DCSwitchcomponents.docx

1、DCSwitchcomponentsDRAFTNEPTUNE Circuit Breaker ComponentsDenise Dennis, Circuit Breaker GroupApril, 2002ABSTRACTThe NEPTUNE circuit breaker is designed for 10kV and 10A dc system. The components of the circuit breaker include a 2-10F capacitor, 2 1k resistors and 3-4 vacuum switches. The task at han

2、d is to locate components that meet the desired specifications. At least two sources are located for each component, and comparisons of the different products are presented. In some instances tentative prices are obtained. At this point recommendations are not made, as certain aspects of the design

3、are not yet finalized.Beyond the components of the circuit breaker, diodes and surge arresters are needed in each node. These important components are also addressed in this report. INTRODUCTIONThe NEPTUNE power system is unique in several respects. First, the source voltage is 10kV direct current,

4、which is uncommon in utility systems. Second, the operating current is larger than most industrial high voltage dc applications. This combination creates a challenge in finding off-the-shelve components.The circuit breaker is designed to be immersed in standard transformer oil to reduce the size of

5、the various components and to provide a heat exchange medium. The components must be capable of withstanding the generated heat for the lifespan of the project. A figure of the circuit breaker is shown below, with all switches open.Figure 1. Circuit BreakerThe work done here is composed of three ste

6、ps:1. To find if the components with the desired ratings exist. 2. If available, the size and durability of the components are examined3. If all satisfactory, the cost is consideredCircuit breaker componentsCAPACITORThe initial investigation indicates that the bypass capacitor may have a valued betw

7、een 2F and 10F. The physical size of a capacitor is determined largely by its voltage rating as well as its capacitance. Since the voltage is fixed (10 kV), and the current is determined by the power flow, the capacitance is the determining factor for the physical size. 10F capacitors are rather lar

8、ge, (up to 14 inches longest dimension), the 1F and 5F capacitors are considerably smaller (about 6 inches longest dimension). We are currently using ATP simulations to select the smallest capacitance that limits the system transients to a tolerable level while preventing restrikes when the breaker

9、is opening. A smaller capacitor could significantly decrease the overall size of the circuit breaker as demonstrated below, but the exact size is to be determined after the ATP simulations are completed. Three sources for capacitors are located, HiVolt Corporation, Plastic Capacitors Inc and High En

10、ergy Corporation. These three companies manufacture similar products. Below is a summary of their capacitors specifications and dimensions. Figures 1-3 show the general dimensions, and Tables 1-4 gives the specifications. Table 5 shows a comparison between these products. Information about the compa

11、nies is included in the appendix, along with datasheets.Hi Volt CapacitorsConstruction: Dielectric material: polyester/polypropylene film and capacitor tissue; Case: hermetically sealed tinplate, rolled-seamed;Internal construction designed to prevent movement when cap is subjected to mechanical sho

12、ck or vibration; External connections via ceramic terminals; Enamel finishImpregnant: mineral oilTolerance: 10%Temperature: -55 to 85CApplications: DC applications such as filters, bypass, coupling of low frequnecy audio. Also Pulse-Forming networks, energy storage, High voltage smoothing, oscillato

13、r circuits, arc and spark suppressionNotes: Vtest: 2Vrated for 1 minuteFigure 1. Hi-Volt Capacitor Diagram10kV DC working voltageCapacitance in FABCDEPMR 100-5030.055880484060PMR 100-5040.514080484060PMR 100-105116085674060PMR 100-20521401301005060PMR 100-60563501301005060PMR 100-156153501801807560D

14、imensions are in mmTable 1. Hi Volt Capacitors: Models and DimensionsPlastic CapacitorsConstruction: Similar to MIL-C-19978; not QPL listed; military can, hermeticallysealed; High voltage terminals of the solder-seal varietyeliminates gasket failure, common fault in some cap types as gaskets age; in

15、ternal individual capacitor elements are wound using extended foil design; elements connected to brass terminal stud with heavy copper braid.Impregnant: mineral oil, 145 C flash pointTemperature: -55 to 85CTolerance: 10%Applications: energy storage/discharge of high current at low repetition rates P

16、ulse x-ray, photoflash, laser pumping, pulse-forming networks, High intensity strobeNotes: Capable of handling a dead-short discharge, though not recommended.Figure 2: Plastic Capacitors Diagram10KVDCCapacitance in FABCDELK100-104ND0.13.751.753.7522.125LK100-504ND 0.53.751.756.2522.125LK100-504ZND 0

