The Forecasting API operations define the exchange of forecasted ratings, including the 240-hour-ahead forecasted AAR data exchange required by FERC Order 881. The operations support submitting rating proposals, querying in-use limits, and monitoring the health and validity of submissions against the Rating Provider's obligations.
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openapi: 3.2.0
info:
title: Transmission Ratings and Operating Limits Information Exchange (TROLIE) Forecasting API
x-logo:
altText: TROLIE logo
url: images/TROLIE-horizontal-color.svg
description: "\nThis specification defines a set of operations for the exchange of power\nsystem ratings and limits between entities that own and operate the electric\npower system in North America. In particular, it is designed to support the\nexchange of Ambient Adjusted Ratings (AARs), pursuant to FERC Order 881. It\nis published as a community standard to facilitate interoperability\nin these exchanges.\n\nThe specification conceives of the exchange as being between two primary\nentities:\n\n* A [Ratings Provider](https://trolie.energy/concepts#ratings-provider) is\n an entity that is responsible for providing ratings on some set of power\n system resources, e.g., Transmission Facilities, typically a Transmission\n Owner or Transmission Operator. The ratings are provided to a\n Clearinghouse Provider whose is responsible for determining the operating\n limits of the power system resources.\n\n* The [Clearinghouse Provider](https://trolie.energy/concepts#clearinghouse-provider) is\n typically a Transmission Provider (FERC) and a Reliability Coordinator (NERC).\n\nAdjacent Clearinghouse Providers exchange ratings in order to establish\noperating limit values for the power system resources that are shared\nbetween them.\n\nA Ratings Provider is assumed by this specification to have pre-coordinated \nwith a Clearinghouse Provider to identify the former's Ratings Obligation,\ni.e., the set of power system resources for which they will provide ratings.\nAdditionally, the Ratings Provider will have similarly pre-coordinated the\ndefinition of their Monitoring Sets, i.e., their power system limits of\ninterest. The nature and method of pre-coordination is out-of-scope for this\nspecification.\n\nNote that this API makes a strict distinction between the terms rating and\nlimit. Colloquially, these terms are often used interchangeably. However,\nin the context of this specification, they have distinct meanings. At a\nhigh-level, the specification defines an exchange where ratings go in and\nlimits come out. A Clearinghouse is a function for determining the operating\nlimits from the ratings it has on-hand, including those that are proposed by\nRatings Providers and any applicable time-bound static ratings.\n\nThis interaction diagram highlights the primary requests and responses that\nare defined in this spec. Note that not all of the operations will be\nsupported by every implementation.\n\n<img src=\"images/interactions.excalidraw.png\" alt=\"Primary Interactions with Ratings Provider\" />\n"
version: 1.1.0
contact:
name: TROLIE Maintainers
email: maintainers@trolie.energy
url: https://trolie.energy
license:
name: Community Specification License 1.0
url: https://spdx.org/licenses/Community-Spec-1.0.html
servers:
- url: https://trolie.example.com
security:
- oauth2-primary-flow: []
tags:
- name: Forecasting
description: 'The Forecasting API operations define the exchange of forecasted ratings,
including the 240-hour-ahead forecasted AAR data exchange required by FERC
Order 881. The operations support submitting rating proposals, querying
in-use limits, and monitoring the health and validity of submissions
against the Rating Provider''s obligations.
