How to enhance and improve the reliability of RTD temperature measurement system for hydropower generating unit

How to enhance and improve the reliability of RTD temperature measurement system for hydropower generating unit 2019 - 06 - 19 hydroelectric generating set features: (RTD temperature measurement system 1) Running time is long, not easy to maintain. Bearing temperature RTD usually should not be installed in a narrow space maintenance replacement, although the unit start-stop frequency ( Pumping power during the day evening) , but usually only when overhaul to have the opportunity to cover to maintain/repair bearing RTD. Unit in accordance with requirements of the state overhaul, overhaul cycle will be longer and longer, it's not good to long-term stable operation of the RTD. （ 2) Important degree is high. Thrust bearing ( Including upper/lower guide bearing) Is the key for the pumped-storage unit temperature testing point, the RTD is primary means of monitoring the running state of the thrust bearing, so the temperature signal often require cast protect, importance is self-evident. （ 3) Poor working conditions. Or in the thrust bearing, the up/down guide bearing RTD, for example, RTD and its wiring soak for a long time in high temperature lubricating oil, the oil film left on the speed and the impact is very big, coupled with the violent vibration of the unit, interfere with the normal service life of the RTD certain negative impact. （ 4) Strong electrical/magnetic interference. Has reached 700 mw large hydroelectric generating set, which produce high voltage/interference magnetic field on the temperature measurement system is very serious, especially for the upper guide and the generator thrust bearing, RTD temperature measurement components such as easily disturbed, lead to unstable temperature measuring signal, and sawtooth wave, spike, jump and other anomalies. （ 5) The temperature measurement system of the intermediate links, connection wire length. A set of thrust bearing from RTD temperature measurement system to the monitoring center for more than 400 meters, the middle after five terminal boxes, and different length of the signal conductor, so many links and signal wire, as long as any link between problems will affect the temperature measurement system to work normally. Enhance and improve the reliability of RTD temperature measurement system countermeasures: through analyzing pumping unit RTD storage failure mechanism, in addition to temperature measuring RTD itself fault, about 40% of the failures are caused by coupling, lead to abnormal signal lines and other reasons. Therefore must be from RTD on the installation of the manufacture, use and daily maintenance, and improve the reliability of the temperature measuring system. （ 1) USES the high quality of RTD - Pt100 chips. Although platinum resistance temperature resistance material is superior to other materials, but platinum resistance chip quality is also different. Made of Pt100 chip sputtering lithography process, have the characteristics of small temperature drift, high long-term stability, and has good resistance to impact and vibration resistance. In order to improve the Pt100 chip pins and lead wire or built-in reliable welding wire and good mechanical properties, platinum and nickel alloy widely used Pt100 chip pins, so as to ensure the reliable connection of after welding wire and good mechanical properties, which can effectively avoid the wiring inside the RTD disconnect occurs. （ 2) Using special wires. RTD and lead long soak in the lubricating oil will appear insulation harden brittle phenomenon, the reason is caused by the unreasonable conductor outer insulation material, such as when the outer insulation of the wire is PVC material, oil resistance, good heat resistance performance is bad. Especially in the occasion of higher temperature, the oil resistant performance will be greatly reduced and harden, brittle phenomenon, affect the service life of the RTD. So you should choose oil resistant, high temperature resistant fep conductor, it has good oil resistance, corrosion resistance and heat resistance, can be in - 250 ~ 250 ℃ temperature in use for a long time. （ 3) In the combination of RTD and wiring and protection devices. In order to solve the problems of the conductor is the root of bolt, should according to the field situation, choose a different form of protection, such as conical spring protection pipe, corrugated pipe and sheathed wire extension protection, etc. Developed in recent years to embedded within the RTD fill in high purity magnesium oxide, both heat conduction and insulation performance, the coat is made of stainless steel, high temperature resistance, corrosion resistance, impact resistance and vibration characteristics, such as good mechanical properties can be arbitrary bending, greatly improving the service life and temperature measuring reliability of RTD. （ 4) Temperature resistance and the integration of the wire shielding. Theoretically the magnetic field is much more difficult than the electric field shielding, for strong magnetic field interference, mesh screen is the most effective solution. Due to the thrust and the upper guide bearing near the generator, the strong electric field, especially in strong magnetic field produced by the magnetic flux leakage of RTD interference is very strong, so the shielding measures is particularly important. Temperature measuring system of intermediate links, the wires are long, be especially careful when wiring, require the wires on each link of reliable connection, the shield is not allowed to shield the middle connection disconnected, lifted the lid open the phenomenon such as terminals, and keep the shielding layer of single point grounding measures. （ 5) Change the way of RTD signals. For individual interference is strong, difficult to guard position, can add RTD - at the scene Pt100 temperature transmitter, converts Pt100 resistance signal to the nearest 4 ~ 20 ma signal, because the 4 ~ 20 ma signal has a strong anti-interference ability, thus can effectively eliminate the interference of the signal transmission in the process of produce, according to the monitoring system of temperature back to normal. （ 6) To optimize the temperature protection logic. To the problem of single point temperature protection, can increase the rate of RTD open and protect and increase the bad value judgment, and other functions, improve and improve the reliability of temperature protection system. The temperature protection of important signal should as far as possible to use 2 of 2 of 2 or 3 judgment logic, eliminate caused by single point temperature abnormal signal unit tripping accidents. （ Source: the home of hydropower station)