Transformer Protection

TRANSFORMER PROTECTIONIntroduction ‡ A Power Transformer is a vital link in a power transmission system and impact of a transformer fault is more serious than a transmission line outage. ‡ Following are important. ‡ High quality transformer. ‡ Operating the transformer within specified limits of temperature and voltage. ‡ Proper checking and maintaining OLTC. ‡ Providing suitable protective relays and monitoring devices. Insulation Breakdown Main causes of this are ‡ Aging of insulation due to over temperature during long time. ‡ Contaminated oil. ‡ Corona discharges in the insulation. ‡ Transient overvoltages due to thunderstorms or switching in the network. ‡ Current forces on the windings due to external faults with high current. Aging of Insulation ‡ Aging of insulation is a function of time and temperature. ‡ Part of the winding operated at highest temperature undergoes greatest deterioration. ‡ Improved cooling of transformer helps avoid accelerated aging of the insulation. Overheating due to overexcitation ‡ The overexcited transformer flux is forced through metal tank and other unlaminated parts of the transformer and result in heating up. ‡ Curve shows IEEE general guide for permissible short time over excitation. ‡ To get correct representation V/Hz relay should be connected to PT measuring voltage of an untapped transformer winding. Oil contamination and leakage ‡ Quality of oil should be checked to ensure dielectric strength at site. ‡ Silica get breather helps avoid moisture. ‡ Oil level monitored to avoid breakdown of insulation. Fundamental of differential protection Basic consideration Type of transformer Vector Requirement of CT Type of differential Fundamental of differential protection Basic consideration TYPE of transformer Generator transformer Sub station transformer Furnace transformer Rectifier transformer Fundamental of differential protection Basic consideration Vector Phase shift Fundamental of differential protection Basic consideration CT Ratio Class Polarity Connection Fundamental of differential protection Types of differential High impedance differential::Here a high impedance is added to relay circuit to prevent relay operation due to CT saturation under through fault conditions.This is very sensitive and fast operating for internal faults. Biased differential :Here the operation depends upon differential current exceeding the bias current. The bias characteristics is variable so that it is applicable to a wide variation in transformer design and configuration. This bias slope is set to stabilize The protection for small differential currents,which flow due to tap changer variation and CT tolerance under through fault conditions. Harmonic restraint Harmonics present in transformer charging in rush current Reduced Cooling ‡ Forced cooling systems should be supervised to get alarm. ‡ Oil temperature should be watched and appropriate action taken if transformer gets overheated. Under Impedance Relay ‡ Overcurrent relays are not suitable for system transformer connecting two networks or in networks with a large difference between maximum and minimum short-circuit fault MVA. ‡ Under impedance relay used should be having same reach for two and three phase faults. ‡ Harmonic Restraint Overcurrent Relay ‡ Overcurrent relay with second harmonic restraint can be used which will be stable for magnetizing inrush. Ground Fault Protection ‡ Low impedance residual overcurrent relays or harmonic restraint overcurrent relays can be connected according to connection A. ‡ Should be delayed to give chance for other protections in the network to operate. ‡ They act as slow back up for transformer differential relays. High Impedance Restricted Earth fault Relay ‡ Provides sensitive high speed restraint protection. ‡ Vk > 2 Us. ‡ CT¶s should be dedicated and having identical turns ratio. ‡ The combination of relays on the same CT core should