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Research — Generation / DER Interconnection · Early Access

IEEE 1547 and FERC interconnection checks that cite the clause they apply.

The generation-side harness, scoped in phase one to distributed generation (solar, storage, small wind) interconnecting under IEEE 1547. Deterministic checks compare a design value to a sourced limit and return a compliance result with the cited clause, an optional jurisdiction or utility override, and a note on how well the source is verified.

IEEE 1547 · FERC Orders 827/842 · TM 5-811-6

Interactive demos

Harnesses in action

Scripted chat-and-viewer examples where this domain's harness is one of the tools. Illustrative, not live sessions.

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What it can do

  • check_der_cease_to_energize_time

    Unintentional-islanding trip time against the 2.0 s default (IEEE 1547-2018 Clause 8.1.1), with a utility override up to 5.0 s.

  • check_der_voltage_ride_through_zone

    Category I/II/III four-zone voltage ride-through (Clause 6.4.2.1).

  • check_der_rocof_ride_through

    Category-dependent rate-of-change-of-frequency ride-through floor (Clause 6.5.2.5).

  • check_poi_fault_contribution_adequacy

    Point-of-interconnection interrupting rating against combined utility and DER fault current (NEC 705.16, 110.9).

  • check_der_fast_track_15_percent_screen

    Aggregate generation on a line section against 15% of peak load (FERC SGIP 2.2.1.2).

  • check_lgi_primary_frequency_response_settings

    Large-generator governor droop and deadband per FERC Order 842.

Design workflow

A staged generation-plant design that hands its fault contribution to the substation.

Six routes walk a plant through stages, including propose and decide for fixes. You send the whole design state in and get the new state back; nothing is stored between calls. The result of the last stage is a versioned hand-off the substation design consumes: the generator’s fault contribution is added to the utility’s source level, never substituted for it.

5 stages, drawn from the harness’s own dependency graph (5 of the 15 stages in its workflow map of TM 5-811-6 are built). Every stage reads the design basis; an arrow means a stage also needs the one it points from, so stages in the same column do not depend on each other.

  1. 1. Design basisdesign_basis

    Takes the generation-plant design basis once; every later stage reads it from the state.

    Validates
    Records the design basis and reports which inputs are still missing.
    Needs
    the design basis
    Can reportvalidincomplete
  2. 2. Generatorgenerator

    Rated MW and lagging Mvar from the nameplate, and the subtransient fault current at the terminals.

    Validates
    Deviations from the manual’s kVA multipliers and standard power factors are advisory notes, not failures.
    Cites
    TM 5-811-6 (1984)
    Needs
    the design basis
    Can reportvalidincomplete
  3. 3. Step-up transformergsu

    Checks that the transformer does not limit station output, reports its ratio to the generator, and computes the generator’s fault contribution on the high side.

    Validates
    A transformer smaller than the net output is failed (a definitional comparison); the manual’s 115 to 120 percent ratio is advisory. The contribution is generator-only.
    Cites
    TM 5-811-6 (1984)
    Needs
    the design basis, and the result of generator
    Can reportvalidincompletefailedproposes fixes
  4. 4. Station servicestation_service

    The unit auxiliary transformer against your analysed auxiliary load plus the manual’s minimum margin for future additions.

    Validates
    An auxiliary transformer below the analysed load plus margin is failed; the 6 to 10 percent rule of thumb is advisory.
    Cites
    TM 5-811-6 (1984)
    Needs
    the design basis, and the result of generator
    Can reportfailedincompletenever validproposes fixes

    Never valid: load classification, motor starting and the startup or standby transformer are not evaluated.

  5. 5. Grid interfacegrid_interface

    Packages the generator, transformer, point-of-interconnection voltage and the generator-only fault contribution as the versioned hand-off; runs the large-generator governor droop and deadband check when you give the settings.

    Validates
    Droop and deadband against the FERC Order 842 limits (pro forma defaults unless a transmission-provider override applies); settings outside them are failed. The reactive-capability range check applies to inverter-based generators only.
    Cites
    TM 5-811-6 (1984); FERC Order 842
    Needs
    the design basis, and the result of generator and gsu
    Can reportfailedincompletenever validproposes fixes

    Never valid: reactive capability at the point of interconnection, the fault contribution’s X/R and stability are not evaluated.

