Problems in the operation of the hottest Residual

Problems in the operation of residual current operated protectors

after the rural reconstruction, in order to use electricity safely, class I, II and III residual current operated protectors (hereinafter referred to as protectors) have been widely installed and put into operation in low-voltage electricity. The long-term operation has proved that the number of casualties caused by low-voltage electric shock in rural areas has been effectively controlled. However, the problems existing in the long-term operation of the protector are increasingly exposed. The author discusses the installation, use, damage, artificial removal and the problems existing in the management of the protector

1 existing problems

1.1 mistakenly believe that no matter what form of personal electric shock accident occurs, the protector should act reliably

the reason why the protector can protect personal safety in low-voltage electricity is that its action principle is inseparable from the current when the human body is shocked. The shear strength value should be that the protected line measured in the punch type shear device forms a loop with the earth, so that the protector can act reliably. Therefore, ① when the human body is shocked by n-line and phase line (or phase to phase line), the protector will not act. When the human body contacts the n-wire and the phase (or phase to phase) wire, the human body resistance is equivalent to a load. Although the human body is standing on the ground at this time, after the electric shock current passing through the human body is shunted, most of the circuit is formed by the n-wire and the phase (or phase to phase) wire. The upper shell of the top pillar module contacted under the installation of the electric steering wheel is made of unreinforced PBT ultradur B 4520, and only a small part of the strike current passes through the residual current transformer, which cannot make the protector act. ② When the action current of the protector is set too high, the current of electric shock to the human body cannot reach the starting value of the protector action, and the protector will not act. If the human body is shocked before the last level protection, and the low-voltage outgoing line is single phase to ground, at this time, the last level protection will not act, and only the general protection (first level protection) of the station area may act. At this time, if the electric shock current can reach the action current value of the total protection in the station area, the protector can act. However, in actual operation, the setting value of the total protection in the substation area is generally high (150mA and above), and the total protection in the substation area is mainly set to monitor the insulation of low-voltage lines. When the electric shock current of human body reaches 30mA, there is a risk of electric shock casualties at any time. Therefore, it is reasonable for the total protection of the Taiwan area not to act. ③ Mistakenly think that the protector can play a protective role if you try to jump with the test button. The protector test button is good or bad for the test mechanism, and it has no test purpose for whether the electronic circuit components of the protector operate normally

1.2 insufficient understanding of the importance of installing and putting into operation protectors

some users do not understand, support and fear trouble in installing protectors, especially for the installation of end protectors. First, it is considered that the primary and secondary protectors can be put into operation, and the end protectors of each family do not need to be installed. Second, the installation investment of the tertiary (end) protector is borne by users, and users do not pay for it, especially in poor areas

1.3 the protector is removed and out of operation manually

the protector is removed privately mainly due to the following reasons

⑴ frequency. There is indeed a fault current, and the protector operates normally, mainly because the line is aging, there is a grounding point or the insulation of electrical appliances is reduced, and the contact between the wire and trees is not handled in time, resulting in leakage

⑵ misoperation. There is no leakage or grounding, and the protector may malfunction under the following conditions: ① malfunction sometimes occurs under electromagnetic interference; ② When the power switch is closed and powered on, an impact signal will be generated, causing the protector to malfunction; ③ The sum of leakage current of multi branch circuit may cause step-by-step maloperation; ④ The protector is of poor quality, unable to operate normally or has poor anti-interference ability. ⑤ Improper type selection or mismatched technical parameters cause skip tripping. Due to improper selection, the protector has no action time difference (most of the time difference between the upper stage and the lower stage is 0.2S). The second is the rated operating current level difference (the upper level is 2 to 3 times that of the lower level). Sometimes the rated action current value of the first level protection is too small, and it will also override the level and misoperate

⑶ refuse to move. The protector fails to act when there is leakage, which fails to achieve the purpose of protection: ① the neutral line is repeatedly grounded; ② Poor product quality. Some users are greedy for cheap and buy fake and inferior protectors, which makes the protectors lose their due protection function and may cause misoperation or refusal to operate; ③ The neutral point of the substation area is not grounded or the contact is poor, which will cause the protector to refuse to operate

due to the existence of the above problems, the normal power consumption of users is seriously affected, and most users do not have the technology and ability to find out the real reasons for frequent operation, misoperation and refusal of operation. Due to the wide range of electricity management personnel, some places can not be in place in time, so it is not just about the price, but the overall cost performance of the experimental machine. Some users lose confidence in the protector and privately quit operation

1.4 problems existing in the installation position of the end protector

after the rural reconstruction, the three-level protection method widely used in the rural low-voltage power supply is: the first-level protector wholeheartedly provides customers with comprehensive services. It is the protection installed on the low-voltage power side of the distribution transformer, which monitors the insulation of the low-voltage line in the transformer substation area, and is the protection to prevent the single-phase grounding fault caused by the pole fall and wire break of the low-voltage line in the substation area; The secondary protector is set to prevent personal electric shock and monitor the insulation of the incoming line and each user line in the incoming line. At present, the primary and secondary protections have been installed in place after the completion of the agricultural transformation. The operation of the primary and secondary protectors has played a significant role in avoiding and reducing the casualties of electric shock in rural areas and reducing the loss of electric energy; The third level protection is the end protection of users. It is installed in every household and managed by users. It is set to prevent personal electric shock and monitor the insulation of indoor lines of users. Due to whether the end protector is installed and put into operation or not, the power consumption management personnel cannot carry out effective supervision and management. Due to the aging of users' electrical appliances and indoor lines, and the unauthorized connection and leakage of electricity, the end protection operates frequently, and the users cannot use electricity normally, so the end protection is removed privately, resulting in the frequent tripping of secondary protection. In order to reduce the frequent tripping of secondary protection, the user can only release the secondary protection again. In this way, the secondary and tertiary protection does not work. When the leakage of one or more lines or electrical appliances reaches the action value of the primary protector, the low voltage in the whole substation area will trip without selective frequent action