Time: OCTOBER 2021 |
Source: Acrel
Abstract: In recent years, the rate of installation, commissioning and and operation qualification rate of total protectors have gradually increased,and the installation rate and commissioning rate of household leakage protectors in rural households have also been widely popularized. By paying close attention to the management of residual current-operated protectors, results have been achieved. By the general installation of protectors, the accidents of electric shock and casualties of rural electric shocks have been greatly reduced, the reliability of rural power supply has been significantly improved, the health of rural power equipment has improved significantly, and Rural low-voltage line loss has dropped significantly.
Keywords: village; leakage protector; electric shock
0.Overview
In the low-voltage power distribution system, direct contact electric shock protection adopts a residual current operated protector with a rated operating current of no more than 30mA and no delay action, as a supplementary protection measure for direct contact electric shock protection, so that it can provide backup protection when the basic protection measure for direct contact with electric shock fails.This supplementary protection is an effective protection measure under special circumstances. Therefore, it is clearly stipulated in GB13955-2005 "Residual Current Protection Device Installation and Operation" that,a residual current protection device must be installed in the direct contact and click protection.
1.Use residual current action protector to ensure safety
Residual current protection devices in low-voltage systems, electrical equipment insulation fault grounding short-circuit, the current value causing indirect electric shock is generally very small, not enough to make the system's over-current protection device automatically cut off the power supply. The residual current operated protector operates on the residual current formed in the event of a fault, and its operating value has nothing to do with the load current and is only in the milliampere level. Under specified conditions, when the operating current value of the residual current-operated protector reaches or exceeds the given current value, it can automatically cut off the power supply. It is usually used to automatically cut off the power supply in the event of a fault. Therefore, the residual current operated protector can be used as direct contact electric shock protection, indirect contact electric shock protection, ground fault protection, and electrical fire protection.
2.Application in rural power safety management
1)Ensure the safety of people's lives and property and promote social harmony. When the level of electricity consumption in rural areas is not high, farmers’ awareness of safe electricity use has not been strengthened, and common sense of safety has not been popularized, residual current action protectors have become an important technical means to ensure the safety of people’s lives and properties, and the use of residual current action protection has been promoted. It is also an effective measure for county-level power supply companies to strengthen the safety management of rural power and ensure the safety of people’s lives and property. Therefore, it is particularly important to strengthen the management of residual current operated protectors to ensure their correct action and reliable operation.
2)Promote loss reduction and efficiency enhancement, which is conducive to the improvement of the efficiency of power supply enterprises.The reliable operation of the protector plays an important role in reducing loss and increasing efficiency.Through time comparison, some stations with high low-voltage line loss are those where the protector trips frequently or the protector does not operate normally. Due to the large leakage current of the line, the power loss is caused, which will reduce the loss and increase the efficiency of the power supply company. Increased a certain degree of difficulty.
3)Promote the elimination of potential safety hazards and improve the health of equipment.To make the protector operate reliably, eliminating the hidden dangers of the equipment is the key. The first is to completely eliminate unprotected blind spots, so that all rural residents in the world can reach the protection range of the total protector and seamlessly cover. The second is to reduce power outages. In some areas with many users and high power consumption, install secondary protection The device can improve the reliability of power supply and the operating rate of the protector, and find and deal with hidden safety hazards in time; the second is to continuously improve the operating reliability of the protector, and completely separate all the transformer neutral ground wires from the common wire of the transformer shell grounding , To ensure the stable operation of the protector; the third is to strengthen the renovation of the power distribution area to improve the health of the equipment.
4)Conducive to the professional management and construction of power supply stations. After installing the leakage protector, the fault points can be reduced to facilitate targeted investigation. Most farmers can deal with the fault, and the station administrators are also free from the tedious work, which is conducive to the professional management of the power supply station and makes the station area easier. The administrator puts more energy on marketing management and quality service.
3. Product overview
The common phase-to-phase short circuit can generate a large current, which can be protected by a switch. However, the current leakage caused by human body electric shock and line aging and the ground fault of the equipment are caused by leakage current. The leakage current is generally At 30mA-3A, these values are so small that traditional switches cannot be protected, so a residual current-operated protection device must be used.
The residual current relay is a residual current transformer to detect the residual current, and under specified conditions, when the residual current reaches or exceeds a given value, one or more electrical output circuit contacts in the electrical appliance will open and close. Switch electrical appliances.
Here are three common leakage situations.
1.High-sensitivity RCD with I△n≤30mA must be used to prevent direct contact and electric shock.
2.The medium sensitivity RCD with I△n greater than 30mA can be used to prevent indirect contact electric shock.
3.A 4-pole or 2-pole RCD shall be used for fireproof RCD.
