Proceedings of the 8th
World Congress on Intelligent Control and Automation
July 6-9 2010, Jinan, China
Xinjian Xiang Ming Li School of Automation and Electrical Engineering College of Metrological Technology & Engineering Zhejiang University of Science and Technology China JILIANG University Hangzhou, Zhejiang Province, P. R. China 310023 Hangzhou, Zhejiang Province, P. R. China 310018 hzxxj@sina.com gundam.li@gmail.com
Abstract - This paper introduces an electrical fire control management software, the monitoring equipment can achieve
system which is composed of stand-alone electrical fire detector its wide-range parameter modification, control and focus on and electrical fire monitoring equipment. The detector with the monitoring. The entire electrical fire control system block
fieldbus communication technologies uses MCU to realize the diagram shown in Fig.1. main route leakage protection for low-voltage 3-phase 4-wire
According to the detector design requirements [1], the system; at the same time, finish the measure, display and control
detector has the basic sound and light leakage detection alarm, of voltage, current, power, electricity, temperature and other
self-check with a variety of functional indicator, LCD screen parameters; through the monitoring equipments have been
installed the management software written by VC++, the and numeric keypad for customers’ data manipulation, set-up
operation of the scene can be monitored and the alarm functions and upload data in the detect filed. Detector also information can be detected in time. With RS-485 or Ethernet provides 20 I/O interfaces for the remote monitoring and
communication, the system can be associated with kinds of control, temperature sensing, circuit breakers, other sound and
standard power monitoring software, circular monitoring and light alarm input, fire Linkage, the state of switch, etc.
control more than 250 detects, and record 100 types of faults and System has other functions like integrates temperature, data with more than 12 months storage time.
overcurrent, overvoltage, under-voltage, phase protection and
energy metering, the fault can be saved in both detector and
Index Terms - MSP430; electric fire; stand-alone; leakage monitoring equipment. Stand-alone detector can record 100
protection. types of faults and data with more than 12 months storage time. Customer can check the faults easy and quick. I. INTRODUCTION
In recent years, there are lots of fires caused by electrical
problems in various types of construction and other fields.
Due to the distribution, sustainability and concealment of electrical fire, it is hard to be noticed at the early stages of fire
and observed by people, resulted in huge losses. Electrical fire
control system is mainly for monitoring, early warning，
promptly remove fire hazards when the leakage current fault
occurs, eliminated the fire hazards at the first stage. Compared
with the traditional fire alarm systems, electrical fire control system is essentially based on prevention, specifically for electrical wiring failures and leakage faults early warning
system. With the application of electrical fire monitoring
online detect technology, we could detect and eliminate most
types of electrical fire hazards, protect national and people's
lives and property.
Fig. 1 Diagram of electrical fire control system FIRE CONTROL SYSTEM COMPONENTS II. ELECTRICAL
III. THE HARDWARE DESIGN OF STAND-ALONE ELECTRICAL Electrical fire control system is mainly consists of the
FIRE DETECTOR electrical fire detectors, fire monitoring equipment and other
alarm signals input, using three-phase four-wire circuit. The Stand-alone electrical fire detector is made up of the
monitoring equipment can control at least 250 stand-alone light/sound alarm, LCD display, numeric keypad, electrical detectors through the line converter, and general computer’s parameters collector, sensor signal, an external data memory, hardware can treat as the monitoring equipment due to the clock / calendar generator and other parts. Taking TI’s 16-bit
design of stand-alone detector decrease the monitoring Ultra-Low-Power microprocessor MSP430F149 [2] as main equipment hardware requirements. Each detector can receive control unit, it has 5 low-power mode can make sure the other alarm signal input such like smoke, temperature and fire detector work with battery for years, and the inside hardware linkage. After installing the related self-write monitoring and
4152
978-1-4244-6712-9/10/$26.00 ©2010 IEEE
The Design of Alarm and Control System for Electric Fire Prevention Based on MSP430F149
multiplier speed up the data processing time so it can do part of DSP operation, this microprocessor have an integrated 12-bit AD converter and temperature sensor, suitable for Indus-trial-grade operating environment better. By the electromagnettic sensing technology, detector collects a variety of electrical parameters in the field, through comparison and integration operations, precise display, analysis, and judge site characteristics, and modified alarm conditions depending on the detail electrical environment. LCD displays the electrical data timely and send to the monitoring equipment by UART [3] or TCP/IP [4] agreement. The hardware design diagram shown in Fig. 2.