'
paths:
/limits/forecast-snapshot:
get:
operationId: getLimitsForecastSnapshot
summary: Limits Forecast Snapshot
tags:
- Forecasting
parameters:
- $ref: '#/components/parameters/offset-period-start'
- $ref: '#/components/parameters/period-end'
- $ref: '#/components/parameters/query-filter'
- $ref: '#/components/parameters/resource-id-filter'
- $ref: '#/components/parameters/static-only'
- $ref: '#/components/parameters/temporal-resolution'
description: "\nReturns the latest Limits Forecast the clearinghouse has produced.\n\nThis content of the response varies significantly based on the media type requested.\n\n* `application/vnd.trolie.forecast-limits-snapshot.v1+json` simply includes the limits.\n* For use cases that require understanding *how* the limits were determined,\n the media type `application/vnd.trolie.forecast-limits-detailed-snapshot.v1+json`\n is available; it contains the ratings proposals and other factors used to\n generate the limits.\n\nBoth of these media types support the `include-psr-header` parameter. This\nis a boolean parameter that defaults to `true`. When set to `false`, the\n`power-system-resource` header is omitted. This can result in smaller\npayloads when the client already knows the resource ids in use by the\nClearinghouse Provider.\n\n```http\nGET /limits/forecast-snapshot HTTP/1.1\nAccept: application/vnd.trolie.forecast-limits-detailed-snapshot.v1+json; include-psr-header=false\n```\n\n### Slim Format\n\nThe `application/vnd.trolie.forecast-limits-snapshot-slim.v1+json` media type\nmay be used to request a more concise representation of the data. The\nmedia type parameter `limit-type` is required to specify the type of limit\nbeing requested, for example:\n\n```http\nGET /limits/forecast-snapshot HTTP/1.1\nAccept: application/vnd.trolie.forecast-limits-snapshot-slim.v1+json; limit-type=apparent-power\n```\nAdditionally, the `inputs-used` parameter may be set to `true` to include\nthe inputs used to generate the forecast.\n```http\nGET /limits/forecast-snapshot HTTP/1.1\nAccept: application/vnd.trolie.forecast-limits-snapshot-slim.v1+json; limit-type=apparent-power; inputs-used=true\n```\n\nNote this format is much more concise but requires significant care in\nprocessing. See [Using Slim Media\nTypes](../example-narratives/using-slim-media-types) for more details.\n\nClients SHOULD perform Conditional `GET` using the `If-None-Match` header\nand the `ETag` of a previous `GET` response to poll this endpoint. Rate\nlimiting is done on a per Ratings Provider basis, so requests from\nindependent clients used by the same provider count against the same\nquota.\n"
responses:
'200':
description: The requested operating forecast snapshot is returned.
content:
application/vnd.trolie.forecast-limits-snapshot.v1+json:
schema:
$ref: '#/components/schemas/forecast-limits-snapshot'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
source:
provider: X-AMPL
last-updated: '2023-07-12T16:00:00-07:00'
origin-id: //trolie.example.com/snapshots/2024-08-05T11%3a00%3a00-07%3a00
default-emergency-durations:
- name: LTE
duration-minutes: 240
- name: STE
duration-minutes: 30
- name: DAL
duration-minutes: 15
power-system-resources:
- resource-id: 8badf00d
alternate-identifiers:
- name: segmentX
authority: TO-NERC-ID
- name: LINE1 SEG-X
authority: RC-NERC-ID
mrid: 8badf00d
limits:
- resource-id: 8badf00d
periods:
- period-start: '2023-07-12T16:00:00-07:00'
period-end: '2023-07-12T17:00:00-07:00'
continuous-operating-limit:
mw: 160
pf: 1
emergency-operating-limits:
- duration-name: LTE
limit:
mw: 170
pf: 1
- duration-name: STE
limit:
mw: 180
pf: 1
- duration-name: DAL
limit:
mw: 190
pf: 1
application/vnd.trolie.forecast-limits-snapshot.v1+json; include-psr-header=false:
schema:
$ref: '#/components/schemas/forecast-limits-snapshot-elide-psr'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
source:
provider: X-AMPL
last-updated: '2023-07-12T16:00:00-07:00'
origin-id: //trolie.example.com/snapshots/2024-08-05T11%3a00%3a00-07%3a00
default-emergency-durations:
- name: LTE
duration-minutes: 240
- name: STE
duration-minutes: 30
- name: DAL
duration-minutes: 15
limits:
- resource-id: 8badf00d
periods:
- period-start: '2023-07-12T16:00:00-07:00'
period-end: '2023-07-12T17:00:00-07:00'
continuous-operating-limit:
mw: 160
pf: 1
emergency-operating-limits:
- duration-name: LTE
limit:
mw: 170
pf: 1
- duration-name: STE
limit:
mw: 180
pf: 1
- duration-name: DAL
limit:
mw: 190
pf: 1
application/vnd.trolie.forecast-limits-snapshot-slim.v1+json; limit-type=apparent-power:
schema:
$ref: '#/components/schemas/forecast-limits-snapshot-slim'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
ends: '2023-07-12T18:00:00-07:00'
source:
provider: X-AMPL
last-updated: '2023-07-12T16:00:00-07:00'
origin-id: //trolie.example.com/snapshots/2024-08-05T11%3a00%3a00-07%3a00
default-emergency-durations:
- name: LTE
duration-minutes: 240
- name: STE
duration-minutes: 30
- name: DAL
duration-minutes: 15
power-system-resources:
- resource-id: 8badf00d
alternate-identifiers:
- name: segmentX
authority: TO-NERC-ID
- name: LINE1 SEG-X
authority: RC-NERC-ID
mrid: 8badf00d
- resource-id: f34d3d
alternate-identifiers:
- name: segmentY
authority: TO-NERC-ID
- name: LINE2 SEG-Y
authority: RC-NERC-ID
mrid: 8badf00d
limits:
- - - 160
- 1
- 170
- 1
- 180
- 1
- 190
- 1
- - 161
- 1
- 171
- 1
- 181
- 1
- 191
- 1
- - - 140
- 1
- 150
- 1
- 160
- 1
- 170
- 1
- - 141
- 1
- 151
- 1
- 161
- 1
- 171
- 1
application/vnd.trolie.forecast-limits-snapshot-slim.v1+json; limit-type=apparent-power; inputs-used=true:
schema:
$ref: '#/components/schemas/forecast-limits-snapshot-slim-inputs-used'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
ends: '2023-07-12T18:00:00-07:00'
source:
provider: X-AMPL
last-updated: '2023-07-12T16:00:00-07:00'
origin-id: //trolie.example.com/snapshots/2024-08-05T11%3a00%3a00-07%3a00
default-emergency-durations:
- name: LTE
duration-minutes: 240
- name: STE
duration-minutes: 30
- name: DAL
duration-minutes: 15
power-system-resources:
- resource-id: 8badf00d
alternate-identifiers:
- name: segmentX
authority: TO-NERC-ID
- name: LINE1 SEG-X
authority: RC-NERC-ID
mrid: 8badf00d
- resource-id: f34d3d
alternate-identifiers:
- name: segmentY
authority: TO-NERC-ID
- name: LINE2 SEG-Y
authority: RC-NERC-ID
mrid: 8badf00d
limits:
- - - 160
- 1
- 170
- 1
- 180
- 1
- 190
- 1
- - 161
- 1
- 171
- 1
- 181
- 1
- 191
- 1
- - - 140
- 1
- 150
- 1
- 160
- 1
- 170
- 1
- - 141
- 1
- 151
- 1
- 161
- 1
- 171
- 1
inputs-used:
- name: dry bulb temperature (Fahrenheit)
unit: degF
values:
- - 50
- 51
- 52
- 53
- - 46.1
- 46.5
- 47.1
- 48
application/vnd.trolie.forecast-limits-detailed-snapshot.v1+json:
schema:
$ref: '#/components/schemas/forecast-limits-detailed-snapshot'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
source:
provider: X-AMPL-RC
last-updated: '2024-07-12T16:00:00-07:00'
origin-id: //trolie.example.com/snapshots/2024-08-05T11%3a00%3a00-07%3a00
default-emergency-durations:
- name: LTE
duration-minutes: 240
- name: STE
duration-minutes: 30
- name: DAL
duration-minutes: 15
power-system-resources:
- resource-id: 8badf00d
alternate-identifiers:
- name: segmentX
authority: TO-NERC-ID
- name: LINE1 SEG-X
authority: X-AMPL-RC
mrid: 8badf00d
limits:
- resource-id: 8badf00d
periods:
- period-start: '2023-07-12T16:00:00-07:00'
period-end: '2023-07-12T17:00:00-07:00'
additional-data:
vendor-specific-data: {}
continuous-operating-limit:
mva: 160
emergency-operating-limits:
- duration-name: LTE
limit:
mva: 165
- duration-name: STE
limit:
mva: 170
- duration-name: DAL
limit:
mva: 180
provenance:
- resource-id: 8badf00d
proposals-considered:
- resource-id: 8badf00d-UTILITY-A-SEG-id
source:
last-updated: '2023-07-12T16:00:00-07:00'
provider: UTILITY-A
origin-id: 8badf00d-UTILITY-A-correlation-id
period-start: '2023-07-12T16:00:00-07:00'
period-end: '2023-07-12T17:00:00-07:00'
continuous-operating-limit:
mva: 150
emergency-operating-limits:
- duration-name: LTE
limit:
mva: 160
- duration-name: STE
limit:
mva: 165
- duration-name: DAL
limit:
mva: 170
inputs-used:
- name: wind-speed
unit: mph
value: 5.2
- name: wind-direction
unit: degrees
value: 277.5
- name: temperature
unit: F
value: 72.1
temporary-aar-exceptions:
- id: https://trolie.example.com/temporary-aar-exceptions/1234
source:
origin-id: 2d8c80e8-f533-4be9-85bf-f7f81eb73d67
provider: UTILITY-A
last-updated: '2025-07-12T16:00:00-07:00'
resource:
resource-id: 8badf00d
start-time: '2025-07-12T16:00:00-07:00'
end-time: '2025-08-01T00:00:00-07:00'
continuous-operating-limit:
mva: 160
emergency-operating-limits:
- duration-name: LTE
limit:
mva: 165
- duration-name: STE
limit:
mva: 170
- duration-name: DAL
limit:
mva: 180
overrides:
- continuous-operating-limit:
mva: 160
emergency-operating-limits:
- duration-name: LTE
limit:
mva: 165
reason: TOI 20250701-01
start-time: '2025-07-01T00:00:00-07:00'
application/vnd.trolie.forecast-limits-detailed-snapshot.v1+json; include-psr-header=false:
schema:
$ref: '#/components/schemas/forecast-limits-detailed-snapshot-elide-psr'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
source:
provider: X-AMPL-RC
last-updated: '2024-07-12T16:00:00-07:00'
origin-id: //trolie.example.com/snapshots/2024-08-05T11%3a00%3a00-07%3a00
default-emergency-durations:
- name: LTE
duration-minutes: 240
- name: STE
duration-minutes: 30
- name: DAL
duration-minutes: 15
limits:
- resource-id: 8badf00d
periods:
- period-start: '2023-07-12T16:00:00-07:00'
period-end: '2023-07-12T17:00:00-07:00'
additional-data:
vendor-specific-data: {}
continuous-operating-limit:
mva: 160
emergency-operating-limits:
- duration-name: LTE
limit:
mva: 165
- duration-name: STE
limit:
mva: 170
- duration-name: DAL
limit:
mva: 180
provenance:
- resource-id: 8badf00d
proposals-considered:
- resource-id: 8badf00d-UTILITY-A-SEG-id
source:
last-updated: '2023-07-12T16:00:00-07:00'
provider: UTILITY-A
origin-id: 8badf00d-UTILITY-A-correlation-id
period-start: '2023-07-12T16:00:00-07:00'
period-end: '2023-07-12T17:00:00-07:00'
continuous-operating-limit:
mva: 150
emergency-operating-limits:
