11kV/400V TX with no LV protection

Yes, but if it is that sort of scheme there will be signalling between sets of breakers, some more remote and the local ones to ensure the correct intertripping sequence-
And then it can get get very complex as those who know far more than me about the HV side mutter darkly about the merits of staggered thresholds for permissive versus direct tripping (*),  And then, at least in the UK , there will be some catch-all that still disconnects eventually even if the inter-trip telemetry fails

In any case, all of this will come out in the wash of inquiring about the primary side protection. If you get an answer you do not understand and there is no clarification forthcoming, then come back and we will see what we can do to help de-mystify it.

Mike.

PS (It is an aside but a permissive intertrip is a sort of voting system where the trip only fires if there is both a  command to trip from the other end of the line and also a local overload at some level,  Direct intertrip is easier to understand but less flexible - if the remote command comes in to trip, then it will always trip - even if the fault is somewhere else)

Yes, but if it is that sort of scheme there will be signalling between sets of breakers, some more remote and the local ones to ensure the correct intertripping sequence-
And then it can get get very complex as those who know far more than me about the HV side mutter darkly about the merits of staggered thresholds for permissive versus direct tripping (*),  And then, at least in the UK , there will be some catch-all that still disconnects eventually even if the inter-trip telemetry fails

In any case, all of this will come out in the wash of inquiring about the primary side protection. If you get an answer you do not understand and there is no clarification forthcoming, then come back and we will see what we can do to help de-mystify it.

Mike.

PS (It is an aside but a permissive intertrip is a sort of voting system where the trip only fires if there is both a  command to trip from the other end of the line and also a local overload at some level,  Direct intertrip is easier to understand but less flexible - if the remote command comes in to trip, then it will always trip - even if the fault is somewhere else)