Earth leakage protector plays an irreplaceable role in daily life, and gradually becomes an important part of daily life. The protector can improve the unreasonable use of electric energy and improve the safety of electricity. However, in practice, there may be unscientific application of protector and problems in circuit setting. Therefore, this paper mainly discusses and analyzes the application of the protector in the low-voltage power supply line, hoping to improve the application effect of the leakage protector.

Electric power is the necessary power material for the social development at that time, and the low-voltage power supply line is directly connected with the user, so the power supply safety of the low-voltage power supply line has become the focus of the power department. Protector is the most common protection equipment in the low-voltage power supply line. Although China has accumulated a lot of experience in the promotion and application of the equipment, there are still many problems to be solved. This paper mainly discusses the application of protector in the low-voltage power supply line at that time, and puts forward some suggestions and opinions on the safety of power supply.

1 overview of leakage protector

1.1 significance of leakage protector

Under normal conditions, people call leakage protector as leakage protection switch. In civil buildings, the phenomenon of leakage is relatively common. The large current in early summer not only has a severe impact on power equipment, but also constitutes personal damage. Therefore, in the process of detailed electricity use, the need to select protector equipment is primarily to deal with the leakage problem.

1.2 equipment type

(1) According to the operation principle, the leakage protector can be divided into three types, namely pulse leakage protector, current leakage protector and voltage leakage protector. The voltage type equipment is mainly set between the transformer and the earth. In case of electric shock or leakage, the neutral point will shift, and the voltage will be generated to the earth, and then the power supply will be blocked. However, the selectivity of this method is relatively poor, so the applicable planning is relatively narrow. The principle of pulse protection equipment is that if there is an electric shock in the process of circuit transmission, the amplitude and phase of three-phase unbalanced current will be changed, which will act as a signal. However, this method has a significant disadvantage in the application process, that is, the protection dead zone is relatively large, so it has not been promoted. The detection component of current source protection equipment is mainly composed of the secondary coil of zero sequence current transformer. This kind of protector can implement hierarchical protection to achieve selective action, so it is widely used now.

(2) According to the classification of equipment sensitivity, the equipment can be divided into three sensitivity levels: high, medium and low. The operating current of high sensitivity equipment should be less than 30mA; the operating current of medium sensitivity equipment should be less than 1000mA; the operating current of low sensitivity equipment should be higher than 1000mA. According to the action mechanism, leakage protection equipment can be divided into relay type equipment and switch type equipment. In addition, the leakage protection equipment can be divided into single-stage two-wire protection equipment and two-stage three wire protection equipment; the protector can be divided into inverse time protection equipment, fast protection equipment and delay protection equipment according to the action time.

2. Application of leakage protector

2.1 operation principle of leakage protector

The application of leakage protection equipment in civil buildings is an important sign of civil buildings nowadays. The equipment is mainly for the protection of current. Try to prevent safety problems. From the composition of the protector, the most important part is the protection element of residual current. In practice, the zero sequence current and the household standard of the corresponding transformer should be taken as the primary basis. The current problems in operation and the working method of line are improved, and the iron core of current transformer is treated scientifically. Only in this way can the vector obtained in the current work be discharged to ensure personal safety. Assuming that a point equipment has a power problem, it will also form a loop through the current node setting to deal with the secondary current. At the same time, the side winding form of electromagnetic field appears, and the current is an important reason for the leakage defect. Through the leakage protection equipment, it can be measured, and the corresponding instructions can be announced to block the power supply in time.

2.2 selection of leakage protector

Among the disadvantages of low-voltage power supply lines, the problem of missing is the most frequent one, while the probability of electrical equipment touching the shell is relatively low. Therefore, the use of protector can ensure the safety of power supply system. As the most basic method, the selection and use of protector should be fully combined with the purpose and conditions of equipment use.

(1) In the low-voltage power supply line, in order to effectively prevent electric shock, we should put the leakage protection equipment at the end of the line, and also need to choose fast and high sensitive equipment. The leakage protection equipment should be installed at the distribution box of residents' residence, and the action current should be 30ma-50ma, which can effectively prevent personal electric shock and block the indoor leakage. (2) The purpose of protector equipment is to prevent electric shock, so the protector should be set in the branch line with equipment grounding, and the protector with fast and medium sensitivity should be selected. The leakage protection equipment should be installed at the switch of the low-voltage power supply incoming line (generally the distribution box or meter box) in the residential area, and the action current should be 100ma-500ma, which can meet the requirements of the building internal fire protection standard. (3) The purpose of the protector equipment is to protect the electrical equipment and power supply line, and prevent the fire caused by leakage after the defect occurs. Therefore, the leakage protection equipment should be time-delay leakage protection equipment. According to the second or third level leakage protection requirements, the delay should cooperate step by step to reduce the protection trip outage planning. Generally, cooperative equipment is carried out with 0.1s, 0.3s and 0.5s delay. (4) The protector is selected according to the power supply method. Due to different practical user terminals and different application requirements, there are certain differences in power supply methods. In the process of selecting the protector, it is necessary to select according to the practical power supply method to ensure that the protector can play a practical effect in the line. (5) In the process of selecting equipment, the protector with national certification should be selected. It is strictly forbidden to use fake and inferior products to the low-voltage power supply line, and then ensure the safety and stability of the power supply line.

3 precautions

1. Leakage protector can not replace the main protection of low voltage power supply line. There are certain limitations in the protection and protection planning of low-voltage power supply lines. For example, the "zero protection" of equipment is to connect the metal shell of electrical equipment with the zero line, and install air switch or fuse on the power side. The use of leakage protector is only under regular conditions. When the leakage current action value reaches or exceeds the given value, the circuit will be actively blocked, and then the protection work will be completed. Because the three-phase short-circuit current is basically balanced, and the zero sequence current is small, the protector can not operate normally when the three-phase short-circuit occurs. Therefore, the protector can not replace the line, which may be the main protection of the equipment. (2) The leakage protector can not replace the protective neutral or protective grounding of equipment and circuit. For electrical equipment, whether it is protective grounding or protective neutral connection, it is to ensure the personal safety of users. Therefore, we can't choose to ground or cancel the protection of neutral because of the device protector. (3) The protector can replace the equipotential combination. Equipotential combination is the way to connect the main gas pipe, water main pipe and other metal pipes. Through equipotential combination, the potential in the building can reach an equilibrium. Therefore, in buildings, especially in flammable and explosive places, the protector can not be replaced by equipotential joint. (4) Correct wiring. The key of equipment protector is to connect the lines well. It is necessary to ensure the correct wiring when using the equipment. Assuming that the protector is integral, it is necessary to pay attention to the zero line, phase line and ground line according to the standard. (5) There are many devices in the low-voltage power supply network, which are simply affected by the environment, human factors and other factors in the process of operation. Due to the long service life, the equipment will appear security risks. Therefore, it is necessary to turn on the protection and maintenance of the power supply equipment regularly to ensure the safety of the power grid. (6) Leakage protection equipment should be installed in low voltage lines. Low voltage line is directly connected with the user terminal, so its power supply safety directly affects the life and property safety of users. Although in practice, due to the different needs of users, environment and application, the requirements, types and protection conditions of low-voltage line leakage protection equipment are not the same, so it is necessary to select the appropriate equipment in combination with practice. (7) The protector may not be set under the following conditions. For example, when the equipment is used to supply power at a safe voltage, when the electrical equipment is two-layer insulation equipment, and when the electric field is not allowed to suddenly block the power supply, the leakage protector equipment can not be used.