EARTH-FAULT SEMINAR, 2018 Taking earth-fault protection to the next level Earth-fault protection in compensated distribution networks Ari Wahlroos. Senior Principal Engineer, ABB Oy, Finland Taking earth-fault protection to the next level Earth-fault protection in compensated networks Experience and know-how ABB Technology leadership There are over 1,500,000 ABB Distribution Automation products installed around the world Pioneering products and innovations over 50 years Service and spare sparts available even for products delivered over 40 years ago REX640, SSC600 2018 Relion product family 2009 The first native IEC 61850 2007 feeder protection relay REF615 Communication Gateway COM610 2004 610 series 2003 RED 500 series protection relays and terminals 1995 Feeder protection relay SPAJ 140 C Integration of prot & control into one unit – SPAC terminal 1989 1987 SPACOM series relay featuring 1985 serial communication © ABB Group November 19, 2018 | Slide 4 Microprocessor-based multifunction relay SPAJ 3M5 J3 1982 Static protective relays for distribution networks 1965 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Content of the presentations Part 1: Fundamentals of earth-fault current compensation and earth-fault protection in compensated networks Basics of earth-fault current compensation Compensated earth-fault current Interpretation of coil controller values Part 2: Effect of earth-fault current compensation into directional earth-fault protection Fundamentals of measurements of Uo and Io, polarities, accuracy Basic earth-fault operation point analysis, affecting quantities Measurement at healthy and faulty feeder © ABB Group November 19, 2018 | Slide 15 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Content of the presentations Part 3: Different earth fault types and their challenges Earth-fault types and their characteristics Re-striking, intermittent earth fault Available earth-fault protection methods in ABB Relion MV-relays Part 4: Multi-frequency admittance based earth-fault protection Background and motivations for the new function Operation principle and advantages Application, settings, secondary testing Practical experience, field test results © ABB Group November 19, 2018 | Slide 16 ABB EARTH-FAULT SEMINAR, 2018 Taking earth-fault protection to the next level Fundamentals of earth-fault current compensation and earth-fault protection in compensated networks Ari Wahlroos. Senior Principal Engineer, ABB Oy, Finland Taking earth-fault protection to the next level Earth-fault protection in compensated networks RIO600 REF615 Single phase earth fault RIO600 Taking earth-fault protection to the next level Earth-fault protection in compensated networks Taking earth-fault protection to the next level Earth-fault protection in compensated networks MV-neutral point A B ? C Taking earth-fault protection to the next level Earth-fault protection in compensated networks 100 years of resonant earthed networks! © ABB Group November 19, 2018 | Slide 7 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks “Compensated” networks Compensated network Arc Suppression Coil (ASC) or Petersen coil earthed network © ABB Group November 19, 2018 | Slide 8 • Resonant(ly) earthed network • High impedance earthed network ABB EARTH-FAULT SEMINAR, 2018 Taking earth-fault protection to the next level Earth-fault current compensation Ari Wahlroos. Senior Principal Engineer, ABB Oy, Finland Taking earth-fault protection to the next level Earth-fault protection in compensated networks Unearthed network • Composition of earth-fault current Capacitive earth-fault current contribution of over-head line ~0.06A/km@20kV +Uo IEF UvS, UvT Capacitive current Resistive current UE UE = Earth potential raise, earthing voltage = IEF * ZE Taking earth-fault protection to the next level Earth-fault protection in compensated networks Unearthed network • Composition of earth-fault current Capacitive earth-fault current contribution of over-head line ~0.06A/km@20kV +Uo Capacitive earthfault current contribution of 3-ph cable ~3…5A/km@20kV! IEF UvS, UvT Capacitive current Resistive current UE UE = Earth potential raise, earthing voltage = IEF * ZE Taking earth-fault protection to the next level Earth-fault protection in compensated networks “Compensated” network +Uo IEF UvS, UvT Capacitive current Inductive current Resistive current UE UE = Earth potential raise, earthing voltage = IEF * ZE Taking earth-fault protection to the next level Earth-fault protection in compensated networks • Alternative ways to implement earth-fault current compensation: L1 L2 L3 110/20kV åIL = Io Ro Co • Centralized compensation • Coil is installed either into neutral point of the feeding main traformer +Uo 500V LCOIL Petersen coil © ABB Group November 19, 2018 | Slide 13 Rpar Parallel resistor ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • Alternative ways to implement earth-fault current compensation: L1 L2 L3 110/20kV åIL = Io Ro Co • Centralized compensation • Coil is installed either into neutral point of the feeding main traformer • or at the neutral point of grounding transformer Grounding transformer ZN-connection 500V LCOIL © ABB Group November 19, 2018 | Slide 14 Petersen coil Rpar Parallel resistor +Uo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • Alternative ways to implement earth-fault current compensation: L1 L2 L3 110/20kV åIL = Io Ro Co • Centralized compensation • Coil is installed either into neutral point of the feeding main traformer • or at the neutral point of grounding transformer Grounding transformer ZN-connection +Uo 500V LCOIL Petersen coil © ABB Group November 19, 2018 | Slide 15 Rpar Parallel resistor LFIX • ‘Plunger’ core (continuously tunable) or fixed value • Typical rating: up to several hundreds of amperes per coil ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • Alternative ways to implement earth-fault current compensation: L1 L2 L3 110/20kV åIL = Io Ro Co • Centralized compensation • Coil is installed either into neutral point of the feeding main traformer • or at the neutral point of grounding transformer Grounding transformer ZN-connection +Uo 500V LCOIL Petersen coil © ABB Group November 19, 2018 | Slide 16 • ‘Plunger’ core (continuously tunable) or fixed value • Typical rating: up to several hundreds of amperes per coil Rpar Parallel resistor LFIX I par 500V 500V 8.7 A 2.5ohm 20000 / 3V • Parallel resistor at PAWwinding is used to increase the value of Iocos used by feeder protection ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 MV/LV 110/20kV åIL = Io Ro Co LCOIL_DST L1 L2 L3 PEN • Alternative ways to implement earth-fault current compensation: • Distributed compensation • Applied to limit capacitive current contribution of long cable feeders L1 L2 L3 åIL = Io Yo • Typical rating: 5-15Aind/coil • Several different device configurations available L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 17 Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Distributed compensation, recommendations • SWEDEN: When capacitive earthfault current of protected feeder contribution exceeds 50 A is is recommend to install distributed coils • NORWAY: When capacitive earthfault current of protected feeder contribution exceeds 40 A is is recommend to install distributed coils © ABB Group November 19, 2018 | Slide 18 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 MV/LV 110/20kV åIL = Io Ro Co LCOIL_DST Yo L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 19 • Distributed compensation • Applied to limit capacitive current contribution of long cable feeders L1 L2 L3 åIL = Io L1 L2 L3 PEN • Alternative ways to implement earth-fault current compensation: Yo • Typical rating: 5-15Aind/coil • Several different device configurations available • If earth-fault current compensation is done with only distributed coils, then feeder earth-fault protection is based on imaginary part of Io (Iosin-method) ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 MV/LV 110/20kV åIL = Io Co LCOIL_DST L1 L2 L3 LFIX åIL = Io +Uo Ro Yo 500V LCOIL Petersen coil Rpar Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 20 L1 L2 L3 PEN • Alternative ways to implement earth-fault current compensation: • Centralized or/and distributed compensation • Centralized and tunable coil is used to compensated ’base’ part of earth-fault current • Distributed coils are applied to limit capacitive current contribution of long cable feeders • Feeder earth-fault protection is based on real part of Io (Iocos-method) Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Compensated network: Petersen coil controller +Uo IEF UvS, UvT Capacitive current UE REX640, Petersen coil tuner application UE = Earth potential