Planning Studies for Connection of 500 MW Photovoltaic Power Plant to Oman Grid at Ibri

Transcription

1 Helwan University From the SelectedWorks of Omar H. Abdalla November 11, 2018 Planning Studies for Connection of 500 MW Photovoltaic Power Plant to Oman Grid at Ibri Hisham A. Al-Riyami Adil Al-Busaidi Ahmed Al-Nadabi Musabah N. Al-Sayabi Omar H. Abdalla Available at:

2 Planning Studies for Connection of 500 MW Photovoltaic Power Plant to Oman Grid at Ibri H. A. Al Riyami 1, A. G. Al Busaidi 1, A. A. Al Nadabi 1, M. N. Al Sayabi 1, A. S. Al Omairi 1, & O. H. Abdalla 2 1 Oman Electricity Transmission Company (Sultanate of Oman) 2 Helwan University (Egypt) Summary: The paper presents techno-economic studies for connecting a 500MW Photovoltaic (PV) power plant to the Main Interconnected Transmission System (MITS) at Ibri. The objective is to justify the required capital expenditure on the basis of the submission of a full, complete and robust study report insuring the transmission system in Oman is planned, developed and operated in an efficient manner. Three connection options are proposed and compared considering cost, compliance with the Security Standard, technical performance, deliverability, environmental conditions, flood risk assessment and safety. The MITS models of 2020 and 2021 have been updated to include the simulation of the alternative connections of the 500MW PV power plant. The DIgSILENT PowerFactory professional software is used to perform system analyses for different cases. The solar PV technology and components are discussed. The MITS description and is presented. Steady-state analyses; including power flow, 3-phase short-circuit, 1-phase short-circuit and contingency are presented. Transient analyses; including system responses to line fault and generator outage are presented. Keywords: Ibri Solar Power Plant, MITS, Photovoltaic. 1. INTRODUCTION There has been a considerable interest in renewable energies over the world in recent decades. Oman Electricity Transmission Company (OETC) has received a connection application from Oman Power and Water Procurement Company (OPWP) [1] for connection of a 500 MW Photovoltaic (PV) power plant to the Main Interconnected Transmission System (MITS) at Ibri. The target date of the PV power plant connection is 1 st of December 2020 and the scheduled commercial operation date is June In order to meet the Transmission Licence Conditions 8, 23 and 26 [2] and mitigate any risk associated with non-compliance of these obligations, OETC has to prepare a Pre-Investment Appraisal Document (PIAD) including technical and economic studies to assess a number of available connection options and recommend the most financially and technically suitable solution [3, 4]. The following three proposed options have been assessed and compared: Option 1: 132 kv connection by LILO of Ibri- Dank Line. Option 2: 220 kv direct connection to Ibri IPP grid station. Option 3: 400 kv direct connection to Ibri IPP grid station. The preferred option providing a technically viable, deliverable and financially preferable solution is Option 2: the construction of a 220 kv double circuit connection from Ibri Solar Power Plant to Ibri Independent Power Plant (Ibri IPP). This solution allows new generation at Ibri Solar Power Plant to supply local loads in the Ibri area with a parallel connection into the wider 400 kv network to New Izki. Furthermore, the selected option aligns with the OETC master plan ( ) [5]. The preferred option presented a lower lifetime cost (on an NPV basis), lower losses, higher technical performance and a more deliverable solution.

