fault level at 11kv system

Demonstrate the solution at an 11kV substation. each. A transformer is rated at 11 kV/0.4 kV, 500 KVA, 5% reactance. Registration on or use of this site constitutes acceptance of our Privacy Policy. The high voltage side protection has not been included in the model as the high voltage protection device had no influence in the study done. /Parent 2 0 R Note that some older transformers may have different LV fuse sizes installed as compared to the current standard fuse size, and some padmount transformers may have an LV circuit breaker installed. Please select system type from these two: Three Phase. Joined: 12 January 2012. Vidyut Technologies India Private Limited - Offering 11 KV ICOG VCB Panel, in Hyderabad, Telangana. That means, rated voltage of circuit breaker corresponds to the highest system voltage. 15 MVA transformer use MVASC = MVA / Zp.u. Your browser is out-of-date. Check out our Hello! A 33/11kV indoor GIS substation with a 33kV fault level of 40kA is considered. Q2. 3 0 obj [3] Kakilli, A.: System Analysis with the MVA Method for Symmetrical Three-Phase Faults. The other important aspect is the time in secs for the fault current. We design our electricity network (or distribution system) to meet the maximum fault currents set out in the table below. As mentioned earlier, the first step is the calculation of the MVA level of each component and converting the single line diagram to its equivalent MVA diagram. EPS and Energy managers association. Free access to premium services like Tuneln, Mubi and more. SAP Training ( PS , Material PR , Service PR ,Cost Planning , Budgeting , PO M. Arkam C. Munaaim Adj. straight forward. : Electrical Fault Level Calculations Using the MVA Method. jHt-k|iPT 6;' @4Yh >'^B&aJzLAo/TBa;a].)$8Qb73PVHr.D,^{?jy:5jl&FTx_s4aM}S\!5'IJR0]+K_}mVgXc;8oiy>.aGRA1dDIvlakZ5W:lEtcyEQcj7Z;+QZ~ aHgQP[7z 6{+I9b k9ye\b7A4sXi,BWRGpc@0OSnTU`@hj6+VU(d 4sX@+&gY9YmG-CU-*. design of electrical equipment (from the point of view of thermal and dynamic effects of short-circuit currents). Let us choose 10,000 kVA as base kVA and 11 kV as base kV Transformer fusing information can be found within the Pole Transformer Fusing Standard. system fault levels [1], [2]. System strength is referred to the system impedance seen at that point. B : 100 MVA. Apply effective risk management The electric power industry will continue to make distribution system reliability and customer-level reliability a top priority. For example, the equivalent MVA at branch A (consisting of network feeder, transformer T1 and power line V1) is. 1.0 SCOPE. So they had planned to deliver the desired voltage with 10 % as extra (110%) to match the transmission loss and line drop. Street lighting, as well as the switching control for street lighting, can be installed in a substation. Avoiding parallel operation of the transformers is probably the least costly approach. As a result, the fault level throughout the system also increases accordingly. Our short term solution involved two tapped reactors (operating in parallel) to segregate the older 250MVA network from the new 350MVA rated equipment. Summer Training presentation on 132/33 KV sub-station Minto park, Allahabad, Sudhir Cement Industries Pvt. control of propagation and impact of upper harmonics in power system. The fault level at the bus is. Promoting, selling, recruiting, coursework and thesis posting is forbidden. Your IP: Thank you for your interest in the topic. /Filter /FlateDecode Same fault level on 11X2. h. Maximum system fault level at 33 kV & 11kV bus es shall be 26.2kA for 1 sec & 18.3kA for 1 sec respectively. Examine how the principles of DfAM upend many of the long-standing rules around manufacturability - allowing engineers and designers to place a parts function at the center of their design considerations. Solution: Alternator percentage reactance is based on its own voltage and kVA ratings. This will involve an additional 11/33kV transformer and associated switchgear. as above. This method is popular because of its simplicity and relative accuracy. Single Phase with Cable Run. At each voltage level the fault level can be ascertained from the reactances given. [1] Jaffari, H.: Fault Current Calculation. Next, for the 69/12kV X=0.076 p.u. To access pad mount and ground substations please contact an Exclusion Zone Officer. : In most practical applications, it is not necessary to know the exact time course of short-circuit currents. Dostupn na internete: < http://www.jmpangseah.com>. The transformer fault level calculator assumes that the transformer is supplied from an infinite bus. Abstract: - The aim of this research work is to carry out a fault analysis of 33KV distribution system using Ekiti state as a case study. . One method was previously discussed here and is based on the guidelines presented in IEC 