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Distance Protection 7SA522SIPROTEC 4 7SA522 distance protection relay for transmission linesFunction overview1Protection functions Non-switched distance protection with 6 measuring systems(21/21N)2 High resistance ground (earth)-fault protection for single- andthree-pole tripping (50N/51N/67N) Tele (pilot) protection (85) Fault locator (FL)3 Power swing detection/tripping (68/68T)LSP2309-afpen.tif Phase-overcurrent protection (50/51/67) STUB bus overcurrent protection (50 STUB)4 Switch-onto-fault protection (50HS) Over/undervoltage protection (59/27) Over/underfrequency protection (81O/U) Auto-reclosure (79)5 Synchro-check (25) Breaker failure protection (50BF)Control functionsFig. 6/47SIPROTEC 4 7SA522 distance protection relay6 Commands for control of CB and isolatorsMonitoring functionsDescription Trip circuit supervision (74TC)7 Self-supervision of the relayThe SIPROTEC 4 7SA522 relay provides full-scheme distanceprotection and incorporates all functions usually required for theprotection of a power line. The relay is designed to provide fastand selective fault clearance on transmission and subtransmission cables and overhead lines with or without series capacitorcompensation. The power system star point can be solid orresistance grounded (earthed), resonant-grounded via Petersoncoil or isolated. The 7SA522 is suitable for single-pole andthree-pole tripping applications with and without tele (pilot)protection schemes.– The 7SA522 incorporates several protective functions usuallyrequired for transmission line protection.– High-speed tripping time– Suitable for cables and overhead lines with or without seriescapacitor compensation– Self-setting power swing detection for power swingfrequencies up to 7 Hz– Digital relay-to-relay communication for two and threeterminal topologies– Adaptive auto-reclosure (ADT) Measured-value supervision Event logging/fault logging8 Oscillographic fault recording Switching statisticsFront design9 User-friendly local operation with numeric keys LEDs for local alarm PC front port for convenient relay setting Function keys10Communication interfaces Front interface for connecting a PC System interface for connecting to a control system via variousprotocols– IEC 61850 Ethernet– IEC 60870-5-103 protocol– PROFIBUS-FMS/-DP– DNP 3.01112 2 serial protection data interfaces for tele (pilot) protection Rear-side service/modem interface Time synchronization via IRIG B or DCF77 or system interface13Hardware Binary inputs: 8/16/2414 Output relays: 16/24/32 High-speed trip outputs: 5 (optional)15Siemens SIP · Edition No. 7 6/45
Distance Protection 7SA522ApplicationApplication1The 7SA522 relay provides full-schemedistance protection and incorporates allfunctions usually required for the protection of a power line. The relay is designedto provide fast and selective fault clearance on transmission and subtransmissioncables and overhead lines with or withoutseries capacitor compensation. Thiscontributes towards improved stability andavailability of your electrical power transmission system. The power system starpoint can be solid or impedance grounded(earthed), resonant-grounded via Petersoncoil or isolated. The 7SA522 is suitable forsingle and three-pole tripping applicationswith and without tele (pilot) protectionschemes.2345The effect of apparent impedances inFig. 6/48 Single-line diagramunfaulted fault loops is eliminated by asophisticated and improved method whichuses pattern recognition with symmetrical components and loadANSIcompensation. The correct phase selection is essential for selectivetripping and reliable fault location.621/21NDuring network power swings, an improved power swing blocking feature prevents the distance protection from unwanted tripping and optionally provides controlled tripping in the event ofloss of synchronism (out of step). This function guarantees powertransmission even under critical network operating conditions.7891011121315Distance protectionFault locator50N/51N/67NDirectional earth(ground)-fault protection50/51/67Backup overcurrent protectionCost-effective power system management50 STUBSTUB-bus overcurrent stageThe SIPROTEC 4 units are numerical relays which also providecontrol and monitoring functions and therefore support theuser in view of a cost-effective power system management. Thesecurity and reliability of power supply is increased as a result ofminimizing the use of hardware.68/68TPower swing detection/tripping85/21Teleprotection for distance protection27WIWeak-infeed protection85/67NTeleprotection for earth(ground)-fault protection50HSSwitch-onto-fault protection50BFBreaker-failure protection59/27Overvoltage/undervoltage protection81O/UOver/underfrequency protection25Synchro-check79Auto-reclosure74TCTrip circuit supervision86Lockout (CLOSE command interlocking)The local operation has been designed according to ergonomiccriteria. Large, easy-to-read backlit displays are provided.The SIPROTEC 4 units have a uniform design and a degree of functionality which represents a benchmark-level of performance inprotection and control. If the requirements for protection, controland interlocking change, it is possible in the majority of the casesto implement such changes by means of parameterization usingDIGSI 4 without having to change the hardware.The use of powerful microcontrollers and the application ofdigital measured-value conditioning and processing largely suppresses the influence of higher-frequency transients, harmonicsand DC components.Features High speed tripping time Suitable for cables and overhead lines with or without seriescapacitor compensation14FLProtection functions Self setting power swing detection fo frequencies up to 7 Hz Digital relay-to-relay communication for two and threeterminal topologies Adaptive auto-reclosure (ADT)6/46 Siemens SIP · Edition No. 7
