In context, ground support equipment, or in this case, electrical ground support equipment (EGSE) is the electrical test racks that plug into the vehicle for ground testing. These are things that simulate all manner of things that can't be actually simulated (solar panel power, battery under/overvoltage--or just batteries in general as they're typically not installed through most of testing--GNC inputs, etc.) and then a master control that is the thing that actually sends the commands to the vehicle, including encryption and decryption once that's actually enabled.
If I'm reading between the lines, "damaged by a power surge" translates into "someone ****ed up an electrical mate". Batteries are often hot mates, and batteries are often not installed until "final" activities/checkouts/processing/whatever a mfg calls the last bit of stuff going on. Total speculation, but...I've seen what happens when someone screws up a battery mate...
