Earth resistance and soil resistivity tester

Earth resistance testing is one of the fundamental requirements for ensuring safety on any household or industrial electrical installation in the provision of an earth electrode. Without an earth/ground electrode, people's lives may be endangered, as well as electrical systems and other property. However, an earth/ground electrode alone is insufficient to ensure ultimate safety. Regular inspections are the only way to ensure that the electrical installation is running properly.

There are numerous ways for measuring earth resistance, based on the type of neutral system, the type of installation (residential, industrial, urban, rural, etc.), and the possibility of switching off the power supply.

 Figure 01: Earth Ground Resistance Tester and Electrode

Why Earthing is necessary?

Earthing is the process of directing an excessive amount of electrical energy's fault current directly into the ground using a low resistance wire. Electrical earthing is accomplished by connecting the equipment's non-current carrying portion of the supply system's neutral to the ground. It assists in the dissipation of excessive fault current directly to the ground, hence ensuring safety. Allow us to discuss the importance of earthing.

What should the earth resistance be set to?

Before you begin any earth resistance measurements, you must first determine the maximum value that is allowed for proper earthing.

Earth resistance standards differ by country, neutral system, and installation type. For instance, a power distributor such as EDF will require a very low ground resistance, frequently less than a few ohms. As a result, it is critical to verify the applicable standards for the installation being tested in advance.

 Generally, two types of grounding are use

1. lightning protection system
2. System Earthing

According to BNBC for LPS maximum value of resistance should be less than 10Ω and for system protection maximum value of resistance should be less than 1Ω.

Soil resistivity

The term "soil resistivity" refers to the resistance provided by the soil to the flow of electricity. The resistivity of the soil is determined by a variety of elements, including soil type, moisture content, and temperature. A soil with low resistivity is ideal for grounding system design. The soil's resistivity is expressed in ohms or ohm-centimeters.

Why soil resistivity measurements are useful

Soil resistivity measurements help you to:

• Specify the electrical characteristics of earth electrodes and earth networks.
• Before construction, determine the locations and types of earth electrodes and earth networks.
• Reduce the cost of earth electrodes and earth networks by optimizing their construction (the needed earth resistance is acquired more rapidly).

As a result, they are frequently utilized on construction sites or in large-scale tertiary structures (or power distribution substations) where it is critical to locate the ground electrodes optimally.

Methods for measuring soil resistivity

Figure 02: Soil Resistivity Measurement

Numerous techniques are used to determine the resistivity of soil. The most often utilized method utilizes "four electrodes," with two alternative approaches:

• WENNER Method: It is ideal for single-depth measurements.
• SCHLUMBERGER Method: It is appropriate for measurements at varying depths, as

                                                     geological soil profiles need

Methods for determining the resistance of an existing earth electrode to the earth

However, different measurement methods may be used depending on the characteristics of the installation: whether it is possible to disconnect the installation's power supply or the earth electrode, whether the electrode to be tested is the only one or is connected to others, the level of measurement accuracy required, and the location of the installation (urban or rural environment).

• Earth resistance measurements on installations with a single earth electrode

Figure 03: Earth resistance measurement with a single electrode

• 3-pole measurement method (62 % method)

Figure 04: Three Pole Earth resistance measurement

• 4-pole earth resistance measurement method

Figure 04: RA 4-Pole Measurement

• Stakeless Ground loop measurement

Figure 05: Stakeless Ground loop measurement

Fluke 1623-2 / 1625-2 Earth Ground Tester

The 1623-2 and 1625-2 Earth Ground Tester (Tester or Product) are a small, field-ready instruments capable of measuring all four types of earth ground. To be more precise, the Tester is capable of measuring earth ground loop resistances using only clamps — a process known as stateless testing. This method eliminates the need for earth-ground posts and does not require the disconnection of ground rods.

Figure 08: Soil resistivity measurement using Fluke 1623-2 earth ground resistance meter

 Key features

• One-button measurement concept
• 3-pole and 4-pole earth ground measurement
• 4-pole soil resistivity testing
• Selective testing, no disconnection of the ground conductor (1 clamp)
• Testing without stakes, rapid ground loop testing (2 clamps)
• Measuring frequency 128 Hz
• IP56 rated for outdoor use
• Rugged carrying case

Fluke 1630 Ground Resistance Meter

The Fluke 1630 Earth Ground Clamp (affectionately referred to as "the Clamp") is a battery-operated hand-held clamp that measures the ground resistance of a ground rod without the use of supplementary ground rods. Without disconnecting the ground under test, the Clamp can be used in multi-grounded systems. Additionally, it is less expensive than other existing models.

Figure 07: System resistance testing using Fluke 1630 ground resistance meter

Key features

• A compact, rugged clamp meter that enables non-intrusive leakage current measurement

for earth ground loop testing

• Features a wide ground loop resistance range, from 0.025 Ω to1500 Ω7
• Measures ground leakage current, from 0.2 mA to 1000 mA, without needing to disconnect
• Measures AC from 0.2 A to 30 A

The Clamp is appropriate for the following applications

• Earth resistance testing of high voltage pylons, buildings, cell phone substations, and RF

         transmitters

• Inspection of lightning protection system

Conclusion

The earthing system is very important for the safety of people and equipment, as it protects against dangerous potential differences. Earth resistance tester is essential for ensuring proper grounding. Soil testing is also an important factor for implementing earthing protection. Earthing protects the personnel from the short-circuit current. It also protects the apparatus from high voltage surges and lightning discharge. Finally, we can say that earth resistance and soil resistivity tester is a must to ensure the safety and efficiency of electrical installation.