- duration-name: LTE
limit:
mva: 160
- duration-name: STE
limit:
mva: 165
- duration-name: DAL
limit:
mva: 170
temporary-aar-exceptions:
- id: https://trolie.example.com/temporary-aar-exceptions/1234
source:
origin-id: 2d8c80e8-f533-4be9-85bf-f7f81eb73d67
provider: UTILITY-A
last-updated: '2025-07-12T16:00:00-07:00'
resource:
resource-id: 8badf00d
start-time: '2025-07-12T16:00:00-07:00'
end-time: '2025-08-01T00:00:00-07:00'
continuous-operating-limit:
mva: 160
emergency-operating-limits:
- duration-name: LTE
limit:
mva: 165
- duration-name: STE
limit:
mva: 170
- duration-name: DAL
limit:
mva: 180
overrides:
- continuous-operating-limit:
mva: 160
emergency-operating-limits:
- duration-name: LTE
limit:
mva: 165
reason: TOI 20250701-01
start-time: '2025-07-01T00:00:00-07:00'
headers:
X-Rate-Limit-Limit:
$ref: '#/components/headers/X-Rate-Limit-Limit'
X-Rate-Limit-Remaining:
$ref: '#/components/headers/X-Rate-Limit-Remaining'
X-Rate-Limit-Reset:
$ref: '#/components/headers/X-Rate-Limit-Reset'
ETag:
$ref: '#/components/headers/ETag'
'304':
$ref: '#/components/responses/304'
'400':
$ref: '#/components/responses/400-problem'
'401':
$ref: '#/components/responses/401-empty'
'403':
$ref: '#/components/responses/403-empty'
'404':
$ref: '#/components/responses/404-empty'
'406':
$ref: '#/components/responses/406'
'422':
description: Unprocessable Content. The requested `temporal_resolution` is not supported.
headers:
X-Rate-Limit-Limit:
$ref: '#/components/headers/X-Rate-Limit-Limit'
X-Rate-Limit-Remaining:
$ref: '#/components/headers/X-Rate-Limit-Remaining'
X-Rate-Limit-Reset:
$ref: '#/components/headers/X-Rate-Limit-Reset'
content:
application/problem+json:
schema:
type: object
allOf:
- properties:
supported-values:
type: array
maxItems: 100
items:
$ref: '#/components/schemas/schema'
- $ref: '#/components/schemas/problem'
required:
- supported-values
example:
type: //trolie.example.com/spec/client-errors/422/unsupported-temporal-resolution
title: Unsupported Temporal Resolution
status: 422
detail: The requested `temporal-resolution` 'PT1M' is not supported. Please choose from the list of supported values.
instance: /forecast?temporal-resolution=PT1M
supported-values:
- PT1H
- P1D
- P1W
- P1M
'429':
$ref: '#/components/responses/429-empty'
'500':
$ref: '#/components/responses/500-empty'
default:
$ref: '#/components/responses/500-empty'
security:
- oauth2-primary-flow:
- read:operating-snapshot
/limits/forecast-snapshot/{period}:
get:
operationId: getHistoricalLimitsForecastSnapshot
summary: Historical Limits Forecast Snapshot
tags:
- Forecasting
parameters:
- $ref: '#/components/parameters/offset-period-start'
- $ref: '#/components/parameters/period-end'
- $ref: '#/components/parameters/query-filter'
- $ref: '#/components/parameters/resource-id-filter'
- $ref: '#/components/parameters/static-only'
- $ref: '#/components/parameters/temporal-resolution'
- name: period
description: 'Returns the Forecast Limits snapshot for the period requested rather
than the current snapshot.
'
in: path
required: true
schema:
$ref: '#/components/schemas/period-start'
description: '
Obtain the Limits Forecast the Transmission Provider used or is currently
using in Operations as of the period requested.
See the [Limits Forecast Snapshot](#tag/Forecasting/operation/getLimitsForecastSnapshot)
operation for more information.
