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					 Proceedings of the 14th International Middle East Power Systems Conference (MEPCON’10), Cairo University, Egypt, December 19-21, 2010, Paper ID 214.


A Practical Framework for Pricing of Backup Reserve and
               Wheeling in Power Systems
                F. Al-Duaij and M.S. Owayedh                                               M.A. El-Kady and Y.A. Al-Turki
                 Saudi Electricity Company                                        SEC Chair in Power System Reliability and Security
                   Riyadh, Saudi Arabia                                             College of Engineering, King Saud University
            FMDeej@se.com.sa, TCTED@se.com.sa                                          melkady@ksu.edu.sa, yasir@ksu.edu.sa



     Abstract - This paper presents a practical pricing model for             from the Lagrange multipliers of reserve constraints. Some
backup reserve and wheeling, which attains a balanced strategy                pricing issues were discussed in [3] regarding the security-
that ensures perceived benefits to both the buyer and the seller.             constrained electricity markets subject to transmission flow
The model and the associated computerized algorithm deal                      limits. In particular, the notion of separate reserve types and
collectively with diverse issues, including: 1) fulfilling local firm
                                                                              prices based on marginal costs was discussed and analyzed.
real (and reactive) power demand requirements, 2) fulfilling local
power reserve requirements, 3) buying firm real (and reactive)                     A probabilistic methodology was proposed in [4] to evaluate
power from the grid, 4) buying reserve power from the grid, 5)                the operating reserve requirements of power systems in
exporting firm real (and reactive) power demand to remote load                deregulated energy markets. The main objectives of the proposed
centers via the grid, 6) exporting reserve power via the grid, 7)             methodology included assessment of reserve requirements for all
wheeling of firm power demand to remote owned sites using the                 submarkets and the determination of the maximum acceptable
grid, and 8) wheeling reserve power to remote owned sites using               bid prices in these submarkets. On the other hand, the authors of
grid. Practical implementation features of the computerized
                                                                              [5] proposed a method to consider generator reliability explicitly
algorithms are also discussed with an illustrative case example.
                                                                              in the scheduling problem. The proposed competitive structure
     Index Terms - Power systems, Electricity-markets, Backup-                included a market for reserve and the problem is then formulated
reserve, Wheeling, Pricing-strategy.                                          as an augmented Lagrangian dual function to be solved by a
                                                                              recurrent neural network algorithm. The impact on the system
                         I. INTRODUCTION                                      voltage profile of VAR allocation pattern and associated system
                                                                              reserve in optimal power flow scenarios was discussed in [6]. On
Backup generation reserve is needed to solve security                         the other hand, the impact of forced outages on system reliability
problems during contingencies when some operating                             and associated capacity reserve availability was discussed in [7].
generator(s) becomes unavailable, leaving the system                               Similarly, the issue of wheeling of power among various
unbalanced with demand greater than supply. System voltage                    generation-demand points through the grid has also gained
and frequency immediately begin to drop. If they drop too far                 considerable attention in the literature [8-10]. The author of [8]
for too long, load must be shed, i.e. disconnecting loads                     described the principles and practice of a methodology for the
involuntarily, to rebalance demand with the remaining supply.                 evaluation of wheeling rates, which does not assume the
Thus spinning reserve and load shedding are substitutes for                   existence of a spot pricing based energy market place. The
the service of restoring system frequency. If sufficient                      wheeling problem is formulated as a nonlinear optimization
operating reserves are available so lost power can be replaced                program with linear constraints and solved by a gradient
within specified periods, there will be usually no need to shed               projection method in order to determine the amount of energy
load.                                                                         transported through each wheeling path and the associated
    The issue of backup reserve and the associated reliability and            wheeling price to be paid. On the other hand, the authors of [9]
security aspects has been addressed extensively in the literature             presented a valuable review of various pricing methodologies
[1-7]. In this regard, advanced computerized models have been                 and their implementation in different countries. In this respect, a
developed to include spot pricing of reserve generation and                   survey of the existing wheeling models and their advantages and
transmission capacities, as well as demand side bidding. In the               disadvantages was presented in [10].
model used in [1], a new formulation of the extended security                      This paper shares the results of a recent major industry-
constrained economic dispatch was presented. The formulation                  supported study with the aim to develop a novel pricing model
allocates both power and reserve generation resources. On the                 for backup reserve and wheeling, which attains a balanced
other hand, a methodology for allocating and pricing operating                strategy that ensures perceived benefits to both the buyer and the
reserves was presented in [2] based on a modified version of the              seller. The model supports the present open-market analysis of
security constrained economic dispatch is formulated. In this                 backup reserve and wheeling pricing simulation studies, in which
formulation, network constraints and line losses were considered              the generation company submits bids to the grid / regulating
and the optimal spot price for operating reserve was calculated               body for both firm and reserve powers as well as optional



