Ground wire shock

I would turn the breakers off 1 by 1 to see which 1 or more is leaking to ground.
Leave the breaker(s) off and see what is on that circuit, lights, fans, recepticles. Could be anyone of them.
Unplug items plugged into the recepticles, and turn off any switches, then look for the voltage on the ground, worse case you will need to open boxes and connections to further isolate.
Be carefull, Good Luck.

I found one circuit that has 52 volts between the ground wire and the ground bar. I unplugged everything on that circuit and turned off the lights. No change. What do I look for next?

If you can work safely at the Panel and with Electric, You could Turn off that Breaker/Circuit. And Place a Continuity tester between the hot and ground, and start disconnecting til the Beeping/buzzer/light/Meter show an open connection between the hot and ground. Also turn off any lights, fans etc, and unplug anything in the recepticles. Could be something plugged into the circuit, not necessarily the wiring itself.

If it's not what is plugged into the outlets what in the outlet box could it be? What should I look for?

I would open related switch boxes, light/fan/smoke detector boxes and seperate the hots, if the continuity is removed, it is downline from that connection.
A screw or nail can puncture the hot and short to ground, any recent work?

I Take it you seperated the grounds at the panel to determine which of the 3 circuits has the Problem.

How is this panel being used?
This sounds like a sub panel in a garage or a shop.

Are the neutrals and grounds connected to the same buss in this panel? This sounds like a 120V sub panel in a garage with neutrals and grounds connected at neutral buss. They should not be.

Was that the ground wire a the ground rod?
Sounds like the braided ground wire between a sub panel and the main panel.

When you did that voltage check did you check on ground wire with the other two disconnected from the panel, or did you check one with the other two connected to the ground buss?

If you have two circuits come together in a box, grounds of both circuits will be connected. In other words if you have two sets of lights on different circuits, and have the switch for each set in the same box, the grounds will be connected. There are other situation where the grounds of two circuits may be connected.

If your grounds and neutrals come together a sub panel and you have poor connection in the neutral, either in the sub panel or the main panel, and you disconnect the ground between panels, then touch the ground and the box you will get shocked.

This is in a sub panel 100 amp/220V in the other half of the cellar. The electrian who put in the new 200 amp panel did not make the 100 panel a sub meaning he left the neturals and ground connected on the same bar. I am in the process of seperating the ground and neturals. that is when I found the shock problem. It is not there on all the grounds.

Confirm that braided ground is the ground between the sub panel and the main panel.

If there is a break in the neutral between the sub panel and the main panel and you disconnect the ground between panels, nothing in the sub panel should work.

no the braided ground is 6 or 7 copper ground wires twisted together and then screwed into the netural bar. I have just split the netural and grounds in the sub panel and isolated the netural. the netural from the main panel has good contact. Still get conductivity between the ground and the hot on one circuit but not enought to trip the breaker. Using a GB outlet polarity tester on all the outlets shows 2 orange LEDS meaning correct wiring at the outlet.