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Ground resistance continuity test

time:2020/8/8   source:华天电力  reading:932 time

All Class I equipment undergoes this specific test to ensure that the connection between the grounding plug in the plug and the equipment housing is satisfactory.

The grounding of the equipment means that it is safer to use, because the possibility of electric shock is greatly reduced, and combining these with standard insulation features even further improves the safety of the equipment.

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This special test is also often referred to as a ground bond or ground resistance test, but they all measure the same thing.

carry out testing

In order to perform a ground continuity test, the power plug of the equipment must be inserted into the PAT test equipment, and the test lead must be connected to a suitable ground point on the equipment.

For example, if you take a kettle, then this test will be performed by inserting the kettle directly into the PAT tester, and then clamp the test leads to the inner metal inside the kettle.

In order to pass the test, the reading you get from the PAT tester must show that the measured resistance is less than 0.1Ω + the resistance of the power cable.

Ground point on equipment

Of course, a problem that needs to be solved when conducting this test is whether there is a suitable grounding point on the device.

On many electrical appliances, there are metal points on the outside of the appliance, suitable for grounding. However, not every metal point on the device is directly connected to ground; if the reading fails, it is important to repeat the test on another potential ground point to ensure that the connection is incorrect.

Rusty metal can also play a role in testing-try to connect clean metal as much as possible, or you can use the teeth of the alligator clip to scrape off some rust.

When testing a "flat-bottomed kettle" where the heating element itself is not exposed, it usually always passes the test. Instead, the ground pin is usually tested on the side of the detachable base. You should be able to get earth connection there.

If testing a PC, try to place the ground connection as close as possible to the power source, which is usually located in the upper right corner. This is where the head of IEC enters the equipment.

Level 1 "no grounding"

These devices are usually limited to paper shredders, laptop/monitor power supplies and desktop fans. There is no place to connect the clip of your test machine.

The approach to these appliances is usually to omit the ground bond test. After all, if no one, including you, can touch metal products, then users cannot touch it either. Therefore, they will not be impacted by contact with exposed metal products that become charged due to insulation breakdown.

Ground test current

Two types of ground bonds are generally used to test current.

The low current is usually in the range of 100 to 200 mA, and the high test current is in the range of 10 amperes or 25 amperes.

The ground connection test transfers the test current along the ground cable from the pin of the plug to the body of the device. Then, the device tester measures the resistance of the connection.

If the connection is rusty, non-existent, or corroded, the ground resistance reading will increase.

In layman's terms, this is a bit like testing a rope, the ground wire is a rope. By adding weight (current) to the rope, you are testing that if a failure occurs (such as the insulation breakdown of the device), the ground wire will be able to withstand the 25amp test current applied to it.

Many PAT testers available today are battery-powered and can only perform 100 or 200 mA tests in accordance with practical specifications.

The main power supply PAT tester performs 10 amp or 25 amp test. It's like testing a rope or cable.

IT equipment should be tested at 100 or 200 mA, while heaters, washing machines, and other high-power devices should ideally be tested at 25 amps if your testers are capable of doing so.

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