Outsourcing maintenance is an economical way for wind farm owners to address sophisticated and expensive maintenance operations of wind turbines. This paper proposes three options for the post-warranty maintenance contract of wind turbines from the perspective of service providers. Option 1 involves corrective maintenance only. In option 2, the first preventive maintenance is performed at a certain time point and after that periodic maintenance is carried out. Option 3 initiates with a preventive replacement and performs periodic maintenance subsequently. An availability target is set over the contract period and failing to satisfy the target incurs a penalty from the service provider. The objective is to determine the optimal preventive maintenance programs of option 2 and option 3 that minimize the contract servicing cost. Numerical examples are provided to illustrate the proposed policies. The results show that option 2 and option 3 are more effective than option 1 and their effectiveness grows when warranty and contract coverages increase.

外包维护是风电场所有者解决风力涡轮机复杂而昂贵的维护操作的一种经济方式。本文从服务提供商的角度提出了风机保修后维护合同的三种选择。选项1仅涉及纠正性维护。在选项2中，第一次预防性维护在某个时间点执行，然后进行定期维护。选项3首先进行预防性更换，然后进行定期维护。在合同期内设定了可用性目标，如果未能达到该目标，则会受到服务提供商的罚款。目的是确定使合同服务成本最小化的方案2和方案3的最佳预防性维护程序。提供了数字示例来说明建议的策略。结果表明，选项2和选项3比选项1更有效，并且随着保修和合同范围的增加，它们的有效性也会提高。