Quality and Security Assessment of Protection Systems Prof. Dr. Rainer Krebs Principal Expert Power Technologies Siemens Energy

Industrial Power System Transmission Distribution Public & Private Utilities Industrial Power System Primary Systems Protection & Control Systems – ~ Contents Protection Systems Power System Influences on Protection Systems Cascading Protection Trips Quality and Security Assessment Conclusion 26-28 May 2009 R. Krebs

Protection Systems From Primary Energy Sources to Consumers Windparcs Onshore/Offshore Double fed ASM Voltage Source Converters Industries Large Motors, Generators Power Electronics Dynamic Loads Transmission Short and long lines, cables Transformers Diff. Busbar Configs FACTS / HVDC Oil and Gas, Harbor- and Special Systems MVDC-SIPLINK LNG Power Plants Large Generators Large Motors Auxiliary Systems Distribution Various Switching Situations DGs Short-circuit Current Limiters 26-28 May 2009 R. Krebs

Protection Systems Consist of Relay Types of Nearly All Eras SIPROTEC V4 SIPROTEC V1-V3 1950 1960 1970 1980 1990 2000 2010 Control Numerical Protection Relays Analog Relays Electromechanical Relays 26-28 May 2009 R. Krebs

Protection Systems Consist of Relay Types of all Nearly All Manufacturers 26-28 May 2009 R. Krebs

Protection Systems Standard Structure signal sampling processing analysis Trip signal formation Protection Equipment System kV, kA protection object System V, A signal adaption circuit breaker control circuit breaker auxiliary power 26-28 May 2009 R. Krebs

Protection Systems Power System Influences Frequency ‚Very Fast Transients‘ Transients & Equipm. Interactions Switching Voltages Surge Voltages Power Converters Ferro-Resonances Transformer Switching System Resonances 40 MHz 10 MHz 5 kHz 1 kHz 100 Hz 10 kHz Power Plant > System > Load 50 Hz fn E-Generation E-Transmission Control & Protection Subsynchronous Resonances Power Swings Oscillations of the Turbine-Generator Multimass System (Power Plants > 300MW) Rotor Oscillations of Generators 10 Hz 5 Hz 0 Hz 26-28 May 2009 R. Krebs

Protection Systems Power System Influences Inrush currents Transformer overexcitation CT saturation Variable system impedances with FACTS Non system frequent voltages with capacitive voltage transformers Sub-synchronous frequencies with series compensation Power swings Inter-area oscillations High equipment and route capacity utilization 26-28 May 2009 R. Krebs

Protection Systems Involvement in Cascading Outages Practically there was no blackout without involvement of protection relays! - Zone 3 trips of distance relays, often used for overload protection instead of use of thermal models in numerical relays - Trip of Distance relays due to missing load and power swing blocking - Uncoordinated protection / or overload settings across borders between diff. Utilities - Too low synchro-check settings - OC backup in parallel to distance or differential without delay - Development of primary system without adaption of relaying design and relay settings - Wrong settings, no system measurements like zero-sequence impedances Analysis and recommendations for improvement is mandatory! 26-28 May 2009 R. Krebs

Protection Systems Development of Selectivity over Years Problem area ‚short-circuit‘ can often not clearly be confined towards the problem areas ‚overload‘, ‚power swing‘ or other system disturbances. Design of the protection system and equipment selection follows standard company rules despite of new requirements defined by modern power systems No consideration of system emergency situations during settings calculation No consideration of system changes and extensions during settings calculations Distance Protection New Protection Concept ! Short-Circuit Emergency Operation, Overload 26-28 May 2009 R. Krebs

Protection Systems Example for Non-Selectivity after Years Sammis-Star Example Canada-US-Blackout 2003 50 100 X/Ohm R/Ohm MHO-Characteristic Blinders must be used for load impedance areas in normal and overload situation  Load impedance during emergency operation Value during US-Blackout 2003  Min. load impedance during normal operation, planning value 26-28 May 2009 R. Krebs

Protection Systems Quality and Security Stability avoids disconnections by false tripping Speed limits damages maintains system stability Modern Protection System avoids overfunction avoids underfunction Security limits isolation area increases availability Selectivity 26-28 May 2009 R. Krebs

Quality and Security Assessment Check and Dimensioning of Instrument Transformers Check of CTs und VTs for changed conditions For relays of all manufacturers Acc. to all international standards For all protection systems Simulation and documentation CTDIM 3.2 26-28 May 2009 R. Krebs

Quality and Security Assessment with SIGUARD® - PSA Analysis of Backup O/C-Protection Line No. ^1-phase-to-ground short-circuit: Fault location at % line length Backup OC Protection-System Behavior p th 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 -1 unselective No trip t/s Actual State of the System SIGUARD® - Patents pending 26-28 May 2009 R. Krebs

Quality and Security Assessment with SIGUARD® - PSA Adapted Settings for Backup O/C Protection Line No. 1-phase-to-ground short-circuit: Fault location at % line length Backup OC Protection-System Behavior p th 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 1 2 3 4 6 7 8 9 11 12 13 14 16 17 18 19 21 22 23 -1 unselective No trip t/s Actual State of the System Revised Relay Settings SIGUARD® - Patents pending 26-28 May 2009 R. Krebs

Quality and Security Assessment with SIGUARD® - PSA Analysis of Distance Protection for Diff. Fault Resistances Fehlerwiderstand < 2,5 Ohm < 2,4 Ohm < 2,3 Ohm < 2,2 Ohm < 2,1 Ohm < 2,0 Ohm < 1,9 Ohm < 1,8 Ohm < 1,7 Ohm < 1,6 Ohm < 1,5 Ohm < 1,4 Ohm < 1,3 Ohm < 1,2 Ohm < 1,1 Ohm < 1,0 Ohm < 0,9 Ohm < 0,8 Ohm < 0,7 Ohm < 0,6 Ohm < 0,5 Ohm < 0,4 Ohm < 0,3 Ohm < 0,2 Ohm < 0,1 Ohm < 0,0 Ohm 26-28 May 2009 R. Krebs

Quality and Security Assessment with SIGUARD® - PSA Analysis of Distance Protection for Diff. Fault Resistances SIGUARD® - Patents pending 26-28 May 2009 R. Krebs

Quality and Security Assessment with SIGUARD® - PSA Analysis of Distance Protection for Diff. Fault Resistances SIGUARD® - Patents pending 26-28 May 2009 R. Krebs

Conclusion Power systems are changing in Structure Generation Utilization Quality and security of the protection system can be assessed continuously or from time to time with SIGUARD® - PSA Settings have to be adapted where necessary to avoid wrong or cascading trips Relay functionalities have to be adapted where necessary Communication has to be installed where necessary Measures can be validated with SIGUARD® - PSA 26-28 May 2009 R. Krebs

Thank you for your attention! Prof. Dr. Rainer Krebs Principal Expert Power Technologies Head of System Protection and Power Quality Siemens AG, E D SE PTI Freyeslebenstr. 1 91058 Erlangen Telefon: +49 9131 – 7 33515 Fax: +49 9131 – 7 35017 Mobil: +49 171 – 3026091 E-Mail: Rainer.Krebs@siemens.com