Dear Sir, The Fault lvel in india is considered as 350 MVA. We design our electricity network (or distribution system) to meet the maximum fault currents set out in the table below. We design our electricity network (or distribution system) to meet the maximum fault currents set out in the table below. Based on the available statistical data, Ekiti State is reported to suffer from severe . >> Solution: Alternator percentage reactance is based on its own voltage and kVA ratings. 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). Three 15MVA transformers, connected in parallel, are used to step down to an 11 kV busbar from which six 5 MVA, 11 kV motors are supplied. EPS and Energy managers association. The transformer fault level calculator assumes that the transformer is supplied from an infinite bus. Single Phase with Cable Run. The action you just performed triggered the security solution. Please select system type from these two: Three Phase. The embedded hardware primarily includes the processor, memory, bus, peripheral devices, I/O ports, and various controllers. Welcome to the forum, we are UK based as stated above, however calculating the fault levels are the same. calculation of induced voltage in telecommunication lines caused by high-voltage or extra-high-voltage networks. << The next steps are based on the simplification of an equivalent MVA diagram to one final value of MVA at the fault point (this represents short-circuit MVA at the fault point). Looks like youve clipped this slide to already. 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. security level of the 11kV distribution system. 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. Ground overcurrent and directional overcurrent relays are the typical ground fault protection solution for such systems. We pay respect to Elders past and present. People confuse your ability to perform with your ability to interview. thanks much. G36 - The impedance of the MV network referred to the LV side of the MV/LV transformer Electrical Engineer at Trident Group India, Do not sell or share my personal information, 1. Now, whether you use 12.5kA breaker or 20kA breaker cannot be decided without understanding the fault levels in your system. Fault Level Calculation For Generator . 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). A transformers nameplate details are 25 kVA, 440V secondary voltage, 5% of percentage impedance, calculate the short circuit fault current. A low-energy, slow, apathetic interviewing style will communicate low-energy, Why Ask This Question? Thanks. /Type /Page For complete information about the cookies we use, data we collect and how we process them, please check our, actual instructions in flowcharting are represented in, University Of Richmond Basketball Records, Does Due Diligence Period Include Weekends In Georgia, rhode island groundwater classification map. The group currently is currently S.Mathankumar 1, V.Agalya ,Member IEEE . 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 . Maximum short-circuit (three-phase) levels normally experienced in the British system are as follows: 275 kV, 15000 MVA; 132kV, 3500MVA; 33kV, 750/1000MVA; 11 kV, 150/ 250 MVA; 415 V, 30 MVA. The 132 kV busbar three-phase fault level is equal to 100 MVA/0.0188 pu = 5319 MVA and this corresponds to a three-phase fault current of 5319 MVA/ which exceeds the 21.9 kA rating. Normally fault level depens on the client requirment. Hence there is need of load flow management. Enter your email address to subscribe and receive notifications of new posts by email. 50 MVA MVA 10.21% 132/33-11 kV Harsool 50 MVA 132/33-11 kV 10.88 % . Learn More Short Circuit Analysis Using ETAP | IEC 60909, Learn More Circuit Breaker Short-Circuit Duty Calculation | IEC60909. Home for the terminally bewildered, one step ahead, New Solar PV design - split system (u/floor heating + domestic supply), Using a Clamp-on Ground Tester for normal & isolated grounds measurements, Do-It-Yourself (DIY) Question & Answer Forum, Options to protect cables entering consumer unit. You can email the site owner to let them know you were blocked. as above. Figure: Power System Network. Now we can reduce the equivalent MVA diagram. We pay respect to Elders past and present. This is in order to account for the system prefault conditions. h. Maximum system fault level at 33 kV & 11kV bus es shall be 26.2kA for 1 sec & 18.3kA for 1 sec respectively. Pad mount and ground substation size is also written on the tank. The kit shall be used for cable types namely XLPE, PVC, PILC with Al / Cu conductor. Weve updated our privacy policy so that we are compliant with changing global privacy regulations and to provide you with insight into the limited ways in which we use your data. ]+Ijq G 9,K!U{.