Measurement board card used for nuclear power plant steam turbine rotation speed pulse signal conversion

Abstract

The invention belongs to the technical field of nuclear power plant steam turbine rotation speed measurement, and particularly relates to a measurement board card for nuclear power plant steam turbine rotation speed pulse signal conversion. Comprising a power supply circuit, a pulse input circuit, an MCU, a pulse output circuit and an RS485 communication circuit, the power supply circuit is connected with the MCU, the pulse input circuit outputs signals to the MCU, the MCU outputs signals to the pulse output circuit, and the RS485 communication circuit is connected with the MCU. The beneficial effects of the invention are that a single-tooth rotating speed pulse input signal is converted into a multi-tooth rotating speed pulse output signal through the pulse signal conversion board card for converting a 1-tooth pulse into a 116-tooth pulse, so that the problem that a plurality of rotating speed measuring devices at present can only realize monitoring and comparison functions can be solved; and mutual switching between an original rotating speed signal and a standby rotating speed signal cannot be realized.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam turbine speed measurement in nuclear power plants, and particularly relates to a conversion board for steam turbine speed pulse signals in nuclear power plants. Background Art

[0002] The speed of the steam turbine of a nuclear power unit is measured by two different types of speed sensors installed directly above the speed measurement gear in the front casing of the steam turbine. Currently, the layout of the speed signal monitoring point positions is relatively single.

[0003] According to Article 8.1.9 of the "Twenty-five Key Requirements for Preventing Power Production Accidents": Two speed measuring devices should be installed on the shafting of the steam turbine generator set and installed on different rotors respectively. Currently, most semi-speed steam turbines in nuclear power plants are equipped with two speed measuring devices (referred to as the original system, 116 teeth). One is used for the steam turbine protection system (GSE), and the other is used for the steam turbine monitoring system (GME). However, both speed measuring devices are located above the speed measurement gear in the front casing of the steam turbine, which does not meet the requirement of being installed on different rotors in the twenty-five key requirements.

[0004] In view of the current setting situation of the speed monitoring points, if the steam turbine undergoes rubbing during the starting and accelerating process to grid connection or the shutdown and disconnection process due to abnormal changes in the gap between the speed measurement gear and the speed sensor, it will lead to abnormal signals of the speed sensors in the original system or even the situation of losing the steam turbine speed monitoring signals simultaneously, which is extremely likely to cause misjudgment by the control room operator and bring greater human factor challenges. To reduce the risk of human error of the operator and avoid abnormal or loss of speed signals caused by rubbing between the speed measurement gear and the speed probe under abnormal conditions of the steam turbine unit. A new set of steam turbine speed monitoring system (referred to as the standby system, 1 tooth) is added at different positions. Under the normal operating state of the unit, the original system and the standby system conduct real-time monitoring and comparative analysis of the steam turbine speed state. When the speed sensor signal of the original system is abnormal or lost, the sensor signal of the original system is cut off through a manual switching device, and the sensor signal of the standby system is input to ensure that the signal of the original system is not lost and ensure the stable and safe operation of the unit. Summary of the Invention

[0005] The purpose of the present invention is to provide a conversion board for steam turbine speed pulse signals in nuclear power plants, which can ensure the speed measurement accuracy under the condition of limited measuring points, and at the same time match the original system, directly input the converted signal of the standby system for steam turbine protection and monitoring, be applicable to the conversion of single-tooth speed pulse signals of nuclear power plant steam turbines into multi-tooth speed pulse signals, and at the same time realize the mutual switching of the original speed signal and the standby speed signal.

[0006] The technical solution of the present invention is as follows: A measurement board for converting the rotational speed pulse signal of a steam turbine in a nuclear power plant, which includes a power supply circuit, a pulse input circuit, an MCU, a pulse output circuit, and an RS485 communication circuit. The power supply circuit is connected to the MCU, the pulse input circuit outputs a signal to the MCU, the MCU outputs a signal to the pulse output circuit, and the RS485 communication circuit is connected to the MCU.

[0007] The power supply circuit is input via two redundant DC24V power supplies.

[0008] The power supply circuit is buck - stepped down to DC6V through a BUCK.

[0009] The power supply circuit is LDO - stepped down to DC3.3V to supply power to the MCU.

[0010] The pulse input circuit includes an optocoupler. After the input pulse is isolated by the optocoupler, it is connected to the input capture channel of Timer A of the MCU to measure the pulse period and filter out interference pulses smaller than the limit value.

[0011] The MCU calculates the pulse output period according to the configuration data and performs two - channel PWM output through Timer B.

