What is an Earth Enhancing Compound?
Earth Enhancing Compound is a mix of minerals that helps reduce the resistance of an earth termination system. It absorbs and retains moisture, so the system stays conductive even in dry conditions. This keeps your earthing safe from electrical hazards.
In this blog, you’ll learn which all tests you need to run, and why they matter for your electrical safety.
Below are the 6 tests that will ensure the quality of your Earth Enhancing Compound.
- Resistivity Determination
- Moisture Retention Test
- Thermal Stability Test
- pH Value Test
- Leaching Test
- Sulphur Determination
- Corrosion Test
- RoHS Compliance
Now, let’s go through each test in detail.
1. Resistivity Determination
This test measures how effectively the compound reduces electrical resistance in an earthing system. To perform this test, the four-electrode method is used. In this method, the sample is placed in an Earthing compound box such that it ensures good electrical contact between the compound and the electrodes.
A uniform pressure of 100 Newton per meter square is applied and maintained for 1 hour and then the resistance is measured using an earth resistance meter. Then the resistivity is calculated as per IEC 62561 part 7 using below mentioned formula:
Where:
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ρ is the sample resistivity
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R is the measured resistance
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A is the cross-sectional area of the container perpendicular to the current flow (m²)
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a is the spacing between the inner edges of the electrodes (m)
A high-quality compound, such as Axis Earth Enhancing Compound (Axifill), achieves a resistivity of 12 ohm-meters or less, as specified by the manufacturer. This confirms Axifill’s effectiveness in dissipating fault current into the ground.
2. pH Value Test
This test measures the pH level of slurries made from earth enhancing compounds. The goal is to confirm that the compound remains chemically and physically inert when in contact with earth electrodes. A stable pH helps prevent corrosion and avoids harm to the surrounding environment.
The pH meter is first calibrated using standard reference solutions, based on the expected pH range. Next, the electrode of the pH meter is immersed directly into the slurry and the pH value is then recorded. This test helps assess the chemical aggressiveness of the compound. A suitable earth enhancing compound will maintain a neutral or near-neutral pH value.
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3. Leaching Test
This test evaluates how Earthing compound materials release inorganic and organic constituents into water under controlled laboratory conditions. It simulates the natural leaching processes that occur when rainwater or groundwater interacts with the Earthing compound.
The test aims to determine the potential environmental impact of Earthing compound contamination and assess the mobility of hazardous substances.
To begin, technicians prepare a representative Earthing compound sample, sieved to a particle size smaller than 2 mm. Each test uses about 100 grams of the compound based on its dry weight. They place the Earthing compound into a clean, inert container such as a polyethylene bottle. Then, they add a leaching solution-typically deionized water-at a liquid-to-solid ratio of 10:1 (for example, 1000 mL of water for 100 grams of compound). After sealing the container, they place it on a rotating platform set to 10 rotations per minute.
This agitation continues for 24 hours at a controlled temperature. Once the leaching period ends, technicians filter the Earthing compound-water mixture using a membrane filter to remove particulates and obtain a clear leachate.
In this test, analysts measure pH, conductivity, and major anions like iron, chloride, sulfate, nitrate, and others. They also test for heavy metals such as lead, cadmium, copper, nickel, cobalt, and zinc, along with organic parameters like dissolved organic carbon, if required. The test determines these anions through Ion Chromatography (IC), using separation and quantification methods.
4. Sulphur Determination
This test checks the amount of Sulphur in the compound. High Sulphur levels can leach into groundwater or surface water, leading to pollution. To avoid this, the Sulphur content must stay within safe limits, set by environmental and safety guidelines.
IEC 62561 states that an earthing compound passes the Sulphur test only if the measured value is less than 2 percent. The test must be carried out as per ISO 4689-3 or ISO 14869-1. Lower Sulphur levels protect Earthing compound quality and ensures long-term safety of the earthing system.
