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A three phase Delta circuit (3 wire) is a SERIES circuit (one path for current to flow). You can have one neutral in a series circuit. It is not a fault to only have one neutral. It just creates a path to ground. Putting two neutrals in a delta circuit would cause a dead short. One neutral can be used to create different voltages for a customer (center tapping one transformer can = Lighter Pot) or you can use the neutral as a corner ground. A corner ground provides safety to a delta 3 wire bank and it can prevent a customer from stealing power due to a meter only measures two legs of a delta because it once again is a series circuit. Corner grounding will also make sure a fuse might blow if one of the other phases accidentally becomes grounded but always be aware a Delta is not dead unless all 3 phases are de-energized.

​@jasonleary6717 I need a video explaining this, I'm hands on so I don't fully understand in my world a hot to ground or neutral will short

@mkidd8806 Thank you for the support and feedback. These are some early videos we were experimenting with. The audio was terrible but if all goes well, I hope to have a new video or two by the end of the month. I had all kinds of request for a floating neutral video and a transformer polarity video.

@jasonleary6717 thanks for the reply. Anything dealing with transforms on the utilitie poles and inside buildings. Also bonding, grounding, neutrals. Anything concerning the use of wye and delta service etc. I will soon check out your video on corner ground delta. Am 72 and my early career there was true 2 phase and if memory is fair may Pennsylvania has a couple of areas. Good luck from Waco Tx

Thank you for the question. A Ground and a neutral have different functions in a electrical circuit but in a 4 wire corner grounded Delta, the neutral is acting as a safety or to prevent the stealing of power. (120 volts) If a 3 wire delta is corner grounded then you can't have a phase get accidental GROUNDED and no one not know there is a phase to ground potential in the circuit. Always remember, a DELTA circuit is a series circuit (one path for current to flow) a neutral can show up and know know there is a potential to ground, if you ground a 3 wire delta now you have protection from accidental grounding. Here is a great you tube channel for all thing electrical. ruclips.net/video/JBpQ9Fodz_Q/видео.htmlsi=TzDHvtDCX1sRkBXN

Thank you for the question. A Delta circuit can be a 3 wire circuit with no ground or a 4 wire circuit with a corner ground or the neutral can be used to get different voltages for the customer. ONLY ONE NEUTRAL CAN BE USED IN A DELTA CIRCUIT. If the circuit is a 3 wire DELTA then no phase to ground voltage is present, because you have no neutral. The danger with this 3 wire circuit is a neutral could show up accidentally and the DELTA circuit will not show any signs of a problem other than having a phase to ground potential there and no one aware of it. If you chose to ground a 3 wire circuit, then you have a 4 wire CORNER GROUNDED DELTA. Now one phase has a ground potential in the circuit. If there is a problem or a fault in the other two phases now you will blow a fuse and know you have problem because TWO neutrals will be in your DELTA circuit causing a dead short. Just remember a Corner grounded delta is used for two purposes. (1), To prevent the stealing of power by a customer (120) volts. (2) to prevent a 3 wire delta from accidentally being grounded and creating a phase to ground voltage without the customer knowing they have a problem with accidental grounding that could cause a accident for workers working on the equipment.

In this example, we have a Wye-Wye 120/208 3 Phase bank. We are lifting the neutral connection from H2 on the transformers to show what happens to the phase to ground voltage on the transformer bank. Notice there is hardly any change in voltage from phase to phase. Always take 6 readings when troubleshooting 3 phase power. The neutral in a 4 wire Wye stabilizes the connection and is a current carrying conductor. A 4 wire Wye system gives you TWO differences of potential. A Phase to ground and a phase to phase voltage. You could have a 3 wire Wye system but every phase would have to be perfectly balanced so a neutral would not be needed to carry the unbalanced load between the phases. A 3 wire Wye would not give you a phase to ground potential though. The 4th wire in a WYE makes sure the Phases has a return path to balance the circuit. The neutral will carry the unbalanced load between the phases. The neutral on the high side is coming of the H2 bushings and the ground on the model is the wire below the transformer cans. When the neutral is lifted or disconnected you lose the 120 degree displacement in the bank from phase to ground. This is why the voltages spike when checking the phase to ground connection. Always remember the ground balances a 4 wire Wye circuit and is a current carrying conductor. If disconnected, loose or just a bad connection, the neutral can have the primary voltage looking for ground and if you become the ground you will get hit by the voltage from phase to ground.

