Peak Load Contribution (PLC) Overview
As a local distribution company (LDC) member of PJM Interconnection, BGE is responsible for determining the capacity and network transmission peak load contributions (PLCs) for each electric account within the BGE zone, aggregating these PLCs separately by capacity and network transmission to the appropriate LSE, and reporting the total aggregate PLCs by capacity and network transmission for each LSE to PJM.
Capacity Peak Load Contribution
As required by the PJM Reliability Assurance Agreement (RAA), the PJM Office of the Interconnection (PJM OI) calculates the PJM zonal capacity obligation. Each LDC in PJMs control area is assigned a capacity obligation for its zone. The LDC is required to calculate and report to PJM daily the capacity peak load contribution data, aggregated by electricity supplier, for its zone.
In accordance with the PJM RAA and PJM rules and procedures, BGE will calculate a system capacity peak load contribution ticket for each electric account on an annual basis. After the end of a summer period, PJM will identify the five highest weather normalized PJM system coincident load hours that occurred on different days over the period from June 1 through September 30. The LDC-specific zones will identify the actual zonal loads associated with these five hours. (See PLC Peak Hours & Defaults) Each LDC-specific zone will reconcile these five different hours back to the one hour weather normalized, system coincident zonal peak load obligation. The consequent peak load contributions will be calculated as an average over these five hours. Each accounts PLC will be updated on a yearly basis in accordance with PJM rules and procedures.
Network Transmission Service Peak Load Contribution
Each local distribution company within PJM has a network transmission service peak load contribution requirement. To allocate fairly the LDCs daily requirement to electricity suppliers, network transmission service peak load contributions (transmission PLCs) are determined. In accordance with the Open Access Transmission Tariff (OATT) and PJM rules and procedures, BGE will calculate a transmission PLC ticket for each electric account on an annual basis. For a given year, an accounts daily network transmission service PLC requirement is based on its load at the time of the actual unrestricted peak hours that occurred during the twelve months ending October 31 of the prior calendar year. (See PLC Peak Hours & Defaults) At the end of this 12-month period, PJM and BGE will identify the five highest unrestricted load hours that occurred on different days during this 12-month period. The LDC will reconcile these five different hours back to the highest unrestricted peak load hour that PJM has determined to be BGEs zonal peak load obligation. The consequent peak load contributions will be calculated as an average over these five hours. The accounts transmission PLC will be updated in accordance with PJM rules and procedures.
Daily Reporting of Peak Load Contributions
On a daily basis, BGE calculates and reports to PJM the sum of the PLCs for each account served by the electricity supplier, known as the Supplier PLC. BGE computes the electricity supplier PLCs after the close of each business day and submits them to PJM using PJMs eRPM system and published submission guidelines. The following sections describe the methods and calculations used to derive electric accounts and electricity suppliers capacity and network transmission PLCs.
Calculating Annual Peak Load Contributions
Peak load contributions are typically processed differently for the three metering types: (1) interval metered accounts, (2) monthly demand metered accounts, and (3) monthly metered accounts (without demand metering). Accounts with monthly demand meters or monthly non-demand meters are also referred to as non-interval metered customers.
- Interval metered accounts - Accounts that have meter usage data available on the hourly level, including meter data collected in 15-minute intervals during the billing cycle. Data collected in 15 minute intervals will be aggregated into hourly quantities.
- Monthly kW demand metered accounts - Accounts that have meter usage data including the accounts highest demand level (monthly kW peak) for the billing cycle and the on-peak time-of-use (TOU) period. In addition to metered demands, kWh energy usage is metered for each time-of-use period defined in BGEs retail tariff.
- Monthly kWh metered accounts - Accounts that have metered kWh usage for the billing cycle. Accounts that are time-of-use (TOU) accounts have kWh recorded separately for each TOU period defined in BGEs retail tariff.
The derivation of the peak load contributions consists of four steps:
- Determine the unreconciled peak loads.
- Reconcile the peak loads.
- Calculate the profiled segment weight and obligation factor for each profiled segment.
- Derive each accounts annual capacity and transmission peak load contribution.
A description of each procedure follows. The procedures are further illustrated below by a simplified hypothetical distribution system serving eight accounts: three monthly kWh metered accounts, three monthly kW demand metered accounts, and two interval metered accounts. An example for each type of account is given showing calculations for one of the five hours averaged in deriving the capacity and transmission PLCs.
Step 1: Determine Unreconciled Peak Loads
For each profiled segment and interval metered account, an initial peak load estimate is obtained based on data metered at the customers premise. Premise level loads are adjusted for the electrical losses that occur in BGEs transmission and distribution system. Loss factors vary by voltage class and may be found under BGE Loss Factors. The loss-adjusted load estimates are termed unreconciled peak loads since in total they may not exactly equal the system load for that hour, and are therefore reconciled or scaled to the known system load. For each peak hour used to calculate PLCs the unreconciled peak is obtained as follows:
- Interval metered accounts: the load for each interval metered electric account is extracted and measured for any load curtailment impacts due to BGE’s direct load control programs. . Each load is then adjusted for losses.
- Non interval metered accounts: the average peak load for each profiled segment is obtained from BGEs statistical sample of each profiled segment. (See Load Profiles) This aggregate peak load is allocated to each account in the segment by applying an account-specific usage factor. The usage factor represents the ratio of the metered usage for the account to the average usage of the profiled segment over the same period. The total unreconciled peak load for the segment is the product of the peak load for the segment, the loss factor for the segment, and the sum of the usage factors for the segment.
Step 2: Reconcile Peak Loads
Unreconciled peak loads are then scaled to BGEs total zonal load for each of the five hours included in the capacity and the transmission PLC calculation. (See PLC Peak Hours & Defaults) An imbalance is computed as the difference between the total unreconciled load and BGEs total zonal load for each zonal peak hour. This hourly imbalance is then apportioned to each interval metered account and each profiled segment in proportion to its unreconciled load.
Step 3: Calculate the Profiled Segment Weight and Obligation Factor for each Profiled Segment
- Profiled segment weight for monthly metered customers: The sum of the usage factors for each monthly metered profiled segment is the profiled segment weight for that segment.
- Profiled segment weight for demand metered customers: The sum of the billed demands for each demand billed profiled segment is the profiled segment weight for that segment.
- Obligation factor: The reconciled peak load divided by the profiled segment weight for each segment is the obligation factor for that segment.
Step 4: Derive the Peak Load Contributions for each Account
- Non interval metered accounts: The peak load contribution for each account for each hour is the product of the obligation factor for the profiled segment times the usage factor for the account.
- Interval metered accounts: The peak load contribution for each account for each hour is the reconciled peak load for the account.
- Capacity peak load contribution: The capacity peak load contribution for each account is the average of the accounts hourly peak load contributions for the five hours designated by PJM as peak capacity hours. (See PLC Peak Hours & Defaults)
- Network transmission peak load contribution: The transmission peak load contribution for each account is the average of the accounts hourly peak load contributions for the five hours designated as transmission peak capacity hours. (See PLC Peak Hours & Defaults)
Examples of Peak Load Contribution Calculations
There are four Excel® files illustrating the procedures for calculating PLCs for monthly metered, monthly demand metered and interval metered accounts, and for deriving reconciled load. For reference purposes, an Excel® spreadsheet named Customer PLC Datasheet Summary lists the kW values by customer account used in the calculation examples. The spreadsheets may be opened from this location or downloaded as a zipped file called PLC Reconciliation Worksheets (zip).