60909. [mcq] power system operation and control , power system operation and control mcq , power system operation and control mcq pdf . The maximum three-phase fault currents that can be expected on the Low Voltage (LV) terminals of a distribution transformer are set out in the table below. Engage an Exclusion Zone Officer (PDF 881.2 kb) to trace the feeder and conductor sizes back to the relevant zone substation and complete your own fault study. For above or equal 400 KV system the insulation of circuit breaker should be capable of withstanding 5% above the normal system voltage. You can read the details below. You can email the site owner to let them know you were blocked. All system parameters are provided in per unit, on 100 MVA base, so as to facilitate the f 6 TABLE VII COMPARISON OF MAX/MIN SYSTEM FAULT LEVELS AND SUPPLY IMPEDANCES PER RESIDENTIAL LOAD SUBSECTOR (A) MV (11kV Supply) (B) LV Distribution Board (0.4kV Supply) (C) 0.4kV Customer Supply Point (CSP) Type of Fault Level (3-ph) System Impedance (3-ph) A Fault Analysis of 11kv Distribution System (A Case Study of Ado Ekiti Electrical Power Distribution District) American Journal of Electrical Power and Energy Systems. Copyright All rights reserved. Please select component: Add Primary Cable Run. Fault level on 11A1 / 11A2 = base MVA/effective impedance upto the bus. This method is used very often but requires knowledge of steady-state conditions before the short-circuit occurrence, which reduces its applicability for general and fast calculations. Thank you very much for your reply pptx electrical impedance, calculation of esdd 02 006 system fault levels issue no 3, an overview in electricians terms with some examples, symmetrical fault current calculations, calculation of the . Current Limiting Reactors:- Current 2.2System Conditions: The 11kV system has three phase and earth Nominal Voltage:11kV Maximum Voltage:12kV Maximum Symmetrical fault level:31.5 kA Limited earth fault current through earthing transformer :4.5 kA Frequency:50 Hz Impulse:75 kV If we look at any electrical power system, we will find, these are several voltage levels. At this time the predicted system fault levels were 'controllable', non-volatile and essentially only modified by changes in system configuration. EHT Substations -1.0 . This enables the switchgear in the substation to remain in operational service without exceeding its 13.12-kA fault rating. The embedded hardware primarily includes the processor, memory, bus, peripheral devices, I/O ports, and various controllers. f you are working on an 11KV distribution network, then your employer should have trained you, or ensured you were adequately trained before they employed you. . In conventional power systems, the system . A Fault Analysis of 11kv Distribution System (A Case Study of Ado Ekiti Electrical Power Distribution District) American Journal of Electrical Power and Energy Systems. Add Transformer to System. These values also assume an infinite HV bus is applied at the transformer at 1.0p.u. Basic & Detailed Engineering. Dynamic Performance of Distance Relayson Series Compensated Transmission Line 60232804 ppt-compensation-techniques-in-ac-transmission-system-using-c, fault location estimator in series compensator. << Known embedded generators are added to our simulation models so that the impacts of these generators on the system fault levels are determined. This website is using a security service to protect itself from online attacks. >> Register to receive SMS notifications for power outages in your area. For above or equal 400 KV system the insulation of circuit breaker should be capable of withstanding 5% above the normal system voltage. Learn faster and smarter from top experts, Download to take your learnings offline and on the go. Fault level at any given point of the Electric Power Supply Network is the maximum current that would flow in case of a short circuit fault at that point. Corresponding to 1.94kA. Accordingly, a primary-to-secondary distribution system, consisting of both medium voltage (MV) and low voltage (LV) The invention of a Switchgear should be rated So, continuous power supply to the consumer is necessary without any interruption. For 1a 00 MVA fault level in a 11kV network, your Thevenin voltage source value will be 11,000/ (sqrt (3) = 6350V (Ph-n) and your series impedance (usually assumed reactance) = j1.21 Ohm.. In the case of unearthed cable, ground voltage is equal to phase to phase voltage. Primary Functions of Current Limiting Reactor. 