3 Figure 1: The MITS of Oman in The paper is organized as follows: Section 2 describes the existing transmission system in Oman. Section 3 provides a brief description of the PV Power Plant concept. Section 4 presents Ibri generation site and surrounding transmission assets. Section 5 presents the technical and economic studies of connecting Ibri IPP to the MITS and provides a comparison of the options. Section 6 presents full technical and economic studies of the preferred connection option. Section 7 summarises the main conclusions of the paper. 2. SYSTEM DESCRIPTION The existing transmission system in northern Oman has three HV operating voltages, i.e. 400 kv, 220 kv and 132 kv while in Dhofar 132 kv is employed. The transmission system extends across the whole of northern Oman and interconnects bulk consumers and generators of electricity located in the Governorates of Muscat, Batinah South, Batinah North, Dhahirah, Buraimi, Dakhliyah, Sharquiya South and Sharqiya North as shown in Figure 1. The present OETC transmission system of the MITS consists of [6]: circuit-km of 400 kv overhead transmission lines circuit-km of 220 kv overhead transmission lines circuit-km of 132 kv overhead transmission lines 75.1 circuit-km of 220 kv underground cables circuit-km of 132 kv underground cables 9750 MVA of 400/220 kv transformer capacity MVA of 220/132 kv transformer capacity 570 MVA of 220/33 kv transformer capacity MVA of 132/33 kv transformer capacity 150 MVA of 132/11 kv transformer capacity Three 400/220/132/33 kv grid stations Two 400/220 kv interconnection grid stations Three 220 kv interconnection grid stations Six 220/132/33 kv grid stations Two 220/132 kv grid stations Two 220/33 kv grid stations Fifty Three 132/33 kv grid stations One 132/11 kv grid station In addition, the present OETC transmission system at Dhofar consists of [6]: circuit-km of 132 kv overhead transmission lines circuit-km of 132 kv cables 2062 MVA of 132/33 kv transformer capacity Eight 132/33 kv grid stations 3. PHOTOVOLTAGE POWER PLANT A photovoltaic system is a green power source, which converts sunlight directly to electricity. The main advantages of the PV system are that it requires

4 no fuel, produces no emissions, and involves no moving parts. Figure 2 shows the main components of a PV power plant. It consists of a large number of solar arrays, DC/DC converters, DC/AC inverters, filters, and step up transformers. DC/DC Convert er DC/AC Inverter Grid Figure 2: Main components of a PV power plant. A solar PV module, which consists of a number of solar cells, produces only a small amount of current and voltage. In order to produce a large amount of electric power, the solar cell modules are connected into arrays. The output voltage from a PV array changes with solar radiation and ambient temperature. In order to connect the PV system to the transmission grid, the output DC voltage from PV system should be first regulated by a DC/DC converter and then converted to AC voltage source by a DC/AC inverter. A filter is used to eliminate harmonics. The power electronic components (DC/DC converter, DC/AC inverter, and filter) have the tasks to guarantee safe and efficient operation, to track the maximum power point tracking of the PV system, and to maintain power quality of the PV system output. 4. IBRI IPP GENERATION SITE AND SURROUNDING MITS ASSETS The Ibri Solar IPP site is proposed to be located approximately midway between the towns of Ibri and Dank (see Figure 3). Nearby there exists a 220 kv double-circuit OHTL which terminates at Ibri from Mahadha in the north (~150 km total length). In parallel to this, a 132 kv network extends from Ibri to Mahadha via Dank and Wadi Sa a (see Figure 1). These 132 kv circuits also continue from Ibri to the east towards Izki. Also, there is 400 kv double-circuit line connected between Ibri IPP grid station and New Izki grid station (~264 km total length). There is a designed 400 kv overhead line but currently operated at 220 kv; it is under construction between Sohar-3 IPP via SFZ and Mahadh and is expected to be completed by end of July Mahadh is connected to the UAE grid and Ibri IPP via a double-circuit 220 kv overhead line. Therefore, the evacuation corridors of the generated power at Ibri area will be via the 400 kv system towards Izki and Misfah and via 220 kv system towards Mahadh and consumed locally at Ibri through the 220 kv and 132 kv systems in Ibri, Dreez, Dank and Heyal grid stations. Figure 3: Ibri generation site With reference to the Annual Five Year Capability Statement 2018 [6], it is expected that new 400 kv double circuit lines from Ibri to New Izki (under construction June 2018 expected completion date), and 400/220 kv with 3x500 MVA transformers (already Energized). Additionally, the ongoing project of construction 400 kv double circuit lines from New Izki to Misfah is expected to be completed by the end of March New 400 kv lines to SFZ and Mahadh grid stations are construction. Figure 4 shows the forecasted peak demand growth against the net maximum generation export in the area (substations along the corridor from Mahadha in the north to Nizwa in the south). 5. TECHNICAL AND ECONOMIC EVALUATION OF OPTIONS Three options have been considered to mitigate the risks associated with non-compliance of License Conditions 8, 23 and 26 [2]. These options are summarised as follows: Option 1: 132 kv connection by LILO of Ibri- Dank Line. Option 2: 220 kv direct connection to Ibri IPP grid station. Option 3: 400 kv direct connection to Ibri IPP grid station. Each of these options is assessed on the basis of the following performance considerations: i. Deliverability All the associated circumstances on every option have been assessed on term of circuit routes, grid station location etc.

