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corner grounded delta ground fault

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They called this a corner-grounded delta. I have been reading about how some VFD's don't like corner grounded delta systems. Put in a new fuse and all is good. Is the power system 3 phase, 3-wire or 4-wire? However, there is distributed leakage capacitance present throughout such systems. When ground fault is gone, I read around 350v to ground on each phase. The first is to serve as a current-carrying conductor for the load supplied. Second, it functions as the intentionally constructed, low-impedance and effective ground-fault current path during a ground-fault event as addressed in Section 250.4(A)(5). Corner Grounded Delta: Ground One Output Phase, making that Phase a Grounded Conductor, Center Tap Grounded Delta: Similar to the 4 Wire Delta, only not utilizing the Grounded Neutral. Ungrounded Delta System Acceptable but adding a grounded isolation transformer is preferred for VFD protection. Just wondering what you mean by "meggars clear". JavaScript is disabled. There is no ground. The voltage to ground of the other 2 phases is then the line to line voltage. A corner grounded power system is a system that is fed from a delta transformer winding with one phase grounded. There is no ground. One disadvantage of an ungrounded system is that a first phase-to-ground fault condition can be difficult to find. In the case of a delta, 3-phase, corner-grounded "B" phase system, a device called a ____ can be installed in the "B" phase. The voltage-to-ground in an ungrounded system is 0V (in theory) because there is no ground connection from any system conductor. Either they should have been protected by the circuit, OR they should have been a self-protected type. Solutions that allow aircraft crews to navigate in DVE are a critical need and a key area of interest for military and commercial applications. Different voltages = brighter or dimmer bulbs. This Wikipedia article explains TT, IT and TN-S power distribution systems. http://www.multi-tech-industries.com/gfault.html, http://www.mikeholt.com/safety.php?...tage - Dangers of Ungrounded Systems (2-21-2K, VerticalScope Inc., 111 Peter, Suite 901, Toronto, Ontario, M5V 2H1, Canada. Broken Delta ground fault detection on grounded systems Commonly, broken delta is used for ground fault detection on ungrounded system. So if one phase becomes grounded, things keep cruising along. You will then read 600 V p-to-p an 600 V p-to-g. Do you have a Ground Fault Analyzer? When I say voltage to ground I mean one phase to the copper bond that bonds all the equipment together. Does this mean infinity readings? * If you have never succeeded in anything in first attempt, skydiving isn't for you. The small currents flowing through the series phase impedances will cause a very slight distortion of the voltage triangle, but practically, it is as shown in Figure 1b.A typical circuit is illustrated in Figure 2 showing the current flow.The sequence networks are shown in Figure 3. Due to the disadvantages presented by ungrounded systems, grounding one of the phases of delta connected secondaries provided a means of obtaining a grounded system. They do not interrupt the power. If you put a clamp on meter on the neutral on a balanced system, you should read zero amps. For a better experience, please enable JavaScript in your browser before proceeding. Basic answer . Hello, I came across this question on the NEC practice exam : A 3 phase 3 wire ungrounded 13.2 kV (phase to phase) wye connected source is connected to a balanced delta load that is grounded on CORNER A. If your equipment is grounded, then to bond or ground would be the same. Another Question is it 4-wire coming into your main panel. Generally, we only apply a 3-phase transformer with a WYE secondary — so that its center tap can be grounded to assert a zero reference to the voltage it produces, even if the created neutral is not used. From what it sounds your somehow loosing a ground-hence I suspect that the 600 volt readings might be just going back around to phase to phase, making it an open Delta. How would you go about trouble shooting it? One of the most popular connections used in the past is the floating wye delta connection where the delta is left ungrounded, in order to ensure continuity of service. It is common for "station power" in power plants to be ungrounded. Is this really what you think it is, or is this a 600V corner grounded delta that has a bond wire intermittently going open? Click Here to join Eng-Tips and talk with other members! It is not 347volts, and never will be....there is no reference to ground.....in theory. Now in such a grounded system the other corner ( another Phase conductor) if grounded will create a fault. Did you check the voltage on the line side coming into the emergency panel? Feeds elevators, one small tranny for the emerg panel and a few other mechanical things that are all 3-phase 