ĐỀ TÀI THIẾT KẾ CHẾ TẠO VÀ THỬ NGHIỆM CÁC MẠCH ĐO ĐẾM ĐỌC KẾT QUẢ QUA ĐƯỜNG TRUYỀN ĐIỆN LƯỚI

DAI HOC QUOC GIA HA NOI KHOA CONG NGHE BAO CAO TONG HOP De tai: THllT K i CHE TAO VA THUf NGHIEM CAC MACH DO DEM DOC KET QUA QUA DUftNG TRUYEN LUdl (De tai nghien cihi khoa hoc cap DHQGHN Khoa quan ly) Ma sd: QC.02.03 Chii tri: TS Ngo Dien Tap Tham gia thuc hien: Th S TrSn Xuan Tii CN Trdn Diic Tung OAI HOC Q U O C QlA HA N O r IRUNGJAM TH6NG TlfV THU Ha Noi 2004 MUC LUC Trang Muc luc Chiicmg Vai net ve qua trinh phat trien eua PLC Chucfng Thiet ke va x^y dung modem PLC 2.1 Ghep noi tin hieu, 66 suy giam va trd khang truy nhap 2.2 Phucfng phap dieu che FSK 2.3 So khoi va nguyen ly hoat dong cua modem PLC 2.4 M6t so dac tinh va thong so eiia modem PLC dung lam thuc nghiem 11 2.5 So nguyen ly ghep noi cae thiet bi iing dung vdfi cae modem PLC 13 Chucmg Thir nghiem mot s6' iing dung lucmg va dieu khien tren mang dien ludi 16 3.1 Mot so thu nghiem co the trien khai vdi cac modem 16 PLC linh vuc ludng va dieu khien 3.2 He thong nhiet qua mang dien ludi 18 3.3 Mot sd ket qua thuc nghiem va thao luan danh gia 23 Tai lieu tham khao 33 Chiromg VAI NET V^ QUA TRINH PHAT TRI^N CUA PLC Qua trinh phat trien eua cdng nghe PLC (Power Line Communication) se dugfc trinh bay p h ^ theo gdc tim hi^u kha nang va phan tfch nhung han che eiia cac iing dung co dien Mang dien ludi dugfc sii dung cho viec truyen thong du" lieu sau bat d^u cdng cuoc dien khf hoa Tii nhung nam 1920, tai cac phdng thi nghiem d Chau Au da tien hanh thu nghiem truy6n tfn hieu thoai tren dudng day dien cao the Sd dl viec truyen thdng tren mang dien ludi cd tfnh ha'p dan manh cac nha dSu tu la vi cac nguyen nhan bat nguon lit lich su Chiing ta biet rang de tn va on dinh dugfc he thdng eung cap dien eao the tren pham vi rdng Idn thi nhiem vu hang dau dat la phai lien tue tri cong tac quan ly van hanh, kiem tra, siia chua va khae phuc cac su cd Cong viee ddi hdi phai cd mot kenh thdng tin hai chidu lien tue va tiie thdi Thf du, chiing ta phai thiet lap cac kenh thong tin giiia nha may phat dien, cac tram bien the, cac thiet bi chuyen maeh va cac diem ket ndi tren mang hay cae diem ket ndi giiia cac mang vdi Tuy nhien, tai thdi diem dd chua cd mang dien thoai nao cd the bao phii toan bg cac khu dan cu, cac khu cdng nghiep eung nhu cac diem trgng yeu ciia mang dien ludi nhu da ke tren Tham chf cho den bay gid van cdn nhieu diem trgng yeu ciia mang dien cao the ed nhu cau truydn thong du lieu va trao doi thdng tin vin chua dugc ket ndi thdng qua cae mang dien thoai Dd la chua ke den cac nhu ciu ket ndi de ludng va kiem tra giam sat tii xa Tai nhung diem da cd ket ndi dien thoai thi ngudi ta ciing khong khdi lo lang ve va'n de gian doan thdng tin Mdi xay hien tugng gian doan thdng tin mang dien thoai gap phai su cd cung gay nen nhiing thiet hai nang ne eho nganh dien lue Han niia, chi phf dau tu de cd dugc mdt dudng day dien thoai den cac vung xa xdi va gia cude phai tra sau mdi lan thuc hien dam thoai hay trao doi du lieu la rat Idn Chfnh nhung nguyen nhan da thiic day nganh dien luc va cae nha khoa hgc vao cugc de phat trien cong nghe PLC Tir nhfltig nam 1920 cua the ky trudc, ciing vdi viec six dung cdng nghe tan sd sdng mang tren dudng day dien thoai, cdng nghe tSn sd sdng mang cung da bat ddu duac iing dung d^ truyen dii lieu tren mang dien cao the [11] Vdi nhiing d^u tu dang ke v^ ky thuat nhd su tie'n bd vuot bac cua cac phuang thiic truyen thdng dii lieu da giup cho cac nha khoa hgc va cac cdng ty dien luc thuc hien duac ddng thdi ca truyen tai nang lugfng ft suy hao va truyen thdng tin vdi tin cay cao tren cung mang dien ludi Cung vdi su phat trien cua khoa hgc cdng nghe, kinh te' xa hgi, cac mang dien cao the' ciing dugc xay dung va phat trien mot each nhanh chdng nham dap ling nhu cSu sir dung dien phuc vu cho sinh boat va san xuat Tit dd, cac cdng ty dien luc bat bude phai xay dung cho minh mdt mang ludi thdng tin day du va chinh xac dung de quan ly va van hanh he thdng cung ca'p dien nang va phuc vu cho cac muc dfch khae nhu