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Analysis of power quality in the petrochemical industry


2021-02-04

1. Introduction 

With the implementation of my country's strategy of building a resource-saving and environment-friendly society, the petrochemical industry is facing more severe situations and tasks in terms of resource protection, energy conservation, emission reduction, and safe production. The petrochemical industry has complex production technology, harsh operating conditions, and increasingly serious power quality problems. A little carelessness in the power system may cause serious safety accidents. How to improve power quality is essential to ensure the safe and stable operation of electrical equipment, improve the comprehensive energy utilization efficiency of the industry, reduce grid pollution, and implement safe production.

2. Indicators for measuring power quality in the petrochemical industry

    Compared with other industries, the power quality indicators of the petrochemical industry are no different. However, the complexity of its own grid system determines that its requirements for power quality are more stringent. The indicators for measuring power quality in the petrochemical industry mainly include the following points:

Voltage deviation index

The change of reactive load causes the voltage of the power system to deviate far from its rated voltage, among which lamps such as motors and lighting are susceptible to voltage deviations.

Flicker and fluctuation of voltage

Caused by changes in active or reactive power generated by impact loads such as electric arc furnaces, arc welders, and rolling mills.

Harmonics of the grid

    The most fundamental cause of harmonics when non-linear loads are generated. The sudden change of the load terminal voltage and the current in the power grid are both important factors that cause the generation of harmonics.

Unbalance of three-phase voltage

Large-capacity asymmetric loads and harmonic components in the grid system will cause negative sequence components in the grid, which are the main factors that cause three-phase imbalance.

3. Power quality analysis in petrochemical industry

    The petrochemical industry has a long production line, a wide range of areas, a high degree of automation, and a degree of correlation between complex devices. Due to production needs, there are a large number of fast-changing shock loads, and the composition of electrical loads has also undergone qualitative changes. The access of a large number of non-linear loads inevitably produces many power problems: voltage flicker and fluctuation, low power factor, excessive reactive power consumption, harmonic interference, etc. Among them, the problem of harmonic interference is the most concerned issue of power quality in the petrochemical industry.

    In the actual power supply system, due to the existence of non-linear loads, when the current flows through the load that is not linear with the applied voltage, a non-sine wave current is formed. Sudden changes in current and load terminal voltage will cause the generation of harmonics.

    The main harmonic sources are: variable frequency speed regulation device of pump, uninterruptible power supply device, motor soft start equipment, new type of lighting (energy-saving lamp, fluorescent lamp with electronic ballast).

    The harmonic hazards in the power grid are manifested in the following aspects:

    3.1) Grids polluted by harmonics have caused relatively increased losses in transmission and distribution lines, motors, and transformers, thereby increasing energy consumption;

    3.2) The skin effect of wires and cables becomes larger, which accelerates the aging of the insulation layer and reduces the utilization rate of the cables;

    3.3) The magnetic induction circulating current of the iron core of the machine increases, which increases the power consumption of the equipment, and the life of the equipment is relatively shortened; in severe cases, the machine resonates, the motor speed is unstable, and the motor burns;

    3.4) The power system relay protection is started by mistake, tripped by mistake, refused to operate and damaged, which usually causes accidents or enlarged power outages, threatening the safe and reliable operation of the power system;

    3.5) The computer, data transmission and automatic control system data are lost, the display screen is distorted, malfunctions, components are damaged, and the accuracy of system file processing is reduced.

1. Introduction 

With the implementation of my country's strategy of building a resource-saving and environment-friendly society, the petrochemical industry is facing more severe situations and tasks in terms of resource protection, energy conservation, emission reduction, and safe production. The petrochemical industry has complex production technology, harsh operating conditions, and increasingly serious power quality problems. A little carelessness in the power system may cause serious safety accidents. How to improve power quality is essential to ensure the safe and stable operation of electrical equipment, improve the comprehensive energy utilization efficiency of the industry, reduce grid pollution, and implement safe production.

2. Indicators for measuring power quality in the petrochemical industry

    Compared with other industries, the power quality indicators of the petrochemical industry are no different. However, the complexity of its own grid system determines that its requirements for power quality are more stringent. The indicators for measuring power quality in the petrochemical industry mainly include the following points:

Voltage deviation index

The change of reactive load causes the voltage of the power system to deviate far from its rated voltage, among which lamps such as motors and lighting are susceptible to voltage deviations.

Flicker and fluctuation of voltage

Caused by changes in active or reactive power generated by impact loads such as electric arc furnaces, arc welders, and rolling mills.

Harmonics of the grid

    The most fundamental cause of harmonics when non-linear loads are generated. The sudden change of the load terminal voltage and the current in the power grid are both important factors that cause the generation of harmonics.

Unbalance of three-phase voltage

Large-capacity asymmetric loads and harmonic components in the grid system will cause negative sequence components in the grid, which are the main factors that cause three-phase imbalance.

3. Power quality analysis in petrochemical industry

    The petrochemical industry has a long production line, a wide range of areas, a high degree of automation, and a degree of correlation between complex devices. Due to production needs, there are a large number of fast-changing shock loads, and the composition of electrical loads has also undergone qualitative changes. The access of a large number of non-linear loads inevitably produces many power problems: voltage flicker and fluctuation, low power factor, excessive reactive power consumption, harmonic interference, etc. Among them, the problem of harmonic interference is the most concerned issue of power quality in the petrochemical industry.

    In the actual power supply system, due to the existence of non-linear loads, when the current flows through the load that is not linear with the applied voltage, a non-sine wave current is formed. Sudden changes in current and load terminal voltage will cause the generation of harmonics.

    The main harmonic sources are: variable frequency speed regulation device of pump, uninterruptible power supply device, motor soft start equipment, new type of lighting (energy-saving lamp, fluorescent lamp with electronic ballast).

    The harmonic hazards in the power grid are manifested in the following aspects:

    3.1) Grids polluted by harmonics have caused relatively increased losses in transmission and distribution lines, motors, and transformers, thereby increasing energy consumption;

    3.2) The skin effect of wires and cables becomes larger, which accelerates the aging of the insulation layer and reduces the utilization rate of the cables;

    3.3) The magnetic induction circulating current of the iron core of the machine increases, which increases the power consumption of the equipment, and the life of the equipment is relatively shortened; in severe cases, the machine resonates, the motor speed is unstable, and the motor burns;

    3.4) The power system relay protection is started by mistake, tripped by mistake, refused to operate and damaged, which usually causes accidents or enlarged power outages, threatening the safe and reliable operation of the power system;

    3.5) The computer, data transmission and automatic control system data are lost, the display screen is distorted, malfunctions, components are damaged, and the accuracy of system file processing is reduced.