Grounding Solar PV Systems

In the context of safety, it is very important to ensure proper grounding in solar PV system. Basic PV module can produce potentially dangerous currents and voltages for the life of the system. Properly maintained grounding helps ensure the overall safety of the system. In electrical and PV systems, there are two types of grounding. They are - equipment grounding and system grounding.

Equipment Grounding: 

Equipment grounding is also known as safety grounding or protective earthing. In this grounding system, all exposed non-current carrying metal parts of the electrical system are effectively bonds (electrically connects) to the earth (ground). By properly bonding exposed metal surfaces together and to the earth, the potential difference between earth and the conductive surface during a fault condition is reduced to near zero, reducing electric shock potential. The proper bonding to earth by the equipment grounding system is crucial, because most of the environment is at earth potential. The conductors used to bond the various exposed metal surfaces together are known as equipment grounding conductors (EGCs).

System Grounding:

When one of the circuits (current-carrying) conductors is bonded (connected) to the equipment grounding system and also to earth is called system grounding. The circuit conductor which is connected to the equipment grounding system and to earth is called the grounded conductor. The connection between the grounded conductor and the equipment grounding system is known as the system bonding jumper. Only one system bonding jumper is allowed in each separate electrical system in which the system grounded conductor is isolated from the grounded conductors of the source or other systems.
Earth Connection:

For making contact with the earth, a metallic device is used which is called the grounding electrode. The conductor which connects the central grounding point and a grounding electrode which is in contact with the earth is known as the grounding electrode conductor (GEC).

Solidly Grounded:

Solidly grounded is defined as connected to ground without inserting any resistor or impedance device in the circuit. In this case, fuses, circuit breakers, and mechanical relay contacts are used in certain grounding circuits.

Grounded Systems:

When one of the DC conductors (either positive or negative) is connected to the grounding system, which in turn is connected to the earth, then a PV system is defined as a grounded system. The conductor that is grounded basically depends on the PV module technology. Most modules can be used with a negative grounded conductor or even in an ungrounded system, but a few PV module technologies require the positive conductor to be connected to earth. 

Color Codes:

The DC grounded conductor must have insulation colored white or gray or have three white stripes if it is 6 AWG (American wire gauge) or smaller. Larger size conductors must be marked with these colors at their termination points. Grounded PV source and PV output conductors 6 AWG and smaller are allowed to be marked in the same manner as larger conductors, in order to allow the use of the durable, black-insulated USE-2 and PV cable/PV wire in exposed locations within the PV array.

Grounding Electrode Conductor—Installation:

The connection between the DC grounded circuit conductor and the grounding system is usually made through the ground-fault protection device (GFPD) internal to most non-battery-based utility-interactive inverters in utility-interactive PV systems. It is important to make a provision for the internal connection of a DC GEC. Microinverters which ground one of the module circuit conductors must have an internal GFPD and will also require a GEC terminal. The connection at the inverter for the GEC is usually a marked GEC terminal. From that terminal on the listed inverter, the PV installer must make the connection to earth through a grounding electrode appropriately.
Prasun Barua

Prasun Barua is an Engineer (Electrical & Electronic) and Member of the European Energy Centre (EEC). His first published book Green Planet is all about green technologies and science. His other published books are Solar PV System Design and Technology, Electricity from Renewable Energy, Tech Know Solar PV System, C Coding Practice, AI and Robotics Overview, Robotics and Artificial Intelligence, Know How Solar PV System, Know The Product, Solar PV Technology Overview, Home Appliances Overview, Tech Know Solar PV System, C Programming Practice, etc. These books are available at Google Books, Google Play, Amazon and other platforms.

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