Hot Rolled Steel Production Line
IFLS600 and SKMC-8 collect the load current and insulation resistance of the motor, locate the insulation fault, transmit the results to the touch screen for display, and conduct real-time monitoring and alarm for the current load and insulation status of each motor.
Application of Insulation Monitoring and Fault Locating in Hot Rolled Steel Production Line
With the acceleration of industrial modernization, the stable operation of rotating equipment is very important for continuous production enterprises such as steel. Once a failure occurs, it is possible to cause the entire production line to shut down, causing huge losses. This loss can reach hundreds of thousands of yuan per hour. Especially with the adoption of intelligent control systems in the production process, the dependence on the safe operation of key equipment is increasing. Therefore, it is very important to monitor these devices online.
Laminar roller motors are one of the key equipment in the steel production line. Whether they can operate normally directly affects the quality and output of the product. Multiple motors of adjacent rollers with the same speed within the process section form a group, which is centrally driven by a set of speed control devices. The electrical topology diagram is as follows:
The system adopts IT power supply mode (Isolated Neutral System), and the neutral point of the low-voltage distribution system is not grounded or grounded through high impedance. The advantage of IT power supply is that when a single-point grounding occurs in the system, the production can be maintained without power outages because there is no grounding loop. Under normal circumstances, the possibility of grounding on the grid side is relatively small, but due to the harsh environment on site, the roller motor (cable) is very likely to be grounded. However, whether a single-point grounding occurs on the grid side or the motor side, the corresponding non-grounded relative voltage will rise from the phase voltage to the line voltage, which may easily cause the insulation of other equipment on the grid side or the remaining roller motors to deteriorate, causing fires or threatening personal safety. If it evolves into two-point or multi-point grounding, the short-circuit current will cause the inverter to trip immediately, and even cause the grid power supply to be interrupted.
At present, the working conditions of laminar roller motors are relatively complex, affected by high steel plate temperature, large steel impact, laminar water and impurity impact, etc.; secondly, the distance between the roller motor and the speed control device is relatively far, the cable is very long, and the environmental humidity is relatively high, resulting in the insulation of the cable and motor being reduced. As long as one motor in each group of motors has poor insulation, it is easy to cause the single motor to trip and stop, which is easy to scratch the rolled piece and affect the surface quality. The current situation is summarized as follows:
1) There are many rollers, the speed is fast, and the temperature of the strip is high, which leads to large water vapor, high temperature, and easy overheating of the rollers. In this way, the grease is easy to lose, causing the rollers to get stuck and bend and deform.
2) The laminar cooling water splashes on the motor on the operating side, causing water to enter the motor. It is in a high temperature and humid environment for a long time, inducing motor short circuit or single-phase grounding and other faults.
3) At present, the laminar roller motor is driven by an inverter (frequency converter). The PWM pulse voltage dv/dt output by the inverter is very high, and the harsh environment such as high temperature, high humidity, and vibration on site has aggravated the insulation degradation trend of the roller motor, seriously affecting the safe operation of the entire unit or power supply system. At the same time, the harmonic current increases the motor loss.
The preventive measures to prevent the motor from tripping are currently to use the production interval or maintenance period, and the workers use the megohmmeter on site to test the insulation resistance between phases and between each phase and ground one by one. The efficiency is very low and the workload is large. Occasionally, a single motor will trip due to insulation failure and emergency treatment afterwards.
Therefore, it is very necessary to monitor the status of the laminar roller conveyor motor. The traditional solution is to install an IMD (insulation monitor). As shown in the figure above, the IMD can monitor the degradation of the system insulation performance during the first ground fault. When the insulation performance drops to the set value, an alarm is issued to remind the on-duty personnel to handle the fault and avoid power outages caused by the second ground fault.
However, this solution IMD (insulation monitor) can only monitor and pre-alarm the overall insulation performance of the IT system. When the IT system has many electrical equipment or many branches, once a ground fault occurs, the IMD can only qualitatively determine that there is a problem with the system insulation, but cannot determine which branch or electrical equipment has a ground fault, nor can it determine the number of faulty branches. The usual practice is to shut down the system and manually check each branch. This approach is inefficient, does not guarantee personnel safety, and is time-consuming.
Based on the above pain points and combined with the deep technical accumulation in the insulation monitoring industry, Sikcon has developed the IFLS-600 insulation fault locator, which can not only perform overall insulation monitoring of the IT system, but also accurately locate the fault to the specific branch and the number of faulty branches, and upload the data to the host computer or computer. By establishing a laminar roller motor status monitoring system, the monitoring data of all roller motors are analyzed and processed to realize the functions of motor fault early warning and alarm, so as to take corresponding measures in advance to control and prevent accidents, avoid motor damage caused by sudden failures, and affect the rolling rhythm. Motor status monitoring makes equipment maintenance change from passive to active, improves the integrity and utilization rate of equipment, improves the level of equipment management, and also plays a certain role in improving product quality.
This solution solves the following problems
1) Preventive monitoring and fault location of the insulation performance of the laminar roller motor power grid;
2) Automatic collection, remote monitoring, real-time reporting of raw data, analysis data, real-time status, etc.;
3) The specific motor can be located in time when the insulation and load of the equipment are abnormal;
4) When the working state of the equipment is abnormal, the system will alarm and notify relevant personnel in time;
5) Monitor the working current of the motor to understand the working state of the motor;
6) Convenient deployment and flexible docking. It can be docked with other production and operation management systems in the factory;
The overall system architecture is shown in the figure above. This solution uses professional sensor technology to collect the load current and insulation resistance of the motor, perform on-site edge calculations, and transmit the results to the touch screen for real-time monitoring and alarm warning of the current load and insulation status of each motor.
Motor current monitoring transmitter
When the motor or roller bearing is abnormal, there is usually a degradation process. During this process, the corresponding motor current will be abnormal. By monitoring the motor current, the abnormality of the motor and roller bearing can be discovered as early as possible and handled in time. The roller motor adopts a transmission method in which one inverter drives multiple motors. It is impossible to know whether the status of each motor is normal. If one motor is abnormal, it will affect the normal operation of the entire roller motor. Therefore, through adaptive transformation, convenient, accurate, and real-time sensor signals, timely and effective detection of the current of each motor and timely warning are the key.
The solution is equipped with Sikcon's SKMC-8 current transmitter. The SKMC-8 current transmitter is based on the Rogowski principle, precision integrator and digital processing technology to measure the current spectrum components. The flexible coils of different lengths can match any shape of current conductor in the installation method. The current coil can be directly unscrewed and put on one phase winding of the motor. The integrator can be installed on a DIN35mm rail or base plate. With the help of built-in functional modules, RS485 digital signals are output and connected to the Internet of Things or edge collectors.
Insulation monitoring and fault location
In the IT system, the SKIM600FL online monitor continuously sends out measurement signals to perform online insulation monitoring on the system. When the insulation fault occurs for the first time and the insulation resistance is less than the preset alarm value of the SKIM600FL insulation monitor, the SKIM600FL sends out an alarm signal to the host computer. At this time, the SKIM600FL sends out a fault location signal to inject into the power grid. At the same time, the SKIM600FL sends out instructions to the fault location instrument SKIF12 through RS485 communication to work (without SKIM600FL instructions, SKIF12 is in standby mode). SKIF12 has multiple wiring ports that can connect 12 high-precision low-frequency current sensors. The low-frequency current sensors are installed on each branch of the system. In this way, SKIF12 can collect the fault location current of each branch, compare the collected fault location current data with the preset current fault value, determine the problematic branch, and upload this data to the host computer or computer through RS485 for the on-duty personnel to handle the fault.
