from math import pi, sqrt
import pytest
from prereise.gather.griddata.transmission.const import kilometers_per_mile as km_per_mi
from prereise.gather.griddata.transmission.geometry import (
Conductor,
ConductorBundle,
Line,
PhaseLocations,
Tower,
)
# Conversion factor for tower spacing in feet to tower spacing in meters
m_in_ft = 304.8e-3
[docs]def test_conductor_by_parameter_values():
# 'Cardinal' conductor
outer_diameter = 0.03038
strand_radius = 1.688e-3
rated_dc_resistance_per_1000_ft = 0.0179
rated_dc_resistance_per_km = rated_dc_resistance_per_1000_ft * 3.2808
# Calculate for solid-aluminum (resistance should be lower than rated)
conductor = Conductor(radius=(outer_diameter / 2), material="aluminum")
assert conductor.resistance_per_km < rated_dc_resistance_per_km
# Count 54 aluminum strands only for conductance purposes, ignore 7 steel strands
# (resistance should be approximately equal to rated)
area = 54 * pi * strand_radius**2
conductor = Conductor(
radius=(outer_diameter / 2),
area=area,
material="aluminum",
current_limit=1015,
)
assert conductor.resistance_per_km == pytest.approx(rated_dc_resistance_per_km, 0.1)
[docs]def test_conductor_by_name():
conductor = Conductor("cardinal")
assert conductor.resistance_per_km == 0.0709
assert conductor.radius == pytest.approx(0.01519)
assert conductor.name == "Cardinal"
[docs]def test_conductor_name_and_parameters():
with pytest.raises(TypeError):
Conductor("Cardinal", resistance_per_km=0.1)
[docs]def test_conductor_bundle():
spacing = 0.4572
conductor = Conductor("Cardinal") # standard ACSR conductor
for n in (2, 3):
bundle = ConductorBundle(n=n, spacing=spacing, conductor=conductor)
assert bundle.resistance_per_km == conductor.resistance_per_km / n
assert bundle.spacing_L == (conductor.gmr * spacing ** (n - 1)) ** (1 / n)
assert bundle.spacing_C == (conductor.radius * spacing ** (n - 1)) ** (1 / n)
[docs]def test_tower_single_circuit():
# Tower has two-conductor bundles (1.5 ft spacing), 24 ft b/w phases, 90 ft height
spacing = 1.5 * m_in_ft
locations = PhaseLocations(
a=(-24 * m_in_ft, 90 * m_in_ft),
b=(0, 90 * m_in_ft),
c=(24 * m_in_ft, 90 * m_in_ft),
)
# Instantiate objects
conductor = Conductor("Cardinal") # standard ACSR conductor
bundle = ConductorBundle(n=2, spacing=spacing, conductor=conductor)
tower = Tower(locations=locations, bundle=bundle)
# Calculate for 50-mile distances (test case)
resistance_per_50_mi = tower.resistance * 50 * km_per_mi
series_reactance_per_50_mi = 2 * pi * 60 * tower.inductance * 50 * km_per_mi
shunt_admittance_per_50_mi = 2 * pi * 60 * tower.capacitance * 50 * km_per_mi
# Expected values
expected_resistance = 2.82 # Ohms
expected_series_reactance = 29.2 # Ohms
expected_shunt_admittance = 3.59e-4 # Siemens
# Check
# relative tolerance of 5% to account for unknown temperature for resistivity
assert resistance_per_50_mi == pytest.approx(expected_resistance, rel=0.05)
# Reactance & admittance values match within 1%, since they're purely gemetric
assert series_reactance_per_50_mi == pytest.approx(
expected_series_reactance, rel=0.01
)
assert shunt_admittance_per_50_mi == pytest.approx(
expected_shunt_admittance, rel=0.01
)
line = Line(tower=tower, length=(50 * km_per_mi), voltage=345)
assert line.power_rating == pytest.approx(1207, rel=0.01)
[docs]def test_tower_double_circuit():
locations = PhaseLocations(
circuits=2,
a=((-9 * m_in_ft, 120 * m_in_ft), (9 * m_in_ft, 100 * m_in_ft)),
b=((-10.5 * m_in_ft, 110 * m_in_ft), (10.5 * m_in_ft, 110 * m_in_ft)),
c=((-9 * m_in_ft, 100 * m_in_ft), (9 * m_in_ft, 120 * m_in_ft)),
)
# Instantiate objects
conductor = Conductor("Ostrich") # standard ACSR conductor
bundle = ConductorBundle(n=1, conductor=conductor)
tower = Tower(locations=locations, bundle=bundle)
# Calculate per-mile values (test case)
series_reactance_per_mi = 2 * pi * 60 * tower.inductance * km_per_mi
shunt_admittance_per_mi = 2 * pi * 60 * tower.capacitance * km_per_mi
# Expected values
expected_series_reactance = 0.372 # Ohms
expected_shunt_admittance = 11.41e-6 # Siemens
# Check
assert series_reactance_per_mi == pytest.approx(expected_series_reactance, rel=0.01)
assert shunt_admittance_per_mi == pytest.approx(expected_shunt_admittance, rel=0.01)
[docs]def test_line_long():
conductor = Conductor("Rook") # standard ACSR conductor
conductor.resistance_per_km = 0.09963 # rated value at 50 C
locations = PhaseLocations(a=(-7.25, 50), b=(0, 50), c=(7.25, 50))
bundle = ConductorBundle(n=1, conductor=conductor)
tower = Tower(locations=locations, bundle=bundle)
line = Line(tower=tower, length=370, voltage=215)
# The following values are appreciably different than what we would see using a
# short-line model that just multiplies per-length by total length
assert line.series_impedance.imag == pytest.approx(183.6619, rel=0.005)
assert line.series_impedance.real == pytest.approx(34.20553, rel=0.005)
assert line.shunt_admittance == pytest.approx(0.001198j, rel=0.005)
assert line.surge_impedance_loading == pytest.approx(215**2 / 406.4, rel=0.005)
assert line.thermal_rating == pytest.approx(215 * 795 * sqrt(3) / 1e3)
assert line.power_rating == pytest.approx(1.14534 * 113.742, rel=0.005)
[docs]def test_line_short():
short_line_length = 10 # km
omega = 60 * 2 * pi
conductor = Conductor("Rook")
locations = PhaseLocations(a=(-7.25, 50), b=(0, 50), c=(7.25, 50))
bundle = ConductorBundle(n=1, conductor=conductor)
tower = Tower(locations=locations, bundle=bundle)
line = Line(tower=tower, length=10, voltage=215)
assert line.power_rating == line.thermal_rating
assert line.series_impedance.imag == pytest.approx(
line.tower.inductance * omega * short_line_length,
rel=1e-4,
)
assert line.series_impedance.real == pytest.approx(
line.tower.resistance * short_line_length,
rel=1e-4,
)
assert line.shunt_admittance.imag == pytest.approx(
short_line_length * line.tower.capacitance * omega, rel=1e-4
)
