Method for de-energized maintenance of a stationary transformer station on a medium-voltage network, - wherein, during normal operation of the stationary transformer station, a first neighboring station is connected to a first network operator feed of the stationary transformer station, - wherein, during normal operation of the stationary transformer station, a second neighboring station is connected to a second network operator feed of the stationary transformer station, - wherein the first network operator feed of the stationary transformer station is switched to a de-energized state, wherein a load break switch associated with the first network operator feed of the stationary transformer station is opened, and wherein a load break switch associated with the first neighboring station is opened, - wherein the first network operator feed of the stationary transformer station that is switched to a de-energized state is connected on the medium voltage side to a first network operator feed of a mobile transformer station by means of a first cable connection, - wherein a customer installation is connected on the low voltage side to the mobile transformer station by means of a second cable connection, - wherein the mobile transformer station is operated (78, 80) in parallel with the stationary transformer station, wherein the load break switch associated with the first neighboring station is closed, wherein a load break switch associated with the first network operator feed of the mobile transformer station is closed, wherein a safety circuit breaker of the mobile transformer station is closed, and wherein a low-voltage-side load break switch of the mobile transformer station is closed, - wherein the stationary transformer station is switched to a de-energized state by means of the mobile transformer station, wherein the stationary transformer station is disconnected from the medium-voltage network by opening a load break switch of the second neighboring station and is disconnected from the customer installation by opening an isolator switch of the stationary transformer station, and wherein the second neighboring station is disconnected from the second network operator feed of the stationary transformer station, - wherein the second network operator feed of the stationary transformer station that is switched to a de-energized state is connected on the medium voltage side to a second network operator feed of the mobile transformer station by means of a cable connection, and - wherein the load break switch of the second neighboring station is closed. - wherein, during normal operation of the stationary transformer station, a first neighboring station is connected to a first network operator feed of the stationary transformer station, - wherein, during normal operation of the stationary transformer station, a second neighboring station is connected to a second network operator feed of the stationary transformer station, - wherein the first network operator feed of the stationary transformer station is switched to a de-energized state, wherein a load break switch associated with the first network operator feed of the stationary transformer station is opened, and wherein a load break switch associated with the first neighboring station is opened, - wherein the first network operator feed of the stationary transformer station that is switched to a de-energized state is connected on the medium voltage side to a first network operator feed of a mobile transformer station by means of a first cable connection, - wherein a customer installation is connected on the low voltage side to the mobile transformer station by means of a second cable connection, - wherein the mobile transformer station is operated (78, 80) in parallel with the stationary transformer station, wherein the load break switch associated with the first neighboring station is closed, wherein a load break switch associated with the first network operator feed of the mobile transformer station is closed, wherein a safety circuit breaker of the mobile transformer station is closed, and wherein a low-voltage-side load break switch of the mobile transformer station is closed, - wherein the stationary transformer station is switched to a de-energized state by means of the mobile transformer station, wherein the stationary transformer station is disconnected from the medium-voltage network by opening a load break switch of the second neighboring station and is disconnected from the customer installation by opening an isolator switch of the stationary transformer station, and wherein the second neighboring station is disconnected from the second network operator feed of the stationary transformer station, - wherein the second network operator feed of the stationary transformer station that is switched to a de-energized state is connected on the medium voltage side to a second network operator feed of the mobile transformer station by means of a cable connection, and - wherein the load break switch of the second neighboring station is closed.