The electrical monitoring function of generator set incorporated into the engineering application of DCS
CARBONS TECH&CREATION(HENAN) INDUSTRY CO.,LTD , https://www.carbonmoldedgraphite.com
First, the characteristics of electrical systems and DCS requirements
1.1 Characteristics of Electrical System Control
(1) Electrical equipment Relative to thermal equipment, there are few control objects and the operating frequency is low.
(2) Electrical equipment protection and automatic devices require high reliability and fast operation speed.
(3) The interlocking logic of electrical systems is less than that of thermal engineering, but the operating mechanism of the equipment itself is complex. Therefore, the integration of the genset electrical system into the DCS for monitoring requires that the control system must have high reliability.
1.2 Requirements for DCS
(1) The unit unit realizes the full-cathode ray tube (CRT) monitoring of the furnace electromechanical system and performs the interlocking protection and locking of the electrical system. The requirements are not only real
It is now normal to start and stop and run operations. It also requires real-time display of various data and conditions under abnormal operation and accident conditions, and provides corresponding operation guidance and emergency response measures to ensure that the electrical system is automatically controlled in the safest and most appropriate conditions. Work under.
(2) The DAS of the DCS shall be capable of continuously acquiring and processing all important measuring point signals and equipment status signals related to the electrical system. Can perform power generation
Machine-transformer group (transformer group) and factory power supply system control and alarm, when the DCS power supply interruption and communication interference and other abnormal work
When it is in a state, its outlet relay does not malfunction.
(3) The DCS should be able to provide operating instructions for the operator and at the same time block the wrong operation. All operations should be confirmed by the operator twice.
The logic lock function cannot be changed by the operator.
(4) DCS should be able to realize sound and light alarm when abnormalities and faults occur in electrical equipment, and the signal system can realize repetitive actions; at the same time, it should have operation display, alarm display, accident recall record (SOE), trip list, and historical data. Features such as storage and retrieval.
Second, monitoring objects and scope
All electrical systems in the main building from the booster station (excluding the booster station) to the main plant side are monitored by DCS.
(1) Transformer group system (excluding the transformer's own ventilation system)
Data acquisition and monitoring: Generator stator three-phase voltage and current, generator rotor voltage, current, excitation manual cabinet, automatic cabinet output current, main exciter excitation voltage, generator active, reactive, frequency, power factor, main transformer High-voltage side three-phase current, neutral point current, main transformer oil temperature, winding temperature, high-pressure transformer oil temperature of the factory; control of the main circuit breaker of generator-transformer group, generator synchronous control, generator excitation system adjustment control, relay protection device Action alarm.
(2) Booster Station System (220kV)
Main transformer 22OkV side circuit breaker, isolation switch control, partial grounding knife status monitoring, switching knife breaker closing and closing fault indication, 220kV system bus voltage data acquisition and monitoring.
(3) High- and low-voltage factory power supply systems (including factory power supply normal switching control, referring to 6kV and 400V systems)
Plant power supply system data acquisition and monitoring: bus voltage, branch current; factory power supply system switch on/off status monitoring, fault alarm.
(4) DC system and uninterruptible power system (UPS): DC bus voltage, UPS fault and alarm, output voltage monitoring.
Electrical main protection, synchronization, fast cutting, excitation, fault recorders and other devices are complicated and have high security levels and are difficult to replace with general-purpose DCS hardware. Therefore, special devices are still used, but they have to interface with DCS. The conventional method uses a hard interface. The reserved protection and automatic special devices mainly include: hair change protection device; automatic synchronizing device (ASS); automatic voltage adjustment device (AVR); fast power supply device for factory use;
The electrical systems of the auxiliary systems outside the main plant, such as coal transportation, water, electric dedusting, and ash removal, are included in the auxiliary system DCS.
