diff --git a/config/config.default.yaml b/config/config.default.yaml
index b16f25f8..b37aaac0 100644
--- a/config/config.default.yaml
+++ b/config/config.default.yaml
@@ -255,7 +255,7 @@ lines:
     750.: "Al/St 560/50 4-bundle 750.0"
   s_max_pu: 0.7
   s_nom_max: .inf
-  max_extension: .inf
+  max_extension: 20000 #MW
   length_factor: 1.25
   reconnect_crimea: true
   under_construction: 'zero' # 'zero': set capacity to zero, 'remove': remove, 'keep': with full capacity
@@ -270,7 +270,7 @@ lines:
 links:
   p_max_pu: 1.0
   p_nom_max: .inf
-  max_extension: .inf
+  max_extension: 30000 #MW
   include_tyndp: true
   under_construction: 'zero' # 'zero': set capacity to zero, 'remove': remove, 'keep': with full capacity