  This paper presents the California Test System (CATS), a synthetic
transmission grid in California that can be used by the public for power
systems policy research without revealing any critical energy information. The
proposed synthetic grid combines publicly available geographic data of
California's electric infrastructure, such as the actual locations of
transmission corridors, with invented topology and transmission line parameters
that are ``realistic but not real". The result is a power grid test system that
is suitable for power flow and policy analyses with geo-referenced
applications, including studies related to weather, topography, and
socio-economic considerations. The methods used to develop and evaluate the
CATS grid are documented in detail in this report.
