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The difference between isolated island and anti-islanding device

          Recently found that some unscrupulous manufacturers fish market to deceive users, holding isolated island device as an anti-islanding device to sell, in fact, the two are essentially the region, the use of confusion, there will be a big security risk, in order to better Services in the national grid, against those fish eyes blacksmith vendors, the following pen are simple to talk about anti-islanding device and anti-islanding device difference

          Anti-islanding protection is required for distributed photovoltaic power plants. That is, when the grid appears high voltage, low voltage, high frequency, low frequency failure, the grid-connected photovoltaic switch in time. When the grid is restored and the voltage and frequency reach the allowable value, the grid switch should be automatically closed. The purpose is to ensure that the national grid will not be much affected circumstances, as far as possible to ensure the photovoltaic power generation efficiency. In some areas, the functions of anti-islanding protection devices will be further improved according to the requirements of local power supply departments. For example, adding over-current protection and unbalanced voltage protection are all understandable. However, at present, some users in the market think that the inverter itself has anti-islanding function, and how it needs to be separately installed anti-islanding protection. In fact, anti-islanding protection device has just begun to use the high voltage level, but later also slowly used in low voltage. For the current inverter, when the grid voltage is pulled high, the inverter will still work properly. Examples: 1) A village-level power station in Heze City, Shandong Province, with a capacity of 300KWP and a transformer of 40KWP. When the power generation is relatively high at noon in summer, the grid voltage can reach 480V or so. If the grid-connected switch does not trip The inverter will still work normally. This long-term operation is bound to impact the power grid. 2) A plant producing photovoltaic PV prices in Ma On Shan, Anhui Province, installed rooftop PVs to implement self-powered residual power grid connection. However, since the installation of photovoltaic power, some of the test equipment power modules in the plant may have burned down. This is caused by the fact that the power supply Instability caused. After taking UPS power supply, problem solving. The above two examples show that distributed photovoltaic power generation has been less stable, when the grid voltage is abnormal, accurate and timely tripping is also very necessary. To achieve this function requires anti-islanding device to achieve, the national grid is also required.

          At the same time, some PV installations require anti-islanding protection devices in the power grid. For many people, anti-islanding protection devices are not too familiar to you, anti-island rarely seen in the market. Do not mistake the two for the same, but in fact they are not the same thing at all. Anti-islanding protection device is a microcomputer protection device, and anti-islanding is the form of distribution cabinet, since the instructions and related information turned over, the following talk about personal anti-islanding installation of meaning and opinions.

Anti-islanding and isolated island device difference.png

          As shown in the figure above, for some rural roofs, this kind of installation exists more. And the PV capacity is not too large, and then the network will not pull the cable side of the transformer, are looking for the nearest 380V power grid. This is both convenient and cost-saving. However, in this case, there will be a situation where the photovoltaic power supply is just for the user side load. If it happens to flow through the grid-connected switch current to 0, the grid is in the process of overhauling. As a result, maintenance personnel will inevitably cause security risks. Moreover, the power generation system runs away from the power grid or isolated network, and is harmless to the user side as well. If in the overhaul, put all the roof of the transformer photovoltaic are stopped, it seems that no small amount of workload. Therefore, it is required to install anti-islanding protection in the configuration of the national grid, which is mainly used in overhauling to ensure personal safety of maintenance personnel and safe use of electricity by users. As shown below:

Anti-islanding device.png

          Simply speaking, when the grid needs overhauling, the grid connection switch is off, and the anti-islanding device is manually put into the device at this time. If the 400V busbar is under voltage at this time, the disturbance resistance in the anti-islanding is put into operation and the balance between electricity generation and electricity consumption is achieved. So that the PV inverter detects the external voltage is not enough to meet the normal output power, forced to stop the inverter. This way you do not have to determine whether each household's inverter stops working. Of course, anti-islanding and grid switch has an interlock, if the grid switch in a position, into the anti-island is useless.

          Although the above is a small probability event, but not difficult to find that the national grid for the safety of electricity, the thought is more comprehensive. For anti-islanding, the grid provides anti-islanding, the use of the transformer 80%, if not, you can only use 25%. However, for the PV specialization, it is basically involved in the operation of isolated networks, and the PV capacity is also in the form of hundreds of K, and more use of anti-islanding as a protection.

          The above is my personal opinion, for reference purposes only. This article comes from : http://www.relay-protector.com/technical/876.html . Please refer to the source!

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