KR102030933B1 - System and method for remote monitoring/controlling of generator - Google Patents

Abstract

The present invention relates to a system for remotely monitoring and controlling a generator and a method therefor. The system comprises: a generator; a Raspberry Pi which communicates with a control panel installed in the generator to read status information of the generator and transmits the status information of the generator read through wireless communications to a mobile terminal through a wireless communication network; and the mobile terminal which transmits a drive control signal of the generator based on a state of the generator transmitted by the Raspberry Pi. The Raspberry Pi receives the drive control signal of the generator from the mobile terminal and transmits the same to the control panel. By this configuration, the system can monitor and control a preliminary inspection and a trial run by using the mobile terminal such as a smartphone at a remote place without being limited to time and space to maintain the generator to be in the optimum state, thereby increasing the reliability and accuracy of the generator.

Description

Generator remote monitoring and control system and its method {SYSTEM AND METHOD FOR REMOTE MONITORING / CONTROLLING OF GENERATOR}

The present invention relates to a generator remote monitoring and control system and method, and more particularly, to a generator remote monitoring and control system and method for monitoring and controlling the condition of the generator in advance.

Emergency diesel generators are used to supply commercial power when commercial power suddenly powers down due to natural disasters or poor external environment.It operates the emergency generator within 10 seconds when the commercial power supplied by KEPCO is cut off. Supply must continue.

For this purpose, the emergency generator should monitor the power generation voltage, power generation frequency, power generation capacity, etc., by the administrator from time to time where the monitor of the power generator is directly installed.

In addition, it is important to check and commission the state of the emergency generator at all times and to maintain the generator to operate normally in the event of an emergency.

For this purpose, even if the power is normally supplied, the emergency generator should be directly commissioned twice a month or once a week for 10 minutes to check whether the generator can operate normally.

When commissioning an emergency generator, the noise is extremely loud, and repeated exposure to strong noise by the manager is likely to damage hearing.

Therefore, a technique for remotely monitoring and controlling the emergency generator is required. Currently, some of the offshore diesel generators are capable of remote monitoring but do not include the ability to directly control the generator remotely. In addition, a diesel generator capable of both remote monitoring and control has not been developed in Korea.

The present invention has been proposed to solve the above conventional problems, the generator can monitor the state of the generator with a remote mobile terminal to maintain the state of the generator in an optimal state, the generator capable of driving an emergency generator remotely It is to provide a remote monitoring and control system.

The configuration according to the first aspect of the present invention for solving the above problems, in the generator remote monitoring and control system, by communicating with the generator and the control panel installed on the generator to read the status information of the generator to wireless communication Raspberry Pi for transmitting the read status information of the generator through a wireless communication network, a mobile terminal for receiving the status information of the generator transmitted by the Raspberry Pi, and transmits the drive control signal of the generator based on the generator status information The raspberry pi receives a generator driving control signal from the mobile terminal and transfers the control signal to a programmable logic controller (PLC) of the control panel. The communication between the raspberry pi and the PLC of the control panel of the generator is performed by a MODBUS communication method. Performs RS-485 communication, and communication between the mobile terminal and the Raspberry Pi Performs socket communication, for the socket communication, the mobile terminal is provided with a TCP client function, an application for generator status monitoring and generator control is installed, the raspberry pi is installed a generator control program to function as a TCP server, Application of the mobile terminal is a generator registration function for the generator registration by inputting the generator identification information and IP address and port number of the Raspberry Pi in the generator for generator monitoring and control, generator control item selection and control value setting function, A generator monitoring function for checking a generator status is performed, and the mobile terminal wirelessly transmits a generator status monitoring request signal or the generator control signal set by the application to the Raspberry Pi.

Here, the drive control signal of the generator preferably includes a generator on / off, generator breaker reset, generator breaker on / off, generator reset signal.

The application of the mobile terminal, for controlling the generator remotely, 'generator registration button', 'generator ON' button, 'generator OFF' button, 'breaker ON' button, 'breaker OFF' button, for generator reset ' It is preferable to display the generator control item screen having a 'reset' button and a 'check warning' button indicating that the sensor value of the generator is out of the normal range.

Herein, the MODBUS communication protocol conforms to the architecture, and the Raspberry Pi becomes a master of the control panel PLC and the control panel PLC becomes a master of various sensors, motors or embedded devices of the generator.

