5 PCB Grounding Methods and 6 Types of Grounding in Circuits

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Fri, Feb 26, 2021

What is grounding? Ground wire or the Ground circuit is the current return path to the electrical or electronic power source. In a circuit, it acts as the reference or the 0V plane. It is common that all the other voltages are measured relative to the ground. The scope of grounding does not limit to just the current return path. In electrical power systems, proper grounding is important for human and property protection. A printed circuit board (PCB) having a ground plane blocks Electromagnetic interference (EMI) and improves heat dissipation in the electronics. Lightning protection systems and surge protection systems rely on proper grounding to work properly.

grounding in schematics

Grounding techniques can be different from the application, location to location, and even country to country. Here we are going to discuss grounding methods used in the electronic and electrical industry and all the main grounding types.

What Methods are Used in PCB Grounding?

There are few methods practiced for grounding in printed circuit boards (PCB). These methods vary from circuit application and the design practice of the PCB design engineers.

  • Method One: Ground Traces

All the components which connect to the ground are connected together from common traces. This is common in old PCBs and simple PCBs.

PCB with only traces

  • Method Two: Common Ground Plane

This is the most common practice in PCB designing. The free space of the PCB which is not utilized by traces or components is covered from the ground place. This method significantly improves the thermal characteristics of the PCB and also helps to reduce electromagnetic interference (EMI).

common PCB ground plane

  • Method Three: Dedicated Ground Layer

This method is used in multilayer PCBs. Components are connected to the ground plane by grounding vias. Can be found in dense complex PCBs with 3 and above layers.

grounding by vias

  • Method Four: Grounding Electrical Power Systems

In power system installations all earth connections are connected to an earth bus bar. This bus bar is connected to an earth conductor which connects to an earth rod or mesh.

earth bus bar

The Earth bus bar collects all the earth wires of all the installations to a common point. The earth resistance of this point should be below 5 Ohms to provide better grounding. A high gauge wire is used to connect the Earth bus bar to earthing arrangement. (Earth Rod and Earth mesh)

earth road connects to earth bus bar

  • Method Five: Equipotential Earthing or Grounding

Equipotential ground means that every conductive element in a protected zone should have the same ground potential. This is achieved by electrically connecting the chassis of equipment, metal pipes, and all earthing arrangements. This ensures that there is no significant potential difference between any conductive part in the zone and prevents electric shock during a fault.

equipotential bonding

Types of Different Grounds

  • Power Ground

This ground is common for both AC and DC voltages. It is the current return path of the electronic circuit. Without the ground, the circuit loop is not complete. Electronic schematics define this ground by the following symbol.

ground GND 0V

Components that have reference to the ground (0V) are indicated by connecting its reference pin to the above symbol. And in the implementation, all the terminals which are connected to the ground (GND) are connected together. Since there are plenty of ground connections. Usually, printed circuit boards (PCB) have a whole plane dedicated to the ground which we will discuss later in this article.

The above symbol is used in electronics and large electrical power systems to mention the grounding connection. In the below image you can see that large transformers are referenced to the ground. The difference is these grounding connections are often earthed by an earthing rod or a mesh. We will describe more into these types of groundings under the Power system grounding methods.

grounding in substatioin

  • Signal Ground

Signal ground is the reference to any analog or digital signal that is used in the circuit. Most of the time signal ground is equal to the power ground. But in some cases signals in the circuit use a different isolated ground to return signal currents. Which leads to defining a separate ground for the signals. These can be found in sensitive equipment and measuring instruments.

signal ground symbol

signal isolator which isolate signal from ground current

  • Virtual Ground

This type of ground is commonly found in Operational Amplifiers (Op-Amps). The point of virtual ground(node) does not directly connect to the ground(GND) current return path but is maintained to match the ground reference potential. Virtual ground is used to analyze the functionality of Op-Amps.

virtual ground of the Op Amp

By considering Virtual ground Ground Potential, and assuming no current is absorbed by the Op-Amp, the following relation is obtained.

formulate

  • Surge and Lightning Protection Ground

Lightning protection systems(LPS) and Surge protection systems need solid ground to dissipate high currents safely. These ground paths have very low resistance and are often welded to structural steel of the building and earthed burying by several earth rods or earth mesh. Equipotential bonding is used between Electrical Power Earth and LPS earth to avoid any voltage difference between earth terminals.

lightning protection system grounding

  • Grounding in Electric Power System

Earthing or grounding in the electric power system varies among countries. These various types are regulated by the International Electrotechnical Commission (IEC). But each country has its own practices and regulations. The main aim of grounding in the electric power system is to provide safety. Here we talk about the earthing arrangement of Low voltage systems or the power distribution system.

These different earthing arrangements are named with two-letter codes.

The first letter indicates the earthing arrangement of the power source. (Distribution transformer)

  • T - Direct connection to the earth
  • I - No direct connection to the earth
  • T - Direct connection to the earth. (Usually earth rod or mesh)
  • N - Earth is supplied by the electricity network.

There are 3 main categories formed from the above arrangements. Which are TT, TN, and IT.

TN systems have 3 subcategories which are defined by the arrangement of Earth conductor(PE) and the Neutral Conductor.

  • TN−S - Earth conductor and Neutral come as separate conductors and join near the power source.
  • TN-C - Earth, and Neutral are combined into one conductor called PEN.
  • TN-C-S - Earth, and Neutral are combined from the power sources as PEN and when it reaches the consumer building it gets separated into two separate conductors of Earth and Neutral.

    different grounding system

  • Floating Ground

Floating ground happens when a system does not have a solid earth connection. And hence the voltage in the ground terminals and conductors are undetermined. The un-intentional floating ground is considered a fault in the system (potential break in the grounding system). But there are applications where the floating ground is intentionally used.

In low voltage supplies and Testing instruments, isolation transformers are used to isolate the low voltage ground from the main grounding system to improve safety. By floating the ground of the low voltage side, It avoids the grounding current path from the main supply. This provides electrical safety if there is a fault at the low voltage side.

floating ground

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When you're done with designing the circuit board, you can ask PCBONLINE to manufacture your PCB. When they receive your quotation request, they will check your Gerber files, so that issues like improper grounding can be avoided. This is free of charge. The reasons to choose PCBONLINE are their high-quality PCB and assemblies, one-stop electronic manufacturing services, and fast delivery. You can get a free quotation online.