Team 4 – Cap Bank Neutral Curren Sensor4队–盖银行中性电流传感器

1、ece senior design team 4neutral current sensor for fixed capacitor bank will brewer (pm)jon geurinkjason christoffdan heidfeldmatt madlapril 17, 2008 team advisor dr. bruce mork aep sponsor contact ray hayes, pe2design review outline project management project problem project objective, requirements

2、, & considerations current transformer testing circuit design transmission/communications microcontroller considerations conclusion3project team hours4project schedule5proposed project budget6project budget, estimated expensesece senior design team 04 - neutral current sensor for fixed capacitor

3、 banksparts orderedlab report book, campus book storeposter foam board, office maxnon-metallic enclouser, cooper b-line, 10106-4xfthcpic microcontroller, pic24fj48ga002-i/sp-nd, digikeyxbee radio starter kit, xb24-dkssupercaps .22 farad, power star, 283-2786-nd, digikeyexplorer 16 starter kit, micro

4、chipvoltage regulators, tps75333qpwp/433qpwpg4, texas insturments1 farad supercaps, 27m9810, newark1.5 farad supercaps, 27m9811100 uh inductor, 63k32483.3v zener diode, 42k28433.3v voltage regulator, 77c0978mosfet driver, 30m95247.5v zener diode, 42k286310v zener diode, 31c448622 uh inductor, 62k049

5、9 photovoltaic solid state relay, lh1262cb, mouserphotovoltaic solid state relay, vo1263aactr3.3 a mosfet, dn2625k6-gshippingdc power plugs, 1710-0725, mouserdc power jack, 163-5012modular jack, 649-69255-00ilfzbee pro, 888-xbp24-awi-001low impedance capacitor, 647-upw1a682mhd6shippingswitching rela

6、ysshipping poster foam board, office maxtotalquantity111211016446622334 223 22221 3 2 total cost$37.49$16.99$109.29$11.16$99.00$40.50deptfree$12.72$13.52$12.54$2.83$8.75$16.30$0.79$48.00$2.36 $7.92$8.46$4.92$17.89$1.74$0.88$1.80$64.00$1.92$36.54$11.85$53.16 $13.98$657.307project problem aep has 12,0

7、00 capacitor banks in the field 45% of those are fixed cap banks while the remain banks are switched fixed cap banks dont contain the hardware to self correct from faults8project problem cont. unbalanced 3-phase transmission lines do not have zero-sum current when one or more fuses fail a cap bank i

8、s no longer balanced and current flows through the neutral line on average 30% of all cap banks in north america are out of service at any one time9project problem cont. aeps approximate annual inspection cost may be $200 per year per capacitor bank. energy is worth about $50/mwhr a single failed ph

9、ase on aeps smallest 450kvar cap bank causes an estimated 50mwhr of additional power loss on a distribution feeder per year. this energy cannot be billed to anyone, so it is a direct loss to company profits. this problem is country-wide.10project problem cont. additional power produced to meet deman

10、ds increases the c02 gases from aeps coal burning power plants. approximately 50 additional tons of co2 gases are released into the atmosphere11line losses efficiency decreases on the lines due to power factor change when a capacitor fails. assuming an average 100 amps real current flow ( in phase w

11、ith voltage ) and a power factor of 0.98 means about 20 amp reactive flow, so rms current = 102 amps. 100 amps20 ampscos-1(.98) = 11.4783100*tan(11.4783) = 20.3058 arms = 100/0.98 = 102.0408 a12line losses cont. loss of a cap phase adds 20 amps to the reactive current, so rms increases to 107.7 amps

12、. rms w/loss =100 amps40 ampsa703.107401002213line losses cont. assuming a line resistance of 5 ohms over one year, thats a loss of 51.312mwhr.at $50/mwhr, losses total about $2566 per phase per year.kwrialno061.525*)0408.102(2min2kwrilossw999.575*)703.107(2/2kwpowerloss939. 5061.52999.5714project o

13、bjective to develop an inexpensive, pole mounted sensor that detects current flow through the ground/neutral line to discover improper operation communications notifying operators of faulty e q uipment and providing opportunities for future distribution infrastructure data collection a universal des

14、ign to be placed throughout the distribution network15ct connection to neutraldiagrams from aeps distribution standards for capacitor banks16design re q uirementsthe main 3 objectives:1. harvest power, self powering design2. wireless communication3. packaged in weatherproof enclosure/able to withsta

15、nd the elementsadditional re q uirements: protection from common surges transmit amplitude of measured current use split core ct (weatherproof), not clamp-on or solid17project tasks will project management, design layout jon communications, switching circuitry jason circuit design and powering matt

