The interconnection of power system network is the connection of one isolated power network, normally belonging to one country, to another isolated network, belonging to another country, via a tie-line or DC link. It has long been recognized that interconnection of individual power system network can provide more beneficial operating conditions both technically and economically [1]. One good example of this interconnected operation is UCTE where European continent's networks are interconnected and operating as one synchronous zone. Part of main advantage of the interconnected network can be summarized as follow: 1) Provide better network security and stability by sharing of available network reserve through interconnection. For example, the lost of generation in one country can be quickly compensated by spinning reserve in another. 2) Provide opening for the trading of power between countries leading to a liberalized electricity market. This point is of great interest in the present development of the electricity

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Advance Planning Tool for Managing a Dynamic Interconnected Power
System in a Liberalized Electricity Market
K. Chan, G. Rizopoulos and AAT Al-Subaie
Kahramaa, Qatar Electricity and Water Corporation
kchan@km.com.qa , grizopoulos@km.com.qa and aalsubaie@km.com.qa
Abstract
This paper addresses the need for the development of
advance planning tool in a dynamic interconnected
power network. The main objective of the tool is to
provide a quasi real time indication of the network
transfer capacity to aid real time trading between
interconnected partners in a liberalized electricity
market. Through proper operational planning the
interconnected network can be operated securely by
determining the limiting power that can be traded
between partners. The detail blocks of the advance
planning tool from requirements to implementation will
be discussed in this paper including an example usage
in the UCTE interconnection.
Keywords: interconnected network, advance planning
tool, network transfer capacity, network congestion
1. Introduction
The interconnection of power system network is the
connection of one isolated power network, normally
belonging to one country, to another isolated network,
belonging to another country, via a tie-line or DC link. It
has long been recognized that interconnection of
individual power system network can provide more
beneficial operating conditions both technically and
economically [1]. One good example of this
interconnected operation is UCTE where European
continent's networks are interconnected and operating as
one synchronous zone.
Part of main advantage of the interconnected network
can be summarized as follow:
1) Provide better network security and stability by
sharing of available network reserve through
interconnection. For example, the lost of
generation in one country can be quickly
compensated by spinning reserve in another.
2) Provide opening for the trading of power
between countries leading to a liberalized
electricity market. This point is of great interest
in the present development of the electricity
market as it relates to the economic of power
generation and consumptions. This allows
network with power generation resources to
supply network with limited generation, both
preventing the wastage of power in one network
while reducing the generation cost in another.
This will economically maintain the generation
and demand balance.
The dynamic interconnection of the network provides
many benefits, however; it also creates new challenges
to transmission system operators (TSO) especially under
a liberalized market where power trading is involve.
Energy trading occurs daily on spot basis, where the
generation scheduling and power exchanges between
interconnected partners are dynamic to meet the
changing load demand. The necessity to operate the
interconnected network close to its physical limit under
this dynamic conditions leads to the need for more
stringent and advance operational planning tools for
TSO in order to observe the network transfer capacity
and prevent network congestion [2].
2. Purpose and Requirements of the
Advance Operational Planning Tools
Management of power system security is an
important aspect for the generation, transmission and
distribution of power in order to ensure good quality and
reliable supply that will be in constant demand. This is
especially true in an interconnected power system with
liberalized power trading where any agreed transactions
will need to be fulfilled by monitoring real time network
transfer capacity. The failure to plan the network day to
day operations adequately will results in network
congestion where the promised power cannot be
delivered from one partner to another. This can lead to
catastrophic conditions which in some instances will
result in system collapse due to power shortages or
severe interconnections overloading.
Take for example the interconnected network shown
in Figure 1, between three individual countries A, B and
C. If a trading agreement is to export X MW of power
KH Chan
PO Box 2629, Doha Qatar

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from A to C during an agreed period, the generation in A
will be scheduled to generate X MW more that the local
demand and generators in C scheduled to generate X
MW less than local demand. By the nature of power
balance, the deficit of power in C will be supplied from
A.
However, the net flow between the tie-line of A and
C might not reflect the full amount of this exchange as
some of the power could have flow from A to C via B.
Hence, the network congestion that has direct affect on
the transfer capacity is not only limited by the tie-line of
A to C but also the network of B depending on the
network impedance path. A planning tool is necessary to
analyze and determine the point of congestion in order
to ascertain the possible net transfer capacity between
two trading partners. The net transfer capacity is
important to prevent partners getting into trading
agreement that's cannot be met technically.
Figure 1: Power exchange diagram
The advance operational planning tool involves
various steps or blocks of individual analysis that
interlink to each other. In general the following steps or
blocks of equipments are the minimal requirements to
implement the advance operational planning tool:
a. State Estimator
Unlike long term planning where the network
model construction for future years can be based
on large degree of assumptions, the advance
operational planning requires more reliable
estimates based on the most recent network
conditions. State estimator as part of an Energy
Management System can provide a forecasted
condition of the network loading based on current
condition.
b. Scheduler
Real time generation schedule of individual
partners for present time period is important to
forecast the permitted schedule, or exchange
between partners, for the next time period of
interest.
c. Planned Outages
The knowledge of planned outages in the required
forecast period is important to create an accurate
network model.
d. Automated network analysis tool
The network analysis tool is required to merge the
information obtained from a. to c. to create a
network snapshot model. Studies will then be
performed on the forecasted snapshot model to
determine the permitted exchange in the network
to maintain security.
The individual tool from a. to d. must be able to
function interlink to form the basis operation of the
advanced planning tool. The proposed operations will be
discussed in the following sections.
3. Methodology
The methodology of operations as mentioned in
Section 2 is about integrating the required individual
blocks. The operation methodology can be summarized
in Figure 2.
For example, let us base Figure 2 on the power
trading between partner A and C in Figure 1 for time
period of interest at 1330 hour. The purpose of this
operational planning tools is then used to determine
what is the maximum power that can be traded between
the two partners at the required time by forecasting in
advance, for example at 1230 hour.
The state estimator is used to predict the network
loading at 1330 hour for all the partners A, B and C
based on known values of 1230 hour. The forecasted
outage for 1330 pm is received. The automated network
analysis tool will then merged this information to create
a forecasted snapshot model representative of the
network at 1330 hour.
With this snapshot model, the generation of each
partner is applied to the respective network by scaling of
generation to meet the schedule. Once this is completed,
an automated sensitivity studies on the transfer limit
between partner A and C can be performed. The
generation in A will be increased in steps, and C reduced
likewise until a network loading or voltage violation is
recorded.
A
B
C

