Engineering, 2013, 5, 174-179
doi:10.4236/eng.2013. 51b032 Published Online January 2013 (http://www.SciRP.o rg/journal/eng)
Operation Indices for Sm art Power Di spat ch
Center Design
Jianing Liu1, Puming Li1, Jin Zhong2, Liang Liang2
1Power Dispatch Center, Guangdong Power Grid Co., Guangzhou, China
2Department of Electrical & Electronic Engineering, The University of Hong Kong, Hong Kong, China
Received 2013
Abstract
With t he deve lopment of po wer sys tems, po wer grid within a control area becomes much more complicated due to in-
creasing number of nodes and renewable energy interconnections. The role of power system control center is more crit-
ical in maintaining system reliable and security operations. Latest developed information and communication technolo-
gies provide a platform to enhance the functions and performance of power system control center. Smart power dispatch
concept will be the trend of future control center development. In this paper, we start from the human factors of control
center design and propose operation indices to reduce the information presented to the system operator. The operation
indices will b e t he impo rtant c rite ria in situatio n a warene ss o f a po wer grid. Pa st, pr esent, future a nd cap abilit y sta tes o f
a power grid are also proposed to provide better visions to the operator of system conditions. The basic ideas of opera-
tion indices and operation states are discussed in the paper. In the end, the design factors for a power dispatch cockpit
are discussed.
Keywords: Control Center; Power Dispatch; Operation In dex ; Power System Operati on ; Human Factors; Power Dispatch
Cockpit.
1. Introduction
Control ce nter is the so ul of a po wer system for it s oper-
ations. The task o f control center is to maintain real-time
balancing of power supply and demand while achieve the
security, reliability and economic requirements of power
system operation. The concept of smart grid was raised
after the 2003 North American blackout. The purpose of
smart grid is to upgrade existing power systems with
latest communication, power electronics and control
technologies [1]. Besides the upgrading of power genera-
tion, transmissio n and distributio n facilities, a smart con-
trol center usin g latest tec hnologies i s essential for future
smart grid. The development of control center used to
follow the requirement of power system operation and
management, while updated with the development of
communication technologies. In a smart grid, the func-
tions of a control center and the way of power dispatch
will have an essential change to adapt newly developed
smart grid.
The development of supervisory control and data ac-
quisition (SCADA) system could be traced back to the
1965 blackout of New York [2]. Power system mea-
surement and monitoring system was developed. Later,
advanced applications like security analysis, load fore-
casting, generation scheduling, and contingency analysis
were developed. With the monitorin g data fro m SCAD A
and the advanced applications, energy management sys-
tem (EMS) was deployed. The SCADA/EMS system has
been used in almost all power control centers in the
world fo r p o wer s yst e m moni t o ri ng, a nal ys i s a nd control.
The basic concepts and framework of SCADA/EMS
were deployed in 1970s-1980s [3]. The upgrading in
recent years is mainly focus on software implementation,
visualization and communication [4-6]. Much more data
and information is available to the system operator with
the upgrading of communication and data acquisition
met hod s. With the latest gener atio n of SCAD A/EMS, t he
system operator is facing a huge amount of data, both
real-time and offline data. The data available to the sys-
tem operator have been increased exponentially. Howev-
er, the design concept of EMS still keep the same as be-
fore, the system operator monitors operation data and
needs to make operation decisions in the emergent situa-
tion according to their experiences or base on the calcu-
lation results of off-line decision tools. The design
framework works well in the past, as the amount of data

J. N. LIU ET AL.
175
available to the operator is limited. Nowadays, plenty of
data acquired from SCADA system is available to the
system operator. In contingency situations, it is hard for
the syste m oper ator to quickly locate useful infor mation,
analyze power flow distribution, re-allocate power flow
and modify network topology. Although latest EMS sys-
tems have better analytical abilities, manual operations
from system operators are still necessary. To safely op-
erate a complicated system as large-scale power system,
human factors and visualizations techniques need to be
considered in the design of control center to improve t he
per for ma nce a nd d ec isi o n ma ki ng by t he s yste m operator
in emergent situat ions.
In this paper, we will discuss the philosophy of control
center design considering human factors and ergonomics.
To simplify the data faced to the system operator, we
will propose several important operation indices for the
syste m operator to make quick decisions. In the end, the
concept of dispatch cockpit for a power system control
center will be presented.
2. Control Center Design Issues
2.1. Man-Machine Model
Power system is the most complicated system in the
world not only because of its large amount of bus-bars,
generation and transmission devices. In different opera-
tion states, voltage and power parameters are different,
and they indicate the trend of future states. Automatic
breaker actions due to fault events or overloading c hange
the topology of the network. The large number of devic-
es and the real-time changing of operation states produce
a lot of real-time information to the system operator,
whose work is to receive information and act on the basis
of the information to control the system. This is a
man-machine model.