thdng tin lien lac ngi bd va eae iing dung ludng, giam sat va dieu khien tCf xa Nhiing nhiem vu cd the dat de tan dung mang dii lieu cua cac cdng ty dien luc cd the dugc phan ba nhdm chfnh sau: • Quan ly van hanh • Kiem tra giam sat • Han che hdng hdc va khae phuc cac su cd Quan ly van hanh tiic la bao dam tdi uu phan phdi nang lugmg, mgt mat phai han che' su lang phf nang luong, mat khae phai dam bao dii cdng suat de dap ling cho nhu cau sir dung vao nhiing gid cao diem De thuc hien dugc nhiem vu ddi hdi phai cd mgt he thdng truyen thdng dii lieu tiie thdi va cd tin cay cao Nhiem vu kiem tra giam sat giiip cho mang ludi dien hoat dgng thdng sudt va lien tuc Nhiem vu tap trung chii yeu vao cac van de lien quan den cac thdng sd hoat ddng ehfnh nhu nhu cau ve nang lugmg, cdng suat phat, dien ap va tin sd Kidm tra giam sat cac thdng sd tif dd dua eae bien phap, cac quyet dinh dieu chinh phii hgfp Vdi nhiem vu viec dam bao thdng tin lien tuc la van de dugc quan tam hang diu Nhiem vu han che hdng hdc va khae phuc su ed tiic la dua cac bien phap phdng chdng va khae phuc cac su cd khdng mong mudn xay Dac biet, trudng hgp xay su cd d mang dien cao the thi phai nhanh chdng dua cac bien phap kip thdi va huu hieu de xac dinh va khae phuc su cd nham giam thi^u hau qua ciia nd Chfnh vi vay, viec nam bat kip thdi cac thdng tin lien quan de'n nha may phat dien, cac tram bie'n the' ciing nhu cac cdng ty dien luc la rit cin thie't Trong trudng hgp viec truyen thdng tin phai thuc hien tren mot khoang each kha xa, dd chi phi phai tra di cd dugc mdt kenh thdng tin la rit Idn vk di6u anh hudng den lgi nhuan ciia nganh dien luc Ciing vdi su phat tridn nhanh chdng ciia cac cdng nghe khae ITnh vuc vien thdng va cdng nghe thdng tin, cho de'n cdng nghe truyen thdng tren mang dien ludi da cho phep cung ca'p dich vu truydn tai dien ket hgp vdi truyen dii lieu mang thdng tin true tie'p tdi ngudi su dung Thuc te' cho tha'y de cd the giai quyet van de truyen thdng tin tren dudng truyen dien ludi cd rit nhieu vin de cin nghien ciiu giai quyet Trudc het, dudng truyen dien ludi gidng nhu mdt angten ca Idn, tie'p nhan rit nhieu nhidu, nhung dong thdi cung phat xa tfn hieu Thanh thir sir dung cho iing dung truydn thdng tin thi qua trinh phat xa cung cin dugc xem xet mgt each than trgng Tiep dd la vin dd xay dung cac bd lgc cd dai thdng thfch hgp Mdt van dd khae la mgi he thdng truydn thdng cin cd su phdi hgp trd khang thfch hgp, tren dudng truydn dien luc lai rat khd thoa man dugc vin dd Nguyen nhan la trd khang ciia tai viia thay doi theo thdi gian, viia thay doi theo vi tri tren dudng truydn, cd the thay doi lit va mili dm den hang nghin dm, ddng thdi gin cac tram bien ap lai rit thip Mdt sd trd khang khdng dd phdi hgp lai cd the xuat hien tren dudng truydn dien ludi, chang han nhu cac hop dau cap Vi vay viec giam suy hao ciia tfn hieu truydn thdng tren dudng truydn dien ludi la mgt ddi tugng nghien ciiu kha phiic tap Tiep dd la va'n dd nhidu: nhidu tren dudng truydn dien ludi la tap hgp ciia nhidu loai nhidu khae da tham nhap dugc vao dudng truydn, phong phii ca vd loai, Idn cung nhu ca vd each tham nhap vao dudng truydn Cac tai duge da'u vao dudng truydn dien ludi nhu tivi, may tfnh, may hiit bui, ddu phat nhidu va dugc lan truydn tiep tren dudng truydn dien ludi, cac he thdng truyen thdng khae ciing dua nhidu vao dudng truydn dien ludi Cd the neu vd sd cac van dd cin nghien ciiu Chfnh vi vay ma ttr nhung nam 20 ciia the ky trudc cdng nghe truydn thdng tin tren dudng dien lue da dugc nhidu nha ky thuat, nhidu cdng ty, nhidu ca sd nghien ciiu quan tam den Trong cude chi^i tranh the' gidi, cac cdng trinh nghien ciiu tam diing nhung sau chie'n tranh the' gidi ke't thiic lai dugc quan tam de'n Gin day, xu hudng tim kie'm mdi trudng truydn thdng cho chat lugng va hieu qua, van dd PLC lai dugc chu y nhidu han Trong khudn kho cua mdt dd tai cip trudng Dai hgc, dd tai chi tap trung nghien ciiu: Thiet ke che tao vd thvc nghiem cdc mgch doi dem dgc kit qud qua du&ng truyen dien ludi Vdi ndi dung chii yeu la: • xay dung mdt