be avoided. ‡ Due to impedance of REF relay differential relay may not get enough current for operation for a phase-ground fault. ‡ Non-linear resistors should be connected in parallel with high impedance relay. This reduces the high peak voltage which can be developed during an internal fault. ‡ The interconnected secondary circuit of the CT should be grounded at only one point. Overexcitation Protection ‡ Overexcited transformers become overheated and damaged. ‡ V/Hz overexcitation relay is required for transformers which may be operated at too high voltage or low frequency. ‡ Especially GT can be overexcited during acceleration and deceleration of turbine. ‡ Ratio should not exceed 1.1 times the ratio of rated voltage and frequency of the transformer. Monitors ‡ Monitors are very important devices which detect faults and abnormal service conditions which may develop into fault. Gas Detector Relay ‡ During fault, arching occurs releasing gas. ‡ Gas collected in alarm device gives alarm. ‡ Can detect a slowly developing fault before it becomes more serious. ‡ Trip devices responds to the high flow of oil which occurs during the sudden occurrence of a serious fault. Temperature Monitoring ‡ Transformer can stand short time overload upto 1.5 times the rated. ‡ Overcurrent relays cannot be used for overload monitoring as they have to be set above the set short time overload. ‡ Oil temperature and winding temperature therefore provide better monitoring. ‡ Static thermal relays with characteristic matching can also be used. ‡ Other devices used include ‡ Pressure relay for OLTC ‡ Oil level monitor ‡ Silica gel dehydrating breather. Fault Currents ‡ The reactance decreases rapidly for fault close to neutral. ‡ Primary fault current for ground fault between 0-40% from neutral is below 1.5In and therefore O/C relay will not be able to detect this. ‡ Primary current is approximately proportional to square of the short circuited fraction of the winding. Turn-to-turn Faults ‡ Turn to turn faults between a few turns is difficult to detect by current measuring relays. Fault current is of the order of rated current when 2 to 4% of the turns are short circuited. ‡ The current in the short circuited loop is high (50-100 times In) and causes local damage and release of gas. ‡ Therefore rate of rise of pressure relay may detect this fault. Protective Relays Used Protective relays limit the damage in case of fault and monitors to prevent the fault. Therefore fast and reliable protective relays should be used. Normal protections used are For transformers larger than 5 MVA ‡ Gas detector relay (Buchholz) ‡ Overload protection (thermal relays or temperature monitoring relays) ‡ Overcurrent protection ‡ Ground fault protection ‡ Differential protection ‡ Pressure relay for tap-changer compartment ‡ Oil level monitor Transformers smaller than 5 MVA - Gas detector relay (Buchholz) - Overload protection - Overcurrent protection - Ground fault protection Differential Relay ‡ The protective zone of a Differential relay includes faults in transformer, faults on Buses or cables between the CT and transformer. Therefore it has a large protective zone than a gas detector relay. ‡ A transformer differential relay must be able to cope with the following conditions. 1. Magnetizing inrush current: This is developed when voltage is returning to normal after a line fault and depends on - The size of the power transformer - The source impedance - The magnetic properties of the core material - The remanence of the core - The moment when the transformer is switched in The magnitude can be 5-10 times the rated current when switching is done on outer winding of the transformer and 10-20 times rated current when done on the inner winding. ‡ Damping of inrush current depends on total resistance of source network and lasts for few seconds. ‡ Inrush can also develop in an energized transformer when a parallel transformer is switched. (The damping of the combined inrush current will then be less than normal and inrush may last for several minutes) ‡ 2nd harmonic restraint prevents unwanted operation of the relay due to inrush is prevented. Inrush current test 2. Normal service: ‡ Differential current flows due to excitation current of transformer, ratio errors in CT and predominantly due to position of tap changer. ‡ A setting 15% higher than mismatch is usual. 