Data memory (EEPROM) and real-time clock chip with a separate power supply system, which would ensure the system set parameter, key data and fault records’ safety in any condition. The external FLASH microcontroller using I2C bus to connect MCU for an efficient and stable data transmission; electrical parameters measurement first use high-precision current transformers and precision resistors for signal conditioning, then specialized high-precision measurement chip ATT7028 [5] deal with the input parameters, this chip provides SPI interface to connect MCU with rapid communication speed, reducing MCU’s burden and power consumption; The numeric keypad and LCD allows the operator not only through the monitoring equipment finish the different operation as system set, check the state and fault records, but also in the field easily and rapidly. Operator can change the set and upload the data to monitoring equipment depend on the field’s electrical environment, which make the system with real-time, simple and convenient features; and detector has an independent self-check alarm functions.
process channel anti-interference, printed circuit boards design and anti-interference software design. Power supply with the AC-DC converter to provide a stable voltage; Input signal with optocoupler technology, and the power supply is isolated from the main power supply; MSP430’s watchdog and extern a hardware watchdog chip ensure the system operation.
Leakage current as the main electrical parameter need to be collected, samples measured by zero-sequence current transformer (ZCT) that basic principles [6] is based on Kirchhoff's current law: The algebraic sum of all currents entering and exiting a node must equal zero. The measurement method is different from the ordinary current transformer (CT), allows three-phase wires together through the ZCT or install the ZCT through the neutral line N to detect three phase current vector sum. As shown in Fig. 3’s left part, take the part of through the ZCT as its primary winding, and right part as its secondary winding. Under normal circumstances, the phase current vector sum equal to zero, that is, Ia + Ib + Ic = 0, therefore, the zero sequence current transformer secondary winding has no signal output, when there is a failure the phase current vector sum become non-zero: Ia + Ib + Ic = I (leakage current), fault current across ZCT core produced a circular magnetic flux, zero-sequence current transformer’s secondary winding generate induced voltage, sampled through amplifier circuit and AD converter to MCU, then follow the related procedures.
Fig. 3 Schematic diagram of zero-sequence current transformer
IV. SOFTWARE DESIGN
A. Electrical fire detector software design
Software flow chart as shown in Fig.4, when the program starts after initialization, detectors finish self-check and scan interfaces, if there is a fault, the alarm signal will send to MCU, and wait next step. Self-check only to its detector, after cutting the fault detector’s power and finish repairing, operators recover the power supply to see if there are any problems. Detector passes the self-check and read the pre-existing data from 24CL04, then triggers Timer A which has set the display and fault alarm time and Timer B which has set the sample time. In the main cycle, system receives the keypad input or communication command to finish related operation. LCD main display cycle included three-phase voltage and current display, power display, energy, the leakage current and temperature display, switch state display and clock display. Consumer can choice other setting displays by using the numeric keypad.
Fig. 2 Electrical fire detector hardware design
Due to lots of interference factors in the field, the problem of anti-jamming should be considered in the system hardware and software design. Anti-jamming design includes power anti-jamming design, microcontroller interference, the
4153
an error between actual cycle and measurement cycle, which called cycle change error. Cycle rounding error and cycle change error together constitute the synchronization error, which is the main source affect the measurement accuracy, and we should improve algorithms to reduce the synchronization error [8].
Cycle rounding error compensation (sampling counting N)
Set the timer count cycle τ, then the corresponding timer count with Ts values for Ts / τ. It generally is not an integer, it truncated decimal rounding, may get integer I, truncated the fractional part as L :
I=int(Ts/τ). (3)
L=(Ts/τ)−int(Ts/τ). (4)
The establishment of accumulation units: i’th sample value of Li
if Li <0.5, then the count value N = I ;
if Li> 0.5, then the count value N = I +1, and Li = Li-1; By improving the deviation can not result in a cumulative, thus ensuring that in a frequency cycle L, the biggest rounding error is not greater than half the minimum resolution time τ.
Using MSP430F149 own 16-way 12-bit high-precision AD conversion, with MCU’s internal reference voltage it can work stability and has better sample and hold circuit. By selecting 16 channels’ control and storage registers as multiple sequence single sampling way for leakage current sampling, greatly enhance the speed and accuracy of sampling.
Users may need to set the leakage protection way and movement time (0-2S).
