thermal_cable_model.cable — Cable Definitions

Cable construction definitions for LV and MV applications.

Cables are described by concentric cylindrical layers from conductor outward. Factory class-methods provide common cable constructions; users can also build custom cables layer-by-layer.

class CableLayer

Bases: object

Single concentric cylindrical layer.

Parameters:

• material (ThermalMaterial)

• inner_radius (float [m])

• outer_radius (float [m])

material: ThermalMaterial

inner_radius: float

outer_radius: float

property thickness: float

property thermal_resistance_per_length: float

Radial thermal resistance per unit length [K·m/W].

property thermal_capacitance_per_length: float

Thermal capacitance per unit length [J/(m·K)].

__init__(material, inner_radius, outer_radius)

Parameters:

• material (ThermalMaterial)

• inner_radius (float)

• outer_radius (float)

Return type:

None

class Cable

Bases: object

Complete cable construction.

Parameters:

• name (str) – Descriptive identifier.

• voltage_class (str) – "LV" or "MV".

• n_conductors (int) – Number of power conductors (1 for single-core, 3 for three-core).

• conductor_area (float) – Cross-sectional area of one conductor [m²].

• conductor_material (ThermalMaterial)

• layers (list[CableLayer]) – Ordered list from innermost insulation outward (excluding the conductor itself).

• ac_resistance_20c (float) – AC resistance at 20 °C per unit length [Ω/m].

• temp_coeff_resistance (float) – Temperature coefficient of resistance [1/K] (≈ 3.93e-3 for Cu, 4.03e-3 for Al).

• max_conductor_temp (float) – Maximum continuous conductor temperature [°C].

• loss_factor_sheath (float) – λ₁ — ratio of sheath/screen losses to conductor losses.

• loss_factor_armour (float) – λ₂ — ratio of armour losses to conductor losses.

• dielectric_loss (float) – W_d — dielectric loss per phase per unit length [W/m].

name: str

voltage_class: str

n_conductors: int

conductor_area: float

conductor_material: ThermalMaterial

layers: list[CableLayer]

ac_resistance_20c: float = 0.0

temp_coeff_resistance: float = 0.00393

max_conductor_temp: float = 90.0

loss_factor_sheath: float = 0.0

loss_factor_armour: float = 0.0

dielectric_loss: float = 0.0

property conductor_radius: float

Equivalent solid conductor radius [m].

property outer_radius: float

property outer_diameter: float

ac_resistance(temperature)

Temperature-corrected AC resistance [Ω/m].

Parameters:

temperature (float)

Return type:

float

conductor_loss(current, temperature)

Joule loss per conductor per unit length W_c [W/m].

Parameters:

• current (float)

• temperature (float)

Return type:

float

total_heat_per_length(current, temperature)

Total heat generation per cable per unit length [W/m].

Includes conductor, sheath, armour, and dielectric losses.

Parameters:

• current (float)

• temperature (float)

Return type:

float

property conductor_capacitance_per_length: float

Thermal capacitance of the conductor [J/(m·K)].

classmethod single_core_xlpe_cu(conductor_area_mm2, voltage_class='MV', voltage_kv=20.0)

Single-core copper XLPE cable (typical MV distribution cable).

Approximate geometry generated from the conductor area; for exact modelling supply layer dimensions directly.

Parameters:

• conductor_area_mm2 (float)

• voltage_class (str)

• voltage_kv (float)

Return type:

Cable

classmethod single_core_xlpe_al(conductor_area_mm2, voltage_class='MV', voltage_kv=20.0)

Single-core aluminium XLPE cable.

Parameters:

• conductor_area_mm2 (float)

• voltage_class (str)

• voltage_kv (float)

Return type:

Cable

classmethod three_core_xlpe_cu(conductor_area_mm2, voltage_class='LV', voltage_kv=0.6)

Three-core copper XLPE cable (typical LV distribution cable).

Parameters:

• conductor_area_mm2 (float)

• voltage_class (str)

• voltage_kv (float)

Return type:

Cable

classmethod three_core_pvc_cu(conductor_area_mm2, voltage_class='LV', voltage_kv=0.6)

Three-core copper PVC cable (LV).

Parameters:

• conductor_area_mm2 (float)

• voltage_class (str)

• voltage_kv (float)

Return type:

Cable

__init__(name, voltage_class, n_conductors, conductor_area, conductor_material, layers=<factory>, ac_resistance_20c=0.0, temp_coeff_resistance=0.00393, max_conductor_temp=90.0, loss_factor_sheath=0.0, loss_factor_armour=0.0, dielectric_loss=0.0)

Parameters:

• name (str)

• voltage_class (str)

• n_conductors (int)

• conductor_area (float)

• conductor_material (ThermalMaterial)

• layers (list[CableLayer])

• ac_resistance_20c (float)

• temp_coeff_resistance (float)

• max_conductor_temp (float)

• loss_factor_sheath (float)

• loss_factor_armour (float)

• dielectric_loss (float)

Return type:

None

iec_line_capacitance_per_length(relative_permittivity, diameter_over_inner_screen_mm, diameter_over_insulation_mm)

Line capacitance [F/m], IEC 60287-1-1 §2.2 (form used in CIGRE TB880).

C = (ε_r / (18·ln(D_i / d_c)))·10⁻⁹ with both diameters in millimetres.

Parameters:

• relative_permittivity (float)

• diameter_over_inner_screen_mm (float)

• diameter_over_insulation_mm (float)

Return type:

float

dielectric_loss_per_length(capacitance_f_per_m, voltage_kv_phase_to_phase, tan_delta, frequency_hz=50.0)

Dielectric loss per unit length [W/m]: ω C U₀² tan δ.

U₀ is RMS phase voltage [V] from line voltage U/√3.

Parameters:

• capacitance_f_per_m (float)

• voltage_kv_phase_to_phase (float)

• tan_delta (float)

• frequency_hz (float)

Return type:

float