6th Comprehensive Protection Training Program at Pearl Continental L AHORE in 2012A TYPICAL POWER SYSTEM NETWORK Slide 1 SIEMENS LECTURE ON OVER CURRENT & EARTH FAULT RELAY SETTING CALCULATIONS AT PEARL CONTINENTAL HOTEL LAHORE ON 04-09-2012 BY SIEMENS PAKISTAN ENGINEERING COMPANY LTD Slide 2 RELAY SETTING CALCULATIONS A guide for the calculations of the Relay Settings for: Over current and Earth fault Relays a) Definite Time Relays b) Inverse Time Relays For Power Transformers & 11kv feeders Slide 3 Finalize the relays setting calculations with duly signed from client\consultant\contractor. 2. 10. Ask from client\consultant to provide essential technical data relating to the existing network and equipment needed in the subject matter. 3. 8. 5. Arrange the content/index sheet of the relays. Enlist the protection relays with their functions to be used. Submission of proposed relay settings to the consultant\client for approval. Upload the parameters in the relays according to the calculations at site for pre-commissioning and testing. need to settings' calculations. Study carefully the protection schemes designed for the project. 7. Slide 4 . Enlist the technical data required in network study and calculations of relay settings. 9. Chalk out which type of documents are agreed to submit to consultant/client. Arrange a meeting to clarify technical and disputed points regarding to the submitted document for the approval. 4.RELAY SETTING CALCULATIONS 1. 6. Slide 5 .RELAY SETTING CALCULATIONS Please note that . (pick up.Minimum generation is considered for relay setting calculations.Circuit Breaking capacity is calculated for maximum generation possible.trip) & . PROTECTION IN SMALL ZONES USING OVERLAPPING PRINCIPLE 1 2 G G 3 POWER HOUSE STATION A 132 kV 4 STATION B 132 kV Boundary of Protection Zones are decided by Location of CT’s X 1 2 3 4 PAKISTAN Circuit Breaker Generator Protection Zone Generator Transformer Unit Protection Zone Bus Bar Protection Zone Transmission Line Protection Zone Slide 6 . Slide 7 . Definite Time Over current Characteristic Slide 8 . Inverse time Over current Characteristic Slide 9 . Slide 10 . Normal Inverse time characteristic of relay 7SJ60 Slide 11 . NTDC and the utilities in Pakistan however have standard practice to use Inverse time relays for back up of Motors. Slide 12 . Although there is no hard and fast rule for use of definite time or inverse time relays and one can decide by looking into the site requirements. It can be applied where there is an abrupt change of current due to faulty condition.SETTING DEFINITE TIME OVERCURRENT RELAYS Over current Relays has a wide range of applications. definite time over current relays are used for back up purpose. These relays are used for protection of Motors. Transformers. Generators and Transmission Lines etc. For HV and EHV lines. Transformers and Generators. In distribution networks these are the main protection whereas in HV and EHV systems. these are used as back up protection. When an element picks up. Slide 13 . The over current element for its pick up value. The instantaneous element pick up value for the current is to be selected whereas time setting is instantaneous.SETTING DEFINITE TIME OVERCURRENT RELAYS Definite time over current relays have adjustable over current elements. it energizes a built in time element which initiates a tripping signal after elapse of set time. In definite time over current Relays. the high set element for its pick up value along with the time delays required. we have to set. 7SJ602 SETTING POSSIBILITIES OVERCURRENT RELAY 7SJ602 PHASE FAULTS STAGE I> DEFINITE TIME OR IDMTL EARTH FAULTS DEFINITE TIME OR IDMTL STAGE I>> DEFINITE TIME OR INSTANTANEOUS DEFINITE TIME OR INSTANTANEOUS STAGE I>>> INSTANTANEOUS ------------ Slide 14 . OVERCURRENT