sd he ludng de dap yeu ciu dgc tur xa • xay dung he thdng truydn sd lieu ludng bang sdng mang (mgt sdng mang) va mgt he phat hien sdng mang ket hgp vdi tach sd lieu ludng • Ke't hgp he thdng va hoan chinh phuang phap n Thir nghiem danh gia va dua vao lip ghep thanh mgt he thdng hoan chinh Trong khudn kho ciia dd tai, mdt he thdng nhiet qua dudng truydn dien ludi da dugc lip rap va ihix nghiem, mgt sd cac thao tac didu khien ca ban nhu ddng/ ngit, truydn dii lieu nhi phan da dugc thuc hien Chirong THI^T Kt VA XAY DUNG M D E M PLC 2.1 GHEP NOI TIN HIEU, DO SUY GIAM TIN HIEU VA TR6 KHANG TRUY NHAP De truyen thdng tin tren mang dien ludi thi cac tfn hieu sdng mang cd tin sd nam pham vi quy dinh ciia chuan EN 50065 phai dugc dua len cac dudng day dien ludi Vdi cac dai tin sd thip mudn dua tfn hieu len dudng day dien ludi phai tieu tdn mdt cdng suit kha Idn, dac biet cac tin sd cua tfn hieu gin vdi tin sd dien ludi, chang han ca vai tram Hz t^l Sado nguyen ly C R V,.A/ Maeh tircrng dircmg C Ly tmyng Hinfi 2-1 Sa nguyen ly cua khoi ghep noi tin hieu vdi dirdng day dien ludi Khi ndi mot modem de truydn du lieu tren mang dien ludi thi trudc bet cin cd hai dudng day din tin hieu Hinh 2-1 cho thay phuang thiic ghep ndi tfn hieu giiia modem PLC va dudng day dien ludi bang mdt bien ap PLC vdi hieu iing thdng cao Tu C dugc dung de each ly nguon dien ap 220 V C) phan phat thi tu C dugc chgn khoang den |iF, tai phin nhan thi gia tri lai thudng dugc chgn c5 100 nF Dd dung hoa giiia phin phat va phin nhan thuc nghiem ca phin phat va phin nhan cung dugc thuc hien tren cung mgt khdi ghep ndi vdi dudng truyen dien ludi nen nhdm tac gia da chgn gia tri cua tu la 470 nF Dien trd R dugc chgn cang nhd cang tdt tai phin phat Dien trd maeh thuc nghiem cua nhdm tac gia dugc thuc hien dong thdi bang dien trd ciia bie'n ap va dien trd ciia ciu chi nham ca muc dfch bao ve cd su cd vd dien Tai phin thu, dien trd R gdp phin hinh ghep ndi ydu vay gia tri cua nd nen dugc chgn Idn han trd khang ciia dudng day mgt sd tai lieu nghien ciiu cd khuye'n nghi tai phin phat dien trd cung nen nhd ban Q, tai phin thu dien trd c5 vao khoang 80 den 120 Q, vay viec sir dung chfnh dien trd ciia bien ap va ciu chi ciia nhdm tac gia la hoan toan hgp ly va chap nhan dugc Trong dd, kich thudc cua cac cudn day L^ va L2 nen dugc chgn can than cho trd khang ciia chiing (27C/JL12) ludn ludn Idn hon cac trd khang da ket ndi dai tin sd hoat ddng ciia /} Trong cac tfnh toan, chiing ta cd the tap trung chu yeu vao phfa dien ngudn, chang han gia tri chfnh xae ciia L;, maeh tuang duang d hinh 2-1 Sd di nhu vay la chiing ta mong mudn cd dugc mgt trd khang ldi phin phat nhd (« Q) Bang each chgn ty le vdng quan bien ap Ni : N2 ta cd dien ap ngudn nudi bdi ting ldi dugc bien doi mdt each tuang ling, dd ta cd tfn hieu xuat hien tren dudng day dien ludi cd bien phil hgp Gia tri Ni : N2 thudng nim khoang tii 1/2 den 1/4 Trong phin thuc nghiem ciia dd tai nay, nhdm tac gia da chgn ty le vdng quin ciia bien ap PLC la 1/4, dd tfn hieu cin dua vao bien ap de truydn ten mang dien ludi dugc khue'ch dai viia du dap iing vdi ty le dd (cd khoang 40 - 44 VAC) phfa nhan, bien ap thudng dugc ndi them mdt bg lgc thdng dai, trd khang ldi vao ciia bd lgc dugc dugc chgn lit khoang den vai tram dm [21 Trong thuc nghiem d day nhdm tac gia chgn gia tri trd khang vao ed 150 Q Didu cd nghla la ty le N-^ : N2 cd the la 2.2 PHUONG PHAP DIEU CHE FSK d day nhdm tac gia khdng mong mudn trinh bay lai ly thuye't ciia phuang phap didu che' FSK ma chi mudn trinh bay mdt sd ly tai lai chgn phuong phap didu chd FSK phin thuc nghiem LTu diem Idn nhat ciia phuang phap didu che' FSK la viec thie't ke' va thuc hien dd dang d ca phin phat va phin nhan, ca cdng nghe tuang tu va cdng nghe sd Vao cud'i nhiing nam 1980 nhidu nha san xuit da dua cac vi maeh diing cho cac umg dung truydn thdng tren mang dien ludi, nhung hiu he't cac vi maeh dugc xay dung dua tren phuang phap FSK [2] Viec sir dung phuang phap didu che' FSK cung cho ta thuc hien viec truydn thdng vdi dd tin cay va tfnh khang nhidu cao [!» 