Yihai Kerry's oilseeds and grain business processes soybeans, rapeseed, peanuts, sunflower seeds, sesame seeds, cottonseeds, and grains (wheat and rice) into edible oil, feed mash, rice flour, cereals, and soy milk powder related products.
In the production process, a large amount of electric energy is consumed, so the electricity cost is always high, and the power quality condition is also known by the management manufacturers or the power supply bureau. There is no professional power quality analyzer tool to verify. The entire production process cannot master the power quality status, and it is even more difficult to find a suitable way to save power.
Power transformers and distribution lines are the most energy intensive in the plant's power distribution system. Due to the changes in market demand and changes in the production process of the factory, there is usually a situation in which the capacity of the power transformer according to the planning equipment does not match the practical load, for example, the transformer has a large capacity, the load rate is low, the transformer loss is large, and the distribution line thickness and length are short. Unreasonable and unstandardized, it also caused a significant increase in line loss.
Based on the above test problems, the customer does not have a corresponding detection method, including power, harmonics, line loss, power factor and other functions that are mainly concerned.
Fluke engineers personally took the Fluke three-phase power quality analyzer Fluke 435-II to the factory for on-site power monitoring. Fluke engineers put on professional work clothes, wear safety helmets, high-voltage arc-proof masks, and 10000 V high-voltage insulated gloves, and carried out tests on voltage and current frequency, power, harmonics, and power factor that customers care about in detail.
The on-site voltage is 380 V and the current is over 2,000 amps. The distance between the high-voltage busbars is very close, and the current loops are more dangerous. The busbars are installed at the bottom of the cabinet half a meter deep from the ground, which makes testing difficult (see the figure below). After the test was completed, the Fluke 435-II generated a detailed power quality report, and customers praised the features of our instruments.
According to Fluke's special report software, the voltage harmonics report is as follows: The total voltage distortion rate is 2.2%, which is in accordance with the national standard 5%, and the power factor is 0.97. This indicator is good, and the customer informed the power supply bureau that there will be targeted rewards. .
The following figure shows the current harmonics. The 3rd and 5th harmonics are slightly exceeded. Harmonics usually cause a large amount of wasted electrical energy and cause significant economic losses. The reason for this harmonic generation may be due to unbalanced three-phase or non-linear load, which will cause certain pollution to the power grid system.
harmonic
The main causes of harmonics are: due to the sinusoidal voltage being applied to a non-linear load, the fundamental wave current is distorted to generate harmonics. The main non-linear load is UPS, switching power supply, rectifier, frequency converter, inverter and so on.
Harmonic currents are the root cause of all harmonic problems. Harmonic voltages are also caused by harmonic currents. Therefore, when studying the harm caused by harmonics, it mainly refers to the harm of harmonic currents.
First: Causes the cable to overheat
Harmonic currents flowing through the cable can cause the cable to overheat. The cause of this phenomenon is the skin effect of the alternating current. The skin effect is a physical phenomenon in which the surface of the conductor is concentrated when the alternating current flows through the conductor. The higher the frequency of the current, the more concentrated the current is on the surface of the conductor. Due to the skin effect, when a harmonic current with a relatively high frequency flows through the conductor, the effective cross-sectional area of ​​the conductor is smaller than the actual cross-sectional area of ​​the conductor. A small cross-sectional area means more resistance, which means more heat. When higher harmonic currents flow through a conductor, the conductor exhibits a greater resistance than the fundamental current, so that harmonic currents of the same magnitude produce more heat than the fundamental current.
Second: cause the transformer to overheat
Harmonic currents flowing through the transformer can cause the transformer to emit extra heat, causing the transformer to overheat when it does not reach the rated power, resulting in a decrease in the transformer's actual capacity.
Third: cause damage to the reactive power compensation device
The influence of harmonic currents on reactive power compensation devices is also very common, which has actually become an unavoidable problem for enterprises to carry out energy-saving technological transformation. In the energy-saving transformation, a large number of inverters are used, and the inverter generates severe harmonic currents.
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