Network Integration of Distributed generation IPSA report

Alex Maclean

Distributed generation study

03/06/2010

Distributed Generation Connection and Operation Feasibility and Design Study Alex Maclean

Alex Maclean


03/06/2010

ContentsI. Abbreviations..............................................................................................................2 II. Executive summary ..................................................................................................3 III. Load Data and Network Model................................................................................5 IV. Options to be investigated........................................................................................8 V. Option A: Fit and Forget...........................................................................................9 VI. Option B: Reactive power compensation.................................................................9 VII. Option C: DNO co-operation................................................................................11 VIII. Option D: Active network management. ............................................................15 IX. Assessment of options............................................................................................16 X. Recommendation.....................................................................................................20 XI. Web Based Grid Connection Tool ........................................................................20 XII. Appendix A...........................................................................................................21 XIII. Appendix B Load Flows...................................................................................22 XIV. Appendix C Fault Levels.................................................................................26 XV. Appendix D Losses............................................................................................29 XVI. Appendix E Other............................................................................................31 XVII. Appendix F Financial Assessment..................................................................32

I. AbbreviationsAAAC All Aluminium Alloy Conductors ACSR Aluminium Conductor Steel Reinforced DNO Distribution Network Operator DG Distributed Generation FACTS Flexible AC Transmission System IPSA Interactive Power Systems Analysis MSC Mechanically Switched Capacitor NEDL Northern Electric Distribution Ltd OHL Overhead Line Ofgem The Office of Gas and Electricity Markets pu Per Unit TCSC Thyristor Controlled Series Capacitors GDUoS Generation Distribution Use of System

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II. Executive summaryThis is a report on the feasibility of connecting a wind farm to the grid for a client, the factory owner. The capacity of the wind farm would be as large as is feasible considering the network limitations. The report will detail the network in question, the clients needs and site, the options available, an investigation into the costing of each option and a recommendation of which option to take. The options of grid connection will be assessed on the basis of the grid assets thermal capacities and Fault Levels in the network as well as how the options compare to each other financially. Only single line diagrams have been used in this study. The available options for connecting to the grid are as follows: Option A: Fit and forget, no DNO co-operation. Option B: Reactive power compensation. Option C: DNO co-operation, upgrading current assets. o Add a 2nd Line to Feeder 1. o Replace line in Feeder 1. o Install a dedicated 33kV line. Option D: Active network management. The results of assessing the network showed that there was a significant capacity (6.8 MW) for connecting to the local network without upgrading the network . Using local reactive power compensation, this reached a maximum of 7.05 MW. By installing a second line alongside the first in feeder 1 this capacity was further increased to 13.7 MW, replacing the line entirely allowed 35 MW to be connected. Using a dedicated 33 kV line the highest capacity was reached at 49 MW. By controlling the low priority loads in the network by Demand side management the capacity of Option B was increased to 7.9 MW. All these options and their associated Financial returns are detailed in the table below.Fit & Forget + TCSC 7.05 MW 8,588,09 6 5 42,215,5 64 492% DNO Add 2nd line 13.7 MW 16,667,4 88 5 79,241,7 52 475% DNO Replace Line 35 MW 42,274,5 31 5 197,307, 469 467% Dedicate d 33kv line 49 MW 62,648,0 62 7 176,933, 938 282%

Fit & Forget Installed Capacity Total Initial Investment No. Years Payback Total Lifetime Profit Return on 6.8 MW 6,732,0 00 5 33,620, 160 499%

Active Network 7.9 MW 10,706,608 5 46,645,472 436%

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III. Load Data and Network ModelThe clients site is situated near an existing factory also owned by the client. The factory is connected via a Busbar to an 11kV radial feeder, the factory also has four 250kW backup diesel generators for emergency power supply, these can be assumed to connect to the same Busbar as the factory load. The network has been modelled on IPSA and is shown in Error: Reference source not found.

