Today, the measurement of grounding resistance must be performed in order to make sure that it fully complies with all the requirements of the PUE, as well as PTEEP. All measurements that will be carried out in an electrical installation with a solidly grounded neutral (voltage that will be below 1000 Volts) must necessarily comply with the following standards.
The value that you get after taking measurements should not exceed the 8, 4 and 2 Ohm mark at 220, 380 and 660 Volts. If an insulated neutral is used in electrical installations, then the resistance of the ground loop will correspond to clause 1.7.104 of the PUE and it will be calculated according to the formula Rz * Iz< 50 В. В этой статье мы рассмотрим основные методики замеров контура, а также приборы, которые необходимо для этого использовать.
Overview of techniques
To carry out a variety of measuring work, you may need to artificially assemble an electrical circuit where the current will flow through the tested ground electrode system, as well as the current electrode. Also, a potential electrode will be used in a similar scheme. Its main purpose will be considered to measure the voltage drop during the flow of electric current through the ground electrode. The potential electrode must be placed equally far from the current electrode and the tested ground electrode, in the zone where the zero potential will be located.
To measure resistance using the ammeter-voltmeter method, you will need to use Ohm's law. In most cases, this method will need to be used for a private house. You can also use a welding transformer to obtain the required measuring current. You can also use other transformers where the secondary winding will not be connected to the primary.
Use of special devices
Even if you have a functional multimeter at home, then in this case you must remember that it is not suitable for measuring the resistance of the ground loop. To measure the resistance of the ground loop with your own hands, you will need to use the following analogs:
- MC-08.
- M-416.
- AES-2016.
- F4103-M1.
Now let's look at how to measure resistance with the M-416 device. Before using the device, you must make sure that it has power. You will need to place the finished device on a flat horizontal surface. Now you need to calibrate this instrument. The device must be put in the "control" position and the red button must be held down, and the value must be set to the "zero" mode. To take measurements, you must use a three-clamp circuit. The auxiliary rod must be driven at least half a meter into the ground. All wires, you need to connect according to the diagram below.
The switch, which is located on the device, will need to be moved to the "X1" position. Then you can hold down the handle and turn the arrow until it is in the "zero" position. The resulting result, you need to multiply by the previously obtained factor. This will be your desired value. In the video below, you can see how to measure ground resistance with a device.
If necessary, you can also use modern devices that greatly simplify all the work of taking measurements. For example, to measure earth resistance, you can use the MRU-MRU200, MRU120, MRU105 instruments.
Clamp work
The resistance of the earth loop can also be measured with a current clamp. Their advantage will be that there is no need to disconnect the grounding device and use auxiliary electrodes. Thanks to this, you will have a wonderful opportunity to quickly conduct the measurement process. Now let's consider. An alternating current will flow through the grounding conductor under the influence of the primary winding of the transformer, which will be located in the measuring head of the clamp. To calculate the resistance value, it is necessary to divide the value of the EMF of the secondary winding by the value of the current measured by the clamp.
What should be the frequency of measurements?
Resistance measurements, as well as partial excavation of the soil, must be carried out regularly. In most cases, it is necessary to follow the schedule that is drawn up in the company or that you have drawn up yourself. Many people who live in a private home neglect protection, but this should not be done.
If you are planning to perform a check, then remember that it is best to complete this task during the dry season. This will give you a great opportunity to achieve accurate results. If the test is carried out in the fall or spring, then remember that due to the wet ground, the current can spread and therefore the readings will be inaccurate.
In order to measure ground resistance by specialists, you will need to contact the appropriate company. After completing the check, you will have the opportunity to receive a protocol, which will indicate all the necessary data on carrying out such a check. Many laboratories indicate in this document the place of work, the purpose of the ground electrode, the seasonal correction factor. Below you can see a sample of such a protocol.
Below you can also see a video that will tell you how to measure the grounding resistance of an overhead line support.
Now you know all the techniques for measuring grounding resistance at home. If you do not have certain skills, then in this case it is best to turn to real professionals.