Glossary
Electrical engineering and software terms used in ekx documentation and interface.
Electrical terms
Active power (P): Real power measured in watts (W), kilowatts (kW), or megawatts (MW). Power that performs useful work. Measured by kWh meters.
Ampacity: Maximum current-carrying capacity of a conductor in amperes, considering insulation temperature rating, ambient temperature, and installation conditions.
Apparent power (S): Total power in AC circuits measured in volt-amperes (VA), kilovolt-amperes (kVA), or megavolt-amperes (MVA). Vector sum of active and reactive power: S = √(P² + Q²).
Arc flash: Explosive release of energy during an electrical fault. Creates extreme heat, pressure wave, and light. Requires personal protective equipment (PPE) based on incident energy.
ATS (Automatic Transfer Switch): Switches between two power sources automatically based on voltage availability. Common for utility/generator backup systems.
Balanced system: Three-phase system where phase voltages and currents have equal magnitude and 120° phase separation. Assumed in most power system analysis.
Branch circuit: Circuit conductors between final overcurrent device and outlet(s) or load(s). Serves specific equipment or receptacles.
Bus (busbar): Common connection point where multiple circuits join. Distributes power from one point to multiple feeders. Can be physical conductor or electrical node.
Cable: Insulated conductor(s) for conducting electrical current. Includes conductor, insulation, and optional shielding or armor.
Circuit breaker: Overcurrent protection device that can be reset. Opens automatically on overload or fault. Manual operation for switching.
Conductor: Material that carries electric current. Copper (Cu) or aluminum (Al) most common. Sized by AWG or kcmil.
Continuous load: Load operating for 3 hours or longer. Requires conductor and OCPD sized at 125% of load current per NEC.
Delta (Δ) connection: Three-phase connection where ends connect in triangle. No neutral point. Line voltage equals phase voltage. Common in industrial distribution.
Demand factor: Ratio of maximum demand to total connected load. Accounts for diversity - not all loads operate simultaneously.
Diversity: Principle that total system load is less than sum of individual loads because they don't all operate at peak simultaneously.
Fault current: Current that flows during short-circuit or ground fault. Can be 10-100× normal current. Must be interrupted quickly.
Feeder: Circuit conductors between service equipment or source of a separately derived system and the final branch-circuit overcurrent device.
Full-load current (FLC): Current drawn by motor at rated horsepower and voltage under rated load conditions. From NEC Tables 430.248 and 430.250, not nameplate.
Fuse: One-time overcurrent protection device. Melts element to interrupt fault. Must be replaced after operation. Current-limiting types available.
Generator: Device that converts mechanical energy to electrical energy. Synchronous or induction type. Provides backup or primary power.
Ground fault: Unintended current path to ground. Phase conductor contacts grounded surface. Can cause fire or shock hazard.
Harmonics: Non-sinusoidal frequency components (multiples of fundamental 60 Hz). Caused by electronic loads. Increases heating in conductors and transformers.
Impedance (Z): Total opposition to AC current flow. Complex number combining resistance (R) and reactance (X): Z = R + jX. Measured in ohms (Ω).
Impedance percent (Z%): Transformer impedance as percentage of base impedance on rated kVA. Determines voltage regulation and limits fault current. Typical: 3-8%.
Inrush current: Initial surge current when energizing transformer or motor. Can be 5-12× normal current for transformers, 5-8× for motors. Lasts milliseconds to seconds.
Interrupting capacity (AIC): Maximum fault current a protective device can safely interrupt. Must exceed available fault current at installation location. Rated in kA.
Line-to-line voltage: Voltage between any two phase conductors in a three-phase system. 480V, 208V, 13.8kV typical.
Line-to-neutral voltage: Voltage between phase conductor and neutral in wye systems. √3 times lower than line-to-line voltage. 277V in 480Y/277V system.
Load: Device that consumes electrical power. Converts electrical energy to light, heat, mechanical work, or other forms.
Locked-rotor current (LRC): Current drawn by motor with rotor not turning (startup). Typically 5-8× full-load current. Used for motor starting calculations.
