design of hci system in monitor and control

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Design of HCI System in Monitor and Control

Centre Based on Dry-type Transformer

Temperature ControllerHainan Long1 and Chun Wang2*

(12

College of Electronic and Information Engineering ,Hebei University ,Baoding071002 ,Heibei provinceChina )*E-mail:

Abstract--Dry-type transformer temperature controllers are

installed on transformers and located in different sites outside,

which brings inconvenience to the management and operation.

The HCI(Human Computer Interface) in monitor and control

centre whose function is complete and direct-viewing can be

operated simply and easily, and it can manage and operate many

temperature controllers inside the monitor and controller centre.

Using RISC(Reduced Instruction Set Computer) high speed

MCU(Micro Control Unit) ATmega128, a dry-type temperature

controller is designed, and then embedding ModBus-RS485

protocol, realizing the data communication between 32

temperature controllers and HCI in monitor and control centre.

In this way, a temperature control system is designed. The

hardware design and principle of temperature controller are

introduced, main functions of HCI system that is designed with

Delphi in monitor and control centre are described and design

block diagram of the main program is given, with the

introduction of embedded Modbus-RS485 protocol and CRC-16

checking. Practice proves that the whole system that consist of

temperature controller and HCI in monitor and control centre

runs well.

Key words--dry-type transformer;HCI(Human and Computer

Interface); ModBus; monitor and control centre ; temperature

controller

I. INTRODUCTION

R

co

Y-TYPE transformer because of its merits such as

nvenient maintenance, fireproofing , dustproofing and

burning isolation, obtains widespread application in our

country in recent years . The winding temperature of

transformer supasses the insulation bearing temperature to

break the insulation ,which is the primary cause for the

breakdown of transformer. Therefore, carrying on the

real-time monitoring and controlling to the winding

temperature of transformer, has guaranteed the reliable and

safe running of transformer.lengthened its service life[1-2].

According to transformer design target and product request,choosing ATmega128 as main processor[3-4]

,a temperature

controller with low cost, high reliability and perfect

performance is designed Although providing each transformer

a temperature controller have just solved the problem of the

protection to one transformer rather than to the entire power

supply system[5]. While through RS485,HCI system in monitor

and control centre allows the winding temperature

demonstration of 32 transformers and the operations on 32

temperature controllers such as writing down working states or

the power-cut records, inquerying history records, processing

the problems of breakdown automatically and so on. In this

way ,we realize the safe and stable operaton of the entire

electrical power distribution system that consist of 32

transformers and others . And sovle the problem of the

inconvenient operation on temperature controllers located in

different sites,realizing the real-time controlling and setting to

each controller[6].

II. HARDWARE STRUCTURE AND PRINCIPLE OF

CONTROLLER[7-9]

The temperature controller of dry-type transformer based on

ATmega128 is mainly composed from 4 parts[3-4]: MCU(Micro

Control Unit) processor, temperature sensor, A/D module,

display and control module; while as one of the controllers, it

communicates with HCI(Human and Computer Interface) in

monitor and control centre through RS485 just as others do.

Figure 1 shows system structure schematic diagram. Selecting

MCP3204 which is produced by Microchip Corporation as AD

chip, using TLC5620 which Texas Instruments Corporation

produces as DA chip, choosing Max485 which Maxim

Corporation produces as 485 correspondence , using chip

LM324 to make the signal enlargement, using LM7812 and

L7805 to make three-end manostat, a dry-type transformertemperature controller with high performance and low cost is

designed.

Temperature

Sensor Pt100A/D

ConvertMCU

ATmega128

Display

and

Control

HCI

MCU

ATmega128

A/D

Convert

Display

and

Control

Temperature

Sensor

Pt100

RS485

Fig. 1 System structure schematic diagram.

Temperature controller of dry-type transformer allows to

D

2008 International Conference on Condition Monitoring and Diagnosis, Beijing, China, April 21-24, 2008

978-1-4244-1622-6

/08/$25.00 2007

IEEE


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carry on the real-time monitoring and controlling to the safe

running of dry-type transformer: monitor the running states of

transformers and control the air blower starting of

transformers ;and in this way lengthens their service lives,

keeping the electrical power distribution system runs stably

and safely. Through RS485,HCI system in monitor and control

centre which is designed with Delphi allows the temperature

demonstration and control of 32 temperature controllers

located in many different places outside. Sampling thetransformer temperature by temperature sensor

Pt100 ,electrical signal obtained through enlargement and AD

transformation, is processed by MCU Atmega128, making

temperature controller to realize temperature demonstration

and according to comparison result with control temperature

value, to start air blower ,to alarm ,to trip or not. Meanwhile it

communicates with HCI system in monitor and control center

through RS485 . There will be elaborate introduction in the

next part about it .

