Application Of Leakage Protection - Leakage Protection, Voltage - Electrical Industry

Abstract: The typical electricity from several different places of the limitations

of the role of leakage protection, and discusses how to correctly use and install and take leakage protection with the combination of security measures such as potential connection.

Keywords: leakage Protector Role of limitations and other potential connection

0 Introduction 80 years ago, China still follows the Soviet model of a zero sequence protection for ground fault protection. Detected in this way the current zero-sequence current, which can be used to include the TN-C system, including all systems, but the protection setting value must be greater than the N line and the PEN stream of three-phase unbalanced line current harmonics current and normal leakage currents and, its value is about tens to hundreds of security. Such a large setting value can only protect the wiring insulation, and can not effectively prevent personal electric shock or grounding of electrical fires caused by arcing. Eighties, the use of the leakage protection (hereinafter referred to as RCD), it is a residual current detection are defined within the protection circuit line and neutral line current with the instantaneous value of the algebra and (including the neutral line in the three phase unbalanced current and harmonic currents), the leakage current shall be the normal ground fault current and fault current. To this end, RCD's setting value, that is, the rated operating current In, only you can escape the normal leakage current value, the value to mA, which is why very sensitive RCD can cut off the circuit ground fault protection, can also be used direct contact with the back-up anti-shock protection. This is our many years of actual use of the RCD has been proved. However, further use of the RCD, it should be noted that the existing deficiencies. Limitations on the role

1 RCD 1.1RCD elsewhere can not prevent transmission to the breakdown voltage due to electrical shock

RCD earth fault current on a very high sensitivity, able to cut off tens of milliseconds to mA total fault current, even if the contact voltage up to 220V, high-sensitivity RCD can quickly cut off people from the risk of electric shock, which is well known. But the RCD only within the scope of its ground fault protection work, but can not prevent transmission to the failure elsewhere due to electrical shock voltage.

Installed in the B household RCD, which is adjacent to a household fuse installed (RD) as a protection in the use of the process, if a household fuse section will be increased arbitrarily, and use of electrical appliances do not Transcatheter electrical equipment insulation damage caused due to fault current can not make time fuse and fuse cut off fault, then fault-voltage transmission lines through the PE to the B household electrical equipment, due to RCD does not move result, there is a caused by household B The hidden dangers of electric shock accident. Examples in the current design of the city under the premise of electricity does not exist. However, in our towns, especially in rural areas, I saw in the survey, because of the disparity in economic conditions, combined with electrical design is not standardized, this phenomenon is widespread, should arouse our attention.

1.2 Some of the sites and the equipment is not installed RCD

In some data-processing equipment, supply lines, its Power supply Anti-jamming equipment on the regular line of high-capacity filter Capacitor .

Capacitor one end of the enclosure and PE through the grounding line, its ground capacitive current is:

Calculated by the two, when C is greater than 0.22 F, the normal operation of the capacitor current will be over 15 with mA, rated operating current is 30mA In the RCD may malfunction because rated current Ino = no action (1 / 2) In = 15mA. In fact the initial capacitor charging current is much larger than this, that if the installation of RCD is that it does not malfunction, filter capacitor must be much less than 0.22 F, this is clearly unrealistic, and therefore anti-electronic data processing equipment attack can not be used RCD. International Electrotechnical Commission in IEC364-4-707 for data processing equipment, electrical safety standard developed specifically.

1.3 installed RCD some places is not allowed

Such as chest hospital operating table, is not allowed the installation of RCD's.

by: gaga

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