Motor: Device converting electrical energy to mechanical rotation. Induction (most common) or synchronous type. Three-phase or single-phase.
Nameplate: Manufacturer's data plate showing ratings and specifications. Actual ratings may differ from NEC table values for sizing purposes.
OCPD (Overcurrent Protective Device): Circuit breaker or fuse protecting against excessive current from overload or fault.
Overload: Current exceeding rated value but not a fault. Typically 105-125% of rating. Causes heating over time.
Per-unit (pu): Normalized quantity expressed as ratio to base value. Voltage in pu = actual voltage ÷ nominal voltage. Simplifies multi-voltage analysis.
Phase: One of the three conductors in a three-phase system (A, B, C). 120° electrical separation between phases.
Power factor (PF): Ratio of active power (kW) to apparent power (kVA): PF = P/S. Range 0-1.0. Lagging (inductive loads) typical. Unity (1.0) best.
Protection coordination: Selective operation of protective devices. Downstream device operates first, upstream remains closed. Minimizes outage area.
Reactance (X): Opposition to AC current from inductance (XL) or capacitance (XC). Imaginary component of impedance. Measured in ohms.
Reactive power (Q): Power oscillating between source and load. Measured in volt-amperes reactive (VAR), kilovolt-amperes reactive (kVAR), or megavolt-amperes reactive (MVAR). Does no useful work but required for magnetic fields.
Resistance (R): Opposition to current flow causing voltage drop and heating. Real component of impedance. Measured in ohms (Ω).
Service entrance: Point where utility power enters facility. Includes metering, main disconnect, and overcurrent protection.
Short-circuit: Very low impedance fault between phases or phase-to-ground. Causes extremely high current. Must be cleared in cycles.
Single-line diagram (SLD): Simplified electrical drawing showing major equipment and connections. Three-phase system shown as single line. Omits detailed wiring.
Slack bus: Reference bus in power flow analysis with fixed voltage magnitude and angle (usually 1.0∠0° pu). Balances system power. Usually utility feed or largest generator.
Switchgear: Assembly of circuit breakers, disconnect switches, and instruments. Metal-enclosed for safety. Low-voltage (<1kV) or medium-voltage.
Synchronous: Generator or motor whose rotor speed is synchronized with supply frequency. Constant speed regardless of load.
Three-phase: AC power system with three voltage sources 120° apart. More efficient than single-phase for power transmission and motors.
Transformer: Device transferring electrical energy between two or more windings through electromagnetic induction. Changes voltage levels. Provides isolation.
Utilization voltage: Voltage level at which equipment operates. Low voltage: 120V-600V. Medium voltage: >1kV to 35kV. High voltage: >35kV.
Utility feed: Connection point to external electrical grid. Provides primary power. Modeled as infinite bus (constant voltage source).
Voltage drop: Reduction in voltage between two points due to conductor resistance and reactance. Limited to 3-5% per NEC recommendations.
Voltage regulation: Change in voltage from no-load to full-load expressed as percentage. Good regulation: <3%. Poor regulation: >5%.
Wye (Y) connection: Three-phase connection with common neutral point. Line voltage √3 × phase voltage. 480Y/277V, 208Y/120V common. Four-wire with neutral.
X/R ratio: Ratio of reactance to resistance. Affects fault current decay and arc flash energy. Typical: 3-8 for LV, 10-20 for MV, 15-30 for HV.
Software terms
Auto-connect: Feature that automatically creates connections between components dropped near each other. ~300px proximity threshold. Disabled with Shift key.
Canvas: Drawing area where electrical components are placed and connected. Uses React Flow for rendering. Supports pan, zoom, snap-to-grid.
Component: Electrical equipment represented on the canvas. Examples: bus, cable, transformer, load, motor, breaker, fuse, generator, utility feed.
Component defaults: Pre-configured values for new components. Four-tier hierarchy: System → Organization → Project → User. Higher tiers override lower.
Connection: Electrical conductor between two components. Represented visually as line or edge. Stored in database with from/to component IDs and handle positions.
