Grid implementation of a 400MVA 220/150kV phase shifting transformer for power flow control
Rimez, Johan Wiot, Didier Jottrand, Emile Van der Planken, Ronny Claessens, Gert Declercq, Jan #
CIGRE Session edition:2006 location:Paris
Load flow studies concerning the power exchange in the border region of Belgium and France, have
shown that the old but important 220kV line between the RTE substation of Chooz (F) and the Elia
substation of Monceau (B) could go into a serious overload condition in case of failure or maintenance
on other transnational power lines or in case of outages on neighbouring interconnection transformers.
The importance of this power line to the industrial Charleroi (B) region obliges special measures to be
taken to protect the line against overloading while staying in service at all possible grid conditions.
The chosen solution consists in implementing a phase shifting autotransformer (PST) in the 150kV
substation of Monceau. The main characteristics were deduced from the results of the load flow
calculations (the simulations were done with and without a phase shifting unit): a 220/150kV
400MVA autotransformer (with OLTC for voltage regulation) able to provoke a phase displacement
between the 220kV and 155kV sides in the range of –15° +3° at full load; also by means of an OLTC.
From these characteristics, it is clear that shifting away the overload current is the main purpose of the
The implementation of the phase shifting transformer has also several operational consequences. Not
only the protection, control and command of the unit, but also various (external) grid events (lightning
strokes, single and multiple phase line faults, autoreclose of the circuit breakers) affect the design of
the PST. The transformer itself will have an influence on the power flow behaviour of the grid, the
protection schemes and the automatic systems in the substation. It is obvious that a close cooperation
and exchange of mathematical simulation models (of both grid and transformer) between the grid
operator and the manufacturer is necessary to cover all possible operational issues before the putting
into service of the transformer in march 2006.
With these experiences, the authors develop the expertise for the grid behaviour studies and
transformer performance for new PST implementations such as 400/400kV 1400MVA phase shifting
transformers to be placed at the electrical border between Belgium and the Netherlands.