Since each system will operate in different electrical environments, which will produce different certain disturbance to the electricity grid sampling parameters, so we should do parameters correction by software. For ordinary voltage, current and its phase, ATT7028’s internal calibration methods can be used to do the digital correction and save the results to the special storage unit that ensure MCU can read the last corrected value. The correction of the leakage parameters is relatively complex, according to Fig.5, firstly we build a reference curve in MCU, then analyze the amplifier circuit characteristics and find the key nodes to ensure sampling linear range, This paper selected three node based on the actual situation: A (100mA) B (300mA) C (600mA), when the input theoretical value of the actual current measured, respectively Ia, Ib, Ic. There are correction factor
B1=((300⋅Ia−100⋅Ib)⋅100)/(Ia−Ib). (5)
Fig.4 Main program flow chart
In particular, the study to the processing speed of microcontroller and communication sampling algorithm [7] ensure the sample signal of leakage current after the amplified has close linear relationship with actual parameter in the wide range. The leakage current will instant cause the fire hazard, we should finish the sampling, converting, alarming and operation within 1 second. In this paper, full-wave Fourier algorithm is selected to finish the sampling, analyzing characteristics and making some change according to the MCU’s sample processing synchronization error.
For example, the leakage current sample in full-wave Fourier algorithm
I=1T∫i2(t)dt. (1)
0
T
Discretization: I
=1N∑ik2
k=1
N
. (2)
N = number of samples per cycle interval, ik for the k’th sample values
In the actual measurement system, because the timer counting cycles can not be infinitely small, while the sampling interval must be the smallest integer multiple of the cycle count, its value is a positive integer, so that there is rounding error, this error will continue to accumulate in the cycle, bring the cycle rounding error. In addition, due to the slow changes in grid frequency, the sampling period Ts is always based on measurements of the grid period before identified, so there is
K1=(10000−B1)/Ia. (6) B2=((600⋅Ib−300⋅Ic)⋅100)/(Ib−Ic) . (7) K2=(30000−B2)/Ic. (8)
According to the slope of the curve, the range of 100mA-600mA is divided into two ranges (100-300) (300-600). When the input value Iin is less than Ib, Iin belong to range (100-300), there is formula
I=(K1⋅Iin+B1)/100. (9)
4154
Fig.5 Measured curve
By the same token, we can get the formula when Iin at range (300-600)
I=(K2⋅Iin+B2)/100. (10) By matching the zero-sequence current transformer
(ZCT) for calibration, measurement uncertainty of leakage can be controlled at below 5%.
B. Software design of electrical fire monitoring equipment
The related monitoring and management software is designed to install on the computer as monitoring equipment. The software is using VC++ to write with a structured, modular programming. It consists of man-machine interface, database, communications, and other modules, to achieve its long-range parameter modification, control and focus on the monitoring. In accordance with the requirements of network management, software with the alarm monitoring interface that can check all detectors’ state in the network, if there is an alarm signal, it will display on the screen and trigger the monitoring equipment light/sound alarm. Then the operator could choose to cut off line, lift alarms, save record and other operations. Consider the operating system security, there is a login interface required the operator enter a password, and different login accounts bring different operate permissions. Low-level access can only observe the system operation and respond to alarm in several ways, but high-level access can set the alarm parameters and respond methods, even change the low-level access and functions, some of this setting need to restart the software after finish the setting. The whole system safe and reliable, second confirmed for the input operation avoid people’s misoperation, and system will back to main monitoring interface when operator finish the parameters setting or fault inquire.
V. EXPERIMENTAL TEST
1) In accordance with national technical standards, this study carry out performance testing on the sample (UART), as: Voltage measurement: 172 ~ 268 V (AC), accuracy of 1%; Current measurement: 0 ~ 600 A (AC), accuracy of 1%; Instantaneous leakage measurement: 0 ~ 1000 mA (AC),
accuracy of 5%;
Contact capacity: 100/225 A 220 V (AC); Communication protocols:
MODBUS, 485 interfaces, 9600 BPS; Supply Voltage: 220 V (AC);
Protection: leakage current, overheating, overload and short circuit protection; phase loss, circuit protection; over-voltage, under-voltage protection. 2) Alarm Performance
Alarm settings: 200mA ~ 800mA, continuously adjustable step to 50mA;
Alarm values set as 200mA, 500mA and 800mA. According to national standards GB14287.2-2005, the action value
should be in the range of 80%~100% set value. Table 1 shows the alarm performance test (Standard 5.2) and alarm monitoring test (Standard 5.3).
