GGXHG arc and resonance suppression and over-voltage protection device
GGXHG arc and resonance suppression over-voltage protection device is used in the 3~35KV neutral point non effectively grounded power system to limit all kinds of over-voltage during the operation of such systems, especially the single-phase arc grounding over-voltage, so as to effectively improve the operation safety and power supply reliability of such power grids.
1、 Harm of single-phase arc grounding overvoltage
Most of the 3~35KV (including 66KV) power grids in China use the neutral point ungrounded operation mode. When single-phase metallic direct grounding occurs in such power grid, the voltage of non fault phase to ground will rise to line voltage, and the value of three-phase line voltage will remain unchanged, and there is still a 120 ° phase difference. The operation of three-phase electrical equipment is not affected, so the normal transmission of electric energy will not be affected. Therefore, the national standard stipulates that such power grids are allowed to operate with fault for a short time after single-phase ground fault, which improves the reliability of power supply of such power grids.
The existing operation regulations stipulate that when single-phase ground fault occurs in the neutral point non effective grounding system, it is allowed to operate for two hours, but the regulations do not clearly define the concept of "single-phase ground fault". If the single-phase grounding fault is metallic grounding, the voltage of the fault phase will drop to zero, and the voltage of the other two sound phases will rise to the line voltage. The electrical equipment of this kind of power grid should be able to withstand this overvoltage without damage under normal conditions. However, if the single-phase grounding fault is intermittent arc grounding, it will produce an overvoltage in the system up to 3.5 times the peak value of the phase voltage. If such a high overvoltage acts on the power grid for several hours, it is bound to cause cumulative damage to the insulation in the electrical equipment, causing insulation breakdown to the ground in the insulation weak link of the sound phase, and then developing into an interphase short circuit accident. In the transient process of intermittent arc grounding, the actual system will form a multi frequency oscillation circuit, which will not only produce a high amplitude phase to ground overvoltage, but also may produce a high amplitude phase to phase overvoltage, which will make the insulation weakness between the phases flashover and develop into a phase to phase short circuit accident.
2、 Arc suppression effect of resonant grounding mode
With the large-scale technological transformation of urban and rural power grids in China, urban and rural distribution networks must be oriented Cable With the development of technology, the capacitive current of the system to the ground is gradually increasing, and the problem of arc grounding overvoltage is also serious day and night. In order to solve the above problems, many power grids adopt resonant grounding, that is, arc suppression coil is installed at the neutral point of the power grid. When single-phase arc grounding occurs in the system, the inductive current generated by the arc suppression coil is used to compensate the capacitive current at the fault point, so that the residual current flowing through the fault point is reduced, so as to achieve natural arc extinction. The actual operation experience has proved that in the power grid whose neutral point is grounded through the arc suppression coil, equipment damage and accidents affecting the safety of system operation caused by single-phase arc grounding overvoltage still occur from time to time. The reason is that due to the diversification of power grid operation modes and the randomness of arc grounding points, it is really difficult for arc suppression coils to effectively compensate the capacitive current, and the arc suppression coils only compensate the power frequency capacitive current, while the actual current passing through the grounding points not only includes power frequency capacitive current, but also contains a large number of high-frequency current and resistive current, In severe cases, only high-frequency current and resistive current can maintain the continuous combustion of the arc. Even in some cases, due to the existence of arc suppression coil, arc re ignition may occur at the unfavorable time when the recovery voltage is high, which will increase the arc grounding overvoltage. With the development of urban and rural power grids and the increasing requirements of production and life on the reliability of power supply, the harm caused by each insulation accident and the affected area are bound to increase. For this reason, our company has developed the GGXHG arc and resonance suppression and over-voltage protection device, which limits the phase to ground and phase to phase over-voltage of the neutral point non effectively grounded power grid to the safe operation of the power grid, Completely solve the threat of various overvoltage to the safe operation of equipment and power grid, and improve the power supply reliability of this kind of power grid.
