Generator Fiber Optic Temperature Measurement System

summary:

The operating temperature of the generator set, especially the temperature of the stator bars and circuit tubes, is an important indicator of the operating status of the hydro generator. So far, the methods for measuring the temperature related to hydroelectric generators include thermal resistance temperature measurement, thermocouple temperature measurement, and infrared temperature measurement. Thermistors and thermocouples both require metal wires to transmit signals. Due to the inability to guarantee the insulation stability of metal wires, we cannot directly measure the temperature of stator bars and copper ring tubes, but rather measure the temperature of the insulation layer. As for infrared temperature measurement, it is a non-contact temperature measurement that can only measure the surface temperature of devices that are susceptible to environmental temperature and surrounding electromagnetic interference. It can only be manually operated and cannot be measured online. In addition, the internal space of the hydroelectric generator is too narrow to install an infrared temperature probe. Therefore, with the development of fiber optic temperature measurement technology, fiber optic temperature measurement can be used to measure the temperature of hydroelectric generators. According to the "DL/T 1163-2012 Guide for Configuration of Online Monitoring Devices for Hidden Pole Generators", a large number of resistance thermometers and thermocouple thermometers should be embedded in the generator according to the measurement location and generator design. With the development of fiber optic temperature measurement technology, fiber optic temperature sensors have the advantages of strong anti-interference ability, fast response, and high accuracy, and are increasingly used to measure the internal temperature of generators.     

Fiber optic sensing technology is a new type of sensing technology that has developed with the advancement of fiber optic and fiber optic communication technology. It is one of the fastest developing technologies in the world since the mid-1970s. FOS fiber optic sensors are fundamentally different from power based sensors. Fiber optic sensors use light as the carrier of sensitive information, with optical fibers serving as the medium for transmitting sensitive information. It is widely used due to its unique characteristics. Fiber optic sensors are used to measure temperature, and according to the fiber optic sensor used and the measurement principle adopted, fiber optic temperature measurement can be divided into many types. At present, fiber optic grating temperature measurement, distributed cable temperature measurement, and fluorescent fiber optic temperature measurement are the main types of fiber optic temperature measurement used in the power industry. Among them, fluorescent fiber temperature measurement is suitable for the smallest sensor size, which makes it suitable for measuring the temperature of generator and transformer windings.

Principle of fluorescence temperature measurement:

The fluorescent temperature sensing probe consists of a common multimode optical fiber and a fluorescent substance (coating) on the top. The principle of temperature measurement is as follows: Fluorescent materials will be excited and emit fluorescent energy after being excited by light of a certain wavelength. When photoexcitation disappears, the persistence of fluorescence emission depends on the characteristics of the fluorescent substance, environmental factors, and the lifetime of the excited state. This excited fluorescence usually decays exponentially, and the decay time constant is called fluorescence lifetime or fluorescence decay time (NS). Due to the varying fluorescence lifetimes at different environmental temperatures, the environmental temperature can be determined by measuring the length of the fluorescence lifetime.

Product Introduction

The AWDS-770 fluorescence fiber thermometer is a temperature measurement system based on the principle of fluorescence fiber temperature measurement. This product is developed specifically for the power industry to meet the requirements of online monitoring of generator temperature. It can achieve online monitoring and control of temperature at measuring points inside the generator, with high precision, stability, and reliability, even in special industrial environments with high voltage, high current, and strong electromagnetic interference. This system has inherent safety in high voltage and electromagnetic environments.

The system consists of a main thermometer and multiple expansion tanks for thermometers. The main thermometer is connected to the expansion box of the thermometer through RS485 or optical fiber to form a temperature measurement system. For a single system, its capacity can be expanded to cover 250 measurement points. Multiple systems can be connected through web servers to form a larger system, whose capacity can be expanded to cover any number of temperature measurement points. The main thermometer has functions such as temperature display, temperature warning/alarm, system fault monitoring, alarm setting, communication setting, historical data storage, temperature calibration, PC communication, etc.