Earth Electrode Testing

Introduction

• Focus on testing earth electrodes.
• Earth electrodes (F electrodes) are uncommon in the UK.
• New installations typically do not require them.
• If present, electrodes must be tested for proper installation and low impedance.

Types of Testing Methods

Easy Method

• Most common method: external impedance test using mains power.
• Connects a two-wire deal between the earth electrode and the building's supply.
• Requires mains power.

Difficult Method

• Used when mains power is not available (e.g., new installations).
• Requires a battery-operated earth electrode tester.
• Time-consuming and requires specific testing equipment.
• Recommended to have multifunction testers that include this function.

Testing Procedure for Earth Electrodes

1. Initial Setup

   • Ensure the electrode is installed underground.
   • Test equipment typically requires three connections:
     • One wire to the earth electrode.
     • Two temporary electrodes placed away from the main electrode.

2. Electrode Placement

   • Temporary electrodes must be spaced at least 10 times the depth of the main electrode.
   • Example: For a 2-meter electrode, temporary electrodes need to be at least 20 meters apart.
   • Ground must be soft enough to insert temporary electrodes.

3. Testing Steps

   • Connect the three wires:
     • One to the main electrode and the other two to temporary electrodes.
   • Ensure that temporary electrodes do not overlap in their areas of effect.
   • Activate the testing device to obtain a reading in ohms.
   • The tester should confirm proper contact with the ground.

4. Multiple Readings

   • Move the temporary electrode closer to the main electrode and conduct another test.
   • Repeat this process to gather at least three readings.
   • Evaluate if readings are consistent and within a sensible range.
   • Average the readings:
     • If readings vary significantly, investigate the connection quality or installation.

Interpretation of Results

• Consistent readings around 100 ohms or less are acceptable.
• High readings (e.g., >400 ohms) indicate poor electrode installation.

Solutions for High Resistance Readings

1. Increase Electrode Depth

   • Use longer electrodes and couplers to install deeper.

2. Install Additional Electrodes

   • Add more electrodes spaced appropriately to ensure effective grounding.

3. Use Alternative Methods

   • Consider using a metallic grid, copper tape, or any conductive materials buried underground.
   • Utilize existing metallic structures or pipes as electrodes if applicable.

Final Considerations

• Some installations may not require earth electrodes, but testing is essential when they are present.
• The method using mains power is quicker and easier.
• Ensure safety: keep people away from electrodes during testing, especially with older equipment that may expose hazardous voltages.