5 Peak Demand VS Net Generation Year MW Net Generation Peak Demand Figure 4: Peak demand and net generation forecast in study area. ii. TSS Compliance The Transmission Security Standard has been prepared in accordance with Condition 26 of OETC's Transmission and Dispatch Licence [2]. OETC implements the TSS for the planning and operation of its licensed transmission system. iii. Capital cost Cost of every asset and civil works cost on every options have been be calculated thoroughly. iv. Net Present Value (NPV) The net present value is calculated for every option for 40 years. v. Environmental considerations As OETC is an ISO (EMS) Environmental Management System certified company, it is committed toward environment so all the environmental impacts of every project are considered. vi. Flood risk assessment OETC maintains a check list that considers the location of all assets associated to every option to the nearest flood or valleys. vii. Safety As OETC is an ISO (OHSAS) Occupational Health and Safety Assessment Series certified company, it is committed toward safety so all the safety impacts of every project are considered. viii. Comparison of options Table I provides a comparative summary of the options based on the key aspects assessed including financial, technical performance, deliverability, environmental considerations including Flood Risk Assessment (FRA) and safety aspects. Colour coding is provided for visual reference such that green indicates no issues, yellow indicates feasibility but with some additional considerations, red indicates a non-feasible aspect which prevents the option from being considered further and black notes items in nonfeasible options that have not been fully assessed due to a prior limitation. As summarised in Table I, Option 1 is deemed not feasible as a result of significant overloads seen under (N-1) assessments across a range of outage conditions and therefore non-compliant with the OETC TSS and subsequent Licence Condition 26. This option is therefore not considered further, leaving Option 2 and Option 3 as the remaining feasible options. While both options 2 and 3 are having almost similar technical performance, then the main factor for comparison is the capital cost for the present and future solar expansion. A summary of Option 2 and Option 3 and the relative merits of each are subsequently provided below: Option 2 This option presents the least cost lifetime cost solution with regard to capital cost by minimising any new 400 kv infrastructure and utilising the 220 kv voltage level. It is proposed that the 220 kv overhead lines be constructed for a length of 3 km. It also complies with the TSS requirements. In addition, option 2 has lower power losses in comparison with option 3. Furthermore, option 2 incurs lower capital cost by about two million for the present connection of Ibri Solar-PV power plant and also lower capital cost by about one million for future solar expansion if required.

6 Table I: Comparison of options Technical Performance Capital Cost [R.O.] Option 1 Option 2 Option 3 8,284, ,197, NPV -29,463,075-33,448,649 Future Solar Expansion Cost 1,354,497 2,202,375 Intact TSS Violation (Loading Issue) No issues No issues N-1 TSS Violation (Loading& Supply lost Issues) No issues No issues N-M-1 No issues No issues Short Circuit No issues No issues Losses (2022 Peak) High losses (51MW) Lower losses (32.13MW) Medium losses (33.03MW) Deliverability LILO of the 132kV OHL will required long Shutdown and proper coordination to secure power supply to Dank and Yanqul areas - Crossing rail way route - Securing new OHL route - Crossing rail way route - Securing new OHL route Environmental No issues No issues No issues FRA Low risk Low risk Low risk Safety Has medium risk dealing with existing OHL diversion Has medium risk by working in live system at Ibri IPP GS Has medium risk by working in live system at Ibri IPP GS Option 3 This option results in a greater capital cost due to the establishment of a 400 kv substation at Ibri Solar- PV PS with associated 400 kv OHL and additional two 400 kv bays at Ibri IPP substation. Moreover, the future solar expansion will entails higher capital cost compared to option 2. Furthermore, it has higher loss compared to be option 2. Based on the comparison of the options presented above, it is clear that option 2 represents the technically preferred long term solution whilst providing the lowest lifetime cost with minimised deliverability risks. Subsequently, option 2 is recommended for the connection of the proposed Ibri Solar-PV IPP generator. ix. Dynamic studies Subsequently, dynamic studies of the preferred option (option 2) relating to a close and remote three phased fault of one of the 220 kv lines from Ibri Solar-PV PS to Ibri IPP have been conducted. Also, a Solar-PV PS trip at Ibri have been conducted and the results are presented. The studies have been completed for peak and off peak demand conditions. It is concluded that there are no issues to report with regard to the dynamic assessment with all generators in MITS remaining stable under the conditions assessed. 6. PREFERRED CONNECTION OPTION A. Configuration Figure 5 shows the location of Ibri Solar power plant with option 2 connection. Figure 6 shows a simplified connection of Option 2. This preferred option mitigates the licence condition risks whilst providing a technically viable, deliverable and financially preferable solution through the construction of a 220 kv double circuit connection for a length of 3 km from Ibri Solar-PV IPP to Ibri IPP station. The solution allows new generation at Ibri Solar-PV power plant to supply local loads in the Ibri/Nizwa area with a parallel connection into the wider 400 kv network to Misfah, Izki and Mudharib. Figure 5: Location of Ibri 500 MW power plant