3. Internal Faults: ‡ Operating time of typical differential relay(ABB RADSB relay ) for a fault current of 5 times the rated current is 27ms. ‡ Unrestrained operation circuit to speed up the operation for a high fault current 8ms at 10 times the set operating current. Recommended Setting for Unrestrained Operation: Power Rated Power Transformer Connection (1) <10 MVA Yy Yy Yd Dy Dy 10-100 MVA >100 MVA <100 MVA >100 MVA Recommended setting *In when energizing from HV Side 20 13 8 13 13 8 LV Side 10 13 8 13 20 13 Setting of 20*In required when large through fault currents can saturate the CTs and causes a large differential current for 1 & 1/2 CB arrangement. 4. External Faults: ‡ For faults outside the protective zone of the relay a relatively large differential current can occur due to position of the tap changer and differences between the CTs. ‡ The differential relay should not operate for this differential current. ‡ The differential relays are provided with a through-fault restraint circuit which makes the relay operate for a certain % differential current related to the current through the transformer. Restraint characteristic Use of Auxiliary CTs: ‡ Aux. CTs of Y are required even for YY transformer to prevent any operation of relay for external ground fault. ‡ For Y Power transformer, aux. CTs are required for balancing of currents and for correction of phase angles. ‡ Aux CTs are recommended on all sides of the transformer so that same time is taken for saturation for all the inputs. ‡ Connection of aux. CTs will depend on the connection of the Power transformer. Differential Protection for Auto-transformers: ‡ Delta winding may or may not be connected to the network. If not connected CTs are not required. ‡The differential relay will protect the main winding as well as the delta winding. ‡High impedance relay can be used by applying CTs in the neutral point of the main winding. ‡ The relays protect the main winding but not the delta connected wdg. ‡ All CTs should have the same ratio and auxiliary CTs can not be used. Saturation voltage of all the CTs should be at least twice the selected operating voltage. Overexcitation: ‡ For an overvoltage of 20%, the excitation current can increase above the pick-up level of differential relay. ‡ An overexcited condition is not a transformer fault and hence the differential relay should not operate. ‡ If differential relay operates valuable time will be wasted on the investigation of the transformer. ‡ 5th harmonic restraint will prevent the tripping for Overexcitation as overexcited condition results in pronounced 5th harmonic component. Time Overcurrent Relays: ‡ Used on all feeding circuits of a transformer to provide back-up to differential relay and relays on the load side of transformer. ‡ An instantaneous highset overcurrent element is normally used to give fast fault clearance to severe faults. ‡ Time Overcurrent relay is set to 150% of the rated current and time delay must be set long enough to avoid tripping due to magnetizing inrush. ‡ The instantaneous element should be set to about 25% above the maximum through fault current and above the maximum inrush current. With this setting instantaneous tripping is obtained only for severe faults on the feeding side of the transformer. Relay operates delayed for faults on the remaining parts of the windings and for faults on the load side of the transformer. TRANSFORMER PROTECTION TERMINALS Historical evolution      electromechanical