A well designed interface and framework of a
man-machine model could significantly improve the ef-
ficiency of the control system. Especially during the
emergency states, quick and correct actions to the events
are very important. The issue in power system control
center is that the system operator needs to handle too
much information in very short time to react to emer-
genc y situation. A clear i nd ic ation of operation states and
simplified (after analysis) information could release the
pressure to the system operator and help them to make
quick dec isions.
2.2. Visualization and Human Factors in Control
Centers
The man-machine interaction has been applied in the de-
sign of EMS and power system contr ol center. For e xam-
ple, one-line diagram, 2-D visualization and geographic
information are used to display the power grid. Multiple
screens are used for displaying of grid topology in mul-
tiple layers. 3-D visualization and animation are also
proposed for power system analysis [7], which could eas-
ily indicate severe voltage problem or over-loading. Vi-
sualization software is also developed to display power
flow and ope ration data i n a use r -friendly interface [8]. A
Web-based tool with flexible open data structure is pro-
posed to serve as a platform for power system visualiza-
tion [9]. I n 1980s, human factors have been considered in
the design of dispatch control centers for utilities to
overcome stressful situations in system operations [10].
The major states of power system operations are normal,
degraded, and restorative. Therefore, the operator’s activ-
ities can be categorized as pre-dispatch, dispatch and
post-dispatch. Raw data needs to be converted to useful
necessary information for three different time lines.
3. Operati on Indices for Diff erent Operati on
States
3.1. Operation States for Power System Dispatch
In traditional power system dispatch and state estimation,
system operations states are classified as normal, de-
graded and restorative states. With our operation expe-
riences of a large-scale power grid, fours states with sim-
ple indices are proposed. The four states are past state,
present state, future state and capability state. For present
state, it shows current situation of the system, for example,
whether it is normal state, abnormal state or in emergent.
The present state will become past state with time passing.
The future state is calculated based on the system fore-
casting result, current system parameters and raw data.
Analytical tools need to be used to calculate the state pa-
rameters of present and future states. Capability state
shows the stability capability of a system. It is somewhere
between present state and future state. The definition and
calculation of the state are based on the system reserve,
loading margin, e tc. T he four states and its times lines are
shown in Figure 1. For present and future states, each of
them has normal, abnormal and emergent states. The rela-
tionship and interaction between the normal, abnormal
and emergent states are show as in Figure 2.
Past
state Present state Future state
Capability
state
Past FuturePresent
Figure 1 . Four states with timelines

J. N. LIU ET AL.
176
Normal
Abnormal
Emergent
Disturbance
Fault
Operator
control
Control
Figure 2. Normal, abnormal an d emergent states and t heir
control relationship
3.2. Key Performance Indi cat or
In the complicated industry control system and manage-
ment cockpit, key performance indicat o r (KPI) is used as
the useful infor matio n converted from raw data to simply
tell the situation of the system. The KPIs can be used as
the benchmark to sense the operation situations, hence to
achieve situation awareness. In this paper, we will pro-
pose an index system for power system dispatch from
different time scales and various aspects: security, eco-
nomic, environmental and operation risk. The compro-
mised index considering four indices can evaluate the
operation state of the grid. The indices are shown as in
Figure 3.
Security Index
Security is the most important issue in power system
operation. Security index plays an important role in de-
ciding syste m oper ation states and operational ris ks. T he
security index mainly affects present state monitoring
and future state monitoring. Figure 4 shows the position
and relationship of a security index with other operation
states and da ta. Figure 5 sho ws t he definition of security
index.
Raw data
Power system data
Weather data
Geography data
tie line power flow
real power, reactive
power voltage, phase
angle, frequency,
status of primary
devices and secondary
devices
temperature, wind,
humidity, rain,
thunderstorm, etc.
area,
geographic condition
Figure 3. Structure of operation indices
Security index
Security index
criteria
Present state
monitoring Future state
monitoring
Present SCADA
data
Forecasted
future data
Generation schedue
Load forecasting
Figure 4. Security index wi th operation states
Figure 5. Security index .

Engineering, 2013, 5, 174-179
doi:10.4236/eng.2013. 51b032 Published Online January 2013 (http://www.SciRP.o rg/journal/eng)
Economic Index
Economic factor is one of the concerns in power sys-
tem dispatch. In Guangdong power grid, pump-storage
capacity is high. It is used for quick reserve and energy
storage. The economic benefits of pump-storage need to
be considered when dispatching pump-storage stations.
The other factors need to be considered are total cost for
power generation and purchasing, electricity average
price and cost of transmission losses. The definition of
eco nomic ind ex is s hown in F igure 6.
