Electrical bonding is a process in which parts of an electrical assembly or sub-modules within a system are connected electrically by their joints or by any low-resistance bonding media (Jumpers). Electrical bonding is a process of connecting metallic objects that may be exposed to electrical faults or induced voltages to the grounding conductors. This ensures that in the event of a fault, the current will have a low resistance path to take to trip the over-current devices as quickly as possible, as well as provide a path for static electricity and induced voltage to drain out.
In other words, electrical bonding is simply the act of joining two electrical conductors together. Bonding has to be done by connecting all the metal parts that are not supposed to be carrying current during normal operations to bring them to the same electrical potential. It ensures that these two bounded things will be at the same electrical potential. That means we would not get electricity building up between two different pieces of equipment.
The main purpose of electrical bonding is to make a homogeneous structure with respect to the flow of radio frequency (RF) current so that it would experience the minimum barrier as it crosses one surface to the other without developing electrical potential at the crossover point. Bonding to electrical earth is used extensively to ensure that all conductors (Person, surface, and product) are at the same electrical potential. When all the conductors are at the same potential then no discharge will occur.
Electrical bonding requirements
The main function of electrical bonding is to create a homogeneous structure to allow a smooth flow of RF current. So that it will experience minimum resistance to the flow of current. It doesn’t create any potential at the joint or crossover point. In order to ensure electromagnetic compatibility (EMC) specification the various components of a module or all the modules of the system are connected to a common chassis or common reference ground via low impedance electrical path that should provide non-zero impedance at all frequencies. This kind of bonding provided to meet EMC specifications is known as EMC Bond and the process is known as EMC Bonding.
The main purpose of electrical bonding is to prevent voltage difference between two parts being joined.
Why Electrical bonding is important?
One of the important uses of electrical bonding is to reduce the touch potential, especially in the case of long runs of conductive cable trays. Whenever voltage is applied to the conductor, it can be a wire or anything in its metallic body, there will be some residual voltage drop across the length of the conductor based on its size, material, and length. There is some resistance even in highly conductive copper and aluminum. Then due to this resistance based on the distance from the nearest grounding connection, a small potential difference can occur. If there is a difference between a cable tray and a nearby staircase, then someone who touches both metal objects at once might experience an electrical shock.
A more frequent electrical bonding connection will reduce the potential between metallic objects and it decreases the chances of unintentional electrical shock from static or induced voltages. On large electrical sites, potentially flammable or explosive fluids or gases are available in an adequate amount. Even a small static spark can be dangerous. Hence care must be taken to ensure that electrical bonding connections are secure and frequent enough to minimize the risk of fire or explosion. Residential swimming pools can also be susceptible to touch potential differences, especially when water meets metal surfaces. Metal parts of pools, hot tubes, and fountains must be bonded to the earth to reduce the risk of electrical shock to anyone who might come in contact with these surfaces, especially when the humid environment increases the chances of providing a path to the ground through a person’s body.
Types of Electrical bonding
To perform bonding at DC or low power frequencies (i.e. 50 or 60 Hz), a simple but durable permanent low-resistance joint can be adequate. To accomplish this kind of low resistance, a bond between these two metal walls, a hole can be drilled in the adjoining parallel walls and the two cabinets can be bolted together with the star washers at the point of contact between the walls. These bonds are created by using bolts and star washers at the point of contact between the two walls. However, such a bond is not suitable at high RF or microwave frequencies due to its high resistance and inductive reactance. An electrical bond involves dissimilar metals where non-linear junctions can develop at the bond, leading to the generation of harmonics, especially under the strong RF fields that cause interference.
To reduce the above problem a radical approach is required if the bond is to work at high frequencies. The most effective method is to divide the bonding process into two categories Mechanical bonding and Electrical bonding.
impedance path between parts to be joined makes them electrically robust. Electrical bonding is classified into two types:
- Direct bonding
- Indirect bonding
Electrical bonding of Earth wire
Electrical bonding behavior at RF
This circuit acts as a parallel resonance circuit. So the circuit provides very high impedance at higher frequencies. Due to the skin effect at a higher frequency, there becomes a flow of current via the outer surface of the conductor. Hence due to this, the bond offers very high resistance in the circuit.