  We study the structure of locational marginal prices in day-ahead and
real-time wholesale electricity markets. In particular, we consider the case of
two North American markets and show that the price correlations contain
information on the locational structure of the grid. We study various
clustering methods and introduce a type of correlation function based on event
synchronization for spiky time series, and another based on string correlations
of location names provided by the markets. This allows us to reconstruct
aspects of the locational structure of the grid.