3、 Composition and function of the device
GGXHG arc and resonance suppression and over-voltage protection device is a new technical product developed by Guogen Science and Technology Co., Ltd. to quickly eliminate the harm to electrical equipment caused by arc grounding of neutral point non effectively grounded power grid. Its principle is shown in Figure 1. It mainly consists of the following seven parts:
Figure 1 Schematic Diagram of GGXHG Arc and Harmonic Suppression and Overvoltage Protection Device
1. Combined overvoltage protector (TBP) composed of high-capacity ZnO nonlinear elements
Compared with various existing overvoltage protectors, the TBP three-phase combined overvoltage protector has lower protection value and higher ability to withstand temporary overvoltage. It can effectively limit the transient overvoltage at the beginning of high amplitude arc grounding in the system before the subsequent protection device acts. It is the front device in this device to limit various overvoltage, It is mainly used to limit atmospheric overvoltage and switching overvoltage.
2. Split phase controlled high-voltage vacuum contactor (JA, JB, JC)
The high-voltage vacuum contactor with split phase control is composed of three single-phase vacuum AC contactors with mutually locked operation circuits, which are respectively connected between the three-phase bus of the system and the ground. When the system is normal, it is in the off state and will not have any impact on the normal operation of the system; When single-phase arc grounding occurs in the system, the vacuum contactor will close and open according to the instructions of the microcomputer controller to directly ground the fault phase bus, thus completing the arc grounding overvoltage limitation.
3. Split phase resistance capacitance absorber (R-C)
The split phase resistance capacitance absorber is composed of R-C absorption device composed of three groups of resistance capacitors in series, which is connected in parallel to both ends of the split phase control high-voltage vacuum contactor to limit the high-frequency overvoltage of the absorption system. When intermittent arc grounding occurs in the system, limit the arc grounding overvoltage to a safe range before the arc suppression contactor acts; When the arc suppression contactor is opened and exited, the amplitude and rising speed of the recovery voltage of the fault phase are limited, so that the fault point will not be re ignited due to the overvoltage caused by the operation of the vacuum contactor, thus greatly improving the success rate of the device in eliminating the transient grounding fault.
4. Multifunctional microcomputer controller ZK
a. The device has the following eight functions: arc suppression function, harmonic suppression function, 32 line selection small current automatic line selection function, over-voltage limiting function, atmospheric over-voltage protection function, protection operation over-voltage function, resistance capacitance absorption protection function, protection arc grounding over-voltage, etc., and also has the functions of PT cabinet.
b. The core component of the arc suppression device - the measurement and control device shall adopt dual CPUs, and the main CPU shall adopt 32-bit DSP technology. The device has the power on self-test function to prevent the arc suppression cabinet from misjudging, misoperating, refusing to operate and other abnormal conditions in the system operation.
c. Arc suppression device shall be set CA N and RS-485 external communication interfaces adopt standard MODBUS RTU communication protocol to ensure that the device is compatible with the whole monitoring system. d. After single-phase arc grounding occurs in the system, the device can extinguish the arc at the fault point, and limit the over-voltage of the non fault phase to the level of the online voltage, and is equipped with primary and secondary harmonic elimination devices.
e. After the device acts, it can allow 80A capacitive current to pass continuously for more than 2 hours, which is convenient for users to complete switching operation for important loads or Power Supply Switch work. f. The arc suppression device shall conduct true PT disconnection, metal grounding and arc light grounding tests under the same voltage level, and each phase shall be tested for at least 30 times, the action accuracy shall reach 100%, and the arc current generated by the test shall not be less than 200A.
g. When PT disconnection, metal grounding and arc grounding faults occur in the system, in addition to the fault type and fault phase displayed on the panel, passive contact signals are also output.
h. The device is equipped with a microcomputer interface, which provides a communication protocol to realize remote data transmission. The device is monitored remotely through the booster station monitoring system or background terminal.
i. The device can store fault records for at least 18 times, which is convenient for users to read or print.
j. The device has self inspection function, and can start emergency signal in case of internal failure or loss of working power supply of the device.
k. The device can limit the overvoltage between phases and between phases and ground to less than 3.5 times.
l. The action time of the whole device shall be ≤ 10ms.