3], vdi muc dfch tiep can vdi cdng nghe va vdi nhiing ly tren nhdm tac gia da khdng ngin ngai phai lua chgn phuang phap didu che' FSK de thuc hien phin thuc nghiem ciia minh 2.3 SO DO KHOI VA NGUYEN LY HOAT DONG CUA MODEM PLC Sado khdi cua modem PLC: Cvbc]i noi JITL lliiol hi iX\> ^AAAA/* *—iDerriod < Amp Fill Bo tiU> diliv Ji>ii!> * Mod ^Filter Chiiy^:iit3oi Filter C c B(>ylicp noi voj dirim^ day dicu laoi Amp Hinh 2'L So khoi cua modem PLC Trong mddem PLC, khdi CPU thuc hien chiic nang didu khien toan bg boat ddng he thdng De thuc hien dugc chiic nang dd, khdi dugc nap mgt chuang trinh phin mdm didu khien mgi hoat dgng cua mddem PLC va cac phuang thiie giao tie'p vdi cac thiet bi ghep ndi vdi mddem PLC Khdi ghep ndi dudng day thuc hien viec ghep ndi mddem PLC vdi dudng day dien ap 220 V va lgc nhidu dudng day Trong maeh thi nghiem khdi dugc thuc hien bang mdt bien ap PLC va mgt tu lgc nhidu 470 nF/ 250 V Bien ap dugc chgn cd ty sd vdng quin giiia cudn sa ca'p va cudn thii cip la 1:4 Tai cac kenh vao cdn cd hai phin he't siic quan trgng dd la bd didu chd va bd giai didu che day phuang phap didu chd dugc sir dung la didu che FSK vi cac ly nhu da dd cap d phin tren Ngoai cdn cd cac bd lgc chdng nhidu va loai trii cac boa ba Tfn hieu trudc truyen di cung nhu sau nhan vd ddu dugc khuech dai nhd cac bg khue'ch dai dat lai cac vi tri nhu sa khdi hinh 2-1 De he thdng boat ddng mdt each ddng bg nhip nhang thi khdng the khdng cd khdi dong ho he thdng va dong bg he thdng Khdi ddng bg va cip xung dong hd cho toan he thdng dugc nudi bang mdt bg cdng hudng thach anh 11,0592 MHz Han niia, mddem PLC cdn cd ldi cap xung ddng hd cho cac maeh iing dung ghep ndi vdi chfnh nd Hoat ddng ciia he thdng dugc md ta nhu sau: Khi d chd phat, mddem PLC nhan tfn hieu tii cac thiet bi ngoai vi thdng qua cong truydn thdng ndi tiep Tfn hieu dugc xir ly nhd khdi xu ly trung tam va sau dd dugc dua tdi bd didu che FSK Tai day tin hieu dugc didu che theo phuang thiic didu che FSK vdi tin sd trung tam la 82 kHz Vdi miic Idgic "0" tin sd quy dinh ldi se la 82 - 0,3 kHz va vdi miic logic " " thi tin sd ldi tuang ling se la 82 + 0,3 kHz Ket qua la tai ldi ciia bd didu che FSK ta thu dugc mgt tfn hieu didu che FSK tuang iing vdi dii lieu ldi vao Tfn hieu se dugc dua qua mgt bg lgc va sau dd dugc dua tdi mgt bd khuech dai nham dam bao bien phii hgp trudc dua vao khdi ghep ndi vdi dudng truydn dien ludi 220 V Tai khdi ghep ndi tfn hieu se dugc dua len dudng day dien ludi 220 V nhd mgt bien ap PLC va mgt tu 47 nF Ngugc lai, hoat ddng d che thu mddem PLC nhan tfn hieu mang thdng tin tren dudng truydn dien ludi 220 V thong qua khdi ghep ndi dudng day dien ludi Khdi ghep ndi ciing chfnh la khdi ghep ndi hoat dgng d che phat Tuy nhien, ldi tfn hieu ciia khdi khdng dugc dua vd dudng phat tfn hieu d che phat va dugc dua vao mdt bd lgc thu tfn hieu Tfn hieu sau dugc lgc nhidu se dugc dua qua mdt bg chuyen doi tin sd nhim thu duge ehfnh xac tfn hieu cd sdng mang diing theo quy udc Tfn hieu sau chuyen doi tan sd 10 Mot Ihiet ke vd mo hinh truydn dii lieu lucmg nh6 tin hieu mang de ^^y dung he thdng lucmg tren mang dien sSn co ^, M « i : Nam 2001, ben A cap cho ^^„ ben ^B SO ^ ^» ^v tidn «^» la ^ trieu dong ^ *'V :; trieu d6ng) tong so kinh phi ba chue (30.000.000 d) trieu dong ciia de tai da dugc Chi phieu the nhu sau: Mm no 112 112 114 119 145A 145B 134 Cung ung van phong Hgi thao Cong tac phi Chi phi thue muon chuyen m6n Chi phi hoat dongithuyen m6n (lam maeh in, ) Mua sdm thiet bi (von ke chinh xac) Mua sdm linh kien le Chi khae Tong cong: trieu 0,5 trieu trieu trieu 0,5 trieu 15 trieu trieu trieu 30 trieu Dieu 4: Ben B co trach nhiem chi tieu kinh phi dugc cap theo dung miic dich, dung che tai chinh hien hanh va quyet toan vai phong Hanh chinh - Tong hgp trudc ngayoZ5'//iZ/200a Dieu 5: Hai ben cam ket thuc hien dung cac dieu khoan da dugc ghi hgp d6ng Trong qua trinh thuc hien hgp ddng, hai ben phai thong bao cho nhiing vin de sinh va cung ban bac, giai quyet Dieu 6: Hgp d6ng dugc lam ban, m6i ben giu ban, ban