Merge pull request #49 from statnett/fix-conductor-temperature-computation

Update thermal_model.py

Author: genisott

linerate/models/thermal_model.py

@@ -245,6 +245,8 @@ def compute_conductor_temperature(
         ----------
         current:
             :math:`I_\text{max}~\left[\text{A}\right]`. The current flowing through the conductor.
+            NOTE that the current is the total current for all conductors in the span. When
+            computing the temperature, the current is divided by the number of conductors.
         min_temperature:
             :math:`T_\text{min}~\left[^\circ\text{C}\right]`. Lower bound for the numerical scheme
             for computing the temperature
@@ -262,12 +264,12 @@ def compute_conductor_temperature(
         Union[float, float64, ndarray[Any, dtype[float64]]]
             :math:`I~\left[\text{A}\right]`. The thermal rating.
         """
+        n = self.span.num_conductors
         T = solver.compute_conductor_temperature(
             self.compute_heat_balance,
-            current=current,
+            current=current / n,
             min_temperature=min_temperature,
             max_temperature=max_temperature,
             tolerance=tolerance,
         )
-        n = self.span.num_conductors
-        return T / n
+        return T

tests/acceptance_tests/test_cigre_ampacity_cases.py

@@ -7,72 +7,27 @@
 import linerate
 
 
-@pytest.fixture
-def drake_conductor_a():
-    return linerate.Conductor(
-        core_diameter=10.4e-3,
-        conductor_diameter=28.1e-3,
-        outer_layer_strand_diameter=4.4e-3,
-        emissivity=0.8,
-        solar_absorptivity=0.8,
-        temperature1=25,
-        temperature2=75,
-        resistance_at_temperature2=8.688e-5,
-        resistance_at_temperature1=7.283e-5,
-        aluminium_cross_section_area=float("nan"),
-        constant_magnetic_effect=1,
-        current_density_proportional_magnetic_effect=0,
-        max_magnetic_core_relative_resistance_increase=1,
-    )
-
-
-@pytest.fixture
-def example_weather_a():
-    return linerate.Weather(
-        air_temperature=40,
-        wind_direction=np.radians(30),  # Conductor azimuth is 90, so 90 - 30 is 30
-        wind_speed=0.61,
-        clearness_ratio=1,
-    )
-
-
-@pytest.fixture
-def example_span_a(drake_conductor_a):
-    start_tower = linerate.Tower(latitude=30, longitude=0.0001, altitude=0)
-    end_tower = linerate.Tower(latitude=30, longitude=-0.0001, altitude=0)
-    return linerate.Span(
-        conductor=drake_conductor_a,
-        start_tower=start_tower,
-        end_tower=end_tower,
-        ground_albedo=0.1,
-        num_conductors=1,
-    )
-
-
-@pytest.fixture
-def example_model_a(example_span_a, example_weather_a):
-    return linerate.Cigre601(example_span_a, example_weather_a, np.datetime64("2016-06-10 11:00"))
-
+def test_example_a_convective_cooling(example_model_1_conductors):
+    assert example_model_1_conductors.compute_convective_cooling(100, None) == approx(77.6, abs=0.5)
 
-def test_example_a_convective_cooling(example_model_a):
-    assert example_model_a.compute_convective_cooling(100, None) == approx(77.6, abs=0.5)
 
+def test_example_a_radiative_cooling(example_model_1_conductors):
+    assert example_model_1_conductors.compute_radiative_cooling(100, None) == approx(39.1, abs=0.5)
 
-def test_example_a_radiative_cooling(example_model_a):
-    assert example_model_a.compute_radiative_cooling(100, None) == approx(39.1, abs=0.5)
 
+def test_example_a_solar_heating(example_model_1_conductors):
+    assert example_model_1_conductors.compute_solar_heating(100, None) == approx(27.2, abs=0.5)
 
-def test_example_a_solar_heating(example_model_a):
-    assert example_model_a.compute_solar_heating(100, None) == approx(27.2, abs=0.5)
 
-
-def test_example_a_resistance(example_model_a):
-    assert example_model_a.compute_resistance(100, None) == approx(9.3905e-5, abs=0.0001e-5)
+def test_example_a_resistance(example_model_1_conductors):
+    assert example_model_1_conductors.compute_resistance(100, None) == approx(
+        9.3905e-5, abs=0.0001e-5
+    )
 