192.1: Source Impedance = MV System fault MVA / Base MVA = 0.0008: LT Transformer impedance at 0.63MVA & 11kV Base = 0.05: Total MV system impedance (MV System + LT Transformer) = 0 . example 1 a 100 mva 13 8 kv y connected 3 phase 60 hz synchronous generator is operating at the The following tables provide quick order of magnitude fault levels for a a range of typical low voltage Assume system fault at the point of supply to be 250MVA @ 11KV and no load Point of Supply : 11KV, 250MVA Fault Level Transformer : 315KVA, 11KV/400V, 4% Z Supply Cable : 50 m - 240 mm. A hard-wired protection system that automatically disconnects generators from the network under pre-defined conditions, typically in . [4] Mslo, K., Novk, J., Doleal, J.: Analysis of short-circuit currents. This data can be used in substation earthing system design and assessment. Here in the following case, we will calculate the fault current and fault level of the three-phase symmetrical short circuit fault occurring at 22 kV bus bar indicated by F. 15 MVA transformer use MVASC = MVA / Zp.u. By way of example, consider a 2 MVA transformer with an impedance of 5%. The evolving lexicon of instant messaging (IM) has often been referred to as "E-illiteracy" and "IM-English" in the sense that the writers have created their own jargon that may save them time and prove they re cool but may also alienate the non-IM generation. (96 great interview questions to ask before you hire). . As you know, interviewing is a staged, contrived event. This article deals with an alternative method for the short-circuit current calculation so-called the MVA method. Based on the available statistical data, Ekiti State is reported. Thanks. The padmount transformer size is also written on the tank (for newer transformers). Nominal System voltage (kV) Highest System Voltage (kV) Phase and earth (mm) Between Phases (mm) Safety Clearance (mm) Ground Clearance (mm) 11 12.1 178 230 2600 3700 66 3.1.6 Three phase fault levels are generally higher than single phase fault levels for the 33kV and 11kV network. The method uses highly sensitive and energy-efficient magnetic sensors to detect variations in MF levels measured along the distribution lines. The between - bus reactors are a real challenge on indoor metalclad switchgear when done as a retro-fit! One great advantage of direct-current transmission links in parallel with the alternating-current system is that no increase in the short-circuit currents results. Ground overcurrent and directional overcurrent relays are the typical ground fault protection solution for such systems. I'm interested in hearing about how people out there deal with the problem of controllong fault levels in 11kV distribution substations. The impedance of the transformer and the 380V cable are shown in Fig. We design our electricity network (or distribution system) to meet the maximum fault currents set out in the table below. Objective : To be a part of an Organisation where, my knowledge and capabilities can be utilised in a creative way & challenging environment for achieving goals and to upgrade my abilities and skills to grow up in the corporate ladder. worked with Siemens PLC S7-400 and also on the WINCC redundancy worked on Constant Current Regulator (CCR) of high voltage of 30 kv, 25 kv, 20 kv, 15 . [6] Mslo, K. et al. Known embedded generators are added to our simulation models so that the impacts of these generators on the system fault levels are determined. E.g. The group currently is currently S.Mathankumar 1, V.Agalya ,Member IEEE . This is a simple graphical method that consists of subtracting the necessary parameters of the electrical system elements (impedances) from the graphs that were pre-printed on the sheets, separately for each voltage level. Actually, the total impedance, Zfault, is the equivalent impedance i.e. can be used for calculation of symmetrical and unsymmetrical faults, voltage drop during motor start-up, or steady-state. MV System fault level (Maximum) = 40 kA: 6. performance of the electrical system, choosing circuit breakers with an appropriate short-circuit current rating and short-time current rating will allow you to have a selectively coordinated system up to high fault current levels. Welcome to schneider electric's fault current calculator. As a . Abstract: There are alot of methods that can be used for short-circuit current calculation. Sometimes, if the system MVA is not available, but its voltage and impedance are given, the short circuit MVA can be calculated by MVASC = KV2 * Y formula. Nos. Earthed system refers to a three phase system whose star point is grounded directly and the voltage between the healthy phases and the ground will be - 11kV/1.732 or 6.6/1.732. Now, whether you use 12.5kA breaker or 20kA breaker cannot be decided without understanding the fault levels in your system. By using customer metering data and the agreed supply Since the system operates normally before the fault, there will be no current I f through that source. }i%G9"Ucj8/RrdssK~J=Y]4$\2.I$7s7 7`w~cIy@= :R.Wjo.uVnPYhF.R,.R` For above or equal 400 KV system the insulation of circuit breaker should be capable of withstanding 5% above the normal