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 θ θ cos ⋅ P θ sin ⋅ Q P Q

line

• n

distributi

• f

factor Power : θ sinθ Q cosθ P S : line

• n

distributi each For

L L N

• L

L N

• L

L

⋅ + ⋅ =

Long-run marginal cost pricing based on MW+MVAr-mile

∑

∆ =

l l l l

Km MW UC LRMP

∑ ∑

∆ + ∆ =

l l l l l Q l l l P

Km MVAr UC Km MW UC LRMP

, ,

l l N P

UC UC θ cos

,

⋅ =

l l N Q

UC UC θ sin

,

⋅ =

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
• f 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

Bus 2

D:29.66+j31.03=42.92MVA G:20-j20=28.28MVA L:4.86+j25.31=26.04MVA L:4.86+j25.31=26.04 MVA

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: UCl =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

km MW UC UC

l l N P

/ / 25 . 91 £ 1908 . * 3 . 478 cos

,

= = ⋅ = θ

km MVAr UC UC

l l N Q

/ / 94 . 470 £ 9846 . * 3 . 478 sin

,

= = ⋅ = θ

Cost allocation

1+j1

Bus 1

0.5+j0.5 0.5+j0.5

Bus 2

1+j1

Calculate locational charge

∑

∆ =

l l l l P p

Km MW UC C

,

MW Cp / 7 . 1003 £ ) 25 . 91 11 5 . 25 . 91 11 5 . ( = × × + × × =

∑

∆ =

l l l l Q q

Km MVAr UC C

,

MVAr Cq / 4 . 5180 £ ) 94 . 470 11 5 . 94 . 470 11 5 . ( = × × + × × =

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

MW recovery MVAr recovery Revenue from capacity utilisation Revenue from unused capacity Total revenue Gene Customer

• £20,074

£103,610 £83,536 £10,277 (£363.4/MVA) £93,813 (£3317.3/MVA) Demand Customer £29,770 £171,070 £200,840 £15,597 (£363.4/MVA) £216,437 (£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

Bus Data Total Revenue Bus Number P (£/KW/Yr) Q (£/KVAr/Yr ) P(£/Yr) Q(£/Yr) Total (£/Yr) Unused (£/KVA/Yr) Total (£/Yr) (£/Yr) 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 Marginal Cost Revenue from used capacity Revenue from unused capacity

Results for some EHV Customers

• 500,000

500,000 1,000,000 1,500,000 2,000,000 2,500,000 3,000,000 EHV1 EHV2 EHV3 EHV4 EHV5

£/yr

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
• ff peak charging
• How to charge for HV & LV generators

Longer term DUoS Charging Model

Nigel Turvey – Design & Development Manager