Electrical standards reference

ekx follows established electrical codes and standards for calculations, sizing, and analysis.

Primary standards

NEC 2026 (National Electrical Code):

• Default code book for United States
• Published by NFPA (National Fire Protection Association)
• Covers installation requirements, conductor sizing, protection
• Updated every 3 years
• Legally enforced by most US jurisdictions

IEEE Standards:

• IEEE 141 (Red Book): Electric Power Distribution for Industrial Plants
• IEEE 242 (Buff Book): Protection and Coordination
• IEEE 399 (Brown Book): Power System Analysis
• IEEE 551: Voltage Dips, Short Interruptions, Voltage Imbalance, Swells
• IEEE 1584-2018: Arc Flash Hazard Calculation, three-phase alternating current, 208 V to 15 kV

CEC 2024 (Canadian Electrical Code):

• Available as a project code book when you create a blank project

IEC Standards:

• IEC 60909: Short-circuit current calculation method

NEC articles referenced

ekx implements these NEC 2026 articles:

Cable sizing standards

NEC 310.16 Ampacity Tables:

• Copper and aluminum conductors
• 60°C, 75°C, 90°C temperature ratings
• Not more than three current-carrying conductors
• Ambient temperature 30°C
• System includes all tables

Temperature derating (NEC 310.15(B)(1)):

• Correction factors for ambient temperature
• Termination temperature limits ampacity
• 75°C terminations most common
• 90°C conductor insulation for derating calculations

Adjustment factors (NEC 310.15(C)(1)):

• More than 3 conductors in raceway/cable
• 4-6 conductors: 80% of ampacity
• 7-9 conductors: 70% of ampacity
• 10-20 conductors: 50% of ampacity
• 21-30 conductors: 45% of ampacity
• 31-40 conductors: 40% of ampacity

Parallel conductors (NEC 310.10(G)):

• Minimum 1/0 AWG per run
• Same length, material, size, insulation
• Terminated same manner
• Ampacity multiplied by number of runs

OCPD sizing standards

Standard sizes (NEC 240.6(A)):

15, 20, 25, 30, 35, 40, 45, 50, 60, 70, 80, 90, 100, 110, 125, 150, 175, 200,
225, 250, 300, 350, 400, 450, 500, 600, 700, 800, 1000, 1200, 1600, 2000,
2500, 3000, 4000, 5000, 6000 amperes

Next size up rule (NEC 240.4(B) and (C)):

• If the conductor ampacity does not match a standard rating, the next higher standard rating is permitted when it does not exceed 800 A and the other 240.4(B) conditions are met
• Above 800 A, the conductor ampacity must be equal to or greater than the OCPD rating

Motor protection (NEC 430.52, Table 430.52(C)(1)):

Maximum rating or setting of the motor branch-circuit short-circuit and ground-fault protective device, as a percentage of motor full-load current, for single-phase motors and AC polyphase motors other than wound-rotor:

• Wound-rotor motors are limited to 150% for fuses and inverse time breakers. DC motors are limited to 150%, or 250% for an instantaneous-trip breaker.
• If the percentage does not match a standard rating in 240.6, the next higher standard rating is permitted (430.52(C)(1)(a)).
• An instantaneous-trip breaker must be adjustable and part of a listed combination motor controller (430.52(C)(3)).

Power flow analysis standards

PandaPower implements:

• Newton-Raphson power flow (default)
• Based on IEEE and IEC methodologies
• Slack bus provides voltage reference
• Per-unit system for calculations
• Engineering units for results

Convergence criteria:

• Voltage tolerance: 1e-6 pu
• Power tolerance: 1e-6 MW/MVAR
• Maximum iterations: 100
• Voltage initialization: flat start (1.0 pu)

Assumptions:

• Balanced three-phase system
• Fundamental frequency (60 Hz US, 50 Hz international)
• Sinusoidal waveforms
• Positive-sequence network (no zero/negative sequence)

Short-circuit analysis standards

IEC 60909 method (PandaPower default):

• Three-phase fault current calculation
• Subtransient reactance for generators
• Transformer impedances on rated kVA
• Cable impedances from parameters
• Peak current calculation (kappa factor)

Fault current components:

• Ik'' (initial symmetrical short-circuit current)
• Ip (peak short-circuit current)
• Ib (symmetrical breaking current)
• Ith (thermal equivalent short-circuit current)

Source contributions:

• Utility feeds: Source impedance from the short-circuit MVA and X/R ratio you enter
• Generators: Finite source with Xd'' reactance
• Motors: Contribute ~4-6× FLA for first few cycles

Voltage standards

ANSI C84.1 voltage ranges:

Per-unit acceptable ranges:

• Normal operation: 0.95-1.05 pu
• Emergency: 0.90-1.10 pu
• Power flow violations flagged outside Range A

Conductor sizing standards

Continuous loads (NEC 210.19(A)(1)):

• Conductor ampacity ≥ 125% of continuous load
• Continuous load: Operates 3+ hours
• Prevents conductor overheating

Motor conductors (NEC 430.22):

• Ampacity ≥ 125% of motor full-load current
• Based on NEC table values, not nameplate
• Continuous duty assumed

Voltage drop recommendations (NEC Informational Note):

• Branch circuits: 3% maximum
• Feeders: 3% maximum
• Combined: 5% maximum
• Not a requirement, but good practice

IEC 60364 (International):

• Not currently available as a sizing profile.

Standard deviations

Custom reference tables:

• Organizations can override system tables
• Apply organization-specific values
• Remain within the project's selected code profile and are recorded as custom

data in sizing evidence

• See Customizing tables

When to deviate:

• Local jurisdiction amendments
• Company engineering standards
• Conservative design requirements

Custom tables cannot substitute for a registered CEC, IEC, or other electrical- code implementation. Confirm local amendments and acceptance with the AHJ.

Documentation requirements:

• Justify alternative values
• Get approval from AHJ (Authority Having Jurisdiction)
• Document in calculation reports

Code book per project

• New blank projects default to NEC 2026. Choose CEC 2024 under Electrical code when you

create the project.

• A project created from a template keeps the template's code book and edition.
• The code book cannot be changed after the project is created.

Certification and compliance

ekx calculations:

• Based on published code
• Not certified for legal submissions (user responsibility)
• Provides calculation basis
• Engineer must verify and stamp

Compliance responsibility:

• Licensed Professional Engineer (PE) must review
• Check local code amendments
• Verify AHJ requirements
• Sign and seal drawings

Calculation reports:

• Export results for documentation
• Include assumptions and references
• Show code article citations
• Support permitting process

Related topics

• Component properties - Property validation ranges
• Cable sizing - NEC ampacity calculations
• OCPD sizing - NEC protection sizing
• Customizing tables - Override code values