Brief description of intelligent harmonic elimination and arc suppression device:
In China’s 3~35KV power supply and distribution system, most of them are neutral point ungrounded systems. According to our company’s industry standards, when single-phase grounding occurs, the system is allowed to operate abnormally for 2 hours, which greatly reduces operating costs and improves the reliability of the power supply and distribution system. However, due to the gradual increase of the power supply capacity of the system, the power supply mode has gradually changed from overhead lines to cable lines, and the capacitance current of the system to ground will become very large. When the system forms single-phase grounding, the arc generated by the excessive capacitor current is not easy to be extinguished, and it is likely to become an intermittent arc grounding device. At this time, the overvoltage of the arc grounding device and the ferromagnetic series resonance overvoltage caused by it will seriously endanger the safe operation of the power grid. The overvoltage of the single-phase arc arc grounding device is relatively serious, and the uncommon fault phase overvoltage level reaches 3~3.5 times of the normal operation phase voltage. If such a high overvoltage acts on the grid for several hours, it will definitely damage the insulation of electrical equipment. After the insulation of electrical equipment has been accumulated and damaged for many times, an insulation weakness will be formed, resulting in insulation breakdown and grounding, resulting in a two-color short circuit failure accident. In addition, it will also cause safety accidents such as electrical equipment insulation breakdown (especially motor insulation breakdown), cable explosion, voltage transformer saturation state excitation regulator burning PT, and zinc oxide arrester explosion. In order to solve the overvoltage problem caused by the long-term electric arc grounding device, the arc suppression coil is used to compensate the current of the neutral point capacitor, and the occurrence of common fault point electric arc is suppressed. The purpose of this method is to eliminate electric light. However, due to the many characteristics of the arc suppression coil itself, it is impossible to effectively compensate the capacitive current, especially the damage caused by high frequency components to the power supply cannot be eliminated. On the basis of studying various arc suppression rings, our company has developed the HYXHX intelligent arc suppression device.
The working principle of the intelligent arc suppression device:
1. When the system is in normal operation, the computer control board ZK of the device continuously monitors the voltage signal generated by the voltage transformer PT;
2. When the working voltage of the auxiliary secondary leading triangle of the voltage transformer changes from a low potential difference to a high potential, it means that the system software is faulty. At this time, the microcomputer control board ZK starts immediately, and at the same time judges the fault type and phase difference according to the changes of the PT secondary output signals Ua, Ub and Uc:
a. If the single-phase PT is broken, the microcomputer controller ZK will display the difference of the broken line and the signal of the broken line, and output the passive switch contact signal at the same time;
b. If it is a metal grounding fault, the microcomputer control panel ZK displays the grounding fault location and grounding attribute signal, and outputs a passive switch touch signal at the same time. According to the special requirements of the user, it can also issue a closing action command to the vacuum contactor JZ in the cabinet, which can greatly reduce the contact voltage and step voltage, and is conducive to ensuring personal safety;
c. If it is an arc fault, the microcomputer control panel ZK will display the ground fault phase and ground characteristic signal, and at the same time send a closing command to the fault phase vacuum contactor JZ, and the AC contactor will immediately close the arc The grounding is changed to metal grounding. Because of the pressure of the electric arc on both sides, the grounding electric arc drops to zero immediately, and the electric arc is completely extinguished. If it is used in a grid dominated by transmission lines, the vacuum contactor JZ of the equipment will automatically shut down after 5 seconds of operation. If it is an instantaneous speed failure, the system will recover. If it is a permanent fault, it will continue to operate and play a role in permanently limiting overvoltage. And output passive switch contact signal;
d. If the device has an automatic selection function, when the auxiliary secondary opening triangle voltage u of the transformer PT changes from low potential to high potential, the small current grounding selection module immediately collects the zero-phase current of each line, and when there is no single-phase grounding In the case of a metal ground fault that cannot be recovered normally, select the fault line according to the amplitude of the zero-phase current of the line. The fault line is selected according to the principle of large mutation before and after the grounding arc is extinguished.
