TWENTIES WORKSHOP, EWEA 2012 Unveiling the future energy system: full scale demonstrations to reach 2020 targets 17th April 2012
Session 2 Technological challenges to cope with in TWENTIES field tests 17. April 2012 WORKSHOP EWEA 2012 www.twenties-project.eu 2
DC-breaker prototype: challenges and advances Wolfgang Grieshaber, Alstom Grid 17. April 2012 WORKSHOP EWEA 2012 www.twenties-project.eu 3
DC-breaker prototype: challenges and advances 1. Differences between AC and DC current interruption 2. DC breaker options Choosing the breaker concept. 3. Key Performance Indicators (KPI) Dielectric withstand. Short Time Withstand Current. Reduction of electromagnetic forces. Duration of current interruption. 4. Demonstrator duties Selecting the duties to demonstrate. 5. Current interruption & let-through current 6. Advances 4
1 - Fault in AC loop 200 Current (ka) 50 Hz, 80 ka rms Opportunities for current interruption 100 0 Magnetic energy in the system 0 10 20 30 40 50 60 70 80 90 100 Time (ms) Attempt to interrupt when I 0 rapid variation of magnetic flux overvoltage Current interruption succeeds when magnetic energy 0
1 - Fault clearance in DC loop Fault inception current rises Magnetic energy in network increases Breaker inserts element limiting the over voltage & absorbing energy Energy transferred to energy management system Limitation of overvoltage + absorption of magnetic energy = prerequisites for DC current interruption
2 - DC breaker options MRTB Solid State Switch CB Fast switch Solid State Circuit Breaker without auxiliary circuit arc / power electron. arc chamber arc chamber + power electronics power electronics power electronics development needed none synchronous switch, capacitor load circuit new concept new concept smallest break time 27ms to 41ms 19ms for contact separation + 8ms to 22ms arcing time 27ms 19ms for contact separation + 8ms arcing time ~ 2ms ~0.1ms on-state losses <1 mohm <1 mohm <100 mohm ~1 Ohm max break current ~4 ka (possibly 8kA) 5 ka possibly 10kA ~10 ka ~10 ka complexity low medium high high
3 - Key Performance Indicators KPI were defined at beginning of Twenties Project (early 2010) No standard available! 1. Dielectric withstand in open state Lightning Impulse Withstand (indicator = U peak / 650kV) Target: indicator > 1 2. Current above 1500A (1 min.) in closed state Indicator = current / 3000A Target: indicator > 1 3. What harm can be prevented (force reduction) Indicator = (peak prospective current / peak interrupted current)² Target: indicator > (1.1)² 4. How fast is the interruption Comparison to AC breaker ; Indicator = 40ms / interruption time Target: indicator > 1 Prospective current: current without DC-breaker action. Later analysis led to extend the duties to be tested!
4 - Demonstrator duties All breaker duties Open state Without power With power Normal condition DC fault condition Dielectric withstand (BIL, SIL, DC) Closing Let-through current Let-through current Load switching Closed state DC dielectric withstand to ground Let-through current Close on fault Opening On idle line or cable: no current, no TRV no problem Load switching Terminal fault (highest rate of rise of current, highest prospective fault current) Without power: At least one breaker terminal is connected to a network that has only stored energy (trapped charges) but neither power source nor load nor network faults. Normal condition : The breaker is connected to power sources (and loads), but no faults. DC fault condition : a breaker has on one side a power source and on the other side a network fault.
4 - Demonstrator duties Selection for Twenties Open state Closed state Without power Dielectric withstand (BIL, SIL, DC) Normal condition With power DC dielectric withstand to ground Let-through current (must withstand, but not to interrupt) DC fault condition Opening Load switching Terminal fault (highest rate of rise of current, highest prospective fault current) Power tests Let-through current Wave forms as a function of time. The 4 wave forms are individual tests. 1. 1500Adc until dt/dt<1 C/hour 2. 3000Adc for 1 minute 3. 5kA sin(2π 50Hz t) for 10ms 4. 10kA sin(2π 313Hz t) for 1.6ms No standard available Interrupted current had to be described in simple manner
5 - Current interruption Specification of breaker performance: Transient Interruption Voltage ( TIV < Network insulation level) Prospective current 3 or 5 parameter envelope function (similar to TRV in IEC 62271-100) Prospective current I load +I fault Rate of rise of prospective current Prospective current = no breaker action I load 0 t 0 Instant of fault inception t 0 + t 3 time
5 - Current interruption Specification of breaker performance: Transient Interruption Voltage ( TIV < Network insulation level) Prospective current 3 or 5 parameter envelope function (similar to TRV in IEC 62271-100) Energy to absorb Prospective current I load +I fault I load Breaking of prospective current Energy absorption Current zero 0 t 0 t 0 + t 3 time
5 - Interruption and let-through Target values to be exceeded Prospective current 1.5kA, 7.5kA, 0.6ms Transient Interruption Voltage 180kV Energy to absorb Prospective current 7.5kA 1.5kA Black line = performance target Depends on test circuit in the 100kJ to 1MJ range Let-through current 10kA, 1.6ms 5kA, 10 ms 3kA, 60 s 1.5kA, infinitely 0 0 0.6ms Let-through 10 ka current 5 ka 3 ka 1.5 ka time 0 1.6 ms 10 ms 60 s time
6 Advances & outlook Breaker is designed Patent application in progress. Subassembly qualification tests started Temperature rise tests target in reach. Dielectric tests on subcomponents target in reach. Test circuit Circuit is designed. Prospective current range will be verified by test. Power test of demonstrator Scheduled for end of 2012. RtE and independent observer to witness the tests.
Thanks for your attention! Any question? www.alstom.com/grid 15
Thank you for your attention Questions to DEMO3 DCCB? www.alstom.com/grid