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: Arc Flash Hazard Calculation (planned, not yet available)

IEC Standards (future):

• IEC 60038: Standard voltages
• IEC 60909: Short-circuit current calculation
• IEC 60947: Low-voltage switchgear
• Future support planned

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 310.4):

• 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)):

• If calculated load falls between standard sizes
• Use next higher standard rating
• Exception: If next size up >800A and load <800A, must use load value

Motor protection (NEC 430.52):

• Inverse time breaker: 250% of motor FLC
• Instantaneous trip breaker: 800% (1300% for Design E)
• Inverse time fuse: 175% of motor FLC
• Dual element (time-delay) fuse: 175% of motor FLC
• If percentage doesn't correspond to standard size, next size up permitted

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: Infinite bus with specified MVA
• 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

Future standards support

Canadian Electrical Code (CEC):

• Similar structure to NEC
• Metric units
• Different table values
• Planned for future release

IEC 60364 (International):

• European and international standard
• Different voltage levels
• Metric conductor sizes (mm²)
• Alternative calculation methods

Standard deviations

Custom reference tables:

• Organizations can override system tables
• Apply organization-specific values
• Alternative code books (CEC, local amendments)
• See Customizing tables

When to deviate:

• Local jurisdiction amendments
• Company engineering standards
• Conservative design requirements
• Alternative international codes

Documentation requirements:

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

Standards version tracking

NEC edition:

• System default: NEC 2026
• Project-specific: Set in project settings
• Organization default: Set in org settings

Future versions:

• NEC 2029 when published
• Backward compatibility with NEC 2023, 2020
• Table value updates
• Calculation method changes

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