Quick start

This section presents a basic steady-state thermal-rating calculation using both the IEEE 738 and CIGRE TB 601 methods implemented in PyPacity.

Thermal rating: \(I_{CDR}=f(T_{CDR})\)

The objective is to calculate the steady-state conductor current for a specified steady-state conductor temperature. The thermal equilibrium is expressed as

\[q_c + q_r = q_s + I^2 R(T_{avg}),\]

where \(q_c\) is the convective heat loss, \(q_r\) is the radiative heat loss, \(q_s\) is the solar heat gain, and \(R(T_{avg})\) is the conductor resistance evaluated at its average temperature.

Example

The following example selects a DRAKE conductor, defines the ambient and operating conditions, and computes its thermal rating according to IEEE 738 and CIGRE TB 601.

from pypacity.cable import cable
from pypacity.case import case
from pypacity.ieee738 import ieee738
from pypacity.cigre601 import cigre601
from pypacity.utils import solar

import matplotlib.pyplot as plt
from datetime import datetime

print("*******************************************************************")
print("*******************************************************************")
print("CIGRE TB 601 - Thermal rating of power cables")
print("Example A: Page 79")
print("*******************************************************************")

NSELECT = 2
Cable1 = cable.Cable()
c_db, error = Cable1.load_cable_db()
Cable1.set_cable( NSELECT, conductor = 'DRAKE')
Cable1.EMISS = 0.8
Cable1.ABSORP = 0.8

# Case 1
dt1 = datetime(2026, 6, 10, 11, 00)
print("Date and time: " + str(dt1))
SG1 = solar.SolarGeometry()
Case1 = case.Case()
Case1.demo( NSELECT)
# Ambient conditions
Case1.TAMB = 40.0
Case1.CDR_LAT_DEG = 30
Case1.ALBEDO = 0.1
Case1.beta = 0
Case1.CDR_ELEV = 0
Case1.TCDRPRELOAD = 100
Case1.VWIND = 0.61
Case1.DWIND_DEG = 60
Case1.Z1_DEG = 0
Case1.SOLAR = 1
Case1.Ns = 1.0
Case1.SUN_TIME = round(SG1.DatetimetoSolarHour(dt1),3)
print("SUN_TIME: " + str(Case1.SUN_TIME)) # SUN_TIME > 24 => Measurement available.
Case1.NDAY = SG1.DatetimetoDayOfYear(dt1)
print("NDAY: " + str(Case1.NDAY))

Case1TB601 = cigre601.CIGRE601()
Case1TB601.Debug = 0
Case1TB601.set_cable( Cable1)
Case1TB601.set_case( Case1)
Case1TB601.cigre601()
Case1TB601.output()

Case1IEEE738 = ieee738.IEEE738()
Case1IEEE738.Debug = 0
Case1IEEE738.set_cable( Cable1)
Case1IEEE738.set_case( Case1)
Case1IEEE738.ieee_738_2013()
Case1IEEE738.output()

print(" ")
print(" ")
print("*******************************************************************")
print("*******************************************************************")
print("CIGRE TB 601 - Thermal rating of power cables")
print("Example B: Page 79")
print("*******************************************************************")

NSELECT = 2
Cable2 = cable.Cable()
c_db, error = Cable1.load_cable_db()
Cable2.set_cable( NSELECT, conductor = 'DRAKE')
Cable2.EMISS = 0.9
Cable2.ABSORP = 0.9

# Case 1
dt2 = datetime(2026, 10, 3, 14, 00)
print("Date and time: " + str(dt2))
SG2 = solar.SolarGeometry()
Case2 = case.Case()
Case2.demo( NSELECT)
# Ambient conditions
Case2.TAMB = 20.0
Case2.CDR_LAT_DEG = 50
Case2.ALBEDO = 0.15
Case2.beta = 10
Case2.CDR_ELEV = 500
Case2.TCDRPRELOAD = 100
Case2.VWIND = 1.66
Case2.DWIND_DEG = 80
Case2.Z1_DEG = 0
Case2.SOLAR = 1
Case2.Ns = 0.5
Case2.SUN_TIME = round(SG2.DatetimetoSolarHour(dt2),3)
print("SUN_TIME: " + str(Case2.SUN_TIME))
Case2.NDAY = SG2.DatetimetoDayOfYear(dt2)
print("NDAY: " + str(Case2.NDAY))

Case2TB601 = cigre601.CIGRE601()
Case2TB601.Debug = 0
Case2TB601.set_cable( Cable2)
Case2TB601.set_case( Case2)
Case2TB601.cigre601()
Case2TB601.output()

Case2IEEE738 = ieee738.IEEE738()
Case2IEEE738.Debug = 0
Case2IEEE738.set_cable( Cable2)
Case2IEEE738.set_case( Case2)
Case2IEEE738.ieee_738_2013()
Case2IEEE738.output()