III. DESIGN OF HCI SYSTEMA. Function Introduction

According the request from user, in order to realizetemperature demonstration and control of many temperature

controllers outside, HCI system need to achieve such functions

as Fig2 shows.

Fig. 2 System function diagram.

1. Correspondence Port SettingThe user could modify serial port parameter (port number,

baud rate, data bits, check bits, stop bits) in order to suit for

various serial communication conditions and thus enhances

compatibility to different temperature controllers.

2. Force Air Blower to Start

The user could force air blower of temperature controller

manually, thus give real-time control to the cool system of

transformer and keep the stable and safe running of dry-type

transformer.

3. Inquiry and Print

The user could establish conditions such as temperature

controller address, the beginning and termination date to

inquiry history record of temperature controller and then save,

set the print and print. It facilitates user to exam history

working records of temperature controller and to study

working states of dry-type transformer.

4. Display Time SettingThe user could set the display time of three-phase

temperature curves of one temperature controller, and thus

determines total tour demonstration time of all the temperature

controllers at last realizes many temperature controllers tour

demonstration. When need to study temperature curves of one

temperature controller in order to study the working states of

corresponding transformer, a longer time could be set here.

5. Address Setting

The user could add or delete address of temperature

controller to decide which temperature controllers

temperature curves need to demonstrate in order to study the

working states of corresponding transformers here.

6. Control Temperature SettingThe user could set the temperature value of start or stop air

blower, as well as the temperature value of alarm and trip in

order to exert flexible and automatic real-time temperature

controlling on transformers.

7. Main Interface

There are 2 datasheets in the main interface. The

Current-State one shows the address of temperature controller,

the date and time , the three-phase temperature value, the

control temperature as well as the working states of

temperature controller. It is very convenient for the user to

look over the current and history temperature records, the

history information of start or stop air blower manually or

automatically as well as the modifying value records of controltemperature. The Power-Cut datasheet records the three-phase

temperature value and the temperature controllers working

states of the power-cut moment , whose function is just like the

black box, so it is very convenient for user to study the

power-cut reasons of transformer. Another is the 3 pieces of

temperature curves. The temperature curves simultaneously

show three-phase temperature value, and user can set display

time of each temperature controller (Display Time Setting), as

well as set to

display which temperature controllers three-phase

temperature curves (Address Setting).They are the

direct-viewing evidences for user to analyze the workingconditions of temperature controllers . Some indicating lights

tell user the working states of controller and corresponding

transformer. Figure 3 shows the main interface .

B. Software Realization of Main ProgramLower position machine (temperature controller),

corresponds with upper position machine(HCI) in monitor and

control centre through RS485 .HCI send data to all the

controllers ,which including 1 byte address code,1 byte

function code,2 bytes CRC checking code, and some bytes

other information code. When one of the controllers recognizes


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the address ,it exams the function code field, if it is 03h,that

means HCI wants to get the controllers three-phase working

states, the records of the moment of power-cut as well as the

CRC checking code figured out by temperature controller. HCI

checks whether the CRC checking code received is equal to the

Fig. 3 Main interface of HCI.(Power-cut records.)

one itself just calculated; if yesTransmission success, it

will write the received three-phase temperature and working

states of temperature controller into Current-State database,

and the information will be found in Current-State datasheet in

main interface, with the corresponding indication light bright

or dark. If the received records of the moment of power-cut

change(Power-Cut happens),it will also write the records into

the Power-Cut database and the information will also show in

the Power-Cut datasheet in main interface. If the function code

field is 05h, that means forcing air blower to start or stop. The

temperature controller do the action and reply the data

including their working states and CRC checking code figured

out by itself. If the two CRC checking code of HCI sent andreceived is the same one, that proves they communicate with

each other correctly. The received working states of

temperature will be written into the Current-State database and

be shown in the Current-State datasheet in main interface. And

if the function code is equal to 10h,that means modifying the

control temperature value of temperature controller (air blower

start or stopalarm and trip ).The temperature controller

answers and sends back the modified temperature value. If the

two CRC code is equal(Transmission success),the received

records will be written into Current State database, and will

also be shown in Current-Sate datasheet in main interface .If

the function code is equal to none of the three, or the address

code belongs to none of the temperature controllers, that means

communicating data have errors, then drop it and start to send

the next data. Main Flowchart is Figure4 as follows.

