Longer term DUoS Charging Model Nigel Turvey Design & - PowerPoint PPT Presentation

Longer term DUoS Charging Model Nigel Turvey – Design & Development Manager

WPD Project • Started in March 2005 • 1 year duration working with The University of Bath • Objective to develop a charging methodology based usage of network assets • Covered by a contract with the Intellectual Property Rights assigned to WPD

MW+MVAr-Mile charging model (Bath model) ⋅ θ sin Q ⋅ θ cos P Q θ θ P For each distributi on line : = ⋅ + ⋅ S P cos θ Q sin θ L L - N L L - N L θ : Power factor of distributi on line L

Long-run marginal cost pricing based on MW+MVAr-mile ∑ = ∆ LRMP UC MW Km l l l l sin ⋅ Q θ ⋅ P cos θ P Q ∑ ∑ = ∆ + ∆ LRMP UC MW Km UC MVAr Km , , P l l l Q l l l l l = ⋅ θ cos UC UC , P N l l = ⋅ θ sin UC UC , Q N l l

Outline of the process • Cost evaluation: • Cost of a reference network, accommodating anticipated generation/demand • Cost allocation: • Inject 1.0 +j1.0 at each node of the reference network • Determine which facilities support the injection and at what degree • Calculate locational charges according to the degree of the support along each line, the unit cost of the line and the length of the line

Outline of the process (cont) • Calculation of used capacity cost: • locational unit prices for both real and reactive power at all the nodes are used to calculate the total cost of real and reactive power drawn by demand/generation customers at the corresponding nodes. • Calculation of unused capacity cost: • Calculated as the difference between required asset cost and the cost of used capacity • Allocation of unused capacity cost: • Unused cost has been uniformly distributed among the total MVA connected load/generations sets a uniform unit price(£/kVA/Year)

Example Reference Network 385.79+j297.26 Bus 1 375.87+j246.13 L:4.86+j25.31=26.04 MVA L:4.86+j25.31=26.04MVA Bus 2 D:29.66+j31.03=42.92MVA G:20-j20=28.28MVA

Cost of Reference network If each line is supposed to support 45MVA over 11km, the annuity cost is £236760 per year, then the unit cost of the line: UC l =236760/45/11=£478.3/MVA/km Since the line flow along both lines are: 4.96+j25.6=26MVA cosa=4.96/26=0.1908 sina=25.6/26=0.9846 = ⋅ θ = = cos 478 . 3 * 0 . 1908 £ 91 . 25 / / UC UC MW km , P N l l = ⋅ θ = = sin 478 . 3 * 0 . 9846 £ 470 . 94 / / UC UC MVAr km , Q N l l

Cost allocation 1+j1 Bus 1 0.5+j0.5 0.5+j0.5 Bus 2 1+j1

Calculate locational charge ∑ = ∆ C UC MW Km , p P l l l l = × × + × × = ( 0 . 5 11 91 . 25 0 . 5 11 91 . 25 ) £ 1003 . 7 / Cp MW ∑ = ∆ C UC MVAr Km , q Q l l l l = × × + × × = ( 0 . 5 11 470 . 94 0 . 5 11 470 . 94 ) £ 5180 . 4 / Cq MVAr

Calculation of used and calc and allocation of unused capacity D: 29.66+j31.03= 42.92MVA G:20-j20=28.28MVA At Cp=£1,003.7 /MW, Cq=£5,180.4/MVAr Annuity cost to be recovered: £236,760x2=£473,520 Revenue Revenue from Total revenue MW MVAr from unused capacity recovery recovery capacity utilisation Gene -£20,074 £103,610 £83,536 £10,277 £93,813 Customer (£363.4/MVA) (£3317.3/MVA) Demand £29,770 £171,070 £200,840 £15,597 £216,437 Customer (£363.4/MVA) (£5042.8/MVA) Total £9,696 £274,680 £284,376 £25,874 £310,250

What about lower voltage networks ? • Method is reasonable complex at 132/33kV level where there are around 1,000 nodes • At HV number of nodes increase to in excess of 20,000 – making application impractical • Billing and settlements data increasingly at GSP Group level on HV networks and entirely on LV networks • Output from model at 33/11kV transformation used as input to HV & LV yardsticks • Existing ‘500MW’ model used for HV & LV cost allocation

Results so far • Method has been applied to the whole WPD S Wales network • Data in model is still being checked/ corrected but results are likely to be representative

Revenue from unused Total Marginal Cost Revenue from used capacity Bus Data capacity Revenue Q P Unused (£/KVAr/Yr P(£/Yr) Q(£/Yr) Total (£/Yr) (£/KVA/Yr) Total (£/Yr) (£/Yr) (£/KW/Yr) Bus Number ) 2203 -1.61 0.68 - 33,691 4,671 - 29,020 9.96 219,166 190,146 2204 -1.56 0.57 - 32,541 3,901 - 28,640 9.96 219,166 190,526 2205 1.61 -0.68 81,466 - 6,963 74,503 9.96 514,427 588,931 2236 2.88 4.01 52,038 30,885 82,922 9.96 195,955 278,877 2255 3.92 4.95 98,784 41,068 139,852 9.96 264,315 404,168 3732 2.45 3.45 29,179 25,508 54,687 9.96 139,603 194,290 3762 2.00 3.31 29,925 30,820 60,745 9.96 175,824 236,570 3771 1.97 3.44 14,942 16,168 31,110 9.96 89,021 120,131 3780 0.12 -0.71 1,162 - 1,162 9.96 100,619 101,780 3781 0.78 0.83 7,095 2,476 9,571 9.96 95,636 105,207 3789 0.20 0.37 2,856 - 2,856 9.96 139,471 142,327 3792 3.41 4.18 12,287 9,196 21,483 9.96 42,031 63,514

Results for some EHV Customers 3,000,000 2,500,000 2,000,000 1,500,000 £/yr 1,000,000 500,000 0 EHV1 EHV2 EHV3 EHV4 EHV5 -500,000 2005/06 prices 2005/06 full prices Revised interim Proposed Prices 2005/06 new method - unused across whole network 2005/06 new method - unused across sub network 2005/06 used charge

Main Issues • Method can give high prices where there is low system utilisation • Allocation of unused capacity costs – by sub network or system wide ? • How to deal with system assets that have been part contributed to as part of connection charges – would account for some of the unused capacity • What generator/large customer output/ demand should be used to assess system costs • With the use of different models at 132/33kV and lower voltages, how do we ensure ‘fair’ apportionment of revenue from these two models ? • Yet more price disturbance for EHV connections

Next Steps • Understanding why unused charge is so high and the impact of different apportionment • Model uses time of peak demand – work now looking at off peak charging • How to charge for HV & LV generators

Longer term DUoS Charging Model Nigel Turvey – Design & Development Manager