In China’s 3-35kV power supply and distribution system, most of the neutral point is non-grounded. According to national industry standards, when single-phase grounding occurs, the system can run abnormally for 2 hours, which greatly reduces operating costs and improves the reliability of the power supply and distribution system. However, due to the continuous improvement of the power supply capacity of the system, the mode of the power supply is gradually changing from the transmission line to the cable line, and the current flow from the system to the road capacitor will become very large. When the system is single-phase grounded, the capacitor current protection is not easy to clear, and it is converted into an intermittent grounding system. The overvoltage of the protective grounding system and the ferromagnetic parallel resonance overvoltage caused by the overvoltage will seriously endanger the safe operation of the power grid. The overvoltage of the two-phase protective grounding system is more serious, and the overvoltage level of the mechanical failure phase is 3 to 3.5 times that of all normal operation phase voltages. If such a high overvoltage occurs on the power grid for several hours, it will definitely damage the insulation of electrical equipment. After repeated accumulation and damage of the insulation layer of electrical equipment, it will cause the weak point of the insulation layer, cause the faulty grounding system of the insulation layer, and cause two-color short-circuit failure accidents. In addition, it will also cause safety accidents such as failure of the insulation layer of electrical equipment (the key is the failure of the insulation layer of the motor), explosion of cables, emission point PT of voltage transformer saturation excitation regulator, explosion of high-voltage arrester, etc. In order to solve the overvoltage problem caused by the long-term electrical protective grounding system, the arc suppression coil is used to compensate the current of the neutralization capacitor, and the possibility of common fault point electrical protection is suppressed. The purpose of this method is to remove photoelectricity. At present, it is not clear that the arc suppression coil itself has many characteristics, and it cannot effectively compensate the capacitive current, especially the damage caused in high-voltage power equipment cannot be compensated at will. On the basis of scientific research on various arc suppression rings, our company has developed HYXHX intelligent arc suppression equipment.
The scope of application of the intelligent arc suppression device:
1. This equipment is suitable for 3~35KV medium voltage power system;
2. This equipment is suitable for the power supply system where the neutral point is not grounded, the neutral point is grounded through the arc suppressing coil, or the neutral point is grounded through high resistance.
3. This equipment is suitable for power grids with cables as the main body, hybrid power grids with cables and overhead cables as the main body, and power grids with overhead cables as the main body.
Technical characteristics of intelligent arc suppression device:
The controller adopts four CPU structures, one for human interaction and real-time communication, one for sampling and calculation, one for output signal management to ensure the correctness of output signals, and one for fault recording.
Software Features:
1. Real-time multitasking operating system (RTOS):
The software development adopts real-time operating system and powerful expert library function, and is oriented towards the programming style of daily tasks, and performs resource allocation, task scheduling, exception handling and other tasks in accordance with the all-priority service mode. It works very reliably and can make full use of the performance of digital signal processors and microprocessors. Descriptive computer language is faster to implement, has better readability, and is easy to expand and transplant.
2. Standard MODBUS communication protocol:
Standard MODBUS communication protocol is adopted to facilitate access to various standard integrated automation systems. A separate communication processing microprocessor is selected to further improve the communication processing capability and communication speed.
After the device is activated, it can be restored to a distant place.
3. Using high-performance DSP:
The sampling and calculation part chooses the TMS320F2812DSP chip of TI Company. High frequency up to 150MHz.
According to computer programming, the analog signal collected in real time can be rapidly Fourier transformed in a short period of time, and the pulse current can be obtained and measured in real time.
4.14-bit multi-channel simultaneous sampling digital-to-analog converter:
Because the system is required to have sampling accuracy, AD chooses 14 bits. There are 8 channels in total. Every 4 channel columns use advertisements at the same time to improve the accuracy of use. The external CLK of AD is 16M, thus ensuring the 64-point sampling and calculation requirements of each cycle of our sampling.
5. Using programmable logic devices:
The functions of traditional devices are concentrated on one chip, which reduces the substrate area and the number of pads, shortens the bus length, improves anti-interference performance and circuit reliability, and improves flexibility at the same time.
The entire system software uses two ALTERA EPM7128 as part of the digital logic. This chip can be reprogrammed, which has 2500 gates and 128 macro cells, which can meet the requirements of most complex logic. The application of integrated ic greatly reduces the number of independent logic devices required by the digital system, and improves the reliability and security of the system.
6. Fault recording function:
The fault recorder can record 8 fault waveforms in a cyclical system, including the left and right three-phase voltage, zero-sequence voltage, zero-sequence current, three-phase AC contactor and circuit breaker before and after the fault occurs.
7.The human-machine interface adopts a large liquid crystal display and full Chinese menu to display the current state quantity in a graphical manner, real-time and intuitive three-phase voltage value, zero-phase voltage value, and zero-phase current value.