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 Proceedings of the 14th International Middle East Power Systems Conference (MEPCON’10), Cairo University, Egypt, December 19-21, 2010, Paper ID 214.

wheeling of firm and/or reserve powers. During its current drive                   Also, a pricing structure for wheeling should provide the
toward a complete open electricity market structure, the Saudi                following incentives:
Electricity Company (SEC) is presently dealing with a special
                                                                              a)   The incentive to SEC to profit from using its own grid (and
business operating environment in which some of its major
                                                                                   even expanding / strengthening it) as a wheeling vehicle for
industrial consumers are in a position to offer and compete for
                                                                                   its major consumers to wheel generated power among their
surplus generation as well as request wheeling of firm power
                                                                                   demand centers connected to the main grid.
and/or reserve among their local facilities using the main grid.
When the company owning the grid also has its own generation,                 b) The incentive to the major customer to use SEC grid for
as in the current situation with SEC, while other major                          wheeling power (and/or reserve) among its various demand
consumers buy from SEC as well as sell to surplus power from                     centers connected to the grid rather than selling the excess
their local generating facilities, a balanced pricing strategy is of             power directly to SEC while purchasing the required power
an extreme importance. Such balanced strategy should ensure                      at the demand center again from SEC, or even build the
                                                                                 extra local generation capacity required at the particular
perceived benefits to both the buyer and the seller.
                                                                                 demand center.
    Practical implementation features of the computerized
algorithms and the associated simulation software are discussed
in regard to both backup reserve and wheeling pricing                                        III. PRICING MODEL FORMULATION
evaluation. An illustrative case example is also presented for                     Because the electricity market restructuring process is still in
demonstration purposes.                                                       progress, with still no defined structure for multi generation and
                                                                              distribution companies, a full-scale complex optimization model
                                                                              for solving the overall firm and reserve power pricing problem is
               II. PRINCIPLES OF PRICING MODEL                                considered not needed in the present situation. What was
    Without loss of generality, the pricing model assumes                     required by both SEC and the major customer is a basic
business interaction between the electricity company (SEC) and                simulation tool which determines the pricing structure in a
one of its major customers. The major customer has its own                    “what-if” tableau-type analysis with full user control over the
generation at some facilities (buses) to supply a portion of its              input data parameters.
local demand while purchasing power from SEC to supply the                         The “optimal” pricing strategy – as perceived by both SEC
remaining portion of its demand. Moreover, at some buses                      and the major customer – is therefore arrived at through
owned by the major customer, excess power could be wheeled to                 successive executions of the pricing simulation routine with
other buses owned by the same major customer under negotiated                 sequential updating and refining of the user input parameters as
agreements with SEC.                                                          mutually agreed upon via negotiations between buyer and seller.
    More specifically, a pricing structure for firm power demand              In this case, the problem formulation takes an additional
should provide the following incentives to both SEC and its                   complexity dimension as it deals collectively with diverse issues,
major customers:                                                              including: 1) fulfilling local firm real (and reactive) power
                                                                              demand requirements, 2) fulfilling local power reserve
a)   The incentive to SEC to recover both capital and                         requirements, 3) buying firm real (and reactive) power from the
     fuel/operation costs and profit from the use of its existing             grid, 4) buying reserve power from the grid, 5) exporting firm
     generation facilities (or even expand its existing generation            real (and reactive) power demand to remote load centers via the
     sites) in selling power to its major consumers, and                      grid, 6) exporting reserve power via the grid, 7) wheeling of firm
                                                                              power demand to remote owned sites using the grid, and 8)
b) The incentive to the major customer to maintain power                      wheeling reserve power to remote owned sites using grid.
   purchase from SEC using the main SEC grid) as a more
                                                                                   It is important to note that the overall pricing problem
   economically viable alternative to building its own extra
                                                                              comprises all entities (market players) dealing with backup
   generation facilities.
                                                                              reserve and wheeling in the electricity market. The money flow
                                                                              represents costs incurred – and revenues gained – by various
On the other hand, a pricing structure for reserve backup should
                                                                              entities. Wheeling fees, for example, are costs to the participating
    provide the following incentives to various electricity
                                                                              bus owners and, at the same time, revenues to the grid owner. It
    market entities:
                                                                              is, however, of essence to note that the collective costs of all
a)   The incentive to SEC to profit from making its own existing              entities do not cancel out the collective revenues, and therefore,
     generation facilities available for backup reserve to its major          profit opportunity exists for all entities. This is simply because
     consumers, and                                                           the overall pricing problem has two main external monetary
                                                                              parameters that are not associated with the interacting business
b) The incentive to the major customer to refrain from building               entities. These two main parameters are the cost of fuel and the
   its own extra generation capacity to provide the required                  associated transportation costs to power generation sites, which
   backup reserve to its demand centers and opt for acquiring                 are paid to external entities outside the costing model, and the
   the reserve power available from SEC through its power                     revenues from local power sales at various buses, which are
   grid.


