Abstract: There are alot of methods that can be used for short-circuit current calculation. 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. Cream Magazine by Themebeez, Fault Level Calculation Using The MVA Method, Short Circuit Analysis Using ETAP | IEC 60909, Circuit Breaker Short-Circuit Duty Calculation | IEC60909, Calculation of MVA level of each element of the electrical network, Short-Circuit Currents | 3-Phase VS 1-Phase, Practical Evaluation of a Power Fuse Interrupting Capacity, Vector Group of Transformer Dyn1|Dyn11|Ynd1|Ynd11, kAIC Rating of Circuit Breakers | Calculation in Low Voltage System. For an underground area, engage an Exclusion Zone Officer who can assess conductor sizes, for example lift pillar lids, open pad mounts and ground substations. Earth-fault current in the 11kV system could be well over 100kA (peak!) 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. I'm working on an old 11kV system with a mixture of old padmounts and ground mounted tx's. 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. As more site load is added and extra embedded generation installed, the taps are changed to limit the site fault level. 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. Join your peers on the Internet's largest technical engineering professional community.It's easy to join and it's free. Responsible for Power system studies and Design of Doha International Airport, Qatar Petroleum NGL facilities, and offshore platforms. The FCL was installed on the 11-kV side of transformer T3, with a rating equivalent to the transformer (10-MVA nominal, 15-MVA overload). 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. 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. The sequence impedance varies with the type of power system components under consideration:-. Based on the available statistical data, Ekiti State is reported to ThinkScan SR2 car code scanner supports 4 in 1 data display, saves, reads and prints health reports. The short circuit impedance can be specified for the sub-transient, transient or steady state phase of the generator fault. All rights reserved. Please select component: Add Primary Cable Run. Now customize the name of a clipboard to store your clips. 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. 3, No. Keywords: short-circuit current, the MVA method, calculation methods. Energex acknowledges the Traditional Custodians of the land on which we live and work, and recognise their continuing connection to land, waters and community. 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. 132/33/11 kV substation system using ETAP software. Fig. Electric power is an essential facilitator for sustainable development of the modern nation state. We've updated our privacy policy. ABB. 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. Hand written calculations are hard and laborious often flawed because of all the conversions required. At each voltage level the fault level can be ascertained from the reactances given < Prev CONTENTS : Source Next > Fault Levels in a Typical System. Next, for the 69/12kV X=0.076 p.u. (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 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. The pole transformer size is written on the transformer tank (for newer transformers) and is visible from the ground. As the transmission voltages increase, the short-circuit currents also increase, and for the 400 kV system, circuit breakers of 35 000 MVA breaking capacity are required. 10 INSULATION LEVELS: Sl. A : 1000 MVA. [2] Lee Wai, M., Pang, J.M. as above. The task is to find out the value of initial symmetrical three-phase short-circuit current at 6.6 kV busbar. In conventional power systems, the system . The between - bus reactors are a real challenge on indoor metalclad switchgear when done as a retro-fit! 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. Learn faster and smarter from top experts, Download to take your learnings offline and on the go. Maximum short-circuit (three-phase) levels normally experienced in the British system are as follows: 275 kV, 15000 MVA; 132kV, 3500MVA . 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. The table below lists design fault level limits that apply at our installations. 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. The substation is equipped with three 10-MVA 33/11-kV transformers, one of which runs on hot standby to avoid exceeding the fault-level rating of the existing 11-kV switchgear. It's recommended this table is used when designing your network. 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). 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. << >> Our short term solution involved two tapped reactors (operating in parallel) to segregate the older 250MVA network from the new 350MVA rated equipment. 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 other important aspect is the time in secs for the fault current. As a result, the fault level throughout the system also increases accordingly. 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. 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. 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. Transformer fusing information can be found within the Pole Transformer Fusing Standard. The typical hardware structure of an embedded system is shown in Figure 1-7. Electrical Engineer at Trident Group India, Do not sell or share my personal information, 1. 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). The MVA method is known to be simple, quick, and easy, and is sufficiently accurate for engineers in practice for basic estimation of fault levels at any point in an electrical network. Known embedded generators are added to our simulation models so that the impacts of these generators on the system fault levels are determined. Register to receive SMS notifications for power outages in your area. Distribution Annual Planning Report (DAPR), The South East Queensland electricity network, National Energy Customer Framework (NECF), Approximately 8-10kA 3 ph. Site growth took our fault level beyond the existing equipment's 250MVA rating with a predicted level of 350MVA. Next, for the 69/12kV X=0.076 p.u. The analysis is done by using This will involve an additional 11/33kV transformer and associated switchgear. This website is using a security service to protect itself from online attacks. The soil conditions considered are desert conditions and hence with poor resistivity. I'm interested in hearing about how people out there deal with the problem of controllong fault levels in 11kV distribution substations. The action you just performed triggered the security solution. /Type /Page New connections of distributed generation and embedded generations which increases fault levels are individually assessed to ensure limits are not infringed. For example, the equivalent MVA at branch A (consisting of network feeder, transformer T1 and power line V1) is. INTRODUCTION TO PROTECTIVE RELAYING.pptx, Series & shunt compensation and FACTs Devices, Electrical 132kv substation project .. shakir, Sample calculation-for-differential-relays. The equivalent short-circuit impedance at the fault point is calculated to be, If the value of initial symmetrical short-circuit current is known, the peak short-circuit current can be determined using. There are several methods for the calculation of short-circuit currents. 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. I can get the fault level at the LV board using Fluke 1653. The kit shall be used for cable types namely XLPE, PVC, PILC with Al / Cu conductor. Known embedded generators are added to our simulation models so that the impacts of these generators on the system fault levels are determined. 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