single function static single function digital single function digital multifunction relays numerical multifunction relays numerical multifunction systems Comparison of technologies conventional ‡ protection functions realised with different HW ‡ Quantity and types of protection func. fixed and limited ‡ HW-extensions difficult ‡ No. of CT's and PT's higher ‡ Requirements to primary transformers higher numerical ‡ fixed HW prot.functions realised with SW ‡ Complete library of func. available ‡ Adaptation by SW ‡ No.of CT's and PT's lower ‡ Requirement to primary transformers lower Comparison of technologies conventional ‡ Settings and operation locally ‡ no documentation ( only hand-made) ‡ Only binary information ‡ Periodical tests necessary numerical ‡ Settings and operation locally or remote ‡ Self-documentation of all settings and events etc. ‡ Numerical information, meas..values, events, etc. ‡ Selfsupervision and test functions reduces maintenance. ‡ Five different types only ‡ Various spare parts Comparison of technologies conventional ‡ integration to control systems difficult ‡ only protection ‡ only protection ‡ fixed solution numerical ‡ integration to control systems possible ‡ integrated protection and control possible ‡ monitoring with available information possible ‡ extension and new developments possible --> open architecture Generator Terminal Transformer Terminal Control Terminal Line Terminal M G Generation Transmission Distribution Load Station Automation System LON SPA IEC 870-5-103 IEC 1375 Line protection Transformer protection Software Library Generator protection Human-machinecommunication R Units Bay C E Control IEC 1375 Automation Remote Input/Output Unit  Complete library with functions for bay control, monitoring, protection of generators, transformers.  Software and hardware proven and well introduced. Extremely powerful and cost efficient solutions for MV and HV applications.  Selective Protection of: ‡ Two or Three winding Transformer ‡ Auto Transformers ‡ Generator-Transformer unit Detection of Faults: ‡ All phase faults ‡ Earth faults at solidly or Low impedance grounded systems ‡ Inter-turn faults ‡ No interposing CT's ‡ Standard wiring diagram ‡ Inputs for external functions (Buchholz, temperature sensors) available ‡ Programmable indication of tripping and signaling ‡ Indication of measuring values ‡ Continuous self-monitoring ‡ Modular SW protection functions ‡ 4 serial interfaces: - one front for local communication (PC) - one rear for remote communication - two others (spare) Compact Design Flexible input and output configuration Open communication strategy 5 7 4 4 4 4 321 6 1) Analog input unit up to 6 transformer 2) Digital/Optical unit 3) CPU with serial port 4) Binary input/output unit R Units Bay 5) Communication PCMCIA 6) Mother Board 7) Power Supply Hardware concept Interbay bus 1 Analog input module, up to 9 input transformers for AC voltage and current CPU Binary I/O modules (max. 56 binary inputs, max. 32 binary outputs) Communication interface for the interbay bus (PC-Card) Connection module Supply module Communication interface for the process bus (MVB PC-Card) 3 4 5 5 7 6 4 4 4 4 381 6 7 8 Process bus RIO580 R Units Bay Up to 1024 binary I/Os Hardware concept DC +5V A/D DSP DPM CPU 486DX SW-Key +15V -15V +24V DC AC Power Supply Remote I/O Remote I/OTrip Outputs Trip Remote I/O Sign. Outputs Outputs Trip Sign. Outputs Bin. Outputs Sign.Inputs Bin. Outputs Inputs Bin. Inputs Trip Trip Outputs Trip Outputs I/O Trip Sign. Outputs / Sign. I /IOO Outputs Outputs Ports Sign. Ports Outputs O I/ Sign. Outputs Ports Bin. Outputs Ports Bin. Inputs Bin. Inputs Bin. Inputs Inputs FLASH EPROM PC-Card Tranceiver P C C A R D a Process bus IEC1375 (MVB) b PC-Card c RAM LON d e.g. LON LED's RS Serial 232 Controller RS Serial 232 Controller SCS SMS SPA / IEC870-5-103 (VDEW6) MMC Hardware concept RX Tx DC +5V +15V -15V +24V Power DPM A/D