Cables

Cables transport electrical power between components in your system. They represent conductors installed in conduit, cable tray, direct burial, or free air configurations.

Cable vs line distinction

In ekx:

Cables have specific physical properties:

• Conductor material (copper or aluminum)
• Conductor size (AWG or kcmil)
• Insulation type (THHN, XHHW, etc.)
• Length in meters or feet
• Installation method
• Resistance, reactance, and capacitance per km

Lines are generic connections:

• Simple connections with no physical properties
• Used for logical connections only
• Not currently supported (all connections are cables)

All connections in ekx are modeled as cables with detailed electrical parameters for accurate power flow and sizing calculations.

Cable series and variants

The cable database contains 12 series with 246 total variants:

Series groups cables by:

• Manufacturer name or product type
• Conductor material (CU or AL)
• Insulation type (PVC, XLPE, EPR)
• Voltage rating (600V, 1000V, 5kV, etc.)
• Temperature rating (60°C, 75°C, 90°C)

Variants represent individual conductor sizes within a series:

• AWG sizes: 14, 12, 10, 8, 6, 4, 2, 1, 1/0, 2/0, 3/0, 4/0
• kcmil sizes: 250, 300, 350, 400, 500, 600, 750, 1000, 1250, 1500, 2000
• Each variant has specific ampacity and electrical parameters

Example series:

Creating a cable

1. Drag the Cable icon from the component toolbar.
2. Drop on the canvas to create the cable.
3. Manually connect the cable endpoints to components, or
4. Use auto-connect by dropping near compatible components.

Cables appear as straight lines connecting two components. Cable properties appear in the edit panel when selected.

Conductor material

Select copper (CU) or aluminum (AL) based on:

Copper conductors:

• Higher ampacity per size
• Better conductivity (lower resistance)
• Standard for most building applications
• More expensive per foot
• Smaller sizes meet code requirements

Aluminum conductors:

• Lower ampacity per size (requires 2 sizes larger than copper for same current)
• Higher resistance (more voltage drop)
• Lighter weight (easier installation for large feeders)
• Less expensive per foot for large sizes
• Common for service entrance conductors and large feeders

Rule of thumb:

• Use copper for most branch circuits and small feeders
• Consider aluminum for large feeders (>400 A) where cost savings justify larger conduit

Conductor material is part of the cable series selection - choose a copper or aluminum series based on your design requirements.

Conductor size

Cable size determines current capacity (ampacity) and voltage drop:

AWG sizes (American Wire Gauge):

• Smaller numbers = larger wire (14 AWG is smaller than 10 AWG)
• Branch circuits: 14 AWG (15A), 12 AWG (20A), 10 AWG (30A)
• Feeders: 8 AWG through 4/0 AWG
• Notation: 1/0 (one aught), 2/0, 3/0, 4/0

kcmil sizes (thousands of circular mils):

• Used for very large conductors (above 4/0 AWG)
• Range: 250 kcmil through 2000 kcmil
• Service entrance conductors and large feeders
• Linear scale (500 kcmil is twice the area of 250 kcmil)

Select conductor size based on:

1. Run NEC sizing to get minimum required size
2. Check power flow results for voltage drop
3. Upsize if voltage drop exceeds 3%
4. Consider future load growth

Pending conductor suggestions

When the sizing engine finds a better conductor size, the cable can show a green pending suggestion on the canvas and in the edit panel.

This green value is a proposal. It does not change the saved cable until you accept it.

Cable suggestions may also be linked to protection-device suggestions on the same branch. If a breaker recommendation depends on a proposed cable ampacity, accepting the breaker suggestion can also accept the dependent cable suggestion.

See Auto-sizing for the full proposal and acceptance workflow.

Insulation types

Insulation determines temperature rating and application suitability:

THHN/THWN-2 (most common):

• PVC insulation with nylon jacket
• 90°C dry, 90°C wet
• General purpose building wire
• Suitable for conduit installation
• Most economical

XHHW-2:

• Cross-linked polyethylene (XLPE) insulation
• 90°C dry, 90°C wet
• Better moisture resistance than THHN
• Higher temperature rating
• Direct burial applications

TC-ER (Tray Cable):

• XLPE insulation
• 1000V rating
• Cable tray installation
• Exposed runs in industrial facilities
• All conductors in one jacket

MV-90 (Medium Voltage):

• EPR (ethylene propylene rubber) insulation
• 5kV to 35kV ratings
• Underground distribution
• Substation connections
• Shielded for safety

Choose insulation type based on installation environment, voltage level, and code requirements.

Voltage rating

Cable voltage rating must meet or exceed system voltage:

Selection rule:

• System voltage ≤ Cable voltage rating
• Example: 480V system requires ≥600V cable
• Example: 13.8kV system requires ≥15kV cable

Using higher voltage-rated cable than required is acceptable and provides safety margin.