16、ct testing and harvesting dan microcontroller coding, ct testing18current transformer overview preliminary design with 100:5 split-core ct currently using 200:5a ratio 0.3 accuracy class gec durham industries 4 a-t primary to run circuit19ct testing testing the ct with oc/sc tests wasrequired to get

17、 its flux-current loop and to develop its equivalent circuit model this information is used to model the ct in the computer using matlab we can then determine when the ct core will saturate and how long it will take to charge our super capacitors20ct tests / figuresshort circuit test675 w 120v21ct t

18、ests / figuresopen circuit test675 w 120v22preliminary ct tests / figurescurrent loop curve flex-core current transformer100:5 a cat 604-101rf 1.33 acc class +/- 5% 1va50-400 hz 600 v insclass 10kv biltesting using open circuit test from 0.5 amps to rated, 5 amps, in 0.5 amps intervals23current tran

19、sformer new currently using 200:5 amp ratio 0.3 accuracy class, gec durham industries 4 amps was found to be the minimum to charge the super caps to 5.6v when 20a from a failedphase flows through primary, thesecondary sees 39.8v which isregulated by the zener bridgect tests / figuresopen circuit tes

20、t resultinstrument current transformer200:5 a cat 100p-3accuracy class .360 hz n.s.v. 600 vclass 10kv bil25waveforms to ctct waveform during charging modect voltage waveform during active/measuring mode26preliminary circuit design27final circuit design28surge protection & rectifier surge protect

21、ion consists of two 10 volt, 10 watt zener diodes back to back on the ct input wires. chip rectifier is rated for 1.5 a continuous, up to 50 a surge, 280 vrms and up to 400 v reverse current protection.29super capacitors circuit employs four 0.47 farad super capacitors. charge to 5.6 volts before di

22、scharging. chosen for high duty cycle capabilities and ability to maintain optimum voltage level longer. 30charging super capacitors these calculations assume no losses under constant conditions. ideally, for a total of 1.88 farad super caps to charge from 0 to 5.6 vdc, at 1 amps primary and 0.025 a

23、mps secondary, it will take about 421.12 seconds for a full charge. based on calculations for linear capacitorssec12.421025. 088. 1*6 . 5ampfaradvdc31charging super capacitors cont. a faulted capacitor condition yields approximately 20 amps primary, the 0.5 amps secondary will charge the super caps

24、in about 21.056 seconds.-based on calculations for linear capacitorssec056.215 . 088. 1*6 . 5ampfaradvdc32measuring resistor & filter resistor is 3.3 ohm, 10 watt with a 5% tolerance. need to keep voltage across less then 3.3 vdc smoothing capacitor flattens voltage signal and allows for more pr

25、ecise calculations.33voltage regulator voltage regulator is a lm2576. capable of 3 a continuous output. produces a 3.3 vdc output from 4.7-6 vdc34switching concepts - preliminary fully relay logic and switching easy to use and control high power consumption fully transistor logic and switching some

26、power savings more complications resistive losses35switching concepts - preliminary mosfets minimal losses power savings more complicated an opto-iso or high-side driver re q uired for controlling a nc depletion mode mosfet36switching concepts - preliminary power consumption of opto-iso turned out t

27、o be more than small relay coil: opto-iso= 41.7ma 3.3vdc = 138mw small relay=33.333ma 3.3v=100mw37switching concepts - final latching relay + 2 mosfets mosfets require very little power relay only requires power to change states reduced part count less complicated very low losses38latching relay 4.5

28、 volt, 2 coil, dpdt 2a contact rating relay ideal for project: switch on 5.6v, switch off by 4.4v relay coil consumes more power than non-latching but it only operates momentarily works directly from super capacitors39switching circuitto super capacitorscharging:from ct40switching circuitfrom super

29、capacitorstransition:41switching circuitfrom super capacitorsactive / testing:to vregfrom ct42 radio and micro powered up microcontroller calculates current from measuring resistor microcontroller sends data out radio after 15 sec or a confirmation signal, micro sends signal to mosfet circuit return

30、s to charging mode active / testing mode43switching circuitfrom super capacitorstransition:from mirco44voltage dividers originally, we wanted very high resistance to keep losses very small final design should contain smaller resistance to prevent accidental switching due to transient currents45radio

31、xbee/ xbee pro module- low power consumption - self contained module- range up to 1 mile with x bee pro- multiple baud rates and options- mesh networking- compatibility with ami networks- z igbee compatibility re q uested by sponsor46 pic24fj48ga002-i/sp 10 bit a/d uart communication 20ma 3.3v, 16mipsmicrocontroller47microcontroller - programming48development