The document includes the following information:
Basic explanations of TTC, ATC, and TRM
List of VT TRANSCO'S POR's /POD's and forecast/posting responsibilities
Methods of determining TTC and TRM for each POR / POD.
| Total Transfer Capability (TTC) |
| NERC Definition |
The Total Transfer Capability (TTC) for an interface is the best engineering estimate of the total amount of electric power that can be transferred over the interface in a reliable manner in a given time-frame. |
| Basis for TTC |
There is no calculation for VT TRANSCO's TTCs. The TTC's for VT TRANSCO'S lines are non-constrained facilities and are not limited. To this end, the posting for VELCO's TTC's are 9999. |
| Transmission Reliability Margin (TRM) |
| Definition |
The Transmission Reliability Margin (TRM) is the portion of TTC that cannot be used for reservation of firm transmission service because of uncertainties in system operation. VELCO TRM posts a TRM = 0. |
| Available Transfer Capability (ATC) |
| Definition of Firm ATC |
Firm Available Transfer Capability (Firm ATC) for an interface is the capability for firm transmission reservations that remains after allowing for existing firm commitments and the TRM. Mathematically, since VT TRANSCO's TRM=0, Firm ATC is calculated using the equation: Firm ATC = TTC - Existing Firm Commitments. |
Capacity Benefit Margin
(CBM) not included |
For VT TRANSCO, 'Existing Firm Commitments' means the existing firm transmission reservations. VT TRANSCO does not include a CBM component in any ATC calculations, because the CBM is reflected in the capacity requirements of load-serving entities. |
| Definition of Non-Firm ATC |
Non-Firm Available Transfer Capability (Non-Firm ATC) for an interface is the capability for non-firm transmission reservations that remains after allowing for all existing commitments. Mathematically, Non-Firm ATC is calculated using the equation: Non-Firm ATC = TTC-All Existing Firm & Non-Firm Commitments |
| VT TRANSCO Transmission Provider Responsibility |
VT TRANSCO calculates and updates Firm and Non-Firm ATCs for service in accordance with the VT TRANSCO Point to Point transmission tariff. The tariff represents all radial lines emanating from the PTF to the load serving entities. |
The eight interfaces for which ATC values are currently posted on the VT TRANSCO OASIS node are listed in the table below. Some of these interfaces consist of a single tie and others have multiple ties.
| POR's / POD's |
Transmission Providers |
Comments |
| VT.LN.BED |
Burlington Electric Department |
|
| VT.LN.CVPS |
Central Vermont Public Service |
|
| |
|
|
| VT.LN.GMP |
Green Mountain Power Corp |
|
| VT.LN.SWAN |
Swanton Electric Lighting Co |
|
| NEPOOL.PTF |
Vermont Electric Power Co |
|
| NEPOOL.PTF |
NEPOOL.RTG |
|
| HIGHGATE.DC |
Central Vermont Public Service, Green Mountain Power Corp, Vermont Public Power Auth, Burlington Electric Dept, Village of Johnson W & L, Citizens Utilities Company, Rochester Electric L & P |
Tie to Highgate Converter | |