Convergence: Achievement of solution in iterative power flow calculation. When voltage/power changes between iterations fall below tolerance. Failure indicates modeling issue.
Edge: React Flow term for connection line between nodes. In ekx: represents cables, electrical connections, or power flow paths.
Handle: Connection point on component where connections attach. Top/bottom/left/right positions. Can be single or multiple per side.
Handle side: Position of handle on component: top, bottom, left, right. Determines connection direction and visual routing.
Local state: Component positions and properties maintained in browser for smooth UI. Syncs with database but allows immediate UI response during drag.
Migration: Database schema change tracked by Drizzle. SQL file defining table/column additions, modifications, or deletions. Applied sequentially.
Node: React Flow term for visual component on canvas. In ekx: bus, transformer, load, or any electrical component.
Organization: Group of users sharing projects, settings, and billing. Personal (single user) or team (multiple users). Every user belongs to at least one organization.
Project: Container for single electrical system model. Includes components, connections, canvas state, calculation results. Owned by organization.
Proximity threshold: Distance (~300px) within which auto-connect activates. Components closer than threshold may auto-connect on drop.
Reference table: Code-mandated data table (NEC ampacity, motor FLC, adjustment factors) used in sizing calculations. Can be customized at org/user scope.
Role: Permission level for organization or project access. Organization: Owner, Admin, Billing Admin, Member. Project: Owner, Editor, Viewer.
Row Level Security (RLS): PostgreSQL security policy filtering database rows based on user. Ensures users only see/edit data they own or have permission to access.
Scope: Level at which setting or default applies: System (built-in), Organization (team-wide), Project (project-specific), User (personal).
Server action: Next.js function executing on server. Handles database operations, calculations, external API calls. Type-safe with Zod validation.
Sizing: Calculation of conductor size and OCPD rating based on NEC rules. Applies derating factors, multipliers, and standard sizes.
Slack bus: See electrical terms. Software marks utility feed or designated generator as slack for power flow reference voltage.
Validation: Check for electrical correctness before calculation. Identifies missing sources, orphaned components, voltage mismatches, incomplete data.
Viewport: Visible portion of canvas. Pan moves viewport, zoom changes scale. Position and zoom persist per user/project.
Abbreviations
AC: Alternating Current
AHJ: Authority Having Jurisdiction (local electrical inspector)
AIC: Ampere Interrupting Capacity
AL: Aluminum (conductor material)
ANSI: American National Standards Institute
AWG: American Wire Gauge (conductor sizing standard)
CEC: Canadian Electrical Code
Cu: Copper (conductor material)
DOL: Direct-On-Line (motor starting method)
FLA: Full-Load Amperes (same as FLC)
FLC: Full-Load Current
GFCI: Ground Fault Circuit Interrupter
HV: High Voltage (>35kV typically)
Hz: Hertz (frequency, 60 Hz in US/Canada, 50 Hz elsewhere)
IEC: International Electrotechnical Commission
IEEE: Institute of Electrical and Electronics Engineers
kA: Kiloampere (1000 amperes)
kcmil: Thousand circular mils (large conductor size)
kV: Kilovolt (1000 volts)
kVA: Kilovolt-ampere (apparent power)
kVAR: Kilovolt-ampere reactive (reactive power)
kW: Kilowatt (active power)
LV: Low Voltage (<1kV typically)
MV: Medium Voltage (1kV-35kV typically)
MVA: Megavolt-ampere
MVAR: Megavolt-ampere reactive
MW: Megawatt
NEC: National Electrical Code
NEMA: National Electrical Manufacturers Association
NFPA: National Fire Protection Association
OCPD: Overcurrent Protective Device
PE: Professional Engineer (licensed)
PF: Power Factor
PPE: Personal Protective Equipment
pu: Per-unit
RLS: Row Level Security
SLD: Single-Line Diagram
VFD: Variable Frequency Drive
VAR: Volt-ampere reactive
Related topics
- Electrical concepts - Power system fundamentals
- Component properties - Complete property reference
- Electrical standards - NEC and IEEE standards