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Diesel generator sets are widely used in places where there is no mains electricity supply and where uninterrupted power supply is required, such as telecommunication systems, power systems, radio and television system stations, computer rooms, banks, hospitals and other units. It is very important for diesel generator sets to realize computer automatic monitoring and unified management, which helps reduce the work intensity of duty personnel, improve work efficiency, and improve management level.
1 System structure
The system structure of the diesel generator remote monitoring platform is shown in Figure 1.
The diesel generator set is connected to the telephone line via the MODEM, and then connected to the RS-232 serial port of the monitoring host via the MODEM at the other end of the telephone line.
Many county-level bureaus and subordinate stations have SDH channels connected. If there is an additional RS-232 serial port, data can also be transmitted through the SDH channel, thereby eliminating the modem on both sides of the telephone line, which is equivalent to the RS-232 serial cable directly Connected.
If there are multiple diesel generator sets in a subordinate station that need to be monitored, if the telephone line permits, each unit can be assigned a telephone line, each occupying an RS-232 serial port of the monitoring host. If the telephone line is limited, each diesel generator set in the station can also be connected into a network through the RS-485 bus, through the RS-485 / RS-232 converter, and then connected to the MODEM (see Figure 2), through a telephone line Connected to the monitoring host, only occupies an RS-232 serial port of the monitoring host, each unit is assigned an address, the monitoring host depends on the address to distinguish the unit, and each unit is monitored by the same telephone line in turn, but this will reduce the monitoring system Speed ​​of response.
The RS-485 bus is a two-wire half-duplex serial bus, which uses twisted-pair wires to transmit data in a balanced differential manner. Its main features are: fast transmission rate, up to 10M bits per second; long transmission distance, up to 1200 meters ; Strong anti-interference ability, driving 32 nodes at long distance in noisy environment.
2 Diesel generator set monitoring module
Each diesel generator set is equipped with a monitoring module, which can be used for computer monitoring of the diesel generator set through a serial port. Various signals are taken from the diesel generator set electrical control box.
We use 80C552 single chip microcomputer as the monitoring module control, using large-scale integrated circuits, and combined with advanced design technology. The monitoring module is equipped with dual watchdog circuits to ensure that the system can automatically resume work in the event of an unexpected crash, which is extremely important in the case of unattended operation.
The diesel generator set monitoring module measures the unit output three-phase voltage, three-phase current, unit frequency, unit speed, oil pressure, cooling water temperature, fuel oil level, unit starting battery voltage, output power and other operating parameters and sends it to the monitoring host as needed. The measurement sensors of cooling water temperature, oil pressure and other parameters are generally not linear, and the sensors selected by different diesel generator manufacturers vary greatly. The monitoring module saves the data table sent by the monitoring host and cools the collected data according to the table. Parameters such as water temperature and oil pressure are linearized to adapt to different sensors. The monitoring module has a power-off memory, which can save a large number of work and control parameters.
When the measured operating parameters exceed the set upper and lower limit alarm values, the monitoring module controls various actions of the diesel generator set according to complex control logic: starting, stopping, ATS conversion, etc., and various alarm information and each of the diesel generator sets Various status (auto / manual status, running / stop status, mains / oil engine ATS status, oil engine / oil engine ATS status) report monitoring host.
The monitoring host can also remotely control the unit's startup, shutdown, emergency shutdown, mains / oil machine ATS conversion or oil machine / oil machine ATS conversion, etc. as needed.
All settings of the monitoring module of the diesel generator set can be done on the scene through the panel keyboard, or by the monitoring host at a distance through the serial port. The monitoring module provides two interfaces: RS-232 and RS-485. There are two models of the General Administration of Telecommunications Protocol and the MODBUS protocol. It uses 10-bit asynchronous serial communication (start 1 bit, data 8 bits, stop 1 bit, no verification) Bit), the data transmission rate is 1.2kb / s—19.2kb / s optional, the monitoring host and the monitoring module use a strict master-slave method to exchange data (the monitoring module will only return the corresponding after receiving the command from the monitoring host Data, but will not actively send data to the monitoring host). This design is very suitable for building our remote monitoring platform for diesel generating sets.
The monitoring module of diesel generator set has formed a series of products according to the different strengths of the function to meet different needs. The monitoring module itself has a flexible structure and convenient function expansion.
3 Communication protocol
We use two communication protocols: the General Telecommunications Administration Communication Protocol and the MODBUS Communication Protocol.
The communication protocol of the General Administration of Telecommunications refers to the "Communication Protocol of the Front-end Intelligent Equipment of the Centralized Monitoring and Management System of the Power Supply, Air Conditioning and Environment of the Communication Bureau (Station)", and the encoding method is ASCII code. The information transmission mode is asynchronous, with 1 start bit, 8 data bits, 1 stop bit, and no check. Transmission baud rate is 19.2KB / S, 9.6KB / S, 2.4KB / S, 1.2KB / S, 0.6KB / S, 0.3KB / S optional.
The coding method and information transmission method of the MODBUS communication protocol are the same as those of the General Administration of Telecommunications.
The MODBUS protocol is described as follows:
Command format: AA, CC, SSSS, WWWW, LRC, CR, LR
AA: address (two bytes);
CC: Command (two bytes);
SSSS: data address (four bytes);
WWWW: data (four bytes);
LRC: check code (two bytes);
CR: Enter;
LR: Line break.
Response format: AA, CC, RENUM, DATA, LRC, CR, LR
RENUM: returns the number of bytes of response data;
DATA: return data;
The rest of the explanation is the same as the command format.
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