system voltage. /F3 12 0 R For general enquiries, call from 7:00am to 5.00pm Monday - Friday, or call after hours for planned interruption enquiries. MV System fault MVA = 3 x 40 x 11 = 762 MVA: Calculation. If your fault levels are below 10kA, of course, 20kA is better than 12.5kA as it is more capable breaker and can be used even after your fault levels go up in future. SelSystemTypeTitle. transmission network 4 Fault Level Calculations Typical State Level Power System & our area of interest . Do I just use the impedance of the TX (and obviously the turns ratio) to work out the HV fault level or is there another method? The disadvantage of nomograms is their limited use only for radial networks and the fact that the method accuracy is directly dependent on the accuracy of reading from the graphs drawn. Please advise. If you with to obtain more detailed fault level information, there are three ways you can do this: Determine the zone substation you are supplied from (available from your electricity retailer) and then locate the relevant substation and associated fault level within the Annual Fault Study Summary Report (XLSX 161.8 kb). Determine (a) the actual values of the line voltage, phase voltage and reactance, and (b) the corresponding quantities to a new base of 500 MVA, 13.5 kV. In this paper, the last factor, i.e. Copyright 1998-2023 engineering.com, Inc. All rights reserved.Unauthorized reproduction or linking forbidden without expressed written permission. SYSTEM STUDY IN 11 KV HT SYSTEMS . Please select system type from these two: Three Phase. Cloudflare Ray ID: 7a2e4b01efca1cee Please note that there may be a fee for this service. Prague, Czech Republic, 2013. It may not display this or other websites correctly. The Fault lvel in india is considered as 350 MVA. In this paper, a new approach related to the noncontact magnetic field (MF)-based measurement system to localize SC faults on 11-kV overhead distribution lines is presented. . Metal 3D printing has rapidly emerged as a key technology in modern design and manufacturing, so its critical educational institutions include it in their curricula to avoid leaving students at a disadvantage as they enter the workforce. Please include what you were doing when this page came up and the Cloudflare Ray ID found at the bottom of this page. Indoor and Outdoor Termination for 11 kV, 22 kV and 33kV Cables Used in MSEDCL 2.1 Nominal System Voltage : 11kV, 22kV, 33kV 2.2 Voltage variation on supply side : 10 % 2.8 Fault level (minimum) kA : 12.5, 25, 25 --- for 3 sec. Two 11kV feeders will be provided for the supply to the high voltage chillers at WKT. The system described has a short-circuit duty of approximately 720MVA. It's recommended this table is used 5.11 All new substations within 100 metres of an existing 11/6.6 kV ring circuit to which the connection is to be made shall be ringed. I have discussed it in other parts of this book, but you must always communicate a high energy level. and is generating 1.15 pu voltage. 3, No. Clipping is a handy way to collect important slides you want to go back to later. Effective impedance on 11X1 = 0.258pu (this needs delta to star conversion and series parallel combination of impedance, in the single line diagram) Fault level on 11X1 = 387.44MVA, 20335 Amps. Voltage level (kV) Short circuit level (MVA) Short circuit level (kA) 132kV . We also use content and scripts from third parties that may use tracking technologies. Tap here to review the details. An overcurrent relay supplied through a 3000/5 C.T. SUMMARY More than 18years' experience in engineering & design of large industrial, electrical generation power plant and petrochemical plants. clear and easy to follow. It's recommended this table is used when designing your network. For example, suppose a typical power system where electrical power is generated at 6.6 kV then that 132 kV power is transmitted to terminal substation where it is stepped down to 33 kV and 11 kV levels and this 11 kV level may further step down to 0.4 kv. Table 1. The electrical network equivalent MVA can be obtained from the sum of three parallel branches A, B, and C. The graphical representation of industrial power network reduction is shown in figure 3. 