NPP: Power Grid Mutual Safety Assessment - Nuclear Power Plant Instrumentation and Control Systems for Safety and Security - page 405

of influence and systems being under influence.
The value characterizes the strength of influence.
The influences between NPP and PG elements
could be represented by a matrix of influence
shown in the Table 1.
The influence matrix shows how elements of
the system influence each other and strength of
their influence. As an example, NPP influences
TPP with a strength - medium and HPP with high
level of influence. Generally, influence is an abil-
ity of one system to determine the state, charac-
teristics and behavior of other systems.
To evaluate the influences between NPP and
power grid systems we need to have the metrics
by which this influences could be measured and
compared. Two types of metrics: linguistic and
numerical are suggested. The linguistic metric
operates with the linguistic values used to evalu-
ate the strength of influence. The different values
as high, medium and low are applied to consider
and predict the smart grid's system state changing
provided the accident in other SG system occurred.
Numerical values, as ranks, are used in the similar
way, and the different ranks stand for the differ-
ent strength of influence. Expert judgments are
considered as the basis for taking the influence
values. The influence database is completed for
each NPP. These values are regularly updated.

Physical, geographical, organizational, informa-
tional, logical, societal is a particular influence.
Total influence might be represented as:

NPP NPP NPP NPP NPP NPP

I ( I ( ), t I ( ), t I ( ), t I ( ), t I ( )) t

t geo phys org soc log

(1)

The total influence is a time dependable value.
The changes of NPP states and characteristics
stipulate the changes of the total influence value.
We could illustrate the particular influence, for
example geographical influence of NPP on other
system of power grid shown in Figure 2.
Formally, the geographical influence of NPP
on other systems of power grid might be written
as:

NPP

I t

I NPP

( ) =

→

geo

{ } =

( TPP I NPP ), ( → HPP I NPP ), ( → TG )

= { Medium M H ( ), igh H Low L ( ), ( )}.

(2)

The value of geographical influence could be
calculated as:

I

∑ (

NPP i

I = I NPP → SPG ) =H + M + L.

(3)

geo geo i

i = 1

Space of Influence

NPP could influence the power grid in the different
ways as physically, geographically, organization-
ally, by means of information, logically, societal,
etc. Thus, we introduce the space of influence.

Figure 2. Geographical influence

Table 1. Matrix of influence

NPP TPP HPP

NPP - M H

TPP L -

HPP M -