Use safety device of solar photovoltaic power generation system

Photovoltaic power station generally installed in the field, or roof, the component must be installed in the open air condition, natural conditions, will inevitably encounter natural and man-made, typhoon, snow, dust and other natural disasters can damage equipment, mice and other small animals bite the equipment,

photovoltaic power station is usually installed in the field or on the roof. These parts must be installed outdoors. Bad natural environment. Natural disasters, such as natural and man-made disasters, typhoon, storm, dust and other natural disasters will inevitably damage the equipment. Small animals such as mice will bite equipment, cable also are difficult to cut off the thief. The safety of the power station is very important. Whether distributed small power station or centralized large ground has certain risks. As a result, photovoltaic system equipment must be equipped with a special safety device, such as fuse and lightning protection devices. They are often unknown, and at a critical moment to stand up to protect the safety of the power station. 1. Fusion fuse protector is a kind of current, its principle is when the current exceeds the specified value after a period of time, the melt is itself the heat generated by the melt, so as to cut off the circuit. The fuse is widely used in low-voltage distribution system, control system and electrical equipment. As a short circuit and over current protection, fuse is one of the commonly used protective device. A fuse of the photovoltaic power station can be divided into DC and ac fuses fuse. According to the different configuration of photovoltaic inverter, the DC side of the photovoltaic power station together multiple sets of series and parallel to the DC female head of the DC bus ( Centralized inverter scheme) Or a set of series inverter ( A set of series inverter scheme) 。 When several pv set of series and parallel, if a group of short circuit fault occur, the DC bus and the grid on the sum total of the other groups will offer a short-circuit point short circuit current. If there is no corresponding protection measures, photovoltaic components and their connection cable and other equipment will be destroyed. At the same time, it may cause burns near equipment accessories. At present, a lot of fire in similar photovoltaic roof, in order to improve the safety of the photovoltaic power station, it is necessary to install in each series of parallel circuit in protection device. With the increasing demand for DC fuse of photovoltaic industry, how to correctly select the DC fuse protection effectively is a problem of users and manufacturers should pay serious attention. When choosing the DC fuse, exchanges the electrical specifications and structure size of the fuse can't simply copy, because there are many different between the technical specifications and design concept, involves the fault current is safe and reliable to disconnect and not considered in the direction of the accident. 1) Due to the dc current is not zero, when cut off the fault current, arc only under the effect of quartz sand packing forced cooling quickly extinguished by oneself, this is much more difficult than to cut off the ac arc. Melt the reasonable design and welding method, the purity and granularity of the quartz sand ratio, melting and solidification method decide the validity of the dc arc force out and effects. 2) Under the same rated voltage, DC arc produced by the arc energy is ac arc more than 2 times. In order to ensure that each arc can be limited within the controllable distance, quickly put out at the same time, each arc by direct series conduction and produce large amounts of energy accumulation, cause long time continuous arc of blown fuse resulted from the accident. DC fuse tube body generally longer than ac fuses, otherwise can't see the size of the normal use differences can have serious consequences in the presence of fault current. 3) According to international data fuse technology organization recommendation, every increase of 150 v, DC voltage fuse tube length should be increased 10 mm, every increase of 1000 v, DC voltage fuse tube length should be an increase of 70 mm. 4) When used in the DC circuit fuse, must consider the existence of the inductance and capacitance energy brought about by the complex, so the time constant of the L/R is an important parameter which cannot be ignored, should be based on the incidence of specific circuit system short circuit fault current and attenuation rate for accurate assessment, rather than choose big or small. Due to the time constant of the L/R DC fuse breaking arc energy, breaking time and the voltage is allowed, so must be reasonable and safely choose tube thickness and length.