Send dada to

controller

Address accord

Function

code=03h

Function

code=05h

Function

code=10h

Controller reply

temperature

power-cut records

Received CRC=send

CR C

Power-cut

records change

Write corresponding

value into 2

datasheets,correspon

ding indication light

bright or dark

Write corresponding

value into Current-

State datasheet,light

bright or darkSend next data

Start or stop blowers

and reply

controller s

working state

Received CRC=send

CR C

Controller modify

control temperature

and reply

Received

CRC=send CRC

Write control

temperature into

Current-State sheet

Y

Y

Y

N

Y

YN

Y

Y

N

N

N

N

N

Fig. 4 Main flowchart.

C.Modbus-RS485 Protocol Introduction[10]

1. Modbus Protocol

The common language used by all Modicon controllers is

the Modbus protocol. This protocol defines a message

structure that controllers will recognize and use, regardless of

the type of networks over which they communicate. It


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describes the process a controller uses to request access to

another device, how it will respond to requests from the other

devices, and how errors will be detected and reported. It

establishes a common format for the layout and contents of

message fields.

Controllers can be setup to communicate on standard

Modbus networks using either of two transmission modes:

ASCII or RTU.

This paper has used the Modbus-RS485 correspondence protocol to implement the correspondence between lower

position machine(controller) and on the position

machine(HCI),having taken Modbus-RTU (Remote Terminal

Unit) query-response way, with the baud rate 9600 BPS, 8-bit

data as well as non-parity check bit ,and the outset and stop bit

each having 1 .The user can also select another

communication way(Correspondence Port Setting).

2. Modbus Message FramingA typical RTU message frame is shown below as Table 1.

TABLE 1RTU MESSAGE FRAME

Start Address Function Data CRC End

T1-T2-

T3-T4

8bit 8bit n x

8bit

16bit T1-T2-

T3-T4

D. CRC-16 CheckingIn RTU mode, messages include an errorchecking field

that is based on a Cyclical Redundancy Check (CRC) method.

The CRC field checks the contents of the entire message. The

CRC value is calculated by the transmitting device, whichappends the CRC to the end of the message. The receiving

device recalculates the CRC of the received message, andcomparing the two CRC, if they are different from each other,

that means the transmission has errors.

.CONCLUSION

Embedded ModBus-RS485 protocol, we enhance the

liability of data communication and compatibility of the

system, which makes HCI givethe real-time monitoring and

controlling to 32 dry-type transformers successfully .What

make the whole system of temperature control superior are

the low cost and high reliability of hardware choice and the

perfect software(HMI) functions. It realizes the

transformation from the safe protection of single transformer

to the monitoring and controlling safe operation of entire

electrical power distribution system. The biggest merit of the

temperature control system is HCI system in monitor and

control centre whose function is complete and direct-viewing

and which is operated by user simply and easily .Anothermerit is that it is very convenient for user to exert real-time

study on the working temperature of transformers through the

setting of display time and address. The principle of design

and the programming thought, could be applied in other

situations of temperature monitoring and controlling , which

makes it have very high promoted value.

V. REFERENCES

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[2] A.P. Zhang, J.J. Wu, Development of temperature control instrument

for dry-type transformer, Engineering Journal of Wuhan University,

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Atmega128,Beijing:Beijing Aerospace University Press,2004.

[4] [4](2004).ATMEL.Atmega128datasheet.[Online].

Available:http://www.atmel.com/dyn/resources/prod_documents/doc2467_cn.pdf

[5] C. Ji, Application of PLC in distributed supervisory system of dry

transformer, Electric Power Automation Equipment, vol. 23, pp.79-81,2003.

[6] H. Wang, L. Wang, Z.Z. Jiang, Application of touch screen

technology in dry-type transformer temperature control system,

Electric Times, vol. 16, pp. 86-87, 2005.[7] F.Y. Zhang,C.J. Chen, Q.W. Lai, Design of temperature measurement

controller for DTC-4305 three-phase dry transformer, Journal of

Nanchang University(Natural Science) ,vol. 22,pp. 239-244,1998.

[8] Y.K. Zhao,J.Q. Wang, Intelligent temperature controller design ondry-type transformer based on Atmega16,Instrumentation Technology,

vol. 1, pp. 47-48, 2005.

[9] Q.X. Zhu, M.Chen, Instrument with single - chip microcomputer formonitoring temperature of drytype transformer , Transformer, vol. 5,

pp. 20-22, 1998.

[10] X.H. Yang,Industrial data communication and control networks,Beijing:Tsinghua University Press,2003.

[11] (2004). ModBus Communication Protocol [Online].Available:

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