For residential electricity to install leakage switch, there are several wrong views, leakage switch will occur wrong action, resulting in power failure, so do not install leakage switch;As long as the grounding is reliable, it can not be installed leakage switch, has been installed leakage switch, electrical equipment shell is not connected to the ground does not matter;Leakage switches have been installed, and then the electrical equipment shell and water pipes connected, how authentic......

Leakage current action protector referred to as leakage protector, also known as leakage protection switch, is mainly used in the event of equipment leakage fault and fatal danger of personal shock protection.

Leakage protection is a relatively new technology in the field of electrical safety.In the past 30 years, with the development of electronic technology, the leakage protection device with high sensitivity and fast action has obtained great development.Germany, France, the United Kingdom, the United States, Japan and other countries and even the international electrical commission have established and revised the product standards and related standards and regulations of leakage protection devices.In our country leakage protection device manufacturer is numerous, the product variety is various, the country has formulated the national standard "leakage current action protector" (gb6829-86), this standard has made the explicit stipulation to the leakage protection device characteristic, the classification, the working condition and the installment condition, the structure and the performance request, the test method, the inspection rule and so on.

Principle and composition of leakage protector

Leakage protector has high sensitivity and quick action in response to electric shock and leakage protection, which is incomparable with other protective appliances, such as fuse, automatic switch and so on.Automatic switch and fuse normally through the load current, their action protection value to avoid the normal load current to set, so their main role is to cut off the system phase short circuit fault (some automatic switch also has overload protection function).And leakage protector is the use of residual current response and action in the system, the normal operation of the system of the residual current is almost zero, so it's the set values for the action to be setting is small (typically for mA level), personal electric shock occurs when the system or equipment shell charged, appear larger residual current, leakage protector, by detecting and processing after the residual current movements in a reliable way, cut off power supply.

So how does the leakage protector play a protective role?

We know that when the electrical equipment leaks electricity, it will present abnormal current or voltage signal, and the leakage protector will prompt the action of the actuator by detecting and processing this abnormal current or voltage signal.We according to the fault current action leakage protector is called current type leakage protector, according to the fault voltage action leakage protector is called voltage type leakage protector.Due to the complex structure of voltage type leakage protector, poor stability of operation characteristics due to external interference and high manufacturing cost, it has been basically eliminated.At present, the research and application of leakage protector at home and abroad are dominated by current type leakage protector.

Current type leakage protector is a part of the zero sequence current in the circuit (usually called residual current) as the action signal, and most of the electronic components as the intermediate mechanism, high sensitivity, complete functions, so this protection device is more and more widely used.

Ii. Classification of leakage protectors

Leakage protection device can be classified according to its protection function, structural characteristics, installation mode, operation mode, pole number and line number, action sensitivity, etc., here mainly according to its protection function and use classification, general can be divided into leakage protection relay, leakage protection switch and leakage protection socket three.

1. Leakage protection relay refers to the leakage current detection and judgment function, but does not have the function of cutting off and connecting the main circuit leakage protection device.Leakage protection relay is composed of zero sequence transformer, tripping device and auxiliary contact of output signal.It can be combined with the automatic switch of high current, and can be used as the general protection of the low-voltage network or the leakage, grounding or insulation monitoring protection of the trunk line.

When there is leakage current in the main circuit, the detach tripper of the auxiliary contact and the main circuit switch is connected in series to form a primary circuit.Therefore, the auxiliary contact is connected to detach the tripping device and disconnect the air switch, ac contactor, etc., so that the switch is off and the main circuit is cut off.Auxiliary contacts can also be connected to acoustic and optical signal devices, send out leakage alarm signal, reflecting the insulation status of the line.

2. Leakage protection switch refers to the switch element that can not only turn on or off the main circuit like other circuit breakers, but also has the function of detecting and judging leakage current. When leakage or insulation damage occurs in the main circuit, the leakage protection switch can turn on or off the main circuit according to the judgment result.It can be combined with fuse and thermal relay to form a fully functional low-voltage switch element.

At present, this form of leakage protection device is the most widely used, the leakage protection switch on the market according to the functions commonly used in the following categories:

(1) it only has the power off function of leakage protection, and it must cooperate with fuse, thermal relay, overcurrent relay and other protection elements when using.

