Isolated nodes in the PyPSA graph

[gplssm]

Some grid districts (197, 1066, ...) have isolated node in the PyPSA graph thus multiple islanded grids result of this. Find the reason for some node not being connected to the remaining part of the grid and fix it. The isolated nodes are mostly buses of BranchTee()'s.

[gplssm]

This is an issue related to import_from_ding0() it 😏

With [_.node for _ in connected_component_subgraphs(network.mv_grid.graph)] you can see 4 subgraphs exist.

0 = {dict} {Generator_717: {'type': 'generator'}, LVStation_176765: {'type': 'lv_station'}, LVStation_176770: {'type': 'lv_station'}, Generator_720: {'type': 'generator'}, BranchTee_MVGrid_1066_2: {'type': 'branch_tee'}, LVStation_176709: {'type': 'lv_station'}, LVSt
1 = {dict} {BranchTee_MVGrid_1066_5: {'type': 'branch_tee'}}
2 = {dict} {MVDisconnectingPoint_1: {'type': 'disconnection_point'}}
3 = {dict} {MVDisconnectingPoint_2: {'type': 'disconnection_point'}}

We don't have to worry about the last two, but about the second. Somehow there appear unconnected BranchTee's

[gplssm]

Hmm, maybe it's not a problem of the importer. We can see there are cable distributors included in Ding0's MV cable distributors list without being part of the MV graph. Therefore, put a break point in _build_mv_grid() and ask for

set(ding0_grid._cable_distributors) - set(ding0_grid._graph.nodes())

It will show mv_cable_dist_5 is not a node of the graph. Neither an isolated one.

@nesnoj do you have idea why the mv_cable_dist_5 is in the list but not in the graph?

A quick, dirty fix would be possible in eDisGo being asking if the node is part of the Ding0 graph, but I would prefer to solve it in Ding0 itself.

[nesnoj]

Thanks for discovering!

Fixed in openego/ding0@1bb0530 .
Reason: When CDs are disconnected from graph (procedure: connect -> check if branch constraints are violated -> if yes, disconnect), they were removed from graph but not from CD list in MV grid.

Please close if ok @gplssm

PS: I used

for cd in nd._mv_grid_districts[0].mv_grid._cable_distributors:
    if not nd._mv_grid_districts[0].mv_grid._graph.has_node(cd):
        print(repr(cd), 'is no member of graph')

to check if all CDs in MV grid list are member of the MV graph..

[gplssm]

🍻 man!