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 Proceedings of the 14th International Middle East Power Systems Conference (MEPCON’10), Cairo University, Egypt, December 19-21, 2010, Paper ID 214.

collected by the consumers who, again, are not entities in the                    On the other hand, The total annual revenue for entity k is
pricing model. The market net margin of gains is predominantly                given by
determined by the relative magnitude of these two external                    R(k)      =     Rd(k) + Re(k) + Rr(k) + Rwd(k) + Rwr(k)
parameters, which may very well depends on one hand on the                                    + Rl(k)                                 (2)
global fuel prices and , on the other hand, on the tariff regulations
and rate caps imposed by the government and/or the electricity                which consists of the following components:
regulator.                                                                    Rd(k)     =     Revenue from selling power to local demand.
     When only some owners are considered in the pricing                      Re(k)     =     Revenue from exporting firm power to the grid.
problem while other owners are not modeled, the entire power                  Rr(k)     =     Revenue from exporting reserve power to the grid.
network buses should ideally by included in the power flow
solution while only the considered owner buses are included in                Rwd(k) =        Revenue (to grid) from wheeling fees of firm
the pricing calculations. However, in some cases, the non-                                    power.
considered buses may be regarded as static in terms of bus                    Rwr(k) =        Revenue (to grid) from wheeling reserve.
voltages and powers and, therefore, can be modeled in the power               Rl(k)     =     Revenue (to grid) from fees related to network
flow solution as external network equivalents. This would greatly                             losses contributions by individual buses.
simplify the network solution and reduce problem size especially
when the pricing problem is formulated for only one or two                    The net annual profit (revenue – cost) for entity k is given by
owners together with the grid.                                                F(k) = C(k) - R(k)                                               (3)
     In general, during the energy transactions occurring in the
semi-open market environment in Saudi Arabia, both SEC and                         Without loss of generality, the symbol (k) in the above
its major customers shall acquire revenues and incur costs. Each              expressions, which denotes a particular entity, can be considered
network bus in the system is considered as being owned by one                 to mean the sum of all buses and/or the grid (being one of the
entity only. In addition, the whole power grid is owned by one                entities) which are owned by the particular entity (k). For
entity, which may also own one or more buses. Therefore, an                   example, the annual cost, revenue and net profit can be written,
entity (SEC or a major customer) may own several buses in the                 respectively, as
system comprising combinations of generation and/or demand
centers.
                                                                              C(k) =    Σ C(i)                                                 (4a)
                                                                                       i∈Ik
     The total annual cost for entity k, which represents an owner
(including the grid owner) is given by                                        R(k) =    Σ R(i)                                                 (4b)
C(k) = Cc(k) + Cf(k) + Ce(k) + Cr(k) + Cwd(k)                                          i∈Ik
       + Cwr(k) + Cl(k)                                         (1)           F(k) =    Σ F(i)                                                 (4c)
which consists of the following individual entity cost                                  i∈Ik
components:                                                                   where Ik denotes the set of network buses (or the grid) owned by
                                                                              entity k. It is to be noted that the above cost coefficients are
Cc(k)    =    Annual equivalent generation (both real and
                                                                              subject to uncertainties in practice. However, in the present
              reactive power) capacity addition costs, levelized
                                                                              analysis, best estimate values for these coefficients are assumed.
              using associated capital recovery factors. The
              generation capacity covers both firm demand and
                                                                                                     IV. IMPLEMENTATION
              reserve requirements.
                                                                                   The approach followed in determining the backup reserve
Cf(k)    =    Generation fuel (to supply firm power demand)
                                                                              and wheeling pricing strategy is based on negotiating various
              and other operation costs.
                                                                              pricing scenarios representing bids submitted by the different
Ce(k)    =    Cost of importing firm power from the grid to                   generation companies the grid / regulating body for both firm
              supply local demand.                                            and reserve powers as well as optional wheeling of firm and/or
Cr(k)    =    Cost of importing reserve power from the grid to                reserve powers. Each pricing strategy is based on an assumed
              supply local demand.                                            solved network flow case in which the power flow equations are
                                                                              satisfied and a feasible demand-supply balance is attained. Once
Cwd(k) =      Cost of wheeling firm power through the grid                    a feasible network flow is established, various cost and revenue
              to remote buses owned by the same entity.                       components are calculated based on the proposed price
Cwr(k) =      Cost of wheeling reserve power through the                      coefficients being negotiated. Although is not the main subject of
              grid to some remote buses owned by the same                     this paper, the above formulation is also suitable as a base for
              entity.                                                         online pricing, in which case the solution of relevant econometric
                                                                              models would be required (smart grid applications). On the other
Cl(k)    =    Cost paid to the grid for bus contribution to
                                                                              hand, advanced sparse matrix techniques should be used for the
              network losses.
                                                                              application of the pricing model to large-scale power networks.


