Power Quality Problems

The most common types of Power Quality problems are presented in the following Table

Power quality

What is Power Quality?

1. The concept of powering and grounding sensitive equipment in a manner that is suitable to the operation of that equipment.”
2. “Within the industry, alternate definitions or interpretations of power quality have been used, reflecting different points of view.”
3. The definition of Power Quality cannot be limited to the characteristics of the supply power. The definition must also include the requirements of the load.“

Power Quality Solution Strategy

1. good grounding system 
2. Harmonic solutions
3. Surge solution 
4. Voltage variation solution 

Grounding Codes and Standards

 Ideally a ground should be of zero ohms resistance. The NEC has stated that "A single electrode consisting of a rod, pipe, or plate which does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode..." Once you have added the supplemental ground you have met the requirement for the NEC.

This does not mean that the value of the ground now has to be 25 ohms or less. The ground resistance values objectives vary from industry to industry.

Telecommunications industry has often used 5 ohms or less as their value for grounding and bonding. The goal in ground resistance values is to achieve the lowest ground resistance value possible that makes sense economically and physically

The need to ground

There are important reasons why a grounding system should be installed.

1- The most important reason is to protect people

2- Protection of structures and equipment from unintentional contact with live conductors


3- Ensure maximum safety from electrical system faults and lightning.

The meaning of earthing

It is a fundamental fact that electricity ALWAYS flows to the point of lowest potential. The task is to ensure that electricity, including faults, lightning and electronic noise, and flows to this point with maximum safety to people, while maintaining the reliability of equipment. Therefore we must ensure the safe, controlled flow of electricity with minimum voltage drop to earth in all cases.

The different between earth and ground 

  Ground:

The NEC, National Electrical Code defines a ground as: A conducting connection, whether intentional or accidental, between an electrical circuit or equipment and the earth, or to some conducting body that serves in place of the earth.

Earth:

The conductive mass of the earth, whose electric potential at any point is conventionally taken as equal to zero. (In some countries the term "ground" is used instead of "earth.")