Management of new technology is always associated with multiple challenges. When faced with a dilemma of choosing between an existing proven technology and a nascent technology, the conservative recourse is to fall back on the former. For, such a choice will enable the deciding authority steer clear of embarrassing scenarios, should the choice of new technology misfire.

It requires courage and vision to plump for the latter even if the authorities strongly feel about the benefits of the new technology and have sufficient time at their disposal to experiment.

The process cannot be rushed through, especially when the application is meant for extremely critical areas or where huge financial outlay is involved. A case study from Germany will demonstrate this.

Tryst With History

In the year 1990, after the reunification of Germany, the power demand of Berlin — the capital of united Germany —- was steadily going up. Until then, the west and east parts of the transmission network of Berlin were operating in isolation and there was no interconnection available.

Drawing up a long-term plan for efficient management of the power network, the Berlin power utility BEWAG (now, Vattenfall Europe) decided to interconnect the west and east parts of Berlin city through a 400 kV underground cable link.

The route length was approximately 6.3 km. The cable had to be laid and safely secured without posing safety hazards to the public and causing least disturbance to the traffic.

BEWAG, therefore, decided to construct a large tunnel approximately 25 metres below the ground level and place two parallel cable circuits in this tunnel.

Testing the Technology

At that time, for the 400 kV application, paper-insulated, oil-filled cables were available. This was prone to failures and required maintenance. Cross-linked polyethylene cables born of a superior technology had been used and well proven in the networks but only up to 230 kV. There was no commercial installation of 400 kV XLPE cables in Europe. The German utility was left with an option to choose between an oil-filled cable and XLPE cable.

BEWAG decided to try 400 kV XLPE cable system, even though it had not been installed till then. But it took several meticulous steps to ensure dependability of the installation.

In 1993, BEWAG invited six cable system manufacturers to participate in a technical pre-qualification exercise wherein the cable and its accessories – identical to the system that was to be installed in Berlin – had to go through a one-year rigorous test programme at the CESI’s test lab in Milan, Italy.

BEWAG approached the technical body CIGRE which is the International Council on Large Electric Systems and headquartered in Paris, France, to develop the testing specifications. In September 93, the one-year rigorous tests began at CESI’s lab.

With some interruptions, the long-term testing was completed in April 1995. But only one participant passed the gruelling tests successfully and this company was issued a Pre-Qualification certificate.

More Vendors in The Kitty

As only one qualified vendor would leave the field lopsided, BEWAG decided to develop more vendors before introducing the new technology. Therefore, it once again invited more cable system suppliers, including the so far unsuccessful candidates, to participate in a second test sequence. This rigorous testing which started in 1995 was completed in 97.

The participants who were given second chance could improve and modify their technology with lessons learnt from failures in the first test. Five out of six vendors passed the second test. Thus, at the end of the second series of tests, there were six pre-qualified suppliers.

Having developed sufficient vendors in the 400 kV EHV cable technology, BEWAG selected two vendors— the lone qualifier in the first test and one from the second test, and placed orders on both to install the first 400 kV XLPE cable system in Germany.

The two vendors were awarded one circuit each. The historic interlink was commissioned in 1998.

Lessons for Sharing

In India, with rapid upgradation of the transmission network, there will be a growing need for 400 kV XLPE underground cable system, especially for passing through crowded cities. Currently, a global tender is the best option for 400 kV cable in view of the limited availability of local technology in this range.

A nodal entity like Powergrid Corporation can proactively support the process of developing a bunch of local manufacturers in the 400 kV and higher EHV cable technology.

The process of technology management deserves careful consideration as in the above historic Berlin case.

(The author works as AGM, Powertech Engineering LLC, Muscat. The views are personal.)

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