Listed means one follow the instructions. 67 times 34. Also, you can save. , What is the minimum-size aluminum or copper-clad aluminum. A review is given of 480 V corner-grounded delta service for oil fields. 5 . The purpose of bonding c. Basic cheap plug-in breakers are “slash” rated, meaning 240/120V; they are rated 240V phase to phase, but 120V phase to ground. Claim this business (250) 884-1942. Then any corner of the delta arrangement is grounded (the B-corner-ground is customary) to create a neutral in the winding (labeled and colored usually gray and white as a neutral). The transformer has multiple taps . Because of the disadvantages of not grounding systems, electrical designers had to integrate a ground reference to existing configurations. Besoeker3 Senior Member. The service company sent us a Magnum Power Genset (by Generac). Jan 26, 2017. Apparently, code requires this conductor to be phased white or gray but many People outside of code apply alternate color tape to the conductor because this. 85 of the 2002 NEC was changed to read: 240. Sounds to me like it’s a corner grounded delta with no 120V tap. It kind of freaks me out measuring 0 volts to ground on a open buss 4-5 thousand amps switchgear in the powerplant. 362K subscribers in the electricians community. One line conductor is grounded (conventionally it is BØ). optional based on the design of the electrical engineer. J. Proper grounding reduces overvoltages, improves uptime, and isolates faults. Google a pic for corner grounded delta transformer. corner grounded Delta system. 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. The 277 volt is interesting but, not relevant. Pole pigs are 2 winding transformers with each winding isolated from one another. And, without proper identification of the. So instead of 480VAC 3 phase being 277V to ground, it was also 480V to ground thus being a bigger risk if accidentally grounded during troubleshooting. Some have argued that, because Rule 097B2 does not specifically mention the multi-grounded phase of a corner-grounded delta circuit, the multi-grounded phase cannot be A corner-grounded Delta system is a system in which the transformer secondary is grounded and one corner of the delta is solidly grounded. This system has multiple transformers that go from 480-208 delta-delta and also 480v delta-208/120v wye. The size of the step-down transformer is. Normally the grounded conductor is A or B phase- but you never. SPDs must be listed [Sec. A two-pole circuit breaker applied on a 3-phase, corner-grounded delta system must be marked 1Φ-3Φ. , a zero sequence voltage). Delta wye transformer wiring arrangementDelta wiring diagram 4 wire 240 volt wiring diagramDelta phase system wiring wire three grounded corner. Delta grounded 240vSchematic diagram of (a) grounded and (b) ungrounded pv systems Grounded b phase wiring diagramPhase wire delta single grounded 480v transformer corner 480 ground system volt three 208 volts leg efficent than service open. MRG, Article 200. iceworm Curmudgeon still using printed IEEE Color Books. BRB for 120/240, 120/208, 120 delta corner grounded (rare but have seen it), or 240 delta corner grounded, with grounded white or marked white, whether it be grounded corner phase, center tap ,or wye. By "fail", it would have to mean a GROUND FAULT. True. gap, is maximum. A 480 volt corner ground delta does not have any portion of the supply that operates below 277 volts to ground (aside from the grounded conductor itself) - you can not connect any load in a way that gives you less then 277 volts between conductors or ground on this sytem - a 277/480 rated breaker can not be used on this system. "A" or "B" phase short and the the OCP operates. I've seen corner-grounded systems where one phase is tied to earth. 240V. The solidly-grounded wye secondary is the modern way to go for 600V. D1-D4 lumen packages only. 2. Currently, the secondary of the transformer enters our switchgear which has a disconnect for each of the 2 sides of the switchgear. I can see 1 phase of the secondary is grounded to the common primary neutral. If all are zero to gnd, then probably a floating delta. Aside from serving the step-down transformer, the 480V side is mostly going unused. Solidly-Grounded wye or star configuration : Yes: High resistance grounded wye or star configuration : No: Ungrounded wye or star configuration : Asymmetrical: Grounded at the corner of the delta connection : Grounded at the middle of the side : Single-phase, grounded at the end point : Three-phase variable transformer without. On the utility side, the transformer can either be. Sparkle. No 120/240VAC circuit breakers may be used on any corner grounded delta system. The NEC® addresses slash voltage ratings for circuit breakers in 240. If a solidly grounded neutral conductor is also being