7 Figure 6: Simplified configuration of Option 2. B. Works and Equipment The outline specification of the works associated with the preferred option is as follows: Establish 220 kv switchgear (GIS) in Ibri Solar-PV PS Substation 2 x 220 kv GIS: unit incomers 4 x 220 kv GIS: two bus section and two bus coupler 2 x 220 kv GIS: outgaining feeders Associated civil, auxiliary and infrastructure works to support the above equipment 2 x 220 kv GIS as feeder incomers at Ibri IPP substation with associated protection and civil modification. 3 km 220 kv twin Araucaria overhead line double circuit from Ibri Solar-PV IPP to Ibri IPP grid station. 500 m, 220 kv, 2500 mm 2 XLPE cable between the gantries to the 220 kv GIS at Ibri IPP station. This option 2 is capable to cater for the future solar expansion in Ibri area with additional investment but with lower cost in comparison with option 3. It is recommended that the works are carried out in time for meeting the proposed schedule commercial operation date of June 2021 to ensure compliance with OETC licence conditions. Maximum export of 500 MW for the Ibri Solar-PV IPP generator is expected in June C. Cost The chosen option aligns well with the OETC principles of developing the Oman electricity transmission system in a cost effective manner whilst providing a secure and reliable service to customers in compliance with statutory requirements (i.e. the Oman Grid Code, Transmission Licence, etc.). The preferred option provides lower lifetime cost (on NPV basis), lower losses, higher technical performance and a more deliverable solution. The estimated capital cost for connection of the Ibri IPP to the MITS is R.O. 8,284, The requested funding will be distributed over five years as follows: 2018 R.O. 1,656, R.O. 2,899, R.O. 2,899, R.O. 828, D. Deliverability This option would require the delivery of a new 220 kv specification double circuit line for a length of

