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大家一起学标准之IEC61400-1(18)

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点击听全文，今天大家继续一起学IEC61400-1。

7.4.8 Parked plus fault conditions (DLC 7.1)

Deviations from the normal behaviour of a parked wind turbine, resulting from faults on the electrical network or in the wind turbine, shall require an alysis. As a minimum, failures in the following systems shall be evaluated: brake system, pitch system, and yaw system. The fault condition shall be combined with EWM for a return period of one year. Those conditions shall be either turbulent or quasi-steady with correction for gusts and dynamic response.

In case of a fault in the yaw system, yaw misalignment of ±180° shall be considered. If for the cases DLC 7.1 with fault in the yaw system, yaw misalignment is evaluated using discrete values, the increment in yaw misalignment shall be not more than 10° in the sector of the maximum lift force on the blades. For any other fault, yaw misalignment shall be consistent with DLC 6.1.

If slippage in the yaw system can occur at the characteristic load found in DLC 7.1, the largest unfavourable slippage possible shall be considered.

7.4.9 Transport, assembly, maintenance and repair (DLC 8.1 and 8.2)

For DLC 8.1, the manufacturer shall state all the wind conditions and design situations assumed for transport, assembly on site, maintenance and repair of a wind turbine. The maximum stated wind conditions shall be considered in the design if they can produce significant loading on the turbine. The manufacturer shall allow sufficient margin between the stated conditions and the wind conditions considered in design to give an acceptable safety level. Sufficient margin may be obtained by adding 5 m/s to the stated wind condition.

In addition, DLC 8.2 shall include all transport, assembly, maintenance and repair turbine states which may persist for longer than one week. This shall, when relevant, include a partially completed tower, the tower standing without the nacelle and the turbine without one or more blades. In the case of a tower standing without a nacelle, appropriate means shall be taken to avoid critical wind speeds for vortex generated transverse vibrations, or the appropriate fatigue design load shall be added¹¹. It shall be assumed that the electrical network is not connected in any of these states. Measures may be taken to reduce the loads during any of these states as long as these measures do not require the electrical network connection.

Blocking devices shall be able to sustain the loads arising from relevant situations in DLC 8.1. Non-redundant blocking devices shall be designed in component class 3. In particular, application of maximum design actuator forces shall be taken into account. It is recommended that standards for lifting appliances including safety factors/influence factors are additionally applied when relevant. Unless permanently installed, the lifting appliance itself is not covered by this document and should be designed and tested according to relevant standards for lifting appliances.

7.5 Load calculations

Loads as described in 7.3.2 through 7.3.5 shall be taken into account for each design load case. Where relevant, the following shall also be taken into account:

·wind field perturbations due to the wind turbine itself (wake induced velocities, tower shadow, etc.);

·the influence of three dimensional flow on the blade aerodynamic characteristics (e.g. three dimensional stall and aerodynamic tip loss);

·unsteady aerodynamic effects;

·structural dynamics and the coupling of vibration modes;

·aeroelastic effects;

·the behaviour of the control system of the wind turbine.

Dynamic simulations utilizing a structural dynamics model are usually used to calculate wind turbine loads. Certain load cases have a turbulent wind input. The total period of load data for these cases, shall be long enough to ensure statistical reliability of the estimate of the characteristic load. At least six 10-min stochastic realizations (or a continuous 60 min period) shall be required for each mean, hub-height wind speed used in the simulations. However, for DLC 2.1, 2.2 and 5.1, at least 12 simulations shall be carried out for each event at the given wind speed. Since the initial conditions used for the dynamic simulations typically have an effect on the load statistics during the beginning of the simulation period, the first 5 s of data (or longer if necessary) shall be eliminated from consideration in any an alysis interval involving turbulent wind input.

It shall be ensured that during application of a cycle count on the load time series, the remaining residuals from each time series shall be taken into consideration by half-cycles for fatigue failure mode evaluation. Furthermore, the discretization of the load range shall ensure a sufficient resolution.

When turbulent winds are used for dynamic simulations, attention should be given to the grid resolution regarding the spatial¹² and time resolution.