When the Raspberry Pi receives the generator status monitoring request signal from the mobile terminal, the raspberry pi reads various sensor values from the control panel of the generator and transmits the sensor values to the mobile terminal, and receives the generator control signal and transmits it to the control panel of the generator. It is desirable to.

According to a second aspect of the present invention for solving the above problems, there is provided an emergency generator remote monitoring comprising a generator and a control panel for controlling the generator, and a raspberry pi communicating with the control panel and a remote mobile terminal; A control method comprising: transmitting, by the mobile terminal, the generator status monitoring request signal; Requesting, by the Raspberry Pi, status information of the generator to a PLC of the control panel through RS-485 communication using a MODBUS communication method; Transmitting, by the PLC of the control panel, the state information of the generator to the Raspberry Pi through RS-485 communication using a MODBUS communication method; The raspberry pi wirelessly transmitting status information of the generator to a mobile terminal; And transmitting, by the mobile terminal, a driving control signal including a generator control item selection and a control value setting based on the state of the generator received from the Raspberry Pi, and the communication between the mobile terminal and the Raspberry Pi is socket communication. To perform the socket communication, the mobile terminal functions as a TCP client, an application for generator status monitoring and generator control is installed, and the raspberry pi is installed with a generator control program functioning as a TCP server. .

The MODBUS communication protocol follows a master-slave architecture, preferably the Raspberry Pi becomes the master of the control panel PLC and the control panel PLC becomes the master of the various sensors, motors or embedded devices of the generator.

Here, the application of the mobile terminal, in order to remotely control the generator, generator registration button, generator ON button, generator OFF button, circuit breaker ON button, circuit breaker OFF button, generator reset It is preferable to display the generator control item screen having a 'reset' button and a 'warning check' button indicating that the sensor value of the generator is out of the normal range.

With this configuration, the preliminary inspection and commissioning can be monitored and controlled by using a smartphone at a remote location without being limited to time and space, and accordingly, the diesel generator reliability is maintained by maintaining the optimum state of the diesel emergency generator. And accuracy can be increased.

In addition, by using the wireless Internet to command the commissioning of the emergency generator remotely from the smart phone and can check the status, it is possible to significantly reduce the administrative costs as well as the health and safety of the administrator.

1 is a block diagram of a generator remote monitoring and control system according to the present invention,
2 is a block diagram showing a communication method between the components of the generator remote monitoring and control system of FIG.
3 is a master-slave relationship in communication between the raspberry pi and the generator control panel and the generator of FIG.
4 is a configuration diagram of a transmission message of a Modbus RTU protocol;
5 is a flow chart of a generator remote monitoring and control method according to the present invention,
6 is an emergency generator registration and deletion screen in the service app for remote monitoring / control of the generator of the smartphone of Figure 1,
7 is a state display screen of the emergency generator in the service app for remote monitoring control of the generator of the smartphone of FIG.

Advantages and features of the present invention, and methods of achieving the same will be described through embodiments described below in detail with the accompanying drawings. However, the present invention is not limited to the embodiments described herein and may be embodied in other forms. However, the embodiments are provided to explain in detail enough to easily implement the technical idea of the present invention to those skilled in the art.

In the drawings, embodiments of the invention are not limited to the specific forms shown, and are exaggerated for clarity. In addition, parts denoted by the same reference numerals throughout the specification represent the same components. The expression "and / or" is used herein to mean including at least one of the components listed before and after. In addition, the singular also includes the plural unless specifically stated otherwise in the text. Also, as used herein, components, steps, operations, and elements referred to as "comprising" or "comprising" refer to the presence or addition of one or more other components, steps, operations, elements, and devices.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. In the following description of the present invention, if it is determined that the detailed description of the related known function or configuration may unnecessarily obscure the subject matter of the present invention, the detailed description thereof will be omitted.

The remote monitoring and control system of the generator according to the present invention is a mobile terminal (in the present invention, the mobile terminal is a term that includes all the portable terminals, such as smartphones, tablet PCs) to grasp the current state of the generator from time to time To command the operation of the generator in an emergency.

