Application of Intelligent Motor Controller in Power Plant

Abstract: The traditional low-voltage motor protection is achieved through the relay protection secondary circuit. With the rapid development of electronic technology, some motor controllers have been fully protected from the circuit. According to the characteristics of the motor protection of the power plant auxiliary control equipment and its control requirements, combined with the application of the ARD3 intelligent motor controller in the power plant low-voltage motor protection and control, comprehensively introduces the ARD3 intelligent motor controller product features and intelligent protection, Measurement, control and communications, etc., for reference in engineering design.

Keywords: motor protection, intelligence, communication

With the advancement of science and technology, the use of electrical equipment in China's power plants has gradually increased, and the normal operation of electric motors has become a prerequisite for the normal operation of other equipment. Therefore, the ability to rationally select and use electric motor controllers is a normal industry. The performance of the on-site production work is only able to ensure that the work flow of the entire industry will not be disturbed and can operate normally only on the basis that the motor functions normally. In thermal power plants, the control principle and application of low-voltage motors have always been a technical problem in thermal power plants [1, 2].

In the protection design of the power plant electrical equipment, the application and protection configuration of the low-voltage motor can be designed in various schemes. For the past, thermal relays, circuit breakers (or fuses) were used as motor overload protection, phase protection protection, short circuit protection and Control elements, due to the constraints of various conditions such as inflexible communication functions, have been unable to meet the requirements of the ever-evolving power plant automation production, and new intelligent motor controllers can realize heavy-load start-up to achieve motor temperature protection, and also provide A variety of monitoring and control functions and a variety of motor control modes can meet the motor protection and control requirements, and effectively ensure the safe operation of the motor. This article describes the practical application of ARD3 intelligent motor controllers in power plants.

In the electromechanical industry in China, the motor is widely used. The total amount of electricity consumed in the electric motor accounts for a large part of the electric power, and various types of fans, pumps, and air compressors account for more than half of the electric power consumed by the electric motor. The working environment of the power plant motor is rather harsh, and it is often prone to malfunctions such as locked rotor, short circuit, phase failure or long-term overload operation. Therefore, the controller must be capable of real-time protection and control of the motor working in harsh environments to ensure power generation. The normal operation of the factory motor.

According to "Technical Regulations for Power Design of Power Plants for Thermal Power Plants" (DL/T 5153-2002), low-voltage motor applications should be installed with interphase short circuit protection, single-phase ground protection (or single-phase ground short circuit protection), overload protection, and low Voltage protection, phase failure protection [4]. Therefore, the power plant project needs voltage and current full-power parameter measurement, and with communication function, the controller needs to have self-diagnosis output, power-off output, fault record and other functions, and is summarized as the following functions:

1, to achieve a complete motor protection

The controller collects the three-phase alternating current, three-phase alternating current voltage, residual current, PTC thermal resistance, motor power, and other electrical parameters, as well as various motion states during motor operation. To achieve motor starting timeout, overload, blocking, underload, phase failure, three-phase current unbalance, residual current (ground/earth leakage), temperature, external fault, phase sequence, overvoltage, undervoltage, underpower, overpower, tE time and other comprehensive protection, and thus ensure the safe and continuous operation of power plant production work [4].

2, to achieve a variety of motor control

The intelligent motor controller is controlled by the program to realize a variety of different motor starting controls. The operation control permission achieved by the controller includes: 1) RS-485 communication interface realizes remote control; 2) It can be performed through the buttons on the display module. Operation control; 3) Remote control via DCS system control DI terminal; 4) Local control of DI terminal on site.

3, real-time monitoring of motor operation on site

Through the controller, the power plant can observe the voltage, current, frequency and other parameters of the field motor equipment during operation, and the current running status of the motor in real time. The buttons on the operation display module set the startup mode of the power plant's motor equipment (optional manual start, two Step start, two-speed start and protection mode).

4, to achieve communication

The controller can communicate with the host computer management system via RS-485 communication interface through Modbus-RTU or Profibus-DP communication protocol, send information to the background management system in a short period of time and send an alarm signal to the fault information, make the operation The personnel can discover the cause of the fault and eliminate the fault in time, realizing the real-time transmission of the data of the power plant's motor equipment.

ARD3 intelligent motor controller adopts a modular product structure, including main control module, transformer module and display module, and can be equipped with other functional modules and accessories of ARD3 intelligent motor controller according to the actual application in the industrial field. Through the use of ARD3 intelligent motor controller installed in the low-voltage switchgear, with the switch, contactor, motor starter and other electrical components constitute the motor control protection unit, to achieve a remote automatic control, direct control of the scene, LCD interface parameter indication, signal alarm Fieldbus communication and other functions have improved the reliability and stability of the entire control loop while reducing the operator's on-site commissioning and maintenance workload. The anti-slopping and self-starting of the circuit can be achieved through the optional anti-swing electrical module. When the auxiliary power supply of the ARD3 intelligent motor controller is powered off, the controller can be continuously powered for 10 seconds. At the same time, an optional AC380V power supply module is used for control. The place where the AC380V is used as an auxiliary power source.

With the large-scale deployment of power plant DCS systems, realizing remote real-time centralized monitoring of industrial field motors has become one of the key points for achieving industrial automation control. Figure 1 shows the field bus layout of ARD3 intelligent motor controllers in power plant applications. ARD3 intelligent motor controller provides users with RS485 (Modbus-RTU/Profibus-DP) communication interface, which can collect the three-phase AC voltage, zero-sequence current, thermal resistance value, motor power and status monitoring information of the motor on the industrial site. Collected into the field bus, the operator can monitor the operation of the industrial site in real time through the host computer, and realize the DCS remote control of the operator's operation interface [5].

