The power quality problems in the power supply system of the coal industry include large voltage deviation, voltage fluctuation and flicker, high harmonic content, low power factor, and large loss.

Load analysis in coal industry

1. Hoist

The hoist has a large installed power and accounts for a significant proportion of the total power supply load of the mine. As a high-power, frequent start, periodic shock load and the use of silicon rectifier device, the hoist causes great reactive power impact and high harmonic pollution to the power grid. Therefore, high-power hoists put forward higher requirements for the capacity and stability of the power supply grid.

2. Long-distance transmission lines

In the process of coal mining, there are a large number of roadway boring equipment, ventilation equipment, running lights and electrical equipment are applied underground, in the mining process of non-open-pit coal mine, a long transmission line is required to provide power for underground equipment, long-distance power transmission brings high energy consumption, resulting in low terminal voltage.

3. Frequency converter and soft starter

Frequency converters or soft starters are configured to improve start-up shock and operational energy savings. Due to the use of frequency converters, 6k±1 harmonics are generally generated.

Characteristics of harmonics in the coal mining industry

Due to the widespread use of inverter equipment in mine hoist systems, frequency converters have become the main source of harmonics. In addition to the inverter, UPS, the load in the coal mine power distribution system also has sensitive equipment, such as: gas monitoring, video, audio monitoring, mine digitization and personnel positioning, rescue system, etc., the harmonics generated by the frequency converter will produce harmonic pollution to these sensitive equipment systems through conduction, induction, etc., which in turn affects the normal operation of these sensitive equipment, and at the same time has a negative impact on the accuracy and service life of sensitive equipment, safe operation, and brings great hidden dangers to the economic benefits and safety production of coal mines.

Hazards caused

1. Continuous capacity increase, resulting in overload of transformers or systems, resulting in fire, damage to transformers or power distribution systems.

2. The loss of equipment and lines increases, destroys insulation, reduces service life, and seriously causes fire, endangering personal safety.

3. Cause the occurrence of tight stop faults such as overcurrent and undervoltage in the power distribution system, which affects mine production.

4. Reward and punish electricity fees according to the "Measures for Adjusting Electricity Charges by Power Factor".

Solution

Application Case

1. Application of BW-SVG in Yangmei No. 2 Mine Coal Preparation Plant

2. Application of BW-APF in Yangmei No. 2 Mine Coal Preparation Plant