2, A possible guide to maximum 11kV Fault level is that if the 2.5MVA transformer is assumed to be on infinite 66kV bus bars, then the maximum fault level at the substation 11kV bus The aim of this research work is to carry out fault analysis of 11KV distribution power system. Electric power is an essential facilitator for sustainable development of the modern nation state. In such cases, it becomes necessary to increase the area of the grounding network. It is easy to calculate the maximum current that a transformer can deliver under symmetrical fault conditions. Register today and take advantage of membership benefits. Activate your 30 day free trialto unlock unlimited reading. The 3-phase short-circuit fault level P SC, in kA or in MVA [1] is given by the power supply authority concerned, from which an equivalent impedance can be deduced. As part of our Distribution Annual Planning Report, we publish the Annual Fault Study Summary Report (XLSX 3.1 mb) which provides information on the maximum fault levels and the corresponding sequence components at certain specified substations. Answer (1 of 2): Fault KVA of transformer =( Rated KVA of transformer/ % impedance) x100 Fault KVA of transformer =( 500/10) x100 = 500/0.1 = 5000 KVA Fault Current I = Fault KVA/ 3 V Fault Current = 5000/(1.732 x 0.4) = 7 kA Answer (1 of 2): Fault KVA of transformer =( Rated KVA of transformer/ % impedance) x100 Fault KVA of transformer =( 500/10) x100 = 500/0.1 = 5000 KVA Fault Current I = Fault KVA/ 3 V Fault Current = 5000/(1.732 x 0.4) = 7 kA each. Responsible for Power system studies and Design of Doha International Airport, Qatar Petroleum NGL facilities, and offshore platforms. The 132 kV busbar three-phase fault level is given by X Thv. By accepting, you agree to the updated privacy policy. Hi. Furthermore, 11kV switchgear panels will be provided at strategic locations for interconnection to external CLPP 11kV distribution rings to further enhance the security level of the 11kV distribution network for XRL. Network modelling indicates that site fault levels will drop by 40-45% with this connection mode. ISBN 978-80-260-4461-1. Many thanks. Close this window and log in. Fault Level Calculations 7 Step-2 What is mean by fault level. (11 kV or 6.6 kV in the UK) is typically a complex interconnected ring network containing many substations (indoor, outdoor or pole mounted), while the secondary distribution system (0.4 kV) is generally a radial The percentage impedance of a transformer has a major effect on system fault levels. Hand written calculations are hard and laborious often flawed because of all the conversions required. Test system should be versatile to test HT & LT cables of different types, sizes and various voltage levels like 33KV, 22 KV, 11KV, 6.6KV and 415V. Click to reveal These can be divided into numerical and numeric-graphical methods. 109.175.24.5 Northeast Public Power Association, 2013. Determination of Voltage Regulation and Power system losses, Determination of voltage regulation and power system losses, The important use of reactors in substations, Application of Capacitors to Distribution System and Voltage Regulation, Basic Fundamental Electronics by D-Sarda PART X, Basic Fundamental Electronics by D-Sarda PART IX, Basic Fundamental Electronics by D-Sarda PART VIII, Basic Fundamental Electronics by D-Sarda PART VII, Basic Fundamental Electronics by D-Sarda PART VI, Basic Fundamental Electronics by D-Sarda PART V, Basic Fundamental Electronics by D-Sarda PART IV, Basic Fundamental Of Transistors by D-Sarda, Basic Fundamental Electronics by D-Sarda PART III, Basic Fundamental Electronics by D-Sarda PART II, No public clipboards found for this slide, Enjoy access to millions of presentations, documents, ebooks, audiobooks, magazines, and more. Let us assume that the industrial power network is connected through the power line V1 and supplied from the 22 kV external distribution network. That means, rated voltage of circuit breaker corresponds to the highest system voltage. The impedance offered by the system to the flow of zero sequence current is known as zero sequence impedance. It determines the maximum value of current that will flow under fault conditions. 2.3 Fault levels The design fault level limit for 11kV network is 250MVA/13.12kV (RMS Break) and the 11kV switchgear is usually rated equal to the design limits. design and operation of protection devices. 27-36. doi: 10.11648/j.epes.20140302.13 Abstract: The aim of this research work is to carry out fault analysis of 11KV distribution power system . /Contents 4 0 R This may not be the case for old power station sites where non-standard arrangements are used or where impedance earthing is not used (5 MVA transformers). Learn More Short Circuit Analysis Using ETAP | IEC 60909, Learn More Circuit Breaker Short-Circuit Duty Calculation | IEC60909. Q3. Prof, PhD, PEPC, IntPE. The good news is fault events can be minimized or avoided through diligent electrical design, accurate record keeping information on equipment/devices/motors, proper installation, and use of agency-certified equipment. These high levels typically require line tripping to remove the fault from the system. The determination of the level of short-circuit current at any point of an electrical network can be of interest because of several reasons, e.g. % The single line diagram of an 11 KV substation is shown in the figure below. Maximum allowable fault levels set out by OEB Nominal Voltage (kV) Maximum 3-Phase Fault (kA) Maximum SLG fault (kA) 500 80 (usually limited to 63 kA) 80 (usually limited to 63 kA) 230 63 80 (usually limited to 63 kA) 115 50 50 44 20 19 (usually limited to 8 kA) 27.6 (4-wire) 17 12 27.6 (3-wire) 17 0.45 13.8 21 10 Table 2. You can refer to the table of voltage factors from this link. Pad mount and ground substation size is also written on the tank. In practice, the fault level plays a key role in system protection design and relays co-ordination . The fault level at the bus is. Ltd. Meerut, Installation, Testing and Troubleshooting of Transformers, Generator protection calculations settings. This is usually achieved by opening the circuit breaker connecting two sections of a substation or generating station busbar. . Regards, Shaheed P PhilCorso Lets see the calculation Learn More: What is Step potential and Touch Potential and Calculation 10 KV X 110% = 11 KV 20KV X 110% = 22 KV 30 KV X 110% = 33 KV 60 KV X 110% = 66 KV 100KV X 110% = 110KV 120 KV X 110% = 132KV I hope this is not too late but to answer your question, the constant C is taken from the voltage factors recommended in the IEC 60909. The action you just performed triggered the security solution. This means, the fault level on the primary side of the transformer is considered to be infinite. For overhead power lines, the short-circuit MVA can be calculated directly from the impedance in form Zv=R+jX, therefore we can write. Activate your 30 day free trialto continue reading. By whitelisting SlideShare on your ad-blocker, you are supporting our community of content creators. I am result oriented Engineer with long practical experience in field engineering, construction supervision of projects, engineering services, Plants operation, reliability & maintenance, and engineering consultancy. Diversified in setting up, and development of Feed and detailed design for electrical & Instrument installations for building services, Infrastructure, power house, gas . The circuit breaker should be capable of Breaking & Making current as per their ratings & should also have Rated short time capacity. Actual Fault Current available at AC distribution board . Next, for the 69/12kV X=0.076 p.u. Experience in maintenance, testing and commissioning of C&R panels, switchgear panels, Transformers, CB, CT, PT, relays, earthing, battery charger and control wiring at 66/33/11kV voltage level. If youd like more detailed fault level information, you can complete our online enquiry form. Thus, higher fault level, i.e. The methods calculation short-circuit currents vary in complexity and the amount of effort put into. The first step of calculation procedure is to convert classic single-line diagram of the power network to an equivalent MVA diagram. Short circuit level 25 KA r.m.s at 33000 volts b- 11 KV system Nominal voltage 11000 volts Highest system voltage 12000 volts System 3-phase,3 wire with neutral earthed through an earthing resistance of 21.1 ohm to limit earth fault current to 300Amps. Please let us know here why this post is inappropriate. This ebook covers tips for creating and managing workflows, security best practices and protection of intellectual property, Cloud vs. on-premise software solutions, CAD file management, compliance, and more. stream 132/33/11 kV substation system using ETAP software. increasing rapidly but generation is not up to the level of demand. In previous fault calculation, Z 1, Z 2 and Z 0 are positive, negative and zero sequence impedance respectively. Dear Sir, /F1 6 0 R Worked on oil and gas industrial projects performed power system studies, to select major electrical equipment . Your IP: Now we can reduce the equivalent MVA diagram. System voltage: 11KV Considering 10%, -ve tolerance voltage: 9.9KV Xfmr impedance (Assumed): 9% Considering 10%, -ve tolerance voltage: 0.08 or 8% Fault contribution from Xfmr: MVA/Xd"= 246.91MVA Fault current KA: MVA/ (1.732*KV) = 246.91/ (1.732*9.9)=14.40KA Now Total fault level: 8.33+0.89+14.4=23.62KA. ]+Ijq G 9,K!U{.# /Length 3674 Learn methods and guidelines for using stereolithography (SLA) 3D printed molds in the injection molding process to lower costs and lead time. For 66/11 kV substation, following minimum electrical & safety clearances are required. Determine the fault current and fault MVA. Selecting P base as 20 MVA and V base as 11 kV and using the above equations: and the Line-Neutral voltage on the secondary of the transformer is 0.4/3 = 0.230 kV, giving: Three Phase Fault Example Three Phase Fault Example During the study, the condition of all relevant equipment for power distribution at the 11 kV level was assessed. Three Low Voltage Fault Tables. An excellent and very helpful article.Missing are only the calculations to detemine the value of the total impedance Zfault=0,353 ,which I think would be very useful.Kindly advise