# 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. By accepting, you agree to the updated privacy policy. 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. 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. It's recommended this table is used when designing your network. Voltage (kV) Impulse Voltage (kV Peak) Power Frequency Voltage (kV) 1 0.433 - 3 2 11 75 28 3 33 170 70 11 LOSSES: 11.1 The transformer of HV voltage up to 11kV,the total losses(no-load + load losses at 75 0C) at 50% of rated load and total losses at 100% of rated load shall not exceed the maximum total loss and hence 2, 2014, pp. Register to receive SMS notifications for power outages in your area. Infintite bus assumption. 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. 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. EHT Substations -1.0 . Fault levels are most commonly modelled using power . . 3000v + 300v = 3.3kVetc. 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. 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 If the downstream LV fault level is required (overhead area) you should visit the site and determine conductor sizes and length. [1] Jaffari, H.: Fault Current Calculation. If you have lost power or are experiencing electricity supply problems. [5] Pauza, J.: Short-circuits in electrical networks. Two 11kV feeders will be provided for the supply to the high voltage chillers at WKT. 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. The single line diagram makes the system easy and it provides the facilitates reading of the electrical supply and connection. What is the fault level for a fault on one of the feeders near the bus bar? Discover how this hybrid manufacturing process enables on-demand mold fabrication to quickly produce small batches of thermoplastic parts. A microprocessor is the center of the system, with storage devices, input and output peripherals, a power supply, human-computer interaction devices, and other necessary supporting facilities. Oct 2007 - Sep 20092 years. The pole-mounted sub-stations are generally used for transformer capacity up to *200 kVA. There are several actions that could trigger this block including submitting a certain word or phrase, a SQL command or malformed data. EE 423 - Power System Analysis: Faults - J R Lucas - October 2005 5 Example: A 200 MVA, 13.8 kV generator has a reactance of 0.85 p.u. When the insulation of the system fails at one or more points or a conducting object comes Philosophy change to primarily operate the 11 kV system as a single power system island. The short circuit impedance can be specified for the sub-transient, transient or steady state phase of the generator fault. Next, for the 69/12kV X=0.076 p.u. Clipping is a handy way to collect important slides you want to go back to later. C : 500 MVA. Free access to premium services like Tuneln, Mubi and more. Summer Training presentation on 132/33 KV sub-station Minto park, Allahabad, Sudhir Cement Industries Pvt. The fault level calculations for three-phase fault and single line to ground faults are carried out for all the three types of 6.6KV/0.433KV LT Transformers in service at XYZ PLANT Base KV =6.6KV/0.433KV. Valid from 1.10.2016. 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 fault currents correspond to a worst-case transformer impedance of 90% of nominal impedance, as transformer standards allow for a 10% tolerance on nominal impedance. In static and balanced power system components like transformer and lines, the . >> /MediaBox [0 0 595 842] 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. = 268.13 MVA, 14073 Amps. Let us assume that the industrial power network is connected through the power line V1 and supplied from the 22 kV external distribution network. It is evident that it follows the UTILITY capacity, since it's being lesser compared to. Single Phase with Cable Run. A comparison of the results between the two methods is shown in the following table. Thank you very much for your reply FAULT LEVEL CALCULATION SUMMARY<br>More than 18years' experience in engineering & design of large industrial, electrical generation power plant and petrochemical plants. Performance & security by Cloudflare. Many thanks. A : 1000 MVA. These values also assume an infinite HV bus is applied at the transformer at 1.0p.u. Fault level limiting in 11kV distribution, Electric power & transmission & distribution Forum, Low-Volume Rapid Injection Molding With 3D Printed Molds, Industry Perspective: Education and Metal 3D Printing. 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. By whitelisting SlideShare on your ad-blocker, you are supporting our community of content creators. As you know, interviewing is a staged, contrived event. The transformers are delta-star connected with the star point of each 11 kV winding, solidly earthed. fault level at the end of the feeder, Approximately 2kA ph.