Performance requirements of box - type transformer oil

Box-type transformer oil is a mixture of hydrocarbon compounds, transformer oil properties of the transformer oil has a greater impact on the function. To ensure the normal functioning of the pad mounted transformers oil, the step voltage regulators of transformer oil usually have the following requirements: 1. Density as small as possible in order to facilitate the precipitation of oil in water and impurities. 2. Viscosity should be moderate, too much will affect the convection cooling, too small will reduce the flash point. 3. Flash point should be as high as possible, generally should not be less than 135 ℃. 4. The freezing point should be as low as possible. 5. Acid, alkali, sulfur, ash and other impurities in the lower the better, to try to avoid their insulating materials, wires, tanks and other corrosion. 6. The degree of oxidation can not be too high. The degree of oxidation is usually expressed in terms of acid value, which is the amount of potassium hydroxide (mg) required to absorb the free acid in 1 gram of oil. 7. Stability should not be too low, the stability of the acid value of the test is usually expressed in the sediment, which represents the ability of anti-aging oil.

Detailed explanation of series reactor selection difficult problem

Series reactor (hereinafter referred to as series resistance) is a parallel capacitor device (hereinafter referred to as the capacitor device or capacitor group) is one of the main components, which plays a limit capacitor bank (back to back) closing surge in power harmonic suppression, to prevent the capacitor Damage, and to avoid the capacitive device access to the harmonic harmonic over-amplification and resonance and so on an important role.However, string resistance and capacitor can not be arbitrarily combined, if not consider the capacitance device access to the actual situation of the grid, the "one size fits all" (Such as capacitors are equipped with a reactance of 5% to 6% of the string resistance), often counterproductive, leading to a serious amplification of harmonics and even resonance, endanger the safety of devices and systems.Because of the presence of oil immersed distribution transformer harmonics The complexity and randomness of the capacitive devices, and the difference of the structure and characteristics of the electric network in which the capacitive devices are located make the choice of the harmonic response and the series reactance rate of the capacitor devices a difficult problem and a research topic. However, with the deepening of the research work and the accumulation of practical experience, many consensus opinions or effective measures have been put forward, or some suggestions have been made for the design of string reactors in the design of capacitor installations. Lessons Learned. The string resistance has both the advantages of suppressing inrush current and harmonics, but also has its additional power loss and construction investment and operating costs of the shortcomings.Therefore, the new expansion of the capacitor device, Or has been put into operation of the capacitor device in the series of anti-selection program, the technical and economic comparison is necessary.This paper focuses on the part of the capacitor device engineering design followed the choice of 6% string anti-problem analysis, with a view to device construction and Operation has some benefits.

Transient Effect of Magnetic Saturation on Transformer

Magnetic saturation transient effect of the transformer Note that magnetic flux should be checked for saturation near minimum input voltage and maximum pulse width. As the input voltage is high, the pulse width will be narrowed, so the core is far from saturated. In a transient load, when the input voltage is high and the load current is small, if the load current suddenly increases, the control circuit immediately increases the pulse width to provide the supplemental power. In this way, the input voltage and pulse width are simultaneously maximized, even if for a short period of time, the single phase step down transformer will appear saturated, and cause out of control and failure. Here are some measures to avoid runaway. (1) transformer in accordance with high input, voltage, wide pulse design, the core work in low flux density and winding more primary winding. The disadvantage of this method is to reduce the efficiency of the transformer, increasing the size of the Amorphous Core Transformers weight. (2) the control circuit should be in the high sensitivity to determine the state of work, when the high input voltage appears to be able to quickly limit the pulse width, it is still safe value. (3) in the control circuit to improve performance, so that the switch in the current work cycle to quickly respond to control. UC1846 / UC1847 current mode control chip, can automatically achieve this limit action.

Power transformer type and characteristics

Power transformer type and characteristics of commonly used power transformer classification can be summarized as follows: (1) by the number of phases: (1) single-phase power transformer: for single-phase load and three-phase power transformer group. (2) three-phase power transformer: three-phase system for the rise and fall voltage. (2) by cooling: (1) dry power transformer: rely on air convection cooling, generally used for local lighting, electronic circuits and other small-capacity power transformers. (2) oil-immersed power transformers: rely on oil for cooling medium, such as oil from the cold, oil-immersed air-cooled, oil-immersed water, forced oil circulation. (3) by the use of points: (1) Power Transformer: transmission and distribution system for the rise and fall voltage. (2) Instrument 10kva single phase transformer: such as voltage transformers, current transformers, for measuring instruments and relay protection devices. (3) test transformer: can produce high voltage, high voltage test of electrical equipment. (4) special transformers: such as electric furnace transformers, rectifier transformers, transformers and so on. (4) according to the form of winding: (1) dual-winding transformer: used to connect the two power system voltage level. (2) three-winding transformer: generally used for power system regional substation, connecting three voltage levels. (3) auto-transformer: used to connect different voltage power system. Can also be used as an ordinary step-up or down after the transformer. (5) according to the core form: (1) core prefabricated compact transformer: for high voltage power transformer. (2) amorphous alloy transformer: Amorphous alloy core transformer is a new magnetic materials, no-load current decreased by about 80%, is the ideal energy-saving effect of distribution transformers, especially for rural power grids and developing areas Load rate is low. (3) shell-type transformers: for high-current special transformers, such as electric furnace transformers, welding transformers; or for electronic equipment and television, radio and other power transformers.