随着调度一声令下，玛尔挡水电站合上3305开关开始对5号主变压器进行第一次冲击合闸试验。本次试验将750kV云杉变电站作为电源供应点，通过330千伏输电线路、开关站GIS、330千伏高压电缆、地下GIB传送至主变高压侧进行倒送电操作。冲击合闸试验共进行5次，本次试验相序、变比、电流的辐值、二次回路电压及相关保护、表计正确，继保、测控及自动化信号各项结果正常，各次冲击合闸试验结果及运行指标均符合要求。

送电前，玛尔挡公司严格审查启动方案、操作单、定值文件、应急预案等，并对现场设备及保护装置各项性能进行仔细确认。同时，对带电运行设备实行区域隔离，设置安全警示标识，对作业人员进行详细的安全技术交底，明晰危险源及预防控制措施，确保现场作业环境安全可控，为本次试验保驾护航，保障了主变压器冲击合闸试验一次性成功。

主变压器倒送电冲击合闸试验的完成，标志着首台机组330kV系统已具备带电运行条件，为后续机组并网、商运打下了坚实基础。

With the dispatch of the first order, Maerblock hydropower station to close the 3305 switch began to 5 main transformer for the first impact closing test. In this test, 750kV Spruce transformer station is used as the power supply point, which is transmitted to the high voltage side of the main transformer through 330 kV transmission line, switch station GIS, 330 kV high voltage cable and underground GIB for reverse power transmission operation. The impact closing test was carried out for a total of 5 times, the test phase sequence, ratio, current spoke value, secondary loop voltage and related protection and meter were correct, the results of relay, measurement and control and automation signals were normal, and the results of each impact closing test and operating indicators met the requirements.

Before power transmission, Marblock company strictly reviews the starting scheme, operation order, setting documents, emergency plans, etc., and carefully confirms the performance of on-site equipment and protection devices. At the same time, the implementation of regional isolation for live operating equipment, set up safety warning signs, detailed safety technology disclosure for operators, clear hazard sources and prevention and control measures to ensure that the site operating environment is safe and controllable, escort for this test, and ensure the main transformer impact closing test one-time success.

The completion of the shock closing test of the main transformer in reverse power supply marks that the 330kV system of the first unit has the operating conditions of live power, which lays a solid foundation for the subsequent units to be connected to the grid and commercial operation.