TECHNICAL PAPER PRESENTATION

Transcription

1 1 W E L C O M E T O A C O M E T TECHNICAL PAPER PRESENTATION

2 2 INSULATION AND SWITCHING IN ENVIRONMENTALLY FRIENDLY GASES BY JAVIER MANTILLA

3 3 A B O U T T H E A U T H O R BRIEF BIO JAVIER MANTILLA PRINCIPAL ENGINEER ABB SWITZERLAND Principal Engineer at ABB Switzerland Holds an M.Sc. in Mechatronics and an M.Sc. in Power Engineering from the RWTH Aachen University Ten years experience in high voltage circuit breaker R&D with ABB Switzerland. Main focus on environmentally friendly technologies. Expert in CIGRE WG A3.26 and WG A3.32 Senior Member of IEEE

4 4 PILOT INSTALLATION EWZ ZÜRICH First High-Voltage GIS (170 kv / 40 ka) with alternative Insulation- and Switching gas AirPlus HV and MV equipment with AirPlus, Flawless operation since August 2015 LEARN MORE

5 Alternative Insulation and Switching Gases 5 Overview from the «Current Zero Club» for CIGRE SC A3 (August 2016) AirPlus C5 Fluoroketones. Used as an additive to a background gas. Air for insulation, CO2 for switching. Commercially available under Novec 5110 from 3M g3 C4 Nitriles. Used as an additive to a background gas. Commercially available under Novec 4710 from 3M

6 6 Insulation- and Switching gases for High-Voltage switchgear General aspects for the assessment of Insulation gases Traditional Technical functionality Size / Footprint Capital expenditure Reliability and maintenance effort Future Environmental impact / Global Warming Potential (GWP) Operational costs due to regulations Different regulations in different countries / regions Environmental Impact Functionality

7 7 Scalability Application of alternative gases in the whole portfolio Basic Aspects lthe insulation performance of alternative gases for AC and impulse stresses is relative simple scalable Especially the circuit breaker, but also disconnectors and grounding switches have to be investigated experimentally due to the complexity of the switching physics Knowledge from decades of research with SF6 as Insulation- and switching-medium have to be assessed for validity with respect to the new gas mixture Un * In Product

8 8 Insulation- and Switching gases for High-Voltage switchgear ABB s AirPlus Properties C5-Fluorketones have a boiling-point of 26.5 C and have to be mixed with a non-condensing buffer gas therefore a mixture with N2 or CO2 (Circuit Breaker) is necessary Additional admixture of O2 to avoid soot formation and toxic decomposition products Insulation- and switching performance close to SF6 today achievable for minimum ambient temperatures of -5 C.. +5 C by using only slightly modified SF6 - products Typical mixing ratios in HV - applications: C5-Ketones O2 N2 or CO2 4-7% 8-14% 79-88% Typical minimum operating pressure around 6-7 bar N 2 or CO 2 O 2 C 5 F 10 O

9 9 Example for new optimization areas Thermodynamic Poynting Effect [1, 2] Dewpoint shift Tests in climate chamber to confirm dewpoint Buffer gas influences C5-vapor, shift of dewpoint Effect strongly depends on gas properties AirPlus : Shift of dewpoint around -0.7 C / bar -> around % better insulation performance [1] R. Krishna and C. B. Panchal, Condensation of a binary vapour mixture in the presence of an inert gas, Chem. Eng. Sci., vol. 32, no. 7, pp , 1977 [2] C. C. M. Luijten and M. E. H. van Dongen, Nucleation at high pressure. I. Theoretical considerations, J. Chem. Phys., vol. 111, no. 18, pp , Nov. 1999

10 10 Decomposition products after extreme arcing stress (circuit breaker) G I S - B r e a k e r k V / 5 0 k A a f t e r 8 x T a, 3. 1 M J a c c u m u l a t e d a r c i n g e n e r g y CONCLUSION 1 Gas analysis (EMPA, Switzerland) C5-FK filling: 5.7 % at 7 bar, V = 380 Litres -> 6.8 Mol / 400 mbar (partial pressure)

11 11 AirPlus Consumption Rate From numerous development tests The measured decomposition products are not critical Existing safety measures as known for SF6 are far on the safe side when handling AirPlus Decomposition rates of 0.14 mol/mj (T10/T30) up to 0.5 mol/mj (T100a) have been measured The «Aging» of the insulation gas by decomposition of the C5- Fluorketones is not problematic for typical GIS breaker tank sizes By correct dimensioning, the lifetime of the circuit breaker stays determined by nozzle- and contact erosion

12 12 Switching in AirPlus Introduction General topics High-Voltage circuit breakers have to handle a large number of switching gases safely (IEC ) Today, the dominant technologies for SF6 - HV-interrupters are self blast devices and for larger power the thermally supported puffer breakers All investigations have been performed with circuit breakers, which originally were developed for SF6 Self blast interrupters as well as puffer unit with ratings up to 300 kv /50 ka were tested No change of operating mechanism / linkage / contact speed Only modifications were the new gas mixture, slightly increased filling pressure and changes in the nozzle contour and flow cross sections of the arc extinction system

13 13 Switching performance 1/3 Smaller currents -> capacitive/inductive/t10/t30/phase opposition Development tests with AirPlus Unmodified SF6 Breaker: Problems at long arcing times (too low no-load pressure), but already excellent interruption performance for shorter arcing times Modification of the flow cross section, adaptation to the changed thermodynamic properties (density, sound velocity) No modification of linkage and operating mechanism Capacitive and inductive switching performance finally as good as with SF6 (e.g. similar low chopping number)

14 14 Switching performance 2/3 Short line faults (SLF, «thermal interruption») Development tests with AirPlus With slightly modified nozzle contours around 80% of the thermal interruption performance of the SF6-version can be achieved Therefore the di/dt has to be down rated by 20%, if a short-linefault interruption capability is needed «Decision time» for thermal interruption around 1 ms after current zero, similar to SF6 -> SLF90 stays most critical case, same as with SF6 Future improvements e.g. by providing higher blow pressure

15 15 Switching performance 3/3 High short circuit currents T60 T100 a/s Development tests with AirPlus General challenge for T100a - interruption: High temperature and pressure, especially in self blast devices With AirPlus the pressure build-up at long arcing times is lower than with SF6, which is beneficial in this switching case So far no problems by breakdowns to the tank due to hot exhaust gases. Nozzle contour and electric field in the arcing region, especially in the so called diffusor area, has to be adapted

16 16 Summary Conclusion and outlook Circuit Breakers with AirPlus reach the performance of the SF6- version in most of the switching cases For short-line-faults the maximum di/dt has to be downrated by 20% versus the SF6 base version Only minor modifications in the nozzle system in the breaker Limitation today to indoor / warm climate installations Technology is scalable for higher short circuit currents and voltage ratings Full compatibility for the unlikely case, that SF6 shall be used, only exchange of the HV interrupter necessary in this case Standard products planned for 2020 Project-based installations possible on request