Protective grounding is the most common grounding we can see in electrical installations. Its main function is to protect people from electric shock, and equipment from its failure in case of emergencies.
But there is one more task that requires grounding: equipment protection from interference. This is a low-voltage impact generally not capable of damaging the equipment or affecting physical human health. However, the absence of such grounding that is called functional grounding (or, in some cases, informational) results in an unpleasant background during operation of sound amplification equipment, communication system failures, etc.
Familiarization with technical grounding standards (such as GOST R 50571.22-2000 and IEC-7) shows that most of them were adopted about 20 years ago. Since then, digital technologies have made a large step forward. Not all aspects have been considered in regulatory documents. Many tasks could be solved only on the basis of experience accumulated by the designers.
For more details, read the article Protective and Functional Grounding: Combined or Individual?.