5) Corrosion Test
This test checks whether the earthing compound causes corrosion to the earth electrode. To ensure long-term reliability, the compound must remain physically and chemically inert and must not damage the electrode over time.
The test uses the Potentiodynamic Polarization Resistance method, following the ASTM G59-97 standard. A three-terminal potentiostat serves as the core instrument for this procedure.
Technicians place the earth electrode—either a GI rod or a copper-bonded rod—into the sample along with two reference electrodes. They connect all three electrodes to the potentiostat and use a Galvanostat to measure the polarization resistance.
For copper-bonded rods, the measured resistance must exceed 4 ohm-square meters in non-aggressive environments and 8 in aggressive environments. For galvanized rods, the minimum required resistance is 3 ohm-square meters for non-aggressive conditions and 7.6 for aggressive ones.
According to IEC 62561-7, every compliant compound must carry the manufacturer’s name, trademark, batch number, resistivity value, testing method, installation instructions, and a conformity statement to ensure traceability and compliance.
6) Restriction of Hazardous Substances – RoHS Compliance
The RoHS Compliance Test verifies that materials contain hazardous substances within regulatory limits, ensuring both environmental and health safety. The test focuses on key substances such as lead, mercury, cadmium, hexavalent chromium, polybrominated biphenyls (PBBs), and polybrominated diphenyl ethers (PBDEs).
The process begins with the preparation of a powdered sample of the material. Technicians perform initial screening using X-Ray Fluorescence (XRF) Spectroscopy-a fast, non-destructive technique that detects heavy metals. If any substance approaches or exceeds threshold levels, they confirm the findings through Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) or Mass Spectrometry (ICP-MS), following acid digestion of the sample.
Analysts then compare the detected concentrations with RoHS limits, such as 0.1% for lead and 0.01% for cadmium. To prevent false positives, they validate any positive findings through detailed chemical analysis. The test concludes with the issuance of a compliance certificate, which summarizes the results and confirms whether the material meets RoHS requirements. By completing this test, manufacturers ensure their products are environmentally safe and legally compliant for sale in global markets.
7) Moisture Retention Test
This test measures the compound’s ability to absorb and retain water over time. The process starts by weighing a dry sample of the compound, usually around 200 grams. The sample is then placed in a controlled container, and approximately 100 millilitres of water is added.
The sample is left undisturbed for 24 hours at room temperature. After that, any unabsorbed water is removed using a filter or mesh. The wet sample is then weighed. Next, the sample is dried in an oven at 60 to 80 degrees Celsius for another 24 hours and weighed again. The difference in weight before and after drying is used to calculate the moisture retention percentage as per this formula.
Moisture Retention (%) = (Wet Weight − Dry Weight After Heating) ÷ Initial Dry Weight × 100
A good Earth Enhancing Compound should retain between 30 to 50 percent moisture, depending on its formulation. It should not leach water or lose its form.
8)Thermal Stability Test
This test checks how the Earth Enhancing Compound performs under extreme temperature changes. The compound is exposed to repeated heating and cooling cycles to determine its stability against environmental stress. The goal here is to ensure that the compound’s electrical resistivity stays stable, and its physical structure does not break down. The process begins by preparing three test samples, each weighing 500 grams. These samples are first dried in an oven at 105 degrees Celsius for 24 hours to remove any moisture. They are then cooled to room temperature in a desiccator. The thermal cycle starts with heating. Each sample is placed in an oven at 80 degrees Celsius for 24 hours. Then they are moved to a cold chamber, set at minus 40 degrees Celsius for another 24 hours. This cycle is repeated 10 times over 20 days.
Post completion of the cycles, the following checks are performed:
- First Resistivity Measurement. Measures the electrical resistivity using the Wenner Four-Point Method. The change in resistivity must stay within ±10 percent of the original value.
- Next, Visual Inspection. Inspect the sample under a magnifying glass. There should be no cracking, powdering, phase separation, or surface damage.
- Lastly, Chemical Check. Perform a pH test to confirm chemical stability. The pH should remain between 6 and 10.
