The arc suppression coil is an inductor coil with an iron core. It is connected between the neutral point of the transformer (or generator) and the ground to form the arc suppression coil grounding system. During normal operation, no current flows through the arc suppression coil. When the power grid is struck by lightning or a single-phase arc grounding occurs, the neutral point potential will rise to the phase voltage. At this time, the inductive current flowing through the arc suppression coil and the single-phase grounding capacitive fault current cancel each other out, so that the fault current After being compensated, the residual current after compensation becomes very small, which is not enough to maintain the arc, and then extinguish itself. In this way, the ground can be eliminated quickly without causing overvoltage.
The turn-adjusting arc suppression coil can automatically track the changes in the parameters of the power grid, automatically measure the capacitor current, and automatically adjust the compensation current. Both over and under compensation can be operated, and the method is very flexible. Can well suppress arc ground overvoltage, disconnection overvoltage and transfer overvoltage. The tuning methods of the arc suppression coil can be divided into two types: pre-adjustment and follow-on adjustment. According to the adjustment method of the arc suppression coil reactance, it can be divided into electric on-load adjusting turn type, DC bias magnetic type, air-gap type, capacity-adjusting type and so on.
Most of the medium-voltage systems in China's urban power grids and factories and mines are ungrounded (ie, small current grounded) neutral systems. This type of system can still operate with a fault when a single-phase grounding occurs; however, when a single-phase grounding fault occurs and the grounding capacitor current is large, if the grounding arc develops into intermittent extinguishment and reignition, it will cause arc grounding Overvoltage endangers the insulation of electrical equipment and causes great harm to power supply and consumption equipment. If the ground arc cannot be extinguished in time, it will quickly develop into a phase-to-phase short circuit, causing the line to trip and the power supply to be interrupted. The intelligent arc suppression coil grounding method can accurately measure the grid capacitor current, implement fast automatic compensation for the grid ground capacitor current, and effectively suppress the arc ground overvoltage hazard, reduce the current at the ground point, and achieve the purpose of automatically extinguishing the arc.
The role of the arc suppression coil is to provide an inductive current to compensate the grounding capacitor current after a single-phase grounding fault occurs in the power grid, so that the grounding current is reduced, and the speed of the recovery voltage at both ends of the faulting grounding arc is reduced to achieve the purpose of extinguishing the arc. . When the arc suppression coil is properly tuned, it can not only effectively reduce the probability of generating arcing ground overvoltage, but also effectively suppress the overvoltage amplitude, and also minimize the thermal damage of the fault point and the voltage of the ground network. Wait. The so-called correct tuning, that is, the inductor current is grounded or equal to the capacitor current, and the degree of tuning is described by the degree of detuning V in engineering. After the capacitor current flows into the ground, stray current is formed in the ground. This current may generate sparks, ignite gas explosions, etc., may cause the detonator to fire in advance, and corrode water pipes and gas pipes.
NS-FZ generator neutral point resistance cabinet is connected to the neutral point of the generator. When a single-phase ground fault occurs on the grid or the stator windings of the generator, an additional resistive current is provided to the ground point, so that the current at the ground point is capacitive. It becomes a resistance-capacitance current, thereby ensuring that the generated overvoltage does not exceed the phase voltage of 2.6 times. When designing the parameters, try to control the total ground current within 15A, which can not only meet the requirements of relay protection sensitivity, but also reduce the damage to the iron core when the stator winding of the generator is grounded. Integrate scattered single-phase transformers, resistors, current transformers, measuring instruments, ground protection output terminals and other electrical equipment in a closed metal cabinet, and can optionally be equipped with isolating switches and arresters, which are supplied in sets; high safety and reliability , Clear and tidy layout, easy to install and debug and operation and maintenance. The single-phase transformer it uses is a dry-type insulation transformer, which has stable working performance and strong shock resistance. The secondary side of the transformer is made of stainless steel.
The neutral point of the distribution network system via resistance grounding has been used in developed countries such as Europe and the United States for more than 100 years, and it has become increasingly popular in China's power grids. When the selection line of the compensation amount of the arc suppression coil grounding system cannot meet the rapid development of the system, in order to better limit the system overvoltage level and quickly select and remove faulty lines, the neutral point is connected to the ground through a resistor and the power generation system In order to limit the fault current flowing at the engine outlet and limit the overvoltage level, the neutral point is also used to ground through resistance.
The power system is composed of power generation, transformation, transmission, distribution, and power consumption. Among them, the transformer is a very critical device, and its safe operation is vital to the power system. During the operation of the transformer, the copper loss in the windings and the iron loss in the iron core are converted into thermal energy, which increases the temperature of each part of the transformer. The degree of insulation aging of the transformer determines its service life. The insulation aging is mainly affected by temperature changes. influences. The results of the study show that: in the case of exceeding the design temperature, the insulation aging life of the transformer will be reduced by half for every 6 ° C increase in temperature, which is the six-degree rule for transformer insulation aging. It can be seen that temperature is an important indicator that affects the service life of the transformer.
Aiming at the operating characteristics of power system cables, our company has developed and produced NS-BHQ series cable sheath protectors, which can be widely used in single-core power cable lines to protect the metal sheath of cables from various overvoltages. In order to better meet the needs of the market and facilitate the installation and use by users on site, our company has further developed several forms of protective grounding devices such as direct grounding boxes for cable sheaths, protective grounding boxes and cross-interconnecting protective grounding boxes. At present, various cable protective grounding devices produced by our company have been widely used in the national power and railway systems, and have obtained good operating experience.