In the present invention, by installing a Rasberry Pi having a wireless communication function such as Wi-Fi in the generator, the Raspberry Pi and a remote smart phone (mobile terminal) to enable wireless communication, the generator can be monitored and controlled remotely Design and implement systems that can

For this purpose, Raspberry Pi is installed on the control panel of the diesel generator, and Raspberry Pi communicates with PLC (Programmable Logic Controller) installed on the control panel using RS-485 of MODBUS communication method. The PLC is used for automatic control and monitoring of the generator, and the control panel is connected to various sensors, motors or other embedded devices of the diesel generator.

According to the present invention, the remote monitoring function of the generator by the smartphone includes a function that can represent all of the error of the generator by type. And, the remote control function of the generator by the smartphone may include all the existing control functions, including the on and off of the generator, the addition of power and cut off.

1 is a block diagram of a generator remote monitoring and control system according to the present invention, Figure 2 is a block diagram showing a communication method between each component of the generator remote monitoring and control system of FIG. FIG. 3 is a master-slave relationship diagram when the Raspberry Pi and the generator control panel of FIG. 1 communicate with each other.

As shown in FIG. 1, the generator remote monitoring and control system 1 is a mobile terminal for monitoring and controlling the state of the emergency generator by wirelessly communicating with the emergency generator 10 and the emergency generator 10 (hereinafter 'smartphone'). 30). In the present invention, the generator includes a general generator, an emergency generator, and in the embodiment, is called an emergency generator.

The emergency generator 10 includes a diesel engine 11, a control panel 12 for controlling the diesel engine 11, and a raspberry pi 13 for communication with the smartphone 30.

The emergency generator 10 is provided with various sensors (not shown) for detecting the state of the diesel engine 11.
As shown in FIG. 2, the control panel 12 is provided with a PLC 121 that functions as a control, various kinds of emergency generator sensors 15, and an emergency generator driver 16.

Raspberry Pi 13 is a mini PC based on an embedded board (Embedded Board) is capable of wired communication and wireless communication (Wi-Fi).

According to the present invention, between the Raspberry Pi 13 and the smart phone 30 to send and receive messages using the Wi-Fi wireless communication. Programming languages for sending and receiving messages are Python and Android Studio.

The generator state values read out from the PLC 121 at the request of the Raspberry Pi are voltage (r-s), voltage (s-t), voltage (t-r), current (r), current (s), Current (t), Power (KWatt) * 10, Power Factor * 10, Apparent Power (KVA) * 10, Frequency (Hz) * 10, Integrated Power High, Integrated Power Low * 10, Battery Voltage * 10, Lubricant pressure * 10, coolant temperature.

The control data of the emergency generator 10 may include generator operation, generator stop, breaker input, breaker shutdown, buzzer stop, reset, generator auto selection, generator manual selection, breaker automatic selection, breaker manual selection.

As shown in FIG. 2, the communication between the smartphone 30 and the Raspberry Pi 13 in the present embodiment uses socket communication, and the PLC of the control panel 12 of the Raspberry Pi 13 and the emergency generator 10 is used. The communication between the 121 uses MODBUS communication using RS-485. Communication using RS-485 is the most commonly used serial communication with RS-232 communication.

Socket communication plays a role of continuously connecting the app of the smart phone 30 as a TCP client and the program in the Raspberry Pi as a TCP (Transmission Control Protocol) server until the administrator finishes remote monitoring or control.
MODBUS communication has the advantages of high speed, wide communication range, point to point mode, and network creation (multidrop) of multiple devices.It has been known for a long time. It is widely adopted and used in many measurement control devices.

In this embodiment, the smartphone app installed in the smartphone 30 becomes a TCP client and the generator control program installed in the Raspberry Pi 13 becomes a TCP server.

In addition, in the present embodiment, the smart phone 30 remotely monitors and controls the emergency generator 10 as follows. When the TCP client of the app of the smart phone 30 wirelessly transmits the control signal of the emergency generator 10, the TCP server driven from the Raspberry Pi 13 installed in the remote emergency generator after receiving the control signal and the control signal Is transmitted to the PLC 121 of the emergency generator, and the PLC 121 controls the diesel engine 11 according to the control signal.

Meanwhile, a message exchanged between a TCP client and a TCP server is composed of a MODBUS frame, and there are two types of MODBUS frames, a protocol data unit (PDU) and an application data unit (ADU). The PDU frame contains data after a function code. The function code represents the task to perform and the data represents the information to use for this task. ADU frames provide error checking for additional address parts.