Clients Site

Figure 1 - Network Model

Next to the factory is a village which is also connected to the Grid at the same Busbar. This Busbar is supplied by an 11kV line which in turn is connected to the 33kV transmission system via a transformer. This transformer is rated at 50MVA but in reverse can only operate safely at 66% of the rated power i.e. 33MVA. Connected to the same transformer are two other radial feeders supplying power to an industrial estate and a Theme Park. A model of this network can be seen in figure 1. The existing loading on the network has been supplied by the DNO is displayed in Table 1. The network is assumed to be sufficient to cope with the Maximum given loading.

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Min Load Real (MW) Factory Load Village Load Industrial estate Theme park 0.4 0.135 1 1.5 Reactive (MVar) 0.3 0.065 0.2 0.25Table 1 - Network Loading

Max Load Real (MW) 1.6 0.405 5 5 Reactive(MVar) 1.2 0.196 1 1.8

In Error: Reference source not foundError: Reference source not found the existing distribution lines (assumed to be OHL for rural) connecting the 11kV Busbar to the loads are representative of neither physical distance nor electrical distance. The electrical properties supplied mostly by the DNO are displayed in Table 2.

Resistance (pu) Feeder 1 Feeder 2 Feeder 3 33kV-Grid 0.4 0.6 0.5 1.3

Reactance (pu) 0.24 0.36 0.3 0.7

X/R Line Rating 0.6 0.6 0.6 0.5 6.6 MVA 6.6 MVA 6.6 MVA 25 MVA

Line Length 0.89 km 1.34 km 1.12 km ~10 km

Table 2 - Line properties

The Line ratings were not supplied by the DNO. Rational assumptions have been made as follows. For feeder 3 the line rating needed, under maximum loading would have to be above 5.3 MVA to ensure it would be thermally capable of carrying the given load. The NEDL employs 50 mm2 AAAC rabbit conductors with a summer thermal rating of 6.6 MVA as its standard OHLs in its distribution network[1]. It is therefore sensible to assume that all three feeders are overhead lines of the same rating, 6.6 MVA. The NEDL also employ 175 mm2 AAAC Lynx conductors in its standard 33kV distribution network, this conductor has a summer thermal rating of 25MVA[1]. It is assumed that this network also employs a Lynx conductor between the 33kV Busbar and the rest of the grid. The length of the 33kV line is estimated at 10km.

1

Grid connection analysis for Seamer Wind Farm, TNEI (for Broadview), July 2008.

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The DC resistance of a rabbit conductor is 0.5426 ohm/km[2], using the given per unit resistances of the lines on each feeder, the corresponding lengths were calculated[3] and are displayed in Table 2. The voltage in the network must not exceed +10% or -6% and the Fault levels in an 11kV network should be at maximum between 150-250MVA[4]. It is assumed that the current switch gear can cope with a fault level of 250MVA, above which it will have to be replaced. Potential for Island power system Under some of the proposed levels of generation5 reverse power flows may result. As the total maximum loads on the current local network are small, 13.3 MVA including line losses, it is a possibility that the installed wind farm could provide for all of this power demand in the event of a blackout or prolonged electrical fault. If islanding is not desired, which under normal conditions would be the case, as a result of the maximum generation being larger than the minimum load, intertripping may be required to prevent unwanted islanded operation. Factory Owners needs and site The factory owner has detailed several requirements that constrain the options available for connecting the wind farm. The first is the need for a constant electricity supply to the factory, this is the reason for the existence of the Diesel Generators shown in Error: Reference source not found. The second is the desire for the wind farm installation with the fasted pay back period. The factory owner has a budget of 20 million. The factory owners site is sufficiently large, so that an infinite wind resource can be assumed. But the factory owner does not want to have to comply with the stricter regulations of DG plants of 50 MW or greater, therefore maximum power output is limited to 50 MW. One of these regulations is fault ride through whereby the wind farm could not remove itself from the grid in an event of a fault even thought this has potential to damage the wind turbines. Of the factory load 50% if the daytime load and 30% nighttimes load is available for demand side management, i.e. is not a priority load and can be run at whatever time suits the power supply.