-E fault level at the start of the feeder, Approximately 1.5kA ph.-E fault level at the end of the feeder, Typical OH 11kV feeder conductor is 7/4.75AAC, Typical UG 11kV feeder conductor is 240mm Al. In such cases, it becomes necessary to increase the area of the grounding network. A 3-phase short circuit occurs at its terminals. >> wn|3h;rmoxw.0~58BB&_*Hx/d~n-*~YP!6V63W_QbPBsUQ;O62G _`c CO,'0Aa This is due to the impedance earthing used at these levels. Joined: 12 January 2012. Prague, Czech Republic, 2013. From . Table 1. Follow our social media channels to get the latest updates on Energex's work in South East Queensland. You are using an out of date browser. High voltage fault level limits. 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. You must ensure that any circuit breakers/switchgear on your side of the connection point that isolate your premises from our electricity network have sufficient ratings to safely break the fault currents (both active and reactive) that may occur on our network. Thank you for helping keep Eng-Tips Forums free from inappropriate posts.The Eng-Tips staff will check this out and take appropriate action. }i%G9"Ucj8/RrdssK~J=Y]4$\2.I$7s7 7`w~cIy@= :R.Wjo.uVnPYhF.R,.R` 52-} Three generators rated 100 MVA, 11 kV have an impedance of 0.15 pu. The aim of this research work is to carry out a fault analys is of 33KV distribution system using Ekiti state as a case study. Prof, PhD, PEPC, IntPE. Worked on oil and gas industrial projects performed power system studies, to select major electrical equipment . Site growth took our fault level beyond the existing equipment's 250MVA rating with a predicted level of 350MVA. Our nominal maximum (design) fault level is 13kA (250MVA). There are several methods for the calculation of short-circuit currents. All reactances on a 100 MVA base. It determines the maximum value of current that will flow under fault conditions. *Eng-Tips's functionality depends on members receiving e-mail. 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. 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. 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? This is based on a zone substation transformer rating of 15 MVA (33/11 kV, Z =8.6%). The following concepts are used while planning BigchainDBs safety efforts: , (Blockchain, Big Data and Machine Learning: Trends and Applications). Result : Maximum value of Fault at 11 kV Bus is only 0.223 KA against 3.669 kA capacity of Transformer. The first step of calculation procedure is to convert classic single-line diagram of the power network to an equivalent MVA diagram. I'm working on an old 11kV system with a mixture of old padmounts and ground mounted tx's. 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 selectively provide your consent below to allow such third party embeds. There is no way the lead sheath can support such current even if maximum fault-clearing time (assuming an instantaneous-element EF relay, like a 50N) were 50 ms! Actually, the total impedance, Zfault, is the equivalent impedance i.e. Finally, the initial symmetrical short-circuit current at the fault point can be calculated from the equivalent network MVA. We've updated our privacy policy. Earth-fault current in the 11kV system could be well over 100kA (peak!) 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.<br><br>worked with Siemens PLC S7-400 and also on the WINCC redundancy <br>worked on Constant Current Regulator (CCR) of high voltage of 30 kv, 25 kv, 20 kv, 15 . Cloudflare Ray ID: 7a2e4a305f529441 Delhi, India. contact us with an enquiry. Responsible for Power system studies and Design of Doha International Airport, Qatar Petroleum NGL facilities, and offshore platforms. Guidelines for 11kV level 11kV is the medium voltage distribution level; the primary stations are 220/11kV, 132/11kV, 66/11kV or 33/11kV and the distribution substations are 11/0.433 kV. Star Lesn, Slovakia, 2001. presentation on substation layout and BUS bar arrangement. As a . b. 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. Standard distribution transformer LV fusing information can be found within the Overhead Construction Manual (PDF 8.0 mb) and the Underground Construction Manual (PDF 21.5 mb). A 33 kV System can be designed for 31.5 kA , a 132 kV System is designed for 40 kA with highest fault current for the transformer is considered. straight forward. 11KV : Amp Rating : 1250 A : Fault Level : 25 KA : Minimum Order Quantity : 1 Set : View Complete Details. This article deals with an alternative method for the short-circuit current calculation so-called the MVA method. FAULT LEVEL CALCULATION Dinesh Kumar Sarda 2. Welcome to schneider electric's fault current calculator. Copyright Energex 2023. 