giri phong HC-TH khoa Cong nghe DAI DIEN BEN B NGO DIEN TAP, TS Ha noi, ^4 thdng 0^ ndm 2002 ^^^Dp^BENA The Chinese Conference on Power System Protection CONTROL OVER THE POWER LINES Ngo Dien Tap, Tran Xuan Tu (Faculty of Technology, VNU Hanoi) Abstract: Now, the power line is not only used to supply power, it is also used as a medium to transfer control-data Data transmission system is designed and implemented in order to take measurements remotely over the powerline for control purpose The data maybe temperature of environment In this case, the system controlled by a microcontroller of the 8051 family peftbrms data transmission from sensors to the control-unit and the display-unit through interconnection with a PLC-modem A proper software is written to drive the control and measuring system, especially in reading data at the sensors and sending them to the control-unit and display-unit over the power lines The system described in this paper can also be modified to controV measure other parameters of the environment, for example, humidity, pressure, etc., or controlling data, timing event and many other type of information Introduction Together with the use of the carrier-frequency technology over postal lines around 1920, one began to apply this technology for data transmission over high-voltage networks or powerlines ''I Recently, the under structures of the powerlines have been improved very well So using the power lines to transmit control information is very useftil and economical ^^\ With PLC-modem we have a communication medium, the rest is up to you! It may be said that many of the data types (voice, measurement data, etc.) can be transmitted over the power line Below is a short list of some doable things just to spark your imagination • Control lights and other devices • Security systems • Energy control and management • Process control • Environmental control • Low speed PC networks • Heating and air-condition control ' Sprinkler/ watering systems • Connect your whole home to Internet gateway • Help for elderly and disabled people • Chat system for whole buildings 578 ' Small info terminals in rooms • Close blinds if sunlight is to strong ' Let your PC control your home • Stage control in home theaters It may be said that many of data types (voice, control signal, measurement data, etc ) can be transmitted over * the powerline ^^\ A striking demonstration is that we have just implemented a thermometer interfaced with the powerlines and a data collection and control system in real-time also interfaced with the powerlines Experiment To measure and control temperature, the designed system is composed of four parts: a digital thermometer, two PLC-modems, carrier detector and reader and control unit, as shown in Figure The control unit can be set in other side, near the sensor This system has operated properly and indicated satisfactory results The operation of the system can be described as follows At first, the temperature to be measured is collected by thermosensor (LM35D) and as a result, we have a corresponding voltage signal Then the voltage signal is sent to an analog-digital converter (ADC), the 2003 The Asian Conference on Power System Protection ADC in use is ADC3162 from Intersil (USA) Here, the voltage signal is converted to digital signal in accordance with the transmitter, which receives temperature information in the form of digital signals, processes and sends them to PLC tnodem The transmitter is built from an AT89C2051 microcontroller supplied by Atmel Corporation, and we must write software to drive our system and load it to the microcontroller Collecting Mini-Logger and Decision Unit Unit power supply and a V power supply for the microcontroller digital interface It is interfaced to the powerline by an external driver, and a transformer (see Figure 2) Its data transmission rate is 120-2400 bps and its carrier frequency is 132.45 kHz PLC ^B PLC Modem "' r i : t F 1 "1 : Inter Timer Fig Power Line t ^PLC Modem Fig.l Carrier Detector and Reader 220V BBBB