Co-Generation Energy Solutions for MiningBy Andrea Villar | Mon, 04/20/2020 - 12:38
Miners need to work round-the-clock because stopping production for just a few minutes can result in mammoth losses. Solutions for securing a reliable power supply have come to the industry forefront. Energy self-generation is seen as a promising alternative. But equipment normally used in mines, such as power shovels, have special electricity requirements that must be addressed for self-generation to really work.
Companies like Técnica Salgar focus on technology for bridging the gap between power suppliers and consumers. “CFE delivers energy in a practically pure sine wave. When it goes through electronic processes that imply rectification, which is done to mining equipment to increase productivity, harmonics are created,” says Bernardo Salcido, Técnica Salgar’s Director General. “Harmonics are a voltage or current at a multiple of the fundamental frequency of the system. They come into existence when rectifiers convert alternating current, which periodically reverses direction, to direct current, which flows in only one direction.” This produces many problems. Harmonic frequencies in the power grid are a frequent cause of power-quality problems, which results in an increased equipment and conductor heating, misfiring in variable speed drives and torque pulsations in motors.
To solve this problem, power must be cleaned and made suitable for use in mining equipment. “Our harmonic current filters clean the current and make it safe to use. In addition, our equipment is movable, by means of a crane, and can be located next to the shovels throughout the mine. Our filters clean the energy and make it safe to use.” Técnica Salgar’s filters are connected to the circuit that feeds all the equipment in the mine. Shovels need current to be filtered in order to work properly. In addition, says Salcido, CFE does not allow distorting alternating current. “There are fines against it because it can damage the grid. This is stated in the law, and its latest version went into effect in 2019. This regulation contains the minimum technical requirements necessary to ensure the efficient development of all processes associated with the national electric system.”
The law regulating Mexico’s power grid requires high and medium voltage companies in the industrial and commercial sectors to report an electrical diagnosis of their facilities. If a problem is found, they must come up with a work plan to correct it. Everything must be reported to CRE, which can send an inspector to verify compliance. If a company commits a fault that can potentially generate a serious problem, CRE can fine it 2-10 percent of its gross income from the previous year. Therefore, as Salcido says, “harmonic current filters are absolutely indispensable in mining operations. Técnica Salgar helps miners do more with less kW. By filtering out harmonics, engines become more efficient. It is like finetuning a car so that it needs less gas to run faster. And at the same time, we make sure the company does not run into trouble with the authorities,” explains Salcido.
Miners that want to generate their own power also face the harmonics issue. The most common situation is that companies enter a co-generation scheme with CFE. “As companies cannot take the risk of their own generators failing, they work out ways to co-generate with CFE. Whenever they generate extra, they sell it to CFE. Nevertheless, companies need to carefully evaluate if this will really be beneficial for them, as many other expenses become necessary to keep the generators,” says Salcido. Even so, when companies sell energy to CFE, it has to be cleaned of harmonics because it is a rectified current moving from electronic to electric systems. Therefore, Técnica Salgar’s harmonic filters are crucial for co-generating companies.
Técnica Salgar also manufactures current-limiting reactors that reduce short-circuit currents resulting from plant expansions and power-source additions. The resulting currents can be adequately handled by existing distribution equipment. In this process, CFE’s power lines have a set short-circuit capacity that has to be equaled by the co-generating party. Current-limiting reactors are necessary to this end.
A further point that is important in co-generation schemes is that, in order to supply power to CFE, companies need to provide a little extra voltage. For this purpose, a capacitor bank is required. This is a group of several capacitors of the same rating that are connected in a series to store electrical energy. The resulting bank is then used to counteract or correct a power factor lag or phase shift in an alternating current power supply. “As the quality of generating equipment improves, the industry-wide tendency to co-generation and self-generation will gain strength. Técnica Salgar’s equipment is essential for successfully navigating this emerging trend,” concludes Salcido.