Subterranean LED «ray of light»
Tunnels are unique engineering structures. Very often they operate in continuous mode 24/7. This means they should maintain superior standards as to reliability and safety of materials used during construction and operation. Careful choice and competent arrangement of luminaires in tunnels are very important because artificial illumination is the only source of light and the main safety condition at any time of day.
There are several factors for choosing luminaires for metro tunnels. For instance, illumination norm should be not less than 10 lx for a completed section of the tunnel and not less than 50 lx for equipment maintenance. Furthermore, light sources for tunnels should have long durability without losing their photometric characteristics, and high protection from dust and moisture (not less than IP 54).
In most cases conventional incandescent lamps are used for metro tunnel illumination. Such sources have a number of disadvantages. Low luminous efficiency and lack of any protection makes them very fragile in the operating conditions of metro tunnels: the lamp gathers dust and dirt that heat and then dry, the cap sticks to the socket, which makes replacement of the lamp difficult. As a result, despite low cost, usual incandescent lamps turn out to be inefficient and expensive light sources for underground objects.
LED luminaires are superseding conventional light sources. They allow maximum illumination of tunnels to be achieved with maximum cost savings. These luminaires are protected from overheating and short circuits. Their use enables energy consumption to be reduced and the risk of electricity mains overload eliminated. High quality and reliable industrial luminaires should provide ultimate durability and record stability due to their ability to operate in continuous mode and tough conditions of vibrations and dust. They also have superior luminous characteristics, and give an opportunity to save on illumination due to the low energy consumption. And last, but not least, the luminaires are able to operate almost without maintenance thanks to high protection from dust and humidity (usually, IP 67). The calculated duration of their continuous operation is not less than 50 thousand hours, which is more than 12 years. LED units manufactured in Russia correspond to the regulations for illumination of tunnels. These high quality luminaires are not manufactured in China and don't include any Chinese components. The vivid example that testifies the efficiency of LED luminaires in metro tunnels is AtomSvet long-term project, implemented for Mosmetrostroy OJSC.
Work on this project began in November 2012. Mosmetrostroy faced serious problems with illumination of the construction site of the main line tunnel because of high humidity. All conventional light sources failed after a while. For that reason a high-grade substitute had to be found. The key factor for choosing new luminaires became the reliability of the equipment and its failure-free operation under conditions of high humidity. AtomSvet supplied four low voltage 22 W luminaires AtomSvet Plant series LV for test operation. The trial lasted for four months during which the luminaires had proved themselves in the best way.
Technical parameters of AtomSvet Plant LV luminaire allow the required luminous flux to be obtained at low energy consumption. The luminaire housing is made of extruded heat-dissipating aluminum profile protected by an oxide coating. The dome is made of special polycarbonate Makrolon LED, produced by the Bayer company, with a minimum light transmission coefficient of 87%.
First of all, the main features of AtomSvet low voltage luminaires is high reliability and stable operation in adverse conditions, such as wide range of possible input voltages 12–50 VAC, wide range of operating temperatures –60…+60 °С and high humidity. It became possible to achieve these superior characteristics due to implementation of the latest developments in the design of LED luminaires, more specifically:
- high efficiency Nichia diodes in operation modes of 700 mA;
- new circuit design of the control driver, which allows simultaneous operation in increasing and decreasing output modes at input voltage variations in the range of 12–50 VAC with high efficiency coefficient >80%; it enables continuous operation of the diodes;
- new technology of manufacturing the “ALOX” heat-dissipating plane which can increase the heat conduction coefficient almost ten times in comparison with conventional methods. This technology enables the manufacture of the diode control driver in one structure (on one common board), which significantly improved heat characteristics of circuit components, simplified the luminaires assembly process, and consequently, reduced labour and material consumption for the end product.
- by filling the main operating components and luminaire mechanisms with a compound they have ingress protection rating against environmental exposure of not less than IP67.
Such filling technology was successfully tested with time and during certification on environmental exposure when manufacturing the Plant series of luminaires. On completion of testing of lighting products from various suppliers, a pilot project startup began at SMU-1 Metrostroy and over 400 low voltage luminaires manufactured by AtomSvet were purchased. Over several months the electrical supervisor of SMU not only performed the test operation of the luminaires, but also carried out measurements, according to which an energy saving evaluation was made. On completion of the tests the conclusion was made, that the payback period for AtomSvet luminaires is approximately 7 months in a tunnel section of 1.3 km, while cost saving at the same section had reached about 2.5 mln. rubles.
“Considering that transformers in the 300 m section are arranged in a close proximity with incandescent lamps, and supply the voltage of 36 V for them, significant voltage drop occurs at the end of the tunnel” - says Sergey Katin, the manager of AtomSvet, LLC project on low voltage. “To ensure that lamps provide sufficient illumination throughout the tunnel, technical personnel had increased output voltage on the construction site up to 45 V, which led to additional energy consumption. When using AtomSvet luminaires in this section the voltage drop was minimal because they consume 3.5 times less energy than incandescent lamps. It should be noted that AtomSvet released a batch of luminaires according to special project requirements, with increased voltage threshold up to 50 V when the standard is 36 V.”
This measure provided complete compliance with illumination regulations and contributed to money and energy saving. In case of incandescent lamps usage Mosmetrostoy would have to arrange intersection transformers every 300 metres with an input voltage of 45 V. Thanks to implementation of low voltage AtomSvet luminaires intersection transformers are arranged every 450 m with an input voltage of 36 V.
“In July 2013 during the construction of branch line in “Likhobory” depot over 200 LED AtomSvet Plant LV luminaires were installed in an operating voltage mains of 36 V|” — comments Igor Rudkov, the electrical supervisor of SMU-1 Metrostoy. “According to results of operation the illumination increased to 200 lx (at 50 lx required). In shadowed areas it amounted to at least 100 lx. Besides, power consumption was reduced by a factor of five and consequently, energy consumption decreased. According to our calculations, cost savings for energy consumption of the lighting system for the tunnel 5.6 km in length on the Lyublinsko-Dmitrovskaya metro branch line in the end of construction will reach 9.3 mln. rubles, if we use AtomSvet LED luminaires.”
The examples show that AtomSvet LED luminaires are a reliable substitute for conventional light sources, and what is most important, help to save energy and money. Thus far, over 800 AtomSvet Plant LV 31 W luminaires have been acquired for Mosmetrostroy’s needs.
Future plans are to continue and extend cooperation with these two companies, and not only concerning low voltage equipment implementation. AtomSvet has already equipped a number of metro construction sites with its standard AtomSvet Plant 220 V luminaires, as secure lighting and area illumination, instead of DRL and HMI lamps.
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