Main features of intelligent arc suppression device:
1. The device runs fast and can run within 30 to 40 milliseconds, which greatly shortens the duration of the single-phase grounding arc;
2. The arc can be extinguished immediately after the device is running, effectively limiting the arc grounding overvoltage within the online voltage range
3. After the operation of the device, allow the capacity current of the system to be passed continuously for at least two hours, and the user can deal with the faulty line after completing the shift operation of the load
4. The protection function of the equipment is not affected by the scale and operation mode of the power grid;
5. The device is cost-effective. Voltage transformers can provide voltage signals for metering and protection, replacing traditional voltage transformer cabinets.
6. The device is equipped with a small current grounding line selection device, which can greatly improve the accuracy of line selection by utilizing the characteristics of large mutations of the zero-sequence current of the fault line before and after arc extinguishing.
7. The device adopts the combination of anti-saturation voltage transformer and special primary current-limiting harmonic canceller, which fundamentally suppresses ferromagnetic resonance and effectively protects PT.
8. This equipment has the function of recording the common faults of the electric arc grounding device, and provides data for customers to analyze safety accidents.
The basic functions of the intelligent arc suppression and harmonic elimination device:
1. When the device is in normal operation, it has the function of PT cabinet
2. At the same time, it has the function of system disconnection alarm and lock;
3. System metal ground fault alarm, transfer system ground fault point function;
4. Clear the arc grounding device, the system software series resonance function; the bottom voltage and overvoltage alarm function;
5. It has information recording functions such as fault alarm elimination time, fault nature, fault phase, system voltage, open circuit delta voltage, capacitor ground current, etc., which is convenient for fault handling and analysis;
6. When the system software has a single-phase grounding fault, the device can immediately connect the fault to the ground within about 30ms through the special phase-splitting vacuum contactor. The grounding overvoltage is stable at the phase voltage level, which can effectively prevent the two-color short circuit fault caused by single-phase grounding and the zinc oxide arrester explosion caused by the arc grounding overvoltage.
7. If the metal is grounded, the contact voltage and step voltage can be greatly reduced, which is conducive to ensuring personal safety (metal grounding can be set whether the device operates according to user requirements);
8. If used in a power grid mainly composed of overhead lines, the vacuum contactor will automatically close after 5 seconds of device operation. If it is a momentary failure, the system will return to normal. In the event of a permanent failure, the device will operate again to permanently limit the overvoltage.
9. When a PT disconnection fault occurs in the system, the device will display the phase difference of the disconnection fault and output a contact signal at the same time, so that the user can reliably lock the protection device that may fail due to PT disconnection.
10. The device’s unique “intelligent socket (PTK)” technology can comprehensively suppress the occurrence of ferromagnetic resonance, and effectively protect platinum from ignition, explosion and other accidents caused by system resonance.
11. The device is equipped with RS485 socket, and adopts standard MODBUS communication protocol to ensure the compatibility mode between the device and all video surveillance systems, and maintain the functions of data transmission and remote control.
Additional functions of intelligent arc suppression and harmonic elimination device:
1. The automatic selection function can be configured according to the user’s requirements
2. The HYLX small current grounding line selection device developed by our company mainly selects the line according to the amplitude of the zero-sequence current when the system is grounded. It overcomes the disadvantage of low accuracy of the selection line when the selection line speed is slow and the arc is grounded in the usual selection line device
3. The function of eliminating (removing) resonance (vibration) can be configured according to user requirements;
4. The special anti-saturation voltage transformer developed by our company can be configured to match the primary current-limiting harmonic canceller, which fundamentally destroys the ferromagnetic resonance condition and avoids “burning platinum” and “platinum safety explosion” caused by resonance overvoltage ACCIDENT.
5. Microcomputer harmonic elimination device can also be configured according to user requirements to eliminate ferromagnetic resonance.
Post time: Apr-13-2023