IT" Controller Unit The block-diagram of the control system and data c o l l e c t i o n in real-t.ime The PLC modem is interfaced with the power line so that the data could be transmitted over the powerlines by a carrier wave So at any point on the power line, we can also receive the temperature information To carry out that, we will design a PLC modem to connect with the powerlines at the point where we need to collect the temperature Then the information received from PLC modem is sent to the carry detector and reader Here,- the information on temperature is read and converted into digital signal, and processed in order to be displayed on a 7-segment LED or LCD display In this block, we have used an AT89C2051 microcontroller as a central processing unit Certainly software is needed to link and drive the whole system So we can read the temperature in a remote place from the thermo sensor without having to go there or calling for help The main part of the system is a PLC-modem, which is designed and moimted on the PCB with the size of 45 x 58 mm^ This modem is a half duplex asynchronous FSK-modem designed for home automation communication on the domestic electric mains, which complies with the EN 50065-1 CENELEC standard It mainly operates from a 10 V The interconnection of PLC-modem with power I ines The modem consists of two main parts: TRANSMTTTING SECTION: The transmit mode is set when x/Tx = 0, if x/Tx is held at I longer than a second, then the device switches automatically in the Rx mode A new activation of the Tx mode requires x/Tx to be returned to for a minimum 2-microsecond period before being set to The Transinit Data (TxD) enter asynchronously the FSK modulator with a nominal intra-message data rate of 2400 bps The basic transmit frequencies are: -f(TxD=0)= 133.05 kHz -f(TxD=l)= 131.85 kHz These frequencies are synthesized from a 11.0592MHz crystal oscillator; their precision is the same as the crystal one's (100 ppm) The modulated signal that coming out of the FSK modulator is filtered by a switched capacitor band-pass filter (Tx band-pass) in order to limit the output spectrum and to reduce the level of harmonic components The final stage of the Tx path consists of an operational amplifier, which needs a feedback signal (FBS) from the power amplifier In Tx mode the Receive Data (RxD) signal is set to RECEIVING SECTION: The receiving section is active when x/Tx = The Rx signal is applied and filtered by a band-pass switched capacitor filter (Rx band-pass) centered on the carrier frequency and whose bandwidth is around 12 kHz The Rx filter output is amplified by a 20 dB gain 579 9™ The Chinese Conference on Power System P r o t e c t i o n stage, which provides symmetrical limitations for large voltage The resulting signal is down-converted by a mixer, which receives a local oscillator synthesized by the FSK modulator block Finally an intermediate frequency band-pass filter (IF band-pass) whose central frequency is 5.4 kHz improves the signal to noise ratio before entering the FSK demodulator The coupling of the intermediate frequency filter output (IFO) to the FSK demodulator input (DEMI) is made by an external capacitor C5 (100 nF ±10%, 10 V), which cancels the Rx path offset voltage The RxD output delivers the demodulated signal if the carrier detect ( high level when ) signal is low and is set to = The RxD output can deliver the demodulated signal whatever the level of or 1), if (allowing demodulation on very low receive level, "^V typically) description ' High noise immunity and reliable data communication Inputs/outputs of the PCL-modem is on the left of figure 2, which includes MCLK, WD, x/Tx, , TxD, RxD and RSTO pins From here, these pins can be connected to the thermometer, especially with the microcontroller on the thermometer board The interconnection of PLC-modem with microcontroller 89C2051 is illustrated in Figure The software loaded in the * microcontroller performs the data-exchange between the microcontroller and the modem (0 x/Tx = and TxD = (see Figure 