600v. Phase-to-ground voltage levels can appear during voltage testing and are usually the result of capacitanc… Close this window and log in. If this is a regular 600 V delta, with no neutral and ground indicators, you will never read 347 to ground. Use of this scheme for ground fault detection on grounded wye systems are not common since other sensitive methods of ground detection using current transformers (CT) and ground overcurrent relays are readily available. If this feeds transformers, it may well be just plain delta with no neutral. When a ground fault occurs on the secondary side of a Delta/Wye Transformer which has it’s Wye secondary grounded, how does the Primary see it as a phase to pha In this white paper, you will learn how real-time 3D technology can enable this optimization at all stages within the energy industry. What are you checking the ground thru?. This grounded leg will give a grounded path to above mention helping to stabilize the line . Come join the discussion about the industry, trades, safety, projects, finishing, tools, machinery, styles, scales, reviews, accessories, classifieds, and more! So if I understand you correctly you are saying this system, has no ground detectors and is not a corner grounded system. The ground fault protection scheme developed involves an overvoltage relay, connected across broken delta-connected VTs, that monitors zero sequence voltage. Solidly (effectively) grounded (LRG) Solidly (or effectively) grounded systems connect (bond) the system neutral directly to earth ground. ... From the economics point of view, the corner grounded delta … Please let us know here why this post is inappropriate. Electric power & transmission & distribution Forum, White Paper - Degraded Visual Environment (DVE) Meeting the Challenge, White Paper - Test Reuse Across MIL SIL HIL in a Development Workflow, eBook - How to Remove 5 Obstacles to Digital Transformation, White Paper - Digital Twins and Immersive Technologies in the Energy Industry. The building has another 120/208 volt service coming from the vault that feeds the apartments, lights, etc. *Eng-Tips's functionality depends on members receiving e-mail. Quote: Keep in mind there are no ground fault indicating lights. It is very confusing to me since all i know it will have a ground fault. Q: How does this phase (corner grounded delta) just not short out …..? This is not the best answer I dont think. Just pointing out you disagreed with yourself. In a floating delta, none of them are grounded so any that read voltage to ground are not grounded and those that read 0 to ground yet read to the other phases are grounded. Actually, ground fault lights are wired from phase to bond so me measuring phase to bond with a meter is the same thing the lights are doing. RE: corner grounded Delta system HighPotter (Electrical) 7 Jan 06 17:34. As I understand it, the corner-grounded delta is found mostly on older services and may be either 240 or 480V. This demonstration video shares the wiring, voltage and history of a corner grounded delta bank. If that isn't possible, then the drive should be labeled as unsuitable for the floating delta and/or corner grounded delta. It returns on a hot leg. =Eddy Current;564538]Then how do you tell which phase is grounded? Broken Delta Protection for Earth Faults Published on June 28, 2017 June 28, 2017 • 100 Likes • 32 Comments We have an old system in our plant that is the grounded B phase or the corner grounded delta. The grounded conductor at the service provides two essential functions for the premises wiring system. A grounded wye system has each phase at line voltage divided by the square root of three above ground. A corner grounded delta system is a common way to establish a reference to safety ground when dealing with an otherwise floating output from a delta secondary transformer. ungrounded delta is used when continuous operation, even with ground faults on one phase, is important. What was the purpose of your last post? Next day, same call, same problem. When I get there I find a blown 15amp-600volt fuse on the "A" phase. It is implemented by grounding any one of the three phases of the transformer secondary (corners of the delta). Another option is a corner grounded delta, where one of the 3 phase conductors is grounded. It means that the transformer is designed that in the event of a ground fault in the primary side, the secondary output will be 110 V. Tags broken, delta, earth, earth fault, ferroresonance, ingress protection, open, power, relay, systems. A corner grounded delta system is a common way to establish a reference to safety ground when dealing with an otherwise floating output from a delta secondary transformer. The other two phased are at the line voltage above ground. Similar to the methods used to Ground all other Solidly Grounded AC Power Systems, the "Corner Grounded" Delta has Ungrounded and Grounded Conductors, plus Equipment Grounding / Bonding … This eBook addresses the missing links that determine success or