The MODBUS communication protocol, on the other hand, has a master-slave structure. The master sends a request to the slave and waits for a response. As shown in FIG. 3, the Raspberry Pi 13 may be a master of the PLC 121, and the PLC 121 may be a master of sensors, motors or other embedded devices of the emergency generator 10.

When the Raspberry Pi 13 sends 'Request' to the PLC 121 to request various status values of the emergency generator, the PLC 121 sends the 'Request' to the diesel generator 11 and the diesel generator sends various status values. It reads and sends a 'Response' to the PLC 121, the PLC 121 sends a 'Response' to the Raspberry Pi (13).

Hereinafter, the configuration of the transmission message in the Modbus RTU protocol will be described.

The frame format of the transmission message is configured as shown in FIG. 4 (a) below, and the query message and the response message are in the same format, but the data part is changed according to the function code.

As shown in Fig. 4 (b), the slave address block indicates an address of a slave (communication device) to receive an inquiry message and to send a response message, and data having a value in the range of 0 to 255 is stored. Is sent.

A data block is a group of multiple 8bits as data values whose contents and length vary depending on the function code of the message. Data with a 16-bit value is sent first to the parent.

Function code block is a code that indicates the function of the message to be transmitted. It is expressed in the range of 1 ~ 255. The role of each function code is shown in Table 1. In the present embodiment, the function code 04 and the function code 05 are used among the function codes of the "function code of the Modbus RTU protocol" in Table 1 below.

Function code function Reference address range Remarks 01 Read Coil Status 0x 00001-09999 unused 04 Read Input Register 3x 30001-39999 use 05 Force Single Coil 0x 00001-09999 use 15 Force Multiple Coils 0x 00001-09999 unused 16 Preset Multiple Registers 4x 40001-49999 unused

Function code 04 is “Input Registers”. That is, function code 04 is used to read the analog register value of each slave or read the digital register in units of 16 bits.

Function Code 04-① Question (PC (Master) ---> Device (Slave)) Slave Address Function code data Crc code 0A 04 00 00 00 02 Calculated Value

The upper two bytes of data are the register start address 30001, and the lower two bytes are the number (word unit).

 Function Code 04-② Response (PC (Master) <--- Instrument (Slave)) Slave Address Function code data Crc code 0A 04 04 02 2B 00 64 Calculated Value

The first of the data means the number of data to be read (byte unit), followed by the upper and lower parts of the first data and the upper and lower parts of the second data.

Function code 05 is "Single Coil". Command to reinforce the single coil installed in the generator.

Function code 05-① Question (PC (Master) ---> Device (Slave)) Slave Address Function code data Crc code 0A 05 00 00 FF 00 Calculated Value

The upper 2 bytes of data means register start address (00001), the lower 2 bytes means "on" if it is "FF 00" and "" if it is "00 00".

Function code 05-② Response (PC (master) <--- Machine (slave)) Slave Address Function code data Crc code 0A 05 00 00 FF 00 Calculated Value

A normal response echoes the query as above.

On the other hand, the CRC code block is an error detection code and is for reception error detection. The CRC code is composed of 16 bits (2 bytes). The CRC code is added to the end of the transmission message to determine whether there is a reception error by comparing with the calculated value each time the receiving side receives the received data one byte.

5 is a flow chart of a generator remote monitoring / control method of the smart phone according to the present invention. As shown in FIG. 5, the raspberry pi 13 installed in the generator receives the monitoring request signal of the emergency generator from the smartphone 30 (S1). After the Raspberry Pi 13 of the generator 10 requests generator status information to the control panel 12 through RS-485 communication using MODBUS communication, status information of the emergency generator through RS-485 communication from the control panel 12. Received (S2). The raspberry pi 13 of the generator 1 wirelessly transmits the state information of the emergency generator to the smartphone 30 (S3).

The smartphone 30 displays the state of the emergency generator 10 through the app (S4). The user of the smartphone 10 determines whether to control the emergency generator (S5), and if the determination result requires the control of the emergency generator, the user of the smartphone 30 in the generator control app, the control items of the emergency generator 10 After selecting and setting the control value, the smartphone 30 wirelessly transmits the control signal (S6).

