Developing Fiber Optics Moisture Sensors and System used in Transformers and Bushings

湿度和湿度的精确测量有许多应用，特别是在农业种子储存、化学、生物医学、食品和电子加工、医院、博物馆、卫生间和一般情况下，在大多数建筑物中的环境监测。在高压工程中，测量变压器油中的水分含量是非常重要的。目前，该行业依靠各种测量局部放电(PD)的方法来确定变压器何时需要维修。大多数方法只在损害已经造成时才给出迹象。通过测量绕组绝缘纸和框架中的水分，可以在损坏发生之前对变压器进行维修，这将使电力系统更强大，并节省大量资金。在电子传感器等几种技术中，光纤传感器因其体积小、重量轻、对多功能传感器敏感以及更重要的是其对电磁干扰的免疫力而受到越来越多的关注。基于光纤布拉格光栅(FBG)的光传感器已经广为人知和普及。FBG是一种紧凑的本征传感元件，制造成本相对较低，易于多路复用，适用于一系列应变和温度传感应用。最近，QPS Photonics公司开发了一种使用两种类型的FBG的水分传感器，标准FBG和先进的相移光栅。这种传感器是通过在光栅区上逐步涂覆10层聚酰胺涂层而开发的，并在300℃下固化。涂层与水分接触后，吸收水分，轻微膨胀，并从固有应变中恢复。本项目的目标是研制一种高灵敏度、高性价比的光学传感器，用于监测高压电力变压器内部的温度和湿度。本项目涉及能够检测微小水分的传感器的封装设计和性能表征。这将是世界上第一次开发这样的功能，使变压器所有者能够实时了解取决于运行油温和负载的水分传输。

Precise measurement of humidity and moisture has many applications particularly monitoring environmentslike agricultural seed storage, in chemical, biomedical, food, and electronic processing, hospitals, museumslibraries and generally, in most buildings. Moisture measurement in high voltage engineering formeasurements of water content in transformer oil is very important. Currently the industry is relying on variousmethods of measuring partial discharge (PD) to determine when a transformer needs to be serviced. Mostmethods only give indications when damages are already done. The measurement of moisture in the windinginsulation paper and frame allows the transformer to be serviced before damages happened, this will lead to amore robust power system and considerable savings. Among several techniques such as electrical sensors, fiberoptic sensors are capturing more attention due to small size, light weight, susceptible to multifunctional sensingand more importantly their immunity to electromagnetic interference. Fiber Bragg Grating (FBG) based opticalsensors have become widely known and popular. FBGs are compact intrinsic sensing elements, which arerelatively low cost to produce, easy to multiplex, and applicable to a range of strain and temperature sensingapplications. Recently QPS Photonics Inc. has developed a moisture sensor using two types of FBGs, astandard FBG and an advanced phase shifted gratings. This sensor was developed by incrementally applying 10layers of polymide coating over the grating area, and cured at 300 C. The coating upon contact with moisture,absorbs the moisture, slightly expands and recovers from the inherent strain. The objective of this project is todevelop a high sensitive and cost effective optical sensor for monitoring the temperature and moisture inside ahigh voltage power transformer. This project is involved with the design of packaging and characterizing theperformance of the sensor which capable to detect small trace of moisture. This would be the first time in theworld that such a capability will be developed, allowing transformer owners to understand, in real time, thetransport of moisture which depends on the operating oil temperature, and loading.