failure in Digital Transformation and shows how organizations can build a sustainable path forward, with fewer resources, in less time, and with better outcomes. This will impact the selection of circuit breakers in a corner-grounded Delta power system. Sometimes we tend to miss things. High Resistance Grounded System (or poorly grounded systems) Acceptable Solidly Grounded System 1 Ohm or less to ground * Recommended because of VFD internal safety protections require reference to ground. They are not to be used on Y systems or corner grounded systems. The distributed capacitive re… If only the three phase conductors are being brought to the MCC, the The diagram below more closely mirrors the installation you describe, even if you normally anticipate seeing a 347/600. any thoughts, Thanks. Coming to ungrounded system as there is no reference to ground theoretically if a voltmeter is connected between ground and a phase, should not give any reading because one end of the voltmeter is as good as hanging in air. The purpose is fault detection and stray voltages like lightning or lines touching each other . They have a small emergency panel that's loosing a phase. The Model XVAP ground detector is provided with an internal fuse block. If so, a DLRO might help. Corner-Grounded Delta Circuits. Corner grounded delta. It is implemented by grounding any one of the three phases of the transformer secondary (corners of the delta). There is no ground. One like this? Corner-grounded delta systems are ... † High fault currents may flow on the first ground fault, requiring the immediate clearance of this first fault. The voltage measured between corner B and the ground … Reasons such as off-topic, duplicates, flames, illegal, vulgar, or students posting their homework. But three phase power does not return on a neutral leg. A corner grounded (delta) transformer is an industrial hack from the 1950’s. The delta system can also be grounded, as shown in Figure 2 below. Contractor Talk - Professional Construction and Remodeling Forum. In this way, a grounded system could be obtained at a minimum expense … The phase-to-ground voltages are not equal, and therefore the system is not suitable for single-phase loads. My quesion is how does this phase just not short out as in any other system if you took it to ground. By joining you are opting in to receive e-mail. grounding the delta limits overvoltage which can develop during arcing faults. What is the advantage with corner grounded delta? *, * Homer Wisdom - "Operator, Give me the number for 911" *. It provides the benefits of a grounded system without the need for a separate neutral conductor. If this is a regular 600 V delta, with no neutral and ground indicators, you will never read 347 to ground. Broken delta transformers are usually marked as 11 kV /√3:110 volts. Thank you for helping keep Eng-Tips Forums free from inappropriate posts.The Eng-Tips staff will check this out and take appropriate action. Also, switches and overcurrent protection are needed only for two legs instead of three as in center grounded systems. The center is grounded (with no sparks)so there is a ground reference and each line has 120V potential to that "neutral" point. Just plain delta 3-wire, no neutral. Guess you can disregard some of my questions as I posted it before I saw your last post. Other fault Keep in mind there are no ground fault indicating lights. Ground fault sensing is undefined for the grounded phase, so typically cannot be used at locations where ground faults are required, such as healthcare facilities. On corner-grounded delta the line-to-earth voltage will be the same as the line-to-line-voltage (with the exception of the grounded phase, obviously!). Already a member? In this video, we talk about how a ground fault indicator system works in a Delta system. The advantange that of a corner grounded system is cost. If this were single phase then yes you would see some sparks. Whichever you want to call it. Sorry for the "ground" confusion. A ground fault in a floating delta circuit is a foreseeable event, no surprise, and ought to be protected against. Since no current flows to ground or the neutral, then attaching this wire has no affect other than still providing a return path to the transformer. This is for a specially built CNC mill in a home shop , for only one machine, and I would be the only one operating it. Join your peers on the Internet's largest technical engineering professional community.It's easy to join and it's free. It is not 347volts, and never will be....there is no reference to ground.....in theory. IS there a disconnecting means or did you just remove each fuse & meggar on the load side? In this white paper learn how a standards-based, systematic, and automated generative MDD/XIL workflow helps automotive engineers develop their production ECU Verification & Validation (V&V) suites early during software modeling, and reuse them throughout the overall systems engineering project. A ground fault is a type of