Statuses:missing (the stage has not been run); valid (it ran and everything it evaluates passed); incomplete (it ran but could not evaluate something, and says what); failed (a comparison it did evaluate did not pass); stale (an input or an upstream stage changed since it ran).missing and stale apply to every stage.

Hand-off: The grid-interface stage builds a versioned hand-off object (contract version 1, generation_to_substation) for the substation design. It is generator-only: the grid source must be added to it, and a hand-off built from an incomplete or failed stage is still accepted.

Proposals, on request

For a transformer that limits output, the minimum rating that does not (and the rule-of-thumb size); for an auxiliary transformer below the analysed load plus margin, the minimum rating; for governor settings outside Order 842, the droop and deadband that pass. Each is re-checked by re-running the stages, and lists what else it changes, such as the transformer’s impedance on the generator base.

What was checked

Every sizing number was read from the TM 5-811-6 text and its rendered page images. The manual’s own worked example is outside the range for which it states a multiplier, so the stage reports it rather than judging it. Calculations are covered by hand-worked per-unit cases, and an independent per-unit calculation matched the high-side fault contribution.

What it does not do

  • The hand-off (contract v2) carries the status of the stages it was built from, a content hash and, when you give the generator and transformer X/R, a plant X/R. The substation refuses a hand-off built on a failed stage or edited after it was issued, but cannot tell that the generation design changed afterwards. Reactive output at the step-up transformer’s high side at rated MVA and power factor is computed (generator Mvar less the transformer’s series loss) but not judged; leading capability, the station-service reactive load and stability are not evaluated.
  • With no generator data you can pick a typical machine row (NPAG Table 5.1, unsaturated, third-party copy): missing X″d, X2 and X0 take the lower end of its range, each recorded as an assumption, and the hand-off is labelled a typical estimate. Inverter-based generators are a current limit (1.2 × rated for grid-following, 2 × for grid-forming, from Sandia test summaries), not a reactance. Replace these with the OEM datasheet or a test report.
  • Station-service load can come from an analysed figure, a load list (100% demand, no transformer losses) or a typical percent-of-gross row from two NETL plant designs (1.73% gas, 5.36% coal). Motor starting is a locked-rotor estimate from the NEMA code letter, judged only against a voltage limit you supply.
  • The manual’s sizing numbers are 1984 rules of thumb: deviations are advisory notes, not failures. Only the two definitional comparisons (transformer limiting output; auxiliary transformer below the analysed load plus margin) and the Order 842 check can fail a stage.
  • The Order 827 reactive-power range applies to inverter-based generators only and is reported as not applicable for synchronous units.
  • A proposed transformer rating is a minimum to meet, not a product; enter the selected unit’s real nameplate impedance afterwards.
  • Draft; no generation engineer has reviewed it.

Live in the REST API (generation harness v0.2.0, seven routes: the six above plus a fix proposal for a single failing check) and as MCP tools. A staged design never ends with every stage valid: the station-service and grid-interface stages can only be failed or incomplete. Draft.

Draft, unvalidated: no engineer has reviewed this workflow, and a stage result is a screening result, not a design approval.

A worked case

Input

Measured cease-to-energize trip time of 2.01 s.

Result

Not compliant: 2.01 s exceeds the 2 s maximum for unintentional islanding (IEEE 1547-2018 Clause 8.1.1). Exactly 2.0 s passes.

Where this stands

Draft, unvalidated. No DER interconnection or protection engineer has reviewed it; every function has only an AI-assisted pre-review. IEEE 1547-2018 is paywalled, so subclause numbers are mostly single-source. The FERC screens are confirmed against authoritative copies.

Open questions

  • Category III voltage ride-through clearing times were corrected after sources disagreed, and are the top item awaiting human review.
  • Whether IEEE 1547’s “before the first reclose interval” nuance changes the 8.1.1 clearing time is disputed between secondary sources.
  • The 10% fault-current screen has an unresolved ambiguity over whether the denominator includes the DER’s own contribution.
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