Leakage protector design and configuration

Update date:2018-07-06 Source:MAXGE

The leakage protector is composed of a zero-sequence current transformer, a tripping mechanism, a leakage release, a main switch, and an experimental button. The ground fault current of the protected device acts on the leakage release of the leakage protector, and when the current exceeds the predetermined value, the switch trips immediately, thereby cutting off the fault circuit and achieving the protection function.

Leakage protector

The leakage current values of electrical lines and equipment and the leakage leakage current characteristics and time characteristics of the cascade installation are as follows:

(1) When used in a single electrical equipment, the operating current shall not be less than 4 times the measured leakage current of normal operation;

(2) The operating current of the leakage protector of the distribution line shall not be less than 2.5 times of the measured leakage current of the normal operation, and shall also satisfy the leakage current of the normal operation of one of the electrical equipment with the largest leakage current;

(3) When used for network protection, the operating current should be no less than 2 times the measured leakage current;

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(4) The rated operating current of the leakage protector should be left with a certain margin to accommodate the increase in current leakage caused by the reduction of insulation resistance of the circuit, the increase of power equipment and seasonal changes.

A basic requirement of electrical safety is to minimize the number of poles and the number of contacts of the switchgear and the connection point of the line. The active connection such as the switch contact and the fixed connection of the line may be the cause of the accident due to various reasons. The neutral line in the three-phase circuit is more dangerous than the neutral line. This is because the device is still running when the neutral line is poorly conductive. The hidden danger is not easy to be found. When the three-phase load is seriously unbalanced, the three-phase voltage will also be seriously unbalanced. Burning out single-phase equipment, so limit the contact on the neutral line as much as possible.

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Leakage protector only provides indirect contact protection for single-phase 220V lines. At the same time, there are hidden dangers caused by mechanical wear, poor contact, short quality and short life, which can not become a reliable protection measure. Therefore, equipotential bonding should be implemented to effectively eliminate the occurrence of arcing and sparking between electrical circuits or equipment that leaks and metal components with low potential, that is, to eliminate the possibility of fire caused by leakage voltage.

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