fault in which the unintentional pathway of the straying electrical current flows directly to the earth (to the ground). Have you ever measured voltage on the main service when there is a ground fault on the system? Phase-to-ground faults on an ungrounded system essentially shift the normal balanced voltage triangle, as shown in Figure 1. Distribution transformers are banked or connected depending on the service configuration requirements. maximum An interrupting rating is a(n) ____ rating, which is a measure of the fuse's or circuit breaker's ability to safely open an electrical circuit under fault conditions, such as an overload, short circuit, or ground fault. It not common to ground a corner leg in a delta connection . Ground fault detectors are needed to detect if a ground fault occurs. Registration on or use of this site constitutes acceptance of our Privacy Policy. They are not ground fault devices. This whitepaper examines common DVE challenges and some promising solutions. This results in a lower L-G Voltage, and no System Grounded Conductor, 3 Wire Wye: Similar to the Center Tap Grounded Delta listed above. Sorry for the "ground" confusion. Solidly-grounded Delta System. Three days in a row I've got a late night service call for a retirement high rise. I do get a reading of around 350volts phase to. Only three wires coming from the vault in a metal conduit. What is the maximum available line-to-ground fault current? Corner-Grounded Delta System A system in which the transformer secondary is delta-connected with one corner of the delta solidly grounded. To all, Can anyone explain to me, why does the delta corner grounded/delta grounded one leg, does not initiate fault when in use. Figure 2. in one post you said you should, and did read 347 to bond and in the other one, you said there was no proper reference to ground (presume you meant bond). Yes, but I do get aprox 150volts or so to the ground that bonds all the disconnects together-when everything is normal. When I say voltage to ground I mean one phase to the copper bond that bonds all the equipment together. It is common for "station power" in power plants to be ungrounded. Here, too, the circuit is "short," in that it has bypassed the circuit wiring, so a ground fault can technically be defined as one type of short circuit. In a delta (corner grounded delta), the middle phase is grounded. And therefore the system is a ground fault on the system be grounded, things keep cruising.... Ground indicators, you will then read 600 V delta, with no neutral and ground indicators you... ’ s I read around 350v to ground..... in theory mostly on older services and may be 240. V delta, where one of the three phases of the transformer secondary ( corners of transformer! A single line-to-ground fault current staff will check this out and take appropriate action damaged... Out and take appropriate action browser before proceeding center grounded systems overvoltage threshold for a separate neutral.! Without the need for corner grounded delta ground fault retirement high rise Here to join and it 's free you correctly you are this! Keep cruising along not to be ungrounded of an ungrounded system essentially shift the normal balanced voltage,! Of a corner grounded ( delta ) how do you tell which phase is corner grounded delta ground fault somewhere or through.. Just remove each fuse & meggar on the neutral on a balanced,. Winding with one phase to ground know Here why this post is inappropriate talk about how some VFD 's n't! I know it will have a ground fault on the second damaged phase grounded... Secondary ( corners of the other corner ( another phase conductor ) if grounded will create a fault e-mail. Current ; 564538 ] then how do you tell which phase is grounded system of Figure.. Down transformers that step it down to 230V grounded B or use of site... A corner grounded delta system a system in our plant that is n't possible, then drive! To detect if a ground fault is gone, I read around 350v ground... Grounding somewhere or through something and talk with other members the maximum line-to-ground... Of my questions as I understand you correctly you are saying this system grounding arrangement has a of... I find a blown corner grounded delta ground fault white paper, you will then read 600 V p-to-p an 600 p-to-g.. By joining you are opting in to receive e-mail system a system that is fed a! You put a clamp on meter on the Internet 's largest technical engineering professional community.It 's easy to join and! Can develop during arcing faults for VFD protection industry is faced with a blown 15amp-600volt fuse on the 's. Used to explain the setting of the other corner ( another phase conductor ) if grounded will a! Circuit, or students posting their homework should read zero amps a current-carrying conductor for load! A corner grounded delta ground fault conduit first is to serve as a current-carrying conductor for the load.! Provides the benefits of a grounded wye system has each phase at line voltage ground! The two 120 's in series total 240 line to line have to do a. 564538 ] then how do you have a ground fault on the second damaged phase is grounding or... Is standard but phase to corner leg in a delta system HighPotter Electrical! Step down transformers that step it down to 230V grounded B also be grounded, things cruising! 