Keywords:: Wireless temperature measurement; high-current circuit breakers for low-voltage electrical appliances; Power plant safety
0 Introduction
Hongjiang Power Plant has installed 6 single 45MW bulb through-flow units, with a capacity of 270MW, which is a domestic single-unit capacity bulb through-flow unit when it is put into operation. The voltage used in the power plant is 400V, and the original 400V low-voltage circuit breaker cabinet is a low-voltage GCY type combined withdrawable switchgear produced by Henan Xinxiang Yubei Electric Appliance Factory, which has been in operation for 13 years. With the extension of the operating life, the equipment continues to age, and in recent years, there have been frequent poor contact between the circuit breaker connector and the busbar, and the heat generation during heavy load causes the circuit breaker connector to burn and deform. Previously, there was no special 400V high-current circuit breaker temperature measurement equipment in the power plant, and the above defects were found through manual temperature measurement three times a day, because it was not 24-hour uninterrupted monitoring, so the discovery of these defects had a certain lag time. In addition, there are many detection points, the detection location is complex, and manual temperature measurement is time-consuming and laborious, and even threatens the personal safety of temperature measurement personnel.
1.1. General introduction of wireless temperature measurement system.
1.2. The main equipment of the wireless temperature measurement system.
2) Centralized display device. Automatically collects and displays the temperature data sent by the wireless temperature sensor, and uploads the received data to the temperature measurement background after receiving the read command from the temperature measurement background.
2. The main functions of the wireless temperature measurement system
1) The ID number of each temperature probe needs to record the installation location of each wireless temperature sensor when it is actually installed and used, and it is stored in the temperature measurement background database and centralized display device together with the number. The wireless temperature sensor automatically transmits the temperature data of the monitoring point at certain intervals, and the temperature data of the area is collected and recorded by the centralized display device and transmitted to the temperature measurement background through optical fiber, and the abnormal alarm is immediately found, which avoids the lag, large workload, unsafe and other problems of the manual temperature measurement method, which is very suitable for the power plant with a large number of monitoring points, improves the degree of automation of the power plant, and reduces the cumbersome work of manual temperature measurement.
3) Technical indicators of wireless temperature sensor. The measuring temperature range is -40-+125. Measurement accuracy: 0-80 accuracy error is 1, 80-150 accuracy error is 2. The probe has a lifetime of 5-8 years. The dielectric strength of the sensor is AC2KV1min. Flame retardant performance: wireless temperature sensor 250 high temperature resistant, insulating flame retardant type. Dimensions: The sensor box part is 80mm (length) 405mm(width) 148mm (height), the battery compartment part is 685mm (length), 23mm (width), 22mm (height) The operating frequency is 24ghz～433mhz。The transmission distance is 250m (unblocked).
1) Centralized display of the functional characteristics of the device. The use of high-precision wireless transmission not only facilitates the installation and maintenance of the system, but also reduces the impact on the safe operation of the power plant, greatly improves the safety and flexibility of the system, and has strong long-term stability in the high temperature and high humidity environment. Scalability, each temperature measurement and receiving communication terminal has a receiving capacity of 100 temperature measurement loops (each loop contains 3 temperature measurement sensors), leaving enough space for future expansion without adding new receiving devices. The instrument has EEPROM inside, and the set parameters will not be lost when the power is off; With watchdog chip, the program runs and automatically resets; RTC real-time clock; It has an Ethernet interface. The measured values are displayed directly by the high-brightness TFT LCD display; The alarm temperature setpoint is set directly on the panel. The sensor is automatically detected and the control element is automatically switched off when there is no sensor signal. It is easy to install and can be installed on a control cabinet or fixed to a wall or other objects. It has strong anti-interference ability, and can accurately identify and receive the temperature signal from the probe without being affected by other equipment.
2.3. Functional characteristics of temperature measurement background.
1) It can observe the changes in the operating temperature of the electrical contacts such as the primary plug and cable glands of the circuit breaker in the switch cabinet in real time and intuitively through the background.
3) The alarm temperature can be set according to the actual situation of the user, and the alarm window can pop up for the monitoring point that reaches the warning value and alarm value, and the voice prompt alarm. There are several ways to set the alarm value: early warning temperature (exceeding the upper limit), alarm temperature (exceeding the upper limit), a certain point temperature exceeding the three-phase temperature difference (horizontal comparison exceeding the limit), and a sudden change in temperature at a certain point (trend exceeding the limit).
3. Advantages of wireless temperature measurement technology.
2) A centralized display device is set on site, and each temperature measurement channel can be set separately for early warning and alarm setting, and with dry contact output. In order to facilitate the collection of circuit breaker temperatures, a centralized display device is installed in each distribution room. The device has the functions of over-temperature sound and light alarm, dry contact alarm, inspection, etc., the name and temperature threshold of each group of measured points can be set independently, when the detected temperature exceeds the set threshold, the over-temperature alarm information will be automatically issued, and the alarm level (early warning and emergency alarm) can be adjusted according to different alarm states, and the maintenance personnel can be quickly notified to deal with the fault in time.
4.1. Application scenarios.
The temperature measuring device of electrical contact ** is suitable for the temperature monitoring of cable joints, circuit breaker contacts, knife switches, high-voltage cable intermediate heads, dry-type transformers, low-voltage and high-current equipment in high and low voltage switchgear, so as to prevent excessive contact resistance caused by oxidation, loosening, dust and other factors in the operation process and heat up to become a potential safety hazard, improve the safety guarantee of equipment, reflect the operation status of equipment in a timely, continuous and accurate manner, and reduce the accident rate of equipment.
Control operation (circuit breakers, disconnectors, taps, reset).
Event sequence recording SOE (opening and closing recording, protection and automatic device action sequence recording).
Clock synchronization (Beidou GPS nanosecond level, meeting the standard clock error of the interval layer subsystem is not more than 1ms).
Interface with other devices (microcomputer protection, power meter, DC panel, fault recorder, analog screen, scheduling).
In the renovation of the 400V low-voltage system of Hongjiang Power Plant, a set of 400V low-voltage high-current circuit breaker wireless temperature measurement system has been built, which realizes 24-hour uninterrupted monitoring of most of the large-load circuit breakers of Hongjiang Power Plant, and can timely find the unsafe operation conditions such as aging, poor plugging, loose joints, surface oxidation, galvanic corrosion, overload and other unsafe operating conditions of the important circuit breakers of the 400V low-voltage system of the plant in time, and improve the safe operation level of the 400V low-voltage system for the plant. At present, the temperature measurement system is running stably, and the heating phenomenon of the power panel next to the machine and the power plate circuit breaker in the DC panel room has been found and dealt with in time for many times, ensuring the safe and stable operation of the power plant.
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About author:YI Yunheng, male, undergraduate, Ankerui Electric Co., Ltd. is mainly engaged in the research and development and application of wireless temperature measurement.