Ground resistance testing is the key to ensure the safe and effective operation of electrical equipment. Here are five common ground resistance test methods:

1. Dc grounding resistance method
    Principle: By applying a DC voltage between the grounding body and the ground, the current flowing through the grounding body is measured and the grounding resistance is calculated.
    Equipment: Usually use DC ground resistance tester.
    Steps:
    Connect the two leads of the tester to the ground body and the ground respectively.
    Apply a direct current and measure the current flowing.
    Calculate the grounding resistance according to Ohm's law (R = U/I).

2. Ac ground resistance method
    Principle: Ground resistance is measured by applying AC voltage, usually using a 50Hz or 60Hz AC signal.
    Equipment: AC ground resistance tester.
    Steps:
    Connect the lead of the tester to the ground body and the ground.
    An AC current is applied and the current flowing through is measured.
    Calculate the grounding resistance based on the measured current and voltage.

3. Fall of Potential Method
    Principle: By setting three electrodes (A, B, C) around the grounding body, the voltage and current are measured to determine the grounding resistance.
    Equipment: three pole ground resistance tester.
    Steps:
    Connect electrode A to the ground body, electrode B as the current electrode and electrode C as the voltage electrode.
Apply a current and measure the voltage.
The ground resistance is calculated by measuring voltage and current.

4. Ground resistance measurement method
    Principle: Connect the ground resistance meter to the ground body and measure the ground resistance directly.
    Equipment: Ground resistance meter.
    Steps:
    Connect the two terminals of the ground resistance meter to the ground body and the ground respectively.
    The instrument automatically applies current and measures voltage, showing ground resistance.

5. Frequency method
    Principle: The use of signals of different frequencies to measure the grounding resistance is suitable for analyzing the characteristics of the grounding system at different frequencies.
    Equipment: Frequency response tester.
    Steps:
    Connect the tester to the ground body.
    Test signals are applied at multiple frequencies to measure response voltages and currents.
    The performance of the grounding system is analyzed by the measurement results at different frequencies.

Matters needing attention
    Before testing, ensure that the grounding body is intact and do not test in a thunderstorm.
    During the test, ensure that there is no interference from other electrical equipment to obtain accurate measurement results.
     After testing, the results should be recorded and periodically rechecked to ensure the effectiveness and safety of the grounding system.