For the IT systems, residual current relays are used as required. In order to prevent the insulation of the system from degrading and as a secondary fault backup protection, according to the wiring type, a protective measure similar to the TT or TN system is adopted. First, an insulation monitoring device should be used to predict a failure.
For the TT system, a residual current relay is recommended. Because when a single-phase ground fault occurs, the fault current is very small and difficult to estimate. If the operating current of the switch is not reached, a dangerous voltage will appear on the housing. At this time, the N wire must pass through the residual current transformer.
For the TN-S system, a residual current relay can be used. Cut off the fault more quickly and sensitively to improve safety and reliability. At this time, the PE wire must not pass through the transformer, and the N wire must pass through the transformer, and it must not be grounded repeatedly.
For TN-C systems, residual current relays cannot be used. Because the PE wire and the N wire are integrated, if the PEN wire is not repeatedly grounded, when the shell is energized, the current in and out of the transformer is equal, and the ASJ refuses to move; if the PEN wire is repeatedly grounded, part of the single-phase current will flow into the repeated grounding. After reaching a certain value, ASJ malfunctioned. It is necessary to transform the TN-C system into a TN-C-S system, which is the same as the TN-S system, and then connect the residual current transformer to the TN-S system.
4. Product Introduction
Acrel Electric's ASJ series residual current relay can meet the protection of the above-mentioned leakage conditions, and it can be used in conjunction with a remote trip switch to cut off the power supply in time to prevent indirect contact and limit the leakage current. It can also be directly used as a signal relay to monitor power equipment. It is especially suitable for the safety protection of electricity consumption in schools, commercial buildings, factory workshops, bazaars, industrial and mining enterprises, national key fire protection units, smart buildings and communities, subways, petrochemicals, telecommunications and national defense departments.
ASJ series products mainly have two installation methods. ASJ10 series are rail-mounted installations. The appearance and functions are shown in the following table:
Conformation | Type | Main function | Functional difference |
| ASJ10-LD1C | 1. Residual current measurement 2. Over-limit alarm 3. The rated residual operating current can be set 4. The limit non-driving time can be set 5. Two sets of relay output 6. With local/remote test/reset function | 1. AC type residual current measurement 2. Current limit alarm indication |
 | ASJ10-LD1A | 1. A-type residual current measurement 2. Current percentage bar display |
 | ASJ10L-LD1A | 1, A-type residual current measurement 2. Segment LCD display 3. Transformer disconnection alarm 4. Pre-alarm value can be set, return value can be set 5. 25 event records |
ASJ20 series are panel mounted, the appearance and function are shown in the table below
Conformation | Type | Main function | Functional difference |
 | ASJ20-LD1C | 1. Residual current measurement 2. Over-limit alarm 3. The rated residual operating current can be set 4. The limit non-driving time can be set 5. Two sets of relay output 6. With local/remote test/reset function | 1. AC type residual current measurement 2. Current limit alarm indication |
 | ASJ20-LD1A |
| 1. A-type residual current measurement 2. Current percentage bar display |
Among them, the difference between AC type and A type residual current relay is: AC type residual current relay is a residual current relay that can ensure the tripping of the residual sinusoidal alternating current that is suddenly applied or slowly rising, and it mainly monitors sinusoidal alternating current signals. Type A residual current relay is a residual current relay that can ensure the tripping of residual sinusoidal alternating current and residual pulsating direct current that is applied suddenly or slowly, and mainly monitors sinusoidal alternating current signals and pulsed direct current signals.
The specific wiring terminals and typical wiring of the instrument are as follows:
5.Conclusion
The use of leakage protectors can effectively prevent residents from getting electric shock, and can remind users to take necessary protective measures in time. At the same time, the use of hierarchical protection can effectively reduce failure points and avoid greater losses. ASJ series residual current relay products can monitor the leakage current in the line. When the leakage current reaches or exceeds the set value, the internal relay will act to issue an alarm, and can be linked with the circuit breaker switch to quickly cut off the line to ensure line safety.
References
[1]Jie Zhang, Jianming Wong. Using residual current action protector as a platform to realize intelligent management of station area[C]// Chinese Society of Electrical Engineering. Chinese Society of Electrical Engineering, 2016.
[2] Enterprise Microgrid Design and Application Manual. 2020.6
[3]Kai Hu. Analysis of leakage protection technology in the construction of electrical engineering of buildings[J]. Doors and Windows, 2017(2).
[4]Yong Wong. Application of residual current operated protector in rural power grid[J]. Rural Electrician, 2005, 11(11):21-21.
[5]Xiaowen Kang. Residual current operated protector in rural power safety management Application in [J]. Popular Electricity, 2010(06):42-42.
About the author: Jianguo Wu, male, undergraduate,Acrel Co., Ltd., the main research direction is insulation monitoring and residual current monitoring, Email: zimmer.wu@qq.com, mobile phone: 13524474635
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