Solar Toolbox – Grounding

Bonding is simply a matter of taking all of the electrical and metallic masses in a facility and connecting them with conductors, bringing them to the same electrical potential. The primary reason for bonding is personnel safety, so someone touching two pieces of equipment at the same time does not receive a shock by becoming the path of equalization if they happen to be at different potentials.

Grounding is a matter of bringing the bonded equipment mass to the potential of the surface of the earth which it occupies. The purpose of grounding and bonding is to protect you from the danger of electric shock. Grounding and bonding achieves this by ensuring that when an electric fault occurs, the potential of the metal parts of enclosures will be maintained at a safe value with respect to earth and/or the fault will cause the system to be disconnected by a protective device.

The following is an excerpt from the Trace Engineering Technote TN7

One Ground for All Equipment

If an electrical system has components grounded at different points in the earth, large voltage differences will exist between these points during a lightning strike (Figure 1). If this voltage appears between the AC and the DC side of the inverter, it will fail.

The first step in inverter protection is to make sure that all equipment in the system is grounded at the same location. This assures that there is no voltage potential between grounds in the system (fig. 1). No voltage means no current flow through the system. Practically speaking, this would mean connecting the generator and battery grounds together, as well as the case or safety grounds in the system, and then attaching all to the same earth grounding rod.

All equipment involved in a system should be kept as close as possible to one another. This reduces the potential that is developed between the ground site and the individual components of the system during a lightning strike. The single point grounding greatly reduces the potential for lightning damage to electrical equipment. If you are unable to achieve single point grounding due to large distances between equipment (or other variables) other means of lightning protection must be considered. Consult a reputable lightning protection company.