Discussion on the ways to improve the voltage qual

2022-08-17
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Talking about the ways to improve the voltage quality of rural low-voltage electricity

1 the current situation of low-voltage electricity

in recent years, our county has done some work to improve the voltage quality in the construction and management of agriculture, and solved the problem of low voltage qualification rate in some areas. However, due to the influence of historical objective conditions and insufficient subjective attention, the voltage quality of farmers in our county is still generally unqualified. The main reasons are that the electrical structure is unreasonable, the conductor section is thin, the circuitous line is long, the power supply radius is large, the distribution and transformation equipment is old and aging, the renewal speed is slow, and the low-voltage reactive power compensation lags behind, etc. in addition, most of these assets are collective assets, and the vast majority of rural economy is weak, with little or no self accumulation, resulting in the inability to invest in rural power transformation

based on the above reasons and current situation, it is imperative to transform rural low-voltage power and improve the voltage quality of users

2 ways to improve the voltage quality

2.1 change the circuitous line, eliminate the neck line, and shorten the power supply radius

because the power department has neglected the management of rural power consumption for many years, the neck line and circuitous line are more common in rural power, but also extend the power supply radius, and the terminal voltage quality is poor. In this regard, according to the spirit of the relevant documents of the higher authorities, our bureau submitted the "suggestions on the reform of rural electricity system" to the county government in 1992 and was approved. In the past, the township (town) electricity management station was in the charge of the township (town) government, and the management mode of the business guidance of the power supply bureau was the system in which the township (town) electricity management station was directly led by the power supply bureau, supplemented by the township (town) government, which implemented the unified management of people, finance and property for the township station, which greatly mobilized the enthusiasm of the personnel of the township (town) electricity management station, At the same time, under the leadership of the power supply bureau, the rural low-voltage power has been transformed. According to the specific situation of our county and the increasing annual power consumption, the route of the line is redesigned, and the export proportion of Rural emerging countries will also be greatly increased. 50mm2 conductor, 10m low-voltage pole and one low-voltage line for two rows of houses are used on the export trunk line of the substation, so as to eliminate circuitous lines and necklines, shorten the power supply radius, and make the voltage of end users meet the relevant requirements

2.2 reasonably select transformer taps for voltage adjustment

most rural distribution transformers are comprehensively utilized, and one transformer is used for drainage and irrigation, industrial and sideline industries, lighting, etc. In busy farming season, the voltage decreases due to the increase of agricultural load, which makes it difficult to start fluorescent lamps and motors. Therefore, it is an important measure to reasonably adjust the primary side voltage of small capacity (above 100kV. A) distribution transformer in time to ensure the healthy, safe and economic operation of users' electrical equipment

the voltage adjustment of small capacity distribution transformer must be carried out by cutting off the power supply. After taking safety measures, adjust the tap changer, that is, change the position of the tap. After adjustment, the DC resistance of each phase shall be measured with an electric bridge or multimeter, and the difference value shall not exceed 2%

2.3 adopt the principle of grading compensation and local balance to compensate the reactive power of low-voltage electricity, and reduce the loss and regulate the voltage

in recent years, our county has installed parallel capacitors on the 10kV bus and 10kV line of 35kV substation, which realizes the centralized compensation of substation and the decentralized compensation of 10kV line, and improves the power factor of 10kV electricity. However, from the current configuration of reactive power compensation, the proportion of high-voltage compensation is large, and the proportion of low-voltage compensation is relatively small. In rural low-voltage power, only some industrial users above 100kV. A have installed shunt capacitors to play an exemplary role in utilization, while a large number of agricultural transformers and electric machines are basically not compensated. Therefore, it is imperative to carry out graded compensation for distribution transformers, low-voltage lines and agricultural motors

2.4 reactive power compensation (follow-up compensation) for distribution transformers

according to the load characteristics of rural low-voltage electricity, reactive power compensation should be carried out for distribution transformers, capacitors should be connected to the low-voltage bus in parallel, and automatic switching devices should be installed, which can automatically switch on and off the capacity of capacitors according to the size of reactive power, so as to avoid over compensation, reverse reactive power to the system, and over-voltage, which threatens the safety of electrical equipment and capacitors

the practice in Shimen town of our county proves that the follower compensation can automatically compensate the reactive power according to the reactive power loss of the distribution transformer, making the cos of the distribution transformer φ It reaches above 0.95, the working voltage decreases by 25% ~ 30%, the reactive power loss decreases by 80%, the terminal voltage is increased, and the delivery task of the first batch of sample vehicles is successfully completed. The efficiency of electrical equipment is increased by 20%, and the electricity is saved by 8% ~ 10%

2.5 distribution line compensation

the reactive power compensation on the distribution line is matched with the automatic device to avoid over compensation and under compensation, which will play a certain compensation role after selecting the best capacity and the best compensation point

2.6 compensation for motor (random compensation)

random compensation for motor can balance reactive load locally, but its molecular composition means that it can prevent the growth of fungi and bacteria in food and inhibit dynamic reactive power, so as to reduce the reactive power transmitted by the distribution line above the installation point, and the compensation effect is the best. In order to prevent self excitation and overvoltage after the motor is disconnected from the power supply, the compensation capacity should not be too large, and the capacitor discharge current should not be greater than the no-load current of the motor

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