(2) overload protection function.

(3) overload and short circuit protection functions.

(4) at the same time with short circuit protection function.

(5) at the same time with short circuit, overload, leakage, overvoltage, undervoltage function.

3. Leakage protection socket refers to the power socket with leakage current detection and judgment and can cut off the circuit.Its rated current is generally below 20A, leakage action current 6 ~ 30mA, high sensitivity, often used for the protection of hand-held electric tools and mobile electrical equipment and home, school and other civilian places.

Three, the principle of selection of leakage protector

In order to regulate the correct use of leakage protection devices, the state has promulgated a series of standards and regulations, such as "provisions on the safety supervision of leakage protection devices" (Lao 'an zi (1999) no. 16) and "installation and operation of leakage protection devices (gb13955-92)".

According to these standards and regulations, we should follow the following main principles when choosing leakage protector:

1. When purchasing leakage protector, the manufacturer's products with production qualification should be purchased, and the product quality is qualified.Want to remind everybody here: the leakage current protective device that sells on the market has a lot of unqualified goods.On October 28, 2002, the general administration of quality supervision, inspection and quarantine of the People's Republic of China announced the results of sampling inspection on the quality of leakage protector products.Some can't protect the person from electric shock;Some should not trip when tripping, affecting the normal power consumption.

2. The power supply voltage, working current, leakage current and operation time and other parameters of the leakage protector should be determined according to the protection scope, personal and equipment safety and environmental requirements.

3. When the power supply adopts leakage protector for grading protection, it should meet the selectivity of upper and lower switch actions.Generally, the rated leakage current of the upper level leakage protection device is not less than the rated leakage current of the lower level leakage protection device, which can protect the safety of the person and equipment sensitively, and avoid skipping tripping, reducing the scope of accident inspection.

4. Portable electric tools (except category III), mobile household appliances (except category III), other mobile mechanical and electrical equipment, as well as electrical equipment with high risk of electric shock, must be installed with leakage protection.

5. Leakage protectors should be installed for electrical equipment in construction sites and temporary lines.This is clearly required in the technical specification for temporary electricity safety at construction site (jgj46-88).

6. Electrical leakage protection must be installed in the electrical outlet circuit in government organs, schools, enterprises and residential buildings, as well as in guest rooms of hotels, restaurants and guest houses.

7. Installed in the power lines and equipment in the water and damp, high temperature, metal occupies larger coefficient and other conductive good places, such as machinery, metallurgy, textile, electronics, food processing industries of workplaces, and the boiler room, water pump room, dining room, bathroom, hospitals and other places, you must use the leakage protector for their own protection.

8. Power distribution box with leakage protector should be selected for fixed line electrical equipment and normal production and operation places.Temporary use of small electrical equipment, should choose leakage protection plug (seat) or with leakage protection socket box.

9. Leakage protector as a supplement to direct contact protection (not as the only direct contact protection), should choose high sensitivity, rapid action type leakage protector.

Generally, the action current should not exceed 30mA and the action time should not exceed 0.1s. These two parameters ensure that the electrocuted body will not produce pathological physiological risk effect.

Rated operating current of leakage protector in bathroom, swimming pool and other places should not exceed 10mA;In the case of secondary accident caused by electric shock, the rated operating current of 6mA leakage protector should be used.

10. For the electrical equipment that is not allowed to be cut off, such as channel lighting in public places, emergency lighting, power supply for fire fighting equipment, power supply for anti-theft alarm, etc., the alarm type leakage protector should be used to connect the sound and light alarm signal, and inform the management personnel to timely deal with the fault.

Installation of leakage protector installation of leakage protector

In addition to observing the normal installation procedures for electrical equipment, the following points should also be noted:

1. Installation of leakage protector shall meet the requirements of the manufacturer's product manual.

2. Leakage protector marked with power side and load side shall not be connected backwards.If the connection is reversed, it will cause the tripping coil of the electronic leakage protector can not be cut off with the power supply and power failure, so that a long time to burn.

3. Installation of leakage protector shall not remove or abandon the original safety protection measures, leakage protector can only be used as additional protection measures in the electrical safety protection system.