In many cases, the local strains or stresses for critical locations in a given wind turbine component are governed by simultaneous multi-axial loading. In this case, time series of orthogonal loads that are output from simulations are sometimes used to specify design loads. When such orthogonal component time series are used to calculate fatigue and ultimate loads, they shall be combined to preserve both phase and magnitude. Thus, the direct method is based on the derivation of the significant stress as a time history. Extreme and fatigue prediction methods can then be applied to this single signal, avoiding load combination issues.

Ultimate load components may also be combined in a conservative manner assuming the extreme component values occur simultaneously. In case this option is pursued, both minimum and maximum extreme component values shall be applied in all possible combinations to avoid introducing non-conservatism.

Guidance for the derivation of extreme design loads from contemporaneous loads taken from a number of realizations is given in Annex I.

7.4.8 停机静置叠加故障工况（DLC 7.1）

电网故障或机组内部故障会造成静置机组偏离正常工作状态，该类工况必须开展分析。至少应对制动系统、变桨系统、偏航系统的失效工况进行评估。故障工况应与重现期 1 年的极端风速模型（EWM）组合，风况可选用湍流模型，或采用准稳态方法并对阵风、动态响应进行修正。

若偏航系统发生故障，应考虑 ±180° 偏航偏差。对于偏航系统故障的 DLC 7.1 工况，若采用离散值计算偏航偏差，则在叶片最大升力对应的扇区内，偏航偏差计算步长不宜大于 10°。其余各类故障对应的偏航偏差取值应与 DLC 6.1 保持一致。

若 DLC 7.1 对应的特征荷载作用下偏航系统存在滑移可能，则应考虑最不利的滑移量。

7.4.9 运输、安装、维护与检修工况（DLC 8.1、8.2）

对于 DLC 8.1，制造商应当明确机组运输、现场安装、维护检修所假定的全部风况与设计工况。若规定的最大风况能够在机组上产生显著荷载，则设计中必须予以考虑。制造商需要在规定风况与设计校核风况之间预留充足裕度，保证安全水平达标；可通过在给定风速基础上增加 5 m/s 实现足够安全裕度。

除此之外，DLC 8.2 包含所有持续时长可能超过一周的运输、安装、运维状态；适用时涵盖未完工塔筒、无机舱塔筒、缺失一片或多片叶片的机组。塔筒未安装机舱时，应当采取措施避开诱发横风向涡激振动的临界风速，或者增设对应的疲劳设计荷载 ¹¹。所有上述工况均假定机组未连接电网。可以采取措施降低工况荷载，但措施不得依赖电网供电。

锁止装置应当能够承受 DLC 8.1 相关工况产生的荷载。无冗余设计的锁止装置需按照 3 类部件进行设计，尤其需要考虑执行机构最大设计作用力。适用情况下，建议额外遵循起重设备相关标准（包含安全系数、影响系数）。起重设备若非永久安装，不属于本标准覆盖范围，应依据对应的起重设备标准开展设计与试验。

7.5 荷载计算

每个设计荷载工况均应考虑 7.3.2～7.3.5 规定的各类荷载；适用时还应纳入下列影响因素：

·机组自身造成的流场扰动（尾流诱导速度、塔影效应等）；

·三维流动对叶片气动特性的影响（例如三维失速、叶尖气动损失）；

·非定常气动效应；

·结构动力学以及各阶振型耦合效应；

·气弹效应；

·风力发电机组控制系统动态特性。

通常采用结构动力学模型开展动态仿真计算机组荷载。部分荷载工况输入湍流风。该类工况的荷载数据时长应足够，保证特征荷载统计结果可靠。对于仿真采用的各个轮毂高度平均风速，至少需要 6 组 10 分钟随机样本（或连续 60 分钟时长）。但 DLC 2.1、2.2、5.1 工况下，给定风速的每一类事件至少完成 12 次仿真。动态仿真初始条件通常会影响仿真初期的荷载统计结果，因此所有包含湍流风输入的分析区间，应当剔除最开始 5 秒数据（必要时延长剔除时长）。

