diff --git a/rules/build_electricity.smk b/rules/build_electricity.smk
index be97270a..10d253f2 100755
--- a/rules/build_electricity.smk
+++ b/rules/build_electricity.smk
@@ -386,6 +386,7 @@ rule build_transmission_projects:
     params:
         transmission_projects=config_provider("transmission_projects"),
         line_factor=config_provider("lines", "length_factor"),
+        s_max_pu=config_provider("lines", "s_max_pu"),
     input:
         base_network=resources("networks/base.nc"),
         offshore_shapes=resources("offshore_shapes.geojson"),
diff --git a/scripts/build_transmission_projects.py b/scripts/build_transmission_projects.py
index ba185d17..8dbc044b 100644
--- a/scripts/build_transmission_projects.py
+++ b/scripts/build_transmission_projects.py
@@ -482,6 +482,7 @@ if __name__ == "__main__":
     set_scenario_config(snakemake)
 
     line_factor = snakemake.params.line_factor
+    s_max_pu = snakemake.params.s_max_pu
 
     n = pypsa.Network(snakemake.input.base_network)
 
@@ -543,6 +544,8 @@ if __name__ == "__main__":
             * new_lines_df["v_nom"]
             * new_lines_df["num_parallel"]
         ).round(2)
+        # set s_max_pu
+        new_lines_df["s_max_pu"] = s_max_pu
     if not new_links_df.empty:
         # Add carrier types of lines and links
         new_links_df["carrier"] = "DC"