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MR in Sri Lanka to probe transformer failure amid grid stability concerns

Mar 21, 2016 14:46 PM GMT+0530 | 0 Comment(s)

ECONOMYNEXT - Technicians from a German manufacturer of transformer components that failed twice in a row causing blackouts this month, have arrived in Sri Lanka to begin their own probe, the head of Sri Lanka's power utility said amid concerns about grid stability.

A key component of the transformer in the Biyagama receiving station, known as a tap changer failed earlier this month, triggering a nation-wide blackout and also emergency shut-down of three coal plants.

A few days later another tap changer in Kotugoda, also near Colombo also caught fire.

Sri Lanka had blackouts in October 2015 and February and March 2016, which were related to weaknesses in the transmission network.

Amid speculation that the 2015 failure may have damaged the tape changer, Ceylon Electricity Board Chairman Anura Wijepala said there was no information to support the idea, but investigations were looking at all aspects.

Technicians from the manufacturers had also arrived in Sri Lanka, to start their own inquiries, he said.

The tap changers were made by Maschinenfabrik Reinhausen (MR) a well-known brand used by global power grids. The Biyagama receiving station was built in the early 1980s.

The tap changers on both occasions failed 'coupling transformers' which connects 220kV long-distance transmission lines coming from power generating stations to the 132kV network, mainly used in distribution, sources familiar with the matter said.

There are less than a dozen such locations in the country, where coupling transformers connect the two networks, sources familiar with the matter said.

Before 2015, private power plants which were retired were connected to the grid through 132kV lines, at the same voltage as the distribution side.

With their retirement after the contracts expired in 2015, the entire daily load now passes through the coupling transformers.

CEB is now going through emergency procurement to bring back at least three of the de-commissioned plants, which in addition to giving stand by power will also help with direct connection to the distribution side network and reduce pressure on the few coupling transformers.

It is not clear whether one or more existing generators could be also connected to the 132kV transmission network directly through some modifications.

The high voltage lines are preferred for long distances transmission as losses are reduced.

A committee is expected to present short and long term fixes to prevention country-wide failures today.

Sri Lanka's power regulator, which employed consultants to probe the 2015 outage said the CEB was allowing voltage fluctuations of 10 percent in its high tension networks which increased risks of tripping and aske the utility to reduce the tolerance to 5 percent.

The CEB has to file answers this week.


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