在对荷载时程开展雨流计数时，疲劳失效评估需采用半循环计入各时程的剩余荷载循环；同时荷载幅值离散划分需要保证足够分辨率。

采用湍流风开展动态仿真时，需要关注空间分辨率 ¹² 与时间步长对应的网格精度。

多数情况下，机组构件关键位置的局部应变、应力由多轴同步荷载控制。工程中有时采用仿真输出的正交荷载时程确定设计荷载。使用正交分量时程计算极限荷载与疲劳荷载时，组合计算必须同时保留相位与幅值信息。直接法基于完整应力时程提取有效应力，随后可对单条时程开展极限与疲劳预测，规避荷载组合难题。

极限荷载分量也可采用偏保守方式组合，假定各分量极值同步出现。采用该方法时，所有分量的极大值、极小值需要进行全部组合，避免计算结果偏危险。

附录 I 提供了基于多组同步荷载样本求取极限设计荷载的相关指导方法。

简单总结

本节明确停机叠加故障、运输安装运维工况的荷载校核条件，并统一荷载计算准则。计算需综合气动、气弹、控制系统耦合等影响；湍流仿真满足样本数量要求，同时规范多轴荷载与极限荷载的组合方式。

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大家一起学标准之IEC61400-1(15)

点击听全文，今天大家继续一起学IEC61400-1。Table 2 – Design load cases (DLC)Design situationDLCWind conditionOther conditionsType of an alysisPartial safety factors1) Power production1.1NTM Vin <Vhub <Vout </Vout<> </Vhub<>For extrapolation of extreme eventsUN 1.2NTM Vin <Vhub <Vout </Vout<> </Vhub<> F* 1.3ETM Vin <Vhub <Vout </Vout<> </Vhub<> UN 1.4ECD Vhub=Vr−2 m/s, Vr, Vr+2 m/s UN 1.5EWS Vin <Vhub <Vout </Vout<> </Vhub<> UN2) Power production plus occurrence of fault2.1NTM Vin <Vhub <Vout </Vout<> </Vhub<>Normal control system fault or loss of electrical network or primary layer control function fault (see 7.4.3)UN 2.2NTM Vin <Vhub <Vout </Vout<> </Vhub<>Abnormal control system fault or secondary layer protection function related fault (see 7.4.3)UA 2.3EOG Vhub=Vr±2 m/sand VoutExternal or internal electrical fault including loss of electrical networkUA 2.4NTM Vin <Vhub <Vout </Vout<> </Vhub<>Control system fault, electrical fault or loss of electrical networkF* 2.5NWP Vin <Vhub <Vout </Vout<> </Vhub<>Low voltage ride throughUN3) Start-up3.1NWP Vin <Vhub <Vout </Vout<> </Vhub<> F* 3.2EOG Vhub=Vin, Vr±2 m/sand Vout UN 3.3EDC Vhub=Vin, Vr±2 m/sand Vout UN4) Normal shutdown4.1NWP Vin <Vhub <Vout </Vout<> </Vhub<> F* 4.2EOG Vhub=Vr±2 m/sand Vout UN5) Emergency stop5.1NTM Vhub=Vr±2 m/sand Vout UN6) Parked (standing still or idling)6.1EWM 50-year return period UN 6.2EWM 50-year return periodLoss of electrical network connectionUA 6.3EWM 1-year return periodExtreme yaw misalignmentUN 6.4NTM Vhub<0.7 Vref F*7) Parked and fault conditions7.1EWM 1-year return period UA8) Transport, assembly, maintenance and repair8.1NTM Vmajto be stated by the manufacturer UN 8.2EWM 1-year return period UAKeyDLC Design load caseECD Extreme coherent gust with direction change (see 6.3.3.6)EDC Extreme direction change (see 6.3.3.5)EOG Extreme operating gust (see 6.3.3.3)EWM Extreme wind speed model (see 6.3.3.2)EWS Extreme wind shear (see 6.3.3.7)NTM Normal turbulence model (see 6.3.2.3)ETM Extreme turbulence model (see 6.3.3.4)NWP Normal wind profile model (see 6.3.2.2)Vr±2m/s Sensitivity to all wind