Hi Facetoface.
Just my opinion, base on few cases was happend at the last mounth.
1. Check first energazing procedure with trafo mnf.
Read this post.
thread238-218517
2. Check all fire systems and gas.
2.1 check place of fire services hydrants and water.
2.2 check push button " fire trouble" and check that this operation disconnect all power supplies.
2.3. Put guys from fire service near to this hudrants with your electrical guys.
2.4 please order one or two mobiles of fire service
3. Check "place" of oil in case of trafo fault.
4. Check option of energazing trafo from very weak line, with lowerst level of SC., if trafo mnf. haven't some special requerements and you have option --energize from low side
5. in additional to diff 87T trafo protection and 50/51
add temprorary 50/51/50N/51N settings with minimum time settings on the infeed line.
Just my opinion.
Best Regards.
Slava