@@jasonleary6717 Yes, Kirchhoff’s voltage law for series circuits (open or lose Neutral conductor). Thank you

@@jasonleary6717 Is the Neutral coming off of the H2 bushing grounded to the can ONLY and not going in parallel on another conductor back to the substation? thank you. P.S. Meaning Mulit Point Grounding system at EACH POLE that has a transformer.

@@tedlahm5740 In this scenario it is a isolated transformer bank showing the dangers of a broken neutral at the transformer bank. Our goal is to show a open neutral coming off the H2 terminals or a bad connection. Troubleshooting with the meter shows the problem by checking voltages.

Hey man, I’m trying to learn the complete process for paralleling 2 480v 3 wire delta delta closed banks. Do you know how to do that? Can you teach me if you do? This video was a little helpful but I’m still not completely certain on how to do it.

Thank you for the compliment. A Delta circuit is a Series circuit (one path for current to flow). You can ONLY put ONE neutral in a delta circuit. You can use the neutral as a corner ground or use the neutral to center tap a can for different voltages but you can only do one or another at a time. You can't center tap with a neutral and corner ground at the same time. It would be to many neutrals in a delta circuit at the same time causing a short in the circuit.

@@jasonleary6717 hey thanks for the response, so i got it. so the corner ground acts as a neutral to carry the load unbalance¿? the reason i ask os because i installed a buck amd boost on that corner delta for a three phase stove, and i read in the buckboost that if the load is unbalanced it needs to be tied to a 4 wire system, but i am not sure what is the asumption. their specs are very poor, just a label.

@@celsiusfahrenheit1176 I have never used a buck-boost transformer but I'm guessing that it is a transformer that makes changes to a fixed voltage. As a lineman we have pole mounted transformer with tap changers that do the same thing by adjusting the primary coil's turns ratio to match high or low voltage on a distribution circuit. If you have a 3 wire delta bank, you would have just one voltage to chose from between any two phases; however, when you corner ground a phase you do stabilize the ungrounded phases. An example would be having a 240v 3 wire delta. There would be no phase to ground voltage except for phantom or ghost voltage which can be corrected by using a meter with a LoZ setting on it. We have a phantom or ghost voltage video on a 3 wire delta on here as well. So, lets say you corner ground B phase on a delta circuit. Now your voltages change in the circuit. B to neutral will read zero but A and C phase to neutral will read 240 volts. It stabilizes the other two phases not grounded. I'm guessing like you mentioned the neutral on that type of transformer is needed for the unbalanced load to have a completed circuit to stabilize the ungrounded phases but that is just my best guess on this situation.

@@jasonleary6717 nobody really knows, i wil talk to the engineer from the poco. i never saw a three phase stove before, i told the custumers in writting when they asked me, that their service was a 3 phase corner delta no neutral 240v they still got a 3 phase 208v no neutral required. anyways thanks for your replays.

Mark, that is a very good question. We have used various high voltage applications as well as different kva transformer ratings. But we the secondary voltages have always been 120/240-volts this is due to the harmonic build up between the primary and secondary coils that cause these voltages. Keep in mind they can drop 10-20% based on our studies. We need to try this with a 240/480-volt secondary and see if the results are the same. Again great question Mark.

​​@@threephaseinnovations7546ave you ever ran across a 240/480V 4 wire delta? I've heard of them but never came across one since they are extremely uncommon. I've seen 120V/240V 4 wire open deltas in rural settings where a farmer needs some 3 phase power for motor loads, but the majority of the loads are 120/240 single phase.