raise, earthing voltage = IEF * ZE Inductive current Resistive current Taking earth-fault protection to the next level Earth-fault protection in compensated networks Compensated network: Petersen coil controller +Uo IEF Fundamental parameters of compensated network UvS, UvT 1. Network unbalance Unbalance of phase-to-earth capacitance (𝐶0_𝐿1 ≠ 𝐶0_𝐿2 ≠ 𝐶0_𝐿3 ) 2. Network resonance point Inductive current of the coil(s), which matches the capacitive earth-fault current of the network 3. Network compensation degree (detuning) Coil (de)tuning value, setting (% or A) 4. Network damping Total losses of the zero-sequence circuit, ~real-part of earth-fault current, estimated by the controller Capacitive current UE UE = Earth potential raise, earthing voltage = IEF * ZE Inductive current Resistive current Taking earth-fault protection to the next level Earth-fault protection in compensated networks Compensated network: Petersen coil controller +Uo IEF Fundamental parameters of compensated network UvS, UvT 1. Network unbalance Unbalance of phase-to-earth capacitance (𝐶0_𝐿1 ≠ 𝐶0_𝐿2 ≠ 𝐶0_𝐿3 ) 2. Network resonance point Inductive current of the coil(s), which matches the capacitive earth-fault current of the network Capacitive current UE UE = Earth potential raise, earthing voltage = IEF * ZE Coil (de)tuning value, setting (% or A) 4. Network damping Resistive current Earth-fault current magnitude: 3. Network compensation degree (detuning) Inductive current Total losses of the zero-sequence circuit, ~real-part of earth-fault current, estimated by the controller 𝐼𝐸𝐹 = 2 2 2 2 2 𝐼𝐷𝑎𝑚𝑝𝑖𝑛𝑔 + 𝐼𝐷𝑒𝑡𝑢𝑛𝑖𝑛𝑔 + (𝐼𝐻𝑎𝑟𝑚2 +𝐼𝐻𝑎𝑟𝑚3 + ⋯ + 𝐼𝐻𝑎𝑟𝑚𝑛 ) Taking earth-fault protection to the next level Earth-fault protection in compensated networks Interpretation of values calculated by the coil controller © ABB Group November 19, 2018 | Slide 28 Resonance curve with operation point • Behavior of Uo-voltage during healthy-state as a function of Petersen coil current (detuning) • Shape depends on the degree of admittance imbalance and total damping of the network • Indication of maximum Uo value at resonance • Affected by the connection status of parallel resistor of the coil ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Interpretation of values calculated by the coil controller Network resonance point seen by the Petersen coil controller • This value includes the effect of fixed and distributed coils • At this coil current value, Uo reaches maximum level © ABB Group November 19, 2018 | Slide 29 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Interpretation of values calculated by the coil controller Coil detuning in amperes •This value determines the actual fault current during earth fault •Pos. value over-comp. •Neg.-value under-comp •0 resonance © ABB Group November 19, 2018 | Slide 30 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Interpretation of values calculated by the coil controller © ABB Group November 19, 2018 | Slide 31 Total damping of the network • This the real-part of fault current at galvanic fault that is not compensated by the Petersen coil • This value is used by protection and it provides damping to the oscillations • Value depends on the value and connection status of the parallel resistor of the coil ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Interpretation of values calculated by the coil controller Fault current magnitude when RF = 0ohm I_FLT = ABS(I_DAMPING + j*I_DETUNING) • I_FLT: A Icoil: A © ABB Group November 19, 2018 | Slide 32 This is the expected fault current value with current detuning and total losses of the network during galvanic fault • Possible fault resistance will reduce this value ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Compensated systems Benefits vs. Drawbacks IMPROVED SAFETY AND SERVICE QUALITY CHALLENGING EARTH-FAULT (EF) PROTECTION • The inductive current of the coil reduces the capacitive fault current, 95…97% • High sensitivity requirements • Self-extinguishing of arcing faults • Network operation possible during a sustained earth fault • Accurate measurement required • Special functionality required due to multitude nature of earth faults • Improved power quality and reliability for the customer © ABB Group November 19, 2018 | Slide 34 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Compensated neutral earthing is prevailing MV-neutral earthing practice globally! © ABB Group November 19, 2018 | Slide 35 ABB EARTH FAULT SEMINAR, 2018 Taking earth-fault protection to the next level Effect of earth-fault current current compensation into directional earth-fault protection Ari Wahlroos. Senior Principal Engineer, ABB Oy, Finland Taking earth-fault protection to the next level Earth-fault protection in compensated networks EARTH-FAULT PROTECTION SHORT-CIRCUIT PROTECTION Z = U/I= R + j*X Im (Io) OPERATE SECTOR Im (Z) -(Uo) Re (Io) Re (Z) © ABB Group November 19, 2018 | Slide 2 OPERATE SECTOR Y =Io/Uo= G + j*B ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Main transformer L1 L2 L3 110/20kV L1 L2 L3 500V LCOIL Petersen coil © ABB Group November 19, 2018 | Slide 4 Rpar Parallel resistor L1 L2 L3 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 L1 L2 L3 110/20kV Substation busbar L1 L2 L3 500V LCOIL Petersen coil © ABB Group November 19, 2018 | Slide 5 Rpar Parallel resistor L1 L2 L3 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 L1 L2 L3 110/20kV Outgoing feeders L1 L2 L3 500V LCOIL Petersen coil © ABB Group November 19, 2018 | Slide 6 Rpar Parallel resistor L1 L2 L3 ABB Taking earth-fault protection to the next level Earth fault protection in compensated networks L1 L2 L3 L1 L2 L3 110/20kV L1 L2 L3 Petersen coil or Arc Suppression coil (ASC) 500V LCOIL Petersen coil Rpar Parallel resistor L1 L2 L3 Parallel resistor © ABB Group November 19, 2018 | Slide 7 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 L1 L2 L3 110/20kV åIL = Io L1 L2 L3 åIL = Io 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 8 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 L1 L2 L3 110/20kV • During a solid earth fault (RF=0 ohm), neutral point voltage Uo will be same as system phase-to-earth voltage: 11.547kV in 20kV system • Typically this equals 100V or 110V in the open-delta winding åIL = Io • L1 L2 L3 Recommended accuracy class 3P: Amplitude error: ±3% Phase displacement: ±2o åIL = Io L1 L2 L3 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor √3 L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 9 20 A A N dn N dn A PRIMARY WÌNDING kV 100 3 N dn V da da da TERTIARY 3U0 WINDINGS OPEN-DELTA ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • Polarity of Uo voltage: • ABB Relion MV-relays are connected to measure +Uo voltage! REF6XX +Uo + - + - © ABB Group November 19, 2018 | Slide 10 + ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 L1 L2 L3 110/20kV åIL = Io • Current Io is measured preferably with accurate cable core CT (CBCT) KOKM 1RL12, 0.5S/5P10, 100/1, 1VA, 180mm Neutral point voltage L1 measurement L2 L3 åIL = Io PRIMARY WÌNDING 500V LCOIL +Uo Petersen coil A B C A Rpar FAULT LOCATION, N N N phase L1 dn dn dn Parallel resistor V åIL = Io da da Residual current measurement Uo Io Io A kV da © ABB Group November 19, 2018 | Slide 11 A Protection relay CBCT L1 L2 U L3 o TERTIARY WINDINGS OPEN-DELTA ABB Taking earth-fault protection to the next level Kompensoidun verkon maasulkusuojaus REF6XX • Polarity of Io current: • ABB Relion MV-relays are connected to measure -Io current! Note: Minus polarity! - -Io © ABB Group November 19, 2018 | Slide 12 + + - ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • Longitudial impedance vs. shunt admittance: L1 L2 L3 Z1 L1 L2 L3 110/20kV åIL = Io Ro Co Z1 L1 L2 L3 åIL = Io Yo • 10km conductor: Longitudial impedance: Z1 =~ few ohms 500V LCOIL +Uo Petersen coil Rpar Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 13 Shunt admittance: FAULT LOCATION, phase L1 Z1 Yo Xco 1 1 Co 100 Co XCo =~ thousends of ohms Longitudial impedance can be ~ignored!… ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • Longitudial impedance vs. shunt admittance: L1 L2 L3 Z1 L1 L2 L3 110/20kV åIL = Io Ro Co Z1 L1 L2 L3 åIL = Io Yo • 10km conductor: Longitudial impedance: Z1 =~ few ohms 500V LCOIL +Uo Petersen coil Rpar Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 14 Shunt admittance: FAULT LOCATION, Z1 phase L1 Yo Xco 1 1 Co 100 Co XCo =~ thousends of ohms Longitudial impedance can be ~ignored!… ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 L1 L2 L3 110/20kV åIL = Io Ro Co L1 L2 L3 åIL = Io Yo 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor • There are always some “natural losses”, resistive shunt losses present L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 15 • In practice, the network admittances are dominantly capacitive as they are due to the phaseto-earth capacitances of the electrical conductors: overhead lines and underground cables Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 L1 L2 L3 110/20kV åIL = Io Ro Co L1 L2 L3 åIL = Io Yo 500V LCOIL +Uo Petersen coil Rpar x 50!! Larger Co FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 16 • In practice, the network admittances are dominantly capacitive • Their practical value depends on the share of cables in the network! Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • Usage of underground cabling is increasing in MV-level! • Affects to the earth-fault current magnitude! © ABB Group November 19, 2018 | Slide 17 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • Usage of underground cabling is increasing in MV-level! • Affects to the earth-fault current magnitude! © ABB Group November 19, 2018 | Slide 18 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • What earth-fault protection measures during healthy state? © ABB Group November 19, 2018 | Slide 19 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L1 L2 L3 Capacitive current Inductive current L2 L3 L1 L2 L3 Resistive current 110/20kV Ro åIL = Io Co ~very small value • During the HEALTHY STATE residual current and voltage are (typically) very small. • The exact value depends on the natural asymmetry of the network. L1 L2 L3 åIL = Io ~very small value Yo 500V LCOIL +Uo Rpar ~small value Petersen coil Parallel resistor FAULT LOCATION, phase L1 L1 L2 L3 åIL = Io ~very small value © ABB Group November 19, 2018 | Slide 20 Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • What earth-fault protection measures during fault? HEALTHY FEEDER © ABB Group November 19, 2018 | Slide 21 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro Co L1 L2 L3 åIL = Io Yo 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 22 Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro Co L1 L2 L3 åIL = Io Yo • Residual current Io measured at the beginning of a healthy feeder equals the earth fault current produced by the phaseto-earth admittances of that feeder! • Practical magnitude depends on the cable km in feeder • It is dominantly capacitive! • It flows from line towards busbar! Im(Io) 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor åIL = Io © ABB Group November 19, 2018 | Slide 24 Re(Io) L1 L2 L3 Yo -Uo Io ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro Co L1 L2 L3 åIL = Io Yo • Residual current Io measured at the beginning of a healthy feeder equals the earth fault current produced by the phaseto-earth admittances of that feeder! • Practical magnitude depends on the cable km in feeder • It is dominantly capacitive! • It flows from line towards busbar! Im(Io) 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor åIL = Io © ABB Group November 19, 2018 | Slide 25 Re(Io) L1 L2 L3 -Uo Yo Io ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro Co L1 L2 L3 åIL = Io Yo • Residual current Io measured at the beginning of a healthy feeder equals the earth fault current produced by the phaseto-earth admittances of that feeder! • Practical magnitude depends on the cable km in feeder • It is dominantly capacitive! • It flows from line towards busbar! Im(Io) 500V LCOIL +Uo FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 26 OPERATE SECTOR Petersen coil Rpar Re(Io) -Uo Yo Io ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 L1 L2 L3 110/20kV åIL = Io • Current Io is measured preferably with accurate cable core CT (CBCT) KOKM 1RL12, 0.5S/5P10, 100/1, 1VA, 180mm Neutral point voltage L1 measurement L2 L3 åIL = Io PRIMARY WÌNDING 500V LCOIL +Uo Petersen coil A B C A Rpar FAULT LOCATION, N N N phase L1 dn dn dn Parallel resistor V åIL = Io da da Residual current measurement Uo Io Io A kV da © ABB Group November 19, 2018 | Slide 27 A Protection relay CBCT L1 L2 U L3 o TERTIARY WINDINGS OPEN-DELTA ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks ! • Current Io is measured preferably with accurate cable core CT (CBCT) KOKM 1RL12, 0.5S/5P10, 100/1, 1VA, 180mm Neutral point voltage measurement A B C PRIMARY WÌNDING A A Protection relay Residual current measurement Uo Io Io A kV CBCT N dn N dn N dn V Uo da da da TERTIARY WINDINGS OPEN-DELTA © ABB Group November 19, 2018 | Slide 28 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks ! • Current Io is measured preferably with accurate cable core CT (CBCT) KOKM 1RL12, 0.5S/5P10, 100/1, 1VA, 180mm Neutral point voltage measurement A B C PRIMARY WÌNDING A A Protection relay Residual current measurement Uo Io Io A kV CBCT N dn N dn N dn V Uo da da da TERTIARY WINDINGS OPEN-DELTA © ABB Group November 19, 2018 | Slide 29 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks “Combi-class CBCT” Recommended! KOKM 1RL12, 0.5S/5P10, 100/1, 1VA, 180mm © ABB Group November 19, 2018 | Slide 30 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Not all CBCTs are equal! • “Window”-type CBCT have larger phase displacements compared with Ring-type • “Window”-type CBCT are not applicable for sensitive directional earth-fault protection © ABB Group November 19, 2018 | Slide 31 • With Split-core CBCT, the “true” accuracy depends on the installation quality • Especially any air gap should be avoided as it introduces large phase displacement! ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • What earth-fault protection measures during fault? FAULTY FEEDER © ABB Group November 19, 2018 | Slide 32 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro Co L1 L2 L3 åIL = Io Yo 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 34 • Residual current Io measured at the beginning of a faulty feeder is affected by the inductive current of the coil (ASC) i.e. compensation degree • The inductive current of the coil (ASC) is ONLY seen in the faulty feeder • Also the additional resistive current of the parallel resistor is only measured at the faulty feeder Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNEARTHED NEUTRAL POINT Co L1 L2 L3 åIL = Io • Coil is disconnected and the network becomes unearthed network (isolated neutral) • The earth-fault current is determined by the total phase-to-earth admittances (capacitances) of the network Yo 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 35 Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNEARTHED NEUTRAL POINT Co L1 L2 L3 åIL = Io Yo Io Im(Io) 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 36 • In unearthed network residual current Io measured at the beginning of a faulty feeder is dominantly capacitive! • It is due to phase-to-earth admittances of the “background network” • It flows from busbar towards line! Re(Io) -Uo Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNEARTHED NEUTRAL POINT Co L1 L2 L3 åIL = Io Yo Io Im(Io) FAULTY 500V LCOIL +Uo Petersen coil Rpar OPERATE SECTOR (Iosin) FAULT LOCATION, phase L1 Parallel resistor Re(Io) L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 37 • In unearthed network residual currents Io measured at the beginning of a faulty and healthy feeders are both dominantly capacitive! • But their direction is opposite (~180 apart)! • Easy discrimination based on the reactive part of Io Yo -Uo Io HEALTHY ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNEARTHED NEUTRAL POINT Co L1 L2 L3 åIL = Io Yo Io Im(Io) FAULTY 500V LCOIL +Uo Petersen coil Rpar OPERATE SECTOR (Iosin) FAULT LOCATION, phase L1 Parallel resistor Re(Io) L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 38 • In unearthed network residual currents Io measured at the beginning of a faulty and healthy feeders are both dominantly capacitive! • But their direction is opposite (~180 apart)! • Easy discrimination based on the reactive part of Io Yo -Uo Io HEALTHY ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNDERCOMPENSATED STATE Co L1 L2 L3 åIL = Io Yo Im(Io) 500V LCOIL +Uo Petersen coil Io Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 39 • Compensation coils is connected and the coil current is gradually increased…1 Re(Io) -Uo Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNDERCOMPENSATED STATE • Compensation coils is connected and the coil current is gradually increased…2 Co L1 L2 L3 åIL = Io Yo Im(Io) 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 40 Io Re(Io) -Uo Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNDERCOMPENSATED STATE • Compensation coils is connected and the coil current is gradually increased…3 Co L1 L2 L3 åIL = Io Yo Im(Io) 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 41 Io Re(Io) -Uo Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNDERCOMPENSATED STATE Co L1 L2 L3 åIL = Io Yo Im(Io) 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 42 • Compensation coils is connected and the coil current is gradually increased…4 • Now level of undercompensation equals feeder earth-fault current • Protection does not see any reactive component! Io Re(Io) -Uo Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNDERCOMPENSATED STATE Co L1 L2 L3 åIL = Io Yo Im(Io) 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 43 • Compensation coils is connected and the coil current is gradually increased…5 • Phasor turns in same direction as in healthy feeder! Re(Io) Io -Uo Yo ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro RESONANCE STATE Co L1 L2 L3 åIL = Io Yo Im(Io) 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor Re(Io) L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 44 • Compensation coils is connected and the coil current is gradually increased…6 • Phasor turns in same direction as in healthy feeder! • Resonance state: Only resistive component and harmonics present in the earth-fault current! Yo -Uo Io ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro Co RESONANCE STATE • In compensated network residual currents Io measured at the beginning of a faulty and healthy feeders are seen similarly, the reactive part • Discrimination must be based on the resistive part L1 L2 L3 åIL = Io Yo Im(Io) 500V LCOIL +Uo Petersen coil Rpar FAULT LOCATION, phase L1 Parallel resistor åIL = Io © ABB Group November 19, 2018 | Slide 45 Re(Io) L1 L2 L3 Yo -Uo HEALTHY Io Io FAULTY ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro Co RESONANCE STATE L1 L2 L3 åIL = Io Yo • In compensated network residual currents Io measured at the beginning of a faulty and healthy feeders are seen similarly, the reactive part • Discrimination must be based on the resistive part • Reliable detection requires typically additional resistive component from parallel resistor Im(Io) 500V LCOIL +Uo Rpar FAULT LOCATION, phase L1 Parallel resistor OPERATE SECTOR Petersen coil Ipar L1 L2 L3 åIL = Io Yo Io Re(Io) -Uo Io Ipar © ABB Group November 19, 2018 | Slide 46 ABB Taking earth-fault protection to the next level Interpretation of values calculated by the coil controller Total damping of the network • This the real-part of fault current at galvanic fault that is not compensated by the Petersen coil • This value is used by protection and it provides damping to the oscillations • Value depends on the value and connection status of the parallel resistor of the coil © ABB Group November 19, 2018 | Slide 47 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Resistive part of fault current ~resistive part of Io: information from coil regulator: damping! Parallel resistor CONNECTED Parallel resistor DISCONNECTED 2.7 I_DAMPING (Parallel resistor switched off)= Shunt losses of the network + Losses of the coil(s) = 2.7A/66A=~4% ”Total losses/damping of the network”: I_DAMPING [A or %] Losses of the parallel resistor (ON/OFF!) Losses of the coil(s) Shunt losses of the network Approximate value of resistive current measured at the faulty feeder by protection during galvanic (RF = 0ohm) earth-fault! Provides damping to the transient oscillations! • • • © ABB Group November 19, 2018 | Slide 48 ABB Taking earth-fault protection to the next level Parallel resistor logic (Rf = 5000 ohm): OFF-ON • Disconnection of parallel resistor may result in delayed operation of protection Recommendation to keep parallel resistor connected or connect immediately when earth-fault is detected! © ABB Group November 19, 2018 | Slide 49 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Effect of under- and over-compensation? © ABB Group November 19, 2018 | Slide 50 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro OVERCOMPENSATED STATE Co • In compensated network residual currents Io measured at the beginning of a faulty and healthy feeders are seen similarly, the reactive part • Discrimination must be based on the resistive part • L1 L2 L3 åIL = Io Yo Over-compensated state: earth-fault current has inductive and resistive component Im(Io) 500V LCOIL +Uo Rpar FAULT LOCATION, phase L1 Parallel resistor OPERATE SECTOR Petersen coil Ipar L1 L2 L3 åIL = Io Yo HEALTHY Io FAULTY Io © ABB Group November 19, 2018 | Slide 51 Ipar Re(Io) -Uo Amount of overcompen sation ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro UNDERCOMPENSATED STATE Co • In compensated network residual currents Io measured at the beginning of a faulty and healthy feeders are seen similarly, the reactive part • Discrimination must be based on the resistive part • L1 L2 L3 åIL = Io Yo Under-compensated state: earth-fault current has capacitive and resistive component Im(Io) 500V LCOIL +Uo Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 52 OPERATE SECTOR Petersen coil Ipar Yo HEALTHY Io I Ipar o FAULTY Re(Io) -Uo Amount of undercompensation ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Effect of high eart-fault current contribution of faulted feeder? © ABB Group November 19, 2018 | Slide 53 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro Co • RESONANCE STATE L1 L2 L3 åIL = Io At the beginning of a faulty feeder, the reactive part depends: • On the phase-to-earth capacitance of the feeder • On the tuning degree of the coil Fault in the long cable feeder moves operation point towards the boundary Yo Im(Io) 500V LCOIL +Uo FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 54 OPERATE SECTOR Petersen coil Rpar Re(Io) -Uo Yo Io Io Ipar ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks • L1 L2 L3 Capacitive current Inductive current L1 L2 L3 Resistive current 110/20kV åIL = Io Ro OVERCOMPENSATED STATE Co L1 L2 L3 åIL = Io Yo At the beginning of a faulty feeder, the reactive part depends: • On the phase-to-earth capacitance of the feeder • On the tuning degree of the coil • Fault in the long cable feeder moves operation point towards the boundary • Over-compensation of centralized coil emphasizes this effect! Im(Io) 500V LCOIL +Uo Rpar FAULT LOCATION, phase L1 Parallel resistor L1 L2 L3 åIL = Io © ABB Group November 19, 2018 | Slide 55 OPERATE SECTOR Petersen coil Ipar Re(Io) -Uo Yo Io Ipar Io Amount of overcompensation ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks IEFFd [A] 5 10 15 20 25 30 35 40 45 50 55 60 65 70 75 80 85 90 95 100 © ABB Group November 19, 2018 | Slide 56 [A] b b bIIEFFd b[A] EFFd 45 63 72 76 55 10 27 45 56 63 10 15 18 34 45 53 15 20 14 27 37 45 20 25 11 22 31 39 25 30 9 18 27 34 30 35 8 16 23 30 35 40 7 14 21 27 40 45 6 13 18 24 45 50 6 11 17 22 50 55 5 10 15 20 55 60 5 9 14 18 60 65 4 9 13 17 65 70 4 8 12 16 70 75 4 8 11 15 75 80 4 7 11 14 80 85 3 7 10 13 85 90 3 6 9 13 90 95 3 6 9 12 95 100 3 6 9 11100 [A] 55 10 10 15 10 15 15 20 20 IIPar 15IPar 20 20[A] 5 10 1555 20 10 Par [A] bEFFdb b[A]b b b b b I 45 63 63 72 76 76 45 27 72 518 14 27 4510 56 63 63 27 63 45 56 34 27 18 34 53 18 72 34 5615 45 45 53 37 14 27 37 45 14 76 27 6320 37 53 45 11 22 31 39 39 11 79 22 6825 31 59 51 18 27 34 34 81 99 18 7230 27 63 56 16 23 30 30 82 88 16 7435 23 67 60 14 21 27 27 83 77 14 7640 21 69 63 13 18 24 24 84 66 13 7745 18 72 66 11 17 22 22 84 66 11 7950 17 73 68 10 15 20 20 85 55 10 8055 15 75 70 14 18 18 85 55 81 99 60 14 76 72 13 17 17 86 44 81 99 65 13 77 73 12 16 16 86 44 82 88 70 12 78 74 11 15 15 86 44 82 88 75 11 79 75 11 14 14 86 44 83 77 80 11 79 76 10 13 13 87 33 83 77 85 10 80 77 13 87 33 84 66 9081 99 13 77 12 87 33 84 66 9581 99 12 78 11 87 33 84 6610081 99 11 79 b b b b 45 76 27 18 18 14 14 45 63 72 45 27 63 63 45 34 34 27 27 27 45 56 63 45 72 53 56 45 45 37 37 18 34 45 72 56 76 45 63 53 53 45 45 14 27 37 76 63 79 39 68 59 59 51 51 11 22 31 79 68 81 34 72 63 63 56 56 9 18 27 81 72 82 30 74 67 67 60 60 8 16 23 82 74 83 27 76 69 69 63 63 7 14 21 83 76 84 24 77 72 72 66 66 6 13 18 84 77 84 22 79 73 73 68 68 6 11 17 84 79 85 20 80 75 75 70 70 5 10 15 85 80 85 18 81 76 76 72 72 5 9 14 85 81 86 17 81 77 77 73 73 4 9 13 86 81 86 16 82 78 78 74 74 4 8 12 86 82 86 15 82 79 79 75 75 4 8 11 86 82 86 14 83 79 79 76 76 4 7 11 86 83 87 13 83 80 80 77 77 3 7 10 87 83 84 81 81 77 77 3 6 87 987 13 84 84 81 81 78 78 3 6 87 987 12 84 84 81 81 79 79 3 6 87 987 11 84 5 10 15 20 Resistive current from the parallel resistor 45 27 18 14 63 45 34 27 72 56 45 37 76 63 53 45 79 68 59 51 81 72 63 56 82 74 67 60 83 76 69 63 84 77 72 66 84 79 73 68 85 80 75 70 85 81 76 72 86 81 77 73 86 82 78 74 86 82 79 75 HEALTHY 86 83 79 76 87 83 80 77 87 84 81 77 87 84 81 78 87 84 81 79 Earth fault current of the protected feeder IPar [A] 5 10 15 20 I I Par a tan EFFd Amount of undercompensation FAULTY Io Amount of overcompensation ABB EARTH FAULT SEMINAR, 2018 Taking earth-fault protection to the next level Check of correct polarity of Uo and Io Ari Wahlroos. Senior Principal Engineer, ABB Oy, Finland Taking