Sanya, Hainan

Standardization of electrical design for wind farm engineering

Wang Junhua

Hebei Electric Power Survey and Design Institute, Shijiazhuang, Hebei 05003 1 Abstract: This paper expounds and standardizes the design scheme of wind farm and booster station from the aspects of main wiring form, equipment selection, distribution equipment selection, electrical general layout and consideration of special problems of wind farm. The optimized scheme is not only safe, economical and reasonable, but also universal, which can greatly improve the design efficiency.

Standardization of wind power station engineering design

This paper mainly introduces the wind power station and booster station, and provides the design scheme. The single-line form, main equipment selection, distribution equipment selection, general electrical layout and special problems of wind farm are described and standardized in detail. The optimized scheme is not only safe, economical and reasonable, but also universal, which can greatly improve the design efficiency. Keywords:: wind power station booster station design project standardization

Introduction:

At present, domestic wind power projects blow out. In order to ensure the design quality and progress, it is imperative to carry out standardized design. The author has tried standardized design in design practice, and is willing to encourage with all experts. If there are any shortcomings, please criticize and correct me.

1. Wind farm:

1. 1 standardization of connection forms

The wiring of wind farm adopts the unit wiring form of one machine and one transformer, which is not only flexible and reliable in operation, but also easy to realize in layout. The high voltage side adopts ungrounded system, and the low voltage side adopts neutral point direct grounding system. Wind farms generally use 35kV collector lines to connect to booster stations. The 380/220V field power supply of the fan and box transformer is taken from their respective dry-type transformers, and the single bus configuration is adopted. Open transformer does not need 380/220V power supply, thermostat and other secondary components.

1.2 standardization of equipment selection

According to experience, short-circuit current level:

According to the selection, the outlet of the wind farm fan (or stepped up to the low-voltage side) is 20kA, and the high-voltage side of the booster transformer is 3 1.5kA (1). The booster transformer of the wind turbine generator set adopts the no-load oil-immersed double-winding transformer, the voltage level is generally 35kV/0.69kV, and the connection group is D, Yn1/kloc-. Generally, it can be divided into two categories: open transformer and box substation. The price of open transformer is relatively low (compared with box-type substation), but the installation area is large, the installation period is long, it needs regular maintenance, and the installation of high and low voltage side equipment is complicated. Box-type substation has the advantages of compact structure, strong completeness, reliable operation, maintenance-free and beautiful appearance. In particular, it has outstanding effects such as small floor space, flexible site selection, convenient movement and short construction period. Box-type substation is recommended for the step-up transformer of wind turbines. (2) Selection of equipment on high and low voltage side The high voltage side of open transformer is protected by fall insurance, lightning arrester and circuit breaker. The high voltage side of box-type substation is protected by load switch, fuse and lightning arrester, and the low voltage side is protected by circuit breaker. The following are the wiring diagrams of open and box substations.

Paper of 2008 China Wind Power Technology Seminar —— "Lecture 7"

Sanya, Hainan

Standardization of 1.3 layout

Generally, the distance between the fan and the line tower is about 25m. The step-up transformer (or box transformer) is arranged outside the wind turbine 10m, which can ensure the safe lifting distance of the tower and blades. It can also avoid the safe distance after the hanging rope put down by the staff from the engine room swings under the action of wind or other external forces when the fan is maintained; It can also prevent lightning from hitting the transformer (box transformer) back. If the step-up transformer (or box transformer) is placed under the overhead line of the transmission line, if it is close to the tower, it will lead to lightning strike back caused by the line, and if it is slightly away from the tower, it will collide with the inclined cable of the tower, increasing the consumption of low-voltage cable. The high voltage side is directly connected to the overhead line through the conductor T, and the jumper is generally more than ten meters or even twenty meters. The wind swing is very strong, and the T-clamp is often pulled off, which increases the stress on the tower. Therefore, this arrangement is not suitable. The recommended layout of step-up transformer (box transformer) is shown in the figure below. The low voltage side of the transformer is connected to the fan power cabinet through a cable. The high voltage side of the transformer is led up along the tower with cable, and then connected to the overhead line with short conductor T.

