Modal impact testing for non-destructive evaluation of wood pole transmission lines

Nalcor Energy是纽芬兰和拉布拉多最大的发电公司，目前拥有约2400公里的木杆输电线路，由约26000根不同年龄的杆组成。由于老化、腐烂和周期性潮湿或冻结等多种因素，木质杆会失去强度。 必须及早发现“危险杆”，以避免对检查人员造成安全危害，并最大限度地利用采取防腐处理等纠正措施的机会。 低强度的电线杆在风和冰的作用下可能会失效，导致级联失效和大范围停电。 另一方面，过早地将杆从服务中移除会浪费能源、材料和金钱。现有的商业无损评估（NDE）设备往往会过度预测旧杆的强度，从而造成危险杆使用时间过长的风险。 Nalcor Energy和Memorial University正在进行一项研究计划，以开发基于模态冲击测试的新NDE方法。 初步结果表明阻尼比（在实验室条件下用模态冲击锤测量）和实验室强度之间具有良好的相关性。 拟议的研究阶段将在现场进行极点测试，目的是提高该方法对现实条件的鲁棒性。 将使用便携式现场测试设备，在有导体和无导体的情况下，对将要重新定位的输电线路杆进行模态测试，以便确定电线的影响。 然后将杆移除并运输到实验室，在刚性夹具中进行测试，以量化并帮助模拟基础的影响。 最后将对电杆进行破坏性测试，破坏性测试结果将用于根据振动数据创建预测模型。 考虑到这样的杆的数量是大约170000在大西洋加拿大和200万在北美，在研究计划的成功将激励开发的通用和便携式测试程序和设备的商业市场。

Nalcor Energy, Newfoundland and Labrador's largest power generation utility, currently maintains approximately 2400 km of wood pole transmission lines, consisting of approximately 26000 poles of varying ages. Wooden poles lose strength due to a number of factors such as aging, rot, and cyclical wetting or freezing. It is essential to detect "danger poles" early to avoid safety hazards to inspection personnel, and to maximize the opportunity to apply corrective actions such as preservative treatment. Low strength poles can fail during wind and ice loading, leading to cascade failure and extensive power outages. On the other hand, prematurely removing a pole from service wastes energy, materials and money. Existing commercial non-destructive evaluation (NDE) equipment tends to overpredict strength of old poles, creating the risk of leaving danger poles in service for too long. Nalcor Energy and Memorial University have an ongoing research program to develop new NDE methods based on modal impact testing. Preliminary results show good correlation between damping ratios (as measured with a modal impact hammer under laboratory conditions) and strength in the laboratory. The proposed phase of research will see testing of poles in the field, with the goal of improving the robustness of the method to real-world conditions. Transmission line poles that are to be relocated will be subjected to modal testing, using portable field-test equipment, with and without conductors so that the effect of wires can be determined. The poles will then be removed and transported to the laboratory for testing in a rigid clamp, to quantify and aid in modeling the effect of the foundation. The poles will finally be destructively tested, with the destructive test results used to create prediction models based on vibration data. Given that the number of such poles is approximately 170000 in Atlantic Canada and 2 million in North America, success in the research program will motivate development of versatile and portable test procedures and equipment for the commercial market.