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 Proceedings of the 14th International Middle East Power Systems Conference (MEPCON’10), Cairo University, Egypt, December 19-21, 2010, Paper ID 214.

     Tables I and II show samples of the output calculated                          Tables III and IV show samples of the user-input data
quantities in a typical backup reserve and wheeling pricing study.              parameters in the reserve and wheeling pricing simulation
A set of advanced software simulation modules are used to                       software.
simulate, examine and evaluate various feasible pricing
strategies. The simulation software is capable of dealing with
pricing strategies for firm demand, backup reserve and wheeling.                                                TABLE III
Both real and reactive powers are modeled. In addition, wheeling                      SAMPLE OF USER-INPUT DATA PARAMETERS (BUSES)
of reserve power among same-owner buses is possible.
                                  TABLE I                                           001        Bus ID-# {Max 5-Digits}
                                                                                    002        Bus-Owner ID-# {Sequential 1 ~ 98}, 99 for Grid
    SAMPLE OF OUTPUT SIMULATION PARAMETERS (OWNER)
                                                                                    003        Bus Type >> 1:(Load), 2:(Gen), 3:(Slack)
   1    Owner ID-#                                                                  004        Real Power Generated at Bus
   2    Cost of Fuel Paid to External Fuel Supplier                                 005        Reactive Power Generated at Bus
   3    Cost of Capacity                                                            006        Bus Voltage Magnitude
   4    Cost of Buying Real Power Demand                                            007        Bus Voltage Angle
   5    Cost of Buying +ve Reactive Power Demand                                    008        Local Reserve Real Power at Bus
   6    Cost of Buying -ve Reactive Power Demand                                    009        Local Reserve Reactive Power at Bus
   7    Cost of Buying Real Power Reserve                                           010        Export Reserve {Inc. Wheeled} Real Power at Bus
   8    Cost of Buying +ve Reactive Power Reserve                                   011        Export Reserve Reactive Power at Bus
   9    Cost of Buying -ve Reactive Power Reserve                                   012        Real Power Local Demand at Bus
  10    Cost of Paying Fees for Wheeling Demand Power                               013        Reactive Power Local Demand at Bus
  11    Cost of Paying Fees for Wheeling Reserve Power                              014        Capacity of Bus Real Power Generation
  12    Revenue from Selling Real Power Demand to Local                             018        Minimum Req. Reserve for Local Real Power Demand
  13    Revenue from Selling Real Power Demand via Export                           019        Maximum Req. Reserve for Local Real Power Demand
  14    Revenue from Selling +ve Reactive Power Demand to Local                     022        Cost To-Threshold of Bus Real Power Capacity
  15    Revenue from Selling -ve Reactive Power Demand to Local                     023        Threshold-Value of Real Power Capacity
  16    Revenue from Selling +ve Reactive Power Demand via Export                   024        Linear Cost {> Threshold} of Real Power Capacity
  17    Revenue from Selling -ve Reactive Power Demand via Export                   031        Constant Cost Coeff. for Bus Power Generation
  18    Revenue from Selling Real Power Reserve                                     032        Linear Cost Coeff. for Bus Power Generation
  19    Revenue from Selling +ve Reactive Power Reserve                             033        Quadratic Cost Coeff. for Bus Power Generation
  20    Revenue from Selling -ve Reactive Power Reserve                             034        Cost for Export Real Power Demand Supply
  21    Revenue from Fees for Wheeling Demand Power (Grid Only)                     040        Rate for Local Real Power Demand Supply
  22    Revenue from Fees for Wheeling Reserve Power (Grid Only)                    043        Rate for Export Real Power Demand Supply
  23    Cost to Bus / Revenue to Grid for Bus Contribution to Losses                046        Rate for Export Real Power Reserve Supply
  24    Total System Losses Supplied by Slack Bus                                   049        Cost paid to Grid for P-Loss {Bus Contribution}
  25    Revenue to Bus / Cost to Grid for Contribution to System Losses