5. High voltage current limiting fuse
High voltage current limiting fuse is the backup protection device of the whole device, which is used to prevent short circuit accidents. It is characterized by rapid breaking and large breaking capacity.
6. Voltage transformer
It is used to convert the primary high voltage of the system to the secondary low voltage that can be processed by the microcomputer controller for monitoring and sampling.
7. High voltage isolation switch It is used for switching during installation and maintenance of the device.
4、 Harmonic elimination principle
1、 The device adopts the microcomputer secondary resonance elimination technology. When the system has resonance, the microcomputer controller performs different resonance elimination actions according to the resonance type:
(1) If the resonance of the system is frequency division resonance, the microcomputer controller will short circuit the open delta winding of PT instantly to destroy the resonance parameters and eliminate the resonance;
(2) If the resonance of the system is power frequency or high frequency resonance, the microcomputer controller connects the high-power resonance elimination resistor to the open delta winding of PT for resonance elimination.
So as to destroy the resonance parameters of the system, consume the resonance power, and eliminate the resonance fault of the system.
2、 Harmonic elimination characteristics:
(1) . It adopts the microcomputer secondary harmonic elimination technology, which has a very fast response time, and the harmonic elimination effect is far better than the traditional harmonic elimination device;
(2) . It has no influence on the voltage output of the protection winding (open delta) of the voltage transformer, and avoids the disadvantage that the traditional harmonic elimination technology affects the voltage output of the protection winding of the voltage transformer.
5、 Basic operating principle of the device
When high amplitude over-voltage occurs in the system, the combined over-voltage protector TBP is put into operation first to limit the system over-voltage within the safe range allowed by the electrical equipment insulation; When the overvoltage amplitude of the system is low, the split phase resistance capacitance absorber R-C works to absorb high-frequency overvoltage and provide weak insulation protection for equipment. When single-phase grounding occurs in the system, microcomputer controller ZK calculates and processes the signals of three-phase voltage Ua, Ub, Uc and open triangle voltage U0 provided by voltage transformer, judges the grounding nature and phase, and conducts the following processing:
If the fault occurred is intermittent arc grounding, the microcomputer integrated controller will close the high-voltage vacuum contactor of the fault phase after judging the grounding phase, so that the system can quickly change from unstable arc grounding to stable metallic direct grounding, the fault phase voltage will drop to zero, and the arc will disappear. After a few seconds, disconnect the grounded high-voltage vacuum contactor again. At this time, the parallel resistance capacitor absorber R-C works to limit the recovery speed and amplitude of the fault phase voltage and prevent the grounding point from being re ignited due to overvoltage. If the fault disappears, it indicates that the arc grounding fault is a transient grounding fault caused by overvoltage shock, and the system returns to normal operation. If the system appears stable arc grounding in the original fault phase again after the contactor is disconnected, the device determines that the fault is a long-term grounding fault, and then closes the high-voltage vacuum contactor of the fault phase again, waiting for the operator on duty or the microcomputer to select the line.
If the fault occurred is a metallic direct grounding fault, the device can directly ground the fault phase bus according to the user's requirements, reduce the current flowing through the fault point, send an indication signal, and wait for the operator on duty or the microcomputer to select the line.
If the fault is TV disconnection fault, the device will only send an indication signal and wait for the personnel on duty to deal with it.
6、 Main features of the device
1. Greatly improve the safe and stable operation level of power system
All kinds of overvoltage can be limited to a lower voltage level, which greatly reduces insulation accidents and continuous accidents caused by overvoltage.
2. With perfect overvoltage protection function
It can protect atmospheric over-voltage, operating over-voltage and arc grounding over-voltage, and its function of limiting arc grounding over-voltage is better and more perfect than that of installing arc suppression coil. After installing this device, the system that should be installed with arc suppression coil according to the design specifications can no longer be installed.