RELAY SETTINGS Slide 15 . OVERCURRENT RELAY SETTINGS The relay at the far end B is set with shortest operating time.1or 0. Slide 16 . The Relay on upstream which is at end A has to be time graded against relay at end B with a minimum time difference of 200-300mSec for numerical relays and of 400-500mSec for electro-mechanical relays. The relay at end B is required to be set with the minimum operating time IDMTL mode and to be set for TMS of 0. The relay at end A has to be set accordingly.05 Time Dial whichever setting is available. SETTING OF OVER CURRENT RELAYS Slide 17 . The inverse mode is selected where fault current is much less at the far end of the line than at the local end. Definite time characteristic is selected where Source Impedance is quite larger compared to the line impedance. (Selection also depends on the utility preference looking into their operational requirements.OVERCURRENT RELAY SETTINGS In the previous diagram. Relays on the upstream are to be time graded against the next down stream relay in steps of 0.) Slide 18 .2 Secs. This means small current variation between near and far end faults. the relay at far end (D) is set with shortest operating time. 95 Is = 810A = 0.5KV Required Settings: Plug Setting Characteristic to be selected Time Multiplier Setting (TMS) High Set Element Settings.7SJ602 SETTING CALCULATIONS FOR AUTOTRANSFORMER 3x200 MVA 500KV 3 × 200 MVA Auto-transformer HV Winding Circuit Time Over Current Relay Type: CT Ratio : Rated power: Rated voltage: (at minimum tap) 7SJ6021-5EB20-1FA0 N = 3250/1 S = 600MVA U = 472.25A Slide 19 . I >>> Plug Setting: Autotransformer HV winding rated current IN = S ÷ ( 3 × U ) Allowed overloading Relay's resetting ratio = Drop off ÷ Pick up Relay's setting current = (IN + IN ) ÷R Corresponding secondary current = Is ÷ N IN = 733A = 5% R = 0. I >> Instantaneous Element Setting. inverse time characteristics are selected. I >> IE >> =0.200 sec. For selectivity as backup. Usually for inductive loads. definite time characteristics are suggested. tripping time chosen B =1.00 I/In Settings recommended: Over current plug setting TMS setting Characteristic Instantaneous setting (Ipick up = 5 × IN ) High Set Element Settings.47 = Normal Inverse =5. Required time multiplier setting.47 High Set Element setting = to be blocked Instantaneous setting (Ipick up = 5 × IN ) =5.25 As per IEC Normal Inverse characteristic =0.00 I/In = Blocked Slide 20 .02-1} Operating time at TMS = 1 A =2. = B ÷ A TMS = 0.565 sec. For line feeders.25)0.25 I/In =0. Time Multiplier Setting: Fault current at HV Connection of autotransformer IF =11548A Multiples of Fault Current (PSM) = IF ÷ Is =14.7SJ602 SETTING CALCULATIONS FOR AUTOTRANSFORMER 3x200 MVA 500KV Characteristic to be selected: Normal Inverse Characteristic is selected according to the NTDC System practice.14÷{(14. 57 or Is = 39A Corresponding secondary current = Is ÷ N = 0. IE >> Instantaneous Element Setting.95=38.01A Slide 21 .5KV Required Settings: Plug Setting Characteristic to be selected Time Multiplier Setting (TMS) High Set Element Settings. IE >>> Plug Setting: Autotransformer HV winding rated current IN = S ÷ 3 × U ) IN = 733A Minimum fault current considered as percentage of rated current = 5% (for purpose of pick up of relay) Relay's resetting ratio = Drop off ÷ Pick up R = 0.05x733 ÷.95 Relay's setting current = ( )×(IN ÷ R) =.7SJ602 SETTING CALCULATIONS FOR AUTOTRANSFORMER 3x200 MVA 500KV 3 × 200 MVA Auto-transformer HV Winding Circuit Earth Fault Time Over Current Relay Type: 7SJ6021-5EB20-1FA0 CT Ratio : N = 3250/1 Rated power: S = 600MVA Rated voltage: (at minimum tap) U = 472. 01 I/In =0.00 I/In = Blocked Slide 22 . For selectivity as backup. tripping time chosen B =1. Time Multiplier Setting: Fault current at HV Connection of autotransformer IF =1469A Multiples of Fault Current (PSM) = IF ÷ Is =38. definite time characteristics are suggested. I >> IE >> =0.14÷{(38.854 sec. Required time multiplier setting.59 = Normal Inverse =5.59 High Set Element Setting = to be blocked Instantaneous setting (Ipick up = 5 × IN ) =5. inverse time characteristics are selected and For line feeders.07 As per IEC Normal Inverse characteristic =0.02-1} Operating time at TMS = 1 A =1. = B ÷ A TMS = 0.00 I/In Settings recommended: Over current plug setting TMS setting Characteristic Instantaneous setting (Ipick up = 5 × IN ) High Set Element Settings. Usually for inductive loads.100 sec.7SJ602 SETTING CALCULATIONS FOR AUTOTRANSFORMER 3x200 MVA 500KV Characteristic to be selected: Normal Inverse Characteristic is selected according to the NTDC System practice.07)0. 95 = 360x1.1 . Permissible over loading Relays Resetting ratio = Drop off/Pick up Relay setting current Secondary Current Selected Pick Up Setting 3) Time Multiplier Setting Assuming fault current Multiple of Fault Current (PSM) = 360 A = 10 % = 0.2 A 80 = 1.95 = 417 = 5.23 = 1350 417 Slide 23 .OVER CURRENT RELAY SETTINGS FOR 11KV FEEDER 11 kV Outgoing Panel CT Ratio = 400/5 = 80 Load Current = 360 A Relay Nominal Current = 5A ___________________________________________________________________________ Relay 7SJ602 O/C Settings Calculations Settings Required 1) Characteristic to be chosen 2) Plug Setting 3) Time Multiplier Setting TMS 4) High Set elements settings I >> IE >> 5) Instantaneous element setting I >>> ___________________________________________________________________________ PHASE FAULT: Ip > (Pick Up) 1) Characteristic = Normal Inverse (IEC) 2) Plug Setting Considering Full Load Current.04 = 417 A = 1350 A (an hypothetical value) = 3. 85/ 5 =4.85 A 80(ct ratio) Selected Pick Up Setting = 20.20) (Please note that the fault current is to be calculated based on fault calculation study on HT side and considering the secondary impedance of the Transformer installed ) Slide 24 .04 x 5 = 5.24 PHASE FAULT: Ip >> (High Set) 1) Characteristic = Definite Time _ 2) Plug Setting Considering 4.05 A 80 Selected Pick Up Setting = 26.057 5. ) Therefore: TMS = _0.0 times the Pick up Current.2 (or we can calculate from I pick up which will be 1.02 (3. Secondary Current = 417x5 = 26.17 3) Time Setting = 0.0267 = 5. Secondary Current = 1668 = 20.14 = 0.3_ = 0.24 Time required for Relay Operation is = 300 mSec ( Normally site requirements should be considered.0 times the Pick up Current.23 – 1) 0.05/5 = 5.14 0.OVER CURRENT RELAY SETTINGS FOR 11KV FEEDER (continues) Operating time as per IEC NI Characteristics = 0.1 s (to be chosen by the engineer as per requirement) PHASE FAULT: Ip>>> (Instantaneous) 1) Characteristic = Instantaneous 2) Plug Setting Considering 5. = 0.71 0.365 Slide 25 . Normally time of operation is set equal to phase operation time.2 Operating time as per IEC NI Characteristics = 0. rated current. the sensitivity is reduced but stability is increased.02 – 1) 0.0416 = 3.14 = 0. sensitivity increases and stability reduces.71 84. At higher pick up.14 (7.) Time Multiplier Setting Assuming single phase to ground fault current = 650 Amps Multiple of Fault Current = 650 = 7.2 x 5 = 1 (effective value in amps = 80 Amps) (Utilities normally select earth fault element pick up from 10% to 20%.EARTH FAULT SETTINGS FOR 11KV FEEDER Relay 7SJ602 E/F Settings Calculations EARTH FAULT: Ie> (Pick Up) CHARACTERISTIC SELECTED = NORMAL INVERSE (IEC) Plug Setting Considering NTDC practice to set the E/F element pick up at 20% of ct sec. At lower pick up values. 