Electrical Ground Rules White Paper

Best Practices for Grounding Your Electrical Equipment

This electrical ground rules paper is part one of a three-part series that looks at grounding and its role in protecting personnel, equipment, and ensuring the integrity of electrical signals. In this part, we will review circuit grounding and its importance to you, as well as the US AC power system and its use of earth ground.

Topics include the following electrical ground rules principals:

  1. What is Ground?
  2. The Importance of Ground
  3. AC Powered Systems
  4. The Ground Loop

Firstly, the two principal purposes of connecting your system to earth ground:

  1. Stabilize the voltage to earth during normal operation (think of earth like an anchor to the system voltage)
  2. Limit the voltage rise created by lightning, line surges, and unintentional contact with higher voltages

Secondly, the three main purposes for correctly applying ground:

  1. Safety: connect to ground to provide an alternative path for fault current to flow
  2. Limit Voltage and its Variation: connect signals to ground to stabilize them & keep them from floating
  3. Limit the Induced Voltage Magnitude: connect to ground to limit the voltage-rise induced on powered circuits

To this, another very important side-benefit to providing a good connection to earth ground: grounding our circuits to gain electromagnetic compatibility (EMC) benefits that result in lower noise and radiated emissions.