                          TABLE II                                                                              TABLE IV
       SAMPLE OF OUTPUT SIMULATION PARAMETERS (GRID)                            SAMPLE OF INPUT SIMULATION DATA PARAMETERS (WHEELING)
   1    `99` Grid ID-#
   2    {Normally 0!}: Cost of Fuel Paid to External Fuel Supplier                        01     Wheel-From Bus ID-#
   3    Cost of Capacity                                                                  02     Wheeling Type 0:(None), 1:(Demand), 2:(Reserve)
   4    Cost of Buying Real Power Demand                                                  03     Number of Wheeling Transactions to Follow
   5    Cost of Buying +ve Reactive Power Demand                                          04     1st Wheel-To Bus ID-#
   6    Cost of Buying -ve Reactive Power Demand                                          05     1st Amount of Power to be Wheeled
   7    Cost of Buying Real Power Reserve                                                 06     1st Cost of Wheeled Power {Paid to Grid}
   8    Cost of Buying +ve Reactive Power Reserve                                         07     2nd Wheel-To Bus ID-#
   9    Cost of Buying -ve Reactive Power Reserve                                         08     2nd Amount of Power to be Wheeled
  10    Cost of Paying Fees for Wheeling Demand Power                                     09     2nd Cost of Wheeled Power {Paid to Grid}
  11    Cost of Paying Fees for Wheeling Reserve Power                                    ..     ...
  12    Revenue from Selling Real Power Demand to Local
  13    Revenue from Selling Real Power Demand via Export
  14    Revenue from Selling +ve Reactive Power Demand to Local
  15    Revenue from Selling -ve Reactive Power Demand to Local
                                                                                    As part of an on-going research and development study, the
  16    Revenue from Selling +ve Reactive Power Demand via Export               backup reserve and wheeling pricing algorithm is currently being
  17    Revenue from Selling -ve Reactive Power Demand via Export               implemented on a portion of the SEC vast power grid as shown
  18    Revenue from Selling Real Power Reserve                                 in Figure 1. The power system consists of two main regions,
  19    Revenue from Selling +ve Reactive Power Reserve                         namely the Central region and the Eastern region. The two
  20    Revenue from Selling -ve Reactive Power Reserve
  21    Revenue from Fees for Wheeling Demand Power (Grid Only)
                                                                                systems are interconnected through two 380 kV and one 230 kV
  22    Revenue from Fees for Wheeling Reserve Power (Grid Only)                double-circuit lines. Three zones are identified in the present
  23    Cost to Bus / Revenue to Grid for Bus Contribution to Losses            analysis, two in the Central region (Riyadh and Qassim zones)
  24    Total System Losses Supplied by Slack Bus                               and one in the Eastern region. One large customer owns several
  25    Revenue to Bus / Cost to Grid for Contribution to System Losses
                                                                                buses in the system, including buses with local generation.



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                                     CENTER
                                                                                                                             EAST