The specific layout requirements are as follows: (1)α is the clockwise rotation angle between the connecting line between the center point of the booster transformer (box transformer) and the center point of the fan and the true north direction (this is consistent with the angle displayed by the locator of the construction unit, which is convenient for construction). (2) 15m is the distance from the center point of step-up transformer (box transformer) to the center point of fan. (3) Step-up transformer (box transformer)

2. The booster station part:

2. 1 Standardization of wiring forms

Northwest China is rich in wind power resources and weak in power grid. Local access of wind power to power grid will threaten the stability of the system. The design generally adopts the principle of 500kV high voltage transmission and graded power consumption. This paper does not consider the working conditions in this area. 220kV or 1 10kV main wiring: the local access system of 220kV or1/0kv is generally adopted for wind farms in most areas outside the northwest. Generally, there is only 1 return line on the high voltage side of booster station. When there is a 1 return line on the high voltage side of the booster station, the single bus configuration is adopted. When there are two circuits on the high voltage side of the booster station, the single bus is used for sectional wiring, which is not only simple and clear, but also simple to operate. And the reliability and flexibility of operation are also high. 35kV wiring: The low voltage is generally 35kV, so it is recommended to adopt single bus type. It is understood that at present, the main transformer and electrical equipment are only overhauled once every three years, and can be overhauled within one day. In the future, the overhaul interval may be extended. 35kV bus is not segmented, which has little influence on operation reliability, but.

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Paper of 2008 China Wind Power Technology Seminar —— "Lecture 7"

Sanya, Hainan

However, it reduces the investment of double-sided switchgear or 1 subsection interval. 380V/220V connection: 220kV substation adopts single bus section; 1 10kV substation adopts single bus connection line.

2.2 Standardization of equipment selection

Short-circuit current level: The short-circuit current of the wind farm is provided by the wind farm itself and the system. According to experience, the short-circuit current of the selected equipment can be specified as follows: for 220kV/35kV substation, the 220kV bus is selected as 40kA35kV bus according to 3 1.5kA, 1 10kV/35kV substation: 1 10kV bus is selected as 3 1.5kA; 35kV bus is selected as 3 1.5kA (1), and the main transformer is selected as conventional 2. The 35kV class of the main transformer is not considered to be connected to Y-type. The nonstandard type of the third balance winding is added. For the problem that the capacitor current exceeds the standard, there is no need to install a resistor or an arc extinguishing device at the neutral point of the main transformer. Consider adding a complete set of arc suppression and harmonic elimination devices on the 35kV bus. It is also described in the following special problem of capacitor current exceeding the standard. (2) Selection of 220kv equipment (220kV/35kV substation) SF6 shall be considered for the 220kV circuit breaker. The 220kV disconnector adopts GW7 type at first, and the 220kV current transformer adopts oil-immersed type. All the above products are mature, which are not only low in price, but also rich in operating experience. Moreover, its reliability is also very good. The 220kV disconnector firstly adopts GW7 type, which can make the distribution equipment more compact and save land. Choose GW7 type, and the interval width of 220kV is 13m. If GW4 type is selected, the interval width needs to be 15m. (3) SF6 shall be considered in the selection of 1 10kV equipment (1 10kV substation) and110kv circuit breaker.

1 10kV disconnector adopts GW4 type first, and 1 10kV current transformer adopts oil-immersed type. All the products selected above are very mature products, which are not only low in price, but also very reliable. (4) Selection of 35kV equipment: 220kV/35kV substation and 1 10kV/35kV substation; handcart switchgear is selected for 35kV. Handcart switchgear is smaller than fixed switchgear, which can reduce the building area. And the maintenance is convenient. At present, the domestic 35kV handcart switchgear is a mature product with stable performance. (5) The dynamic reactive power compensation device is considered in the selection of reactive power compensation part. It can be adjusted linearly or automatically in steps within its capacity range, which is more suitable for the changeable working conditions of wind farms, effectively solves the adverse effects caused by large-scale wind farms connected to the power grid, and improves the power quality sent by wind farms.

2.3 Standardization of distribution equipment forms

220kV or 1 10kV power distribution equipment: in areas with earthquake intensity lower than 8 degrees, outdoor supporting tube bus and medium-sized power distribution equipment are adopted. The scheme has the advantages of simple structure, convenient operation and maintenance, clear layout and less steel consumption. 35kV power distribution equipment: indoor switchgear is recommended. Compared with the outdoor open type, the recommended indoor switch cabinet scheme occupies less land and has a shorter installation period.

2.4 Standardization of electrical general layout

220kV (or 1 10kV) and 35kV power distribution devices are arranged in opposite directions, and the main transformer is arranged in the middle. 220kV (or 1 10kV) power distribution devices are arranged in two rows, which not only makes the layout compact and the wiring smooth, but also reduces the material consumption. The optimization of general layout can save land.