 
-def test_example_a_ampacity(example_model_a):
+def test_example_a_ampacity(example_model_1_conductors):
     # There are noticable roundoff errors in the report
-    assert example_model_a.compute_steady_state_ampacity(100, tolerance=1e-8) == approx(
+    assert example_model_1_conductors.compute_steady_state_ampacity(100, tolerance=1e-8) == approx(
         976, abs=1.5
     )
 

tests/conftest.py

@@ -1,6 +1,9 @@
 import hypothesis
+import numpy as np
 import pytest
 
+import linerate
+
 hypothesis.settings.register_profile("default", deadline=None)
 hypothesis.settings.load_profile("default")
 
@@ -15,3 +18,72 @@ def rng(random_seed):
     import numpy as np
 
     return np.random.default_rng(random_seed)
+
+
+@pytest.fixture
+def drake_conductor_a():
+    return linerate.Conductor(
+        core_diameter=10.4e-3,
+        conductor_diameter=28.1e-3,
+        outer_layer_strand_diameter=4.4e-3,
+        emissivity=0.8,
+        solar_absorptivity=0.8,
+        temperature1=25,
+        temperature2=75,
+        resistance_at_temperature2=8.688e-5,
+        resistance_at_temperature1=7.283e-5,
+        aluminium_cross_section_area=float("nan"),
+        constant_magnetic_effect=1,
+        current_density_proportional_magnetic_effect=0,
+        max_magnetic_core_relative_resistance_increase=1,
+    )
+
+
+@pytest.fixture
+def example_weather_a():
+    return linerate.Weather(
+        air_temperature=40,
+        wind_direction=np.radians(30),  # Conductor azimuth is 90, so 90 - 30 is 30
+        wind_speed=0.61,
+        clearness_ratio=1,
+    )
+
+
+@pytest.fixture
+def example_span_1_conductor(drake_conductor_a):
+    start_tower = linerate.Tower(latitude=30, longitude=0.0001, altitude=0)
+    end_tower = linerate.Tower(latitude=30, longitude=-0.0001, altitude=0)
+    return linerate.Span(
+        conductor=drake_conductor_a,
+        start_tower=start_tower,
+        end_tower=end_tower,
+        ground_albedo=0.1,
+        num_conductors=1,
+    )
+
+
+@pytest.fixture
+def example_span_2_conductors(drake_conductor_a):
+    start_tower = linerate.Tower(latitude=30, longitude=0.0001, altitude=0)
+    end_tower = linerate.Tower(latitude=30, longitude=-0.0001, altitude=0)
+    return linerate.Span(
+        conductor=drake_conductor_a,
+        start_tower=start_tower,
+        end_tower=end_tower,
+        ground_albedo=0.1,
+        num_conductors=2,
+    )
+
+
+@pytest.fixture
+def example_model_1_conductors(example_span_1_conductor, example_weather_a):
+    return linerate.Cigre601(
+        example_span_1_conductor, example_weather_a, np.datetime64("2016-06-10 11:00")
+    )
+
+
+@pytest.fixture
+def example_model_2_conductors(example_span_2_conductors, example_weather_a):
+    return linerate.Cigre601(
+        example_span_2_conductors, example_weather_a, np.datetime64("2016-06-10 11:00")
+    )

tests/models/test_thermal_model.py

@@ -0,0 +1,12 @@
+"""Test cases from Annex E of CIGRE TB 601."""
+
+
+def test_compute_conductor_temperature(example_model_1_conductors, example_model_2_conductors):
+    # Check that the ampacity of a span with two conductors is divided
+    # when computing the conductor temperature.
+    current_1_conductor = 1000
+    current_2_conductors = current_1_conductor * 2
+    # The temperature should stay the same
+    assert example_model_1_conductors.compute_conductor_temperature(
+        current_1_conductor
+    ) == example_model_2_conductors.compute_conductor_temperature(current_2_conductors)

tests/test_solver.py

@@ -16,7 +16,7 @@ def heat_balance(conductor_temperature, current):
     assert conductor_temperature == pytest.approx(15, rel=1e-7)
 
 
-def test_compute_conductor_temperature_computes_correct_ampacity():
+def test_compute_conductor_ampacity_computes_correct_ampacity():
     def heat_balance(conductor_temperature, current):
         A = current
         T = conductor_temperature