How to use the NERC flowgate
for transfer limits analysis within my control area (I am a transmission
provider)?
It is a good idea to add flowgates
for the neighboring control areas to your regular contingency
analysis. Then you will be able to determine the location of the
‘true’ most restrictive constraint, which can be either
in your control areas or somewhere outside. If you choose to define
your own flowgates, then every PSS™MUST reported limit should
be defined as a flowgate. After defining your own flowgates it
is a good idea to repeat transfer limit analysis to verify that
the same limit is reported twice – as the conventional branch
and as a flowgate.
The NERC flowgate file doesn't
define flowgate limits. Does this mean that I can’t use the
NERC flowgates for transfer limit analysis?
The answer depends on the region
of interest in the US. For most of the US regions where flowgates
are defined as the monitored single branch in the base case or
under a contingency, PSS™MUST will define the limits itself.
In general, flowgates limits should
be defined together with flowgates definitions. Without transfer
limits you can’t use flowgates for transfer limit analysis.
For flowgates without defined limits PSS™MUST will attempt
to set the limits depending on the flowgate types:
For flowgates defined as a single line in the base case, it
will use the branch base case rating.
For flowgates defined as a single line under some contingency,
it will use the branch contingency rating.
For flowgates containing multiple monitored lines, flowgate
ratings will be defined as the sum of the branch ratings. This
may not be acceptable for the transfer limit analysis. You may
have to define limits for these flowgates. Fortunately, only
a small subset of flowgates has several monitored branches (mostly
in NPCC and PJM).