DSP CPU 486DX SW-Key DC Supply AC Remote I/O Remote I/OTrip Outputs Remote I/O Trip Sign. Outputs Outputs Trip Sign. Outputs Bin. Outputs Sign. Inputs Bin. Outputs Inputs Bin. Inputs A/D DSP DPM Trip Trip Outputs Trip Outputs I/O Trip Sign. Outputs / Sign. I /I OO Outputs Outputs Ports Sign. Ports Outputs O I/ Sign. Outputs Ports Bin. Ports Outputs Bin. Inputs Bin. Inputs Bin. Inputs Inputs FLASH EPROM PC-Card Tranceiver P C C A R D a Process bus IEC1375 (MVB) b PC-Card c RAM LON d e.g. LON LED's RS Serial 232 Controller RS Serial 232 Controller SCS SMS SPA / IEC870-5-103 (VDEW6) MMC Signal data flow S A/I MUX H A/D Analog to digital conversion MMI SCS/ SMS COM DSP I> U< Z< 1 DiffGen on 2 Current on 3 BinInp 2 off COM Numerical signal processing etc. Trip B/I etc. Binary signal B/O processing Typical tripping time Analog input isolation Low pass Shunt filter Amplifier Algorithm and Logic processor Z< I> I etc Binary output isolation FUPLA Digital filter A/I b b b 0 3 MUX S H A/D b b b 7 B/O etc 9 4 2 0 ms 0 ms 3 ms 5 ms 12 ms 21 ms 25 ms Software Library I> 51 I 87G U> 59 Z< 21 U0> 64S I>> 50 I 87T U< 27 X< 40 CTRL I>U< 51-27 U 60 ITH 49 U/f 24 P<32 I> 51 I 87G U> 59 Z< 21 U0> 64S I>> 50 I 87T U< 27 X< 40 CTRL I>U< 51-27 U 60 ITH 49 U/f 24 P<32 I> 51 I 87G U> 59 Z< 21 U0> 64S I>> 50 I 87T U< 27 X< 40 CTRL I>U< 51-27 U 60 I TH 49 U/f 24 P<32 I2 46 F<> 81 Ucos 78 I2 46 F<> 81 Ucos 78 I2 46 F<> 81 Ucos 78 Logic Timer Counter Logic Timer Counter Logic Timer Counter Function Library Metering (UlfPQ) Frequency (81) Overexcitation with Inverse time delay (24) Overexcitation (24) Instantaneous Overvoltage (27/59) Definite time Over and Under Voltage (27/59) Inverse time Overcurrent (51) Instantaneous Overcurrent (50) Definite time Over and Under Current (51DT) Thermal overload (49) Restricted Earth Fault (64) Transformer-differential 2 or 3 Winding (87T) Function Library 4 parameter sets Counter, Timer MONITORING AND AUXILIARY FUNCTIONS Logic's (OR, AND, RS-FF) Remote Inputs and Outputs Additional I/O units Operating values I, U, P, Q, f Event recording Disturbance recorder Self supervision Remote communication Human Machine Interface Local Display unit Software concept CPU Capacity I> 51 I 87 L P<P<32 Z< 21 U< 27 3 I0 67N Ucos 78 eg. SM300 Protection Library Fupla I> 51 I TH 49 U> 59 Z< 21 AR 21 SC 25 I>> 50 I 87 L U< 27 I 60 U 60 Ucos 78 Binary Signal Trans. Hardware-key 3 I0 67N U >> 59 P<32 Dist. Rec. FUP1 FUP1 FUP1 FUP4 FUP1 FUP1 Logics Timer e.g. Z < (Distance) need 50 % RE21604 HMI functionality ‡ LED-displays ‡ Measurand display ‡ Event list ‡ Operating instructions ‡ Disturbance recorded information ‡ Self supervision ‡ Acknowledgement functions ‡ Optical connector for external HMI HMI functionality LED indications Availability Start Operation Measurand display Analog channels (amplitude, angle, frequency) Functional measurands (e.g. differential current) Binary signals (I/O signals, tripping) Event list (tripping values only, e.g. distance to fault) Operating instructions HMI functionality Disturbance recorder information Number of recorded events and date Diagnostics Operating status of the unit Operating status of the interbay bus Operating status of the process bus Acknowledgement functions Resetting the LED's Resetting the latching outputs Event erasing Warm start Transformer Differential Protection (87T) Differential protection of two or three winding power transformers & generator/transformer units. Features: ‡ Non-linear, current dependent operating characteristic. ‡ High stability during through faults and in the presence of CT saturation. ‡ Short tripping times. ‡ Three phase measurement. ‡ Inrush current restraint. ‡ using the second harmonic. ‡ detection of the highest phase current. ‡ detection of the load current to determine whether the transformer is energized or not. ‡ Compensation of phase group. ‡ Compensation of CT ratio. ‡ DC current component filter