What are the main electrical wiring solutions for photovoltaic power stations?

　　What are the main electrical wiring solutions for photovoltaic power stations?

　　When conducting primary electrical design, factors such as power supply reliability, operational flexibility, ease of operation, economy, and ease of expansion must be fully considered.

　　Typical electrical main wiring can be roughly divided into two categories: according to the number of access points, it can be divided into wiring methods with a busbar (that is, a single access point) and wiring methods without a busbar (multiple access points). Among them, busbar connection methods are divided into single (double) busbar and single (double) bus segmentation methods, and busbar-free connection methods can be divided into external bridge connection method and inner bridge connection method.

　　1. Convergence bus wiring method

　　1.Single busbar wiring method

　　The advantages of single busbar wiring are simple and clear wiring, less equipment, small investment, convenient operation, and conducive to expansion. Disadvantages of single busbar wiring: poor reliability and flexibility. All power must be disconnected when the busbar or busbar isolating switch is inspected or malfunctions.

　　2.Double busbar wiring method

　　The two sets of busbars are connected through busbar contact circuit breakers. Each lead line and power branch are connected to the two sets of busbars through a circuit breaker and two sets of busbar isolating switches.

　　Advantages of double-busbar wiring: maintenance of any busbar does not affect the normal power supply; maintenance of the busbar isolating switch only affects the power supply of this branch (the isolating switch cannot break with load, and the circuit breaker needs to be disconnected); when the working busbar fails, all The branch circuit can quickly restore power supply; when special needs arise, the busbar tie circuit breaker can be used to perform parallel and de-paralleling operations with the system. Therefore, the operation schedule is flexible and the reliability is high. Similarly, the equipment investment cost is high.

　　2. Wiring method without busbar

　　1.Unit wiring

　　The outlet of the power generation unit is directly connected to the high-voltage system through the transformer, which is called the power generation unit-transformer group unit wiring. On this basis, the high-voltage side of each main transformer is directly connected to a transmission line and transmits power independently. There is no switch station in the power plant, and there is no electrical connection between each main transformer. It is called a generator-transformer-line group unit. wiring.

　　Advantages of unit wiring: simple wiring, less switching equipment, less space, easy operation, reduced short-circuit current in low-voltage measurement of generators and main transformers (because there are fewer power points for feedback), especially its investment can be reduced to a minimum .

　　2.Bridge wiring

　　The so-called inner and outer bridge wiring are distinguished according to the distance between the bridge (circuit breaker QF3 in the picture) and the transformer. The short distance is called the inner bridge, and the far distance is called the outer bridge. The distance is based on the unit wiring of the main circuit breaker (in the picture). QF1, QF2) is the basis for judgment.

　　Inner bridge wiring is suitable for situations where line maintenance is frequent and the transformer does not need to be switched frequently (the switching operation is cumbersome when the transformer is switched, and QF1 and QF3 need to be cut off at the same time).

　　External bridge wiring is suitable for situations where the lines are short, the transformer needs to be switched frequently, and the booster station has through-pass power.

　　3. Cost comparison

　　For the above-mentioned schemes, the equipment investment costs from high to low are double-busbar wiring, single-bus segmented, bridge-type wiring, unit wiring, and single-busbar wiring (unit wiring is suitable for multiple access points, and repeated investment is more expensive than single-busbar wiring). Busbar wiring is high).

　　4. Characteristics of electrical main wiring of photovoltaic power stations

　　The photovoltaic power station is located at the end of the power grid and has a small installed capacity. The input and output of the photovoltaic power station have basically no impact on the stability of the system. Therefore, the photovoltaic power station can be input for power generation and disconnected from operation at any time. Therefore, during design, the requirements for the reliability of power transmission from photovoltaic power stations are not a priority.

　　In principle, all the above solutions are suitable for the main electrical wiring of photovoltaic power stations, but considering the economic benefits and the number of access points, photovoltaic power stations should give priority to solutions with relatively low investment. Therefore, the main electrical wiring of the photovoltaic power station can adopt unit wiring, bridge wiring or single busbar wiring.

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