4. When installing leakage protector, it is necessary to strictly distinguish between neutral wire and protective wire.When using three pole four wire type and four pole four wire type leakage protector, the neutral line should be connected with leakage protector.The neutral wire passing through the leakage protector shall not be used as the protection wire.

5. The working zero line shall not be repeatedly grounded at the load side of the leakage protector, otherwise the leakage protector cannot work normally.

6. The working zero line of branches using leakage protector can only be used as the zero line of this circuit. It is forbidden to connect with the working zero line of other circuits.

7. After the installation is complete, according to the construction of electrical engineering construction quality acceptance specification clause 3.1.6 (GB50303-2002), the "power and lighting engineering leakage protector should be" do simulation test requirements, the completion of the leakage protector testing, to ensure its sensitivity and reliability. Trial operational test button three times, loading points three times, confirm the action is correct, before officially put into use.

Operation of leakage protector

The safe operation of leakage protector depends on a set of effective management system and measures.In addition to regular maintenance, the operation characteristics of the leakage protector (including leakage operating value and operating time, leakage non-operating current value, etc.) should be tested regularly, the detection record should be made, and compared with the initial value of installation, to determine whether its quality has changed.

In use, the leakage protector shall be used in accordance with the requirements of the operation manual, and shall be checked once a month according to the provisions. That is, the test button of the leakage protector shall be operated to check whether it can be normally disconnected from the power supply.In the inspection should pay attention to the operation of the test button time should not be too long, generally inching is appropriate, the number of times should not be too much, so as not to burn out the internal components.

Leakage protection device in the use of tripping, after the inspection did not find the cause of switch action, allow a test power supply, if the tripping again, should find out the reason, find out the fault, shall not be forced to continue power supply.

Once the leakage protector is damaged and cannot be used, it should be immediately checked or replaced by a professional electrician.Electric leakage protection device, commonly known as "electric shock security device" or "life-saving device", many people believe that as long as the installation of electric leakage protection device, can eliminate the occurrence of electric shock casualties.In fact, a lot of reasons can cause the leakage protection device to refuse to jump, thus unable to protect the role.Therefore, it is of great importance to fully analyze the causes of resistance of electric leakage protector and correct the mistakes in people's thinking and understanding to prevent the occurrence of electric shock accidents.

5.1 the leakage protector is in abnormal operation state and cannot play a protective role

5.1.1 internal fault or damage of leakage protector

Although the power sector of the leakage protection device management has developed the relevant system, for example: the rural electricity leakage protection device, generally requires rural electricians to check by cycle jump, but even so, still can not avoid the leakage protection device (especially the rural grid three-phase leakage protection device) internal fault may occur at any time.If not timely detection and troubleshooting, leakage protector will not play the due protection.In order to avoid unnecessary legal liability caused by accidents on the lines of the rural power grid, it is suggested that the responsibility of the electric leakage protector of the rural power grid should be checked frequently and recorded in the test run.

5.1.2 artificial shutdown of leakage protector

As a result of some reason, leakage protector by mistake move or trip frequently, individual user coveting convenience, without authorization will leakage protector out of operation, make leakage protector play less than due protection.The way to exit the operation of the leakage protector, in addition to the common way of unlocking the incoming and outgoing lines of the leakage protector and connecting them directly, there is a more concealed and worse way to loosen the wiring screw on the secondary side of the current coil inside the leakage protector.

5.1.3 wiring error of leakage protector

Before installing the leakage protector, it is necessary to understand its nameplate and operating instructions in detail, and adopt different wiring methods according to different field conditions.After installation, the following inspection must be carried out :(1) with load points, close the switch three times, do not mistakenly operate;(2) use the test button to test three times, and it should be correctly broken;(3) the grounding test of the test resistance of each phase shall be conducted three times, and it shall operate correctly.Only after all the above inspection items are qualified, the wiring of leakage protector can be judged to be correct.

Leakage protector installed in TN system, it is important to pay special attention to the distinction between neutral and protective line, three phase four wire type or four pole leakage protector in the neutral wire should be connected to the leakage protector, after leakage protector of neutral line shall not be used as protection, shall not repeat grounding, or pick up equipment exposed conductive parts, protection line shall not be connected to the leakage protector.