The raspberry pi 13 of the emergency generator 10 wirelessly receives the control signal and transmits it to the control panel 12 (S7). The control panel 12 controls the diesel engine 11 in accordance with the control signal (S8).

6 is an emergency generator app screen 60 in the service app for the generator remote monitoring / control of the smartphone of Figure 1, Figure 7 is a state of the emergency generator in the service app for remote monitoring control of the smartphone of Figure 1 It is a display screen.

Downloading the app to perform emergency generator remote monitoring and control in the smart phone 30, and displays the emergency generator app screen 60 that can register, delete, modify the diesel generator. Pressing the "Generator Registration" button (60a) in Figure 6 (a) is shown a generator registration screen 61 that can register the generator as shown in Figure 6 (b). In the generator registration screen 61 of FIG. 6 (b), when the generator name (identification information) and the smartphone app which is a TCP client enter the IP address and port number of the Raspberry Pi which is a TCP server to communicate with, The generator registration completion screen 62 as shown in Fig. 6C is displayed.

And, if you press the 'Motor generator modification' button in the emergency generator app screen 60 of Figure 6 (a) as shown in Figure 6 (d) modification screen to modify the name (identification information) and IP address, and port number of the generator (63) appears.

Meanwhile, when the generator icon 62a registered in FIG. 6 (c) is selected, the registered generator icon 71 a is activated as in the generator selection screen 71 of FIG. 7 (a). When the generator icon 71a registered in the generator selection screen 71 of FIG. 7 (a) is long clicked for 2 to 3 seconds, the generator status confirmation screen 72 for requesting safety confirmation is displayed as shown in FIG. 7 (b). If you click on the block ① and the block ② that asks the generator drive setting in order to display the safety confirmation message, the generator control item screen 73 as shown in FIG. 7 (c) to monitor and control the generator appears.

In the generator control item screen 73 of FIG. 7C, the generator ON button 73a, the generator OFF button, the circuit breaker ON button 73b, the circuit breaker OFF button, the reset button, Alert confirmation button is provided. In the generator control item screen 73 of FIG. 7C, when the 'generator ON' button 73a is selected by pressing, the emergency diesel generator is operated. And, by pressing the 'generator OFF' button 73b in Figure 7 (c), the emergency generator off signal is transmitted through the wireless communication network in the smart phone 30, the raspberry pi 13 in the emergency generator 10 Transmits a signal to the PLC 12 to stop the operation of the emergency generator, and the PLC 12 stops the diesel engine 17.

The raspberry pi 13 of the emergency generator 10 communicates with the PLC 12 and receives various sensor values of the generator at intervals of about 5 seconds, for example, and transmits them to the smartphone 30, and the smartphone 30. Is displayed at the bottom of the screen for monitoring the various sensor values of the emergency generator 10 based on the generator status information transmitted from the Raspberry Pi 13, and if the sensor value of the generator displays a value out of the normal range 'warning' The background of the OK 'button 73d turns red.

At this time, if you press the 'check warning' button, you can check the problem occurred. After the problem is solved, clicking the 'RESET' button 73e in FIG. 7C returns the background color of the 'OK' button 73d to its original color and confirms the warning in FIG. 7D. Each item on the screen will also change to a “no problem” with a green background.

As described above, the Raspberry Pi 13 is installed in the diesel generator 10, and the communication between the Raspberry Pi 13 and the PLC inside the generator control panel 12 uses a MODBUS communication method using RS-485. And, by allowing the Wi-Fi communication between the Raspberry Pi 13 and the remote smart phone 30, it is possible to remotely monitor and control the state of the diesel generator.

Preliminary checks and commissioning can be monitored remotely using a smartphone, regardless of time and space. In addition, it is possible to increase the reliability and accuracy of the diesel generator by maintaining the optimum state of the diesel emergency generator.

In addition, if you can command the commissioning and check the condition of the emergency generator remotely from your smartphone using the wireless Internet, it can not only reduce the management cost, but also greatly help the health and safety of the manager.

