Analysis and improvement of power quality of cement equipment upgrade
Date：2019-08-26 16:00 Source：cementepcViews:
The size of system voltage deviation, voltage three-phase unbalance degree and the reliability of power supply have important influence on the safe operation and service life of electrical equipment.This paper mainly analyzes the causes of voltage deviation, voltage three-phase unbalance and power supply reliability in cement plant and corresponding improvement measures.
1. Supply voltage deviation
1.1 causes and hazards of voltage deviation:
When the system is running at any given time, each workshop reactive power supplied by the system demand of reactive power and reactive power should be equal, but in the cement plant power system load may change at any time, factors such as fault in power system operation will cause the imbalance of power plant, the system reactive power imbalance means that there will be a lot of reactive power flows through power lines and transformers, due to the line and transformer impedance, the resulting line and transformer terminal voltage difference.Power supply and distribution line transmission distance is too long, transmission capacity is too large, resulting in too small cross section and other factors will increase the line voltage loss, resulting in voltage deviation.
1.2 measures to improve voltage deviation:
Change line parameters to reduce voltage loss.Reducing the resistance or reactance of the line can reduce the voltage loss of the line, so as to increase the terminal voltage of the line and achieve the purpose of voltage regulation.Therefore, in the design of power plane layout of cement production line, the best cable laying path should be designed for each electrical equipment as far as possible, and the cable length should be reduced as far as possible. For electrical equipment far away from the distribution cabinet, slightly larger cables than normal current carrying conditions should be selected.
Change the transformer ratio.According to the concrete situation of cement factory, choose suitable tap, make the output voltage of transformer change in the range of ±5% rated voltage, so as to get the suitable output voltage of transformer.
Equipped with adequate reactive power supply.For cement mill, high-voltage motor with power over 1000kW, such as roller press, should be equipped with stationary camera for each motor.For the low-voltage cabinet in the workshop, a reasonable reactive power capacitor compensation device should be configured according to the calculation.
2 three-phase voltage imbalance
2.1 causes and hazards of unbalance in three phases:
Cement power supply system three - phase imbalance can be divided into two categories, one is accident imbalance, the other is normal imbalance.Accidental imbalance is caused by various faults, such as single-phase grounding short circuit or two-phase short circuit.Normal unbalance is a three-phase unbalance of the power system caused by the unbalance of power lines or power links in the normal operation mode.For the long-distance transmission line of cement plant, the reactance of the line is far greater than the resistance of the line.When the three-phase wires are arranged horizontally or vertically, the flux chains intersected by the wires on both sides are larger than the flux chains of the intermediate wires, so the three-phase reactance is not equal, so whether the three-phase reactance is equal or not directly determines whether the power supply line is balanced.The unbalance of power supply is mainly caused by unsymmetrical three-phase load.
2.2 measures to improve three-phase imbalance:
The asymmetrical load is distributed in three phases so that the load of each phase is balanced as far as possible.For multiple single-phase loads with large capacity, the active power and reactive power should be fully calculated, so that the load distributed in the three phases can not differ as much as possible.
When the single-phase load capacity is very large, the asymmetric load is supplied by a single transformer.
For long distance and large capacity feeders, for example, when the total drop is far away from a transformer in the plant area, try to use three-core cables to avoid the three-phase imbalance of power lines caused by the uneven reactance distribution of single-core cables.
To avoid the possible loss caused by the three phase unbalance, install arc extinguishing device.
3.Supply interruption and supply reliability
3.1 causes of power supply interruption and hazards of power supply interruption:
The causes of power supply interruption of cement plant are various, mainly divided into the following categories, one is due to rats, snakes and other small animals into the distribution cabinet, causing an accident of power supply interruption of the original phase short circuit;The other is that some operators are not familiar with the relevant operating rules and regulations, or the supervisor's carelessness, thus causing accidents and causing power failure;There is also a lightning strike, lightning and other equipment protection actions, causing system accidents.
The operation of the cement production line with continuity, because outages caused by the production line stop jumping to cement enterprises cement production, cement quality to reduce the serious consequences, especially when the cement sales season, cement supply, caused by the loss is incalculable, and cement enterprise reputation and image will be affected by the bad.So it is very important to ensure the reliability and continuity of power supply.
3.2 measures to improve the reliability of power supply:
Security doors are installed in the distribution rooms to increase the threshold to prevent small animals from tampering.Due to the cat, mouse and other tamper into the distribution cabinet caused by the short circuit fault has been common, some production lines even more than once similar incidents, causing huge economic losses to cement enterprises.
Strengthen the pre-job training and business skills training of operation personnel, and resolutely carry out the work with certificates. At the same time, we should also strengthen the education of production safety, constantly improve the technical level of operation personnel and the ability to deal with accidents quickly.
Formulate elaborate emergency measures for accidents.Pay close attention to the weather change, do the maintenance work of the electrical equipment in advance, reduce the loss caused by the accident to the minimum.
To sum up, the size of system voltage deviation, voltage three-phase unbalance degree and the quality of power supply reliability have an important impact on the safe operation and service life of electrical equipment, but also directly related to the cement plant power system itself safety and stability and economic operation.The basic tasks of electrical operation and maintenance in cement plant are to ensure the voltage deviation at all points within the allowable range, to ensure the three-phase voltage balance and to improve the power supply reliability of the system.Jiangsu LVSSN can provide high quality and efficient cement plant construction, please consult our customer service or leave a message to us, we will reply to you as soon as possible.