We have the Ideal 958 kit and it has worked for this exact situation before. The trouble is that sometimes it works and sometimes it does not. We did not need a TDR in our case, because we were able to trace the energized portion until the signal dropped.
The 958 is not strictly an underground tracer, and Ideal does;t claim it to be, but the handy video shows someone tracing out pole lights in a parking lot, which I have a hard time believing.
Please let us know what works, I enjoy learning from all of you.