'
responses:
'200':
description: The requested operating forecast snapshot is returned.
content:
application/vnd.trolie.forecast-limits-snapshot.v1+json:
schema:
$ref: '#/components/schemas/forecast-limits-snapshot'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
source:
provider: X-AMPL
last-updated: '2023-07-12T16:00:00-07:00'
origin-id: //trolie.example.com/snapshots/2024-08-05T11%3a00%3a00-07%3a00
default-emergency-durations:
- name: LTE
duration-minutes: 240
- name: STE
duration-minutes: 30
- name: DAL
duration-minutes: 15
power-system-resources:
- resource-id: 8badf00d
alternate-identifiers:
- name: segmentX
authority: TO-NERC-ID
- name: LINE1 SEG-X
authority: RC-NERC-ID
mrid: 8badf00d
limits:
- resource-id: 8badf00d
periods:
- period-start: '2023-07-12T16:00:00-07:00'
period-end: '2023-07-12T17:00:00-07:00'
continuous-operating-limit:
mw: 160
pf: 1
emergency-operating-limits:
- duration-name: LTE
limit:
mw: 170
pf: 1
- duration-name: STE
limit:
mw: 180
pf: 1
- duration-name: DAL
limit:
mw: 190
pf: 1
application/vnd.trolie.forecast-limits-snapshot.v1+json; include-psr-header=false:
schema:
$ref: '#/components/schemas/forecast-limits-snapshot-elide-psr'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
source:
provider: X-AMPL
last-updated: '2023-07-12T16:00:00-07:00'
origin-id: //trolie.example.com/snapshots/2024-08-05T11%3a00%3a00-07%3a00
default-emergency-durations:
- name: LTE
duration-minutes: 240
- name: STE
duration-minutes: 30
- name: DAL
duration-minutes: 15
limits:
- resource-id: 8badf00d
periods:
- period-start: '2023-07-12T16:00:00-07:00'
period-end: '2023-07-12T17:00:00-07:00'
continuous-operating-limit:
mw: 160
pf: 1
emergency-operating-limits:
- duration-name: LTE
limit:
mw: 170
pf: 1
- duration-name: STE
limit:
mw: 180
pf: 1
- duration-name: DAL
limit:
mw: 190
pf: 1
application/vnd.trolie.forecast-limits-snapshot-slim.v1+json; limit-type=apparent-power:
schema:
$ref: '#/components/schemas/forecast-limits-snapshot-slim'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
ends: '2023-07-12T18:00:00-07:00'
source:
provider: X-AMPL
last-updated: '2023-07-12T16:00:00-07:00'
origin-id: //trolie.example.com/snapshots/2024-08-05T11%3a00%3a00-07%3a00
default-emergency-durations:
- name: LTE
duration-minutes: 240
- name: STE
duration-minutes: 30
- name: DAL
duration-minutes: 15
power-system-resources:
- resource-id: 8badf00d
alternate-identifiers:
- name: segmentX
authority: TO-NERC-ID
- name: LINE1 SEG-X
authority: RC-NERC-ID
mrid: 8badf00d
- resource-id: f34d3d
alternate-identifiers:
- name: segmentY
authority: TO-NERC-ID
- name: LINE2 SEG-Y
authority: RC-NERC-ID
mrid: 8badf00d
limits:
- - - 160
- 1
- 170
- 1
- 180
- 1
- 190
- 1
- - 161
- 1
- 171
- 1
- 181
- 1
- 191
- 1
- - - 140
- 1
- 150
- 1
- 160
- 1
- 170
- 1
- - 141
- 1
- 151
- 1
- 161
- 1
- 171
- 1
application/vnd.trolie.forecast-limits-snapshot-slim.v1+json; limit-type=apparent-power; inputs-used=true:
schema:
$ref: '#/components/schemas/forecast-limits-snapshot-slim-inputs-used'
example:
snapshot-header:
begins: '2023-07-12T16:00:00-07:00'
ends: '2023-07-12T18:00:00-07:00'
source:
provider: X-AMPL
last-updated: '2023-07-12T16:00:00-07:00'
# --- truncated at 32 KB (149 KB total) ---
# Full source: https://raw.githubusercontent.com/api-evangelist/spp/refs/heads/main/openapi/spp-forecasting-api-openapi.yml