Leakage protector rejection reason and analysis - Database & Sql Blog Articles

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Leakage protectors, commonly known as "electric shock protectors" or "life-saving devices", many people believe that as long as the installation of leakage protectors, you can eliminate the occurrence of electric shock and casualties. In fact, many reasons can cause the leakage protector to refuse to jump, thus failing to protect. Therefore, it is extremely important to fully analyze the cause of the leakage of the leakage protector and correct the mistakes in people's thinking and understanding, and to prevent the occurrence of electric shock and casualties.
1 The leakage protector is in an abnormal operating state and cannot be protected.

1.1 Leakage protector internal fault or damage

Although the power sector has formulated relevant systems for the management of leakage protectors, for example, for rural network leakage protectors, rural electricians are generally required to check and test on a periodic basis, but even then, leakage protectors cannot be avoided (especially the rural network). Three-phase leakage protector) The possibility of internal failure at any time. If the fault is not detected and eliminated in time, the leakage protector will not provide the protection it deserves. In order to avoid unnecessary legal liability when an accident occurs on the agricultural network line, it is recommended that the responsibility of the leakage protection device of the agricultural network should be checked, and the test run record should be made.

1.2 Leakage protector artificially exited

For some reason, the leakage protector is malfunctioning or tripping frequently. Individual users arbitrarily withdraw the leakage protector from operation in order to facilitate the convenience of the map, so that the leakage protector does not have the protection function as it should. The method of exiting the leakage protector operates in addition to the common intrusion of the leakage line of the leakage protector, and directly attaches it, and there is a more concealed and more severe method of loosening the secondary side of the internal current coil of the leakage protector. Wiring screw.

1.3 Leakage protector wiring error

Before installing the leakage protector, it is necessary to know the nameplate and the instruction manual in detail, and adopt different wiring methods according to the actual situation of the site. After installation, it is necessary to carry out the following inspections: (1) with load division and closing switch three times, no mistakes; (2) three times with the test button, it should be able to break correctly; (3) test the grounding test with three phases for each phase Should act correctly. Only after the above inspection items are all qualified can the electric leakage protector be correctly wired.

When the leakage protector is installed in the TN system, special attention should be paid to strictly distinguish the neutral line and the protection line. The neutral line of the three-phase four-wire or four-pole leakage protector should be connected to the leakage protector through the leakage protector. The neutral line shall not be used as a protection line. It shall not be grounded or connected to the exposed conductive part of the equipment. The protection line shall not be connected to the leakage protector.

2 The leakage protector is in normal operation and cannot be protected.

2.1 In the TT system, the neutral point of the transformer is disconnected, a single-phase electric shock occurs, and the leakage protector does not operate.

When the neutral point of the transformer in the TT system is disconnected, the total leakage protector installed on the load side of the transformer will reproduce the following situation: when the test jump button is pressed, the test jump is normal, but it is relatively short-circuited (ie In case of single-phase electric shock accident, the leakage protector refuses to jump. The reason for this situation is that the test jump button can only detect whether the leakage protector itself is normal, and after the grounding line of the neutral point of the transformer is disconnected, the short-circuit current cannot flow back to the distribution transformer through the protected line and the earth. Therefore, the leakage protector cannot operate.

The above situation should be especially noticed by the agricultural power management personnel, because many agricultural power management personnel have always believed that as long as the leakage protector is normally tested, it can play a protective role. Especially in recent years, the grounding of the transformer ground wire is quite serious. Therefore, it is necessary to strengthen inspections and adopt technical means such as extending the grounding rod. In the case where the leakage protector is normally tested, the grounding resistance is also used for the grounding test.

2.2 When the phase is zero and the phase is in contact with the electric shock, the leakage protector does not move.

When the human body touches the phase zero (or phase phase), the body resistance is equivalent to a load, although the person is standing on the ground at this time, but after the human body's electric shock current is shunted, most of the phase is zero (or phase). The wires form a loop, and the electric current is only a small part of the ground return-to-distribution transformer, and this current cannot operate the leakage protector.

GB6829-86 "Leakage current action protector" stipulates: "The leakage protector shall not protect against the electric shock caused by the two wires being protected at the same time."

2.3 Leakage protector trips over the stage, unable to move

When implementing the grading protection, if the leakage protector has only the operating current level difference and there is no operating time difference, it is easy to cause the over-level crossing. The danger of crossing the gate is to expand the scope of the power outage.

2.4 The neutral valve fuse fuse in front of the leakage protector is blown, and the leakage protector does not operate.

If the leakage protector is installed together with the knife gate, the power supply line enters the knife gate first, and then enters the protection switch. When the neutral wire fuse of the knife gate is blown, the leakage protector "self circuit" pushes the working power supply, and cannot operate. At this time, if the fuse of the phase line is not rejuvenated, although all kinds of electrical appliances have stopped working, the line below the knife gate is still charged, forming an "illusion" power outage. When the user uses the electrical appliance or checks for "illusion" power failure, the leakage protector is highly susceptible to electric shock accidents due to loss of power. In order to make the leakage protector fully play its due role, users of this type of wiring are recommended to remove the neutral wire fuse in the knife gate and replace it with the same specification wire.

Leakage protectors are not “life-saving devices”. Many reasons can cause them to refuse to jump. The majority of agricultural power workers and users must have a clear understanding to prevent accidents caused by electric shock and casualties.