Earthing system is a security application made to ensure equipment and life safety against possible electrical leakage in electrical equipment. This process in the system against electrical leakage that may occur; It is an indispensable system that ensures the safety of both equipment and employees. Grounding installation is required in residences and facilities.
Grounding measurement; The Electricity Plant and Grounding Regulation is made within the framework of the Electricity Internal Installation Regulation and other regulations.
These measurements are once a year for fixed facilities and once every six months once time for displaced machinery and equipment; It must be done by an authorized Electrical or Electrical Electronics Engineer with an SMM certificate.
What are the Types of Grounding?
The grounding installation to be applied in the facilities can be classified in 4 ways according to their purposes.
- Protection Grounding: It is an application to protect people and other living creatures against touch voltage in case of any electrical malfunction. It is made by connecting the parts of the equipment that are not under tension with the conductor to the ground. We can define it as the transmission of the current that will harm human health in the event of possible leakage to the ground through the conductor. With this method, external metal surfaces that are dangerous for conducting electricity by touch are protected. Earthing in places such as motor bodies, escalator surfaces, panel plates, etc. is made for protection grounding.
- Operation Grounding: It is an application made to protect the electrical circuits in the network against high voltages that may occur. The purpose of the system is to prevent the voltage between the system and the ground to exceed a certain value in low voltage networks.
- Function Grounding: It is an application made for a specific purpose requested by the enterprise.
- Lightning Protection: It is an application made to protect buildings and electrical facilities against lightning. In the event of a lightning strike, it is to prevent jumping to the energized conductors of the enterprise and to direct the high pulse current caused by lightning to the ground. The purpose of this application is to limit the high pulse current value that occurs and prevent it from damaging the system. Units such as lightning rods and surge arresters in electrical systems prevent damage caused by lightning strikes from damaging the system. It is classified in 4 ways according to the lightning protection application method.
What are Grounding Types?
The grounding installation to protect the health of the personnel and the electrical equipment varies according to the application method. The system to be applied must be selected according to the business life scenario and intended use.
Low voltage systems are classified in 3 ways in our country and international grounding regulations. These are TN, TT and IT.
- T: Terra
- I: Isolation
- N: Neutral
- C: Combine
- S: Seperate (It is used as the 3rd letter in some systems.)
The meanings of the letters used in the classification are as follows:
For Letter 1:
It tells the connection of the power system to ground, that is, the structure of the transformer system and the type of grounding.
- T: In practice, the point is directly connected to the ground. In other words, one point of the network (like a star point) is grounded.
- I: It is the separation of all points under voltage from the ground or connection to the ground through an impedance. In other words; all of the active equipment is isolated against ground or one point in the network is connected to ground through an impedance.
For Letter 2:
Describes how the conductors exposed in the electrical installation are connected to the ground. More specifically, it describes the condition of the conductive part of the equipment against the ground.
- T: Regardless of the grounding of any point in the system, it is the electric direct grounding of the place to be applied.
- N: It is the direct connection of the exposed conductive part to be grounded to the grounded point of the electrical system. In low voltage systems, the grounded point of the system is normally connected to its neutral point.
Letter 3 on some systems:
- S: It refers to the protection function with a conductor separate from the neutral or grounded conductor.
- C: It is the connection of ground and neutral system through a single conductor (PEN conductor)
TN System
It is the most widely used system. There is a directly grounded point in this system. The conductive parts exposed in the electrical system are connected to this point. This operation is operating grounding point. There are three different methods, TN-C, TN-S and TN-C-S, depending on the type of application of the TN type system.
TT System
It is a system in which the grounding point is directly connected in the electric grid systems and the conductive surfaces are connected to the grounding electrode separately from the grid grounding system. While the grounding of the transformer star point in the power system is the operating ground; The grounding of the conductive parts of the facility separately from the operating grounding is also the protection grounding.
IT System
In this application, the star point of the transformer system is made from a circuit element that is isolated from the ground or this point has a very high impedance value. Equipment in the system is grounded separately. In this application, the first phase ground fault occurring in the system does not affect the equipment connected to the system.
What Are The Factors Affecting Earth Resistance?
The ground resistance indicates the resistance of a cube with an edge of 1 meter. Soil resistance can vary depending on environmental factors.
- Herbal structures and electrical plants. Different grounding electrodes may be needed for changes.
- Equipment that may cause electrical noise in the facilities may cause errors in measurement due to the noise source.
- The presence of non-metallic pipes or channels.
- Soil is moist or dry.
How to Measure Earthing Resistors?
It is the reaction of the soil when it transmits electric current. Although soil conductivity is low; If the area is large, the resistance value is low and it can become a good conductor.
Earth resistance is generally measured as 2 piles (3 probes). The two electrodes are driven deeply into the ground, approximately 5 meters apart. Soil in the area to be measured (where the electrodes are nailed) helps to reduce the earth resistance.
How to Measure Earthing?
The electrical facility grounding regulation, the measurements made within the scope of the electrical internal facilities regulation, should be made by expert and competent Electrical or Electrical Electronics engineers with SMM certificate by the Chamber of Electrical Engineers and calibrated grounding measurement device issued by authorized.
- Measurements should be made by experts and authorized persons.
- Calibration of the device should be done in earthing measurement.
- If the measurement location is an industrial facility, the grounding system should be investigated and what type it should be determined. If there is a TN type grounding system, the loop impedance protection conductors should be checked from the project.
- In the TN system, it should be checked whether the protection conductor is connected to the transformer output neutral bar.
- Soil specific resistance needs to be measured.
- Earthing resistance needs to be measured.
At What Intervals Should I Take Grounding Measurement?
- Once every two years in electricity generation, transmission and distribution centers
- Once in five years in energy transmission and lines
- Once a year in industrial industrial centers and business centers
- Once a year in workplaces that work with explosive and dangerous substances
- Stationary operating equipment once a year
- For unstable operating equipment, measurements should be made every six months.