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The possible network transfer capacity can be
calculated based on the transfer limit obtained. The
transfer capacity can then be relayed back to the
dispatcher, which will adjust the generation in A and C
accordingly for the 1330 hour. If for any reason the
permitted power transfer does not meet the requirement
at C due to technical limitations, then there will be
ample time for network operators to increase local
generations, seek import from other partners or perform
load shedding.
4. Development and Selection of the
Advance Planning Tools
Sections 2 and 3 described the required tools or
blocks; and the methodology where these blocks can be
used for completing the advanced planning tools. The
successful development of the proposed method requires
time perfect co-ordinations between the individual tool;
as well as different network partners. Hence, it is
inevitable that the first step of development is a reliable
communications system where data can be exchanged
freely.
From Figure 2, it is clear that information exchange
is required; and in many cases this information is passed
on as data files. The electronic exchange of these data
files is only feasible with a computer server established
to interconnect individual blocks. The host server with
its FTP and electronic storage will be the information
exchange points.
The host server alone is insufficient for the control of
the advance planning tools. As time co-ordinations are
required, flow controller is necessary to function at the
heart of the server to supervise and control the planning
tools. For example, the flow controller will be
programmed to obtain information from SCADA system
at 1230 hour; through the server, and trigger the
operation of the State Estimator. Upon completion of
estimation, the state estimator will send a signal to flow
controller that information and it can be picked up from
exchange server. Then workflow control will go on to
the next stage; and so on.
The computer server and flow controller is important
as a logistic controller in the advanced planning tools.
However, the main purpose of the tool is for performing
of quasi real time analysis to determine network transfer
capacity. While the network analysis tools can be any
available industrial power system packages; it must be
assessed thoroughly for the following:
1. Reliability – accuracy of results from for large
quantities of load flow and contingency
calculations.
2. Robustness – able to operate continuously
without program crashing; or unnecessary
built up of temporary files and optimizes
usage of computer memories.
3. Flexibility – while most available industrial
power system packages can offer reliability
and robustness, most do not meet the
requirements for flexibility. The network
analysis tools must have the benefit of
operating in an automation loop without
human interaction through internal
programming language. A program with
flexibility of an in-built macro will be
necessary to function within this advance
planning tools.
5. Application
An example application of similar advance
automation tool that was purpose built, and in operation,
in the liberalized interconnected European market is
presented in [2].
Figure 3: European Zone cover by advance planning
tool reported in [2]
The implementation of the planning tool has
significantly reduced the time required by network
operators to perform calculations for network forecast.
The required time dropped from 120 minute with
manual calculations, to 2 minutes with the advance
automation tool. With the time efficient operations, the
network conditions can be forecasted in smaller intervals
which allow network operators to operate the network
closer to its real time limit while maintaining continuous
security.

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Figure 4: Reduction in calculation cycles
The required analysis results and the reporting format
can be tailored as part of the advance automation tools
to meet the requirements of individual network
operators. Presentations of these results are normally
design to provide concise well organizes information for
the decision maker.
6. Conclusions
In this paper, the idea of implementing an advance
planning tool for managing dynamic interconnected
power systems is discussed. The details from
methodology of operations, development and selection
of tools are provided.
With the GCC nations heading towards greater
energy co-operation through the planned GCC
interconnection, it is inevitable that a well unified
advance planning tool is required. This is especially the
case if the interconnection is open up for market trading
beyond the current planned emergency operation. The
paper is written to address this issue, and to bring
awareness to the tool that will be required for the secure
operation of this interconnection in the future.
7. Acknowledgment
The first author will like to acknowledge fellow co-
authors of reference [2] for their original contribution to
the plots of Section 5.
8. References
1. UCTE Operational Handbook, Policy 4
2. D. Tchoubraev, N Singh, U Studer, KH Chan and M
Barlow, "Advance Automated Approach for
Interconnected Power Systems Congestion Forecast",
MedPower’04 Conference and Exhibitions, Cyprus,
November14-17, 2004.
Figure 2: Methodology of Advance Planning Tools
State Estimator
Forecast for 1330
hour
1230
hour
SCADA information about the
network data for 1230 hour
Network with
estimated loading,
schedule and
connectivity for 1330
Automated
network analysis
tools
Trading request(s)
from partners for
1330 hour
Scheduler
Planned Outage
Projected Outage
information for
1330 hour
Projected
generation
schedule for 1330
Feedback to dispatcher of
each partners for necessary
actions to balance
generation and demand
Next time period
(1430 hours)
Calculated net transfer capacity
Revised schedule for 1330
hour and trading limit to
maintain network security