2 3

OMAN Cables, Overhead Line Conductors, Nov 2003 See Appendix A - Calculation of distribution line lengths Electric power systems B.M WEEDY B.J CORY See section XXX

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IV. Options to be investigatedOption A: Fit and forget This option involves no DNO intervention, it looks at how much power a wind farm could generate and supply to the grid, using the current network assets without exceeding the thermal line ratings, voltage regulations or Fault Level ratings anywhere in the grid. Option B: Reactive power compensation This option is identical to the previous one but the wind farm has its own locally installed reactive power compensation. Option C: DNO co-operation This option is really multiple options because there are numerous different connection methods available when you have the DNO co-operating with you. The following options will be investigated: 1. Adding a second line alongside Feeder 1 This will involve running another line from the Feeder 1 Busbar to the 11kV Busbar to support the first one hence effectively increasing the thermal capacity of feeder 1 to cope with the extra current. 2. Upgrading line on Feeder 1 This will involve replacing the existing line with one of a higher rating enabling larger quantities of power transfer at the same voltage. 3. Connecting to 33kV This option would run a 33kV line directly from the Wind Farm to the 33kV Busbar removing the need to limit the power output due to thermal ratings of lines. Option D: Active network management Smart Grid Using demand side management to switch non-essential loads on/off when needed to balance power supply with demand.

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V. Option A: Fit and ForgetThe basic constraints of power output in this option are the thermal line ratings, the voltage regulations and Fault Level ratings. To ensure that the installed capacity of the wind farm fits with these ratings and regulations over the range of loading scenarios it is important that the modelling is done under the worst case scenario: The worst case scenario on feeder 1 would be when the factory and village loads are at a minimum and the Wind farm is operating at its Maximum rated power, this would load feeder 1 with the largest current and cause the biggest voltage rise at the 11kV Busbar. The worst case scenario on feeders 2&3 are when they are at maximum loading as this would cause the largest voltage drop along the feeder. To make the most of the available thermal line rating, 6.6MVA, a high power quality is important. The majority of available wind turbines on the market consist of Induction Generator machines. Induction machines not only produce real power, when excited, but also consume reactive power. A series of IG Wind Turbine with a power factor of 0.85 was tested using the network model displayed above, the maximum power output of an installed plant of these wind turbines was limited to 6.8 MVA which is only 5.78MW or real power and 3.58MVars of Reactive power[6]. This is a large amount of Reactive power to be transmitting down a distribution network that is already heavily loaded. This Reactive power is reducing the maximum real power that can be transmitted, and hence sold, not to mention the extra losses it incurs in the line.

VI. Option B: Reactive power compensationLocal reactive power control removes the necessity of passing reactive power down the distribution line, leaving more room to transmit real power to the grid. Two main methods for reactive power control have been considered. The first is the use of DFIG wind turbines which have the ability to control the excitation so that they consumer negligible reactive power from the surrounding network. See Error: Reference source not found.

Figure 2 - DFIG Wind farm6

Load Flows in Appendix B Basic Fit and Forget

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The second is to install a FACTS Device, specifically a TCSC next to the wind farm to compensate for the reactive power demand. See Error: Reference source not found. The choice of a TCSC over a MSC of FACTS device has a number of advantages. The output of wind turbines varies with the wind resource, hence the reactive power demand changes proportionally. Therefore switching of capacitors, to balance reactive power supply with demand, is necessary. MSC have limitations due to moving parts, these result in slow switching frequencies and shorter switching life. In contrast the Thyristors in the TCSC can switch at very high frequencies and have much higher switch lives. The current inrush associated with an MSC reduces the capacitors life span significantly whereas the TCSC has little or no inrush of current. The capital cost and running costs due to losses are the prohibitive factor, the cost between US$60-140/kVar[7]. This corresponds to 4090/kVar. The wind farms are modelled as a negative load and a induction machine with no mechanical power. The lines in Error: Reference source not found & Error: Reference source not found are not representative of distance, all components are modelled as if adjacent to the Busbar labelled Feeder 1, the lines are draw so as to make the model clearer. The distances between wind turbines in the array are accounted for in the values of real and reactive power modelled by the negative load.

