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Detection Technology

Loop impedance test?

time:2020/5/7   source:华天电力  reading:321 time

Each circuit must be tested to ensure that the actual loop impedance does not exceed the specified impedance for the protective equipment. Due to the severity of contact electrical fault, it is very important to test the grounding fault loop impedance of electrical equipment and power points. Your system is valuable, and you need to maintain circuits to ensure business durability and functionality. In most homes, basic shock protection is achieved by placing a ground circuit with an automatic switch in the wiring of the house. This will quickly cut off the power supply to the docking circuit if a fault occurs and the touch voltage exceeds the acceptable limit.


According to the current national safety standards, you are required to perform loop impedance tests at your premises to ensure the safety of all guests and employees. Grounding of all electrical installations and power points must be tested to detect any faults in the circuit. A properly functioning ground circuit will allow circuit fault detection and facilitate MCB response. The technician will detect the resistance level in the ground circuit and notify you if the resistance level is wrong that the resistance must be low enough for the circuit breaker to work properly. Your wires will be inspected and tested and we will be required to conduct tests to protect your employees and your responsibilities.


Earth Resistance Tester.png


The required impedance and time values will vary depending on the type of installation (TN/TT, etc.) and the type of protection, for example, whether it is a miniature circuit breaker (MCB), plug-in fuse or reconnectable fuse, the fault current can be in a neutral or ground circuit, so the loop impedance of each circuit needs to be confirmed.


It is generally considered that, when the measured impedance of the circuit ground fault circuit is not greater than 80% of the specified relevant limit, the resistance can be expected to be low enough under ground fault conditions to reach the specified relevant limit. And the protection device automatically disconnects within the specified time.


When the TT wiring system meets the following requirements, appropriate protection can be provided against the risk of electric shock:


Ra x Ia < 50,


Where "Ra" is the sum of the resistance of the grounding rod and the protection conductor, and "Ia" is the maximum current of the protection system. The value of Ra times Ia should not be greater than 50V, that is, in the event of a ground fault, the maximum voltage that a person can touch will not exceed 50V.


The impedance of the fault circuit was tested between the conductor and the earth. To test the loop impedance, our technicians will use the ground loop impedance tester, which is plugged into a power outlet (GPO) to take readings.


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