8 approximately 3 km. Initial site surveys have been conducted and indicated that there is scope to acquire a suitable right of way to allow this development. Also, the rail route is passing in between the Ibri Solar-PV and Ibri IPP sites which shall be considered during the OHTL design. However, at this time the survey has indicated that the use of overhead line throughout the route length should be feasible. E. Technical Performance A digital model of the MITS has been developed [9] using the DIgSILENT professional software [10]. The model has been updated to accommodate new assets to be added in studied years (2021). The following simulation studies have been performed to assess the technical performance of the MITS with Option 2 of Ibri Solar IPP connection. Intact Conditions Tables II show power flow results at peak demand condition after adding the Ibri IPP in Although Ibri IPP and Ibri Solar-PV IPP physically are in one site and Ibri Solar is connected through 3 km of 2 x 220 kv OHTL to Ibri IPP 220 kv BB, but electrically they have a common connection point. Therefore, it looks like one generation site with approximately 2039 MW (500 MW Solar plus 1539 MW Ibri IPP). Since the connection of the Solar-PV IPP under this option is via the 220 kv, the flow from 400 kv Ibri IPP GS to Ibri load group decreases and the majority of the Ibri IPP power is now exported by the 400 kv lines in the direction of New Izki and Misfah areas around 1072 MW compared to MW prior the connection of the Solar-PV IPP. Thus, there is no concern for the out of frim loading of the 3x500 MVA, 400/220 kv transformers at Ibri IPP. However, the risk of the out of firm loading is cascaded to the 220/132 kv, 2x500 MVA transformers at Ibir grid station where the loading reached 56.18%. However, it should be highlighted that the loading of these transformers is not mainly driven by the connection of Ibri Solar-PV IPP rather than the load growth in Ibri area where their loading before the connection of the Solar-PV IPP was 47.91%. However, tripping any of these transformer has not resulted in overloading of the second transformer and therefore comply with TSS requirement. The other lines and transformers at Ibri network are well within the standard limits. The loading of the 2 x 220 kv line between Ibri IPP to Ibri grid stations is 41.74% which is very well within the firm capacity. With respect to the voltage profile for Ibri network area at different voltage levels 400 kv, 220 kv and 132 kv, it shows acceptable voltage profile and no voltage violation has been detected for the system peak condition. (N-1) Contingency Conditions A loss of one of the 400 kv lines to New Izki results in small impact on the remaining network with flows seen to be in line with intact conditions (with exception to the second 400 kv line which is now loaded to 41.62%). Similarly, a loss of one of the 220 kv lines to Mahadha also results in small impact on the remaining network. Subsequently, a loss of one of the 220 kv circuits from the Ibri IPP substation to the Ibri 220/132 kv substation results in other circuit loading to 77.48%. Furthermore a loss of one of the 220/132 kv transformers results in loading of the remaining transformer to 96.66% which complies with TSS criteria. Therefore, a third transformer may be will required in the future considering the load growth of the area which is subject to another assessment. Moreover, losing one of the 3 x 400/220 kv transformers at Ibri IPP station has no major impact as the Solar-PV IPP connection is at 220kV system and no violation has been observed. Additionally, a loss of any of the 132 kv circuits in the Ibri to Jebreen corridor results in loading of the remaining circuit (up to 46.67%). Finally, from voltage profile perspective, the most credible scenario that has the highest voltage changes is the loss of one of the 220/132 kv transformers at Ibri grid station. However, the drop of voltages were within the acceptable limits, where the lowest voltages were ( pu) noted at Dreez, Hayel and Jebreen stations of as shown in Table II. From the above assessment it is clear that Option 2, with connection arrangement does meet OETC TSS requirements under (N-1) condition. This option is therefore deemed feasible on the grounds of OETC TSS compliance. (N-M-1) Contingency Conditions (N-M-1) conditions relate to a forced outage occurring during the periods of low demand, when another asset is already out for maintenance. The network configuration for the (N-M-1) study reflects the maintenance period (usually in winter) when the OETC TSS requirements such that all 33 kv (and below) connected loads are reduced to 67% of peak demand unless realistic data is available, whilst direct connected customers to transmission customers remain at peak demand values. As the assessment focus of this PIAD is the connection of Ibri Solar-PV PS, it assumed to operate at its maximum output 500

