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，特别是监测环境，如农业种子储存，化学，生物医学，食品和电子加工，医院，博物馆，图书馆和大多数建筑物。水分测量在高压工程中对Transformer油中水分含量的测量非常重要。目前，该行业依靠各种测量局部放电（PD）的方法来确定何时需要维修Transformer。大多数方法只在损害已经造成时才给出指示。测量绕组绝缘纸和框架中的水分可以使Transformer在损坏发生之前得到维修，这将导致更强大的电力系统和可观的节省。在电传感器等几种技术中，光纤传感器由于体积小、重量轻、易于实现多功能传感以及更重要的是其抗电磁干扰能力而受到更多的关注。基于光纤布拉格光栅（FBG）的光学传感器已经变得广为人知和流行。光纤光栅是一种结构紧凑的本征传感元件，其生产成本相对较低，易于多路复用，并适用于一系列应变和温度传感应用。最近QPS Photonics Inc.研制了一种采用两种类型FBG的湿度传感器，一种是标准FBG，另一种是先进的相移光栅。这种传感器是在光栅表面上逐层涂覆10层聚酰亚胺涂层，并在300 ℃下固化而成的。涂层在与水分接触时吸收水分，轻微膨胀并从固有应变恢复。本计画的目的是研制一种高灵敏度且具成本效益的光学感测器，以监测高压电力Transformer内部的温度与湿度。本课题主要是对一种能够检测微量水分的传感器进行封装设计和性能表征。这将是世界上第一次开发这种能力，使Transformer所有者能够真实的了解水分的运输，这取决于工作油温和负载。

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.