Distance Protection 7SA522ConstructionConstruction1Connection techniques and housingwith many advantages½ and -rack sizes2These are the available housing widthsof the SIPROTEC 4 7SA522 relays, referredto a 19" module frame system. Thismeans that previous models can alwaysbe replaced. The height is a uniform245 mm for flush-mounting housings and266 mm for surface-mounting housingsfor all housing widths. All cables can beconnected with or without ring lugs. Plugin terminals are available as an option.LSP2310-afpen.tif45Fig. 6/49Housing widths ½ 19" and 19"678LSP2166-afp.tifLSP2174-afp.tifIt is thus possible to employ prefabricatedcable harnesses. In the case of surfacemounting on a panel, the connectionterminals are located above and belowin the form of screw-type terminals. Thecommunication interfaces are located in asloped case at the top and bottom of thehousing.3910Fig. 6/50Rear view with screw-type terminalsand serial interfacesFig. 6/51Rear view with terminal covers andwiring1112131415Siemens SIP · Edition No. 7 6/47
Distance Protection 7SA522Protection functionsProtection functions1Distance protection (ANSI 21, 21N)The main function of the 7SA522 is a full-scheme distanceprotection. By parallel calculation and monitoring of all siximpedance loops, a high degree of sensitivity and selectivity isachieved for all types of faults. The shortest tripping time is lessthan one cycle. Single-pole and three-pole tripping is possible.The distance protection is suitable for cables and overhead lineswith or without series capacitor compensation.23Mho and quadrilateral characteristicsThe 7SA522 relay provides quadrilateral as well as mho zonecharacteristics. Both characteristics can be used separately forphase and ground (earth) faults. Resistance ground (earth)faults can, for instance, be covered with the quadrilateralcharacteristic and phase faults with the mho characteristic.4Load zone5In order to guarantee a reliable discrimination between loadoperation and short-circuit - especially on long high loadedlines - the relay is equipped with a selectable load encroachmentcharacteristic. Impedances within this load encroachment characteristic prevent the distance zones from unwanted tripping.6Fig. 6/52Distance protection: quadrilateral characteristicFig. 6/53Distance protection: mho characteristicAbsolute phase-selectivityThe 7SA522 distance protection incorporates a well-proven,highly sophisticated phase selection algorithm. The pickup ofunfaulted loops is reliably eliminated to prevent the adverseinfluence of currents and voltages in the fault-free loops. Thisphase selection algorithm achieves single-pole tripping andcorrect distance measurement in a wide application range.78Parallel line compensationThe influence of wrong distance measurement due to parallellines can be compensated by feeding the neutral current of theparallel line to the relay. Parallel line compensation can be usedfor distance protection as well as for the fault locator.9101112137 distance zonesSix independant distance zones and one separate overreachzone are available. Each distance zone has dedicated timestages, partly separate for single-phase or multi-phase faults.Ground (earth) faults are detected by monitoring the neutralcurrent 3I0 and the zero-sequence voltage 3V0.The quadrilateral tripping characteristic permits separate settingof the reactance X and the resistance R. The resistance section Rcan be set separately for faults with and without ground involvement. This characteristic has therefore an optimal performancein case of faults with fault resistance. The distance zones can beset forward, reverse or non-directional. Sound phase polarization and voltage memory provides a dynamically unlimiteddirectional sensitivity.Mho1415The mho tripping characteristic provides sound phase respectively memory polarization for all distance zones. The diagramshows characteristic without the expansion due to polarizing.During a forward fault the polarizing expands the mho circletowards the source so that the origin is included. This mho circleexpansion guarantees safe and selective operation for all typesof faults, even for close-in faults.6/48 Siemens SIP · Edition No. 7Elimination of interference signalsDigital filters render the unit immune to interference signalscontained in the measured values. In particular, the influence ofDC components, capacitive voltage transformers and frequencychanges is considerably reduced. A special measuring method isemployed in order to assure protection selectivity during saturation of the current transformers.Measuring voltage monitoringTripping of the distance protection is blocked automatically inthe event of failure of the measuring voltage, thus preventingspurious tripping.The measuring voltage is monitored by the integrated fuse failure monitor. Distance protection is blocked if either the fuse failure monitor or the auxiliary contact of the voltage transformerprotection switch operates and, in this case, the EMERGENCYdefinite-time overcurrent protection can be activated.
Distance Protection 7SA522Protection functionsFault locator1The integrated fault locator calculatesthe fault impedance and the distanceto-fault. The result is displayed in ohms,miles, kilometers or in percent of theline length. Parallel line and load currentcompensation is also available.2Power swing detection (ANSI 68, 68T)34LSP2311-afp.tifDynamic transient reactions, for instanceshort-circuits, load fluctuations, autoreclosures or switching operations cancause power swings in the transmissionnetwork. During power swings, largecurrents along with small voltages cancause unwanted tripping of distanceprotection relays. To avoid uncontrolledtripping of the distance protection andto achieve controlled tripping in theevent of loss of synchronism, the 7SA522relay is equipped with an efficient powerswing detection function. Power swingscan be detected under symmetrical loadconditions as well as during single-poleauto-reclosures.Fig. 6/545Power swing current and voltage wave forms6Tele (pilot) protection for distance protection (ANSI 85-21)7A teleprotection function is available forfast clearance of faults up to 100 % ofthe line length. The following operatingmodes may be selected:8LSP2312-afp.tif– PUTT, permissive underreaching zonetransfer trip– POTT, permissive overreaching zonetransfer trip– UNBLOCKING– BLOCKING– DUTT, direct underreaching zone transfer trip (together with Direct TransferTrip function)Fig. 6/5510Power swing circle diagramThe carrier send and receive signals are available as binaryinputs and outputs and can be freely assigned to each physicalrelay input or output. At least one channel is required for eachdirection.Common transmission channels are power-line carrier,microwave radio and fiber-optic links. A serial protection datainterface for direct connection to a digital communicationnetwork or fiber-optic link is available as well.7SA522 also permits the transfer of phase-selective signals. Thisfeature is particularly advantageous as it ensures reliable singlepole tripping, if two single-pole faults occur on different lines.The transmission methods are suitable also for lines with threeends (three-terminal lines).9Phase-selective transmission is also possible with multi-endapplications, if some user-specific linkages are implementedby way of the integrated CFC logic. During disturbances in thetransmission receiver or on the transmission circuit, the teleprotection function can be blocked by a binary input signal without losing the zone selectivity. The control of the overreach zoneZ1B (zone extension) can be switched over to the auto-reclosurefunction. A transient blocking function (Current reversal guard)is provided in order to suppress interference signals during tripping of parallel lines.Direct transfer trippingUnder certain conditions on the power system it is necessary toexecute remote tripping of the circuit-breaker. The 7SA522 relayis equipped with phase-selective "external trip inputs" that canbe assigned to the received inter-trip signal for this purpose.1112131415Siemens
Distance protection (ANSI 21, 21N) The main function of the 7SA522 is a full-scheme distance protection. By parallel calculation and monitoring of all six impedance loops, a high degree of sensitivity and selectivity is achieved for all types of faults. The shortest tripping time is less than one cycle. Single-pole and three-pole tripping is possible. The distance protection is suitable for .
