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Data,
whether it is monitored from the field or retrieved from some other system,
needs to have appropriate precision and accuracy. In particular, distribution
automation functions require more accurate data than system operators who
merely need to get an estimate of conditions. This data accuracy requirement
implies that (to the appropriate degree for the functions using the data):
· The source of
the data must be precise, with accurate CTs and PTs, appropriately scaled
analog-to-digital conversions, appropriate resolution of the digital values
(8-bits, 12 bits, or more bits to represent the analog value), and
appropriately precise calculations of derived values (e.g. var, VA, kW).
· The data sources
must be accurately calibrated.
· The data must be
converted correctly to engineering units or other measurement units.
· Data should be
validated for reasonableness, if not for more precise checks. For instance,
within IEDs, certain checks for consistency could be used to detect
inconsistent data, while at the control center State Estimation at both the
transmission and the distribution levels could be used.
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