remove cable dist. from MV grid when disconnected

openego/eDisGo#48

ding0/core/network/grids.py

@@ -132,6 +132,15 @@ def add_cable_distributor(self, cable_dist):
             self._cable_distributors.append(cable_dist)
             self.graph_add_node(cable_dist)
 
+    def remove_cable_distributor(self, cable_dist):
+        """Removes a cable distributor from _cable_distributors if existing"""
+        if cable_dist in self.cable_distributors() and isinstance(cable_dist,
+                                                                  MVCableDistributorDing0):
+            # remove from array and graph
+            self._cable_distributors.remove(cable_dist)
+            if self._graph.has_node(cable_dist):
+                self._graph.remove_node(cable_dist)
+
     def add_ring(self, ring):
         """Adds a ring to _rings if not already existing"""
         if ring not in self._rings and isinstance(ring, RingDing0):

ding0/grid/mv_grid/mv_connect.py

@@ -518,7 +518,7 @@ def disconnect_node(node, target_obj_result, graph, debug):
         neighbor_nodes = graph.neighbors(target_obj_result)
 
         if len(neighbor_nodes) == 2:
-            graph.remove_node(target_obj_result)
+            node.grid.remove_cable_distributor(target_obj_result)
 
             branch_length = calc_geo_dist_vincenty(neighbor_nodes[0], neighbor_nodes[1])
             graph.add_edge(neighbor_nodes[0], neighbor_nodes[1], branch=BranchDing0(length=branch_length,