Earthing

Loads of them:

• British Standard 7671
• Indian Standard 3053
• Etc.

The purpose of the earth conductor is to operate the circuit protective device(s) in the event of a fault. So it is strongly recommended that instruments are bonded to a separate earth bar to the power equipment and the connection between the instrument earth and the main power earth be as close to the main earth point as is practicable. The reason is that a fault in a piece of power equipment will have the least influence on the instrumentation that way round; a surprise blat and a blown fuse on a heavy motor cable is then of least significance in terms of keeping the rest of the plant running safely.

Indian Standard 3053 Indian Standard 3043

The basic purpose of grounding and bonding in a power system is to put all devices at the same earth potential.Internal grounds on the dc supplies is different,and may require separation of digital and analog circuits and under certain circumstances,capacitive coupling between the two to prevent interference with each other.

If you install a separate ground rod or grid,you should make sure that it is bonded to the main power ground system with as low of a resistance as possible to prevent a difference in potential between the two ground systems.

Consider a resistance between two ground rods or grids of only .1 amps.A typical lightning bolt can carry 100,000 amps and millions of volts.It also creates a very intense high frequency electromagnetic pulse which can induce voltages in metal equipment.

The lightning pulse can create 10000 volts difference in potential between the grounds,and consequently,the equipment.A person in contact with the equipment at this instant can be seriously hurt or worse.

I am speaking here mainly of the safety aspect of bonding and grounding,not the internal dc circuit itself.

For more details refer to this link:

https://www.mikeholt.com/instructor2/img/product/pdf/1292448885sample.pdf

There's loads to read here.