9 MW to reflect the most challenging operation case. Therefore, the connection arrangement that being assessed must be capable to cater for full power evacuation under the (N-M-1) condition whilst Ibri IPP is dispatched in practical manner similarly to other generation in the transmission network. Therefore, the total generation at Ibri in this case is 892 MW (500 MW Solar plus 392 MW Ibri IPP). The above arrangement provides a suitable network configuration to allow the (N-M-1) studies to be conducted, representing a reduced load scenario in line with OETC TSS requirements (and practical network loadings in the maintenance period) in addition to a practical generation dispatch whilst maintaining a maximum output of Ibri Solar-PV IPP. Sur gas turbines, as the reference (swing bus) machines, are seen to be at 54% output under this arrangement, indicating a practical balance of generation and demand. Further (N-M-1) contingency analysis indicated no voltage constraints based on this connection arrangement as the load during the maintenance period is low. Short Circuit Levels Three-phase and single-phase to ground intact system short circuit system levels (all generators on to provide worst case assessment) have been calculated (according to the IEC 60909) and are measured against equipment ratings for relevant substation locations in the vicinity of the new Ibri Solar IPP. Table II: Branch power flow and voltage profile (2021) Peak System Case Loading % N N-1 Condition Condition Conditions 220 kv OHL 400 kv OHL 220 kv 220 kv OHL Intact Lines / Scenarios Ibri Solar- Ibri IPP- OHL Ibri Ibri IPP- System Ibri IPP New Izki IPP-Ibri GS Mahadha 220kV OHL Ibri Solar-Ibri IPP 400kV OHL Ibri IPP-New Izki 220kV OHL Ibri IPP-Ibri GS 220kV OHL Ibri IPP-Mahadha 132kV OHL Ibri GS-Jebren 3x500MVA (400/220kV) Tx Ibri IPP 2x500MVA (220/132kV) Ibri GS Peak System Case Voltage Profile (pu) 220kV Ibri Solar BB 132 kv OHL Ibri GS-Jebren 2x500 MVA (220/132kV) Ibri GS kV Ibri IPP BB kV New Izki BB kV Ibri IPP BB kV Ibri GS BB kV Mahadha GS BB kV Ibri GS BB kV Jebreen GS BB kV Al Hayl GS BB kV Dreez GS BB

10 Table III shows a sample of the calculated short circuit currents of 2022 system condition. These and fault currents at other busbars are within the corresponding thermal busbar fault levels. Bus Bars Table III: Short circuit levels Short Circuit Rating (ka) 3-Ph (ka) 1-Ph (ka) 400kV Ibri IPP BB kV Ibri IPP BB kV Ibri GS BB kV Ibri GS BB Losses Real power losses at 2019 peak demand have been calculated for this option to be included in the lifetime cost assessment and as a comparison to other feasible options. The real power losses have been calculated for the network in the vicinity of the Ibri IPP which is directly impacted by the additional generation. Broadly this relates to the 400 kv network from Ibri to Izki, the 220 kv network to Mahadha from Ibri, the 132 kv network from Ibri to Al-Hayl and Nizwa in addition to relevant transformers at these locations. After the connection of the Solar-PV power plant, the transmission losses have increased from MW to MW. The major losses increase is observed in the 400 kv line, the 220 kv line to Mahadha and 132 kv to Jebreen. This is because, the majority of generated power (around 1072 MW) of Ibri IPP is transmitted to Izki and Misfah areas via the 400 kv and 338 MW flow to the direction of Mahadha GS via the 220 kv line. In addition, the power flow towards Jebreen and Nizwa GSs has increased causing more power losses in the long 132 kv lines. The losses are dominated by the 220 km 400 kv overhead line from Ibri IPP to Izki grid station with losses of 18.8 MW. F. Financial Assessment The capital cost assessment of this option in full, including five year spend phasing, and can be summarised as a total cost of R.O. 8,284, The NPV assessment of the option which accounts for lifetime costs associated with losses and estimated operations and maintenance costs over a 40 year period. The resulting NPV is R.O. -29,463,075. G. Environmental Considerations Initial site surveys have been conducted which suggest there is scope to obtain a suitable corridor for the new circuit. Furthermore, it is assumed at this time that overhead line can be utilised for the entire route length. Therefore, there are limited unknown environmental concerns at this time. H. Flood Risk Assessment A flood risk assessment for the Ibri Solar IPP power station has been conducted with full details. The assessment has illustrated that there is no significant flood risk associated with this development. I. Safety There is no significant safety considerations associated with Option 2. The new line will be constructed in a new line corridor, offline and away from other live infrastructure. J. Dynamic Studies The compliance with TSS requirements has been assessed by steady state and dynamic studies for both peak and off peak demand with full evacuation of Ibri Solar IPP. The dynamic studies cover the rotor angle stability, voltage response and frequency response at both peak and off peak demands. Samples of the dynamic studies are presented here. Figure 7 shows the frequency response to a three phase short-circuit cleared in 120 ms (at the 220 kv line between Ibri Solar-PV and Ibir IPP GS), at peak demand. Figure 8 shows the frequency response to tripping the 500MW Solar PV power plant. 7. CONCLUSION This paper describes the assessment for each option from different aspects, technically, financially and risk of deliverability of the Ibri Solar IPP connection project. The assessment of each option has been carried out on the basis of the following performance considerations: deliverability, Transmission Security Standard (TSS) compliance technical performance, capital cost, net present value, environmental considerations, safety and flood risk assessment. Power losses have also been considered in the NPV calculation. In addition, the paper describes the optimal generation connection design that is respected the TSS criteria. The compliance with TSS requirements has been proved by steady state and dynamic studies for both peak and off peak demand with full evacuation of Ibri Solar IPP power plant. The preferred Option 2 has shown to mitigate the licence condition risks whilst providing a technically viable, deliverable and financially preferable solution. It consists of construction of a 220 kv double circuit