Third, the realization of electrical monitoring function
In the DCS reconstruction, the NETWORK-6000 distributed control system platform of British Continental was adopted. The process control operation level of this system consists of an engineer station and an operator station, which can complete data acquisition, continuous control, sequence control, and data management (including real-time display , alarms, reports, trends, history collection, etc.), the operator stands on the standard screen and the user configuration screen to collect and display the unit operation information for the operation personnel to monitor and control the operating conditions of the unit. Has a powerful control, monitoring capabilities and excellent man-machine interface.
3.1 I/O measuring point [2]
The total amount of I/O monitored by a 135MW generator set and factory power supply is about 400 points. See Table 1 for the distribution of major I/O measurement points. 
The electrical monitoring screen of a unit is mainly composed of five components: (1) electrical main system; (2) generator excitation adjustment system; (3) 6kV factory power supply system (including work and standby); (4) 400V plant Power system (including working and standby); (5) DC system.
3.3 DAS and Surveillance
On-site voltage, current, power and other analog electrical signals are converted into 4 ~ 2OmA current signals by the electrical transmitter and sent to the T122 card;
On-site circuit breaker auxiliary contacts, isolation switches, grounding switches and all faults and abnormal alarms of the electrical equipment, relay protection action signals (DI points) are sent to the T140 card, via I/O modules. After processing, it enters a DPU T103 to participate in various logic controls. In order to make the contact signals involved in the logic control reliable, all device state acquisitions are hard-wired.
3.4 Implementation of Device Level Control Functions
In the DCS, the control of the electrical system mainly refers to the circuit breaker, isolation switch, closing and closing control. The control logic and blocking of this part of the equipment are all incorporated into the DCS.
IV. Problems and Suggestions
(1) After the plant power supply control is incorporated into the DCS, no standby operation switch independent from the DCS is provided. When the conventional new unit installs the power supply for the inverted plant, the DCS has not yet been put into operation. At this time, the high-voltage startup/preparation, high / Low-voltage factory power supply operation cannot be achieved, so requires DCS equipment installation, commissioning and investment
During the construction period, adjustments must be made. While installing and debugging the factory power supply equipment, installation and commissioning of the DCS should be carried out to meet the requirements for trial operation of the power supply for the electric branch factory and the various process systems in the factory.
(2) The contacts at the site need to be fed into the DCS cabinet with cables. Therefore, a large number of control cables are needed. It is recommended to use a field bus at 22OkV boost stations and 6kV, 400V switch rooms in places where electrical I/O points are concentrated. Add 2500 remote cabinets and connect the signals to the decentralized control unit through optical cables. This can save some investment.
(3) The computer-based protection device, excitation device, synchronous device, and quick-cut device of the electric generation and transformation group have all been computerized and have communication interfaces. The communication function is strong, and the signals of these devices can be communicated with the DCS in communication mode. This reduces the number of I/O points and cables and saves investment. However, it should be noted that the communication port and protocol must be unified during the tendering process of the equipment, and the DCS manufacturers must maintain contact with the manufacturers of the special equipment. It is advisable to carry out a joint commissioning before delivery to avoid errors.
(4) In order to reduce the number of optical plates on the control total disk (BTG disk), the electrical part of the BTG disk only has two accidental signals and an early warning signal. Which kind of protection action or what kind of warning signal is on the CRT? It will be automatically displayed to remind the branch staff. The main meter on the disk has a frequency meter, active power
table. There are 4 sets of buttons on the operation console: the main circuit breaker of the transformer substation, closing button, MK closing button, 6kV factory power switch button (2 groups), which can be used by the operator to achieve safety when the DCS crashes. Stopped.
(5) For the control of the common system of the 2 units, a special control unit is set up for the public equipment of Units 8 and 9. The configuration of the utility system in the DCS is not only connected to Unit 9 but also to Unit 8 and can be passed through the software. The DCS on which the unit is selected is controlled on the common part, but only one set of DCS is allowed to control the common equipment at the same time, and this kind of operation control power can be switched. Therefore, the normal operation of another unit will not be affected when any unit is overhauled.