Minimum Distribution Charges - WPUIwpui.wisc.edu/wp-uploads/2017/06/Vogt-Min-Dist.pdf · Minimum...
Transcript of Minimum Distribution Charges - WPUIwpui.wisc.edu/wp-uploads/2017/06/Vogt-Min-Dist.pdf · Minimum...
Minimum Distribution Charges
Larry VogtDirector, Rates
Mississippi Power
1
Wisconsin Public Utility Institute
June 28, 2017
Costs of Service vs. Cost RecoveryResidential Service Example
2
Assuming that all defined customer-related costs are recovered throughthe Customer Charge.
Principal Cost-of-Service Study Cost Components
3
The classification step of the cost-of-service study assigns all of the functionalized cost elements to the fundamental cost-causation components of Energy, Demand, and Customer.
Energy-related costs – variable costs which are dependent on kWh energy requirements.
Demand-related costs – fixed costs which are dependent on kW load requirements.
Customer-related costs – fixed costs which are independent of load or energy requirements.
• Energy Costs: VARIABLE
• Demand Costs: FIXED
• Customer Costs: FIXED
Minimum Distribution System (MDS)
Fuel
Classification of Functional Costs
4
Distribution SystemLines and Facilities Costs
55
FERC Description360 Land and Land Rights361 Structures362 Station Equipment363 Storage Battery Equipment364 Poles, Towers & Fixtures365 OH Conductors & Devices
Switches Reclosers & Sectionalizers
366 UG Conduit367 UG Conductors & Devices368 Line Transformers
Regulators Capacitors Cutouts Arresters
369 Services370 Meters373 Street Lighting
SUB
SR
N.O.
N.C.
N.C.N.C.
1,500 cKVAR
333-333-33350-50-50
75
15
25 37.5
336.4 MCM ACSR
4/0
CU
NO. 2 ALC/N
1/0 CU
M
Distribution System O&M Costs
6
FERC Description
Distribution Expenses (Excluding Substations)580 - 589 Operation590 - 598 Maintenance
901 - 905 Customer Account Expenses - Operation
906 - 910 Customer Assistance Expenses – Operation
911 - 917 Sales Expenses – Operation
Administrative and General (A&G) Expenses (Allocated portion)920 - 933 Operation935 Maintenance
Cumulative 1-Phase ResidentialCustomer Cost Components
7
MDS Customer CostsRevenue Requirementper Customer per Month
Minimal Customer Costs
Minimum Distribution System
What is MDS?MDS is an analysis module of the cost-of-service study in which primary and secondary voltage distribution system investment and O&M costs are classified between demand-related and customer-related cost components.
Why is MDS important?MDS quantifies those fixed costs that are independent of load or energy usage and thus provides a cost-justification basis for inclusion in the Customer Charge portion of the rate structure.
8
The Access Function Of The Distribution System
99
All primary and secondary voltage customers are connected to a distribution voltage source, i.e., a local substation.
There is a physical path which brings voltage to the customer’s premise.
Maintaining the voltage path ensures customer access to electrical power.
SUB
The Capacity Function Of The Distribution System
1010
Primary and secondary distribution system facilities and lines must be sized to adequately handle the customers’ demand for power.
Electric service facilities are rated in terms of kVA capacity (conductors rated in terms of ampacity).
Customer Load
Feeder Load
10
Objective of the Minimum Distribution System Analysis
11
To assess each device utilized in the distribution system in terms of its “mission” in order to determine if its function is:
Dependent on kW load requirements and therefore demand related,
or
Independent of kW load requirements and therefore customer related.
Customer or Demand?
12
MW
TIME
Capacitor-Based Voltage Control
SUBFEEDER
120 V
108 V
132 V+10%
‐10%
DISTANCE
13
Customer or Demand?
14
Protection SchemeTemporary Fault Condition
RCBSUB
15
Protection SchemePermanent Fault Condition
RCBSUB
16
Protection SchemePermanent Fault Condition – No Load
RCBSUB
17
Customer or Demand?
18
Classification of Distribution Plant for the Cost-of-Service
1919
Demand Customer
Distribution Substations X
Primary Lines* X X
Line Transformers* X X
Secondary Lines* X X
Other Line Equipment* X X
Service Lines X
Meters X
* Minimum Distribution System facilities.
