Abstract: On-load voltage regulation of distribution transformer is one of the means to realize voltage control of distribution network. On-load voltage regulation switch is a key component of distribution transformer to achieve voltage regulation. The technical performance of the distribution transformer directly affects on-load voltage regulation. The safe and reliable operation of the electric transformer. The implementation method of on-load tap-changer switching technology for distribution transformers is introduced. It is divided into three categories: mechanical, power electronics, and hybrid. The technical implementation principles and advantages and disadvantages of different on-load tap-changers are analyzed. The development direction of on-load voltage regulating technology for distribution transformers and the need for in-depth research and focus.
Keywords: distribution network; distributed power supply; voltage control; distribution transformer; on-load voltage regulation
introduction
Voltage quality is one of the important indicators for assessing the power supply service level of power companies. China's rural power grids have large power supply lines, many branch lines, and a wide range of power load points. They are small and scattered, and have seasonal load characteristics. The power consumption period is too concentrated, the annual average load rate is low, and the peak-to-valley difference is large. During the trough loading period, the distribution transformer is under light-load operation and the power supply voltage to the user is high. During the peak load period, the distribution transformer is under heavy load or overload operation, and the power supply voltage to the user is low (referred to as “low voltageâ€). The high supply voltage will accelerate the aging of the insulation of the electrical equipment, increase the loss, and even endanger the safety of the power grid and equipment. The low supply voltage, that is, the "low voltage" problem will cause the efficiency of the power supply equipment to be reduced, endangering the safe and economical operation of the power grid, leading to the failure of normal use of some household appliances and seriously affecting the production and life of residents.
With the further development of smart grid construction, the proportion of clean energy utilization has increased year by year. The construction of distributed power sources and the construction of electric vehicle charging piles have led to more pronounced voltage fluctuations in distribution networks. Currently, for the voltage control technologies of high- and medium-voltage distribution networks, such as on-load voltage regulating main transformers, line voltage regulators, substation automatic reactive power compensation, line automatic reactive power compensation, etc., literature has been studied and proposed for maintenance-free Or no arc, no impact switching on-load voltage regulation program, but no systematic analysis of its advantages and disadvantages, low-voltage power distribution network voltage regulation technology is less involved. Therefore, this article will focus on the domestic and international distribution transformer on-load voltage regulator technology.
1 Research status of voltage regulating technology for distribution transformers
The no-load voltage regulation mode of distribution transformers, which occupy the mainstream in low-voltage distribution networks, can no longer meet the voltage regulation requirements of the distribution station area. On-load voltage regulator type distribution transformer can change the ratio of high and low voltage side to side under load conditions, limit the voltage fluctuation within the qualified range, guarantee the continuity of power supply, improve the quality of power supply, and can greatly reduce the power loss. Started research and discussion of on-load voltage regulating technology and application of medium and low voltage distribution transformers. According to the composition of transformer taps, the on-load tap-changer transformer is divided into three types: mechanical type, auxiliary coil type, and power electronic switch type. The principle and development process of typical voltage regulator technology are analyzed and analyzed. Compare. The literature studies a GPS-based distribution transformer with on-line oil filtering function with on-line pressure regulating system, introduces the system's composition and characteristics, in order to improve the maintenance-free performance of on-load voltage regulating devices of distribution transformers and improve the voltage qualification rate. And power reliability. The literature proposes a power electronic on-load voltage regulation scheme. The main idea is to cancel the traditional mechanical and electric operation mechanism and adopt a binary code adjustment method to realize the on-load voltage regulation of the distribution transformer without arcing.
The application of on-load voltage regulation technology promotes the upgrading of the technical performance of energy-saving distribution transformers, which helps the economic and efficient operation of the distribution station area and the extension and expansion of the distribution automation functions. The combination of on-load voltage regulation and shunt capacitor switching of distribution transformers has become an important means for China to achieve integrated automatic control of voltage and reactive power distribution in the distribution network and limited voltage fluctuations within the qualified range. It guarantees high-quality electric power service for users and improves power distribution. The security, reliability, and economic operation of the network are of important practical significance.
2 new voltage regulator technology and implementation of distribution transformers
The on-load voltage regulating technology of distribution transformers is of great significance for stabilizing the voltage and improving the qualification rate of voltage, and is the basic condition for the realization of voltage and reactive power comprehensive coordination and control in the intelligent distribution station area. The new on-load and voltage-regulating technology of distribution transformers can be roughly divided into three categories: mechanical, power electronic, and hybrid. Mechanical type can be divided into improved, with on-line oil filter type and vacuum arc type 3 kinds.
2.1 Mechanical Load Voltage Regulation Technology
(1) Improved mechanical type. The mechanically modified on-load tap-changer is based on the traditional mechanical on-load tap changer and is additionally provided with an electronic switch circuit. The tap changer consists of a transition resistor and a small number of thyristors, which limits the arc during the tap changeover process. It is achieved through the cooperation of the electronic switch circuit and the mechanical switch. The principle of the tap changer and the electronic switch circuit are shown in Figure 1. The technical advantage of the mechanically modified on-load tap-changer is that it is not necessary to configure a time control loop, and the triggering of the thyristor is realized by operating the mechanical switch; the disadvantage is that the structure is complicated and the operation speed is slow.
(2) With on-line oil filter type. The on-line pressure regulating switch with on-line oil filtering device is based on the traditional on-load pressure regulating switch with an additional on-line oil filtering device. The on-line oil filter device consists of a control system, a power system, a filter element, a pressure gauge, and an operation panel. The power system consists of an electric motor and an oil pump. The filter element is divided into a water removal filter element and a impurity removal filter element to purify the transformer oil and the pressure gauge is used. To monitor the pressure inside the canister, filter replacement tips. On-load pressure regulating device On-line oil filtering device working principle is shown in Figure 2.
The control system records according to the number of on-load tap changer actions, controls the starter motor to drive the oil pump, uses pressure to suck the transformer oil in the tap changer into the canister through the connecting pipe to filter, and then inject the filtered oil into the loaded component. Connect switch oil chamber. The on-load voltage regulation technology has the advantages of being capable of automatic on-line oil filtering, reducing the impact of tap-change arcs, reducing maintenance costs, and being applicable to the on-load voltage regulating and transformation of traditional distribution transformers; the disadvantage is that an additional set of on-line filtering is added. The oil device increases the investment cost and the maintenance work of the device itself (such as replacing the filter element, etc.).Gift Paper Bag,Custom Paper Gift Bags,Recycled Paper Gift Bags,Paper Gift Bags With Handles
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