Hello Funk master flex. Thank you for taking the time to check out our videos. Any single phase, open bank or three phase bank can be paralleled together. The main reason is to make sure your customer is never out of power. You could also wreck one bank out and the customer would never lose power while the other bank back-feeds the customer until the new bank is installed. There are still many delta distribution systems on the power grid where all banks are tied together. Detroit, Michigan would be a good example of this. You can also tie single phase pots together. Example would be taking two 120/240 cans and hoking the coils in each can in series and then building a 480V service if needed. Each single phase can would have to be on the same phase though.

Hello Bryan, Corner Grounded deltas or 3 wire delta banks can be tricky. One of the phases should be labeled or have some kind of identification to let you know what phase is grounded. If it is a corner ground, the other two phase not grounded should be stable to ground. An example would be having the B phase grounded. It should read 10 volts or less on a meter (B Phase to ground) but if you have a meter with Low "Z" setting you should get a more accurate reading. Phase A and Phase C would still read 480V to ground if it is a corner ground. If it's a 3 wire delta and have have readings like you mentioned then whole new troubleshooting problems occur. You may have a piece of equipment or a ground come into the circuit and now you have to find it. When a 3 wire Delta gets an accidental ground, volt meter reading can become very strange depending on the resistance to ground or the type of meter you are using. The Corner ground Delta bank was created to prevent some real troubleshooting problems for 3 wire delta banks and for safety. Just one ground can exist in a Delta bank and not affect the bank at all. I doubt this helped you much with your situation, but you might want to see if your plant has any old electrical prints, warning lights or maybe check out the transformer bank outside on the pole feeding into the building. Sometimes a corner ground Delta is much easier to spot on the transformer pole itself to see if a phase is grounded. good luck.

This was helpful. So it sounds more likely that we have a 3 wire delta, thus the goofy voltages. I’ll be digging into this a bit more now to verify. Thank you for your quick response and expertise.

@@jasonleary6717 hello. i like your explanation and video demonstration. i have an ungrounded 3 phase 3 wire delta going to a customer's 3ph 480v motor. he has no electrical issues to speak of but i wonder if he's aware that one of the phases is grounded at the meter. there is no identification on the grounded conductor; however, at the meter socket is a bonding jumper on the middle phase wiring lug with a manufacturer's tag that clearly states: 'When service is not grounded, remove bonding strap..." i think that's dangerous to ground a phase at the meter because what happens if the equipment (in this case the meter enclosure) ground comes loose? so where is the proper place to ground a phase if not at the meter?

@@betta3301 Thank you for taking the time to check out the video. I really can't give you a great answer to your question; however, when it comes to grounding any electrical circuit, the NEC Code book is very detailed to say the least. I suspect that Local or state codes might also have something to do how the circuit is grounded. I also suspect the circuit might be grounded only in one location so the circuit could easily be underground if need be at certain times for whatever reason. The main thing to remember when dealing with any DELTA circuit is always be aware of back-feed and ONE neutral can be in the circuit making it a 4 wire DELTA. Corner grounded or center tapped to obtain different voltages (120/240 etc..) Electricians have always said troubleshooting a DELTA, which is just a series circuit can be tricky. Section 250.1 helps you overcome a common problem that leads to misapplication of Article 250. Most folks are so overwhelmed by Article 250 that they immediately get lost when confronted with it. However, it’s divided into 6 logical groupings of information and Section 250.1 of the NEC codebook tells you what those are. Good Luck and stay safe. :)

Corner grounded delta's can be tricky. I'm glad I'm on the Lineman side of the bank. So much troubleshooting on the electrician's side. :)

Hello Mr. Rodriguez. Thank You for taking the time to check it out. We really appreciate it.

i'm seeing the same thing at a similar location. if i may ask, where are you seeing the conductor being grounded?

@@betta3301 not sure I understand your question. I was reading the ~11v after the transformer

@@pumarodriguez3964 you stated you have a grounded phase conductor and i was just wondering where you see the phase being grounded at, if possible. if its inside a pad mount transformer then its not obvious as compared to up at the pole. or maybe its grounded somewhere else?