[0012] The pulse output circuit includes an opto - isolator. After opto - isolation, it is connected to the output terminal and configured by the upper - computer software through the RS485 communication interface.

[0013] The beneficial effect of the present invention is that: Through a pulse signal conversion board that converts 1 - tooth pulses to 116 - tooth pulses, the single - tooth rotational speed pulse input signal is converted into a multi - tooth rotational speed pulse output signal, which can solve the problem that currently multiple sets of rotational speed measurement devices can only achieve monitoring and comparison functions and cannot realize the mutual switching between the original rotational speed signal and the standby rotational speed signal (because the number of teeth of the two groups of signals is different). The application scenarios of rotational speed measurement are more, and the installation positions are more flexible. Description of the Drawings

[0014] Figure 1 It is a signal flow schematic diagram;

[0015] Figure 2 It is an input / output signal timing schematic diagram;

[0016] Figure 3 It is a schematic diagram of a measurement board for converting the rotational speed pulse signal of a steam turbine in a nuclear power plant provided by the present invention. Detailed Embodiments

[0017] The present invention will be further described in detail below in conjunction with the drawings and specific embodiments.

[0018] A pulse signal conversion board for the steam turbine of a nuclear power plant, whose main function is to convert an input signal that generates 1 pulse per revolution of the steam turbine rotor into an output signal of 116 pulses per revolution through digital processing. For the convenience of downstream system identification and measurement, the high level of the output pulse signal is designed as +24V, and the low level is designed as 0V or 6V (selected by jumper).

[0019] As Figure 1 and 2 shown, the signal flow is as follows:

[0020] 1. The standby speed probe detects the speed signal 1 and inputs it to the standby system speed measurement card 2 for measurement.

[0021] 2. The standby system speed measurement card 2 outputs a standard pulse to the pulse conversion board 3.

[0022] 3. The pulse conversion board 3 has a built-in microprocessor, and the microprocessor contains a firmware program. The firmware program detects the input pulse and times it. According to the time of each input cycle, dividing by 116, the time period of the output pulse is obtained. Then, through the output drive circuit, a pulse with a high level of +24V and a low level of 0V or 6V (selected by jumper) is output.

[0023] 4. The converted 116-tooth pulse is connected to the manual switch 4 and finally connected to the original system speed measurement card 6.

[0024] The power supply part of the conversion board inputs 24V, first realizes voltage stabilization from 24V to 6V through stepwise voltage regulation to provide power support for the optional output low level, and then realizes voltage stabilization from 6V to 3.3V to provide power support for the logic chip.

[0025] The conversion board uses a STM32F103C8T6 processing chip with a high-performance ARM Cortex-M3 core, a clock frequency of 72Mhz, an internal integrated flash memory space of 64Kbytes, and 3 general-purpose timers, etc. It is powered by 3.3V.

[0026] The signal input part of the conversion board is isolated by an optocoupler. The input port is configured as the input capture function of the general-purpose timer through software to detect the edge change of the input signal. The input pulse captures the count value of the current counter at both the rising edge and the falling edge, and then triggers an internal interrupt. The interrupt service program can calculate the frequency and duty cycle of the input pulse. After a cycle of signal input is satisfied, the duty cycle and frequency of the pulse input signal are also calculated.

[0027] The signal output part of the conversion board is also isolated by optocouplers. At the same time, the low level of the output pulse can be manually configured in hardware by selecting 0V or 6V through a jumper cap. The timer is configured by software to match the flip output function. The timer counts up from 0. When it reaches the preset match value, it flips the level of the output pin and triggers an internal interrupt. The interrupt service program can perform functions such as counting the output pulses. When the half-speed steam turbine of the nuclear power plant is running at a constant speed of 1500 revolutions per minute, the frequency f of the original system speed signal is f = 1500 × 116 / 60 = 2900 Hz. Through theoretical calculation and analysis, the accuracy of the output pulses of the conversion module has an error of 0.25 Hz at a frequency of 3000 Hz, an error of 0.11 Hz at a frequency of 2000 Hz, an error of 0.027 Hz at a frequency of 1000 Hz, an error of 0.007 Hz at a frequency of 500 Hz, and an error of 0.0003 Hz at a frequency of 100 Hz.

[0028] The configuration parameters of the conversion board are stored in an independent partition space of the internal flash memory. During operation, the stored parameters will be read. If parameter changes are required, the parameters can be rewritten and refreshed through the configuration software. When the board is running, it first detects the rising edge and falling edge within one cycle of the input signal, calculates the frequency, then calculates the output signal frequency, and then sets the count match value of the output timer to output a signal with a specific frequency. At the same time, the communication port continuously monitors the configuration messages to ensure the timeliness of parameter changes.

