1.Overview

Low-voltage grounding resistance cabinet refers to a complete set of grounding resistance devices in 220V~1140V low-voltage systems. In order to improve the power quality of the 1140V, 660V, 380V, and 220V systems and the safe operation of the power supply system, avoid the breakdown of the electrical equipment in the system caused by the fault current when a ground fault occurs, or cause a large-scale equipment power outage in the system, etc., in the power plant , The transformer room, and the neutral point of the large motor should adopt a high-resistance grounding operation mode.

After the neutral point grounding resistance cabinet is installed, when a single-phase grounding fault occurs, it is affected by the grounding point resistance, which can reduce the transient overvoltage during single-phase grounding, eliminate the generation of arc grounding overvoltage and some resonance overvoltages. To protect the operating equipment in the power supply system. At the same time, the unbalanced voltage generated through the neutral point after the fault generates a reactive resistive current through the resistance to the ground. After this current flows through the fault point, the relay protection device can directly select the fault line or quickly remove the fault point.

The device has high temperature resistance, high resistivity, low temperature coefficient of resistance, and at the same time has excellent mechanical properties such as high tensile strength and good toughness. The device has advanced automation functions such as intelligent monitoring, protection settings, background communication data transmission, etc. HYGZN series low-voltage grounding resistance cabinets are mainly used for low-voltage diesel generator sets 220V, thermal power plants 380V, coal mine production enterprises 660V, coal mine power supply 1140V, and Various factories and mines motors start and brake fields.

2.Model and working principle

3.General conditions of use

1. Environment: Temperature: -45℃~+50℃, relative humidity: not more than 95% (25℃), altitude not exceeding 4000m;

2. Grid frequency: 48~52Hz (50Hz system), 58~62Hz (60Hz system), with a good grounding grid;

3. There is no flammable, explosive, corrosive gas and conductive dust in the surrounding environment.

Note: Special conditions of use must be specified when ordering.

4.Features

1. The product adopts high-quality stainless steel nickel-chromium alloy (Cr20Ni80) resistance, high conductivity, temperature coefficient α of 8.5×10-5ppm/℃ (20-1100℃) and small temperature coefficient. The resistance can withstand 1500℃ flame-proof and explosion-proof, high reliability, corrosion resistance and stable resistance;

2. The product can be used in various low-voltage power distribution systems. If there is no neutral point plus a grounding transformer, it can be used in conjunction with it. It has a good effect on suppressing system overvoltage and preventing various impacts. The resistance of the resistance cabinet can be changed from 1 ohm to 2000 ohm, the current is designed from 0.5 ampere to 1000 ampere;

3. The resistance cabinet is used indoors or outdoors, and the cabinet body is made of stainless steel plate or cold-rolled steel plate sprayed with plastic;

4. The product can be equipped with grounding records and temperature and humidity control devices to record the operation status of the equipment, and can also be equipped with monitoring and control protection devices.

5. Technical data

1. General parameter configuration of low-voltage resistance cabinet

Note: If users have special requirements for parameters, they can be customized according to specific requirements

6. Appearance and installation

7. Inspection and acceptance

After receiving the product, the user should check it immediately

1. Check whether the quantity of each item in the packing list is consistent with the actual product, and whether the nameplate data is consistent with the order contract;

2. Check whether the appearance of the product is bumped or deformed, whether the internal electrical components and connections are damaged, falling off and loose, whether there is dirt or foreign matter in the insulation, etc.;

3. After the product is unpacked and inspected, if it is not put into operation immediately, it should be properly stored.

8. Product installation, testing and maintenance

This product can be installed on a dedicated foundation or on a concrete platform and placed horizontally. Fix it on the foundation with anchor bolts through the bolt holes (Φ16mm) at the bottom of the cabinet. If it is installed on a concrete foundation, it is recommended to use expansion bolts to fix it.

The grounding end of the resistance element is reliably connected to the grounding grid through a single-core cable or a connection bar. One end of the cable is connected to the resistance cabinet through the cable hole at the bottom of the cabinet from bottom to top, and the cable head is made, and it is reliably connected to the ground terminal of the resistance element or the output terminal of the (zero sequence) current transformer. Already prepared) to protect and block. The inlet end of the resistance cabinet is connected to the inlet end of the grounding transformer or resistor with a single-core cable or copper bar; check and tighten all the fixing and connecting bolts in the cabinet to ensure a firm and reliable connection. The shell is reliably grounded through the ground bolt.

Test before putting into operation, measure the resistance value of the resistance element, measure the insulation resistance, and carry out the power frequency withstand voltage test according to the specified standard. The test voltage is not more than 85% of the factory test voltage; the front panel of the cabinet is also original and ready to be put into operation.

Note: The secondary coil of the current transformer is not allowed to operate in an open circuit. The secondary coil has been short-circuited before leaving the factory. If you need to use it, please remove the short-circuit wire and connect the secondary coil to the circuit. If it is not used, please keep it short-circuited.

The grounding resistance cabinet is highly reliable and generally does not require special power outage maintenance. It is recommended to use the main transformer or busbar in the station to perform inspection and maintenance.

9. Ordering instructions

Please inform the following parameters when ordering:

1. System rated voltage, (kv), short-term allowable current (A) and flow time (S), nominal (Ω);                                 

2. Do you need to install additional current transformers (CT): Provide CT ratio and capacity;

3. Wire entry and exit methods: top entry and bottom exit, bottom entry and bottom exit, or other, resistance cabinet material, cabinet (IP) protection level, color code and installation location (indoor\outdoor);

4. Whether it is necessary to install an intelligent controller device.