3. Improve the operation conditions of the power grid
Since the arc grounding overvoltage with long action time in this kind of power grid is eliminated, the metal zinc oxide The probability of MOA accident is greatly reduced. 4. Simple selection and convenient use
The mechanism of arc suppression and overvoltage protection of the device is independent of the single-phase grounding capacitance current of the power grid, so its protection performance is not affected by the change of power grid operation mode and power grid expansion, and can be used in large power grids and small power grids.
5. Simple structure and convenient installation
The whole device consists of a high-voltage switch cabinet, which can replace the original voltage transformer cabinet. It is simple in structure, small in size, convenient in installation and commissioning, and no longer occupies additional land. It is applicable to both the substation and the high-voltage auxiliary system of the power plant. It is applicable to both the new station and the reconstruction of the old station. * * * The system with arc suppression coil is equipped with this device to improve the protection.
7、 Model and parameters of the device
1. Model description
GGXHG─ □ / □
Rated current (A)
Rated system voltage (kV)
Device code
2. Technical parameters
Rated frequency: 50 (Hz)
Rated voltage: 6 10 35 (KV)
Rated current: 10 16 20 31.5 50 63 100 200 (A)
8、 Model selection and requirements
1. The rated voltage of the device is equal to the rated voltage of the system.
2. The rated current of the device shall not be less than the larger single-phase grounding capacitive current of the protected system.
9、 Structure, outline and installation dimensions
1. See Figure 2 for structure
2. Standard size of cabinet
6kV： 800×1500×2300
10kV: 1000×1500×2300
35kV: 1800×2400×2900
3. It can be produced according to user requirements
Figure 2 Structure diagram of GGXHG arc suppression and overvoltage protection device (side view)
explain:
1. Microcomputer controller 2, auxiliary switch 3, operating mechanism 4, high-voltage current limiting fuse
5. Vacuum contactor 6, resistance capacitance absorber 7, post insulator 8, disconnector
9. High voltage fuse 10, TBP overvoltage protector 11, voltage transformer
10、 Service conditions
1. Ambient temperature: - 30 ° C~40 ° C
2. Altitude: 2000m and below
3. Service environment: there shall be no explosive mixture of pulverized coal, gas, flue gas, etc
11、 Packaging, transportation and storage
1. Generally, it is packed in wooden cases. The cabinet base shall be fixed on the bottom plate of the packing box.
2. It is recommended not to transport on roads below Class III for a long distance, and unpack if necessary.
3. Do not store it outdoors for a long time. If it is not used for a long time, it should be stored in a dry and ventilated indoor warehouse.
12、 Installation, commissioning, maintenance, pre-sales and after-sales service
1. The company is responsible for drawing design and parameter selection according to user requirements. It can provide technical guidance services for on-site installation and commissioning, and users can provide necessary cooperation.
2. During operation, maintenance and inspection shall be carried out according to the requirements of general high-voltage switchgear. In case of arc suppression action, careful inspection shall be carried out to check whether the fuse is damaged and whether the contactor contact is in good contact. If necessary, insulation withstand voltage test of equipment shall be carried out.
3. Within 12 months from the date of installation and use, if it can not be used normally due to quality problems, it will replace parts or repair for users free of charge;
3. Be responsible for training users in technology and use.
4. The company is responsible for providing spare parts and after-sales service for a long time.
13、 Ordering Instructions
1. When ordering, the user shall provide: rated voltage of the system, large single-phase grounding capacitive current of the power grid, cabinet size and bus arrangement.
2. If the user has special requirements, it should be put forward when ordering, and the color code should be provided for the cabinet color.
3. If other additional accessories or spare parts are required, the type and quantity required shall be indicated when ordering.
14、 Design icon
The design diagram of GGXHG arc suppression and overvoltage protection device is shown in the following figure:
