Technical Reference - Siemens Power Solutions
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1. 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference 3V0 p Elem LL T On Enabled Off Disabled Elem Inhibit E F Dir En J Elem Dir 4 Non Dir Forward Elem Characteristic Elem Setti Elem Multiplier Elem Reset Delay start trip Reverse EarthFwd Elem Starter p Elem Trip p If directional elements are not present this block is omitted and the E F Dir En signal is set TRUE E F Dir En EarthRev P300018 Voltage Protection Functions NVD Figure 2 3 2 1 3 2 Specification Element Parameters Functional Diagram for Neutral Voltage Displacement Element The element will take the following parameters unless otherwise specified in the appropriate Diagrams and Parameters document Parameter Value leycle Element cycle time 10 ms from Nominal frequency 50 Hz Reference Parameter Value Vn Nominal voltage 63 5 110 V Vs Setting 5V M Multiplier 40 ta Delay setting 0 00 600 00 s tres Reset setting INST 1 2 60 s 3yo Applied voltage for IDMTL 2to20 xVs operate time DTL 10 xVs from Frequency from Ambient temperature 20 C Operate and Reset Level Attribute Value IDMT 105 Vs 2 or 0 5 V Vop Operate level DTL 100 Vs 2 or 0 5 V 2010 Siemens Protection Devices Ltd P202. 5 100 V I Volt Block Level Va amp Volt Block p Vb Ve P300018 Voltage Protection Functions Volt Block Figure 2 2 Functional Diagram for Voltage Blocking Element 2 1 2 2 Specification Element Parameters The element will take the following parameters unless otherwise specified in the appropriate Diagrams and Parameters document Parameter Value leycle Element cycle time 5 ms from Nominal frequency 50 Hz Reference Parameter Value Vs Setting 2 0 V Frequency fnom Ambient temperature 20 C 2010 Siemens Protection Devices Ltd P20051 Page 6 of 15 SIEMENS SIEMEN TUSSA AU 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Operate and Reset Level Attribute Value Vork Operate level 100 Vs 1 Vn Reset level lt 105 Vox Repeatability 1 10 C to 55 C lt 5 Variation aes ta te 2Hz 55 2 1 3 Neutral Voltage Displacement Element ANSI 59N 2 1 3 1 Description Neutral Voltage Displacement provides two stages of Earth Fault protection using residual earth voltage This allows for an alarm to be issued followed by a trip if the fault is not located and cleared The two stages can be configured to be either definite time lag DTL or inverse definite minimum time IDMT M tp Eji can be selected using Elem Character the multiplier M on the IDMT charac
3. TUSSA AU 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Elem Inhibit Volt Block Va Vb Ve Elem An Y Elem M All UV OV o Vi Elem Operation Elem Setting Elem Hysteresis Elem Starter Elem Delay EL fs gt Elem Operate P300018 Voltage Protection Functions U O Volt Figure 2 1 2 1 1 2 Specification Element Parameters Functional Diagram for Phase Voltage Element The element will take the following parameters unless otherwise specified in the appropriate Diagrams and Parameters document undervoltage Parameter Value leycle Element cycle time 10 ms fnom Nominal frequency 50 Hz Reference Parameter Value Vn Nominal voltage 63 5 110 V Vs Absolute settings 55 0 V hyst Hysteresis 2 ta Delay setting 0 0 600 0 s Frequency thom Ambient temperature 20 C Operate and Reset Level Attribute Value Vop Operate level 100 Vs 1 Vn fesj overvoltage gt 100 hyst x Vop 1 lt 100 hyst x Vop 1 Repeatability 1 10 C to 55 C lt 5 Variation from 3 Hz to from 2 Hz 59 Operate and Reset Time Attribute Value basic Element basic operate time overvoltage 0 9 to 1 1 x Vs 45 ms teycle 0 9 to 2 0 x Vs 35 ms
4. 2 0 2 1 5 0 20 s 21 600 V2 2 Off On V2 2 Setting 1 0 1 5 20 0 90 V V2 2 Delay 0 0 01 2 0 2 1 5 0 20 21 600 Sub menu Status Inputs a inhibit _ 1 for each status input V2 2 Inhibit 2010 Siemens Protection Devices Ltd P20051 Page 9 of 15 SIEMENS SIEMEN TUSSA AU 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Setting name Range bold default Units Notes Sub menu Output Relays V2 Starter Alarm output V2 1 Operate _ 1 for each output contact Trip output if enabled V2 2 Operate Trip output if enabled On Enabled Off Disabled Elem Inhibit Elem Operate Figure 2 4 Functional Diagram for NPS Voltage Element 2 1 4 2 Specification Element Parameters The element will take the following parameters unless otherwise specified in the appropriate Diagrams and Parameters document Parameter Value leycle Element cycle time 10 ms fnom Nominal frequency 50 Hz Reference Parameter Value Vn Nominal voltage 63 5 110 V Vs Absolute settings 55 0 V hyst Hysteresis 2 ta Delay setting 0 0 600 0 s Frequency thom Ambient temperature 20 C Operate and Reset Level Attribute Value Vop Operate level 100 Vs 1 Vn Reset level overvoltage gt 100 hyst x Vop 1 Repeatability 1 10 C to 55 C
5. 051 Page 8 of 15 SIEMENS SIEMEN TUSSA AU 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Attribute Value Reset level gt 95 Vag Repeatability 1 10 C to 55 C lt 5 ER fnom 3 Hz Variation to from 2 Hz lt 5 For NVD settings below 7 5V the reset level can be up to 80 of operate value Operate and Reset Time Attribute Value fsa Element basic OV to 1 5 x Vs lt 43 ms Pase operate time OV to 10x VS lt 38 ms t LET 4 op avo 1 5 or 0 ms top Operate time Ys char DTL thasic ta 1 or teycle tres Reset time toasic tres I Or teycle Repeatability 1 or 10ms Overshoot time lt 40 ms Disengaging time lt 50 ms fnom 3 Hz Variation to from 2HZ lt 5 2 1 4 Negative Phase Sequence Overvoltage Element ANSI 47N 2 1 4 1 Description The negative sequence component is derived from the three phase voltages It is a measure of the quantity of unbalanced voltage in the system The protection comprises two independent instantaneous elements each with a follower time delay These delays can be used to provide time grading margins sequence co ordination grading or scheme logic Table 2 4 Typical Settings NPS Voltage Element Setting name Range bold default Units Notes V2 1 Off On V2 1 Setting 1 0 1 5 20 0 90 V V2 1 Delay 0 0 01
6. 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference 7SG13 Delta Protection and Control Relays Document Release History This document is issue 2010 02 The list of revisions up to and including this issue is Pre release 2010 02 2006 09 2005 12 2005 12 2004 03 2003 02 2003 01 Document reformat due to rebrand 3Vo Input setting added NPS Over voltage and Frequency protections added Updated logic diagrams added NVD applications Revised Performance Specification v2 Page 1 removed invalid references First issue Software Revision History The copyright and other intellectual property rights in this document and in any model or article produced from it and including any registered or unregistered design rights are the property of Siemens Protection Devices Ltd No part of this document shall be reproduced or modified or stored in another form in any data retrieval system without the permission Siemens Protection Devices Ltd nor shall any model or article be reproduced from this document unless Siemens Protection Devices Ltd consent While the information and guidance given in this document is believed to be correct no liability shall be accepted for any loss or damage caused by any error or omission whether such error or omission is the result of negligence or any other cause Any and all such liability is disclaimed 2010 Siemens Protection Devices Ltd SIEMENS slemens russia com 7SG13 De
7. Setting value value Alternatives 1st 2nd 3rd 2 The purpose of this document is to describe the capabilities and functionality of Overcurrent Protection elements Separate User Manual documents describe how to set up and operate the equipment apply configuration settings and passwords view instruments and set default instruments and retrieve fault data Elem Char Dir Digital input signal status Elem Inhibit Setting block showing list of setting input visible to user values with setting name Appropriate block is TRUE when setting selected F J other blocks are FALSE Digital output signal output Elem Startet relay visible to user 7 Elem Reset Delay C Common setting for multi function block Common control input c for multi Digital signal not visible to PhaseAFwd function block All function blocks are user to from another element disabled when control input is FALSE Digital signal not visible to I PhA Dir Bik Function blocks user internal to this element Individual function blocks are disabled when associated control input c is Analogue signal with signal la FALSE description And Gate P300017 Current Protection Functions Key Or Gate Figure 1 1 Key to Functional Block Diagrams 2010 Siemens Protection Devices Ltd P20051 Page 3 of 15 SIEMENS sjemens russia com 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Section 2 Element Definitio
8. ad shedding equipment on a system the relay should be set to co ordinate with it 2010 Siemens Protection Devices Ltd P20051 Page 15 of 15 SIEMENS sl mens russia com
9. e ratio of NPS to PPS Current is much higher than the equivalent ratio of NPS to PPS Voltage NPS Voltage is instead used for monitoring busbar supply quality rather than detecting system faults The presence of NPS Voltage is due to unbalanced load on a system Any system voltage abnormality is important since it will affect every motor connected to the source of supply and can result in mass failures in an industrial plant 2010 Siemens Protection Devices Ltd P20051 Page 14 of 15 SIEMENS sl mens russia com 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference The two NPS Voltage DTL elements should therefore be used as Alarms to indicate that the level of NPS has reached abnormal levels Remedial action can then be taken such as introducing a Balancer network of capacitors and inductors Very high levels of NPS Voltage indicate incorrect phase sequence due to an incorrect connection The Relay uses NPS Voltage as an integral part of other protection algorithms such as VT Supervision NPS polarising is also utilised when reliable Zero Phase Sequence ZPS quantities are not available for example due to the VT connection configuration 3 3 Frequency Protection 3 3 1 Underfrequency and Overfrequency Protection When a power system is in stable operation at normal frequency the total mechanical power input from the prime movers to the generators is equal to the sum of all the connected loads plus all real power losse
10. essary since sudden moderate to severe frequency shifts can throw a system into a dangerous state much faster than an operator can react Underfrequency relays are usually installed at distribution substations or industrial plant where selected loads can be disconnected and where similar priority loads are often grouped together The object of load shedding is to re establish the generator load equation At the instant of a disturbance a measure of the amount of overload is not readily available and thus load is shed in stages until the frequency stabilises and returns to within the nominal band An example scheme would have the first load shedding stage set just below the nominal frequency e g between 49 0 49 5Hz A time delay element would be associated with this and this would be set to allow for transient dips in frequency as well as to provide a time for the system regulating equipment to respond The first load shedding stage would be set to shed a significant percentage of the system load If this drop is sufficient the frequency will stabilise and perhaps increase and return to nominal If however this is not sufficient then a second load shedding stage set at a lower frequency will now shed a smaller percentage of load until the overload is relieved This process will continue until all stages have operated In the event of the load shedding being unsuccessful a final stage of underfrequency protection should be provided to totally isola
11. foyele undervoltage 1 1 to 0 5 x Vs 60 ms teycie 2010 Siemens Protection Devices Ltd P20051 Page 5 of 15 SIEMENS SIEMEN TUSSA AU 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Attribute Value top Operate time following delay tbasic fo 1 Or teycie Repeatability 1 or loycle Disengaging time lt 100 ms hode fnom 3 Hz S Variation to fron 2 Hz lt 5 2 1 2 Voltage Blocking Element ANSI 27 2 1 2 1 Description The voltage blocking element acts as a block to the phase and negative sequence voltage elements and frequency elements If all phase voltages fall below the threshold level then the blocking output will operate This element is required mainly for undervoltage operation conditions Under normal circumstances if all phase voltages fall below the undervoltage setting a trip output would be the expected response However in some applications e g auto reclose schemes having an undervoltage relay trip when the line is de energised during the auto reclose sequence is not desirable Blocking the undervoltage operation in this situation can be achieved by using the voltage blocking threshold which should generally be set above the level of expected induced voltages on the line Table 2 2 Typical Settings Voltage Blocking Element Setting name Range bold default Units Notes Sub menu System Config Volt Block Level OFF 1 2
12. lt 5 Variation from gt 3 Hz to fom 2 Hz 59 Operate and Reset Time Attribute Value i Element basic evendtiage 0 9 to 1 1 x Vs 45 ms toycie basic operate time 0 9 to 2 0 x Vs 35 ms fote 2010 Siemens Protection Devices Ltd P20051 Page 10 of 15 SIEMENS SJEMEN TUSSA AU 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Attribute Value top Operate time following delay tbasic fo 1 Or teycie Repeatability 1 or loycle Disengaging time lt 100 ms hode fnom 3 Hz Variation to fron 2 Hz lt 5 2 2 Frequency Protection 2 2 1 Underfrequency and Overfrequency Elements ANSI 81 2 2 1 1 Description Overfrequency and underfrequency elements use the same functionality as shown in Figure 2 1 The sense of inhibited in four different ways If all phase voltages fall below the voltage blocking threshold level Via a status input inhibit signal Via any combination of voltage elements starting If all of the phase voltages fall below an absolute level of 29V This is independent of the voltage blocking threshold and is required to ensure that the frequency accuracy claims are within 10mHz The frequency calculation is performed on data from one input phase only If all phase voltages are above an internal threshold of 29V then the frequency calculation will be derived from the phase A input If however phase A falls below 29V then the calculation
13. lta P20051 FM1 Voltage Protection Technical Reference Contents Section 1 Introduction wariz acc esieeececerec cee dete est sencctane chee ce ncencangaeceadeeeces cangaseniecsennet cranes etdeeesncuedennesscnegeeceddeuee 3 11 IMMOGUGHOMN lt Sszsed desizes cedhvgscdsdusaasctudaacecsdeaaeectdbdzeacsiudasdetdesdseds dea ecersdtascectdeaddedsneddescaveadeacsacaasaceves 3 Section 2 Element DefinitiOnS rrrarrnnnavnnnnnnnnnvnnnnnvnnnnnnnnnnnnnnnvnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnnennnnnnnnnnnnnnnnnnnnn 4 2 1 Voltage Protection muuumiminn cased sats neve ccvedeskle eeusedsclaceualaheuiedeppetsbeeanesuali leaigadcleeauestandttensegenze 4 2 1 1 Phase Undervoltage and Overvoltage Elements ANSI 27 and 59 rrrurnrrnannrnnnnnnnrn 4 2 1 2 Voltage Blocking Element ANSI 27 rrnnrrrerrnnvvvrrrnnvrverrnavvenrrnarvrerrnnrreerrnerverrrnerreerrnnnn 6 2 1 3 Neutral Voltage Displacement Element ANSI 59N rrrrrrrnnnnrnnnnnvnrrrrnnnnrrrnnnrnnnnnnnnn 7 2 1 4 Negative Phase Sequence Overvoltage Element ANSI 47N seses 9 2 2 Frequency Protection ccccccccecesesceceseeeceeeeeaaeeeeneeeceaeeeeaaeseeaeeceaeeesaeesesaesseasesseeeeseaesseaeeseaes 11 2 2 1 Underfrequency and Overfrequency Elements ANSI 81 rurnrnnannnnrnrrnnnnrnnnnnvnnennne 11 Section 3 Application N tese dasan dansana a eder coset udcuadencesctentsanesncesuaes 13 3 1 Voltage Blocking Else nt rsrsrsr aneinander ea 13 3 2 Voltage Protectiei iarsin aaeain aia iTia din ne
14. ns 2 1 Voltage Protection 2 1 1 Phase Undervoltage and Overvoltage Elements ANSI 27 and 59 2 1 1 1 Description Phase overvoltage and undervoltage elements use the same functionality as shown in Figure 2 1 In some setting while in others it will be pre defined as undervoltage or overvoltage If a voltage blocking element is provided it will inhibit voltage elements The elements can be selected to operate either when any of the phase elements are picked up or alternatively when all of the phase elements are picked up As can be seen in Figure 2 1 this affects the starter and operate outputs off ratio for the element Table 2 1 Typical Settings Phase Voltage Element Setting name Range bold default Units Notes Volt Input Mode Ph N Ph Ph Elem Operation Off U V O V Elem Setting 5 0 5 5 55 0 200 0 V Elem Hysteresis 12 90 o This setting is not always pe z provided Elem Delay 0 0 0 1 10 0 10 5 100 101 1000 1010 10000 10100 s he actual setting range may 100000 101000 864000 differ from that shown here Elem O P Phases Anv All This setting is not always y provided Sub menu Output Relays Elem Siarter Elem Trip Sub menu Status Inputs Elem Inhibit 1 for each status input The inhibit input is not always provided _ 1 for each output contact 2010 Siemens Protection Devices Ltd P20051 Page 4 of 15 SIEMENS SIEMEN
15. nvnnonvnnnnvrvnnnrnnnnnvnnnrrrvnnnrnnennenrennen 12 List of Tables Table 2 1 Typical Settings Phase Voltage Element rrrnrrnnnrnnvvnnnrnavvvnrrnavnvnrrnarrnnrrnsrnnnrrrsrnnnrsrsrnnnennn 4 Table 2 2 Typical Settings Voltage Blocking Element cccccccessestecesseceeeseeeeeeesseeseeeseesaeesseeeaeess 6 Table 2 3 Typical Settings Neutral Voltage Displacement Element cccceesseeeseseeesseteeeseeaeens 7 Table 2 4 Typical Settings NPS Voltage Element rrnrannvnnnnannvnnnnrnnvnnnrrnnvnnnrrrnnnnnsrrsrrrnrsrsrnnnsrrsrnnnennn 9 Table 2 5 Typical Settings Frequency Element rrrnvrnrrnvvrnrrnvrnrnrrrrnnrnrrrsnnrnnrrrrnnrnrrrrnnrnerrrnnnnrsrrnnnne 11 2010 Siemens Protection Devices Ltd P20051 Page 2 of 15 SIEMENS SIEMENS TUSSA AUT 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Section 1 Introduction 1 1 Introduction This document covers the voltage based protection elements and their applications found in the Modular II range of relays as listed below A Diagrams and Parameters document which covers each individual model is available which lists explicitly the functions that are provided and the manner in which they are connected 27 Phase undervoltage 27 Voltage blocking 47 Phase sequence voltage 59 Phase overvoltage 81 Frequency Notes 1 The following notational and formatting conventions are used within the remainder of this document Setting Elem Setting name e
16. ods because they can cause damage to the system insulation and severely affect the life of the insulation An overvoltage element with an appropriate DTL time delay setting to allow the normal system regulating equipment to operate can be used to protect against this type of condition If a number of overvoltage elements are available a variety of different applications can be covered If the overvoltage condition is small a relatively long DTL time delay can be set on an element to clear the fault If the overvoltage is more severe then another element set at a higher pickup level and with a faster DTL time can be used to clear the fault more quickly Alternatively elements can be set to provide alarm and tripping stages with the alarm levels set lower than the tripping stages The use of instantaneous and wide ranging DTL settings allows a simple and secure grading system to be applied to co ordinate the network design the regulating plant design and system plant insulation withstand The use of IDMTL protection is not recommended because of the difficulty of choosing settings to ensure correct co ordination and security of supply Generally wherever voltage relays are employed timing elements should be used to prevent operation during transient disturbances In addition overvoltage relays must be co ordinated with other overvoltage relays elsewhere on the system 3 2 4 Neutral Voltage Displacement Neutral Voltage Displacement Residual O
17. s in the system Any frequency variation is an indication of generator load imbalance in the system If an interconnected system splits for example there might be a situation where the load in one of the subsystems is in excess of the generator capacity in that subsystem In this instance the generator speed will begin to decrease causing a proportional frequency drop An underfrequency condition at nominal voltage can lead to over fluxing of plant such as generators and transformers If the governors and other regulating equipment cannot respond quickly enough a sustained underfrequency condition may lead to a system collapse Conversely if there is an excess of generation in the subsystem then the generator speed will increase causing a proportional frequency rise This may be unacceptable to industrial loads for example where the running speeds of synchronous motors will be affected In the situation where the system frequency is collapsing rapidly it is common practise to disconnect non essential loads for short periods of time until the generation load requirements and network configuration can be corrected This is designed to preserve system integrity and minimise outages Normally utilities will avoid intentionally interrupting service but in this case non critical loads can be interrupted for short periods This type of scheme is known as an underfrequency load shedding scheme Usually automatic load shedding based on underfrequency is nec
18. se 13 3 2 1 Voltage Element Hysteresis mmrrrrnannvnnnnnvnnnrrennnrrnnnnvnnenvennnnrnnennvnnenrernnrrrennrnnnnnennnnn 13 3 2 2 Undervoltage Protection earnrnnnnrrnannvnnnnnvnnrrennnrnnnnnnennnnrennnrnnannnnnenrennnrnnennnnnennennnnn 13 3 2 3 Overvoltage Protection ccceccceccceeeseeeeeeeceeeeeesaeeeseeeeceaeeeeaaeseeaeeseaeeetaeeseaaeeeeneeeaas 14 3 2 4 Neutral Voltage DisplaceMent ccccccceececeeeeeeeeeeeeseeeeeeeeeeaaeeseaeeseaeeesaeeseaeseeneeeaas 14 3 2 5 Negative Phase Sequence Overvoltage rrrrrannrnnnnnvnnonvvnnnrrvnnnrnnnnnnnrnnrrrnnnrnnennnnennn 14 3 3 Frequency Protection uinuuasuunindeas anmeldte 15 3 3 1 Underfrequency and Overfrequency Protection srrrrnrrnnnrrnnnnvnnenvvnrnrrennnrrnnennnnrnnn 15 List of Figures Figure 1 1 Key to Functional Block Diagrams arrrannvvnonvvnnerrrnnnrrnnnnrnnenvennrrrennnrnnnnnvnnenrenerrresnnnnnnennenenn 3 Figure 2 1 Functional Diagram for Phase Voltage Element rrrnrnraranvvnrnrannvrrrrrrnnrnrrrrnnrnrrrrnnrrrrrrrnnnnn 5 Figure 2 2 Functional Diagram for Voltage Blocking Element rrrnnannvnnonvvnnnvrnnnnrnnnenrvnnnrrnnnnrnnennnnennr 6 Figure 2 3 Functional Diagram for Neutral Voltage Displacement Element arnrnnanvrnrnrrnnnnnrnnnnvnnrnnr 8 Figure 2 4 Functional Diagram for NPS Voltage Element urnrrrannvnnnnvvnnrnvrrnnnrnnnnvennerrenrnrrrnennenrrnrenn 10 Figure 2 5 Functional Diagram for Frequency Element orrrnannvnnnn
19. ss otherwise specified in the appropriate Diagrams and Parameters document Parameter Value leycle Element cycle time 10 ms Reference Parameter Value Vn Nominal voltage 63 5 110 V hyst Hysteresis 2 Ambient temperature 20 C Operate and Reset Level Attribute Value Fop Operate level 100 Fs 10mHz overfrequency gt 100 hyst x Fop 25mHz Reset level underfrequency lt 100 hyst x Fop 25mHz Repeatability 1 Variation 10 C to 55 C lt 5 Operate and Reset Time Attribute Value Typically lt 110ms overfrequency a Element basic Maximum lt 150ms ase operate time Typically lt 110ms underfrequency Maximum lt 150ms lop Operate time following delay tbasic fo 1 Or teycie Repeatability 1 or loycle Disengaging time lt 100 ms 2010 Siemens Protection Devices Ltd P20051 Page 12 of 15 SIEMENS SIEMEN TUSSA AU 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Section 3 Application Notes 3 1 Voltage Blocking Element The voltage blocking element acts as a block to the phase voltage elements If all phase voltages fall below the threshold level then the blocking operation will operate The voltage blocking element performs a number of functions e If the relay has been set up with undervoltage elements enabled and is switched on with no volts applied
20. stem rated voltage is expected to run Typical values for hysteresis applied to a voltage element are lt 5 When setting the hysteresis level the user has to be aware that if the amount of hysteresis is set too low e g 1 then for large frequency excursions and low values of voltage element setting the element might become unstable and chatter This will produce nuisance alarms tripping and generate large numbers of stored event records A minimum recommended level is 2 for this reason 3 2 2 Undervoltage Protection Undervoltages are reasonably frequent events on power systems and can occur for a number of different reasons Faults on the system can cause the phase voltages to be depressed the actual voltage drop being dependent upon a number of factors including the fault type and system earthing etc During system earth fault conditions the undervoltage protection is not generally required to operate and thus connecting the relay in the phase phase configuration will make it less susceptible to single phase voltage depressions Another cause of undervoltage is an increase in system loading which should be corrected by system regulating equipment such as tap changers and AVR s However if this equipment is defective then an undesirable situation will occur which will require an undervoltage relay to trip non essential loads to correct for this voltage excursion and to bring it back to its nominal level This tripping should happen af
21. te all loads before plant is damaged e g due to overfluxing An alternative type of load shedding scheme would be to set all underfrequency stages to about the same frequency setting but to have different length time delays set on each stage If after the first stage is shed the frequency doesn t recover then subsequent stages will shed after longer time delays have elapsed As has been mentioned earlier where there is an excess of generation in a subsystem the frequency will rise This is most commonly due to loss of load situations which cause the generators to speed up Normally the generator control equipment will respond to regain the normal running speed but if this equipment fails then the overfrequency protection can be used as a backup The settings for the overfrequency elements should be set to allow for transient frequency excursions following a loss of load condition and allow time for the generator control systems to recover the situation The relay has four frequency elements each of which can be set for underfrequency operation These coupled with independent voltage elements and a large number of output contacts available enable economic application for complex load shedding schemes The accuracy and security of operation built into the numeric algorithms makes them ideally suited for this type of application All frequency elements can be blocked in a number of different ways It is important to note that where there is other lo
22. ter an appropriate time delay has expired Generally wherever voltage relays are employed timing elements should be used to prevent operation during transient disturbances If the system is supplying 3 phase induction motors or variable frequency thyristor drives undervoltages can have the following effect Voltage depressions down to approximately 80 of rated voltage cause the load current to increase possibly resulting in a larger voltage depression due to the supply source impedance Below 80 the current drawn is proportional to the voltage and an induction motor is likely to stall The current drawn is then dependent on the drive design e g thyristor drives include current limitation An undervoltage element can be set to trip out a motor circuit when the voltage falls below a preset value selected based on the motor drive and system design parameters and after a preset time delay The time delay is required to ensure voltage dips due to remote system faults do not result in an unnecessary trip If the system supply to a group of motors is lost undervoltage protection can be applied to ensure that each of the motor circuit breakers or contactors are tripped so that on restoration of the main supply it is not overloaded by 2010 Siemens Protection Devices Ltd P20051 Page 13 of 15 SIEMENS sjemens russia com 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference the simultaneous starting of all the motors A 3 phase
23. teristic is set using Vs direction in which the element is applied It should be noted that neutral voltage displacement can only be achieved for VT arrangements that allow zero sequence flux to flow in the core i e a 5 limb VT or 3 single phase VTs should be used Another requirement is for the VT primary winding neutral to be earthed to allow earth zero sequence exciting current to flow For relay models that do not provide Check Synchronising the fourth VT input is available for Residual Voltage left as Calculated even if the Residual Voltage is measured as one of the other 3 VT inputs Table 2 3 Typical Settings Neutral Voltage Displacement Element Setting name Range bold default ant Notes 3Vo Input Calculated Measured Elem Character Off DTL IDMTL Elem Dir NorDir Forward Reverse Requires appropriate directional element to be present Elem Setting 1 1 5 5 00 100 V Elem Delay DTL 0 00 0 01 2 00 2 1 20 00 21 600 Elem Multiplier 0 1 0 2 0 5 10 10 5 140 Elem Reset Delay INST 1 2 60 S Sub menu Output Relays Elem Starter _ 1 for each output contact The starter output is not always Elem Trip _ 1 for each output contact provided Sub menu Status Inputs Elem Inhibit 1 for each status input The inhibit input is not always provided 2010 Siemens Protection Devices Ltd P20051 Page 7 of 15 SIEMENS SJEMEN TUSSA AU
24. to its inputs then an undervoltage starter would pickup and the relay may issue a trip The relay would then stay locked in this trip condition until volts are applied and the element is reset To prevent this from happening the voltage blocking threshold has to see volts above its set level otherwise the phase voltage elements are fully blocked and no starter or trip operation will follow e In auto reclose schemes the voltage blocking threshold can be used to prevent unnecessary operations of the undervoltage elements during the time when the line is de energised For this type of blocking operation the threshold is typically set to 20 of rated volts though it should always be set to a value above the expected level of induced voltages on the line 3 2 Voltage Protection 3 2 1 Voltage Element Hysteresis The voltage element hysteresis setting if available allows the user to alter the pick up drop off ratio of the element When using the variable hysteresis care has to be taken to ensure that with undervoltage elements the reset level of the element is not set to a value higher than that at which the system rated voltage is expected to operate The system rated voltage will typically have a tolerance of 10 so the upper level of the hysteresis must be below the lower limit of the tolerance otherwise the element may not reset Conversely the level of hysteresis set for an overvoltage element should not be set below that at which the sy
25. undervoltage relay may be used for this task of tripping a feeder for the detection of a complete loss of voltage Also where a supply to induction motors is lost the undervoltage relay can be used to detect the loss of supply or to monitor any busbar residual voltage e g resulting from back e m f generated by the induction motors as they run down The relay can act as a guard prior to re connecting a supply from an alternative source Where undervoltage relays are used on a system the voltage elements should be set to a value below that where a normal system voltage excursion can be expected See also section 2 5 Typically the set values may be 65 to 80 of nominal for protection of the system or plant For confirmation that a monitored supply is dead or that any residual voltage has reduced to a safe level typical set values should be 10 to 30 of nominal voltage 3 2 3 Overvoltage Protection Overvoltages may be caused for a number of different reasons On generator sets for example it may be caused by defective operation of the voltage regulator or if there is a sudden loss of load due to line tripping Under this load rejection situation the generator set may overspeed causing a dangerous voltage rise This should be corrected by system regulating equipment such as tap changers and AVP s but if this equipment mal functions then voltage levels may rise High levels of overvoltages on a system cannot be sustained for long peri
26. vervoltage protection is used to detect an earth fault where there is little or no earth current present This would occur for example where a feeder has been tripped at its HV side for an earth fault but current is still being supplied to the fault from the LV side via an unearthed transformer This current might be provided through interconnection or a secondary supply source Insufficient earth current would be present to cause a trip but residual voltage would increase significantly reaching up to 3 times the normal Vphase level The same situation could also be allowed for by utilising inter tripping from the HV side of the feeder to its LV side If NVD protection is used it must be suitably time graded with other protections in order to prevent unwanted tripping for external feeder faults Although operating characteristics are provided by the relay for NVD this grading would typically be achieved using a DTL Calculations are performed on the voltage fundamental component This gives the feature excellent 3rd Harmonic rejection 3 2 5 Negative Phase Sequence Overvoltage Negative Phase Sequence NPS protection detects phase unbalances and is widely used in protecting rotating plant such as motors and generators However such protection is almost universally based on detecting NPS Current rather than Voltage This is because the NPS impedance of motors etc is much less than the Positive Phase Sequence PPS impedance and therefore th
27. will automatically switch to phase B data During the switchover process the last frequency value measured is held until phase B returns a valid frequency answer This will take approximately 180ms The switchover precedence is A B C and as each phase recovers its voltage then the frequency calculation is switched back to this phase This method ensures that the frequency calculation is performed on a solid system voltage and not on low levels of input voltage where noise could cause incorrect calculation Table 2 5 Typical Settings Frequency Element Setting name Range bold default Units Notes Elem Operation Off U F O F Elem Setting 47 00 47 01 50 00 52 00 Hz Elem Delay 0 0 0 01 2 0 2 1 20 21 600 s Elem Inhibit _ 1 for each voltage element Sub menu Output Relays Elem Starter _ 1 for each output contact Elem Trip Sub menu Status Inputs Elem Inhibit _ 1 for each status input 2010 Siemens Protection Devices Ltd P20051 Page 11 of 15 SIEMENS SJEMEN TUSSA AU 7SG13 Delta P20051 FM1 Voltage Protection Technical Reference Enabled Disabled Elem Inhibit Elem Operation Volt Block Elem Setting C VE Picked up Frequency Figure 2 5 2 2 1 2 Specification Element Parameters lt gt Elem Delay me Functional Diagram for Frequency Element Elem Starter Elem Operate The element will take the following parameters unle
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