“The Beast”: MR delivers the largest OLTC ever built


A 575 MVA phase shifter for Consolidated Edison using the largest MR OLTC ever built left the transformer factory of ABB in Bad Honnef on 7 August 2013 headed for the USA.

The city of New York consumes vast amounts of electrical energy every day which Consolidated Edison, the local utility, must deliver and distribute to millions of people. Since reliability is essential, ConEd must control the power flow on each of a large number of transmission lines which bring electrical power into the city -- the power flow needs to be maximized without overloading the system.

In this context, ABB Bad Honnef delivered one large phase shifting transformer (PST) to the 345kV Ramapo substation located in the north of New York City. PSTs are regulating transformers with the ability to control the electrical power flow in transmission and distribution networks. With the PST, which is designed to avoid overload conditions, ConEd is able to optimize the power flow into New York while simultaneously increasing the reliability of the system.

The city of New York is special and it therefore has special requirements. Hence, the engineers of ABB Bad Honnef and MR teamed-up to provide an outstanding technical solution for this powerful and efficient regulating transformer. The compact and complex transformer design meets the strict noise-level requirements of New York as well as other technical limitations.

Due to the physical size of this kind of transformer, it consists of two tanks which are connected via oil-filled tunnel connections. It delivers 575MVA power at a high voltage level of 345kV. Still, ABB kept the dimensions “small” so that the transformer can be transported from one station to another within the New York City area. Once the transformer is completely installed, the “light” weight will increase to a total of 740 tons with an area of 19 by 14 meters! A noise enclosure brings the unit into “whispering mode” even under full power operation. The main feature - the large phase angle regulating range of +/- 40 degrees - is accomplished by special tailor-made on-load tap changers delivered by MR.

For this “Beast” MR and ABB cooperated deeply to fulfill all technical requirements and MR was able to provide the needed solution with an OLTC OILTAP 3 X G I 3002-123/E-18 35 1WS including a TAPMOTION® ED 200 LT motor drive (equipped with monitoring device TAPGUARD® 260). As only a few pieces of this type of tap changer are produced every year and this was the first time since the 1970s that 3 G-type OILTAP on-load tap changers have been installed in a single transformer, MR had to face a lot of challenges arising during production, assembly and testing.

  • MR built a special wooden test stand for testing the 3 large on-load tap changers together with the motor drive unit and the monitoring system
  • MR fulfilled the short delivery requirements by delivering the OLTCs only 9 months after receipt of the purchase order
  • MR supported ABB on site in Bad Honnef in regard to commissioning, testing, and installation issues
  • This OLTC is the most powerful, most expensive and largest OLTC ever produced by MR for a single transformer

Thanks to all involved colleagues who made the project a big success story for MR.

t.stohr@reinhausen.com  

 

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