11 connection from Ibri Solar IPP to Ibri IPP grid stations. The NPV assessment of this option which accounts for lifetime costs associated with losses and estimated operations and maintenance costs over a 40 year period. The resulting NPV of this option has been calculated to be R.O. -29,463, REFERENCES [1] OPWP: Seven Year Statement ( ), [2] OETC: Transmission and Dispatch Licence, 2016, [3] OETC: PIAD for Connection of Ibri IPP Generator Project, Ref: 51/2018, [4] OETC-AMP-P-SOP-M-007 Preparing PIADs, [5] H. Al-Riyami, O. H. Abdalla, A. Al-Busaidi, A. Al-Nadabi, M. Al-Siyabi, M. Al-Abri, Z. Al- Rawahi, J. Dubois, V. Lambillon, Sh. Mirza, and A. Bastens: Development of Transmission System Master Plan of Oman ( ), Paper No. A036, GCC Cigre 2014, Al- Manamah, Bahrain, November [6] OETC: Five Year Annual Transmission Capability Statement ( ), [7] OETC: The Grid Code, Version 2, April 2010, [8] OETC: Transmission Security Standard, July 2016, [9] O. H. Abdalla, H. Al-Hadi, and H. Al-Riyami: Development of a Digital Model for Oman Electrical Transmission Main Grid, Proc. of the 2009 International Conference on Advanced Computations and Tools in Engineering Applications, pp , Notre Dame University, Lebanon, July, 2009, [10] DIgSILENT 2016 Technical Reference [Hz] [s] 132kV Al Kamil BB: Electrical Frequency 132kV Manah BB: Electrical Frequency 220kV Airport Height BB: Electrical Frequency 220kV Barka PS BB: Electrical Frequency 220kV Barka-3 PS BB: Electrical Frequency 220kV Ibri IPP BB: Electrical Frequency 220kV Sohar-1 PS BB: Electrical Frequency 220kV Sohar-2 PS BB: Electrical Frequency 400kV Ibri IPP BB: Electrical Frequency 400kV Misfah BB: Electrical Frequency 400kV New Izki BB: Electrical Frequency 400kV Sohar-3 IPP BB: Electrical Frequency 400kV Sur PS BB: Electrical Frequency 132kV Rusail Industrial BB: Electrical Frequency Figure 7: Frequency response, at peak demand, to a three phase short of 120 ms, at.

12 50.01 [Hz] [s] 132kV Al Kamil BB: Electrical Frequency 132kV Manah BB: Electrical Frequency 220kV Airport Height BB: Electrical Frequency 220kV Barka PS BB: Electrical Frequency 220kV Barka-3 PS BB: Electrical Frequency 220kV Ibri IPP BB: Electrical Frequency 220kV Sohar-1 PS BB: Electrical Frequency 220kV Sohar-2 PS BB: Electrical Frequency 400kV Ibri IPP BB: Electrical Frequency 400kV Misfah BB: Electrical Frequency 400kV New Izki BB: Electrical Frequency 400kV Sohar-3 IPP BB: Electrical Frequency 400kV Sur PS BB: Electrical Frequency 132kV Rusail Industrial BB: Electrical Frequency Figure 8: Frequency response, at peak demand, to tripping the 500 MW Solar-PV power plant.