives: repair the water-damaged cables and rejuvenate the cables' water tree defects, allowing the cable to operate at its full design voltage.

CableCure/XL silicone-based restoration fluid is injected into electrical cables at a transformer or other termination point. It diffuses into the insulation, purges water and inhibits the growth of future water trees. It prolongs cable life by 20 years or more and increases dielectric strength. Maximum dielectric performance is reached 12 months to 24 months after treatment.

To perform the injection procedure, a vacuum is created on the cable, and pressure is used to push the fluid throughout its length. Unfortunately, the construction splices originally used to join the cables were not designed to handle the pressure necessary to effectively inject the silicone-based fluid.

To address this concern, UTILX designed a patented flow-through splice that met the mechanical and electrical requirements of this project. Prototypes of both the cable and the new splice were laboratory-tested. Tests showed that the cable could handle pressures close to 1000 psi and that the splice could handle pressures up to 800 psi before failing. It was determined, however, that a maximum pressure of 400 psi be used on this project.

Work began in October 1998. Divers located the cable splices in the two parallel circuits, approximately 1000 ft (305 m) apart, and marked their locations with buoys. Two barges were deployed to the location of the first splice to be replaced. Once the barges were in position and anchored, the first cable was de-energized. Divers located the first splice, lifted it off the lake bed and maneuvered it onto the crane's hook. The cable was then gently brought to the surface and draped across the barge.

A tent was placed over the splice being replaced, and every precaution was taken to keep this space dry. After the cable was secured, the old splice was cut out, and a flow test was performed to make sure that the cables were not blocked. With the successful completion of the flow test, the new flow-through splice was installed. The new splice was hand-wrapped (Fig. 1) and then encapsulated in an outer casing to keep water out.

The same procedure was then performed on the second cable. Both splices took approximately 27 hours to complete.

All three phases of the cable were injected simultaneously from the mainland to the island while the cable was in service. Nine and a half days later, the fluid completed its submarine journey and all three phases of the first cable were considered successfully injected. It then took another 11 days to complete the injection process on the second cable.

HTS System to Be Tested in Italy Pirelli Cables and Systems, ENEL and Edison (the MontEdison Group) have signed a four-year cooperation agreement for the development, production and testing of a high temperature superconducting (HTS) cable. The development program will include the first field trial of an industrialized HTS cable system in Italy. The partners will conduct a study relative to the commercial use of new systems based on HTS technology in the existing transmission networks. They also will evaluate the impact and benefits on those networks.

The three companies, all of which have experience in the field of super-conductivity research, will combine their capabilities to develop a 132-kV, three-phase HTS cable system. The cable will be able transport 3000 A continuously, more than double the load of a conventional system.

Pirelli will develop and manufacture a high performance, "cold dielectric" prototype cable. ENEL and Edison will contribute their systems expertise, operational know-how and facilities to evaluate the advantages and applicability of HTS cable technology in transmission and distribution networks. The new system will be subjected to prolonged electrical and mechanical tests in the CESI in Milan.

Ringing Out the Flashovers Over the years, Northeast Utilities, Hartford, Connecticut, U.S., has had flashing problems similar to those reported by other utilities when 25-kV loadbreak elbows would be pulled from their bushing inserts. When the utility started tracking the flashing problems, it found that the occurrences were more obvious during colder temperatures. The initial diagnosis was a normal loadbreak switching failure.

Papers given at an ICC meeting introduced Paschen's Law as a theory and possible cause of the problem. After further investigation, Northeast Utilities found tell-tale `tic' marks on the probe near the crimp connector threads, supporting this theory.

The utility considered several solutions to the flashing problem for the existing products that were installed in the field. One solution was to open the doors of the transformer and blow heat from a portable area heater into the cabinet around the cable and elbows for 20 minutes before trying to switch.

Another solution was to install a specially insulated elbow that makes the strike distance longer, and another solution involved cutting slots in the insert to relieve the vacuum. Both of these cases required an undesirable outage to change out the components.

