The main reason for frequent tripping of leakage protectors

1. The rated current value of the leakage protector is not reasonable.

(1) The final stage leakage protection rated operating current value is set too large. The rated leakage current of the last stage leakage protection exceeds 30mA or exceeds the rated current of the electrical equipment, or the leakage protection device with delay type is selected, because the rated current of the last stage leakage protection is increased or the protection sensitivity is decreased. When a leakage fault occurs, the last stage leakage protection does not operate and the upper leakage protection device operates. The rated operating current value of the last level leakage protection should be 15mA for rural customers and 30mA for large users.

(2) The total leakage protection rated operating current setting is too small. The lower the operating current of the leakage protection device is selected, of course, the sensitivity of the switch can be improved. However, for any power supply circuit and electrical equipment, the insulation resistance cannot be infinite. When there is voltage on the line and equipment, there will always be a certain normal leakage current, while the rural low-voltage power grid has low insulation level and normal leakage current. Larger, so the rated operating current of the total leakage protector must be greater than the sum of the maximum fault leakage current and the normal leakage current value within the protection range. If the total leakage current rating is set, only the fault leakage current of the line is considered, and the normal leakage current on the distribution line after the total leakage is not considered. When the leakage fault occurs, the total leakage will be tripped. Therefore, this should be taken into consideration when installing leakage protection in rural distribution networks. In general, in order to protect the reliable operation of the power grid and ensure the selectivity of multi-level protection, the rated operating current of the upper-level leakage protection is generally chosen to be about twice the rated operating current of the lower stage. The rated operating current value of the total road protection and branch circuit protection shall be obtained by actual measurement to obtain the ground leakage current value of the line or equipment. The maximum action value of the branch protection switching shall not exceed 60 mA, and the maximum action value of the total road protection switching shall not exceed 150mA, the total leakage protection should have a delay of 0.2s, which can improve the selectivity of the last stage of the leakage protection range and the operation of the upper stage leakage protector.

2. No effective "three-level" leakage protection system has been formed within the scope of protection.

(1) The layout of the leakage protector is unreasonable. Due to the phenomenon of rural low-voltage lighting lines chaos and hangs, the wire insulation is not good and often leaks, the busy season harvesters, pumps, small electric welders, etc. are relatively random, easy to cause grounding, and have not passed the leakage protector and other reasons. In addition, in the installation, the leakage protector is not properly arranged according to the actual situation, and an effective “three-level” leakage protection system is not formed, which causes the total leakage protector to frequently trip and the power failure range is large. For these situations, the leakage protector should be reasonably arranged according to the actual situation of the rural distribution network. In some power supply range, the larger distribution transformer area needs to divide the entire distribution area into several small leakage protection ranges according to geographical range or line direction, and form secondary leakage protection in each protection range, which can improve The protection sensitivity of the second or third stage leakage protection in each protection range improves the operation rate of the second or third stage leakage protector when the fault is leaked within the protection range, and reduces the leakage of the total leakage protector. In this way, the total leakage protector of the transformer station can be mainly used as the total protection for the electric fire hazard and electrical short circuit at the power-on site, and also as the backup protection for each small leakage protection range. The rated leakage action time can be delayed by 0.2. -0.3s, which can greatly reduce the impact of surge voltage, current and electromagnetic interference on the total leakage protection, and improve the selectivity and reliability of the total leakage protection action. Only by strengthening the management of the secondary leakage protector, so that the secondary leakage protection within each leakage protection range is in an effective protection state, the frequent tripping rate of the rural total leakage protector can be greatly reduced.

(2) The user privately withdraws the leakage protector from operation. The final leakage protector is the main protection of the customer's electrical equipment. If the final leakage protector is not installed, damaged or improperly selected, it may cause the upper leakage protector to trip frequently. The final leakage protector is installed in each household and is managed by the user. It is designed to prevent personal electric shock and monitor the insulation of the user's indoor line. Due to the installation and operation of the user's end leakage protector, the power management personnel cannot effectively supervise and manage. The user leaks electricity due to their own electrical appliances, the line is aging, and the private leakage is connected to the leakage, causing the terminal leakage protection to operate frequently. The user cannot use the power normally. Therefore, the end protection is removed or even removed, causing the secondary protection to trip frequently, affecting more. Residents use electricity. In order to reduce the frequent tripping of the secondary protection, the user can only remove the secondary protection. In this way, the second and third levels of protection do not work. When one or several lines or electrical appliances leak to reach the level 1 protector action value, the entire station area has no selective frequent trips. Only when an effective two or three-level leakage protection mode is formed in each protection range can the frequent leakage of the total leakage be effectively reduced.

3. Leakage protector wiring problem

(1) The leakage protector wiring is not standardized. During installation, the neutral line does not introduce a leakage protector or it is introduced but the virtual connection causes the leakage protector control loop to be rejected without power. In the event of a leakage accident, the upper leakage protector will be activated.

(2) Neutral disconnection or poor contact, similar to non-connection, causing the midpoint potential to shift to zero potential, increasing the probability of neutral leakage and other faults, resulting in irregular leakage of the leakage protector. .

(3) When the leakage protector is installed, the screw of each terminal is not tightened. After a long time, the terminal will generate heat and oxidation, causing the insulation of the wire to be burnt, causing the line to undervoltage and tripping the leakage protector. In this case, normal power can be restored by tightening or replacing the terminals.

(4) The neutral line is repeatedly grounded. The so-called repeated grounding is the neutral line passing through the leakage protector, and is connected with the neutral line of other leakage protectors or other neutral lines without the leakage protector. When the neutral line is repeatedly grounded, under normal working conditions, the working current will not all return from the neutral line, and some of it will be grounded back to the neutral point of the power supply repeatedly. Unbalanced current will appear in the current transformer. When the current is unbalanced When the rated operating current of the leakage protector is reached, the leakage protector will trip; when the fault leakage occurs, the leakage current on the protection line may also pass through the neutral line of the current transformer to return to the neutral point of the power supply, offsetting the transformer. The leakage current prevents the transformer from detecting the fault leakage current, causing the leakage protector to refuse to operate.

(5) The working neutral line (N) behind the leakage protector is combined with the protection line (PE). If the two are combined, when a leakage fault or human body electric shock occurs, the leakage current flows back through the current transformer, and the transformer can not detect the fault leakage current, causing the leakage protector to refuse to operate.

4. Electrical equipment and power line fault leakage

The use of electrical equipment in rural low-voltage power grids is relatively harsh, maintenance and repair are limited, the quality is uneven, the insulation is good or bad, and some equipments have relatively large leakage currents, such as: the one-way switch is mistakenly connected to the zero line, so that The lamp cap is energized for a long time; the protective earthing or the zero wire of the outer casing is disconnected; the open type load switch (plastic cover brake), the insulating cover of the lamp cap and the socket, the cover is lost or broken. The same applies to the electric line, such as: the low-voltage overhead line is too low, the height to the ground, and the distance from the building do not meet the requirements of the regulations; the waste aluminum wire or wire is used as the wire; the metal casing of the electrical equipment is not grounded or the grounding is poor; Broken or aged wires are used as entry lines or plug-in lines; installation distances between broadcast lines and power lines do not meet the requirements to cause interconnection; connection lines and lead wires are aged or damaged; poles are corroded, wires are broken and joints are broken. Aging, broken porcelain bottles, etc. All of the above phenomena will cause the leakage protector to trip. If the last stage leakage protector is damaged or the last stage leakage protector is removed, it will cause frequent tripping of the upper leakage protector.