speeds in the range shall be a nalysedF Fatigue (see 7.6.3)U Ultimate strength (see 7.6.2)N NormalA Abnormal* Partial safety for fatigue (see 7.6.3)When a wind speed range is indicated in Table 2, wind speeds leading to the most adverse condition for wind turbine design shall be considered. The range of wind speeds may be represented by a set of discrete values, in which case the resolution shall be sufficient to assure accuracy of the calculation⁶. In the definition of the design load cases, reference is made to the wind conditions described in Clause 6.In the further specifications of design load cases (DLCs) in 7.4.2 to 7.4.9, some DLCs allow alternative formulations. Where alternatives are mentioned, the party designing to this document shall decide which alternative shall be used throughout the an alysis of the DLC.7.4.2 Power production (DLC 1.1 to 1.5)In this design situation, a wind turbine is running and connected to the electric load. The assumed wind turbine configuration shall take into account rotor imbalance. The maximum mass and aerodynamic imbalances (e.g. blade pitch and twist deviations) specified for rotor manufacture shall be used in the design calculations.In addition, deviations from theoretical optimum operating situations such as yaw misalignment and control system tracking errors shall be taken into account in the an alyses of operational loads.Design load cases (DLCs) 1.1 and 1.2 embody the requirements for loads resulting from atmospheric turbulence that occurs during normal operation of a wind turbine throughout its lifetime (NTM). DLC 1.3 embodies the requirements for ultimate loading resulting from extreme turbulence conditions. DLC 1.4 and 1.5 specify transient cases that have been selected as potentially critical events in the life of a wind turbine.The statistical an alysis of DLC 1.1 simulation data, see 7.6.2 and Annex G, shall include at least the calculation of extreme values of the blade root in-plane moment and out-of-plane moment and tip deflection. If the extreme design values of the blade root moments derived from DLC 1.1 are exceeded by the extreme design values derived for DLC 1.3, the further an alysis of DLC 1.1 may be omitted.If the extreme design values of the blade root moments derived from DLC 1.1 are not exceeded by the extreme design values derived for DLC 1.3, the factor c in Equation (20) for the extreme turbulence model used in DLC 1.3 may be increased until the extreme design values of the blade root moments computed in DLC 1.3 are equal to or exceed the relevant values derived from DLC 1.1. The characteristic values of the loads relevant for other turbine components may be determined from this a nalysis based on DLC 1.3 with the increased c-value. As an alternative to this a nalysis, the appropriate characteristic values of all load components relevant for each specific turbine component may be directly determined or extrapolated from the simulation.