66/11 kV Stations -2.0 . For sake of simplicity, we consider only one synchronous generator, TG, and one synchronous motor, SM1 in the industrial power network. The fault level at the bus is. Please let us know here why this post is inappropriate. (Triple Zero) To report life threatening emergencies like fallen powerlines or shocks & tingles. The earthing fault level dataset includes the three-phase and single-phase to earth fault levels for all Grid (132kV, 66kV, 33kV) and Primary (33kV, 20kV, 11kV, 6.6kV) substations based on the UK Power Networks Long Term Development Statement (LTDS). The table below lists design fault level limits that apply at our installations. Fault level increases due to external factors are monitored by annual fault level reporting, which estimate the prospective short circuit fault levels at each substation. For simplicity, resistance will be neglected. Work Record : Feb - 2016 to Feb-2018<br>Position : Electrical Technician (Operation & Maintenance)<br>Company : Federal Electricity and water authority<br> Working in Centralized Operation & Maintenance Department, Maintenance of Substation & Condition monitoring (Transmission line like power transformer, OHL feeders 220kv/132/33 KV, cable feeder, towers, PMTs, OPGW, tower earth resistance . internal voltage of all sources is equal to 1 (in per unit). So they had planned to deliver the desired voltage with 10 % as extra (110%) to match the transmission loss and line drop. the lower impedance, implies that the power system is stronger at that point and vice versa [1, 2]. 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). Each 132 kV line is 40 km long and with an inductive reactance of 0.4 V/km. [7] STN IEC 60909 0: Short-circuit currents in three-phase a.c. systems. The FCL enables the substation to run with all three 33/11-kV transformers connected to the 11-kV bus bars with a fault level of 11.3 kA. 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. 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 . Power System Review: Module 6. is installed at the low voltage side of the transformer to protect the cable and the consumer. 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. /ProcSet [/PDF /Text ] The embedded software usually contains (Android Application Development for the Intel Platform). 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. 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. Hello! Q2. Posted By : / actual instructions in flowcharting are represented in /; Under :nose exercise before and afternose exercise before and after As a result, the fault level throughout the system also increases accordingly. used in the distribution lines to the level used by the customer. single line to ground fault and determine the GCS/4/01 and 02 THerefore the maximum fault level at 11kV will be 2.5 divided by 0,0675 (pu) = 37.037MVA. 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. [4] Mslo, K., Novk, J., Doleal, J.: Analysis of short-circuit currents. I have discussed it in other parts of this book, but you must always communicate a high energy level. A hard-wired protection system that automatically disconnects generators from the network under pre-defined conditions, typically in . 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) By way of example, consider a 2 MVA transformer with an impedance of 5%. At each voltage level the fault level can be ascertained from the reactances given. Fault level at 11 KV: Actual fault level at 11KV Bus Let the base MVA % Impedance of the system at source V. Fault level at 2.5MVA Transformer Transformer KVA Voltage rating Impedance of the transformer = = = = TOTAL FAULT IN 415V BUS: Z4 and Z5 are in series Total P.U in Transformer end (Z0) = Z4+Z5 = 0.0123 + 0.07 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. Since the system operates normally before the fault, there will be no current I f through that source. Cloudflare Ray ID: 7a2e4b01efca1cee New consumer unit required - does it mean none fire rated down lighters need replacing? If rotating machines are present at 3.3 kV, 6.6 kV and 11 kV levels, the systems are grounded through resistor or reactor to limit the ground fault current. 