1: generator remote monitoring / control system
11: diesel generator 12: control panel
13: Raspberry Pi 15: generator various sensors
16: emergency generator drive unit 17: diesel engine
20: wireless communication network 30: smart phone
40: Modbus frame structure
42: Modbus RTU protocol transmission message configuration
60: generator app initial screen 61: generator registration screen
62: generator registration completion screen 62: generator information modification screen
71: Generator Selection Screen 72: Generator Status Check Screen
73: Generator Control Item Screen 74: Generator Warning Check Screen

Claims (8)

With generator,
Raspberry Pi, which communicates with the control panel installed in the generator, reads the status information of the generator and transmits the status information of the generator read by wireless communication through a wireless communication network;
And a mobile terminal for receiving the state information of the generator transmitted by the Raspberry Pi, and transmitting a drive control signal of the generator based on the state information of the generator, wherein the Raspberry Pi is a generator drive control from the mobile terminal. Receives a signal and transmits it to a PLC (Programmable Logic Controller) of the control panel, and the communication between the Raspberry Pi and the PLC of the control panel performs a MODBUS communication RS-485 communication, between the mobile terminal and the Raspberry Pi Communication performs socket communication, and for the socket communication, an application for TCP client function and generator status monitoring and generator control is installed in the mobile terminal, and a generator control program for TCP server function is installed in the Raspberry Pi. ,
Application of the mobile terminal is a generator registration function for the generator registration by inputting the generator identification information and IP address and port number of the Raspberry Pi in the generator for generator monitoring and control, generator control item selection and control value setting function Generator monitoring function to check generator status,
And the mobile terminal wirelessly transmits a generator status monitoring request signal or a generator control signal set by the application to the Raspberry Pi. The method of claim 1,
The drive control signal of the generator, generator on / off, generator breaker reset, generator breaker on / off, generator reset signal, generator remote monitoring and control system. The method of claim 1,
The application of the mobile terminal, for controlling the generator remotely, 'generator registration button', 'generator ON' button, 'generator OFF' button, 'breaker ON' button, 'breaker OFF' button, for generator reset ' A generator remote monitoring and control system, wherein the generator control item screen is displayed with a 'reset' button and a 'confirm warning' button indicating that the sensor value of the generator is outside the normal range. The method according to any one of claims 1 to 3,
The MODBUS communication protocol follows a master-slave architecture, wherein the Raspberry Pi becomes the master of the PLC of the control panel, and the PLC of the control panel becomes the master of various sensors, motors or embedded devices of the generator. Phosphorus, generator remote monitoring and control system. The method of claim 4, wherein
When the Raspberry Pi receives the generator status monitoring request signal from the mobile terminal, the raspberry pi reads various sensor values from the control panel of the generator and transmits the sensor values to the mobile terminal, and receives the generator control signal and transmits it to the control panel of the generator. Generator remote monitoring and control system. In the emergency generator remote monitoring and control method comprising a generator and a control panel for controlling the generator, and a raspberry pi in communication with the control panel and a remote mobile terminal,
Registering, by the application of the mobile terminal, the generator with the generator identification information and the IP address and port number of the Raspberry Pi in the generator for monitoring and control of the generator;
Transmitting, by the mobile terminal, a status monitoring request signal of the generator;
Requesting, by the Raspberry Pi, status information of the generator to a PLC of the control panel through RS-485 communication using a MODBUS communication method;
Transmitting, by the PLC of the control panel, the state information of the generator to the Raspberry Pi through RS-485 communication using a MODBUS communication method;
The raspberry pi wirelessly transmitting status information of the generator to a mobile terminal;
Transmitting, by the mobile terminal, a drive control signal including generator control item selection and control value setting based on the state of the generator received from the Raspberry Pi,
Communication between the mobile terminal and the Raspberry Pi performs socket communication, for the socket communication, the mobile terminal functions as a TCP client, and an application for generator status monitoring and generator control is installed, and the Raspberry Pi has a TCP server function. Generator remote monitoring and control method characterized in that the generator control program is installed. The method of claim 6,
The MODBUS communication protocol follows a master-slave architecture, wherein the Raspberry Pi becomes the master of the PLC of the control panel, and the PLC of the control panel becomes the master of various sensors, motors or embedded devices of the generator. Phosphorus, generator remote monitoring and control method. The method of claim 6,
The application of the mobile terminal, for controlling the generator remotely, 'generator registration button', 'generator ON' button, 'generator OFF' button, 'breaker ON' button, 'breaker OFF' button, for generator reset ' And a generator control item screen having a 'reset' button and a 'confirm warning' button indicating that the sensor value of the generator is out of the normal range.

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