[0029] As Figure 3 shown, a measurement board for converting the rotational speed pulse signal of a steam turbine in a nuclear power plant includes a power supply circuit, a pulse input circuit, and an MCU (Micro Controller Unit: abbreviated as MCU, which is an integrated circuit chip integrating a central processing unit CPU, memories (ROM, RAM), and various peripheral interfaces (such as input / output pins, timers, serial ports, etc.)). Through very large scale integration technology, it integrates a central processing unit with data processing capabilities, a random access memory, a read-only memory, multiple I / O ports, an interrupt system, a timer / counter, etc. onto a silicon chip to form a small and complete microcomputer system. A pulse output circuit and an RS485 communication circuit. The power supply circuit is input via two redundant DC24V power supplies, bucked down to DC6V through a BUCK converter, and then bucked down to DC3.3V through an LDO. The power supply circuit is connected to the MCU and supplies power to it. The pulse input circuit outputs a signal to the MCU, the MCU outputs a signal to the pulse output circuit, and the RS485 communication circuit is connected to the MCU.

[0030] The pulse input circuit includes an optocoupler and a current-limiting resistor. After the input pulse is isolated by the optocoupler, it is connected to the input capture channel of Timer A of the MCU (the capture channel is a functional module of the internal integrated timer of the MCU, which is used to measure the time of the pulse signal), measure the pulse period, and filter out interference pulses smaller than the limit value. The MCU calculates the pulse output period according to the configuration data (the configuration parameters are stored in an independent partition space in the internal flash memory of the MCU), and then outputs two-way PWM through Timer B to the pulse output circuit; the pulse output circuit includes an optocoupler and a current-limiting resistor group, and the output pulse is connected to the output terminal after optical isolation. The output terminal is the terminal block, which is used for the output of the processed pulse signal.

[0031] The RS485 communication circuit includes an RS485 transceiver and a TVS protection diode. After being connected to the computer through the RS485 communication interface, it can be configured by the host computer software installed in the computer, that is, the running parameters related to communication are set and adjusted (configuration means the setting or adjustment of running parameters).

[0032] Embodiment 1:

[0033] This pulse signal conversion board is used for the steam turbine speed measurement system under research and development. The newly added 8 sets of speed signals respectively send 8 one-pulse-per-revolution signals to the pulse signal conversion module through the speed measurement card. The pulse signal conversion board converts the one-pulse-per-revolution signal into a 116-pulse-per-revolution signal and sends the 116-pulse-per-revolution signal out in two paths simultaneously. One path is sent to the second channel of the corresponding speed measurement card, and then it can be communicated to the display screen for data comparison and storage; the other path is sent to the redundant speed switching device.

[0034] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it; although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that: if they modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features, it does not make the essence of the corresponding technical solutions deviate from the scope of the technical solutions of the embodiments of the present invention.

Claims

1. A measurement board for converting speed pulse signals of steam turbines in nuclear power plants, characterized in that: It includes a power supply circuit, a pulse input circuit, an MCU, a pulse output circuit and an RS485 communication circuit. The power supply circuit is connected to the MCU, the pulse input circuit outputs signals to the MCU, the MCU outputs signals to the pulse output circuit, and the RS485 communication circuit is connected to the MCU.

2. A measurement board for converting speed pulse signals of steam turbines in nuclear power plants as claimed in claim 1, characterized in that: The power supply circuit is input via two redundant DC24V power supplies.

3. A measurement board for converting speed pulse signals of steam turbines in nuclear power plants as claimed in claim 2, characterized in that: The power supply circuit is stepped down to DC6V by BUCK.

4. A measurement board for converting speed pulse signals of steam turbines in nuclear power plants as claimed in claim 3, characterized in that: The power supply circuit is stepped down to DC3.3V through LDO and supplies power to the MCU.

5. A measurement board for converting speed pulse signals of steam turbines in nuclear power plants as claimed in claim 1, characterized in that: The pulse input circuit includes a photoelectric coupler. After the input pulse is isolated by the photoelectric coupler, it is connected to the timer A input capture channel of the MCU to measure the pulse period and filter the interference pulses less than the limit value.

6. A measurement board for converting speed pulse signals of steam turbines in nuclear power plants as claimed in claim 1, characterized in that: The MCU calculates the pulse output period according to the configuration data and performs two-way PWM output through timer B.

7. A measurement board for converting speed pulse signals of steam turbines in nuclear power plants as claimed in claim 1, characterized in that: The pulse output circuit comprises a photoelectric isolator, which is connected to the output terminal after photoelectric isolation and configured by the host computer software through the RS485 communication interface.

Images