Hello Mr. Thompson, sorry for the late reply but I was able to find a little bit of information to your questions. Hope this helps. QUESTION 1: Important requirements for the grounded conductor of grounded electrical systems or services are found in Article 200, which deals with identification of grounded conductors and their terminals. The grounded conductor is required to be an identified conductor of the system or service. Sizes 6 AWG and smaller generally are required to be identified by white or natural gray insulation for its entire length. Sizes larger than 6 AWG are permitted to be identified by white or natural gray insulation; by three white or natural gray stripes along the entire length of the conductor’s insulation, on other than green insulation; or at their points of termination by distinctive white markings that encircle the conductor, such as colored tape or painting. This identification is required for both grounded conductors and corner-grounded delta systems. QUESTION 2: This section contains a list of standards that are applicable to corner-grounded delta systems. These standards address three basic points: 1. Any two-pole circuit breaker intended for use on corner-grounded delta systems shall be tested and rated for such use. 2. No overcurrent device is permitted to be used to disconnect the grounded conductor, unless this device simultaneously disconnects all conductors of the circuit, including the ground. 3. If the system is a corner-grounded delta system and fuses will be used for motor overload protection, a fuse must be installed in the grounded conductor, but only at the motor controller.

@@jasonleary6717 Thanks that helps narrow it down somewhat. Lyndell

Thank you for the compliment moe molar. I don't have much field experience with this bank myself but you are correct. Everyone says they are tricky for sure.

It can but, not recommend. Laminated thin sheet allows for more surface area for the current to circulate, therefore reducing eddy currents that can create unwanted heat.

Very good question koontreeguy. The only info I have read about losing the ground is a relay should set off an alarm or warning that the ground phase has been lost. Most engineering companies stop with their info right there and don't explain the effects of the bank losing the neutral under load. Schneider Electric only explains the advantages and disadvantages of this old type of system (I copied them below). Sorry about not be able to give you a definite answer to your question. Corner-grounded delta systems:•Stabilize voltages of the un-grounded phases to ground.•Reduce the generation of transient over-voltages.•Provide a method for protecting electrical distribution systems when used in combination with equipment grounding. Due to its disadvantages, the corner-grounded delta system has little reason for modern day use:•The system is unable to supply dual-voltage service for lighting and power loads.•It requires a positive identification of the grounded phase throughout the system.•A higher line-to-ground voltage exists on two phases than in a neutral-grounded system.•Most electrical distribution equipment manufactured in North America is not rated for use on this system.•Fault switching (opening) is much more severe for the clearing device, and ratings may be greatly reduced.

Hello Adam. Thanks for watching the video. Electromagnetic Induction is the whole reason a transformer is able to not "short out" when grounding ONE side of a transformer's coil. Faraday's and Lenz's Law describe a transformers ability to create a CEMF force that opposes the applied voltage. This keeps a delta or wye circuit in balance. A Delta circuit is tying the transformer coils in series. You can always put ONE neutral in a Delta circuit and you will not destroy a transformers ability to create the CEMF force. Two neutrals in the Delta circuit will create a "dead short" across the transformer coil. If you destroy the transformer's ability to produce a CEMF, Ferroresonance will occur. Another crazy phenomenon dealing with electricity. ruclips.net/video/k2RzSs4_Ur0/видео.html Video about Lenz's law ruclips.net/video/U7dNdQc1NL4/видео.html Ferroresonance CEMF

Thanks Jason, they were very helpful!

@@jasonleary6717 hope you can answer but how could we get around this when we connect our 3phase solar inverter on such systems. Will isolation transformers work?

Thank you for the comment Mr. Klopfer. We hope to have a floating neutral video done in the near future as well.

Hello Marc, Yes, they are a miniature version but everything is made out of 6061 standard aluminum, porcelain bushings and the can is even anodized for safety precautions. The pole mounted transformers can be made anyway the customer chooses. We even make them with single bushing high side and polished as well. The secondary voltage ranges from 120/240V to 277V depending on the customers preferences. All of our equipment can be checked out on our website and thank for checking out our videos. Threephaseinnovations.com.