earth-fault protection to the next level Earth-fault protection in compensated networks Check of correct polarity Uo and Io © ABB Group November 19, 2018 | Slide 59 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Petersen coil Check of correct polarity: Uo and Io Im(Io) 2 2 4 6 Typical faulty feeder Io-phasor 8 10 Io © ABB Group November 19, 2018 | Slide 60 4 OPERATION SECTOR Typical faulty feeder Io-phasor, INCORRECT polarity 6 Earth fault inside the protected feeder -Uo 8 10 12 14 Re(Io) DEFLPDEF: • Iocos-moodi • Angle correction 5o • Start value = 1 A Result of incorrect polarity: • No indication in the faulted feeder • Incorrect polarity is ’easy’ to identify 12 14 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Petersen coil Check of correct polarity: Uo and Io Im(Io) 2 2 4 6 8 10 © ABB Group November 19, 2018 | Slide 61 Typical healthy feeder Io-phasor (capacitive) Io 12 14 4 OPERATION SECTOR Healthy feeder Io-phaser, INCORRECT POLARITY 6 Earth-fault outside protected feeder -Uo 8 10 12 Result of incorrect polarity: 14 Re(Io) DEFLPDEF: • Iocos-moodi • Angle correction 5o • Start value = 1 A • No indication in the healthy feeder -> Incorrect polarity is ’difficult’ to identify • Disturbance Recording (DR) analysis of healthy feeders during an earth fault must be conducted! • For example, Uo triggering of DR ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Check of correct polarity: Uo and Io Connection according to manual: +Uo, -Io Validation with primary fault recordings: Best and most secure method (validation of whole measurement chain: CT+VT+relay) Analysis of disturbance records both from faulty AND healthy feeder! Analysis of faulty feeder is not sufficient! Can be used to evaluate accuracy (phase displacement) © ABB Group November 19, 2018 | Slide 62 ABB EARTH-FAULT SEMINAR, 2018 Taking earth-fault protection to the next level Different earth fault types and their challenges Ari Wahlroos. Senior Principal Engineer, ABB Oy, Finland Taking earth-fault protection to the next level Earth-fault protection in compensated networks Taking earth-fault protection to the next level Earth-fault protection in compensated networks Taking earth-fault protection to the next level Earth-fault protection in compensated networks Taking earth-fault protection to the next level Earth-fault protection in compensated networks Classification of single phase earth-faults, affecting parameters Single phase earth-fault (E/F) November 19, 2018 Slide 5 Network parameters Fault parameters Detuning degree Fault resistance Network damping Ignitation moment Network imbalance Fault continuity* Taking earth-fault protection to the next level Earth-fault protection in compensated networks Classification of single phase earth-faults, fault continuity Single phase earth-fault (E/F) Permanent Non-permanent Self-extinguished Continuous Transient Low ohmic November 19, 2018 High(er) ohmic Slide 6 Low ohmic High(er) ohmic Re-striking Low ohmic High(er) ohmic Taking earth-fault protection to the next level Earth-fault protection in compensated networks Classification of single phase earth-faults: Transient E/F • Transient or temporary earth fault is characterized by single or few arc transient(s), which have the ability to self-heal (idea of earth-fault compensation accomplished!) • For transient earth faults it is neither necessary nor desirable to trip the circuit breaker at the substation • Typically not detected by ‘normal E/F protection’, requires ‘Transient E/F’ protection functionality • Long lasting ‘post-fault oscillation may result in unselective operation of E/F protection November 19, 2018 Slide 7 Uo [pu] Uo [pu] Uo [pu] Io [pu] Io [pu] Io [pu] Taking earth-fault protection to the next level Earth-fault protection in compensated networks Classification of single phase earth-faults: Permanent & continuous With higher fault resistance values harmonics and fundamental frequency component is dampened • Damping is determined by fault resistance value and network parameters • ZERO-SEQ. VOLT earth 1xU0 fault needs ZERO-SEQ. VOLT VOLT 1xU0 Detection of high(er) ohmic sensitivity from1xU0 protection, VTZERO-SEQ. & CT Uo [pu] 0 -2 0.4 0.5 0.6 0.7 0.8 RES. CURR. 3xI0 FAULTY FEEDER 1 Io [pu] 0 -1 0.4 0.5 0.6 0.7 0.8 BINARY SIGNALS FAULTY FEEDER FAULTY FEEDER RF = 500 OHM 2 Uo [pu] 0 -2 0.4 0.5 0.6 0.7 0.8 RES. CURR. 3xI0 FAULTY FEEDER 0.4 0.2 0 -0.2 -0.4 0.4 Io [pu] 0.5 0.6 0.7 0.8 BINARY SIGNALS FAULTY FEEDER BLK OP PER UNIT 2 PER UNIT PER UNIT FAULTY FEEDER RF = 0 OHM PER UNIT • PER UNIT In case of solid earth fault (RF = 0 ohm), harmonic components are often included PER UNIT • FAULTY FEEDER RF = 5500 OHM 2 Uo [pu] 0 -2 0.4 0.5 0.6 0.7 0.8 RES. CURR. 3xI0 FAULTY FEEDER 0.1 0.1 0.05 0 0 -0.1 -0.05 0.4 Io [pu] 0.5 0.6 0.7 0.8 BINARY SIGNALS FAULTY FEEDER BLK OP BLK OP Taking earth-fault protection to the next level Earth-fault protection in compensated networks Taking earth-fault protection to the next level Earth-fault protection in compensated networks Classification of single phase earth-faults: Permanent & re-striking • Restriking faults are the most common type of permanent earth faults in compensated networks. • These faults have generally broad frequency content and they are often low ohmic. • They are formed by succession of self-extinguishing faults, where the time duration between recurring reignitions is typically in the order of few tens to some hundreds of milliseconds. • Restriking fault creates highly non-sinusoidal and irregular voltage and current waveforms, which conventional fundamental frequency based methods are not designed for. Restriking, type II Restriking, type I ZERO-SEQUENCE VOLTAGE 1xU0 4 1 2 PER UNIT PER UNIT ZERO-SEQUENCE VOLTAGE 1xU0 2 0 -1 -2 0 0.2 0.4 0.6 0.8 0 -2 -4 1 0 0.05 RESIDUAL CURRENT 3xI0 2 0 -2 -4 0.2 0.4 0.6 TIME (SEC.) 0.2 0.25 0.3 0.25 0.3 2 0 -2 -4 0 0.15 4 ~400 A PER UNIT PER UNIT 4 0.1 RESIDUAL CURRENT 3xI0 0.8 1 0 0.05 0.1 0.15 TIME (SEC.) 0.2 Taking earth-fault protection to the next level Earth-fault protection in compensated networks Taking earth-fault protection to the next level Earth-fault protection in compensated networks Restriking or intermittent earth-fault! Unique fault pattern, every time different Affected by many system and fault parameters Typically a result of insulation failure in cable sheaths, in cable joints or in cable terminations. © ABB Group November 19, 2018 | Slide 14 ABB Intermittent (restriking) earth-fault, typical fault in underground cables Taking earth-fault protection to the next level Earth-fault protection in compensated networks Restriking or intermittent earth-fault! • ‘Piikin’ leveys tyyp. ~ 0.4-0.8 ms • ‘Piikkien’ välinen aika ~ 5-300 ms • Io huippuarvo ~ x 102…103 A verkkoparametrien ja vikapaikan jännitekestoisuuden funktio © ABB Group November 19, 2018 | Slide 16 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks New challenges: Restriking or intermittent earth-faults 0.4 • Unique fault pattern, every time different 0.3 0.2 Io (kA) Uo x 102 (kV) • Affected by many system and fault parameters Io • Pulse width ~ 0.4-0.8 ms • Time between pulses ~ 5-300 ms • Peak amplitude ~ x 102…103 A f(Ictot, K, Re, Utres) Uo 0.1 0 -0.1 -0.2 -0.3 Restriking earth-fault is characterised by repetitive and recurrent of earth-fault arcs with very short duration. This results in highly irregular and intermittent waveforms of residual quantities, which challenges the operation of conventional earth-fault protection functions. © ABB Group November 19, 2018 | Slide 18 UPhfaulty -0.4 Un Ubrk ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks ubrk 20 UA UB UC 0 -20 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 50 UAB UBC UCA 0 -50 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 20 Uo = (UA+UB+UC)/3 0 -20 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 500 IA IB IC 0 -500 0.8 1 1.2 1.4 1.6 1.8 2 2.2 200 2.4 Io = IA+IB+IC 0 -200 -400 © ABB Group November 19, 2018 | Slide 19 0.8 1 1.2 1.4 1.6 1.8 2 2.2 2.4 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Uo> ! FAULTY FEEDER 0.2 0.4 0.6 0 0.2 0.4 0.6 Io (p.u.) 0 0 0.2 0.4 0.6 Time (s) Io OPERATE-AREA ? 0o -Uo Io NON-OPERATE AREA Io OPERATE-AREA © ABB Group November 19, 2018 | Slide 20 ! NON-OPERATE AREA Io> Time (s) Io Uo Io> HEALTHY FEEDER Io (p.u.) • ”Basic” earth-fault protection functions are designed for sinusoidal 50 Hz signals very unstable operating quantity during a restriking E/F! 0o -Uo RISKS FOR PROTECTION MALOPERATION • Healthy feeders: unselective operation • Faulty feeder: unsuccesfull or delayed tripping • May lead to tripping of the busbar E/F protection RECOMMENDATION TO USE DEDICATED FUNCTION FOR RESTRIKING E/F ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Single phase earth-fault may evolve in time… Low current single phase earth-fault (E/F) November 19, 2018 Slide 21 Voltage stress on the two healthy phases Insulation breakdown on other phase High current double earth-fault (cross.country E/F) Taking earth-fault protection to the next level Earth-fault protection in compensated networks – Evolving earth-fault (in cables) • In case restriking E/F is not disconnected, earth-fault may evolve into more serious fault (cross-country E/F or short-circuit) due to successive detoration of insulation ZERO-SEQUENCE VOLTAGE 1xU0 PER UNIT 1 0.5 0 -0.5 -1 0 0.5 1 1.5 2 PER UNIT RESIDUAL CURRENT 3xI0 2 0 -2 0 © ABB Group November 19, 2018 | Slide 22 0.5 Initial damage of insulation 1 1.5 TIME (SEC.) Succesive detoration of insulation 2 Permanent fault ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Taking earth-fault protection to the next level Earth-fault protection in compensated networks PERMANENT E/F © ABB Group November 19, 2018 | Slide 26 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 -20 -22 -24 -26 -28 -30 -32 0.2 0.4 0.6 0.8 Temporary transient over-voltages introduced during re-striking E/F INTERMITTENT E/F 1 1.2 1.4 32 30 28 26 24 22 20 18 16 14 12 10 8 6 4 2 0 -2 -4 -6 -8 -10 -12 -14 -16 -18 -20 -22 -24 -26 -28 -30 -32 0.2 0.4 0.6 0.8 1 1.2 1.4 ABB Taking earth-fault protection to the next level Earth-fault protection in compensated networks Earth-fault protection in a compensated networks is challenging task due to multitude of different possible fault types! Earth-fault pattern in unique every time and may include characteristics from “permanent” and “arcing” faults! November 19, 2018 Slide 27 U0 Io Taking earth-fault protection to the next level Earth-fault protection in compensated networks MOTIVATIONS FOR NEW FUNCTION Contradiction of requirements: – High requirement for sensitivity requires very sensitive settings, – High requirement for selectivity and security; restriking earth faults endanger correct operation of basic EF-protection • Basic E/F functions are not capable in operating selectively during intermittent earth faults • Traditional transient/intermittent functions are not capable in detecting higher ohmic earth-faults © ABB Group November 19, 2018 | Slide 28 Security Sensitivity ABB Novel method taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Reliable and selective protection scheme can be provided, which fullfills set operation speed and sensitivity requirements: • Fundamental frequency based method + Transient based method, OR • Multi-frequency admittance based protection Current based (Io) f=50Hz Fundamental frequency based Uo, Io f=n*50Hz f>>50Hz © ABB Group November 19, 2018 | Slide 29 Harmonic based Transient based DEFxPDEF • Iocos/Iosin • Phase angle Power based (So) WPWDE • Po/Qo Admittance based (Yo) EFPADM • Go/Bo Multifrequency Admittance based MFADPSDE Harmonic based HAEFPTOC Transient-based E/Fprotection against restriking/Intermitte nt earth faults INTRPTEF ’Basic’ E/F protection ’Basic’ + ’Restriking’ E/F protection ’Restriking’ E/F protection ABB Novel method taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Reliable and selective protection scheme can be provided, which fullfills set operation speed and sensitivity requirements: • Fundamental frequency based method + Transient based method, OR • Multi-frequency admittance based protection Current based (Io) f=50Hz Fundamental frequency based Uo, Io f=n*50Hz f>>50Hz © ABB Group November 19, 2018 | Slide 30 Harmonic based Transient based DEFxPDEF • Iocos/Iosin • Phase angle Power based (So) WPWDE • Po/Qo Admittance based (Yo) EFPADM • Go/Bo Multifrequency Admittance based MFADPSDE Harmonic based HAEFPTOC Transient-based E/Fprotection against restriking/Intermittent earth faults INTRPTEF ’Basic’ E/F protection ’Basic’ + ’Restriking’ E/F protection ’Restriking’ E/F protection ABB EARTH-FAULT SEMINAR, 2018 Taking earth-fault protection to the next level Multi-frequency admittance protection (MFADPSDE) Ari Wahlroos. Senior Principal Engineer, ABB Oy, Finland Multi-frequency admittance protection – general presentation 2017-01-25 ”Earth fault locating technology by ABB Finland awarded as the “Network Initiative of the Year 2017” ”An innovative Earth-fault protection and fault indication method developed by ABB in Finland won the Network Initiative of the Year 2017 award. The new technology is very topical, as the share of underground cables and renewable energy production increase. It enhances a grid company’s fault management and thus improves the reliability of power distribution.” The award was presented by Harri Jaskari, Member of Parliament, and Kenneth Hänninen, director responsible for the network business at the Finnish Energy association Novel method taking earth-fault protection to the next level Multi-frequency admittance-based earth-fault protection, MFADPSDE BACKGROUND • Based on deep theoretical understanding of the earth-fault phenomenon • Complemented with practical knowledge gained from numerous field tests and comprehensive disturbance analysis © ABB Group November 19, 2018 | Slide 3 ABB Taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Current (Io) f=50Hz Uo, Io © ABB Group November 19, 2018 | Slide 4 Fundamental frequency based DEFxPDEF • Iocos/Iosin • Phase angle Power (So=Io*Uo) WPWDE • Po/Qo Admittance (Yo=Io/Uo) EFPADM • Go/Bo ’Basic’ E/F protection ABB Taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Current (Io) f=50Hz Fundamental frequency based Power (So=Io*Uo) WPWDE • Po/Qo Admittance (Yo=Io/Uo) EFPADM • Go/Bo Transient-based E/F-protection against transient/restriking/ Intermittent earth faults INTRPTEF Uo, Io f>>50Hz © ABB Group November 19, 2018 | Slide 5 Transient based DEFxPDEF • Iocos/Iosin • Phase angle ’Basic’ E/F protection ’Transient/Restriking’ E/F protection ABB Taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Current (Io) f=50Hz Fundamental frequency based Power (So=Io*Uo) WPWDE • Po/Qo Admittance (Yo=Io/Uo) EFPADM • Go/Bo Transient-based E/F-protection against transient/restriking/ Intermittent earth faults INTRPTEF Uo, Io f>>50Hz © ABB Group November 19, 2018 | Slide 6 Transient based DEFxPDEF • Iocos/Iosin • Phase angle ’Basic’ E/F protection ’Transient/Restriking’ E/F protection ABB Taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Reliable and selective protection scheme can be provided, which fullfills set operation speed and sensitivity requirements: • Fundamental frequency based method + Transient based method, Current (Io) f=50Hz Fundamental frequency based Power (So=Io*Uo) WPWDE • Po/Qo Admittance (Yo=Io/Uo) EFPADM • Go/Bo Harmonic based HAEFPTOC Transient-based E/F-protection against transient/restriking/ Intermittent earth faults INTRPTEF Uo, Io f=n*50Hz f>>50Hz © ABB Group November 19, 2018 | Slide 7 Harmonic based Transient based DEFxPDEF • Iocos/Iosin • Phase angle ’Basic’ E/F protection ’Special’ E/F protection ’Transient/Restriking’ E/F protection ABB Taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Reliable and selective protection scheme can be provided, which fullfills set operation speed and sensitivity requirements: • Fundamental frequency based method + Transient based method, OR • Multi-frequency admittance based protection Current (Io) f=50Hz Fundamental frequency based Uo, Io f=n*50Hz f>>50Hz © ABB Group November 19, 2018 | Slide 8 Harmonic based Transient based DEFxPDEF • Iocos/Iosin • Phase angle Power (So=Io*Uo) WPWDE • Po/Qo Admittance (Yo=Io/Uo) EFPADM • Go/Bo Multi-frequency Admittance based MFADPSDE Harmonic based HAEFPTOC Transient-based E/F-protection against transient/restriking/ Intermittent earth faults INTRPTEF ’Universal’ EF-protection ABB Taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Reliable and selective protection scheme can be provided, which fullfills set operation speed and sensitivity requirements: • Fundamental frequency based method + Transient based method, OR • Multi-frequency admittance based protection Current (Io) f=50Hz Fundamental frequency based Uo, Io f=n*50Hz f>>50Hz © ABB Group November 19, 2018 | Slide 9 Harmonic based Transient based DEFxPDEF • Iocos/Iosin • Phase angle Power (So=Io*Uo) WPWDE • Po/Qo Admittance (Yo=Io/Uo) EFPADM • Go/Bo Multi-frequency Admittance based MFADPSDE Harmonic based HAEFPTOC Transient-based E/F-protection against transient/restriking/ Intermittent earth faults INTRPTEF ’Universal’ EF-protection ABB Taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Reliable and selective protection scheme can be provided, which fullfills set operation speed and sensitivity requirements: • Fundamental frequency based method + Transient based method, OR • Multi-frequency