5.2 the leakage protector is in normal operation and cannot play a protective role

5.2.1 in TT system, the neutral point grounding wire of transformer is disconnected, single-phase electric shock accident occurs, and the leakage protector does not work.

When the neutral grounding wire 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 pressing the "trial-trip" button, the trial-trip is normal, but the leakage protector will refuse to trip when relatively shorting (i.e., single-phase electric shock accident).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 wire of the neutral point of the transformer is disconnected, the short-circuit current cannot be returned to the distribution transformer through the protected line and earth flow, so the leakage protector cannot work.

The above situation should especially cause the attention of agricultural electricity management personnel, because many agricultural electricity management personnel always think: as long as the leakage protector test jump normal, can play a protective role.Especially in recent years transformer grounding wire stolen shear situation is quite serious, so should strengthen inspection, take extended grounding bar and other technical means.In the case of normal tripping of leakage protector, grounding resistance should be used for grounding test.

5.2.2 when phase zero and phase shock occurs, the leakage protector will not work

When the body contact phase zero (or phase), the body resistance is equivalent to a load, while the people are standing on the earth, but through the body electric shock after the electricity flows through the shunt, the vast majority of the phase zero (or phase) wire forming circuit, and get an electric shock electricity flows through the land back to the distribution transformer is few, the electric current cannot make leakage protector action.

Gb6829-86 "leakage current action protector" stipulates: "leakage protector can not protect the risk of electric shock caused by simultaneous contact with two wires of the protected circuit".

5.2.3 the leakage protector jumps over the grade and cannot be operated

In the implementation of graded protection, if the leakage protector only action current level difference, but no action time level difference, it is easy to cause the phenomenon of over the gate.The harm of stepping over the gate is to enlarge the scope of power failure.

5.2.4 the neutral fuse fuse of the knife brake before the leakage protector is fused, and the leakage protector does not work

If the leakage protector is installed together with the knife brake, the power supply wire enters the knife brake first, then enters the protection switch, when the knife brake neutral wire fuse is broken, it will make the leakage protector "own circuit" to push the working power supply, but cannot operate.At this point, if the phase line fuse is not refreshed, although all kinds of electrical appliances have stopped working, but the following line is still charged, the formation of "illusion" power failure.When users use electrical appliances or check "false" power failure, leakage protector due to the loss of electricity and refuse to move and prone to electric shock accident.In order to give full play to the role of the leakage protector, it is suggested that the users who use this kind of wiring mode should remove the neutral wire fuse in the knife brake and use the same specification of wire for replacement.

Leakage protection is not "life", a lot of reasons can cause its refuse to jump, the vast number of farm workers and users should have a clear understanding, to prevent temporary carelessness, causing the occurrence of electric shock casualties.

And the residential electricity should not be installed leakage switch, there are several wrong views, leakage switch will occur wrong action, resulting in power failure, so do not install leakage switch;As long as the grounding is reliable, it can not be installed leakage switch, has been installed leakage switch, electrical equipment shell is not connected to the ground does not matter;Leakage switches have been installed, and then the electrical equipment shell and water pipes connected, how tunnel;Leakage switch has been installed, electrical equipment is also grounded, the bathroom with the bath need not do local equipotential connection.The above errors are analyzed one by one below.

1. The tripping of leakage switch can be divided into normal tripping and abnormal tripping.

Normal tripping indicates that if the rated operating current of the leakage switch is 30MA, the leakage switch will trip if there is more than 25MA leakage current in the load.Since the current of 25MA is safe to pass through the human body, no electric shock death will occur;Similarly, there is no danger to the circuit or electrical equipment, and the work of electrical equipment will not produce abnormal phenomenon.In this case, without analysis, mistakenly thought that the quality of the leakage switch, arbitrarily remove the leakage switch, is extremely wrong, remove the leakage switch, see the electrical equipment working normally, that is right, this is a dangerous practice.

Abnormal trip is caused by the unqualified quality of the leakage switch itself, which is divided into two categories;They don't close and sometimes trip for no reason.In the case of leakage switch connected to the power supply and not connected with the load, if not closed, must be the quality of leakage switch, do not repair their own, because the repair must carry out technical performance test test can be set into use, use is not safe without testing equipment.The second type is the occasional trip, especially in the middle of the night or when no one at home trip, this trip shows the poor anti-interference performance of the leakage switch.Abnormal trip of the leakage switch should be removed, change a good leakage switch.