Environment
Evaluation Index
Average Coal
Consumption Green Power
Ratio
Figure 6. Economic index
Environmental Index
Carbon emission and other environmental issues need
to be considered in power system dispatch nowadays due
to the policy of renewable energy target and emission
control. The environmental index can be simply consi-
dered based on the emission of coal-fired power plants
and the penetration of renewable energy generation in a
grid , as shown in Figure 7.
Economic Evaluation
Index
Average Cost of
Purchase of
Electricity
Network Losses
Cost
Total Cost of
Purchase of
Electricity
Pump-Storage
Economic
Efficiency
Figure 7. Enviro nmental index
3.3. Applying KPIs to Operation States
The security index, economic index and environmental
index can be calculated for present state, future state and
past state based on the raw data from SCADA and ana-
lytical results of advanced applications. The normal, ab-
normal and emergent status can be easily displayed for
past, present and future operation. It simplifies the in-
formation to the system operator.
Capability state is calculated in a separate way. It
shows the capability of a system under the situation that
all security criteria are satisfied. The index of capability
state should reflect real-power adjustment capability,
network topology, transmission margin, system reserve,
freq uenc y margin, etc., a s sho wn in F igure 8.
Figure 8. Capability state and its indices
4. Design of Cockpit for Power System Con-
trol Center
Dispatching and operating a power system is more or
less like controlling a complicated system or driving an
aircraft to be sure that everything is on the right way.
The control objective of power control center is to main-
tain nominal frequency and also be sure all facilities are
operated under normal situation. If there a fault event,
quick actions are needed to release the fault as well as
minimize the number of customers affected / blackout
area.
In China S outhern G rid (CS G) , the concept of dis patch
cockpit has been proposed for control center design. The
concept base on the fact that the man machine interaction
in power control center is similar as the man machine
control in the co ckpits of aircra ft or other industrial co n-
trol systems. The power system operator needs to aware
the si tuatio n by e yes, ea rs and brai n, and c ontro l the sys-
tem by hand. The operational decisions made according
to real-time information aim to operate the system as
pre-scheduled, as well as within security regions. Key

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178
performance indicators designed for power dispatch cen-
ter condense information from raw data; provide visible
information to i nd ic a te the system situation.
The KPIs of present state and future state present most
important information to the system operator. If both of
them are in normal states (with green light), the system
operator could relax. Once alert states (for example yel-
low light) appear, the system operator needs to quickly
check the system data and trace back to find the source
of the emergency, and remove the risk through certain
operations. If the system shows that the future state is
abnormal (red light), the system operator needs to
quickly adjust the system parameters to contr ol the future
state to be back to normal state. If the index of capability
state shows that the system operation margin is not that
good, the system operator needs to adjust the system
conditions to guarantee enough security margin and re-
serves. KPI design and the accurac y of its calculation are
very import ant i n this case.
The other concept introduced to the power dispatch
cockpit is the functions required by different manage-
ment levels. For example, the system operators need all
monitoring and control functions in the control center.
The upper level managers could have smaller cockpits in
their offices. Only information related to their manage-
ment jobs is displayed in their office cockpits. Different
departments have different access rights to operation
information, and different authorizations on controlling
the s ys tem.
Human factors and ergonomics design have great im-
pacts on operator’s reaction speed to emerge nt event s. A
well-designed cockpit system could also reduce the
pressure of the system operator during normal situation.
To design a good cockpit, practical experiences of sys-
tem operators are extremely important. The human fac-
tors design for a power dispatch center could from four
aspects:
• Monitoring: flexible monitoring layers are needed
for monitoring power flow interfaces. It would be
better to have flexible -defined power flow interfaces
and limits, which will help in deciding aler ting states
for pres ent and future situations.
• Control: real power adjustment and control methods
are essential. Friendly man machine control design
will increase the control accurac y.
• Decision making: automatic calculation and analysis
based on monitoring data is needed. Power flow in-
terface parameter calculations and adjustment strat-
egy notifications are important if they could be im-
plemented automatically and t imely.
• Alert: the way of alert could affect the system oper-
ator. A good alerting system could reduce system
operator’s pressure in normal situation as well as
improve their responding speed to emergent events.
• Latest information technologies could improve sys-
tem operators control on the system. For example,
most people use pad and smart phones nowadays.
The applications of touch screens, pad computers
and other mobile d evices in contro l center could im-
prove the work ef fi cienc y.
5. Conclusions
The paper discussed the issues of control center design
from human factors aspects. The operation indices of
security, economic and environmental are proposed to
reduce the amount of information faced by the system
operator. The operation indices are applied to past,
present, future, and capability states to simply indicate
system operation conditions. All these designs could be
applied in the co ntrol center to improve the efficie ncy of
man machine control. The new concepts of power dis-
patch cockpits are also presented and discussed in the
paper.
6. Acknowledgements
The work is sponsored by the Dispatch Center of
Guangdong Power Grid Co., Guangzhou, Guangdong,
China. The project number is K-GD2012-300.
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