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. A1-6 Fault level on 11kV side for percentage impedance = 100 x 10 = 97.98MVA Of 10.206 (from A1.5) on 10MVA base 10.20 A1-7 Length of 11 KV overhead line from 66KV sub Station to factory site = 1.5KM A1-8 Size of conductor = Mink A1-9 Resistance of Mink conductor = 0.456 ohnm/KM . Our short term solution involved two tapped reactors (operating in parallel) to segregate the older 250MVA network from the new 350MVA rated equipment. What is the fault level in 11kV? A 3-phase, 10,000 kVA, 11 kV alternator has a sub-transient reactance of 8%. Primary Functions of Current Limiting Reactor. Street lighting, as well as the switching control for street lighting, can be installed in a substation. control of propagation and impact of upper harmonics in power system. Click here to review the details. If you are using our Services via a browser you can restrict, block or remove cookies through your web browser settings. 3.1.6 Three phase fault levels are generally higher than single phase fault levels for the 33kV and 11kV network. For a better experience, please enable JavaScript in your browser before proceeding. You can open the feeder loop somewhere and close it in (automatically or manually) if you lose one source. Please note that there may be a fee for this service. That means, rated voltage of circuit breaker corresponds to the highest system voltage. A consumer is supplied at 380V 3 phase from a 11 kV substation through a 1500 kVA 11kV/380V transformer and a 380V cable as shown in Fig. Your IP: 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. This will involve an additional 11/33kV transformer and associated switchgear. It appears that you have an ad-blocker running. We want to find the fault level at the transformer secondary. voltage. Now customize the name of a clipboard to store your clips. 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. We've encountered a problem, please try again. Your IP: contains simple formulas for calculation (in comparison with other methods). Fault Level Calculations 8 What is fault level ABC Transmission Co. Ltd. 3 Ph Fault Levels For 2010- 2011 14530 MVA 18290 MVA 9700 MVA 8400 MVA 11300 MVA 4630 MVA 5800 MVA 6400 MVA 7200 MVA 2700 MVA 1185 MVA 3670 MVA 9730 MVA S/S - B S/S - A S/S - C 14530 MVA 8400 MVA 9730 MVA S/S - B. Figure 1-2 shows a configuration diagram of a typical embedded system consisting of two main parts: embedded hardware and embedded software. The impedance of the transformer and the 380V cable are shown in Fig. Design of LV Electrical and DCS, PLC and Controls schemes design system for Submarine (New Generation type Scorpene) Understanding the technical & contract documents from . Maximum short-circuit (three-phase) levels normally experienced in the British system are as follows: 275 kV, 15000 MVA; 132kV, 3500MVA . << Part 0: Calculation of currents. The sequence impedance varies with the type of power system components under consideration:-. 3.3kV contactors are only available rated to 9,000 Amps short circuit Welcome to schneider electric's fault current calculator. It should be noted that the short- circuit level will change with network conditions, and there will normally be two extreme values: that with all plant connected and that with the minimum plant normally connected. It may not display this or other websites correctly. Keywords: short-circuit current, the MVA method, calculation methods. Also known as the Impedance Method. Apply effective risk management The electric power industry will continue to make distribution system reliability and customer-level reliability a top priority. 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. [mcq] power system operation and control , power system operation and control mcq , power system operation and control mcq pdf . Close this window and log in. transformer from the consumers in the event of any fault. In this paper, the last factor, i.e. each. Some of them are listed below: This method can be used when the task is limited only to finding the short-circuit current at the short-circuit location. Voltage level (kV) Short circuit level (MVA) Short circuit level (kA) 132kV . I can recommend a site that has helped me. clear and easy to follow. It's recommended this table is used when designing your network. The maximum rating of 11 kV SF6 or vaccum circuit breaker is assumed to be 4000 amps as allowable rated continuous current. These can be divided into numerical and numeric-graphical methods. The next steps are based on the simplification of an equivalent MVA diagram to one final value of MVA at the fault point (this represents short-circuit MVA at the fault point). Power availability in the 33/11kv injection A simplified calculation is often sufficient. Your browser is out-of-date. The between - bus reactors are a real challenge on indoor metalclad switchgear when done as a retro-fit! Load . Recent plans to augment some substations by adding another transformer means that the fault level will go above this (and beyond the CB capacity) unless we take action to limit it. The single line diagram of an 11 KV substation is shown in the figure below.