                                                          Fig. 1 Implementation portion of SEC power grid




                    V. ILLUSTRATIVE EXAMPLE                                               The backup reserve and wheeling pricing model contains
                                                                                     two owners (entities), namely the “company” and the
    This section presents a sample demonstrative application of                      “customer”. Each entity owns one generation bus and one
the developed pricing model. Figure 2 shows the sample network                       demand bus. The company also owns the power grid. The
representation used, which represents a reduced system model of                      customer generation bus 1 supplies a local demand of 32 MW
a practical power system.                                                            and takes care of its required reserve. In addition, firm and
                                                                                     reserve power is wheeled to the customer-owned demand bus 2.
                            Pg (3)                                                   Part of the surplus generation capacity at bus 1 is exported to the
                            Qg (3)
                                                                                     grid as both firm and reserve power. The grid, in turn, sells the
                                              BUS
                                                                                     needed firm power and reserve to the demand buses in the
                                                                                     system.
       BUS            y13
                                                                                          The levelized capacity costs at buses 1 and 3 are assumed as
                                                                    BUS              0.1 and 0.05 MSR/PU (Million Saudi Riyals per MW),
                                                                          Pd (2)
                                        Y34                               Qd (2)
                                                                                     respectively, which represents the annual charges over facility
                                                                                     life-years, calculated using the associated capital recovery
                                                    y24
   Pg (1)                      Y14                            Y20                    factors. The local reserve requirement for all demands is assumed
   Qg (1)
   Pd (1)                                                                            as 10% under normal operating conditions and 5% under
             Pwd (1 ? 2)
   Qd (1)
             Pwr (1 ? 2)
                                                                                     emergency conditions. For the specific pricing scenario
                                                    Pd (4)                           considered, the power company offers the firm and reserve
                            BUS                     Qd (4)
                                              Y40                                    power to the customer demand at 0.7 and 0.14 MSR/PU,
                                                                                     respectively. For this particular pricing scenario, the same rates
                                                                                     are assumed to be charged by the customer for export firm power
             Fig. 2 Implementation portion of SEC power grid                         and reserve to the grid. At the same time, the customer wheels



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 Proceedings of the 14th International Middle East Power Systems Conference (MEPCON’10), Cairo University, Egypt, December 19-21, 2010, Paper ID 214.

7% of the required demand (38.2 MW) at bus 2 from its plant at                order to fairly model various power exchange scenarios, in which
bus 1 at a wheeling rate of 0.25 MSR/PU paid to the grid. Table               major consumers buy from SEC as well as sell to surplus power
V summarizes the overall results for this hypothetical pricing                from their local generating facilities. Such balanced strategy
scenario, where costs and revenues are in MSR. In Table V,                    should ensure perceived benefits to both the buyer and the seller.
Owners 1, 2 and 99 represent, respectively, the customer, the                 The practical implementation features of the computerized
company and the grid. The results of the table show, for this                 algorithms and the associated simulation software were discussed
assumed pricing scenario, that both the customer and the grid                 in the paper in regard to both backup reserve and wheeling
incur losses while the company gains about 9.3% profit. Of                    pricing evaluation. An illustrative case example was also
course, for a more balanced pricing strategy, the assumed cost                presented for demonstration purposes. The application scenario
and revenue parameters associated with firm and reserve power                 showed that the negotiated pricing coefficients play a crucial role
purchase and export will have to be revised via negotiations                  in the overall cost-revenue pattern for the owners. In order to
between various market entities. This application scenario                    attain a balanced pricing strategy for all owners, a well-designed
demonstrates clearly that the negotiated pricing coefficients play            set of agreed-upon price coefficients will have to be established
a crucial role in the overall cost-revenue pattern for the owners.            for firm and reserve as well as wheeled power associated with
As is expected, the bulk of the costs and revenues in Table V are             both purchase and export activities among various owners in the
associated with firm power purchases and exports. The portions                electricity market.
associated with reserve transactions for this case scenario are
shown in Table VI.
                                                                                                        ACKNOWLEDGMENT
                              TABLE V
OVERALL COST-REVENUE RESULTS OF ILLUSTRATIVE SCENARIO                             This work was supported by the Saudi Electricity
                                                                              Company (SEC) which funds the SEC Chair in Power System
 OWNER        COSTS         REVENUES         PROFIT         %-PROFIT          Reliability and Security.
   1        40.397039       35.248000      -5.149039       -14.6
   2        124.875812      137.698378     12.822566       9.3
    99      111.306378      81.374725      -29.931653      -36.8
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which some of its major industrial consumers are in a position to
offer and compete for surplus generation as well as request                   [10]   E. Handschin, L. Muller, T. Nikodem and R. Palma, "Comparison of
                                                                                     pricing methodologies for wheeling transactions in liberalised energy
wheeling of firm power and/or reserve among their local                              supply systems," Proc, DRPT 2000. International Conference on
facilities using the main grid. Because SEC also owns the power                      Electric Utility Deregulation and Restructuring and Power
grid, a balanced pricing strategy is of an extreme importance in                     Technologies, 2000, pp. 528-531.




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