Superconducting Fault Current Limiters

Transcription

1 Superconducting Fault Current Limiters First Friday Club 1 st April 2011 Gerhard Novak UK Technical Manager Joachim Bock Managing Director, Nexans Superconductors 1

2 Smart Grid Solutions 2

3 Fault current What is a fault current? A fault current is the current which flows during a short circuit. At home we have fuses or magnetic circuit breakers to switch off in case of a short circuit. In a substation the situation is the same only the current is much higher - thousands of ampere. 3

4 Fault current Such a fault current is dangerous for two reasons: Magnetic forces: during a short circuit enormous magnetic forces are created which try to move electric conductors away from each other. Thermal energy: The high current during a short circuit heats up all electric conductors in fractions of a second and can lead to a fire. 4

5 Power Networks in the UK Until now, operators of public and industrial electrical networks could only have limited protection from high short circuit currents, either by the use of complicated equipment or overrated components Development of distributed generation, such as wind power, and the ever increasing demands for power have pushed medium voltage power grids to their maximum operating limits Short circuits can occur more often and are more likely to cause high, uncontrollable fault currents which can lead to defects in the electrical systems and to power failures 5

6 Do we need fault current limiters? If we could look into the future we could plan for every substation and switchgear to cope with the maximum fault current the network will ever deliver But we have to work with our existing network. In the UK our power network is facing new challenges, concepts which have applied for the last 40 years are becoming outdated Distributed generation such as Co-generation Wind farms Solar farms Stronger linkage/coupling AC transmission DC transmission Smart grids : consumer = producer 6

7 Do we need fault current limiters? The traditional load flow will change as we have sustainable energy sources like wind farms included in our network. Some of our substations will not have been designed for the maximum short circuit currents which may occur in this new situation. 7

8 Do we need fault current limiters? Solutions: 1. Upgrade the substation to cope with the new maximum short circuit current from mechanical and thermal point of view. This may cost several million. 2. Or, add a device which reduces the short circuit current to a value which our existing substations can cope with A Fault Current Limiter 8

9 What do we expect from a fault current limiter normal operation short-circuit recovery First peak: Stress on the system current Follow current: Thermal load AND Detection time 9

10 Where do we need fault current limiters? The typical use is in applications such as: Busbar coupling In-line (secondary side of transformer) House load protection in power plants (a coal power plant needs 8% of the power created for auxiliary systems) High voltage Transformer feeder FCL Medium voltage FCL Busbar coupler 10

11 Fault Current Limiters What are the available technologies? Pyrotechnic FCL (ABB Is-limiter) Solid State Fault Current Limiter SSFCL Superconductive Fault Current Limiters (SFCL) Resistive type SFCL Saturated core type SFCL 11

12 Pyrotechnic FCL (ABB Is-limiter) Existed for 50 years but usage is not widespread as it has several drawbacks: - Non fail save - Safety concerns (explosion) - No automatic recovery (time!) + Can be disabled by software 12

13 Solid State Fault Current Limiter SSFCL Still at R&D stage - High loss also at standby (high operation cost) - Needs external trigger (Reliability?) - The control hardware is responsible for the function - Complex system - Cost 13

14 Superconductive Fault Current Limiters The two most common SFCL systems are Saturated core type Resistive Type SFCL Both have been subject to tests on electrical networks 14

15 Superconductive Fault Current Limiters Saturated Core Type Drawbacks and advantages: - Weight - DC operation of superconductor - Low limitation level (approx. 20%) of 1 st peak - Large size - Oil cooled - Losses and limiting effect + Immediate recovery + Intrinsically safe + No need to disconnect This system doesn t use the special properties a superconductive material has and theoretically it could be built without using superconductive conductors. 15

16 Superconductive Fault Current Limiters Resistive Type SFCL Drawbacks and advantages: + Intrinsically safe + High limitation level (up to 80%) + Compact size + Resistive limiting action - Recovery time 16

17 Nexans Super Conductors HTS system provider Office building, and assembly hall Production, workshop, and test area 17

18 Nexans Super Conductors Materials Components - Systems ZF Frankfurt Höchst and GBA Knapsack From R&D to systems October 1987 Corporate Research & Technology January 1995 HOECHST RESEARCH & TECHNOLOGY January 1998 May 1998 chemistry physics material sc. electrical eng. mechanical eng. Alcatel High Temperature Superconductors Nexans SuperConductors October 1999 October

19 HTS material and conductor types for industrial applications YBa 2 Cu 3 O 7-x buffer2 buffer1 substrate Bi-2212/ Bi-2223 tape 1 st generation Y-123 cc-tape 2 nd generation Bi-2212 bulk Y-123 bulk 19

20 From powder to HTS-components Melt Cast Process Nexans proprietary process Fault Current Limiter Components BSCCO-2212 tubes BiSrCaCuO powder 20

21 Basic design of the FCL Connection for adaptation Current in parallel Voltage in series component module set-up of a phase accommodation in a cryostat Current and voltage adjustable by modular construction Fault Current Limiter connected in series with the grid 21

22 Realisation of the FCL Nexans capabilities encompass the full manufacturing and installation process 22

23 Project 1: Field test ASL, Newcastle ENW, Bamber Bridge Live on grid to

24 Project 2: Vattenfall Brown Coal Power Plant - First FCL worldwide in a power plant Installation 10/ 2009 Commissioning End of field-test 12/ 2010 Second field test planned with new superconductor (tape) Significant savings for extension and new construction Improved safety for personnel and equipment 24

25 Project 3: ASL Ainsworth Lane (Scottish Power) System ready tested Delivery Feb

26 Thank you very much for your attention Any Questions? Contact Details: Joachim Bock +49 (0) Gerhard Novak +44 (0)

27 Superconductivity Superconductivity what is that? Superconductivity is a physical phenomena which happens at very low temperatures (-270 to -273 C) at this low temperatures the resistance of an electric conductor drops to zero. This phenomenon is known since 1911 but it is only recently (1986) that materials have been developed which show this phenomena at higher temperatures - The so called high temperature superconductors. The temperature is still not high as we speak about 85K (approx -188 C) but this temperature is easier to reach than -273 C Where do we find superconductors? Wherever the need for a strong magnetic field is (CERN particle accelerator, Magnet resonance tomography) and where energy needs to be transported with low resistive losses (superconductive cables) 27

28 Superconductivity As the resistance of a superconductive material is zero it will not heat up during normal use. But there is one other physical limit the current density. (Ampere per mm 2 ) The current density of a superconductor is approximately 1000 to times higher than that of copper if the current flow goes above this limit the superconductor starts to heat up and instantly loses its special superconductive properties until it is cooled down to 85K again. This effect is used for the SFCL back up 28