Fig. 1 Field bus layout of ARD3 intelligent motor controller

As shown in figure 2 of the ARD3 intelligent motor controller engineering typical application plan diagram, after the circuit is powered on, the controller collects the switch KK1 signal, and the controller selects the remote control by reading the signal value of the control authority port (14, 15) or Local control of motor starting. As shown in the wiring in Fig. 2, if the signal collected by the controller port (15) is "1", the remote control motor is started; if the signal collected by the controller port (15) is "0", then the local control Motor start. The controller collects the signals of three-phase AC voltage, three-phase AC current, zero-sequence current, contactor working status, circuit breaker working status, and DCS cabinet emergency stop button SA and other electrical components. After the controller processes the circuit, it is calculated by the CPU. After processing, according to the actual production requirements of a variety of protection performance, measurement parameters, control logic, data transmission and other requirements, control the on-site 90L liquid crystal display interface on the motor running status and the power plant electrical equipment control circuit in the display of some important power parameters The value, as well as the operating status of the control switch output, controls the protection and protection of the starting method and operation process of the motor equipment. The analog output (35, 36) of the controller outputs a 4-20mA analog signal. The DCS system reads the analog signal and judges the current operating state of the motor. At the same time, as an individual motor controller device, the realization of in-situ protection is its basic function. The ARD3 intelligent motor controller can feedback the on-site detection parameters to the host computer in real time through the RS485 communication interface (25, 26) to facilitate the on-site maintenance personnel to perform real-time remote monitoring and control of the operating status of each point equipment.

Fig. 2 Typical application scheme diagram of ARD3 intelligent motor controller engineering

Fourth, the power plant selected ARD3 intelligent motor controller effect

Protecting the operation of the motor and ensuring continuous and uninterrupted operation of the motor are critical to production. The benefits of using the ARD3 intelligent motor controller for the power plant are:

1. High network flexibility for easy control

In the power plant, the motor controllers have the same weight as the power distribution products. They are inseparable during the implementation of the networking process. ARD3 intelligent motor controller provides RS-485 communication interface, and realizes a variety of protocol options (Modbus-RTU/Profibus-DP). Through communication between RS-485 and host computer, it can be easily realized by engineers through computer background. Remote automatic control and online monitoring of equipment operating conditions.

2, real-time display parameters to facilitate on-site inspection

The ARD3 intelligent motor controller adopts a modular product structure. The display module is installed in the DCS cabinet. The current status of the motor can be observed in real time through the LCD interface, facilitating the user's maintenance and control of the on-site motor.

3, energy saving

The role of the motor controller in saving energy and reducing consumption began to be emphasized by everyone. The ARD3 intelligent motor controller can automatically stop when the motor equipment is under operating conditions such as underload, effectively avoiding the waste of energy and saving money for the company.

4, information centralized

The user can use the communication module to monitor the running status of each motor in the background in real time and observe the operation parameters of the device at any time, such as motor current, voltage, motor running status, motor power, etc. The user can analyze the collected information. The real-time processing of the motor running status of each device improves the safety and reliability of the entire control system.

5, intelligent automatic protection

ARD3 intelligent motor controller is flexible, alarm and protection parameters can be preset by software according to the actual operating conditions of the power plant motor equipment to avoid different values ​​affecting the actual production. After the user selects the ARD3 intelligent motor controller, once the on-site motor fails, the controller controls the motor to stop running in time, and makes corresponding indications and records for various fault information to facilitate the user to query the fault information. In the event of a grid fault, the voltage is momentarily fluctuating or the short-term power failure is restored. With the anti-slopping function, the motor controller can be restarted.

6, record motor fault information, easy to analyze the problem on the spot

Most of the motor equipments working in power plants are in high temperature, humidity and dusty conditions. They are prone to failures. Once a failure occurs, maintenance personnel find it difficult to find the cause of the failure and require a certain amount of time, manpower, and material resources. Analyze the cause of the failure. The ARD3 intelligent motor controller has powerful fault and event records, operation management information to save a lot of time for on-site maintenance personnel, improve the work efficiency of maintenance personnel, and further improve the performance of the entire control loop.

The use of ARD3 intelligent motor controllers in low-voltage motor protection and monitoring systems for power plants enhances the automation level and reliability of the control loop while also improving the overall efficiency of the company and achieving unity of reliability and economy. Moreover, with the continuous development of technology, ARD3 intelligent motor controllers will play an increasingly important role in the protection and monitoring of low-voltage motors in power plants.

references:

[1] Man Lianshan. Application of Low Voltage Motor Protection in Thermal Power Plant. Electronic Technology and Software Engineering. 2014(2)

[2] Yan Gang, Guo Yingchen. Application of intelligent motor controller in power plants. Huadian Technology. 2008 (3)

[3] Zhou Zhong. Product Selection and Solution of Smart Grid User-end Power Monitoring and Power Management System[M]. Beijing Machinery Industry Press. 2011.10

[4] Hu Gang. The application of low voltage motor protection in thermal power plants. Enterprise Technology and Development. 2009 (16)

[5]ZHANG Yuwei. Application of ST500 intelligent controller in low-voltage motor protection of power plant. Science and Technology Wind. 2011(6)

About the author: Yang Xin, female, Ankerui Electric Co., Ltd., the main research direction for motor protection and energy-saving control, mobile phone: 18702111791 , landline, QQ: 2880581273