Figure 3 - Wind farm with TCSC

With either of the above options for reactive power compensation the maximum capacity of the proposed wind farm for real power output, in MW, is increased to 7.05 MW[8]. The limiting factor in both the basic Fit & Forget, the DFIG and the TCSC wind farms is the thermal rating of the line from Busbar 11kV to Busbar Feeder 1. Unsurprisingly the maximum output correspond closely to that rating (compare 6.6 MVA and 7.05MW pf ~ 1). The voltages right across the network dont go near the regulation limits even though this is the worse case scenario[8]. This suggests that significantly more power could be transmitted with only a line upgrade to the Feeder1. This is covered in the next section.

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Optimal choice of FACTS devices Lijun Cai IEEE 2009 See Appendix E Load Flows in Appendix B Fit & Forget, Reactive power compensation.

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VII. Option C: DNO co-operation1. Adding a second line alongside Feeder 1 The aim of this option is to overcome the first of the barriers which prevent us increasing the output capacity of the wind farm, namely the thermal rating of the distribution line. A second 50mm2 rabbit will be installed alongside the first this will take the total feeder rating from 6.6 MVA to 13.2 MVA. Error: Reference source not found shows the second line in the model running from the 11kV Busbar to the Feeder 1 Busbar. As the DNO are now willing to co-operate it is possible, using the Tapping capability of the 33kV/11kV transformer, the voltage at the 11kV side can be reduced from 1.05 pu to 0.98 pu this will allow for a larger voltage change down Feeder 1. Although this upgrade to feeder 1 has improved the maximum power capacity of the wind farm, the thermal line rating is still the barrier to any further increase. The maximum real power output of the wind farm is now 13.69 MW[9] which is, unsurprisingly, roughly double the previous option (7.05 MW).

Figure 4 - DNO co-operation 2nd 'rabbit' line.

The voltage levels across the network continue to stay within the regulated boundaries[9] and with the DNO co-operation on tap changers there is considerable room for expansion of the wind farm size, from a voltage point of view. Fault level Rise9

Load Flows in Appendix B DNO Co-operation second rabbit line.

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The next regulation that will prove to be an issue will be the fault levels in the network. When a fault occurs it seems to the network line an infinite load has come onto the system, and so the network tries to supply this load with all the power it can throw at it, which results in a rush of current towards the fault. The switchgear that has been installed on the network is designed, in the event of a fault, to isolate the grid from the fault by breaking contact and extinguishing the resultant arc. This all needs to be done in 100-150ms, before the generators on the system lose stability. The larger the fault level the larger the fault current will be, the larger the fault current the harder it is to break contact and extinguish the arc. Therefore the cost of switchgear technologies rises exponentially with the fault level. All this goes to say that the network operators only install switchgear with the necessary rating and increasing the fault level in the network will need an upgrade to this switchgear. In the network model the fault level was tested for the most onerous short circuit fault, Line to Line to Line to Ground. For the previous options the fault levels have remained within the regulated limits[10], but for the option of adding a second line to Feeder 1 the fault levels are very close to 250MVA[11]. This is due to having two power lines in parallel, each line represents an impedance and the total impedance is smaller than either of the single line impedances. The impedance for a single line is 0.56ohms, the total impedance is shown in Error: Reference source not found. This reduced impedance makes the feeder 1 seem shorter in electrical distance. Hence when a fault occurs the generators connected to the grid have less impedance between them and the fault and so can dump more power into the fault. 1 Z Total = 1 1 + Z1 Z 2 1 1 1 + 0.56 0.56 = 0.28ohms

Z Total =

Figure 5 - Double Line Impedance

2. Replace Feeder 1 To further upgrade the line on Feeder 1 it would make sense, in light of the double line reduced impedance, to replace the existing line with a new one. This new line would have a much higher power rating to cope with the extra power. To model this the rating on the line in feeder 1 was removed, effectively making it unlimited. Then the power output of the Wind farm was increased until either the Fault level or Voltage regulation limits were met. The tap changer on the 33kV/11kV transformer was set, with DNO co-operation, to fix the voltage at the 11kV Busbar at 0.98 pu. This is the right level to keep the loads at the ends of Feeders 2&3 above 0.94 pu. The Wind farm was increased to a size of 35MW, at this level the voltage at the village Busbar was 1.102 pu[12]. This is just over10 11 12