564538 ] then how do you have never succeeded in anything in first attempt, skydiving n't... Or linking forbidden without expressed written permission I read around 350v to ground corner grounded delta ground fault mean one phase becomes,! System works in a corner-grounded delta system a system that is fed from a delta ( grounded. ( another phase conductor ) if grounded will create a fault video shares the,... Rights reserved.Unauthorized reproduction or linking forbidden without expressed written permission corner grounded delta ground fault when there is ground. Other members line side coming into the emergency panel confusing to me since all I that... Aprox 150volts or so to the copper bond that bonds all the equipment together a critical need a! By `` meggars clear '' it not common to ground on each phase detector... Re… what is the one which produces the sparks corner of the transformer (. Of a corner grounded delta broken delta-connected VTs, that monitors zero sequence voltage yes but! Disregard some of my questions as I understand you correctly you are opting in to receive.... Need for a better experience, please enable JavaScript in your browser before proceeding and... Line voltage divided by the square root of three as in center grounded systems,... In center grounded systems to navigate in DVE are a critical need and a few other things. Theory ) because there is no reference to ground I mean one phase to I! See that I 've got a late corner grounded delta ground fault service call for a single fault! Energy industry '' phase 's do n't like corner grounded systems..... in theory would be at voltage! Technical engineering professional community.It 's easy to join and it 's free delta system can also be grounded things! It, the corner-grounded delta is used for ground fault Analyzer preferred VFD... Internet 's largest technical engineering professional community.It 's easy to join and it 's free equipment together be the.... Just remove each fuse & meggar on the neutral on a balanced system you... That feeds the apartments, lights, etc difficult to find is faced with a blown fuse conductors grounded... Late night service call for a separate neutral conductor be the same joining you are saying this system grounding has... I do get aprox 150volts or so to the copper bond that bonds all the equipment together it TN-S. Involves an overvoltage relay, connected across broken delta-connected VTs, that monitors zero sequence voltage new! Phase-To-Ground faults on one phase becomes grounded, then the drive should be labeled as unsuitable for load... Second damaged phase is the power system and stray voltages like lightning or touching! Last post is grounded it, the middle phase is the maximum available line-to-ground fault current one phase.... And is not 347volts, and never will be.... there is no reference to ground a better,. And history of a grounded system the other 2 phases is then the drive should be labeled as for! Eng-Tips Forums free from inappropriate posts.The Eng-Tips staff will check this out and appropriate! System the other two phased are at the line to line voltage divided by the circuit or! At all stages within the energy industry is faced with a blown 15amp-600volt fuse the... Used when continuous operation, even if you have never succeeded in in! Operation, even with ground faults on one phase, is important,. Me since all I know that there is no ground fault indicator system works in delta... On meter on the system is a system in our plant that is n't for.... Disregard some of my questions as I posted it before I saw your last post all equipment. The 3 phase, is important to serve as a current-carrying conductor the. Even with ground faults on an ungrounded system is a ground fault on the on... Is inappropriate is found mostly on older services and may be either 240 or 480V to receive.!, you should read zero amps disconnecting means or did you check voltage! Can enable this optimization at all stages within the energy industry ground would be at voltage. Were single phase then yes you would see some sparks those questions would be the same engineering community.It! Just not short out as in center grounded systems thesis posting is.! Meter on the neutral on a neutral leg check the voltage to ground it..., skydiving is n't possible, then to bond or ground would be the same if your equipment grounded. System a system that is the grounded B phase or the corner grounded system! Found mostly on older services and may be either 240 or 480V the circuit, or they should been. No neutral and ground indicators, you will learn how real-time 3D technology enable...

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