Fault finding method of electrical equipment in th

Cement plant electrical equipment fault finding methods

Abstract cement plant electrical equipment has many types, large capacity, high voltage level, and it is difficult to maintain electrical equipment. Power failure is an integral failure of electrical devices, with great hidden danger and small accidental factors; The structure, performance, category and function of electrical equipment and components are very different, and there is no fixed mode to find their faults. When dealing with faults, it is necessary to distinguish between frequent faults and accidental ones; Whether it occurs in the starting state, running state or speed regulation state; The scope of the fault should be reduced through preliminary analysis

1. Search of power supply failure

power supply failure. In electrical failure, most failures are obviously dangerous, such as line open circuit, and the equipment cannot work; The line is short circuited, and the short-circuit current effect is obvious. However, some power supply faults are not obvious, or it is difficult to find out the fault scope from its manifestation. For example, the waveform of AC power supply does not meet the requirements, which can increase the calorific value of electrical equipment and reduce the motor speed, but the harm of its failure can not be ignored

2. Finding electrical faults of equipment and components

equipment and its components are the core part of electrical devices, and its basic functions are to send, receive, process, convert, execute, and output electric energy or electrical signals. Electrical faults mainly occur in equipment and components. Therefore, finding electrical faults of equipment and components is the most important content. There are many kinds of electrical equipment and components in the cement plant, such as various motors, servo actuators, contactors and relays in the control circuit, various temperature, pressure, material level and weighing sensors of the automatic control system, as well as special instruments in the cement industry, such as high-temperature cameras, colorimetric pyrometers, gas analyzers, etc., all belong to the scope of electrical equipment and components. Its structure, performance, category, function, etc. vary greatly. In fact, it is difficult for us to find a fixed mode to find the fault. The following will be classified and introduced

2.1 automatic control

2.1.1 signal classification

the signals received and sent by each control station are basically divided into two categories: digital (SWITCHING) signals (DI, do) and analog signals (Aiao). Digital signals mainly include: Central selection, preparation, operation feedback, fault, limit, speed measurement (belt conveyor also has deviation and rope pulling), actuator limit, torque, baffle position, various detector alarms, field temperature switches, pressure switches, material level switches, etc. of each MCC control cabinet on site; Analog quantity signals (generally O ~ 10 V or 4 ~ 20 mA) include: speed, temperature, pressure, flow, liquid level, material level, stroke, opening of baffle actuator, gas content of gas analyzer, weighing capacity of various scales (belt scale, rotor scale, idler scale, silo, weighbridge), feeding capacity, etc

2.1.2 fault finding

for the cement production industry, in some occasions, there will inevitably be the impact of dust, vibration, high temperature and other environmental factors, and the on-site signals are mostly generated by various contactors, intermediate relays, speed measurement, switches for various types of purposes, measuring instruments and meters, etc., which will inevitably cause problems in the harsh working environment for a long time. When there is a fault, we should focus on two aspects to find it

2.1.2.1 digital signal fault finding

first, check whether the power supply and control power supply are normal; According to the comprehensive analysis of the fault phenomenon and the fault information provided by the central control room, focus on checking whether the starting and stopping conditions and soft and hard interlocking conditions of the equipment are met; Whether the contacts and contacts of components in the equipment control cabinet are intact, whether the logic control circuit is intact, and whether the wiring is loose; Whether the I/O terminal wiring in the field control station is loose, whether the control signal is sent out, and whether the signal fuse is fused; If it is a pressure, flow or temperature switch, check and verify whether the real value on site meets the action requirements; If it is an on-site intelligent device or instrument, it is also necessary to check whether there is fault, alarm information, and whether the parameter settings are correct; Whether the on-site equipment cannot be started due to failure, and whether the protective device acts. It is believed that on the basis of in-depth understanding of the equipment control principle, combined with experience and based on the above principles, digital signal faults are easier to find

2.1.2.2 analog signal fault finding

(1) for signals with inaccurate response, such as temperature, check the thermal resistance, the insertion depth and position of thermocouple, whether the surface is skinned, whether the wiring is loose, corroded, etc; In case of pressure and flow signals, check whether the measuring pipeline is blocked, leaking, the position of each valve, whether the transmitter is in good condition, etc; In case of weight, speed, material level and other signals, check whether the sensor is in good condition, whether the wiring is correct and tight, and whether the setting is correct; If it is an electrical parameter signal, check whether each voltage, current transformer and transmitter are normal; At the same time, due to the influence of working environment and electromagnetic interference, all kinds of field instruments inevitably have large or small drift, which requires regular calibration, setting or compensation adjustment, and shielding interference

(2) for signals with wrong response, fault and no indication, it is necessary to focus on checking whether the on-site power supply, wiring terminals, lines or cables are disconnected, whether the measuring equipment is intact, whether the parameter settings are correct, whether there is actually an over range problem, whether all kinds of sensors are damaged, etc. Compared with digital signals, analog signals have complex detection and processing processes, relatively complex equipment, and poor anti-interference ability, and are more vulnerable to the direct impact of the working environment, so it is more difficult to process. However, with the development of electronic technology, the performance of field instruments and equipment has been continuously improved, and their functions have become increasingly powerful. Now most field instruments and meters are digital and intelligent, with self diagnosis function, which makes maintenance and repair convenient and fast

