This might help:
"Buyers Guide To Cable Locators"
<
https://www.tigersupplies.com/LC/Buyers-Guide-To-Cable-Locators-.aspx>
There are some that work at 60 Hz, but most use higher frequencies.
There's just too much interference at 60 Hz. Also, the higher the
frequency, the higher the resolution, which translates in a more
accurately located cable.
"Successful Locating Depends on Knowing Which Frequency to Use"
<
https://www.utilityproducts.com/tools-supplies/article/16003409/successful-locating-depends-on-knowing-which-frequency-to-use>
More than you probably wanted to know:
"The theory of buried cable and pipe location"
<
https://www.radiodetection.com/sites/default/files/Theory-Buried-pipe-manual-V10.pdf>
For what it's worth, I used an RF signal generator to locate buried
cables. The trick is to build a series resonant RF transformer
(ferrite torroid) for your choice of RF frequency. I picked the 160
meter ham band (1.8 to 2.0Mhz), much to the irritation of the local
ham radio operators. The generator was set to about 70% AM modulation
at 1KHz to produce a detectable tone. The resonant transformer will
pass the RF but not the 60 Hz line frequency, thus insuring that there
is some hope that the RF generator will survive the exercise. It also
provides an ungrounded connection to the power line, which should
prevent some types accidental electrocutions.
The difficult part was designing and building a suitable pickup coil.
I finally resorted to a ferrite rod (loopstick) antenna similar to
what is found in many SW (short wave) receivers.
<
https://www.google.com/search?q=loopstick+antenna&tbm=isch>
Such a loopstick antenna a nice deep null in the antenna pattern off
the end of the rod, which makes direction finding possible.
If I were to design a cable locator today, the system would be quite
different. The problem with using only one frequency is that various
types of dirt attenuate different frequencies differently. Instead of
one frequency, I would use a range of frequencies (spread spectrum),
in the hope that at least one frequency will make it through the dirt
(and interference). That's how ground penetrating radar works.
<
https://ieeexplore.ieee.org/abstract/document/9381259>
The last time I had to locate some underground wiring, I was lazy and
used an acoustic method. I made a low frequency "buzzer" that ran
from compressed air. I shoved the air hose as far up the PVC conduit
as possible and turned on the buzzer. With a 1 HP motor, that might
produce 200 watts of audible buzz, which should be audible at ground
level. I used a stethoscope to locate the buried conduit. It wasn't
very precise at locating the conduit, but good enough to provide
clearance for a backhoe trencher.
Good luck.