Causes of malfunction of residual current action protector 10

1. The residual current action protector itself is defective. It should be replaced with a residual current action protector.

2. Poor grounding. If the neutral wire is repeatedly grounded, etc., the repeated grounding should be canceled.

3. Operating overvoltage. Replace it with a time-delay residual current protector or connect capacitors and resistors in parallel between contacts to suppress overvoltage.

4. Multiple large-capacity motors start together. It should be put in again and the motor should be put in sequentially.

5. Lightning overvoltage. You should try again.

6. Electromagnetic interference. If there is a magnetic device connected nearby or a high-power electrical equipment is opened and closed, the residual current action protector should be installed away from the above equipment.

7. The influence of mercury lamps and fluorescent lamp circuits. The number of mercury and fluorescent lamps in the circuit should be reduced, and the distance between the lamp and the ballast should be shortened.

8. Overload or short circuit. When the residual current action protector has both over-current protection and short-circuit protection, it will malfunction due to improper current setting of the over-current and short-circuit tripper, and the action current value of the over-current protection device should be re-tuned to match the working current.

9. Circulation influence. When two transformers are running in parallel, if each transformer has a ground wire at its neutral point, there will be a circulation current in the ground wire because the impedance of the two transformers cannot be exactly the same. If the circulation current is very large, it will cause the residual current action protector to malfunction, and a grounding wire should be removed so that the two transformers share a grounding electrode.

Regarding the "size", the long-delay current setting value of the overcurrent protection is likely to be "less than" the "maximum load current".

The "maximum load current" here usually refers to the starting current of the large motor (short-time, transient) and the "non-fault" current such as the pass-through short-circuit current. "Avoidance" refers to the "peak current time" and "peak current amplitude" that are "allowed".

Taking the electronic three-stage relay protection as an example, the three-stage combination is realized through the inverse time limit (L), fixed time limit (S) and instantaneous (I) curves, and the short-term peak current is avoided through the reasonable setting of the fixed time limit (S) section to avoid the protection malfunction.

The strength of the unit current is described by the current intensity, which is the amount of charge passing through a certain cross-section of the conductor per unit time, referred to as the current, and is represented by i.

The intensity of the current is a scalar quantity, and it is customary to specify the direction of motion of the positive charge as the direction of the current. In a conductor, the direction of the current is always in the direction of the electric field from the high potential to the low potential. In the International System of Units, the unit of current intensity is ampere (a), which is one of the seven basic units in the SI system.

Some common currents: electronic watches, incandescent bulbs 200mA, mobile phones 100mA, air conditioners 5A 10A, high voltage 200A, lightning 20000A 200000A.

greater than to prevent the protected equipment from malfunctioning at the maximum working current.

To avoid the maximum short-circuit current at the end of the protection line, it is necessary to multiply the short-circuit current at the end by a reliability coefficient greater than one (that is, the quick-break action current is greater than the maximum short-circuit current at the end of the line, and the short-circuit at the end cannot operate. ）。In this way, the malfunction of this stage of quick break protection is prevented from malfunctioning when the head of the rear line is shorted (because the short circuit at the head of the rear line is almost the same as the short circuit current at the end of the line).

Substation A is sent to substation B through line A and B, and substation B is sent to substation C through line B and C. The quick-break protection of station A is to avoid the maximum short-circuit current of line A and line B near station B, and the first end of the next line refers to the end of line B and C near station B.

Dodging is to avoid the meaning of jumping, to avoid accidents at this level and jump the upper switch.

For example, in a system, the transformer has a total outgoing circuit breaker, and then there is an outgoing switch, then the outgoing switch can be understood as the end, and the transformer outgoing circuit breaker can be understood as the first end.

For example, the quick-breaking current of the outlet switch is 200A, and the total inlet switch is only 190A, so if there is an accident, the switch at this level has not jumped, and the upper switch has jumped first, and all the outgoing switches have jumped, which is equivalent to expanding the accident. This is a skipping trip and needs to be avoided.

The installation of residual current action protector (RCD for short) in the low-voltage power grid is an effective protective measure to prevent personal electric shock, electrical fire and damage to electrical equipment. The International Electrotechnical Commission (IEC) has vigorously promoted the use of residual current action protectors in low-chain spike dust voltage power grids by formulating corresponding electrical installation regulations and electricity consumption regulations.

Second, the working principle:

The current generated by the current vector and non-zero of each phase (including the neutral wire) in the low-voltage distribution line is called the residual current. The so-called ground fault current, i.e., leakage current, is a common residual current. Residual current protection is a safety technical measure that uses residual current action protection device to prevent electrical accidents.

3. The function of residual current protection device.

1. It is used to prevent single-phase electric shock accidents caused by residual current.

2. It is used to prevent fire and equipment burning accidents caused by residual current.

3. It is used to detect and cut off all kinds of one-phase grounding faults.

4. Some residual current protection devices can also be used for overload, overvoltage, undervoltage and phase loss protection.

The structure of the residual current action protection device is mainly composed of three basic parts, namely, the detection element, the intermediate link (including the amplification element and the comparison element) and the actuator.

The reasons for the malfunction of the residual current action protector are analyzed as follows:

1. Malfunction caused by overvoltage in the opening and closing of low-voltage circuits: The overvoltage caused by operation forms a current to the ground through the capacitance to the ground on the load side. The impulse voltage of the zero-sequence current transformer is induced and causes malfunction.

In addition, overvoltage can also exert an influence on the protector from the current side and cause malfunction;

2. Malfunction caused by lightning overvoltage: lightning overvoltage will cause malfunction of the protector through the ground capacitance of wires, cables and electrical equipment;

3. Malfunction caused by residual capacitance and capacitance current: In general, there is little difference between the capacitance of the three relative grounds, so it can be considered that the sum of the current vectors formed by the three relative grounds is zero, and the protector will not act.

If the switching appliance is not synchronized with each phase or due to runout and other reasons, the capacitance to the ground is not equally charged, which will lead to the malfunction of the protector.

Answer]: B In the protection of the orange cover in direct contact with electric shock, the residual current protection device is only used as a supplementary protective measure for the basic protection measures of direct contact electric shock accidents. It can be seen from the residual current action protection mechanism that the protection does not include the protection against direct contact electric shock accidents between phase and phase, phase and n line.