Page review information

Edition covered

cst toolkit documentation — standards citations are carried in each command's output — n/a — toolkit documentation

Content status

Review pending

Coverage

Documents the Python toolkit; SAMPLE-data outputs are illustrative and licensed table values are user-supplied, never bundled.

Last content update

August 2026

Technical validation

Not yet completed

Primary reference

The official published standard — required for final decisions

Confirm the governing edition, jurisdiction, and project-specific requirements before applying anything on this page.

Engineering Tools

Python Engineering Toolkit — cst

The open-source package that powers this project's templates: standards-cited calculators, a panel design pipeline, commissioning generators, PLC utilities, and diagnostics.

The toolkit lives in the same repository as this site: github.com/kyawminthu20/Control-System-Tools (src/cst/). Python 3.12+, standard library only at its core, with the test suite run as a release gate on every change.

git clone https://github.com/kyawminthu20/Control-System-Tools.git
cd Control-System-Tools
uv sync            # installs the cst CLI (or: pip install -e .)
uv run cst --help

Design Principles

1. Every result carries its citations. Calculators return the value plus the standard clauses, formulas, and assumptions behind it — ready to paste into design notes.
2. Licensed table values are never distributed. Rule logic is open; bulk table values (NEC ampacity, motor FLC, Bussmann C-values) load from files you transcribe from your own licensed copies. Clearly-marked sample data lets everything run out of the box — and warns you it’s sample data.
3. One I/O list drives everything. The panel and commissioning generators all consume the same CSV, so the BOM, wire schedule, loop sheets, and FAT protocol stay consistent with each other.

What It Does

Command	What it produces	Basis
cst voltage-drop / wire-size	Conductor voltage drop; minimum AWG for a drop target	NEC K-factor method; 210.19(A)/215.2(A) recommendations
cst ampacity	Allowable ampacity with ambient correction and bundle adjustment	NEC 310.15(B) equation, Table 310.15(C)(1)
cst motor-branch	Conductor, OCPD, and overload sizing for one motor	NEC Art. 430 chain (430.22, Table 430.52(C)(1), 240.6(A), 430.32)
cst transformer	Transformer FLA and OCPD limits	NEC Table 450.3(B)
cst sccr	Panel SCCR weakest-link assessment	UL 508A Supplement SB4; NEC 409.22 check
cst fault-current	Infinite-bus fault current + point-to-point attenuation	Bussmann method
cst enclosure / fan	Sealed-enclosure temperature rise; filter-fan airflow	IEC/TR 60890-style effective-surface method
cst encoder	Encoder scaling: counts ↔ units ↔ RPM ↔ linear speed	Kinematics
cst io-check	I/O list validation (duplicate tags, address conflicts)	—
cst bom / wire-schedule / legend	Panel design documents from the I/O list	NFPA 79 Ch. 16/19 conventions
cst loop-sheets / fat	Per-point loop test sheets; FAT/SAT protocol skeleton	ISA-style loop-check practice
cst tags-from-io / modbus-map	PLC tag database; Modbus register map	IEC 61131-3 identifier rules; Modbus data model
cst saleae	Pulse stats, glitch finder, quadrature decode from Logic 2 exports	—
cst modbus-decode	Offline Modbus TCP capture analysis: exception responses, unanswered requests, response latency, polled register spans	Modbus Application Protocol Specification V1.1b3
cst sbm	Similarity-based anomaly scores for sensor data	SBM-family kernel autoassociative model
cst twin-validate	Digital-twin payload against the data contract: required fields, requested authority vs the register ceiling, freshness	Corpus digital_twin.md §5; NIST SP 800-82r3
cst twin-sync	Synchronization health of twin telemetry: gaps, out-of-order arrivals, staleness, clock skew and drift	Corpus digital_twin.md §3 steps 2 and 4
cst design-package	One markdown design document stitching the above together	—

Example — the classic Article 430 chain for a 10 hp, 460 V motor:

$ cst motor-branch --hp 10 --volts 460 --nameplate-fla 13.2
Motor branch circuit — 10 hp, 460 V, 3-phase: 17.5 A (min conductor ampacity)
  table_flc_a: 14
  ocpd_max_calc_a: 35
  ocpd_rating_a: 35
  overload_max_a: 16.5
  overload_percent: 125
  Warnings:
    ! Loaded SAMPLE table data — demonstration values only; verify against a licensed copy and populate data/standards_tables/ before design use
  Assumptions:
    - Single continuous-duty motor; no other loads on the branch circuit
    - Service factor 1.15, temperature rise 40 degC
    - Nameplate FLA = 13.2 A
    - Select actual conductor size from ampacity tables (cst.calc.ampacity) with the installation's correction/adjustment factors
  References:
    - NEC 2023 Table 430.250 — table FLC 14 A — NEC (NFPA 70) 2023 Table 430.250 (SAMPLE data)
    - NEC 2023 430.22 — branch conductors >= 125 % of table FLC
    - NEC 2023 Table 430.52(C)(1) + Exc. 1 — inverse time breaker max 250 % of FLC, next standard size permitted
    - NEC 2023 240.6(A) — standard rating selected: 35 A
    - NEC 2023 430.32(A)(1) — overload at 125 % of nameplate FLA

The ! Loaded SAMPLE table data line is part of the real output, not site decoration. Until you transcribe NEC Table 430.250 from your own licensed copy into data/standards_tables/, the 14 A table FLC above is a demonstration value and the whole chain built on it is illustrative only.

Example — reading a Modbus TCP capture taken during an intermittent-dropout investigation:

$ cst modbus-decode capture.pcap --exceptions --unanswered
frames        : 13  (7 req / 6 resp)
unit ids      : 1
capture span  : 0.600 s
  Read Holding Registers            13
response time : mean 8.33 ms, max 10.00 ms
exceptions    : 1
unanswered    : 1

exception responses:
  t=1000.510000 unit=1 txn=6 Read Holding Registers: Illegal Data Address

unanswered requests: 1
  t=1000.600000 unit=1 txn=7 Read Holding Registers start=200 qty=2

--addresses lists the register spans the client actually polls, which you can diff against the design-time map from cst modbus-map.

Example — checking a digital-twin proposal before a gate would see it, and the synchronization health of the telemetry feeding it:

$ cst twin-validate payload.json --register methods.yml --method-id digital_twin_state_sync
3 problem(s):
  - missing required contract field "calibration_version" — which calibration the value rests on
  - requested_authority 3 exceeds the register ceiling 2 for this method
  - payload is stale: valid_until 1752960302.000 passed at 1752960500.000 (198 s late) — a gate must reject it

$ cst twin-sync telemetry.csv --max-age 5
Twin synchronization health: 60 samples over 70 s
  median interval: 1 s
  max gap: 12 s (1 gap(s) detected)
  out-of-order samples: 0
  stale samples: 0 (0.0%)
  mean skew: 0.1922 s (max |skew| 0.204 s)
  skew drift: 0.000309 s/s
  Warnings:
    ! 1 telemetry gap(s); longest 12 s at 1752960030.000 — twin state was unsynchronized across it

The authority ceiling comes from the AI method register, never from the payload’s own claim. See The Digital Twin for the contract and the maturity ladder these checks implement.

Limits

• Screening and design-assist calculations — final designs need the official standards, project-specific data, and engineering review.
• cst twin-validate and cst twin-sync report and never act. A clean result means a proposal is well-formed enough for a non-learned gate to judge, or that telemetry has the synchronization properties it claims — never that anything is safe or authorized. The gate that clamps or vetoes a proposal is plant-side engineering with its own integrity requirements, not a Python library.
• cst modbus-decode reads capture files offline and never opens a network interface. Taking the capture is a separate step: on a live OT segment use a passive method (a TAP or a switch mirror port) — active scanning or injected traffic can disturb a process that is controlling plant.
• Sample table data is for demonstration; transcribe licensed values before design use (the tool warns you until you do).
• Live PLC helpers (pycomm3 extra) read and verify only — they never write to a running controller.

See the templates page for documents generated by the toolkit that you can download directly.

Trust Boundary — Engineering Judgment Required

This site is an independent educational reference for industrial automation standards. It paraphrases and organizes guidance in original language; it is not a substitute for the official published standards, professional engineering judgment, or legal review, and content has not been independently verified against current published editions.

Items marked Review pending await technical review against the identified edition. Items marked Planned have no reviewed source material behind them. Do not rely on this site for compliance determinations, safety-critical design decisions, or legal interpretation.