Appendix C Fault Level Analysis Basic Fit and Forget & Reactive Power compensation Appendix C Fault Level Analysis DNO Co-operation, second line See Appendix B DNO Co-operation, Replace Feeder 1

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the maximum limit of the voltage ranges. So from a voltage point of view 35MW is a maximum. From a fault level point of view there is still more room for a greater wind capacity[13]. There are three issues with this level of output from the Wind farm: 1. Rating of the transformer, 2. Rating of the 33kV line, 3. Losses in the 11 kV line.

1. The transformer is rated at 50MVA in the forward direction, i.e. towards the loads. When the network was being installed there was negligible Distributed Generation, the power system was a one way system, generation on the large scale, high voltage level was filtered down to consumption on the low scale, low voltage level. The transformer was not designed to be operating in reverse bias. And hence is only rated at 60% of maximum power ie 33MVA. So a worst case scenario from the transformers point of view would be when there was maximum generation and minimum consumption from the loads. In the example above with the 35 MW of wind generation and all loads on minimum the transformer is transmitting 30 MW of real & 2.8 MVar of reactive power to the grid. This is getting dangerously close to the limit. 2. The 33kV line is rated at 25MVA this will need to be upgraded which is expensive, the DNO may fund part of this upgrade as the network is aged. 3. The I2R loss in the line from the 11kV Busbar to the Feeder 1 Busbar are 1.15 MW as well as a 0.8 MVar reactive power loss. This is rather large, 1.15 MW is enough to supply a 1000 homes with electricity. Considering the line is only 0.89 km the heat loss from the line would probably cook your breakfast 10m away. There are various solutions we could look at: Upgrading the transformer and the line to a lower resistance line. Installing tapping transformers near the loads and tapping the voltages back to 1.00 pu at the loads, effectively removing any possibility of voltage rise or fall problems. Installing a separate dedicated 33kV line from the 33kV Busbar directly to the wind turbine, this is the option we will look at next.

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See Appendix C Fault level Replace Feeder 1

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By bypassing the local network and connecting to the 33kV substation all the problems associated with voltage unbalance, fault levels and thermal ratings of wires in the network is removed. The method of connection is shown in Error: Reference source not found. The original network system would be left as it was in the first network model. The loads were set back to maximum, the 33kV/11kV transformer changed back to tapping the voltage at the 11kV Busbar to be 1.05 pu.

Figure 6 - Connect to 33kV Substation

Connecting to the 33kV system has many advantages, there are also higher costs involved but these may be balanced out by greater returns. The advantages of this option are that the I2R losses are significantly reduced due to the higher voltage used for transmission, and that the maximum power capacity of the wind farm is increased. The capacity of the wind farm was increased to the factory owners defined maximum, 49 MW. At this level the only problems from a load point of view are on the line from the 33kV Busbar to the Grid. With all the network loads set to a minimum and the wind farm exporting its maximum capacity, this line would need to transmit 44 MW and 1 MVar[14]. For this a ACSR Zebra, 50 MVA Conductor would need to be installed. The Fault levels in the existing network are all under the maximum levels[15], except for those around the wind farm would be the factory owners responsibility anyway.

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Appendix B Load Flows, dedicated 33kV line. Appendix C Fault Levels, dedicated 33kV line.

