Environment

The Environment class captures weather and geographic conditions that affect conductor heat balance, sag, and corona calculations.

Fields

Field	Type	Default	Description
`date`	`date`	today	Reference date (affects solar angle and heat gain)
`latitude`	`float`	—	Geographic latitude in degrees (–90° to 90°)
`elevation_m`	`float`	—	Site elevation above sea level (m)
`wind_speed_m_per_s`	`float`	—	Wind speed (m/s)
`wind_angle`	`int`	—	Angle between wind and conductor axis (0–90°)
`cw_angle_direction_rel_to_north`	`int`	—	Conductor orientation relative to north (0–90°)
`hour`	`int`	—	Hour of day for solar calculations (0–24)
`atmosphere`	`dict`	—	Polynomial coefficients (A–G) for solar heat flux
`ambient_temperature_c`	`float`	—	Ambient air temperature (°C)
`weather_correction_factor`	`float`	`1.0`	Set to `0.8` for rainy conditions
`rugosity_coefficient`	`float`	`0.82`	Conductor surface roughness: `1.0` polished, `0.92–0.98` dirty, `0.80–0.87` stranded

Default Environments

Two pre-configured environments are provided.

Clear skyIndustrial atmosphere

from refa.defaults import default_clear_environment

env = default_clear_environment()
# latitude=45°N, elevation=100 m, wind=1 m/s, ambient=25°C, hour=12

from refa.defaults import default_industrial_environment

env = default_industrial_environment()
# Same geometry, but with industrial pollution atmosphere coefficients

Custom Environment

import datetime
from refa import Environment
from refa.defaults import default_clear_environment

# Start from the default and modify
env = default_clear_environment()
env.date = datetime.date(2025, 7, 15)
env.ambient_temperature_c = 35.0
env.wind_speed_m_per_s = 0.6       # Low wind — conservative rating
env.weather_correction_factor = 0.8  # Rainy conditions

Or construct from scratch:

env = Environment(
    date=datetime.date(2025, 7, 15),
    latitude=34.0,
    elevation_m=200.0,
    wind_speed_m_per_s=0.6,
    wind_angle=45,
    cw_angle_direction_rel_to_north=0,
    hour=14,
    atmosphere={"A": -42.2391, "B": 63.8044, "C": -1.922,
                "D": 0.0346921, "E": -0.000361118,
                "F": 1.94318e-06, "G": -4.07608e-09},
    ambient_temperature_c=35.0,
)

Atmosphere coefficients

The atmosphere dict contains the A–G polynomial coefficients for the Leckner solar heat flux model used in IEEE 738. Use default_clear_environment() or default_industrial_environment() as starting points, or consult the IEEE 738 standard for site-specific values.

Effect on Calculations

The Environment directly drives the IEEE 738 thermal balance equation inside Line. Changing the date, hour, latitude, or wind speed will change:

Ampacity (ampacity_at_environment())
Steady-state conductor temperature
All sag calculations that depend on computed conductor temperature
Losses calculations that depend on computed conductor resistance
Congestion (which depends on available ampacity)

EnvironmentImperial

In case of imperial unit system, the user can use the same constructor Environment, which will accept values in imperial units. These are converted to metric system with which all internal calculations are conducted.