The synchronization of the original hydroelectric generating units with the external network and the decomposition and shutdown of the external network are all completed by manual operation. After the installation of the micro-computer controller, the hydro-generator set can be automatically connected to the grid and also has the function of cracking protection by the detection of the micro-computer controller. Our company has three small hydropower stations, the total installed capacity of the three hydropower stations is 1365KW, and there are seven Francis hydro-generators. Before the transformation, when the hydro-generating unit is connected to the provincial power grid through the boost transformer, the operator must observe the synchronous indicator lights, voltmeters, frequency meters and so on for manual closing and grid connection. When provincial power grid and water electrolysis train, operators often have no time to “stop” to cause high-speed operation of hydro-generators, resulting in high frequency and high voltage generated by “flying car” which causes other equipment in the power grid to burn down and damage to their own generating units. After that, a set of micro-computer control device is installed on the original control system of the hydroelectric generating unit to realize the protection of the hydroelectric generating unit when it is connected to the grid automatically and decomposed by speed motor to shut down the hydroelectric unit to no-load state quickly. It is difficult to master the frequency difference and phase angle difference in quasi-synchronous operation. These two factors have the greatest impact on waiting time and impulse current. The process of automatic grid connection is to turn the knob on the panel of the micro-computer controller into the file of the same period, turn on the micro-computer (1-3 or 1-5) and send out the “turn-on” or “turn-off” signal, control the motor forward (KM1) or reverse (KM2), and quickly adjust the speed of the turbine to be equal to the frequency of the grid. When the difference between the generator frequency and the grid frequency is captured by the micro-computer and the phase angle difference enters 20 degrees from large to small, the micro-computer (9, 10) usually turns on the manual closing button of the ME630 circuit breaker of the original PGL control cabinet to issue the closing command to realize the automatic grid connection function.
After self-excitation, the adjusted voltage is basically the same as that of the external network. 2) Put on the power supply of the micro-computer, the micro-computer will automatically control “turn on” and “turn off” to make the frequency close to 50 HZ, and adjust the excitation to make the voltage of the generator set basically consistent with the voltage of the external network. 3) Turn the micro-computer switch to the same period.
The micro-computer controller detects the HHHH signal when the parameters (voltage, frequency and phase) are synchronized automatically through (13, 16) external network and (18, 20) generator terminal voltage signals. At this time, the ME-630 circuit breaker will automatically close. 4) Turn [the same period] back to [normal], and then gradually increase the power generation by clicking on the “open” button.
One is to avoid the generator burning and switch damage under the condition of different step misoperation when manual closing is connected to the grid. The second is to reduce the mental and physical labor of operators. Most of our small power plants, the unit and the control panel are not in the same place, usually one person adjusts the speed next to the unit, the other person operates at the same time in the control panel, so that no one can run back and forth to achieve synchronous grid connection. After the technological transformation, only one person can operate at the control panel to achieve synchronous grid connection, and one person can be fixed in the front pool to “fish grass” to effectively improve power generation efficiency. Rate.
At the same time, reducing impulse current plays an important role in protecting units and prolonging the life of air switches. For some reason, when the provincial power grid and water electrolysis crack, operators often have no time to shut down, resulting in “flying” phenomenon of hydroelectric generating units. Due to the high frequency and high voltage generated by high-speed operation, or when the circuit breaker fails to turn off, thermostatic element it will cause damage to other electrical equipment in the power grid impacted by generators and their own generators. When the interconnected generator set is equipped with a micro-computer controller, the computer detects the abnormal frequency of the external network at the moment when the [operation mode] turns to the [big grid], i.e. the first time after the switch trips of the substation, if the following conditions are met: frequency (> 50.5 Hz) and voltage (> 456 V); frequency (> 51.0 Hz) and voltage (> 437 V); voltage 52.
0 Hz); frequency ( 45.
6 V). 6V (delay 0.5 seconds); the computer immediately sends out the opening signal: the micro-computer (6, 7) usually opens the point to connect the manual opening button of the original PGL control cabinet ME630 circuit breaker to issue the opening order, at the same time, the micro-computer (1-3) uses the power source of the generating unit to send out the “turn-off” signal to control the motor reversal (KM2) quickly, and adjust the water guide mechanism of the turbine to make the speed equal to the frequency of the power grid (no-load state). 。 Realize the function of crack protection. It improves the reliability and efficiency of the unit operation.
The operation of the hydropower station before and after the technical renovation shows that it has been improved in all aspects. The main manifestations are as follows: before the technical renovation, artificial operation, as far as possible increase the generating capacity, improve the speed of the turbine, resulting in excessive grid voltage, affecting the quality of power supply of the power grid. After the adoption of micro-computer technology reform, the influence of human factors is eliminated, so that the unit can operate in the normal cycle and voltage range, and the quality of power supply of the power grid is ensured.
As a result of manual operation, when the unit fails or the power grid suddenly trips and throws off the load, the operator on duty is too late to operate, which easily leads to the occurrence of motorcycle accidents, resulting in the damage of mechanical and electrical equipment and personnel injury. For example, in August 2012, because of thunderstorm weather, tripping of external network caused by failing to shut down three hydro-generating units in time, the stator windings of Unit 3 (SFW 160) 160KW generator were burned down and the excitation generator was damaged, resulting in a direct economic loss of 205,000 yuan, which mainly affected the power generation efficiency during the peak period (flood season), and its indirect economic loss was 160 Kw*24 h/day*30 days*0.56 yuan/kw.h=645,000 yuan. After the technical reform, the over-speed signal can be automatically sent out immediately after the splitting of the external network. The main switch of the generator is switched off and the governor motor is switched off immediately to control the running of the turbine in the no-load state, which can ensure the safety of the mechanical and electrical equipment and personnel, and the intact rate of the equipment has been greatly improved. Due to the improvement of equipment integrity rate, less downtime and short time to restore power generation, its power generation benefits have been brought into full play. This set of device uses a micro-computer device and the original manual closing, opening and closing as a whole, each of which is converted into standby, and the conversion operation is simple. When using the micro-computer device, the original electrical device is used to cooperate with the micro-computer to achieve the goal of automatic grid connection and decomposition protection. When the micro-computer device fails, it can be converted to manual operation (synchronization lamp) to continue generating electricity by simply switching on the button and turning off the power supply of the micro-computer. The technical transformation of small hydropower station by means of micro-computer can not only ensure the stability of power quality, improve the safety of unit operation and the intact rate of equipment, increase the efficiency of power generation and reduce the operation cost, but also is a technology transformation method with less investment and quick effect.
It can also use the control function of microcomputers to install an automatic water level monitoring device on the forebay to realize the function of automatically adjusting output according to water level, remote control function and so on, laying a good foundation for further technological innovation in the future. Yan Hongyuan, Senior Engineer of Mechanical and Electrical Engineering, Research Direction: Mechanical and Electrical Technology.