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Research Report on the Development of Wind Power Technology in China in 2008

Sanya, Hainan

3. Special problems of wind farms-classification and standardization.

Standardization 3. 1 "Current of single-phase grounding capacitor exceeds the standard"

According to the regulations, the allowable value of 35kV single-phase grounding capacitor current is 10A. When overhead lines are used in 35kV collecting lines, the current of single-phase grounding capacitor can reach more than ten amperes or even dozens of amperes. When cables are used in 35kV collecting lines, the current of single-phase grounding capacitor can reach hundreds of amperes or even higher. The solution considered here is to install "a complete set of arc suppression and harmonic elimination devices" on each section of 35kV low-voltage bus. At present, the "complete set of arc suppression and harmonic elimination device" is a relatively mature product in China, which not only solves the problem of arc overvoltage, but also avoids resonance overvoltage, making the system run safely and stably.

Universal grounding device is used to protect grounding. The grounding body first uses the fan foundation as a natural grounding body, and then lays an artificial grounding net to meet the requirements of grounding resistance. The main grounding grid adopts a composite grounding grid with horizontal grounding grid as the main and vertical grounding grid as the auxiliary. The horizontal grounding grid and equipment grounding downlead of wind farm adopt -60×6 hot-dip galvanized flat steel. φ60 hot-dip galvanized steel pipe is used as vertical grounding body. The grounding grid of step-up transformer (or box transformer) of fan adopts a composite grounding grid with horizontal grounding grid as the main grounding grid and vertical grounding grid as the auxiliary grounding grid. -60×6 hot-dip galvanized flat steel and φ 60 hot-dip galvanized steel pipe are used as vertical grounding bodies. The fan booster transformer and the grounding grid of the fan booster transformer can be connected into a whole. However, it is not connected to the grounding grid of the line tower, so as to prevent the lightning from striking the line from returning to the transformer through the grounding grid of the line tower. The details are as follows: a) The fan, transformer and transformer neutral point are grounded through the * * * power grid. The length of connecting flat steel between transformer main grounding grid and fan outer ring grounding grid should be greater than 15m. It can prevent the lightning striking the fan blade lightning receptor from returning to the transformer through the fan grounding network. B) When the grounding grid of a group of fans and transformers does not meet the resistance requirement of 4Ω, it can be connected with the grounding grid of adjacent fans and transformers for unlimited times. Until the requirements are met, two -60×6 hot-dip galvanized flat steels are used as the connecting material. Generally, two or three wind turbines can meet the requirements. When two or three fans are connected and do not meet the requirements of grounding resistance, and are far away from other fans, additional rays can be used to reduce the resistance. The grounding intention of the wind farm is as follows:

3.2 Standardization of solutions to grounding problems in wind farms

The grounding material of wind farms built on the seashore or in areas where the soil corrodes steel is copper. The soil of wind farm built on grassland or desert is non-corrosive to steel, and the grounding material is steel. The soil resistivity of wind farms built on grasslands or deserts is generally very high, up to hundreds of ohms or even thousands of ohms. The grounding grid made by normal method is difficult to meet the requirement that the fan is less than 4 ohms. The practical solution of the wind farm is as follows: the grounding of the wind turbine: the working grounding of the wind turbine.

Research Report on the Development of Wind Power Technology in China in 2008

Sanya, Hainan

3.3 Standardization of grounding scheme for booster station

The grounding material of booster stations and GIS distribution areas built at the seaside or in areas where the soil is corrosive to steel is copper. For booster stations built on grasslands or deserts, the soil is generally non-corrosive to steel, and the grounding material is steel. For booster stations built on grasslands or deserts, the soil resistivity is generally high. It is hundreds or even thousands of ohms high. The grounding grid made by conventional methods is difficult to meet the requirement that the booster station is less than 0.5 ohm. The solution is as follows: the grounding grid of booster station adopts a composite grounding grid with horizontal grounding grid as the main grid and vertical grounding grid as the auxiliary grid. 1 10kV booster station adopts -60×6 hot-dip galvanized flat steel for the horizontal grounding grid, and -60× for the down lead of equipment. φ60 hot-dip galvanized steel pipe is used as vertical direct grounding body. The horizontal grounding grid of 220kV booster station adopts -60×8 hot-dip galvanized flat steel, the down lead of equipment adopts -80×8 hot-dip galvanized flat steel, and the vertical grounding body adopts φ60 hot-dip galvanized steel pipe. When the resistance requirement is 0.5 Ω, corresponding measures can be taken according to the actual situation. General measures include: expanding power grid, introducing grounding body and changing soil.