admittance based protection f=50Hz Fundamental frequency based Admittance (Yo=Io/Uo) Uo, Io f=n*50Hz © ABB Group November 19, 2018 | Slide 10 Harmonic based Multi-frequency Admittance based MFADPSDE ’Universal’ EF-protection ABB Taking earth-fault protection to the next level Available protection methods and functions, Relion, Q4/2018 Reliable and selective protection scheme can be provided, which fullfills set operation speed and sensitivity requirements: • Fundamental frequency based method + Transient based method, OR • Multi-frequency admittance based protection Current (Io) f=50Hz Fundamental frequency based Uo, Io f=n*50Hz f>>50Hz © ABB Group November 19, 2018 | Slide 11 Harmonic based Transient based DEFxPDEF • Iocos/Iosin • Phase angle Power (So=Io*Uo) WPWDE • Po/Qo Admittance (Yo=Io/Uo) EFPADM • Go/Bo Multi-frequency Admittance based MFADPSDE Harmonic based HAEFPTOC Transient-based E/F-protection against transient/restriking/ Intermittent earth faults INTRPTEF ’Universal’ EF-protection ABB Multi-frequency admittance protection Taking earth-fault protection to the next level Comparison on the functionality of MFADPSDE with traditional methods in resonant earthed networks Earth-fault type Transient Traditional Iocos Treditional Wischer MFADPSDE © ABB Group November 19, 2018 | Slide 13 Continuous Re-striking/Intermittent Low-ohmic High-ohmic ABB Multi-frequency admittance protection Taking earth-fault protection to the next level MULTI-FREQUENCY ADMITTANCE, MFADPSDE Operation principle and advantages © ABB Group November 19, 2018 | Slide 14 ABB Commissioning tests of multi-frequency admittance 17.-18.5.2017 Primary earth fault tests: restriking earth fault Cumulative Phasor Summing (CPS) tend t end Y osum_ CPS HEALTHY osum (i ) j Im Y osum (i ) Re Y FEEDER: i t start i t start Uo Io Iocos Iocos(CPS) ABB Utilization of harmonics: Multi-frequency admittance HEALTHY FEEDER: Uo Io Iocos Iocos(CPS) ABB Utilization of harmonics: Multi-frequency admittance HEALTHY FEEDER: Uo Io Iocos Iocos(CPS) ABB Utilization of harmonics: Multi-frequency admittance HEALTHY FEEDER: Uo Io Iocos Iocos(CPS) XCoil = ω ∙ LCoil ABB Current supervision: I oCPS HEALTHY FEEDER: 1 Y 1 o stab 1 U oCPS Re Y I 1 o stab 1 o stab j ImY G 1 o stab (Gostab j Bostab ) U PE I 1 oCosstab jI 1 oSinstab ostab Uo j Bostab Io Iocos Iocos(CPS) ABB Multi-frequency admittance protection - Taking earth-fault protection to the next level High sensitivity during high(er) ohmic earth faults! © ABB Group November 19, 2018 | Slide 28 ABB Multi-frequency admittance protection Taking earth-fault protection to the next level Multi-frequency admittance function (MFADPSDE) Single function capable in protection and detection against all kinds of earth faults! • Easy setting principles based on basic network data • The operation characteristic provides universal applicability i.e. it is valid both in compensated and unearthed networks (e.g. Petersen coil is out of service) • Fault direction indication both in operate direction (START/OPERATE) and non-operate direction (BLK_EF), which may be utilized during fault location process • Inbuilt transient detector to identify restriking/intermittent earth faults (INTR_EF), and discriminate them from permanent/continuous earth faults • Dedicated operation mode for alarming-mode of earth-fault protection • Sensitivity basically only limited by network healthy-state residual voltage value (degree of asymmetry): practical sensitivity of several kilo-ohms possible © ABB Group November 19, 2018 | Slide 35 ABB Multi-frequency admittance protection Taking earth-fault protection to the next level MULTI-FREQUENCY ADMITTANCE, MFADPSDE One protection function for all fault types Superior selectivity; dependable and secure Easy to set and configure Applicaple both in compensated and unearthed network Sensitivity up to several kilo-ohms © ABB Group November 19, 2018 | Slide 36 ABB Multi-frequency admittance protection Taking earth-fault protection to the next level Benefits compared with DEFxPDEF + INTRPTEF Simpler engineering Only one function block covers all 1-ph fault cases No need to co-ordination (DEF with INTRPTEF) Simpler setting Same settings are valid for all feeders and both during coil on and coil off (no need for change base angle) Can be determined with basic network data • Better selectivity and security • • • MFADPSDE is designed to operate correctly during restriking earth-fault With DEF, there is a risk for protection maloperation especially on the healthy feeders during restriking earth-fault as DEF is measuring unstable 50Hz component Better dependability and sensitivity • MFADPSDE is based on admittance measurement: measured admittance is not affected by fault resistance. Sensitivity is limited by the system healthy-state asymmetry (healthy state Uo). Practical sensitivity of several kilo-ohms can be achieved. ABB Multi-frequency admittance protection Taking earth-fault protection to the next level Benefits compared with competitors solutions Simpler engineering Only one function block covers all 1-ph fault cases No need to co-ordination (many parallel functions) No need for separate fault type dedicated protection devices (such as transient fault detectors) Simpler setting Same settings are valid for all feeders and both during coil on and coil off (no need for change base angle) Can be determined with basic network data. No need to consider transient magnitudes, etc. • Better selectivity and security • • • MFADPSDE is designed to operate correctly during restriking earth-fault With prior-art 50Hz-methods, there is a risk for protection maloperation especially on the healthy feeders during restriking earth-fault as all prior-art 50Hz methods are measuring unstable 50Hz component Better dependability and sensitivity • • MFADPSDE is based on admittance measurement: measured admittance is not affected by fault resistance. Sensitivity is limited by the system healthy-state asymmetry (healthy state Uo). Practical sensitivity of several kilo-ohms can be achieved. Better than any current (Io) or power (Po) based methods ABB Multi-frequency admittance protection Taking earth-fault protection to the next level Performance is validated with tens of practical field tests and thousands of individual tests: © ABB Group November 19, 2018 | Slide 39 Vattenfall, 2012 FAT Elenia, Vilppula, 2013 ESB Irlanti, 2014 Caruna, Pusula, 2014 Jenergia, Hämeenlahti, 2014 SVV, Lapinlahti, 2014 Linköping, Ruotsi, 2015 VSS, Sundom, 2015 HSV, Ilmalantori, 2015 HSV, Herttoniemi, 2016 Elenia, Orivesi, 2016 Caruna, Sastamala, 2016 SEI-verkot, Seinäjoki, 2017 Caruna, Taivalvaara, 2017 ABB Multi-frequency admittance protection Taking earth-fault protection to the next level Multi-frequency admittance protection, reference installations (2018, Q3) Primary substation, protection application (Relion series) • • • • • Jyväskylän Energia, several substations, Finland Sei-verkot, Kärmeskytö substation, Finland Vaasan Sähkö, several substations, Finland Pohjois-Karjalan Sähkö, several substations, Finland Degerfors Energi AB, Sweden Primary substation, protection application (centralized protection, SSC600) • Caruna, Noormarkku substation, Finland Secondary substation, fault passage indication application (RIO600) • Elenia, Finland (MFA) • Caruna, Finland (MFA) © ABB Group November 19, 2018 | Slide 40 ABB Multi-frequency admittance protection Taking earth-fault protection to the next level Summary Single, ‘Universal’, earth-fault protection function for high impedance earthed (compensated) networks • Covers all single phase earth faults with high reliability, selectivity and sensitivity Easy to configure Total protection coverage Simple to set Cost efficient • Easy to use • Part of normal feeder protection relay Multi-frequency admittance protection Taking earth-fault protection to the next level Multi-frequency admittance protection (MFADPSDE) Relion® series 615 series 620 series 630 series 640 series 615 series RIO600 Interconnec tion protection : REF615 5.0 FP1 L ja N REF620 2.0 FP1 REF630 1.3 REX640 Feeder EF-protection extension package REC615/ RER615 2.0 RIO600 1.7 SIM8F Applikaatio Feeder protection Feeder protection Feeder protection Feeder protection Feeder protection (distribution automation) Fault indication (distribution automation) MFADPSDE x x x x x x November 19, 2018 Slide 42 EARTH FAULT SEMINAR, 2018 Taking earth-fault protection to the next level Multi-frequency admittance protection – Easy settings based on basic network data Multi-frequency admittance protection - Taking earth-fault protection to the next level HEALTHY FEEDER: FAULTED FEEDER: Uo Uo Io Io Iocos Iocos Iocos(CPS) Iocos(CPS) Voltage start value Min operate