Identifying MV Cable

If you can access the cables at each end (say in terminal enclosures), you might be able to measure the amperages, and thus determine what matches what.

This now becomes less certain, but if one transformer is noticeably warmer than the other, and the known loads are significantly different, you may be able to correlate.

Contact your local distribution company. They should have high precision radio locators. I used one a few years back on a MV system management course. Part of the training network had deliberately crossed cables in the same trench as part of the cable location training. We successfully identified the cables. This is the unit we used. Expensive which is why I suggest your local distribution company.

Considering the safety implications, ruling out an outage wouldn't be acceptable as defence in the event of an accident. Production does not override safety.

Nassar, there are 3 different ways to accomplish what you seek:

First, you can do as Tornado suggests and try to correlate current readings. Even if you can't get access individual conductors in the PILC cable, you should be able to access the other side of the interrupting device (circuit breaker, contactor, fuse, etc.) and use a clamp-on ammeter. Ideally the switchgear has an installed ammeter for each interrupting device, but that is not always the case.

Second, you can do as TonyS recommends and use a RF locator. These can be used with the cable energized. If the local utility is unwilling or unable to assist, a larger electric contractor in the area may also have one, or they are available for rent depending on your area.

Third and simplest, don't worry about it. If and when the cable fails it will be very easy to correlate the blown fuse or tripped breaker with the de-energized transformer.

If none of these options will work for you but you still need to know which cable serves which transformer, accept the fact that you will have to arrange for a one-time outage to verify source and load.