Length input (meters/feet conversion)

Cable length affects:

• Voltage drop (longer cables = more drop)
• Cost estimation
• Conductor sizing (may need larger conductor for long runs)
• Power losses

To enter cable length:

1. Select the cable.
2. In the Properties panel, find Length field.
3. Click Meters or Feet tab to switch units.
4. Enter the length in your preferred unit.
5. The system stores length in km internally but displays in your selected unit.

Unit conversion:

• 1 meter = 3.281 feet
• 1 foot = 0.3048 meters
• 1 km = 3,281 feet

Length should represent one-way cable run from source to load. For three-phase circuits, enter the length of one conductor (not three times the length).

Installation types

Installation method affects ampacity through heat dissipation:

Common installations:

Conduit:

• Conductors pulled into metal or PVC conduit
• Most common for indoor branch circuits
• Standard ampacity per NEC 310.16

Cable tray:

• Industrial facilities
• Multiple cables laid in tray
• Single layer provides good cooling
• Multi-layer reduces ampacity significantly

Direct burial:

• Underground installation without conduit
• Good heat dissipation to soil
• Higher ampacity than conduit
• USE or direct burial rated cable required

Free air:

• Individual conductors exposed to air
• Highest ampacity (NEC 310.17)
• Limited applications (open bus, overhead spans)

Set installation type accurately for proper ampacity derating in cable sizing calculations.

Per-km electrical parameters

Cables have resistance (R), reactance (X), and capacitance (C) specified per kilometer:

Resistance (Ω/km):

• Energy loss as heat
• Depends on conductor material and size
• Smaller conductors have higher resistance
• Aluminum has ~1.6× resistance of copper
• Causes voltage drop and power losses

Reactance (Ω/km):

• Inductive impedance at 60Hz
• Depends on conductor spacing and size
• Affects voltage drop in AC circuits
• Important for power factor and reactive power

Capacitance (μF/km):

• Capacitive effect between conductors
• Negligible for short cables (<1 km)
• Important for long transmission lines
• Affects reactive power generation

These parameters are built into the cable database and update automatically when you select a cable series and size. You rarely need to modify them directly.

Cable ampacity at 90°C rating

Each cable variant has ampacity ratings at three temperatures:

60°C rating:

• Old code requirement (pre-1970s)
• Conservative but rarely used today
• Some equipment still requires 60°C termination

75°C rating:

• Most common termination rating
• Used for most breakers and equipment
• Standard for NEC calculations unless specified otherwise

90°C rating:

• Maximum conductor temperature
• Modern insulation types (THHN, XHHW)
• Can use 90°C ampacity with derating, but must verify termination rating
• Allows smaller conductor sizes

Important: Even if cable is 90°C rated, terminations are often 75°C. Use 75°C ampacity unless equipment is specifically rated for 90°C.

The cable database includes all three ratings. Sizing calculations use the appropriate rating based on termination temperature defaults.

Parallel runs

For very high current circuits, install multiple conductors per phase:

1. Select the cable.
2. In Properties panel, set Parallel Runs (e.g., 2 for two conductors per phase).
3. Sizing calculations divide total current by number of runs.
4. Each conductor carries: Total Current ÷ Parallel Runs

Example:

1200 A feeder with 3 parallel conductors:

• Current per conductor: 1200 A ÷ 3 = 400 A
• Size each conductor for 400 A (after derating)
• Total cable capacity: 3 × conductor ampacity

NEC 310.4 requirements for parallel conductors:

• Conductors must be 1/0 AWG or larger (copper)
• Same length
• Same material and size
• Same insulation type
• Same termination

Parallel runs reduce conductor size and conduit requirements for high-amperage circuits.

Common cable configurations

Branch circuit:

• 14 AWG (15A) or 12 AWG (20A) copper THHN
• Length: <100 ft typically
• Installation: Conduit
• Voltage: 120V or 208V

Feeder:

• 4 AWG through 500 kcmil copper/aluminum THHN or XHHW
• Length: 50-500 ft
• Installation: Conduit or cable tray
• Voltage: 208V, 480V, 600V

Service entrance:

• 250-1000 kcmil aluminum USE or XHHW
• Parallel runs common for >600A
• Length: Utility connection to main switchboard
• Installation: Underground direct burial or conduit

Medium voltage distribution:

• 1/0 through 500 kcmil copper MV-90 or MV-105
• Length: 100-2000 ft
• Installation: Underground duct bank
• Voltage: 4.16kV, 13.8kV

Selecting from the cable database

To choose a cable:

1. Select the cable on the canvas.
2. In Properties panel, click Cable Series dropdown.
3. The dropdown shows: Series Name | Material | Voltage | Insulation
4. Select the appropriate series for your application.
5. Click Conductor Size dropdown.
6. Select size based on ampacity requirements from sizing calculations.

The system auto-populates resistance, reactance, and ampacity from the database.

Related topics

• Cable sizing - NEC ampacity calculations
• Power flow analysis - Voltage drop verification
• Connections - Connecting cables between components
• Component defaults - Setting default cable series