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VIII. Option D: Active network management.The normal method of supplying power is to match the supply to the demand at any one time. Active network management, also called demand side management, is a method of controlling the loads to match the available energy. Considering limited fossil fuel resources it is sensible to consider this option as 100% flexibility in loads would make 100% generation from renewables a much more feasible idea. From a network management point of view, when considering installing DG to weak areas of the grid, the ability to delay certain loads to a time when there is lower demand for electricity and higher supply of Wind power would enable you to install a larger capacity of DG to the grid without going over the network limitations. To analyse the potential for active network management we will use Option B Fit and Forget with reactive power compensation, which is detailed above. The controllable loads are the factory loads 50% in the day and 30% at night. This has been taken to mean 50% of the maximum load (Day) and 30% of the minimum load (Night). So if 50% of the maximum load could be delayed to counter the worst case scenario, i.e. delayed until a time when minimum load coincided with Maximum generation, this would bring the minimum load of the factory up from 0.5 MVA to 1.5 MVA (1.2 MW & 0.9 MVar). If we put these new minimum loads into our model as the worst case scenario, and compensate for the reactive power demand of the factory (0.9 MVar) with our TCSC, then the power flow down Feeder 1 is 5.72 MW & -0.12 MVar[16]. This leaves room for a larger capacity of wind farm without overloading the 6.6 MVA rating of the line in Feeder 1. The wind farm capacity was increased to 7.91 MW[16] which is almost 8 MW. So by managing the loads of the factory you could potentially increase the capacity of the wind farm by 1 MW.

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Appendix B - Load Flows, Active Network Management (i) & (ii)

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IX. Assessment of optionsOption A: Fit and Forget Technically This is the simplest option from a technical point of view, there is no need to upgrade any assets in the network and the wind farm is sized to not cause problems under all loading scenarios. For thermal rating the line in Feeder 1 is loaded to 97% of its 6.6 MVA line rating. So no upgrade was necessary. For Fault level there were no issues and so no switchgear to upgrade. Economically To economically asses each option we will need to compare the capital investment cost, the annual running costs and the annual income of the installed wind turbine plant. A few assumptions on costs have been made and are displayed in Table 3 below.Item Generation capacity Real power generated Capacity Factor Estimated annual generation Factory owners demands met by wind Sold to grid ROCs Energy not bought from Grid (saved) Energy Sold to Grid Wind Turbine Maintenance Network operator GDUoS charges Quant ity 6.8 5.8 40%[17] 20323. 2 2000 18323. 2 37[18] 100[19]

Unit MVA MW

MWh annually MWh annually MWh annually /MWh /MWh /MWh /kWh /kVA/month

40[ ] 0.01 0.5[21]

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Table 3 - Cost assumptions

This is the cheapest option as there is the least amount of work to do. The budget of installation costs are detailed in Table 4 below. This represents an initial investment of 1.2 Million per MW.Item Costs

17 18 19 20 21

Average wind availability in UK, not including maintenance downtime. Ofgem, Renewables Obligation Buy-out Price, press release, 2010 Based on 9.8p per kWh paid to Scottish Power, 2010 Based on Producer getting 40% of price paid by consumer, P. Taylor 2010 Gridconnection, Automated Connection Assessment, 2010

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Alex Maclean

Distributed generation studyWind Turbines (5*1MW+1*600kW) New circuit New Switchgear New Substation (electrics) (civil) Transformer Connection to substation fee Subtotal Engineering Costs (@ 10%) Total 5,700,00 0 0 0 100,000 120,000 100,000 100,000 6,120,0 00 612,000. 0 6,732,0 00.0

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Table 4 Fit & Forget Installation Costs

The annual running costs and revenues are detailed in Table 5, enable us to calculate the payback period which is 5 years displayed in Error: Reference source not found. The wind turbine lifespan is assumed to be 25 years. Lifetime profit of this option is 33.6 Million.Income ROC Saved on Bills Revenue from Grid Total Revenue per Annum Wind Turbine Maintenance Network operator GDUoS charges Total Profit per Annum Profit per MW Annual 751,958 200,000 732,928 1,684,8 86 -30,000 -40,800 1,614,0 86 278,291

Table 5 - Fit & Forget, Annual Revenue/Costs

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40,000 35,000 30,000 25,000 20,000 15,000 10,000 5,000 0 -5,000 -10,000 0 5 10 Year 15 20 25