Northeast Utilities finally decided to use the Safe-T-Ring device by Chardon Electrical Components, a Hubbell Power Systems company. The device can be installed on any bushing insert, junction, feedthru and insulating bushing already in the field. Using the Safe-T-Ringer Tool on the end of a hotstick, the Safe-T-Ring can be installed in seconds without taking an outage.

BPA Offers Electricity in a Box to Northwest U.S. The Bonneville Power Administration (BPA), Portland, Oregon, U.S., has signed a contract to purchase 110 fuel cells from Northwest Power Systems (NPS) of Bend, Oregon. If testing of the new technology is successful, the region will lead a high-tech revolution in the electric power industry.

"Our goal is to adapt clean, efficient fuel cell generators to small-scale consumers and commercial applications," said Jack Robertson, deputy administrator of BPA. "In just a few years, we could see these energy boxes distributed as widely as the home computer."

BPA will take delivery of the first proton exchange membrane (PEM) fuel cell systems this fall. Utilities in the northwest United States will test the 3-kW units for use in homes. After the first 10 "alpha" units are installed and operated, NPS will make any necessary adjustments and build 100 more "beta" test units, according to NPS president Alan Guggenheim.

BPA will work with local utilities to place the beta units in the homes of interested customers. Because trials of prototypes by BPA over the last two years were successful, the agency decided to move ahead with a full-scale test. "Although fuel cells will not replace large central generating plants, they can help meet load growth and provide clean, efficient electricity in homes," Robertson said. "Over time, the efficiency of these and other types of distributed generation will make them the choice of consumers."

The power units are 85% efficient when waste heat is recovered for space and water heating. Conventional generators are less than 35% efficient in the use of fuel. The cost of producing the beta units is about US$30,000 each, but Guggenheim expects that the price will drop to under US$10,000 per unit when they become commercially available in the year 2002.

Fuel cells produce electricity from natural gas and other fuels such as methanol, ethanol or propane. NPS has designed a processor that chemically removes hydrogen from the fuel. The proton exchange membrane then strips electrons from the hydrogen, thereby generating electricity. The process virtually eliminates the carbon monoxide, carbon dioxide and other harmful gases emitted by combustion engines.

Initially, the fuel cells are expected to be particularly useful in remote locations as backup generators, and in applications where reliable power is particularly important.

NYPA Installs Cathodic Protection System In 1991, the New York Power Authority (NYPA), New York, New York, U.S., completed a 26.3-mile (42.3-km), 345-kV underground and underwater transmission project from Westchester County to Long Island. A key part of the project was a self-contained, fluid-filled submarine cable installed in the Long Island Sound. The cable system consists of four independent cables: three energized phase cables and a spare. Each has a length of 7.9 miles (12.7 km). Prior to installation, the environment was considered to be potentially detrimental to cable life and performance. The cable manufacturer recommended that a thorough investigation be performed after the cable was installed to assess corrosion anomalies. Based on those investigations, NYPA determined that a cathodic protection system should be designed and implemented to ensure that the cable would be in service for at least the design life of 40 years.

The program included:

- A complete analytical evaluation of cable design, environmental conditions and potential galvanic and electrolytic corrosion processes. - Laboratory investigations performed on cable samples to understand the effect of electrolytic and galvanic corrosion and to determine minimum levels detrimental to cable components. - Stray dc current density measurements along the cable route to obtain time-varying magnitude and directional profile data. The results from the analytic and laboratory investigations determined that stray dc current densities in excess of 0.2 A/sq m could have a detrimental effect on the polyethylene semi-conductive layer. Carbon in the semi-conductive layer could be depleted, leading to voids and, in turn, causing water migration and damage to the copper return conductor.

Stray current measurements in the Long Island Sound identified areas where current magnitudes exceeded safe limits and also determined the direction of current flow. The time-varying stray dc current magnitudes were correlated with the dc electric railroad system load on Long Island, in Westchester County and in Connecticut.

An active cathodic protection system was designed to mitigate the effects from both galvanic and electrolytic corrosion. The system consists of multiple anode beds placed strategically along the cable route to provide maximum cable protection. Reference electrodes and current density sensors in the water provide feedback to a control system that automatically adjusts dc power to the anode beds based on stray dc magnitudes. A monitoring system will track protection system operation and performance. The system went online in June.