BD700 pilot reported electrical fault messages after engine shutdown and detected electrical burning smell from an aircraft power area during post-flight. Subsequent maintenance action found evidence of arcing and fire in an electrical center with damage to components.

Narrative

Aircraft dispatched ZZZZ1-ZZZZ under MEL with APU GEN inop. Started aircraft under AC GPU and transferred to engine generators. Arranged GPU for arrival during maintenance in ZZZZ. Operations normal throughout flight. After arriving on parking bay in ZZZZ; left engine shut down; GPU connected; right engine shut down. Experienced a break power transfer as aircraft loads not taken by GPU. Reset GPU which then powered some only AC buses 3 and 4. AC buses 1 and 2 not powered. Cycled ground power switch in flight deck and saw further electrical faults. Coordinated with Bombardier Customer Response Center (CRC) to troubleshoot electrical issues in attempt to restore normal AC power to aircraft for follow on flight. Carried out generator switching procedure in accordance with CRC advice but could not restore normal AC power to all buses or generators. Abandoned follow on flight. Upon checking baggage compartment; noted an electrical burning smell from near AC power center located behind sidewall close out panel. Reported this to engineering team.Subsequent investigation by engineer found evidence of a arcing and fire in electrical center originating from a contactor assembly. Extensive damage noted to other electrical components in the power center. Engineering investigation and repairs on going. Background to occurrence:- Electrical issues began on first leg of a 6 leg trip when power did not transition from engines to APU generator on shutdown. This was reported to engineering team.- On second leg operations normal at power up and during flight but same break power at shutdown. - On shutdown after third leg APU generator no longer able to supply AC power to aircraft. Troubleshooting with Bombardier CRC recommended replacement of a line contactor. This was carried out by engineering team who reported ops normal. - On fourth leg ops normal until shutdown when power again failed to transfer to APU generator. - At start of 5th leg MEL'd APU GEN and used GPU to start right engine. Arranged GPU for technical stop as described above followed by additional electrical issues and eventual abandonment of flight. Noteworthy CRM/human factors issues:- An evolving and confusing electrical problem made it difficult for the crew to understand exactly what the issue was. At all stages they followed the guidance of tech support and engineering. - Decision to dispatch from ZZZZ1 under MEL was acceptable and performed without issue.- Combination of final leg of trip plus quick turnaround for fuel led to increased sense of pressure and additional factors to coordinate. - Crew worked through trouble shooting with tech support and considered system configuration and potential further degraded modes in case of engine failure or other inflight emergency and determined that there were too many unknowns and risk was unacceptable. - Crew were not aware that there had been an electrical fire in the AC power center.- Had the decision been made to continue with the fight there was a serious risk of further electrical issues and inflight fire which may have been catastrophic. - Occurrence highlights the unique demands of corporate flight operations which are largely unsupported and require careful threat management by flight crew.