Thank you for the compliment Echo.Whiskey.

Thank you for the comment jvck blvck. I can only imagine what goes on in those oil fields. I bet you guys deal with "Phantom or Ghost" voltage in all those straight 240V or 480V DELTA banks all the time. Especially tying them together. Thank goodness meters have a "LoZ" setting now. Stay safe.

@@jasonleary6717 Its bad. We have to really pay attention and watch the younger guys, teach them not to just go through the motions because even though the next bank looks the same, its not. Oh yeah LOZ is a life saver. You should see what the phase angles look like for the pump jacks. Current and voltage are never in unity and PF jumps from .51 to .16 lol you be safe also brother

Hello Mr. Padilla, Thank you for the comment and sorry it took awhile to get back to you. If you are referring to a "Floating Neutral" it has several considerations. A WYE-WYE bank must always be tied to ground to stabilize the bank. When you have a DELTA secondary and a WYE primary some utilities will want the Primary neutral not grounded on the WYE high side. One reason is when ground fault happens on the distribution system or at the transformer bank itself the ground fault will not go through the transformer bank or the fault won't go back out on the system. In short, it isolates the transformer bank from the system and the system from the transformer bank so fault current will find a different path. If the transformer bank has a fault, it does not go back on the system and might create damage to other equipment on the system. If the system has a fault, it won't ground out through a customer's transformer bank and go somewhere else to ground out. Second reason: When you lose a phase on a closed bank and the neutral is floated the customer will realize they have a problem and will call the utility to let them know something is wrong. If the bank is not floated on the WYE side and the bank is grounded, the closed bank will turn into a "OPEN" bank when a phase is lost. Two transformers in the Delta secondary are trying to carry the original 3 Phase load and if they KVA has not been rated for this type of situation, the customer may not know they have a problem until the other two transformer burn up trying to carry a load designed for three transformers. Example: 3 transformers each with a 100 KVA. Closed bank total KVA is 300 KVA (3 X100). If you lose a phase with the WYE grounded, the bank is now "OPEN" 2 transformer are now trying to carry a 300 KVA load. They won't be able to do it. Their capacity is has been reduced to 173.2 KVA. There are two different ways to do the calculation. 300 KVA x 57.7% = 173 KVA or you lose a phase and are left with 200 KVA x 86.6%= 173 KVA. 2 transformers will try but can't produce the same load all 3 were working together. They will burn up if the phase is not put back in over time based on the load and all other factors. Ambient temp for example. One thing to remember. If you are going to "FLOAT" the neutral. You must connect it to energize the bank. Then you can float it. When you de-energize the bank, put the neural connection back on, then you can open the bank. You will have high voltages on the neutral itself until you make the ground connection. Ferroresonance can also occur and can be dangerous. Whole topic explained very well be Dennis Merchant. ruclips.net/video/U7dNdQc1NL4/видео.html

@@jasonleary6717 Lovely. I am very happy in your answer. It Enlightens me more. That's why when we do V-phase banking, we connect the one lead to the neutral (usually the center one). Our seniors never explain that way. Thanks jason.

@@cristobalpadilla4117 Glad I could help. When we get some time I hope to make a video about a floating neutral sometime soon.

Great question, if you are a member of our (lineman transformer discussion page) on Facebook, would you please repost this question their. We have some very smart guys on their. Also this would be a great quest for other members to hear about and discuss. Thanks for the questions.

LUIS LOREDO imagine the one ground center tapped. If a ground is added on either side of the transformer that has been grounded it will result in a ground fault short on that phase.

Thank you for the comment Mr. Dove. Our buddy who is in charge of the video production is looking into buying a microphone. That building we are in is terrible for sound. DOHH!

We might come up with a video describing the current flow or angular displacement between the primary and secondary coils in a transformer. I will get with our crew and see what we can come up with in the future. Thank you for your reply Mr. Barajas