To provide a loop switching support apparatus capable of easily determining the propriety of a loop switching operation, even when output adjustment of a generator is difficult or in an emergency.

The loop switching support apparatus 10 is used in switching a power supply destination of a loop turning-out site to a loop turning-in site. The apparatus 10 is provided with an advancing side system detecting unit 12 for detecting an advancing side system viewed at the loop turning-on site, on the basis of phase difference data to be input from a phase difference measurement device 21 provided on the loop turning-in site; and a control unit 13 for determining whether loop switching is possible, by executing parallel use turn-off for a two-line parallel use medium transmission line of a first section adjacent to the advancing side system and/or a second section.

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