625 (It is to be noted that settings are selected keeping in view the site conditions and past experience.3 Sec ( to be selected considering site conditions) Therefore: TMS = 0.125/5=1.3 = 0.EARTH FAULT SETTINGS FOR 11KV FEEDER Time required for Relay Operation is = 0.089 3. These examples are to show the procedure only.125 80 Pick Up Setting for instantaneous element = 8. ) Slide 26 . No hard and fast rules can be chalked out.365 EARTH FAULT: Ie>> (Instantaneous element setting) 1) Characteristic = Instantaneous 2) Plug Setting Considering fault Current = 650A = 650 = 8. Thank you for your Attention Slide 27 . CONSTRUCTION OF ELECTROMECHANICAL RELAYS Slide 28 . Mech or induction base) connected to the system. Slide 29 . There are chances that the Main relay may operate unnecessarily on repeated feeder fault. The Disc emulation feature Offers its advantages when the grading co ordination chart of the time over current protection is combined with other devices (elect.Protection Co ordination of inverse time relays & Disc emulation Disc emulation evokes a dropout process. it is ensured that due to the inertia of the Ferraris Disc. which begins after de energization. This Process corresponds to the back turn of a Ferraris Disc. the history is taken into consideration. Consider the main over current relay of electro mechanical type and the feeder relay of numerical type. In case several faults occur successively. To avoid this Disc emulation feature is introduced. Slide 30 .SLAVE POINTER AND MEAN VALUES Slave pointer and Mean values is basically a measuring technique to measure the Maximum . The waveform can be of current or voltage. Minimum and average values of waveform. the tripping time is calculated according to a formula. t= 35x tL (I/ IL )2 . timer picks up. It can work with memory or without memory. motors and transformers etc) from damage caused by thermal over loading. Trip command is given after the time has elapsed. This protection operates independent on the time over current and unbalanced load protection.1 where t is tripping time I is over load current IL parameterized threshold value tL parameterized time multiplier (tripping time with 6 times the threshold value IL) Slide 31 .THERMAL OVER LOAD PROTECTION The thermal Over load protection prevents the protected object ( cables. This method is easy in handling. OVER LOAD PROTECTION WITHOUT MEMORY If the overload protection without memory is selected. When the current in any phase exceeds threshold value. Slide 32 .THERMAL OVER LOAD PROTECTION OVER LOAD PROTECTION WITH MEMORY The unit computes the temperature rise according to a thermal single body model (thermal replica). its ambient context and its cooling temperature etc. This method requires some knowledge of the protected object. This method is used when the object is to be operated at the limit of its performance. 0(10% to 400%) This statement is independent of amps.1 to 4.relay rated current 1.5 to 20 amps To make it simpler we can write the above pick up range as I/ IN from 0.0 i. 2-80 Amps) Slide 33 .0 Assume ct 100/1. the relay pick up set at 1 means relay will pick up at 100 Amps in primary And if we assume ct of 100/5. the phase current pick up I range has been defined as 0.0 amp However if IN is 5 amp then the pick up range will be from 0.0 IN If IN is 1 amp then it is easy to understand that the pick up range will be from 0. relay rated current 5.1-4. Example: In the 7SJ602 relay.1 IN ------4.e.relay pick up setting possible 2 to 80 Amp) (100/5 means 20 relay can be set 20 x 0. We have to always look at I/IN and set the relay from 0. They should match with each other so that correct setting and pick up values could be selected.CONCEPT OF I/IN IN is the rated current of the relay and also the secondary current of the Current Transformer. the relay pick up set at 1 means that relay will pick up at 100 Amps (ct 100/5 relay 1 amp.1 amp to 4.1 to 4.
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