disconnect switch 1001 was measured as 40.2ms. It should be observed that 1001 is a disconnect switch, resulting in the need to also send trips to the feeder breakers. During the test, an error was found related to the dead bus condition and TO block signal from bus 2. Bus 2 was sending Bank 1 Fault Bus 2 TO Block Bank 1 TO Enabled Initiate Bank 1 TO 2 s Dropout 1001 Open Close 420 Timeout of 5 s Initiate Bank 1 TO a block not permitting the TO to happen. The problem was found to be in a setting for the threshold of an undervoltage (27/PTUV) element used for the dead bus calculation of bus 2. The TO operated as expected after this setting was adjusted to the correct value. The TO initiate was sent with Initiate Bank 1 TO Timeout of 5 s 420 Open figure 10. Throw-Over logic in IED Bank 1. Bus 2 Dead Bus Bank 2 TO Failure Bank 1 TO Failure Bus 2 TO Block Bus 2 Fault 420 BF 436 BF 446 BF Bank 2 Load > Bank 2 Limit Initiate Bus 1 Loadshed Initiate Bank 2 TO 420 Closed figure 11. Throw-Over block and bus load shedding logics in IED Bank 2. April 2022 Show Issue ieee power & energy magazine 113