def add_lv_load_area(self, lv_load_area):
        """ Adds a Load Area `lv_load_area` to _lv_load_areas if not already existing
        
        Additionally, adds the associated centre object to MV grid's _graph as node.

        Args
        ----
        lv_load_area: LVLoadAreaDing0
            instance of class LVLoadAreaDing0
        """
        if lv_load_area not in self.lv_load_areas() and isinstance(lv_load_area, LVLoadAreaDing0):
            self._lv_load_areas.append(lv_load_area)
            self.mv_grid.graph_add_node(lv_load_area.lv_load_area_centre)