Because the panel must be connected to the.
Grounding electrical panel.
If your electrical cables have metal sheathing that runs all the way to the panel the sheathing can serve as a ground path.
When this happens you must bring an appropriately sized equipment grounding conductor over with the circuit to the subpanel you must not have a neutral to ground bond in the panel and the grounding electrodes are optional although highly recommended.
Alternatively you might consider connecting the ground terminal to a water pipe by means of an exposed ground wire.
Grounding and bonding happen simultaneously during the installation of an electrical system and branch circuits.
By shunting excess line voltage back to the panel s neutral pole the ground current forces the circuit breaker to trip.
The wires that bond your metal piping are preventative and they only become important in the unlikely event that an electrical conductor energizes the pipe.
The grounding pathway is generally formed by a system of bare copper wires that connect to every device and every metal electrical box in your home.
Grounding a main panel the ground bar is bonded internally when an external bond to earth is installed as described at the link for electrical grounding below.
The grounding wire that runs from your electrical panel to grounding electrode helps even out voltage increases that often occur because of lightning and other causes.
In standard sheathed nm cable this bare copper wire is included along with the insulated conducting wires inside the cable.
Your service panel s ground wire prevents a line fault from becoming a shocking experience.
Which scenario is recommended.
The tripped breaker shuts off the circuit s current preventing a potentially dangerous situation.
They work hand in hand in order to make it safe.
Two problems make the safety of these approaches questionable.