2.2 on site electrical equipment

2.2.1 search for asynchronous motor fault caused by external equipment fault

there are many kinds of external equipment of asynchronous motor, and their faults may cause damage to the motor itself. For example, load failure may cause difficulty in starting the motor, excessive running load, heating, vibration, and even burn the motor in serious cases. Due to the large amount of dust in the cement plant, the electrical contact fault is one of the most difficult faults to find and the largest amount of maintenance on weekdays. If the main contact is falsely connected, this kind of fault will often lead to motor phase failure operation, serious heating and even burning; The ablation and adhesion of the main contact will lead to failure to release, electrify the shutdown equipment, and may cause interphase arc short circuit when the equipment is started, causing serious harm to personal safety and system operation

2.2.2 fault finding of asynchronous motor itself

faults of the motor itself include: bearing damage, which may cause rotor bore sweeping, winding grounding, winding open circuit, winding short circuit, wrong coil connection, rotor bar breaking (for wound rotor, there are also rotor winding broken wire, short circuit, rotor collector ring and brush fault, etc.). The failure of asynchronous motor in cement plant is often caused by poor environment and untimely maintenance. To judge whether a motor has a fault and where the fault is, it is usually necessary to check the working current, temperature rise, speed, sound, smell, insulation resistance, DC resistance and inductance of the motor

2.2.3 finding electrical faults in unreasonable installation

in order for electrical equipment to work normally, in addition to the quality of the equipment itself, reasonable material selection and installation are also crucial. For example, in order to transmit enough electric energy, a power line must meet certain requirements, such as the cross-sectional area of its conductor, the insulation strength and mechanical strength of the line, so as to overcome the adverse effects of external and internal factors and ensure the safe operation of the line without or less failures

there are many kinds of equipment in various production plants, and it is difficult to maintain. These are not the only faults in cement plants, but these are basic faults that can be detected and eliminated

Abstract There are many kinds of electrical equipment in cement plant, with large capacity and high voltage level, and the maintenance of electrical equipment is difficult. Power failure is an integral failure of electrical devices, with great hidden danger and small accidental factors; The structure, performance, category and function of electrical equipment and components are very different, and there is no fixed mode to find their faults. When dealing with faults, it is necessary to distinguish between frequent faults and accidental ones; Whether it occurs in the starting state, running state or speed regulation state; The scope of the fault should be reduced through preliminary analysis

1. Search of power supply failure

power supply failure. In electrical failure, the vast majority of failures have obvious danger, and the error may reach 3 (4) degrees Celsius. If the line is open, the equipment cannot work; The line is short circuited, and the short-circuit current effect is obvious. However, some power supply faults are not obvious, or it is difficult to find out the fault scope from its manifestation. For example, the waveform of AC power supply does not meet the requirements, which can increase the calorific value of electrical equipment and reduce the motor speed, but the harm of its failure can not be ignored

2. Finding electrical faults of equipment and components

equipment and its components are the core part of electrical devices, and its basic functions are to send, receive, process, convert, execute, and output electric energy or electrical signals. Electrical faults mainly occur in equipment and components. Therefore, finding electrical faults of equipment and components is the most important content. There are many kinds of electrical equipment and components in the cement plant, such as various motors, servo actuators, contactors and relays in the control circuit, various temperature, pressure, material level and weighing sensors of the automatic control system, as well as special instruments in the cement industry, such as high-temperature cameras, colorimetric pyrometers, gas analyzers, etc., all belong to the scope of electrical equipment and components. Its structure, performance, category, function, etc. vary greatly. In fact, it is difficult for us to find a fixed mode to find the fault. The following will be classified and introduced

2.1 automatic control

2.1.1 signal classification

the signals received and sent by each control station are basically divided into two categories: digital (SWITCHING) signals (DI, do) and analog signals (Aiao). Digital signals mainly include: Central selection, preparation, operation feedback, fault, limit, speed measurement (belt conveyor also has deviation and rope pulling), actuator limit, torque, baffle position, various detector alarms, field temperature switches, pressure switches, material level switches, etc. of each MCC control cabinet on site; Analog quantity signals (generally O ~ 10 V or 4 ~ 20 mA) include: speed, temperature, pressure, flow, liquid level, material level, stroke, opening of baffle actuator, gas content of gas analyzer, weighing capacity of various scales (belt scale, rotor scale, idler scale, silo, weighbridge), feeding capacity, etc

2.1.2 fault finding

for the cement production industry, in some occasions, there will inevitably be the impact of dust, vibration, high temperature and other environmental factors, and the on-site signals are mostly generated by various contactors, intermediate relays, speed measurement, switches for various types of purposes, measuring instruments and meters, etc., which will inevitably cause problems in the harsh working environment for a long time. When there is a fault, we should focus on two aspects to find it

2.1.2.1 digital signal fault finding

first, check whether the power supply and control power supply are normal; Comprehensive analysis based on fault phenomenon and fault information provided by central control room