If the leakage current of normal tripping fluctuates at 25MA, the phenomenon is similar to occasional tripping, which is often caused by the insulation aging of the wire, that is, when the environment is wet, when the environment is dry and not tripping.A reliable way to distinguish such normal trips from occasional trips is to measure the insulation resistance of circuits and electrical equipment.Standard regulation, each wire insulation resistance shall be not less than 0.5 M Ω, electrical equipment insulation resistance is generally greater than 0.5 M Ω.If the leakage switch after the load, the total measuring insulation resistance is less than 8.8 K Ω Ω (220 v / 25 ma = 8.8 K), so normal trip will occur.

It is wrong to regard normal tripping as leakage switch and not install leakage switch.Because once the leakage expands beyond 30MA, there is a risk of electric shock.

2. Grounding of electrical equipment is the basic measure of electricity safety.However, even if the grounding resistance of the grounding electrode meets the requirements, it cannot guarantee the reliable grounding of the electrical equipment.Residential electrical equipment within the earth wire is not more than 2.5 was, from the main grounding, grounding, grounding feeder to electrical equipment, there is a lot of points, with a little connection is unreliable or fracture, especially the grounding socket pile head poor contact, can cause ground unreliable, so can't guarantee the electrical equipment grounding is absolutely reliable, reliable grounding, or only guarantee measurement inspection can guarantee always reliable.Therefore, the installation of leakage switch is a very effective way to increase the safety of electricity.

3. The houses built in the past did not pay much attention to the docking place. Although many families have a three-hole socket, they only have two wires and lack the grounding wire.In order to use electricity safely, each house installs leakage switch.Installed after the leakage switch, once appear, leakage, switch trip immediately, to avoid the risk of electric shock, in this case, some people think that the earth wire increase too much trouble, with leakage switch is safe, can not increase the ground wire, this view is wrong, because the leakage switch also has the possibility of failure, with the ground wire, can increase the degree of safety.

Up to now, there are still many families to water pipes and do grounding wire, which is not reliable, one is the grounding resistance can not be guaranteed, the second is the fault voltage easily spread along the water pipe.Shanghai television once reported that a shikumen house, the tap hemp electricity is an example;In an analysis of an electrical accident reported in electric world magazine, an elderly woman died after being shocked while touching a water tap from which her electricity was transmitted.Grounding construction is an important concealed works, must be constructed by professional teams, supervision and acceptance.Grounding and installation of leakage switch, not once and for all, the grounding resistance of the grounding device should be retested once a year, the connection of the grounding wire is reliable, also must be often checked.

5. Gb50096-1999 "code for residential facilities" 6.5.2 stipulates that local equipotential connection should be done in the toilet.Under the condition of complete soaking, such as soaking in the bathtub, the resistance of human body can be ignored. In this case, the dangerous voltage of electric shock is not regulated in China. In the notes of IEC, the voltage shall not exceed 12V, and in Japan, it shall not exceed 2.5v.If you don't make equipotential connection, so the risk of low voltage is extremely easily, between the grounding line and neutral line voltage is often more than 10 v, if light neutral line and water pipe short circuit, floodlight is still normal work, people sitting in the bathtub, bathtub drain pipe is at ground potential, wash bath faucets in its hands, at this time will be electric shock.

Equipotential connection is to connect all the metal bodies in the toilet (including water pipes, pit pipes, downpipes, metal towel racks, etc.) into one, and connect with the ground wire.

The electrical equipment inside toilet should have leakage protection, want to have reliable ground, make equal potential connection even.

Finally, two points need to be pointed out:

1. When single-phase electric shock accident occurs (this kind of accident has the highest probability in electric shock accident), that is, when the load side of the leakage protector contacts a phase line (fire line), it can play a very good protective effect.If the human body to the ground insulation, this time touching a phase line a zero line, leakage protector can not play a protective role.

2. As the role of leakage protector is to prevent problems in the future, when the circuit works normally, it can not reflect its importance, often not easy to attract people's attention.Some people in the leakage protector action is not carefully to find the cause, but the leakage protector short connection or removal, which is extremely dangerous, is absolutely not allowed.