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Power Quality Inspection
It makes the components in the public power grid produce additional harmonic loss and reduces the efficiency of power generation, transmission and electrical equipment. When a large number of third harmonic flows through the neutral line, the line will overheat and even fire.Harmonic makes capacitors, cables and other equipment overheat, insulation aging, life shortened, and even damaged
It leads to the downtime of electronic equipment, computer system and automatic control production line, which leads to the disorder of system control function with voltage phase angle as control instruction，It causes the motor speed instability and affects the product quality. In serious cases, the microcomputer equipment can operate safely
It causes the trip of variable speed drive device, PLC damage, automatic control device misoperation, computer system malfunction and data loss, product quality off shelf and raw material loss caused by production line pause.The disordered start-up of equipment that causes disorder or interruption of production line and voltage drop is much more harmful and loss than the orderly recovery after planned power failure
When the transformer is in unbalanced operation, it will cause local overheating and reduce its service life. When the power supply line is in three-phase unbalanced system, the negative sequence current will produce additional loss and increase the line loss and voltage drop.For sensitive load, it may cause abnormal operation.
Machinery manufacturing industry case
Customers are large-scale manufacturing enterprises, with a large number of impact loads on the power side. During the production process, the plant management personnel found that the transformer and bus bar in the distribution station often had abnormal noise and vibration, and the capacitors in the two reactive power compensation cabinets were bulging and damaged.
（1）By checking the wiring mode of two reactive power compensation cabinets, it is found that the reactive power compensation capacitor is not equipped with reactor;
(2) The power quality of the incoming cabinet of the distribution station is detected, and the total harmonic distortion rate is increased due to the periodic impact load;
（3) Through the comparison before and after the reactive power compensation is put into operation, the harmonic current changes obviously, and the odd harmonics are amplified in varying degrees, especially the 11th and 13th harmonics.
（1）Find the hidden trouble of power supply and distribution system which has been bothering customers for a long time;
（2）To provide data reference and solutions for power quality harmonic control in later period;
（3）Enhance the customer's concern about power quality, including the introduction of power quality prevention and governance scheme for future construction, technical transformation and expansion, so as to ensure the power safety of the plant and reduce the failure rate of equipment.
Case study of building materials industry
The customer's equipment is mainly frequency conversion motor. There are a lot of harmonics in the 0.4kV bus, which leads to the reactor burning in the reactive power compensation cabinet and the bus heating seriously.
（1）The harmonic content on site has exceeded the national standard;
（2）The main harmonics are 5, 7, 11 and 13;
（3）The power factor is up to the standard.
（1）According to the harmonic content data in the test results, a detailed harmonic control scheme can be formulated;
（2）Provide the evaluation of the effect of power quality management after governance, and provide the basis for the completion acceptance of the power quality management project of customers.