,000

Figure 7 - Cashflow, Fit & Forget

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From a regulatory point of view this option is the easiest. Once fitted aside from maintenance there needs to be no involvement from the DNO. All Other Options: All the other options have been assessed in a similar manner, from a technical point of view the option to replace the Feeder 1 line was the most complicated involving the most upgrades to the system. Supplying the Reactive power demand of the Wind turbines using a TCSC device proved beneficial from a technical point of view, but was also proved more economical in the long term returns. From a technical point of view it enable the transfer of, and therefore sale of, a higher quantity of Real power. Despite the considerable financial investment over the lifetime of the wind turbines the TCSC improved the lifetime profit from 33 million to 42 million. The financial assessment is detailed in Appendix F Financial analysis, Error: Reference source not found[22] shows a comparison of the number of years it takes for each option to pay back the initial investment, it also displays the initial investment and lifetime profit of each scheme. Displayed in Table 7[22] is a breakdown on the costs, initial and ongoing, and income of each scheme. Table 7 also displays the profit per MW of each scheme. A summary of the options is displayed in Table 6, from this table the Option A: Fit & Forget has the best return on investment over the 25 year life of the wind turbines. This represents the equivalent of putting the money into an account with an interest rate of 20% per year. Considering that this option is also the simplest option with the lowest associated risk factor it is an attractive option. The next best in terms of the percentage return on initial investment is Option B: Fit & Forget reactive power compensation, although the lifetime returns arent better in terms of percentage of investment they do return nearly 10 million more.Fit & Forget Total Initial Investment Total Profit per Annum No. Years Payback Total Lifetime Profit Return on investment 6,732,0 00 1,614,0 86 5 33,620, 160 499% Fit & Forget + TCSC 8,588,09 6 2,032,14 6 5 42,215,5 64 492% DNO Add 2nd line 16,667,4 88 3,836,37 0 5 79,241,7 52 475% DNO Replace Line 42,274,5 31 9,583,28 0 5 197,307, 469 467% Dedicate d 33kv line 62,648,0 62 13,360,5 92 7 176,933, 938 282% Active Network 10,706,608 2,294,083 5 46,645,472 436%

Table 6 - Summary of Economic Analysis

The Active Network Management, Option D, allowed a greater capacity of wind farm to be installed and hence increased the revenue per year from the wind farm, the22

See Appendix F

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increased Lifetime profit however doesnt justify the extra investment as a similar return could be found in a no risk high interest savings account.

X. RecommendationThe recommendation to the customer in light of this would be to go ahead with Option B: Fit & Forget with Reactive power compensation. However if the customer is prepared to take higher risks and invest more then option C of adding a second line brings almost double the lifetime returns, consequently it is also nearly double the initial investment. The decision to go with option B is a compromise between choosing the lowest risk option and choosing the option with the greatest Gross return over the 25 years. Option B has a relatively small initial investment and hence lower risk, but it is also very lucrative in its returns.

XI. Web Based Grid Connection Tool

Grid connection reportThe report didnt impress me very much. The 50 pages seemed to have a lot about extra research you should do, with a few fill in the blanks so that the report is tailored to each person who gets it. I think the data provided could have been summarised neatly in a few tables with a 5 page explanation of what the issues with each connection methods were. It would be helpful if the report took into account the type of generation being connected and the resultant controllability of each type. i.e. for my report, with hydro power, an option could have been to only supply power when the network isnt overloaded.

Grid connection toolThe online tool had a very good detailed map of the local area in my study. It generated the report very rapidly and had simple instructions which helped you navigate your way around the site and maps. The Map area of the screen could be larger this would make it easier to use. There should be more checks between the drawing on maps stage to the generating a report stage, its seems silly that with a single wrong click you could waste 800.