20
Zero-Intercept Methodology
THE Y-AXISINTERCEPT
IS THE UNITCOST OF ZERO CAPACITY
CAPACITY
UNITCOSTS
××
××
× COST OF A STANDARDSIZE UNIT
Applied to: Line Transformers Conductors Poles
Line Transformers
21
Zero-Intercept Example
22
Single-Phase Overhead Transformers1. ZERO-INTERCEPT: $463.975/transformer
Based on various kVA sizes of 7.2 kV - 120/240 V, single bushing, pole-mount transformers
2. TOTAL NUMBER OF OVERHEAD TRANSFORMERS: 98,278CUSTOMER COMPONENT = $ 463.975 × 98,728 = $45,807,307
3. TOTAL OVERHEAD TRANSFORMER COST: $109,960,813DEMAND COMPONENT = $109,960,813 - $45,807,307 = $64,153,506
CUSTOMER COMPONENT = 41.7%
DEMAND COMPONENT = 58.3%
Primary and Secondary Conductors and Poles
23
PRIMARY
NEUTRAL
SECONDARY
UNDERGROUNDPRIMARY CABLE
CONDUCTOR
CONCENTRICNEUTRAL
24
CONDUIT FORUNDERGROUND CABLES
RIGID PVC FLEXIBLE
25
26
Distribution PolesTypes Of Materials
0%
10%
20%
30%
40%
50%
60%
70%
80%
90%
100%
ALUMINUM CONCRETE FIBERGLASS STEEL WOOD
0.0%
0.1%
0.2%
0.3%
0.4%
0.5%
0.6%
0.7%
0.8%
0.9%
1.0%
ALUMINUM CONCRETE FIBERGLASS STEEL
27
Pole HeightsRelative Frequency Distribution
0%
5%
10%
15%
20%
25%
30%
35%
40%
30' 35' 40' 45' 50' 55' 60' 65' 70' 75' 80' 85' 90' 95'POLE HEIGHTS
Clearance Requirements
2828
Poles lines must be designed to ensure proper safety clearances, such as specified in the National Electric Safety Code (NESC), Section 23.
The NESC provides specific minimum clearances of power lines located over: Roadways, parking lots, driveways, pedestrian areas, railroad
track rails, water ways, etc.
Other electric conductors and services, trolley/electric train cables, communications cables, etc.
29
Pole Line Grading
IMPROPER GRADING:POLES ALL HAVE THE SAME HEIGHT
PROPER GRADING:POLES WITH VARYING HEIGHTS
Distribution Pole ClassificationConclusion On Pole Height
3030
Pole height requirements are mainly a function of clearances and line grading, which are related to safety and mechanical design.
In some situations, a pole height may need to be increased (e.g., from a 40’ to a 45’) to accommodate some facilities.
Overall, pole height is not a predominant function of load.
31
Pole Class
32
Standard Pole ClassesExample: 35’ Wood Pole
No. 139.0”
No. 236.5”
No. 334.0’
No. 431.5”
No. 529.0”
No. 627.0”
No. 725.0”
MINIMUM CIRCUMFERENCE OF SOUTHERN YELLOW PINE POLES (@ GROUND LINE)
33
Pole Class RequirementsBased On Transformer Capacity
0
1
2
3
4
5
6
7
10 15 25 37.5 50 75 100 167 250TRANSFORMER kVA
POLE
CLA
SS
1 TRANSFORMER 2 TRANSFORMERS 3 TRANSFORMERS
Distribution Pole ClassificationConclusion On Pole Class
3434
The physical sizes and weights of line transformers and conductors are related to their current carrying capabilities.
Pole class must be increased in order to carry heavy mechanical loads caused by large line transformers and conductors.
Overall, pole class is a predominant function of load.
Example MDS Analysis ResultsPoles, Transformers, and Conductors
35
Customer DemandPoles• Wood 66.4% 33.6%• Concrete 47.3% 52.7%• Steel 57.5% 42.5%
Transformers• 1Φ OH* 41.7% 58.3%• 1Φ UG** 61.5% 38.5%• 3Φ UG** 34.2% 65.8%
* Basis for classifying transformer vaults** Basis for classifying transformer pads
Customer DemandConductorsPrimary• Bare ACSR OH 21.0% 79.0%• 15 kV CN UG* 57.4% 42.6%
Secondary• WP AL OH 38.4% 61.6%• Duplex OH 31.4% 68.6%• 1-Conductor UG* 60.7% 39.3%
* Basis for classifying conduit
Example MDS Analysis ResultsDistribution Line Devices
36
Primary SecondaryCustomer Demand Customer Demand
Regulators & Capacitors 100%
Reclosers and Sectionalizers 100%
Cutouts & Arresters• Line Transformers (OH) 41.7% 58.3%• Regulators & Capacitors 100%• Reclosers & Sectionalizers 100%• Line Protection 100%
Bypass Switches• Regulators 100%• Reclosers & Sectionalizers 100%
OH Line Switches* 21.0% 79.0%UG Line Switches* 57.4% 42.6%* Based on conductors
Example Cost-of-Service ResultsFor Three Low Voltage Customer Classes
37
Larry Vogt
Q&A
38
Appendix Materials
39
Weighted Linear RegressionFor Distribution Line Transformers
4040
N = Total number of all transformers of a given type, e.g., 59,800 7.2 kV -120/240 V, single-bushing, pole-mount units
n = Number of a given size transformer, e.g., 9,935 15 kVA
X = Transformer size in kVA, e.g., 5, 7.5, 10, 15, etc.