and harmonic filter. Inputs & Outputs Analogue Inputs:  Current ( 2 or 3 sets of 3 inputs) Binary inputs:  Blocking Binary Outputs: Tripping  R phase trip  S phase trip  T phase trip  Measurements: R phase summation current  S phase summation current  T phase summation current  R phase restraining current  S phase restraining current  T phase restraining current  Transformer Differential for 2-windings A D AI 1,2,3 DIFF A D AI 7,8,9 Transformer Differential for 3-windings AI 4,5,6 A D AI 1,2,3 DIFF D A A D AI 7,8,9 Operating Characteristic: I1 I IN 3 Operation 2 Operation for I¶1 <b IN or I¶2 IN 1 v g 1 b 2 Restraint <b I( = | I 1 + I 2 + I 3 | Operating (diff.) current Protected unit I2 I3 IH = = 0 I¶1 * I¶2 * Cos E for Cos E u 0 Restrain current for Cos E < 0 Where I¶1 = greatest of I 1 , I 2 , I 3 I¶2 = I 1 + I 2 + I 3 - I¶1 IH IN E = ( I¶1 - I¶2 ) 3 Fault outside protected zone Low short circuit current Load I < (1.5...3) * Irated I1 I2 (I 4 cos E = 1 3 2 v=50% 1 g 1 2 3 4 5 IH IH ! I1 y I2 y cos E IH = I1 = I2 = ILoad < (1.5...3)*Irated Fault outside protected zone High short circuit current Isc I > (1.5....3) * Irated I1 I2 (I v= infinite 4 cos E = 1 3 2 1 IH = I1 = I2 g 1 2 3 4 5 IH v=50% I ! I1 y I2 y cos b Fault inside protected zone I1 I2 (I 4 3 2 cos E < 0 IH = 0 1 g 1 2 3 4 5 IH Thermal Overload Protection (49) Thermal overload protection with accurate thermal image of the protected unit Features: ‡ 1st order thermal model ‡ Alarm and tripping stages ‡ Adjustable initial temperature ‡ Single or three-phase measurement ‡ Maximum value detection for three-phase measurement ‡ Temperature rise calculated 40 times for each thermal time constant setting 49 Inputs & Outputs Analogue Inputs:  Current Binary inputs:  Blocking Binary Outputs: Alarm  Tripping  Measurements: Temperature rise  Power dissipation  Current  Definite time Over & Under Current (51DT) General purpose current function for Phase fault protection and Back-up protn. Features: ‡ Single or three-phase measurement ‡ 2nd harmonic restraint for high inrush currents ‡ Insensitive to DC component ‡ Maximum respectively minimum value detection in the three-phase mode ‡ May also be used as REF protection with additional hardware I<> 51 Inputs & Outputs Analogue Inputs:  Current Binary inputs:  Blocking Binary Outputs: Pick-up  Tripping  Measurements:  Current amplitude Setting Parameters: ‡ Delay: Time between the function picking up and tripping ‡ I-Setting: Pick-up current setting ‡ MaxMin: Over or Under current ‡ NrOfPhases: 1ph or 3ph measurement ‡ CurrentInp: Analog current input channel ‡ BlockInp: Input for blocking the function ‡ Trip signal: Tripping signal ‡ Start signal: Pick-up signal Instantaneous Over Current (50) General current monitoring with instantaneous response Features: ‡ Maximum or Minimum function (over & under current) ‡ Process instantaneous values and is therefore fast and largely independent of frequency ‡ Single or three-phase measurement ‡ Stores the peak value following pick-up ‡ Maximum value detection in the three-phase mode ‡ Adjustable lower frequency limit fmin I<> 50 inputs & Outputs: Analogue Inputs:  Current Binary inputs:  Blocking Binary Outputs: Pick-up  Tripping  Measurements:  Current amplitude (only available if function trips) Setting Parameters: ‡ Delay: Time between the function picking up and tripping ‡ I-Setting: Pick-up current setting ‡ f-min: Minimum frequency for which measurement is required ‡ MaxMin: Over or Under current ‡ NrOfPhases: 1ph or 3ph measurement ‡ CurrentInp: Analog current input channel ‡ BlockInp: Input for blocking the function ‡ Trip signal: Tripping signal ‡ Start signal: Pick-up signal Inverse time Over Current (51) Overcurrent function with time delay inversely proportional to the current and definite minimum tripping time (IDMT) Features: ‡ Operating characteristic according to British standard 142 ‡ Single or three-phase measurement ‡ Detection of the highest phase value in the three-phase mode I > 51 ‡ Wider setting range than specified in B.S.142 Inputs & Outputs Analogue Inputs:  Current Binary inputs:  Blocking Binary Outputs: Pick-up  Tripping  Measurements:  Current amplitude Setting Parameters: ‡ c-setting: Select operating char. According to BS142 or RXIDG char. ‡ k1-Setting: Time grading ‡ I-Start : Pick-up current at which the characteristic becomes active ‡ MaxMin: Over or Under current ‡ t-min: Definite minimum tripping time ‡ NrOfPhases: Defines the number of phases measured ‡ CurrentInp: Analog current input channel ‡ IB-setting: Base current for taking account of differences of rated current ‡ BlockInp: Input for blocking the function ‡ Trip signal: Tripping signal ‡ Start signal: Pick-up signal Definite time Over & Under voltage (27/59) Standard voltage applications (overvoltage & undervoltage function) Features: ‡ Single or three-phase measurement ‡ Maximum value, respectively minimum value, detection for three-phase measurement ‡ DC component filter ‡ Harmonic filter U<> 59/27 Inputs & Outputs Analogue Inputs:  Voltage Binary inputs:  Blocking Binary Outputs: Pick-up  Tripping  Measurements:  Voltage amplitude Setting Parameters: ‡ Delay: Time between the function picking up and tripping ‡ V-Setting: Voltage setting for tripping ‡ MaxMin: Over or Under voltage selection ‡ NrOfPhases: Number of phases included in the measurement ‡ VoltageInp: Analog input channel ‡ BlockInp: Input for blocking the function ‡ Trip signal: Tripping signal ‡ Start signal: Pick-up signal Instantaneous Overvoltage (27/59) General voltage monitoring with instantaneous response (over & undervoltage) Features: ‡ Processes instantaneous values and is therefore fast and largely independent of frequency ‡ Stores the peak value following pick-up ‡ Single and three-phase measurement ‡ Maximum value detection in the three-phase mode ‡ Adjustable lower frequency limit fmin U>> 59/27 Inputs & Outputs Analogue Inputs:  Voltage Binary inputs:  Blocking Binary Outputs: Pick-up  Tripping  Measurements:  Voltage amplitude (only available if function trips) Setting Parameters: ‡ Delay: Time between the function picking up and tripping ‡ V-Setting: Pick-up voltage setting ‡ f-min: Minimum frequency for which measurement is required ‡ MaxMin: Over or Under voltage setting ‡ NrOfPhases: Defines whether 1ph or 3ph measurement ‡ VoltageInp: Analog voltage input channel ‡ BlockInp: Input for blocking the function ‡ Trip signal: Tripping signal ‡ Start signal: Pick-up signal Overexcitation (24) Protection of generators and power transformers against excessive flux Features: ‡ Evaluation of the voltage/frequency ratio ‡ Single phase measurement ‡ Definite time delay ‡ Determination of frequency from the complex voltage vector U/ f 24 ‡ Over or Underexcitation mode ‡ Insensitive to DC components & harmonics Inputs & Outputs Analogue Inputs:  Voltage Binary inputs:  Blocking Binary Outputs: Pick-up  Tripping  Measurements: Voltage / frequency  frequency  Setting Parameters: ‡ Delay: Time delay between the function picking up and tripping ‡ V/f- setting: Setting of the voltage/frequency ratio for tripping ‡ MaxMin: Over or Under fluxing setting ‡ VoltageInp: Analog voltage input channel ‡ BlockInp: Input for blocking the function ‡ Trip signal: Tripping signal ‡ Start signal: Pick-up signal Overexcitation with Inverse time delay (24) Protection of generators and power transformers against excessive flux, especially in heavily loaded non-laminated metal parts, and the associated excessive heating of the unit. Features: ‡ Evaluation of the voltage/frequency ratio ‡ Single phase measurement ‡ Inverse time delay according to U/f ratio ‡ Determination of frequency from the complex voltage vector U/ f 24 ‡ According to IEEE guide C37.91-1985 ‡ Insensitive to DC components & harmonics Inputs & Outputs Analogue Inputs:  Voltage Binary inputs:  