3.4 choose "dynamic reactive power compensation device form" standardization.

The type of "magnetic control dynamic reactive power compensation device" is recommended and standardized. Due to the instability of wind power output, the required reactive power is not a fixed value and needs to be automatically adjusted according to the output of the wind turbine. The traditional capacitor bank can no longer meet the needs of working conditions. Dynamic reactive power compensation device must be selected. At present, there are three common forms in the market: magnetic control dynamic reactive power compensation device, voltage regulation dynamic reactive power compensation device and phase control.

Dynamic reactive power compensation device. The principle of the magnetically controlled dynamic reactive power compensation device is that the magnetically controlled reactor adopts the principle of DC auxiliary magnetization, and the magnetic permeability of the iron core is changed by additional DC excitation magnetization, so that the reactance value can be continuously adjusted, thereby adjusting the output capacity of the reactor and realizing flexible compensation of reactive power. Its internal structure is completely static, with no moving parts, high working reliability and fast and smooth adjustment. The response time is 100-300 ms, and the compensation effect meets the requirements of wind farm conditions. Magnetron reactor is controlled by low-voltage thyristor, and its terminal voltage is only 1% ~ 2% of the system voltage, which is safe and reliable, without series or parallel connection, and is not easy to be broken down. The harmonic content of the equipment itself is small, which will not cause secondary pollution to the system. Small floor space. Convenient installation and arrangement. After the device is put into operation, the power factor can reach above 0.95, voltage fluctuation and flicker are eliminated, and the three-phase balance meets international standards. The price is moderate. First of all, recommend. The principle of the voltage-regulating dynamic compensation device is: using the voltage regulator to change the output of the capacitor terminal voltage. According to Q=2πfCU2, the reactive power output is adjusted by changing the terminal voltage of the capacitor, thus changing the reactive power output capacity to adjust the system power factor. At present, the output capacity of the device can be divided into nine grades from (100-36)%. The device is a hierarchical compensation mode, which is easy to cause overcompensation and undercompensation. Because the tap-changer of the voltage-regulating transformer is mechanically over-actuated, the response time is slow (4s), and the reactive power change and voltage flicker of the system can not be tracked in time, so the compensation effect is poor. However, it is much better than the traditional capacitor bank. In the process of voltage regulation,

Paper of 2008 China Wind Power Technology Seminar —— "Lecture 7"

Sanya, Hainan

Poor, but cheap, there is a certain market at present, but it is not an ideal form, just a product of the transitional stage, and it is not recommended. The principle of phase-controlled dynamic reactive power compensation device is based on the phase-controlled principle, and the adjustment principle of controllable reactor is shown in the following figure. By controlling the conduction time of the thyristor, the control angle is α, and the fundamental component of the current decreases with the increase of the control angle α, which can vary from 0 to 90.

Advantages of phased schematic diagram: fast response speed ≤40ms, suitable for metallurgical industry. Disadvantages: Thyristors run under high voltage and high current for a long time, which is easy to be broken down and difficult to maintain; Harmonic voltage pollution power grid needs matching filter devices, which occupies a large area and is expensive. Not recommended under wind conditions.

3.5 Standardization of high altitude considerations for wind farms

When the altitude is 2500m ≥ h > When 65438+4000m ≥H >, it is necessary to modify the external insulation of electrical equipment and choose high-altitude products. The formula for calculating the correction coefficient is: ka =1/(1-0.0001h), where h is the altitude of the equipment installation site, and the unit is m. When the altitude is 40, it is recommended to add 220kV and/kloc at 2500m. SF6 gas holder is used in 35kV distribution equipment.

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4. Concluding remarks

The above is the summary and refinement of the author's accumulated experience in the design process. Willing to communicate with peers and contribute to the standardized design of wind farms. Remarks: The title of the paper is "(7)".

Contact information of the author: Hebei Electric Power Survey and Design Institute Tel: 0311-87912590 Email: Department of New Energy Engineering [1* * * *] Wang Junhua, majoring in wind power generation and electric power.

Fax: 0311-87912580

wangjh@hbed.com.cn

wangjh3226@ 126.com

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