Y = Transformer unit cost in $ per unit, e.g., $724.48 (cost of a 15 kVA unit)
22
nXnXN
nYnXnXYNm
NnX
NYn
mb
SLOPE
y‐INTERCEPT
41
Zero-Intercept AnalysisThe Problem With Vintage Costs
$0
$200
$400
$600
$800
$1,000
$1,200
$1,400
$1,600
$1,800
$2,000
0 10 20 30 40 50 60 70 80 90 100
Analysis of Pad-Mount Line TransformersBased on Booked Installed Costs
kVA
Unit C
ost
1Φ
3Φ
42
Zero-Intercept AnalysisUtilizing Current Costs
3Φ
1Φ
Analysis of Pad-Mount Line TransformersBased on Rebuild Costs
kVA
Unit C
ost
$0
$1,500
$3,000
$4,500
$6,000
$7,500
$9,000
$10,500
$12,000
$13,500
$15,000
0 10 20 30 40 50 60 70 80 90 100
Zero-Intercept Example
43
Primary Overhead Conductor1. ZERO-INTERCEPT: $0.396/ft
Based on various MCM sizes of bare ACSR conductors
2. TOTAL LENGTH OF PRIMARY CONDUCTORS: 15,708,000 ftPRIMARY CIRCUIT LENGTH: 15,708,000 × 2 = 31,416,000 ftCUSTOMER COMPONENT = $0.396 × 29,898,000* = $11,827,081* Minimum Distribution System Length
3. TOTAL PRIMARY CONDUCTOR COST: $56,416,253DEMAND COMPONENT = $56,416,253 - $11,827,081 = $44,589,172
CUSTOMER COMPONENT = 21.0%
DEMAND COMPONENT = 79.0%
43
Determination Of OverheadCircuit Lengths For The MDS
4444
SUB
PRIMARY
SECONDARYUNDERBUILD
PRIMARY NEUTRAL COMMON NEUTRAL SECONDARY NEUTRAL
SECONDARYTAPS
TOTAL POLE MILES
Weighted Linear RegressionFor Distribution Conductors
4545
N = Total feet of all conductors of a given type, e.g., 47,557,568 ft of ACSR conductors
n = Number of feet of a given size conductor, e.g., 26,194,939 ft of #2 ACSR
X = Conductor size in MCM (a #2 wire is 66.36 MCM), e.g., 26.24, 41.74, 52.62, 66.36, etc.
Y = Conductor unit cost in $ per feet, e.g., $0.659/ft (cost of a #2 ACSR conductor)
22
nXnXN
nYnXnXYNm
NnX
NYn
mb
SLOPE
y‐INTERCEPT
Pole Capacity
4646
Poles have no electrical capacity component, but they do have a mechanical capacity (strength) component that can be viewed as a proxy for electrical loading.
Pole class (or circumference) can represent loading capability for wood poles, but it does not work for steel or concrete poles since different classes can have the same physical dimensions.
Ground line moment capacities do differ by class for all poles.
Transverse WindLoad of 1,200 lb
Example: 35’ 5-C Pole
GLMC = 33,000 ft-lbs = 33 kips
Weighted Linear RegressionFor Distribution Poles
4747
N = Total feet of all poles of a given type, e.g., 55,642 ft of 40 ft wood poles
n = Number of feet of a given size pole based on its GLMC, e.g., 21,137 ft of 76.80 kilopounds (kips) poles
X = Ground Line Moment Capacity in kips, e.g., 48.0, 60.8, 76.8, 96.0, etc.
Y = Pole unit cost in $ per feet, e.g., $12.05/ft (cost of a 76.8 kips pole)
22
nXnXN
nYnXnXYNm
NnX
NYn
mb
SLOPE
y‐INTERCEPT
Zero-Intercept Example
48
Wood Poles1. ZERO-INTERCEPT: $7.883/ft
Based on various kip ratings of 40’ southern pine poles
2. TOTAL LINEAR FEET OF WOOD POLES: 5,579,390 ftCUSTOMER COMPONENT = $7.883 × 5,579,390 = $43,982,773
3. TOTAL WOOD POLE COST: $66,254,744DEMAND COMPONENT = $66,254,744 - $43,982,773 = $22,271,971
CUSTOMER COMPONENT = 66.4%
DEMAND COMPONENT = 33.6%
48
49
Differentiated Cost AllocationBased on Voltage Magnitude & Phase
3-Phase vs. 1-Phase CustomersCost-of-Service Weighted Allocators
50
CUSTOMER VOLTAGE CLASS 1Φ LV 3Φ LV 1Φ HV 3Φ HV
1Φ OH Line Transformers L1 L3 × 3
Services:1Φ Lines L13Φ Lines L3
Meters:Watt-hour (non-demand) LN11Φ Demand LD1 H13Φ Demand L3 H3LV CT LD1 L3 × 3LV VT LD1 L3 × 3HV CT H1 H3 × 3HV VT H1 H3 × 3
L1 = # of 1Φ LV customers (LN1 + LD1); L3 = # of 3Φ LV customers H1 = # of 1Φ HV customers; H3 = # of 3Φ HV customers