Blocking Binary Outputs: Pick-up  Tripping  Measurements: Voltage / frequency  frequency  Frequency (81) Under and Overfrequency, Load shedding Features: ‡ Measurement of one voltage ‡ Frequency calculation based on the complex voltage vector ‡ Undervoltage blocking ‡ Insensitive to DC components & harmonics Inputs & Outputs Analogue Inputs:  Voltage Binary inputs:  Blocking Binary Outputs: Under voltage blocking  Start  Trip  Measurements: Frequency  Voltage  Metering (UIfPQ) Measurement of voltage,current,real & apparent power and frequency. Features: ‡ Single phase measurement ‡ Phase-to-ground or optionally phase-to-phase voltage measurement ‡ Suppression of DC components and harmonics in current & voltages ‡ Compensation of phase errors in main and input CT¶s and VT¶s Inputs & Outputs Analogue Inputs: Voltage  Current  Binary inputs:  none none Binary Outputs:  Measurements:  Voltage (unit UN)  Current (unit IN)  Real power (unit PN (P))  Apparent power (unit PN (Q))  Frequency (unit Hz) The right information for the right person at the right time SMS Remote Substation Monitoring System On-demand information SCS Substation Control System On-line information SMS Local Substation Monitoring System On-demand information TERMINAL Remote communication and time synchronisation GPS-Clock GP 1  ACQ V1 LOCK AT ELLIT CONT OLLED CLOCK E VP Modem N OR M A L OP E R A TION WE D 1 1 .1 2 .1 9 9 M E Z 1 1 . 2 .2 V 2 > YN M ENU CLR ACK NEXT INC MEINBERG ABB trö As ¨ r I 1000 Brown Boveri FA ULT 1 3 Minute pulse 12 3 ABB etwork rtner A G RE T 31 * ABB etwork rtner A G RE T 31 * 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 C E RE.316 54 32 1  ¤ £¢ 2 ri l Loc l  ¥ © ¨§¦ ¤ ¡  0) ¥  (' & !! P WE ¢ " $ % # #  %     Switch SRIO SPA-LOOP C E Remote communication and diagnostics ‡ Brings a terminal to the user - evaluations - disturbance clarifications - diagnostics - change and control of relay setting - etc. TERMINAL Event recorder Last specified number of events stored Event-No., Date, Time, Funct.-No........... Selectable information Function outputs (Start / Trip and special outputs) Binary inputs Trip-values Status ON/ OFF per event Absolute and relative time (after GFC fulfillment) Disturbance recorder 9 analog channels 16 binary channels (function outputs, binary inputs) 12 function measurements (e.g Idelta, I2, Z ) Total record time 5s Pre-Event 400ms,Event 3000ms, Post-Event 400ms Selectable triggering (GFC, trip or functions and binary inputs) Stop on full or overwrite mode Disturbance Recorder - Recording times t pre tf t lim tp t pre tf t p1 t lim Pre-fault time (0.04- 0.40 sec) Fault time Post-fault time (0.1 - 3.0 sec) Time limit for total recording (0.5 - 4.0 sec) Selfsupervision Memories Read/Write comparison Checksum function Program Processing Watchdog functions External and internal Power supply Tolerance check DC +5V +15V -15V +24V A/D-Conversion continuous conversion of 2 reference signals A/D DSP CPU 486 SW-Key Power DC Supply AC FLASH EPROM 3ph-Voltages and-Currents Symmetry check PC-Card IEC 1375 a Trip Outputs I/O Sign. Outputs Ports Bin. Inputs Transceiver RAM P C C A R D Process bus b PC-Card c LON d LON Signal Transfer Error correction coding MMC LED's RS232 Serial Cont. RS232 RS232 Serial Cont. RS232 SPA / IEC 870-5-103 Serial Data Transfer Hamming distance 4 to 6 by frame format definition, 16 bit CRC or check sum+parity bit Test function Password protected  Test protection functions  send a numerical value to each function  test characteristic setting and related outputs  Test signaling relays  Test tripping relays  Test LED's  Advantages ‡ Self monitoring ‡ Long term stability ‡ Event recorder ‡ Self documentation ‡ Number of CT cores reduced ‡ User designed performance ‡ Selectable protection functions ‡ Facility for communication to SMS/SCS REFERENCES ABB manuals Alsthom manuals Easun Reyrolle manuals Art & science of protective relaying by Russell Mason