In power system operation, operators must monitor a large and complex set of operational data while operating all kinds of control equipment and devices to maintain system reliability and stability within particular constraints. Although some tools can help operators to avoid this situation, the violation of these constraints could lead to misoperation. With the interconnection of power systems, grid operators must be able to analyze and evaluate a large amount of data and make cognitively demanding evaluations and critical, timely decisions under high pressure, meanwhile evaluating ever larger and more complex and changing data streams, and being fully aware of changing system operational conditions. They must focus on individually demanding and precise tasks while maintaining an overall understanding of a large amount of dynamic data affecting the operator’s perception and operation. The process needs to maintain awareness of the overall situation while evaluating an overwhelming amount of critical and ever-changing information. In power grid operation, situation awareness is the concept of describing the performance of an operator during the operation of the power grid. From the point of view of human factors, the situation awareness is described as (Endsley, 1995): “An expert’s perception of the elements in the environment within a volume of time and space, the comprehension of their meaning, and the projection of their status in the near future”. An example is the visualization tools that enable operators and other decision makers to operate a power grid effectively without cognitive overload.

1. Enhance Situation Awareness
In power system operation, operators must monitor a large and complex
set of operational data while operating all kinds of control equipment
and devices to maintain system reliability and stability within particular
constraints. Although some tools can help operators to avoid this
situation, the violation of these constraints could lead to misoperation.
With the interconnection of power systems, grid operators must be able
to analyze and evaluate a large amount of data and make cognitively
demanding evaluations and critical, timely decisions under high
pressure, meanwhile evaluating ever larger and more complex and
changing data streams, and being fully aware of changing system
operational conditions. They must focus on individually demanding and
precise tasks while maintaining an overall understanding of a large
amount of dynamic data affecting the operator’s perception and
operation.
The process needs to maintain awareness of the overall situation while
evaluating an overwhelming amount of critical and ever-changing
information. In power grid operation, situation awareness is the concept
of describing the performance of an operator during the operation of
the power grid. From the point of view of human factors, the situation
awareness is described as (Endsley, 1995): “An expert’s perception of
the elements in the environment within a volume of time and space, the
comprehension of their meaning, and the projection of their status in
the near future”. An example is the visualization tools that enable
operators and other decision makers to operate a power grid effectively
without cognitive overload.
The importance of situation awareness becomes greater as power
system complexity and dynamics increase. Elements in the complex and
dynamic power grid vary across time, possibly at different rates, and are
interdependent. In addition, current situation awareness affects the way

2. the new information is perceived and interpreted. Incomplete or
inaccurate current situation awareness will lead to poorer situational
awareness and at later times. Grid operators, therefore, must
continuously maintain high situation awareness. In the case of critical
circumstances, where the grid operator must correctly react within only
a limited amount of time, incomplete or inaccurate situation awareness
can result in serious errors in decision making with disastrous
consequences. The decisions that an operator must make often require
the acquisition and integration of a substantial amount of information
and, in certain situations, also call for a prompt response. An increase in
situation awareness knowledge could significantly increase the
frequency with which the grid operator makes optimum decisions and
decrease the time needed to reach these decisions. In addition, any
decrease in workload resulting from increased situation awareness could
also improve the chances of accurate decision making.
PMUs can help to maintain and enhance situation awareness by
incorporating PMU data to the power system analysis and visualization
tools. PMUs provide the operators with real-time measurement data
indicating power system dynamic in very high frequency. Effective and
efficient analysis and visualization tools based on PMUs can assist
operators at control centers to maintain situational awareness and
perform time-critical decision making tasks under critical conditions.
Visualization tools have been one critical part of modern EMS/SCADA
systems. One of the important goals in power grid visualization is to
convey a relevant abstract view of the power grid to an operator, in such
a way that the operator can understand the situation of the power grid
with minimal cognitive effort. Examples of such an abstract view include
bar charts, contour maps, pie charts, etc.
SCADA measurements provide a picture of the steady-state health of the
system, whereas PMUs capture the faster variations that may indicate
small signal stability problems. The information presented is static based

3. on steady state of the systems. PMUs provide more accurate and faster
data, and needs a more powerful and effective visualization tool to
convert the data to information useful for operator’s decisions.
Because the PMU is a relatively new technology, tools to increase
situation awareness based on PMU are limited.
Therefore, it is important to study and develop such tools. Other analysis
and visualization tools are also needed to enable the operators to make
appropriate decisions concerning system operations and data
management rapidly and correctly.
The primary concern in real-time operation of power system has been
real time information visualization, simply because the power grid is an
important visual reference in the power grid. A key component of
situation awareness tool is the access to current and historical PMU
data. The historical information assists operators to quickly evaluate the
priority of a given event compared to other potential events, when a
remedial action or decision must be made to solve the event.
Many applications deemed a success because of the usage of situation
awareness. Many pie charts, power flow animations, flow charts, text
massaging, etc. to deliver situation awareness are used. The unique
feature of the system is that it relies on visual or aural information for an
efficient delivery of the situation awareness. Situation Awareness Board
is a software tool to provide an analysis capability of the power system
control center to the operator. It helps in maintaining situation
awareness (Donnelly et al., 2006).
The tool gives the operator an indication of the important of information
and action within a “board”, a designated area by the operator. The
important indication is displayed on the configurable status board. The
goal of Situation Awareness Board is to make the complex PMU
environment intuitive by providing situation awareness.

4. Another promising technique that can be applied in PMU-based
visualization tool is virtual reality (VR). Virtual reality technique provides
a birdseye- view into a simulated power grid by overlaying entities and
information onto 2D view of power grid and visual databases. The
overlaid information includes tracking individual measurement and
group of measurements, providing visual information to an operator to
help build situation awareness.
The main functionality of the system is displaying concentrated
information of power grid entities. The virtual reality system can use a
grid based approach to compute the concentration, and constructs iso-
surfaces of concentration by considering the concentration value as
vertical data in a three dimensional space. Depending on the viewpoint,
concentration is shown by height or by color intensity. Thereby, the
vertical data serves as a redundant encoding of the concentration.
Analytical tools based on PMUs help operators in making decision by
converting raw data into meaningful information, to evaluate current
operating situation and predict the future operation status. More
advanced analytical tools can help to convert information to knowledge.
Usually the power grid is represented by large datasets with various
attributes. These large datasets make it difficult for an operator to
assess the situation in the power grid in a timely manner. Moreover, it is
more troublesome when it comes to dealing with the multi attribute or
multi dimensional datasets, since the operator has to spend more time
to build up a single comprehensive view of the power grid.
An appropriate visual interpretation of the power grid helps an operator
to build up a comprehensive view of the power grid effortlessly and
rapidly, and as a result to make a strategic decision accurately. One of
the keys to successful decision making is a clear and relatively accurate
understanding of the environmental context of a decision.