1. Distribution Loss Factors for Cost To Serve study
Lolo Buys
Eskom
Electricity Pricing

2. Contents Outcome Topic 1: Cost of supply study
Topic 2: Energy losses overview
Topic 3: Modelling Energy losses in HV and MV systems:
HV Losses simulation
MV Losses simulation
End note
Each learner must say what is it that they understand about the topic and what are their expectations.

3. Outcomes of the Training
After this session the learner will be able to:
Understand cost of supply studies
Define technical losses and loss factors.
Understand the factors that affect technical losses
Understand how the technical losses fit into the cost of supply.
Understand how technical losses can be modelled
Understand the use of tools to model technical losses

4. Topic 1:Cost of Supply Study
Objective: To provide an overview of cost of supply study

5. Cost of supply study
A cost of supply study is a study in which the total company cost of service (revenue requirement) is spread or allocated to customer classes.
Customer Class or Class of Service – A set of customers with similar characteristics who have been grouped for the purpose of setting an applicable rate for electric service
Common classifications include residential, commercial, primary service and industrial

6. Cost of Supply
tariff book

7. Cost of Supply Study Steps
Functionalization: costs broken down into production, transmission, distribution
Classification: costs classified by customer, energy, demand
Allocation: costs allocated to different customer classes – residential, commercial, industrial

8. Functionalization and Classification
Distribution
Poles, towers, fixtures
Line transformers
Meters
Station Equipment
Production
Production Plant
Fuel costs
Purchased Power
Transmission
Backbone & Inter-tie Facilities
Generation Step-up Facilities
Subtransmission Plant
Line transformers
Poles, towers, fixtures
Demand & Customer
Station Equipment
Demand
Meters
Customer
Purchased Power
Production Plant
Demand & Energy
Fuel costs
Energy
Demand & Energy
Transmission costs are charged to utilities, some of which are based on demand, some on energy. 

9. Cost Allocation Residential Industrial Commercial
Classified Distribution Costs
Classified Production Costs
Charged Transmission Costs
Allocate
Residential
Industrial
Commercial

10. Topic Summary
Cost of supply study
Customer classification
Various steps of Cost of supply study

11. Topic 2: Energy losses overview
Objective:
To provide an overview of energy losses in distribution networks
The role of energy losses in cost of supply studies

12. Definition of Energy Losses
Energy losses associated with a distribution system can be classified as follows :
Technical Losses - losses associated with the electrical system
Series losses which are proportional to the square of the current and to the resistance of the circuit elements and
Shunt losses due the excitation losses in transformers and rotating machines, as well as leakage currents in cables
Non-technical losses - losses associated with unidentified and uncollected revenue. This covers matters such as illegal connections, meter tampering, metering errors, errors in estimating unmetered supplies, errors in invoicing and revenue collection.

13. Technical losses
Energy losses are incurred as results of transfer of power over the network from the sources to loads.
The level of losses are primarily influenced by demand, conductor’s types, the extent of transformation and distance of loads to source amongst other things.

14. Energy losses on lines
Energy losses are a function of the conductor material, the distance, temperature, and loading
Output Energy is less than input Energy.

15. Energy losses on Transformer
No load losses are considered fixed losses
Load losses vary with the load
Other losses are negligibly small

16. Calculation of Loss factors
The loss factors are essentially a function of energy losses as seen in equation 1 and 2.
Ploss = energy losses, The losses are proportional to square of the current
being supplied through the network
Psupplied = energy supplied
I is current and R+jX is the line impedance

17. Distribution network model for cost to serveG
400kV/275kV/220kV
132kV
88kV
33kV
11kV
400V
In cost to serve studies, the loss factors are disaggregated as follows:
HV: 33kV < Vn ≤ 132kV
MV: 1kV < Vn ≤ 33kV
LV: Vn ≤ 1kV
Urban and rural for MV and LV
The generic network diagram below is used to represent various load connections at different voltage levels and to aid in the pooling and calculation of the Distribution Loss Factors (DLFs).

18. Topic Summary
Energy losses
Technical losses
The relationship between technical losses and loss factors
The generic network equivalent model

19. Topic 3: Modelling Energy losses in HV and MV systems
Objectives:
To provide an overview of the methodology used in modeling energy losses in distribution networks
The use of various tools in simulation of energy losses
and the interpretation of the results

20. Summary of Loss Factor modelling process
Simulate technical losses
Determine losses per assets group
Calculate loss factor for each assets group
Adjust loss factors in line with the WD/Energy allocation
Power flow analysis on OU networks
Use daily load curves
Forced load curve for solar and wind generators
Lines and transformers are grouped according to assets classes used in the CTS
Losses determines for each of the assets class
Calculate the loss factors from the technical losses
Adjust/scale the loss factor to the energy and demand allocation
2018/10/09