3) 'S Fig Data timing diagram of output signal In addition, there is a time base, which delivers all the internal clocks from crystal oscillators (11.0592 kHz) The crystal is connected between XTALl and XTAL2 pins and need two external capacitors C3 and C4 (22 pF ±10%) for proper operation Some main specifications of PLC modem can be shown as following: • Half-duplex asynchronous 2400 bps FSK modem • Tx carrier frequency synthesized from external crystal • Low distortion Tx signal, • Rx sensitivity better than mVRMS • Carrier detection • Watch-dog input •Reset and master clock outputs for microcontroller • Power amplifier bias current control (high impedance in Rx mode) • Simple and economical application schematics in compatible with CENELEC ENN 50065-1 and FCC specification ' Carrier detect clamping on RxD programmable 580 Fig The i n t e r c o n n e c t i o n o f PLC-modem w i t h microcontroller 89C2051 In the remote side there is the same microcontroller and PLC-modem, but in opposite task The role of these two parts is to detect carrier signals with frequency of 132.45 kHz, to decode and send them to display module The demultiplexing circuit drives big LEDs in display-module The software reads the digital data corresponding to temperature values from Analog-Digital Converter Then the data is processed and converted to 7-segment code to be displayed on the local display module On the other hand, the data is transformed into serial form to be placed on the TxD line (RS-232 Standard) The PLC-modem will receive this code and activate the FSK modulation module and send the data over the power line So the data is transmitted on the domestic power line in carrier wave form (one carrier) All of these tasks are executed by the software having loaded un the local*89C2051 On the other side, the modem will receive the signal on the power line and demodulates into a signal 2003 The Asian Conference on Power System Protection m M i^ ^ ^ ^ ^ ^ m ^ :^ m i^'^ in serial form and place it on RxD line The remote 89C2051 processes the signal, converts to 7-segment code and sends to the remote display module The protocol between the transmitter and the receiver is supported by the x/Tx signal If it is held at "0", then the device switches to the transmit mode In contrast, if it is held at " " , then the device switches to the receive mode operated stably, the temperature data from the sensor is displayed on both the local display unit and the remote display unit Two displays units always show the same value of the temperature Waveforms at the transformers of the PLC-modems are illustrated in Figure In this case, a two-channel oscilloscope is used to capture the data carrier and the 50Hz-signal The results and conclusions Unlike many other communication links, the powerline channel does not represent an additive white Gaussian noise (AWGN) environment It has so many kinds of interferences, e.g colored background noise; narrowband noise; impulsive noise; and etc.Tn addition to interferences, access impedance is one of obstacles ^'^\ Fig.6 The n o i s e on t h e signal waveform on t h e power I ine when c o n m u n i c a t i n g between two PLC-Modem i n t h e presence o f motors in operation To reduce the influence of noise and to increase the rehability of the measuring system, three following solutions have been applied: -The circuit is designed as small as possible to shorter connection line in order to restrict local noise -Raise the amplitude of over poweriine transmitted signal by using a power supply of ± 12V for modem part The remaining parts are powered by a voltage of+5 V -Reduce the width of the band-pass by selecting the core of transformer Tri on Figure and Figure It is very importance to reduce the influence of noise, especially in the beginning stage to put the circuit into operation With the designed boards, the measuring system Fig The waveform at the transformer of PLC-Modem The system described in this paper is only one case to illustrate the transmission of measured temperature