Safety Parameters Display Systems - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 354

power, loops in operation, etc. are displayed on
the video frame.
Insofar as a human easily recognizes differ-
ences in distortions in symmetrical geometric
figures, a true (in normal state of the production
process) polygon is used as the basic graphic
signal for displaying deviations of the production
process.
The lengths of segments (characteristic vec-
tors), which connect the center of the polygon to
its corners, will represent values of the generalized
safety parameters, that is those parameters from
the full set existing in the SPDS, which more
generally characterize the safety condition.
Each electronic line on the video frame depicts
a certain scale of generalized safety parameters.
Standardized values of critical operating param-
eters are shown on the scale in vector form.
The value indicating scales of each parameter
are standardized in such a way that the visible
length of all characteristic vectors is identical
in the range of values of the corresponding pa-
rameters that are accessible in a given mode of
the generating unit. The minimal value of the
corresponding parameter is 0.6 of the full length
of any characteristic vector. Positive deviations

from the norm drive the ends of the vector away
from the center of the figure. Negative deviations,
on the contrary, bring them closer to the center
of the figure. Thus, for all parameters the lower
limit is depicted closer to the center of the figure.
Segments that connect the ends of the char-
acteristic vectors in normal state form a true
geometric polygon on the screen.
For each characteristic vector of polar dia-
grams, the upper and lower limits are shown, which
represent: regulated limits (operating limits) for the
“narrow range” and “cold shutdown” diagrams;
emergency limits (design limits of safe operation)
for the “wide range” diagram.
The instantaneous value of a critical parameter
is represented by the end point of the characteristic
vector and the line that connects the end points of
the vectors forms a polygon. When the parameters
differ from the norm, a different geometric shape
appears on the screen.
Evaluation of a critical situation is simplified
and maximally minimized, that is the operator's
task reduced to comparing two geometric shapes
-- a polygon of instantaneous values of generalized
safety parameters and a symmetrical polygon of
nominal values of parameters.

Figure 1. Polarographic video frame “narrow range” (picture from the screen)