21. Calculation of Loss factors
The loss factors are essentially a function of energy losses as seen in equation 1 and 2.
Ploss = energy losses, The losses are proportional to square of the current
being supplied through the network
Psupplied = energy supplied
I is current and R+jX is the line impedance

22. Modelling of Energy losses
Two different approaches employed but both use engineering model/simulators. Selection of the approaches is largely influenced by the nature of the network as modelled (case files).
A case file for MV networks is made up of a single feeder. A large number of case files is required to draw a representative estimate for losses.
Case files for HV Networks have multiple feeders, thus with one case file a representative estimate of losses is possible.
The medium and low voltage networks proved to be challenging to model hourly.

23. HV Losses simulation

24. HV methodology 𝑓 𝑥 of And 𝑃 𝐿𝑜𝑠𝑠 = 𝐼 2 𝑅 𝑃 𝑖 = 𝑃 𝐿𝑜𝑎𝑑 + 𝑃 𝐿𝑜𝑠𝑠
Generators dispatched to match the load requirement
Load profiles
Losses estimated
Loss factors determined
𝑓 𝑥 of
And 𝑃 𝐿𝑜𝑠𝑠 = 𝐼 2 𝑅
𝑃 𝑖 = 𝑃 𝐿𝑜𝑎𝑑 + 𝑃 𝐿𝑜𝑠𝑠
Hourly losses-output
Excel/Access and R used for data storage and analysis
Network models
Digsilent/ReticMaster case files
Load flow studies
Powerworld simulator used for studies
Coded in python
The method used to calculate average DLFs is to carry out load flow studies to determine the losses for each hour of day, followed by the statistical analysis of the hourly losses.

25. Process: Computation of loss factors for 33kV to 132kV (HV) networks
The methodology used to calculate average DLFs for high voltage network is to carry out load flow studies to determine the losses for each hour of the day for the different network components.
Quasi-dynamic modelling
To perform the simulation, load profiles for selected loads and the PowerFactory simulator and steady state case files were used.
The results (Losses) are used o determine loss factors
The simulation was automated to perform loads flows for every hour. The above process was performed using PowerFactory Digsilent Software and Python scripting language.

26. Analysis of the Results: HV methodology
The results of the HV network for all operating units are depicted for each network.
In order to understand the spread of these losses, a histogram was also plotted
A weighted average (weighted by load) was calculated to provide alternative estimate of losses where it’s not possible to use statistical results
The result, consisting of line losses, transformer losses, line flows and maximum power of the transformer are stored in the excel file for analysis. The analysis was done for six operating units

27. Analysis of the Results: HV methodology
There are significant differences in the losses per assets category. The difference can mainly be attributed to the approaches used in determining the losses factors, as outlined below:
The previous methodology:
relied on the simulation of losses for types of commonly used conductors/assets in Distribution.
The method also assumed various loading of each asset type
There was no simulation of a network as modelled by distribution engineers/planners
The previous methodology
relied on the simulation of network model developed by distribution planning and Load profiles used in Distribution (PowerGLF)
Based largely on the Distribution standards

28. Analysis of the Results: HV methodology

29. MV Losses simulation

30. Computation of loss factors for 6.6kV to 22kV MV networks
The medium and low voltage networks proved to be challenging to model hourly. As a result a different approach employing simulation of peak snap-shots, load loss factors and load factors to determine energy losses and energy consumed over a period is used.
Peak losses and load energy are derived from load flow simulation using ReticMaster case files.
Load factors and load loss factors are calculated from the actual metered data.
The MV energy losses are expressed as:

31. Computation of loss factors for 6.6kV to 22kV MV networks
The process of determining the MV loss factors involves the steps depicted by the flow diagram

32. Testing the MV methodology: Results
Lower voltage networks tend to have higher losses, since most networks use underground cables and also carry higher currents.

33. Testing the MV methodology: Results
The losses for MV networks of different operating units, and densities range from 2.5% of to 7.6 % on rural density and 3.10% to 7.23% on the urban arrangement as seen on the table.
The calculated average is approximately 5.44% for all MV networks used in the model
A weighted average (weighted by peak load of each case file) was calculated to provide an estimate of losses
The box-and-whisker plot is shown
The plot also indicate that there are outliers.

34. Topic Summary
The methodology used in modeling energy losses in distribution networks
The use of various tools in simulation of energy losses
Interpretation of the results

35. Course summary Cost of supply study
Energy losses in distribution networks
The role of energy losses in cost of supply studies
The methodology used in modeling energy losses in distribution networks
The use of various tools in simulation of energy losses
The interpretation of the results

36. THANK YOU