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We have got electronic weighbridges in our steel plant. We have provided separate earth pits for Power supply and load cells. During rainy season and heavy lightning strikes the digital weight indicators, load cells and the computers are getting damaged. We checked and found the earth to neutral voltage is varying between 4 volts to 7 volts. I would like to have following clarifications regarding this.
1. For electronic equipment earth pits the earth to neutral voltage should not be more than 1 Volt. How to minimize this voltage?
2. When we tried to apply water to the earth pits water is not being absorbed quickly. It takes more time. How to solve this problem?
3. Can we improve the earth conductivity by adding charcoal, salt, bentonate clay etc to earth pits?
4. Our earth pits depth is 10 to 12 feet only. If we go more deeper (50 feet) can we get more conductivity?
5. If we increase the number of earth pits and by forming a network can we increase earth conductivity?
6. We have got earth resistance tester. When we checked earth resistance as per the procedure shown in the manual we got earth resistance values more than 3 ohms which is not within permissible limits. Our test electrodes were driven to a depth of one meter only. Should we drive the same more deeply( 2 meters)?
7. Once during lightning we switched off the power supply to the weigh bridges but still the load cells got damaged. We are planning to have three spike, brass lightning arrestors on each weigh bridge to protect load cells against direct lightning strokes. Will it be sufficient Or any other method can be adapted?
Pl clarify these points.
Sriram
1. For electronic equipment earth pits the earth to neutral voltage should not be more than 1 Volt. How to minimize this voltage?
2. When we tried to apply water to the earth pits water is not being absorbed quickly. It takes more time. How to solve this problem?
3. Can we improve the earth conductivity by adding charcoal, salt, bentonate clay etc to earth pits?
4. Our earth pits depth is 10 to 12 feet only. If we go more deeper (50 feet) can we get more conductivity?
5. If we increase the number of earth pits and by forming a network can we increase earth conductivity?
6. We have got earth resistance tester. When we checked earth resistance as per the procedure shown in the manual we got earth resistance values more than 3 ohms which is not within permissible limits. Our test electrodes were driven to a depth of one meter only. Should we drive the same more deeply( 2 meters)?
7. Once during lightning we switched off the power supply to the weigh bridges but still the load cells got damaged. We are planning to have three spike, brass lightning arrestors on each weigh bridge to protect load cells against direct lightning strokes. Will it be sufficient Or any other method can be adapted?
Pl clarify these points.
Sriram