Basic information of users
A petrochemical plant mainly produces gas products. The electrical equipment used by the company is a soft starter driver load, and the distribution transformer is 2500 kVA. The power supply system diagram is as follows:
Actual operating data
The total power of the frequency converter of the 2500KVA transformer is 1860KVA, the average power factor is PF=0.8, and the working current is 2400-2700A.
Power System Situation Analysis
The key to the inverter power supply is the load of the rectifier inverter power supply driver, which belongs to the discrete system load. Equipment generates a lot of harmonics during the operation process, which is a typical harmonic source. The harmonic current introduced into the power grid will cause harmonic working voltage on the characteristic impedance of the power grid, resulting in fluctuations in the working voltage and current of the power grid, endangering the quality and operation safety of the power supply system, increasing the line loss and working voltage error, and causing serious damage to the power grid and processing plants. Its own electrical equipment, especially the traditional reactive power compensation cabinet will cause adverse effects, and it is easy to cause harmonic vibration, causing damage to electrical equipment such as capacitor cabinets. Therefore, a low-voltage reactive power compensation filter with harmonic suppression function should be selected to suppress system harmonics, compensate reactive loads, and improve power factor.
Filter reactive power compensation treatment plan
Governance goals
Filter compensation devices are designed to meet regulatory requirements for suppression of harmonics and reactive power.
Under the 0.4KV system operation mode, after the filter compensation equipment leaves the factory, the harmonic suppression is above 0.92 on average monthly power factor.
Do not cause harmonic resonance or resonance overvoltage and overcurrent due to input filter compensation branch.
Design Follows Standards
Power quality Public grid harmonics GB/T14519-1993
Power quality Voltage fluctuation and flicker GB12326-2000
General technical conditions of low-voltage reactive power compensation device GB/T 15576-1995
Low-voltage reactive power compensation device JB/T 7115-1993
Reactive power compensation technical conditions JB/T9663-1999 “Low-voltage reactive power automatic compensation controller” from the high-order harmonic current limit value of low-voltage power and electronic equipment
Electrotechnical terms Power capacitors GB/T 2900.16-1996
Low voltage shunt capacitor GB/T 3983.1-1989
Reactor GB10229-88
Reactor IEC 289-88
Low voltage reactive power compensation
Controller order technical conditions DL/T597-1996
Low-voltage electrical enclosure protection grade GB5013.1-1997
Low-voltage switchgear and controlgear assemblies
Design ideas
According to the actual situation of the enterprise, our company comprehensively considers the load power factor and harmonic suppression in the filter invalid compensation of the inverter, and installs the filter invalid compensation device on the 0.4KV low-voltage side of the enterprise transformer, which suppresses the harmonics and compensates for the increase in reactive power. power factor.
During the operation of the frequency converter, it will generate 5 times of 250HZ, 7 times of 350HZ and other high-order harmonics. Therefore, when designing the filter ineffective compensation of the inverter, it should be ensured that the filter compensation branch circuit can effectively suppress the harmonics and compensate the ineffective power for frequencies above 250HZ and 350HZ to improve the power factor.
design assignment
The comprehensive power factor of the inverter power supply production line matched with each 2500 kVA transformer is compensated from 0.8 to about 0.92. Filtration device compensation equipment must be installed with a capacity of 900 kWh. The capacities of 11 groups of phase-splitting are matched to the windings on the bottom voltage side of the transformer to be connected and disconnected automatically. The classification adjustment capacity is 45KVAR, which can meet various power requirements of soft starters and production lines. This type of design fully guarantees that the adjusted power factor is higher than 0.95.
Effect analysis after installation of filter compensation
In June 2011, the inverter filter reactive power compensation device was installed and put into operation. The device automatically tracks the load change of the inverter, immediately suppresses the high-order pulse current to compensate the reactive load, and improves the power factor. details as following:
After the filter compensation device is put into use, the power factor change curve is about 0.98 (the raised part is about 0.8 when the filter compensation device is removed)
Load operation
The operating current of the 2500KVA transformer is reduced from 2700A to 2300A, and the reduction rate is 15%. After compensation, the power loss reduction value is WT=△Pd*(S1/S2)2*τ*[1-(cosφ1/cosφ2)2]=24×{(0.85×2000)/2000}2×0.4≈16(kw h) In the formula, Pd is the short-circuit loss of the transformer, which is 24KW, and the annual saving of electricity expenses is 16*20*30*10*0.7*2=134,000 yuan (based on working 20 hours a day, 30 days a month, and 10 months a year , 0.7 yuan per kWh).
power factor situation
The company’s comprehensive power factor has increased from 0.8 to 0.95 this month, and the power factor will be maintained at 0.96-0.98 in the next month, and the reward will be increased by 5000-6000 yuan in January.
In general, the low-voltage reactive power compensation of the soft starter filter has a very good ability to suppress pulse current and compensate reactive power, solve the problem of reactive power punishment of the company, increase the output volume of the transformer, and reduce the active power The additional consumption of the product increased the output, brought obvious economic benefits to the company, and recovered the customer’s investment within one year. Therefore, the soft starter filter reactive power compensation produced by the company is very satisfactory, and will attract many customers in the future.
Post time: Apr-14-2023