Switching arc initiation, schematic current / voltage during current interruption, importance of short circuit current and Transient recovery voltage, dielectric recovery, thermal / dielectric re-ignitions.
b. Basics of arc physics
Dynamic arc behavior, Arc in gaseous medium, thermal ionization mechanism
Arc in low pressure / vacuum, thermo-field emission / impact ionization
c. Arc modeling basics
Brief description of different modeling levels (detailed physical models, qualitative arc models as well as black box models), basic consideration of arc-network interaction (current commutation .)
3. Application of power switching devices in power networks
a. Interruption of fault current
Short circuit current (symmetrical / asymmetrical, decay DC, neutral point) different TRV forms, standard for CB
Testing methods (direct / synthetic)
b. Closing under fault condition (short circuit making)
Pre-strike, arc energy, importance for LBS and earthing switch, standard for LBS and CB, test circuit
c. Energizing of loads
Over-voltages, trapped charges, reclosing
d. Switching of inductive loads
Importance of increased RRRV
e. Switching of capacitive loads
Inrush current, pre-strike, 1-cos TRV, re-strike / re-ignition, voltage escalation, standard requirements, test methods
f. Switching of small inductive currents
Current chopping, multiple re-ignitions, virtual current chopping, transient over-voltages
4. Current interruption technologies: present status
a. different types of power switching components
Different parts of a power-switching device, Classification of power switching components based on the requirements, installation, rated voltage as well as arc-extinguishing medium
b. disconnecting switches
Construction for different voltage ratings, challenges including short circuit current carrying capability, mechanical considerations
c. load break switches
Different technologies, application to MV, gaseous LBS, vacuum contactor, peculiarities regarding load current interruption and fault current making, transient switching over-voltages
d. fuse
Arc extinguishing principle in fuse, applications MV / LV, limitations, Is-limiter, possible applications, RMU, fuse + LBS combination
e. circuit breakers
i. Oil circuit breakers
Interruption principle, minimum oil vs. bulk oil CBs, brief description of role of cross baffle, parallel resistor, etc.
ii. Gas circuit breakers
Principle of current interruption in gases, brief description of importance of different cooling mechanisms, construction of compressed air, double pressure SF6, single pressure SF6, puffer vs. self-blast
iii. Magnetic air CB
Current interruption principle, arc elongation + cathode/anode fall, blow out coil, construction of LV CBs
iv. Vacuum CB
Simple construction of VCB, dielectric breakdown in vacuum, different modes of arc in vacuum, role of magnetic field, different technologies to control switching arc in vacuum
5. Future trends of power switching devices
a. HVDC current interruption
Missing CZ, fast operation, principle of current interruption in DC network, upcoming applications, review of different schemes, hybrid circuit breakers, challenges
b. Fault current limitation
Upcoming applications, nonlinear current dependent impedance in network, energy absorption /conversion during the fault, brief review of different schemes, challenges
c. Condition assessment
Importance of condition monitoring in view of recent developments in power systems, brief review of different condition monitoring + decision making concepts, challenges / open questions