In addition, we carry a series of tests such as insulation, pressure, vibration and so on. The impact test according to standard 5.7 is not listed in the table because the sample’s weight is 5 (KG) above.
The above experiment illustrates the stand-alone electrical fire monitoring detector meets the national standards may be running in most environments, and electrical fire hazards can be quick and timely response and handling, form an intelligent monitoring network by massive detectors.
TABLE I
SAMPLE ALARM PERFORMANCE AND MONITORING TESTS 200 mA 500 mA 800 mA Response Sound
Time(s) (dB)
#1 192.2 453.2 716.3 1.0s 76 #2 193.7 427.8 664.2 1.0s 75 #3 189.3 429.7 712.0 1.0s 75 #4 190.4 442.2 703.3 1.0s 74 #5 189.6 456.3 724.3 1.0s 75 TABLE II SAMPLE TEST SUMMARY
Test Standard 200mA 500mA 800mA Result Pressure#1 5.5 191.8 452.6 716.2 Qualified
Pressure#2 5.5 192.5 426.9 665.1 Qualified
Vibration#1 5.6 188.5 438.7 711.9 Qualified
Vibration#2 5.6 191.2 441.3 702.4 Qualified High 5.8 191.7 453.1 715.8 Qualified temperature#1
High 5.8 192.6 425.7 665.8 Qualified temperature#2
Low 5.9 188.4 440.2 711.5 Qualified temperature#1
Low 5.9 191.3 443.1 704.2 Qualified temperature#2 Constant hot 5.10 187.6 455.2 726.1 Qualified and humid Insulation 5.4 >500MΩ Qualified Resistance
VI. SUMMARY
Electrical fire monitoring system is an intelligent protection products applied to online real-time monitoring the
4155
low-voltage power supply route. It can effective prevent the electrical fire hazards from leakage current caused the short circuit; monitoring the protected route’s voltage, current, power, electric degrees, ambient temperature and other parameters, with multiplexing fire linkage and alarm, communicate to monitoring equipment by UART or TCP/IP agreement, fully meet the comprehensive management of remote monitoring.
Stand-alone electric fire detector with advanced micro-electronic technology, modular design concept, combining the traditional low-voltage protect electrical appliances and electronic technology, is the product that adapt to needs of social development. Experiments show that this system has high precision, safety and reliability, low false alarm rate, easy operation and maintenance, can replace traditional air switch and GFCI. The system could be widely used in schools, commercial buildings, factory workshops, markets, industrial and mining enterprises, key national fire service units, intelligent plot, petrochemical, telecommunications and defense sectors which require electricity and electrical fire safety protection.
REFERENCES
[1] GB 14287.2-2005 Alarm system for electric fire prevention Part 2:
Leakage current detecters for electric fire prevention
[2] Sheng Jianhua, Yang Yanqin, Qu Xiaoshu. “MSP430 series of 16-bit
Ultra-Low-Power MCU Principles and Applications,” Beijing: TSINGHUA University Press, 2004.
[3] Zhang Qi, Zhang Ying, “mplementation on serial portcommunication
between PC and MSP430 single chip microcontroller,” Chinese Journal of Construction Machinery, vol. 5, pp. 22-25, May 2007
[4] Wang Ping, Yu Gang, Hu Xiangdong, Yuan Li, “Hardware design of PSE
based on MSP430 MCU,” Journal of Chongqing University of Posts and Telecommunications(Natural Science), vol. 19, pp. 192-196, 2007
[5] Zhou Dexiang, Qin Shuying, Yang Hongwei, “Study on the Applications
of ATT7028 in Measuring Electric Parameter,” Modern Electronics Technique vol. 8, pp. 174-176, 2008
[6] Liu Guofu, “Theoretical for using of zero-sequence current transformer
design protection device,” Science and Technology innovation Herald, vol. 3, pp. 39-40, 2008.
[7] Wen Dingdu, “An Sampling Technology in the Electric Power
Monitoring System,” Techniques of Automation & Appications, vol. 9, pp. 92-93, 2006.
[8] Xiang Xinjian, “Analysis and realization of synchronous sampling
technology for power network parameters of double power source automatic transforming switches,” Energy Engineering, vol 6, pp. 17-21 , 2007
4156
因篇幅问题不能全部显示，请点此查看更多更全内容