data and real-time control data over the powerline With a little modification, we can measure a lot of other parameters, for example, humidity, pressures, etc., and many control system, e.g., alarm system, security system, etc The designed PLC modem is bi-directional so this measuring system uses the same modem for both the remote board and the local board Whether it is used to send or to receive data is decided by the embedded software, which has been loaded in the microcontroller References Klaus Dortcrt: Power Line Communication, Pcnticc Hall PTR 2001 p 43-54 Hcnis David, Dickinson John, et al: PALAS -Powerline as an Alternative Local Access IST-1999-] 1379, 2000 June Scientific Report 2001, University o f Essen, "A Breakthrough Power Line Communication", p 1-2 Germany 2001, Klaus Dortcrt: An Analysis o f the Broadband Noise Sccnano in Powerline Networks Proceedings o f the 15* International Wroclaw Synjposium and Exhibition on Electromagnetic Compatibility June 27-30 Wroclaw Poland ISBN: 83-901999-0^ 581 Data Transmission over the powerlines Ngo Dien Tap, Tran Xuan Tu Faculty of Technology, VNU Hanoi Abstract: The data transmission system is designed and mounted in order to collecting data remotely over the powerlines The data maybe is temperature of environment In this case, modulus in the system are controlled with the microcontroller in the 8051 family to send data from sensors to display-module through interconnection with PLC-modem The proper software is'written to drive the measuring system, especially to read data at the sensors and to send to display-module over the power lines The system described in this report can be modified to measure/collect other parameters of the environment, for example, humidity, pressure, etc., or controlling data, timing even and many type of information L INTRODUCTION Together with the use of the carrier-frequency technology over postal lines around 1920, one began to apply this technology for data traasmission over high-voltage networks or powerlines "' Recently, the under structures of the powerlines have been improved very well So using the power lines to transmit data is very useful and economical '^' With PLC-modem we have a communication medium the rest is up to you! It may be said that many of the data types (voice, measuring data, etc ) can be transmitted over the power line Below is a short list of some doable things just to spark your imagination Control lights and other devices Security systems Energy control and management Process control Environmental control Low speed PC networks Heating and air-condition control Sprinkler/ watering systems Connect your whole home to Internet gateway Help for elderly and disa^jled people Chat system for whole buildings Small info terminals in rooms Qose blinds if sunlight is to strong Let your PC control your home Stage control in home theaters It may be said that many of data types (voice, measuring data, etc ) can be transmitted over the powerline '^' A striking demonstration is that we have just implemented a thermometer interfaced with the powerlines and a data collection and control system in real-time also interfaced with the powerlines 11 EXPERIMENT In thermometer, the designed system is composed of four parts: a digital thermometer, two PLC-modems, and carrier detector and reader as shown in Figure I The operation of the system can be described as following: At first, the temperature to be measured is sensed by themiosensor (LM35D) and as a result, we have a corresponding voltage signal Then the voltage signal is sent to an analog-digital converter (AEXT), the ADC in use is ADC3162 from Intersil (USA) Here, the voltage signal is converted to digital signal in accordance with the transmitter, which receives temperature information in the form of digital signals, processes and sends them to PLC modem The transmitter is built from an AT89C2051 microcontroller supplied by Atmel Corporation, and we must write a program (software) to drive our system and load it to the microcontroller