Main features of the device
1. The action speed of the device is fast, and it can act quickly within 30~40ms, which greatly shortens the duration of the single-phase grounding arc;
2. The arc can be extinguished immediately after the device operates, and the arc grounding overvoltage can be effectively limited within the line voltage range;
3. After the device operates, allow the capacitive current of the system to pass continuously for at least 2 hours, and the user can deal with the faulty line after completing the switching operation of transferring the load;
4. The protection function of the device is not affected by the scale and operation mode of the power grid;
5. The device has high functional cost performance, and the voltage transformer in it can provide voltage signals for metering and protection, replacing conventional PTA giants;
6. The device is equipped with a small current grounding line selection device, which can greatly improve the accuracy of line selection by using the characteristics of the large zero-sequence current mutation of the fault line before and after the arc is extinguished.
7. The device adopts the combination of anti-saturation voltage transformer and special primary current-limiting resonance eliminator, which can fundamentally suppress ferromagnetic resonance and effectively protect stares;
8. The device has the function of arc light grounding fault wave recording, providing data for users to analyze accidents.
The main components of the device and their characteristics:
1. High-voltage vacuum rapid contactor JZ with phase separation control;
This is an AC fast vacuum contactor specially developed by our company that can be controlled by phase separation, and it can be put into operation separately in 8~12ms. One end of the vacuum contactor is connected to the bus, and the other end is directly grounded. During normal operation, JZ is open and closed under the control of microcomputer controller. The operating power circuits of the vacuum contactors of each phase are mutually locked. When any phase closes its system bus grounding device, the other two phases will no longer function.
The function of JZ is to protect system equipment from the influence of overvoltage by quickly transferring from unstable arc grounding to stable metallic direct grounding when arcing grounding occurs in the system.
2. HYT large space explosion-proof maintenance-free overvoltage protector;
HYT large-capacity explosion-proof maintenance-free overvoltage protector acts to limit the overvoltage of the system. It is different from the general zinc oxide arrester (MOA) structure and has the following advantages:
(1) Large flow rate and wide application range;
(2) The four-star connection method can greatly reduce the phase-to-phase overvoltage and greatly improve the reliability of protection;
(3) The high-capacity zinc oxide non-linear resistor and the discharge gap protect each other. The discharge gap makes the charging rate of the ZnO non-linear resistance zero, the ZnO non-linear resistance does not degrade, the non-linear characteristics of the ZnO non-linear resistance do not flow back after the discharge gap is activated, the discharge gap does not undertake the task of arc suppression, and the product life is improved
(4) The voltage surge index is 1, and the charge and discharge voltages are the same under various voltage waveforms, and will not be affected by various operating overvoltage waveforms. Accurate overvoltage protection value and excellent protection performance
(5) The instantaneous value of charge and discharge is close to the remaining voltage, and there is no chopping phenomenon, which is beneficial to protect the insulation layer of winding equipment.
(6) The structure is simple and clear, the volume is small, and the installation is convenient;
The large space explosion-proof maintenance-free overvoltage protector is the first of its kind to limit overvoltages of all kinds. Before the AC contactor JZ is not activated, the overvoltage is limited within the safety range.
3. HYXQ primary current limiting harmonic eliminator:
HYXQ is the invention product of our company. It is installed in series between the primary neutral point of the voltage transformer and the ground to suppress the ferromagnetic series resonance of the voltage transformer and improve the safety factor of the power grid operation.
In normal operation, the resistance is about 40kΩ, and the resistance of the primary winding of the PT is megohm level, so it will not affect the various performances of the PT, and will not greatly change various parameters of the system. When the PT resonates, the iron core is saturated, the excitation current of the primary winding increases, and the MQYXQ resistance increases rapidly, which can play a good damping effect.
HYXQ has simple and clear structure, light weight, convenient installation and reliable operation. It can maintain a continuous and rapid pulse current clearing; the greater the intensity of the series resonance overvoltage, the shorter the pulse current clearing time; this product can limit the sudden increase of the excitation current of the primary winding of the voltage transformer, and avoid the current caused by the primary winding of the voltage transformer. As a result, the kinetic energy of the circuit breaker is not enough to extinguish the arc after the circuit breaker is fused, resulting in a short-circuit failure safety accident of the bus duct.
4. Microcomputer controller ZK:
ZK is the key control part of this equipment. It determines the fault location and fault type (potential transformer disconnection, metal grounding, and arc grounding) based on the Ua, Ub, Uc, and U signals provided by the voltage transformer, and controls the high-voltage vacuum contact in a preset manner Device JZ.
Orphan suppression and line selection can be integrated to achieve the goal of moderate coordination between line selection and line selection.
5. High voltage current limiting fuse FU:
FU is a reserve protector for all equipment, which can avoid the problem of two-color short-circuit failure caused by incorrect wiring or operation errors. It has the following characteristics:
(1) Large breaking capacity, up to 63KA;
(2) Fast circuit breaking, the circuit breaking time is 1~2ms;
(3) Current limiting is easy to use, and the normal fault current can be limited to less than 1/5 of the larger short-circuit fault impulse current;
6. Special voltage transformer PT with auxiliary secondary winding:
The device uses a special anti-saturation voltage transformer. Compared with ordinary voltage transformers, it can not only effectively provide stable voltage signals for system measurement and control, but also reliably protect itself from accidents such as voltage transformer damage and burnout caused by system nonlinear resonance.
Post time: Apr-12-2023