current Tilt angle Operate delay time ABB Multi-frequency admittance protection - Taking earth-fault protection to the next level Easy setting principles based on basic network data: Voltage start value The setting Voltage start value defines the basic sensitivity of the MFADPSDE be function. To avoid unselective start or operation, Voltage start value must always set to a value which exceeds the maximum healthy-state zero-sequence voltage value, taking into consideration of possible network topology changes, compensation coil and parallel resistor switching status and compensation degree variations. Example of selection of setting ‘Voltage start value’ in order to maximize the earth-fault detection sensitivity based on the resonance curve calculated by the coil controller. X.XX © ABB Group November 19, 2018 | Slide 45 ABB Multi-frequency admittance protection - Taking earth-fault protection to the next level Table. Comparison on setting Operating quantity of MFADPSDE with traditional methods. Traditional Setting ‘Operating quantity’ of method MFADPSDE Amplitude Resistive Adaptive Iosin Iocos Iosin/Iocos When Operating quantity = “Amplitude” is selected, the set minimum operate current threshold (setting Min operate current) is compared to the amplitude of 𝐼𝑜1 𝑠𝑡𝑎𝑏 in the whole defined operate sector. When Operating quantity = “Resistive” is selected, the set minimum operate current threshold (setting Min operate current) is compared to the resistive component of 𝐼𝑜1 𝑠𝑡𝑎𝑏 in the whole defined operate sector. When Operating quantity =“Adaptive” is selected, the method adapts the principle of current magnitude supervision (amplitude or resistive) automatically to the system earthing condition. This is done by monitoring the phase angle of accumulated sum admittance phasor. Multi-frequency admittance protection Taking earth-fault protection to the next level Easy setting principles based on basic network data: Min operate current © ABB Group November 19, 2018 | Slide 47 X.XX The direction of the MFADPSDE function is supervised by a settable current magnitude threshold. The setting Min operate current should be set to value: < p*IRtot, where IRtot is the total resistive earth-fault current of the network corresponding to the resistive current of the parallel resistor of the coil and the natural losses of the system. p = security factor = 0.5…0.7 ABB Multi-frequency admittance protection Taking earth-fault protection to the next level Easy setting principles based on basic network data © ABB Group November 19, 2018 | Slide 48 • The tilt of the operation sector, setting Tilt angle, should be selected based on the measurement errors of the applied residual current and voltage measurement transformers. • Based on practical experience, the most critical source of measurement errors is the measurement accuracy of Io. Especially the accuracy of measurement of phase angle (i.e. phase displacement). • In the compensated networks, the residual current (Io) is typically much lower than rated current of phase current CT. Therefore the preferred and recommended method of measuring the Io is with a dedicated Core Balance CT. Typical and recommended ratio would be e.g. 100/1A • For protection class CT, the phase displacement at low values of current is typically not known. In the standard IEC 61869-2, the phase displacement is not defined for 10P-class. And for class 5P, the phase displacement is only defined at rated primary current. ABB Multi-frequency admittance protection Taking earth-fault protection to the next level Operation logic MFADPSDE supports four operation modes selected with setting ‘Operation mode’: • “General EF”, • Applicable in all kinds of earth faults in high-impedance earthed networks, that is, in compensated, unearthed and high resistance earthed networks. It is intended to detect all kinds of earth faults regardless of their type (transient, intermittent or restriking, permanent, high or low ohmic) and provide definite operate time for protection regardless of actual fault type. • “Alarming EF”, • Dedicated operation mode when fault detection is only alarming • “Intermittent EF” • Operation mode “Intermittent EF” is dedicated for detecting restriking or intermittent earth faults. A required number of intermittent earth fault transients set with the Peak counter limit setting must be detected for operation. Therefore, transient faults or permanent faults with only initial fault ignition transient are not detected in “Intermittent EF” mode. The application of “Intermittent EF” mode is limited to low ohmic intermittent or restriking earth faults. • “Transient EF” • Operation mode “Transient EF” is dedicated for detecting fast transient faults where the fault current stays on only for a very short time. It is recommended method in networks, where network damping has very small value or when parallel resistor of the coil is not used, for example in sub-transmission networks. © ABB Group November 19, 2018 | Slide 49 ABB Multi-frequency admittance protection Taking earth-fault protection to the next level DEFxPDEF vs. MFADPSDE: Same settings DEFxPDEF MFADPSDE Comment Operation Pol reversal Io signal Sel Uo signal Sel Directional mode Voltage start value Operate delay time Correction angle Reset delay time Operation Pol resersal Io signal Sel Uo signal Sel Directional mode Voltage start value Operate delay time Tilt angle Reset delay time Allow Non Dir Measurement mode Pol quantity Enable voltage limit Operating curve type Start value Mult Min operate voltage - Same setting. Function activation. Same setting. Polarity reversal. Same setting. Io measurement: measured or calculated. Same setting. Uo measurement: measured or calculated. Same setting. Operation direction (Fwd/Rev) Same setting. Function Uo-start threshold Same setting. Operate delay time. Same setting. Tolerance against (VT+CT+IED) phase displacement. Same setting. MFADPSDE recommendation 300-500ms. Avoids resetting of protection during intermittent earth-fault. MFADPSDE is always directional (fwd or rev) MFADPSDE is always based on DFT-phasors MFADPSDE is always polarized with Uo MFADPSDE has always Uo-start element enabled MFADPSDE has always Definite timer operation © ABB Group November 19, 2018 | Slide 50 MFADPSDE has fixed minimum Uo voltage limit: 0.01xUn ABB Multi-frequency admittance protection Taking earth-fault protection to the next level DEFxPDEF vs. MFADPSDE: New settings DEFxPDEF MFADPSDE - Operating quantity - - © ABB Group November 19, 2018 | Slide 51 Peak counter limit Start delay time Comment When detected number of earth-fault transient reaches ”Peak counter limit”, fault is identified being intermittent type, output: INTR_EF is activated. Note that INTR_EF is ”nondirectional” i.e. for detection in the faulted feeder only, it must be externally AND:ed with START-output. ”Adaptive” equals simultaneous use of Iocos/Iosin-mode. Operating quantity ”Adaptive” is valid both in compensated and unearthed networks. ”Amplitude” equals Iosin-mode, application is in unearthed networks. Delay of START-output. Default value 30ms is ok. Practical application is only ”Alarming EF”-mode. ABB Multi-frequency admittance protection Taking earth-fault protection to the next level DEFxPDEF vs. MFADPSDE: Different settings! DEFxPDEF Min operate current MFADPSDE Comment Different meaning in DEFLPDEF vs. MFADPSDE!!! In MFADPSDE:n minimum operation current abs(Io) is internally fixed to 0.01xIn. Start value Min operate current Different meaning in DEFLPDEF vs. MFADPSDE!!! In DEF:n ”Start value” is the magnitude of operate quantity, i.e. Iocos. In DEF, one has to consider the damping effect of fault resistance. In MFADPSDE:n ”Min operate current” is the magnitude of operate quantity. But due to admittance based calculatation, the damping effect of fault resistance must not be considered Different meaning in DEFLPDEF vs. MFADPSDE!!! • In MFADPSE ”General EF” equals tripping earth-fault protection application regardless of fault type (transient, intermittent, katkeileva, pysyvä) or fault resistance value. • In MFADPSE ”Intermittent EF” equals protection against intermittent or restriking EF. For ”permanent EF” separate protection function must be applied. • In MFADPSE ”Alarming EF” equals alarming EF application. Operate-output is not activated. Operation mode Operation mode © ABB Group November 19, 2018 | Slide 52 ABB EARTH FAULT SEMINAR, 2018 Taking earth-fault protection to the next level Multi-frequency admittance protection – secondary testing Testing Multi-Frequency Admittance-Based Earth-Fault Protection Function MFADPSDE with Omicron © ABB Group November 19, 2018 | Slide 54 ABB
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