17、.53.753.18754.2522.125LK100-105ND 13.752.25822.125LK100-105YND 13.753.1875622.125LK100-105ZND 14.56253.75522.125LK100-205ND 24.56253.757.522.125LK100-405ND 4849.254.52.125LK100-405YND 44.56253.7511.522.125LK100-605YND 67.3755.625932.125LK100-805YND 87.3755.6259.7532.125LK100-106ND 1013.54.125116.752

18、.125LK100-106YND 107.3755.62512.12532.125LK100-206ND 2013.56.125126.752.125Dimensions are in inchesTable 2. Plastic Capacitors: Models and DimensionsHigh Energy CorporationConstruction: paper/polypropylene dielectric, plated steel case with optional epoxy finish, or mild steel with epoxy finish.Impr

19、egnant: environmentally compatible impregnantTemperature: -40 to 85CTolerance: 10%Applications: Primarily used as filters in output of high DC power supplies. Can be used in broadcast and radar power supplies, and other high voltage DC supplies. Figure 3. High Energy Capacitor DiagramsDrawn Rectangu

20、larsWelded CaseA11.75W148B1.192.5W24.1313.5C1.253.75W35.1313.5D1.753.75W46.2513.5E2.253.75W5714F2.53.75G3.193.75K2.844.56J3.754.56Sizes are in inchesTable 3. High Energy Corp Capacitor Dimensions C-F VDC base figure ht B TCC692110,000 G25.502.002.00CC693210,000 J27.002.002.00LC322510,000 W1310.003.0

21、05.00LC3301010,000 W2310.003.005.00Dimensions are in mmTable 4. High Energy Corp: Capacitors and DimensionsPlastic CapacitorsHi Volt CorpHigh Energy CorpConstructionMilitary can, hermetically sealed; high voltage terminals of solder-seal varietyeliminates gasket failure; internal individual capacito

22、r elements wound using extended foil design; elements connected to brass terminal stud with copper braid.Dielectric material: polyester/polypropylene film and capacitor tissue; hermetically sealed tinplate case, rolled-seamed;Internal construction designed to prevent movement when cap is subjected t

23、o mechanical shock or vibration;External connections via ceramic terminalsEnamel finishpaper/polypropylene dielectric, plated steel case with optional epoxy finish, or mild steel with epoxy finish.Impregnantmineral oil, 145 C flash point mineral oilenvironmentally compatible impregnantTemperature -5

24、5 to 85C-55 to 85C-40 to 85CTolerances10%10%10%ApplicationsEnergy storage/discharge of high current at low repetition ratesPulse x-ray, photoflash, laser pumping, pulse-forming networks,High intensity strobeDC applications such as filters, bypass, coupling of low frequency audio. Also Pulse-Forming

25、networks, energy storage, high voltage smoothing, oscillator circuits, arc and spark suppressionPrimarily used as filters in output of high DC power supplies. Can be used in broadcast and radar power supplies, and other high voltage DC supplies. NotesCapable of handling a dead-short discharge 2Vrate

26、d for 1 minuteTable 5. Capacitor ComparisonFigure 4. Volume vs. Capacitance. The linear relationship between volume and capacitance is apparent. The circuit breaker could be significantly smaller if a lower capacitance is used.The chart in Figure 4 shows the capacitor volume vs. its capacitance. The

27、 relationship demonstrates that the size is linearly reduced when the capacitance is reduced.The cost of the capacitors ranges from around $150 for the 1F to close to $500 for the 10F version. RESistorsTwo resistors are required for the circuit breaker (see Figure 1. R1 and R2). One is for the soft-

28、closing of the circuit breaker. The second is for the dissipation of the stored energy of the capacitor after the breaker is opened. The task here is to find resistors which can withstand the power and energy for each of these operations. Three sources were located, Kanthal Globar, Tepro Electrotech

29、nik, and Nicrom Electronic. Company information and datasheets are located in the appendix.Soft close resistorIn the initial design of the breaker, the R1=1k resistor is selected for the soft starting process. During the closing sequence of the breaker, the resistance is present in the circuit for t

30、=1 second. In reality this time will probably be shorter, but t=1 second is used for power and energy calculations. The power (P) and energy (E) requirements of the resistor are calculated as follows:The current of the breaker is assumed to be 1A. This is because we are assuming that when the breaker is closing, it excites only one section with one node. Nicrom Electronic manufactures a resistor appropriate for our purposes. This is the 500.100