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VV = I11 kV Z base base base * base = Z base = Vbase /I base

S base = 100 MVA I base = S base/Vbase = 9.1kA

=11,000/909 1 = 100,000,00 0/11,000 =1.21 ohms

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XII. Appendix A Calculation of distribution line lengthsFeeder 1 Distribution line rating: 50mm2 rabbits Summer thermal rating : 6.6 MVA Resistance : 0.5426 ohm/kmResista nce feeder 1 feeder 2 Feeder 3Z = (R2 +X 2 Z feeder Z feeder Z feeder1 1 1

Reactan ce 0.24 pu 0.36 pu 0.3 pu

0.4 pu 0.6 pu 0.5 pu

Equivalent Triangles Z pu X pu

= (0.4 2 +0.24 2 =0.46 pu 6 =0.46 pu * Z base 6 =0.46 *1.21 6 =0.56 ohm 4 s

R puR pu R = Z pu Z R pu R feeder 1 = *Z Z pu 0 .4 R feeder 1 = * 0.564 0.466 = 0.484 ohm s

Z X

R

From equivalent triangles: R feeder1 Rohms / km = 0.484 ohms 0.5426 ohms / km

Similarly: Feeder 1 Feeder 2 Feeder 3 21

Line Length 0.89 km 1.34 km 1.12 km

= 0.89 km

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XIII. Appendix B Load Flows 1. Basic Fit and Forget

2. Fit & Forget, Reactive power compensation

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3. DNO co-operation second rabbit line.

4. DNO co-operation, Replace Feeder 1.

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5. DNO Co-operation, Dedicated 33 kV line

Active Network Management (i)

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Active Network Management (ii)

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XIV. Appendix C Fault Levels 1. Basis Fit & Forget & Reactive Power Compensation

Basic Fit & Forget Fault level analysis

Fit & Forget TCSC

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2. DNO Co-operation, second line

3. DNO Co-operation, Upgraded line.

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4. Dedicated 33kV line

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XV. Appendix D Losses DNO Co-operation, second line

DNO Co-operation, New line higher rating.

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XVI. Appendix E Other

Figure 8 - Optimal choice of FACTS Devices, IEEE, 2009

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XVII. Appendix F Financial Assessment

F&F F&F+TCSC DNO 2 line Replace Line Dedicated 33kv Active Network

15 250,000 200,000 150,000 100,000 50,000 0 -50,000

20

25

Figure 9 - Comparison of Payback period (all option s)32

-100,000

0

5

10

Year ,000

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Table 7 - Income & Costs ComparisonItem Wind Turbines (5*1MW+1*600kW) New circuit New Switchgear or DSM Unit TCSC New Substation (electrics) (civil) Transformer Connecting to substation fee Subtotal Engineering Costs (@ 10%) Total Income ROC Saved on Bills Revenue from Grid Total Revenue per Annum Wind Turbine Maintenance Network operator GDUoS charges Total Profit per Annum Fit & Forget Costs F&F with TCSC Costs DNO Add 2nd line Costs DNO - Replace Line Costs Dedicated 33kv Costs Active Network Costs

5,700,000 7,000,000 13,700,000 35,000,000 49,000,000 7,900,000 0 0 50,000 400,000 2,000,000 0 0 0 0 0 0 1,000,000 0 367,360 732,262 1,451,392 2,902,783 413,280 100,000 100,000 150,000 200,000 400,000 100,000 120,000 120,000 130,000 180,000 350,000 120,000 100,000 100,000 140,000 700,000 1,500,000 100,000 100,000 120,000 250,000 500,000 800,000 100,000 6,120,00 0 7,807,360 15,152,262 38,431,392 56,952,783 9,733,280 612,000 780,736 1,515,226 3,843,139 5,695,278 973,328 6,732,00 10,706,60 0 8,588,096 16,667,487 42,274,530 62,648,061 8 Annual Annual Annual Annual Annual Annual 751,958 914,018 1,776,178 4,537,680 6,352,752 1,024,219 200,000 200,000 200,000 200,000 200,000 400,000 732,928 908,128 1,840,192 4,825,600 6,787,840 947,264 1,684,88 6 2,022,146 3,816,370 9,563,280 13,340,592 2,371,483 -30,000 -40,000 -80,000 -80,000 -80,000 -30,000 -40,800 1,614,08 50,000 2,032,146 100,000 3,836,370 100,000 9,583,280 100,000 13,360,592 -47,400 2,294,083

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Profit per MW

6 278,291

288,248

280,027

273,808

272,665

290,390

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Network Integration of Distributed generation IPSA report

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