表 2 — 设计荷载工况（DLC）设计工况DLC 编号风况条件其他条件分析类型分项安全系数类别1）正常发电1.1NTM 切入风速＜轮毂风速＜切出风速用于极端事件外推分析UN（正常） 1.2NTM 切入风速＜轮毂风速＜切出风速 F*（疲劳分项系数） 1.3ETM 切入风速＜轮毂风速＜切出风速 UN（正常） 1.4ECD 轮毂风速 = 额定风速−2m/s、额定风速、额定风速 + 2m/s UN（正常） 1.5EWS 切入风速＜轮毂风速＜切出风速 UN（正常）2）发电叠加故障工况2.1NTM 切入风速＜轮毂风速＜切出风速常规控制系统故障、电网失电或第一层控制功能故障（见 7.4.3）UN（正常） 2.2NTM 切入风速＜轮毂风速＜切出风速异常控制系统故障或第二层保护功能相关故障（见 7.4.3）UA（异常） 2.3EOG 轮毂风速 = 额定风速 ±2m/s、切出风速内部 / 外部电气故障，包含电网失电UA（异常） 2.4NTM 切入风速＜轮毂风速＜切出风速控制系统故障、电气故障或电网失电F*（疲劳分项系数） 2.5NWP 切入风速＜轮毂风速＜切出风速低电压穿越UN（正常）3）启动3.1NWP 切入风速＜轮毂风速＜切出风速 F*（疲劳分项系数） 3.2EOG 轮毂风速 = 切入风速、额定风速 ±2m/s、切出风速 UN（正常） 3.3EDC 轮毂风速 = 切入风速、额定风速 ±2m/s、切出风速 UN（正常）4）正常停机4.1NWP 切入风速＜轮毂风速＜切出风速 F*（疲劳分项系数） 4.2EOG 轮毂风速 = 额定风速 ±2m/s、切出风速 UN（正常）5）紧急停机5.1NTM 轮毂风速 = 额定风速 ±2m/s、切出风速 UN（正常）6）停机（静止或空转）6.1EWM 50 年一遇重现期 UN（正常） 6.2EWM 50 年一遇重现期电网连接丢失UA（异常） 6.3EWM 1 年一遇重现期极端偏航不对中UN（正常） 6.4NTM 轮毂风速＜0.7 倍参考风速 F*（疲劳分项系数）7）停机叠加故障工况7.1EWM 1 年一遇重现期 UA（异常）8）运输、组装、运维检修8.1NTM 最大风速由制造商规定 UN（正常） 8.2EWM 1 年一遇重现期 UA（异常）符号说明DLC 设计荷载工况ECD 带方向变化的极端相干阵风（见 6.3.3.6）EDC 极端风向变化（见 6.3.3.5）EOG 极端运行阵风（见 6.3.3.3）EWM 极端风速模型（见 6.3.3.2）EWS 极端风剪切（见 6.3.3.7）NTM 正常湍流模型（见 6.3.2.3）ETM 极端湍流模型（见 6.3.3.4）NWP 正常风廓线模型（见 6.3.2.2）Vr±2m/s 需分析该风速区间内全部风速对应的敏感性F 疲劳荷载分析（见 7.6.3）U 极限强度分析（见 7.6.2）N 正常工况A 异常工况* 疲劳对应的分项安全系数（见 7.6.3）当表 2 中标注风速区间时，应当选取使风力发电机组设计承受最不利条件的风速开展计算。该风速区间可以采用一系列离散风速值表征，离散取值间隔应当足以保证计算精度⁶。设计荷载工况定义均参考第 6 章规定的各类风况条件。7.4.2～7.4.9 对各设计荷载工况（DLC）作出进一步规定，部分荷载工况允许选用多种计算方案。当条文给出多种可选方案时，依据本标准开展设计的单位应当选定一种方案，并在该荷载工况全部分析过程中统一采用。7.4.2 正常发电工况（DLC 1.1～1.5）该设计工况下，风力发电机组处于运行状态并接入电气负荷。所采用的机组模型应当考虑风轮不平衡效应；设计计算需采用风轮制造允许的最大质量不平衡与气动不平衡（例如叶片桨距、扭角偏差）。除此之外，开展运行荷载分析时，还应当考虑偏离理论最优运行状态的各类偏差，例如偏航不对中、控制系统跟踪误差。设计荷载工况 DLC1.1 与 1.2，规定了机组全生命周期正常运行时大气湍流引发荷载的相关要求（正常湍流模型 NTM）；DLC1.3 规定极端湍流条件产生极限荷载的相关要求；DLC1.4 与 1.5 为瞬态工况，选取机组生命周期内具有潜在危险性的关键事件。针对 DLC1.1 仿真数据开展统计分析（见 7.6.2 及附录 G），至少应当计算叶根面内弯矩、面外弯矩以及叶尖挠度的极值。若 DLC1.3 得到的叶根弯矩设计极值大于 DLC1.1 得到的极值，则可省略 DLC1.1 的后续分析。若 DLC1.3 得到的叶根弯矩设计极值未超过 DLC1.1 得到的极值，则式 (20) 中的系数c可增大 DLC 1.3 中所使用的极端湍流模型，直至 DLC 1.3 计算得到的叶根弯矩极值等于或超过 DLC 1.1 中导出的相关值。对于风力机其他部件相关的荷载特征值，可基于采用增大后 c 值的 DLC 1.3 分析结果确定。作为该分析的替代方法，也可通过仿真直接确定或外推各特定风力机部件所需的所有相关荷载分量的特征值。简单总结本节给出 IEC 61400-1 标准核心荷载工况表，划分 8 大类机组设计工况，搭配对应的风模型、外部条件、极限或疲劳分析类型以及正常或异常分项安全系数；同时补充工况选取原则、风速取值要求，并针对发电工况（DLC1.1~1.5）说明建模要求、不平衡量考虑规则、湍流工况分工，以及 DLC1.1 与 DLC1.3 极值结果对比后的分析简化判定准则。今天就学到这里，明天我们继续学习，每天十分钟大家一起学标准。来源：智慧强学斋