Earth Testing
In any facility that requires an earthing system, one or more of the following must be carefully considered:
It is for these reasons testing and checking of the earthing systems, particularly where there is an installation over 1000V is important.
It is recommended that earth resistivity testing be carried out every three years and Step & Touch Voltage checks be carried out more regularly.
To this end O’Hara Engineering have several pieces of specialist equipment specifically for the purpose.
.
- Limits voltage to which the system-to-earth insulation is subjected, thereby more definitely fixing the insulation rating.
- Limits the system-to-ground or system-to-frame voltage to values safe for personnel.
- Provides a relatively stable system with a minimum of transient over-voltages.
- Permits any system fault to ground to be quickly isolated.
It is for these reasons testing and checking of the earthing systems, particularly where there is an installation over 1000V is important.
It is recommended that earth resistivity testing be carried out every three years and Step & Touch Voltage checks be carried out more regularly.
To this end O’Hara Engineering have several pieces of specialist equipment specifically for the purpose.
.
Earthing & Ground Resistance Testing
This popular 4-terminal ground testing instrument is essentially used to carry out both the “Wenner” method earth resistivity test and the “Fall of Potential” Test. The test set is also capable of stake-less ground testing method using two earthing clamps.
It features:
This Clamp instrument is ideal for parallel earth networks, earth clamp is ultra-fast and safe; it not only tests earth loops quickly but also measures leakage current discharging into the earth.
It Features:
This popular 4-terminal ground testing instrument is essentially used to carry out both the “Wenner” method earth resistivity test and the “Fall of Potential” Test. The test set is also capable of stake-less ground testing method using two earthing clamps.
It features:
- 2, 3 and 4 point testing
- Stakeless (clamp-on) testing capability
- ART (Attached Rod Technique) capability
- Multiple, user selectable test frequencies
- Resistance measurement range to 200,000Ω
- Warning indicators prevent test failure
This Clamp instrument is ideal for parallel earth networks, earth clamp is ultra-fast and safe; it not only tests earth loops quickly but also measures leakage current discharging into the earth.
It Features:
- Resistance: 0.10Ω to 1,200Ω (7 cal.)
- RMS leakage current: 1mA to 30.00A (3 cal.)
- Alarm function (Programming of the alarm threshold in Ω
- 99-measurement memory capacity: recording and read-off)
- Clamping diameter: 32mm
Step & Touch Voltage
"Step voltage" is the voltage between the feet of a person standing near an energized grounded object. It is equal to the difference in voltage, given by the voltage distribution curve, between two points at different distances from the "electrode". A person could be at risk of injury during a fault simply by standing near the grounding point.
"Touch voltage" is the voltage between the energized object and the feet of a person in contact with the object. It is equal to the difference in voltage between the object and a point some distance away. The touch potential could be nearly the full voltage across the grounded object if that object is grounded at a point remote from the place where the person is in contact with it. For example, a crane that was grounded to the system neutral and that contacted an energized line would expose any person in contact with the crane or its uninsulated load line to a touch potential nearly equal to the full fault voltage.
To carry out efficient Step – Contact - Voltage Measurement O’Hara Engineering have a purpose built high current test set.
The test set can be used for testing and verification of protective earthing of power stations, substation and other power systems.
It also features:
"Step voltage" is the voltage between the feet of a person standing near an energized grounded object. It is equal to the difference in voltage, given by the voltage distribution curve, between two points at different distances from the "electrode". A person could be at risk of injury during a fault simply by standing near the grounding point.
"Touch voltage" is the voltage between the energized object and the feet of a person in contact with the object. It is equal to the difference in voltage between the object and a point some distance away. The touch potential could be nearly the full voltage across the grounded object if that object is grounded at a point remote from the place where the person is in contact with it. For example, a crane that was grounded to the system neutral and that contacted an energized line would expose any person in contact with the crane or its uninsulated load line to a touch potential nearly equal to the full fault voltage.
To carry out efficient Step – Contact - Voltage Measurement O’Hara Engineering have a purpose built high current test set.
The test set can be used for testing and verification of protective earthing of power stations, substation and other power systems.
It also features:
- High accuracy
- Excellent immunity even against changing earth currents.
- Autonomous Step Voltage meter:
- High safety