brought to the MCC, the power system is a 4-wire. Joined Jan 25, 2011. R. (2) A circuit breaker with a slash rating, such as 120/240 V or 480Y/277 V, shall only be installed in a circuit where the nominal voltage of any conductor to ground does. The system has accidentally become a corner-grounded delta system with little, if any, current flow. 120 V, 3-phase, corner-grounded delta. The inverters may not like the elevated voltages to ground. I have multiple 240v single phase loads and (1) 240v 3 phase load. C orner-grounded delta grids are not supported at these voltages. zbang Senior Member. A corner grounded delta system will put more stress on the insulation between windings and ground. Corner grounded delta securely references the other two phases to earth potential. This supply system configuration is often used where high power is required, for example for large mo-tors. If grounded, then a ground fault protector may be desirable although not required. It is very dangerous to touch the grounded line in a corner-grounded delta when the line. Mr. Ground B phase systems, grounded phase services, and end-grounded delta systems are all examples of corner-grounded delta systems. Glenwood landings for lipa has one. As the project is presently designed, we are stepping this down to 208/120Y and serving all of the building's loads via the 208/120V distribution system. Another disadvantage, as given on page 33 of IEEE Std 142. Every fuse and circuit breaker is assigned an interrupting rating. When people pass the grounded phase through a disconnect, one of the solutions is to put in a dummy fuse link that would look very similar to this. On a 240V 3 phase grounded delta system, the voltage to ground is 240V from 2 of the poles. But guess what, any line to ground fault will be 480v. The cost of running a neutral to the service disconnect seems like a cheap way to save expensive headaches. Z. Wye-wyes are extremely rare in <600V systems. Question, when connecting a Wye generator to the Corner Grounded Delta, will. We are doing this to avoid required ground fault protection in the breakers. 'power' panels (e. Compared with the solidly-grounded wye system of Figure 1 this system grounding arrangement has a number of disadvantages. The grounding resistance required can be determined from these values of current and voltage. 6. Japanese electricity is a dumpster fire since they have both 50 and 60 hz, depending on the island (and whether it was under German or US influence in ~1900), AND they use 100V since it is nominally. Red leg 240 delta four wire was also a standard system and if that was floating (or maybe even grounded at the pole) you would get 120, 120, 183, *or* 0, 240, 240 if A was faulted without being noticed. g. grounded TN systems (TN-S systems) 1 Corner-grounded and midpoint-grounded delta systems 2 (< 600 V) IT systems (ungrounded or high-resistance-grounded [>30 ohms]) 3 R10, R11 Do not remove EMC AC or VAR. One-line diagram symbol for a start push button _____ and a stop push button _____ Step-by-step solution. Author's Comment: Other systems such as a corner-grounded delta system are permitted to be grounded, see Section 250-26(4). For that reason, 99% of people who HAD legacy ungrounded delta systems. 100 % (3 ratings) for this solution. Trying to determine if I have a ground fault somewhere or a bad leg or breaker. It then goes on to discuss performing an open corner test to ensure proper polarity when c. Phase readings as follows: A to…By grounding a corner of the delta, you help stabilize the phase to ground voltages and the phase to phase voltages will also be stable. 73) - Upon ground fault, the faulted phase L-G reading is zero and the other two. UL Listed for use on 240 V Corner-grounded Delta Systems (Grounded B Phase). A two-pole circuit breaker shall not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1Φ–3Φ (see figure 13). I asked them to take voltage readings between phase-phase and phase-ground just to make sure it is an un-grounded delta secondary. 102(C)(1) for sizing the grounded conductor. Section 250. Open delta, also known as corner-grounded or ungrounded delta, is an electrical configuration of a 3-phase system that provides individual phase to ground connections without a single selected neutral point. LocationStudy with Quizlet and memorize flashcards containing terms like The practical safeguarding of persons and property from hazards arising from the use of electricity best describes which of the following? Select one: a. Scanning through 250. the breakers in the panel are. T. The NEC® addresses slash voltage ratings for circuit breakers in 240. 240 V, 3-phase, 3 W, ungrounded or corner grounded delta V. 12. 24(D)(4) This section covers impedance grounded services. three-phase, 3-wire, corner-grounded delta system? 120V 240V 277V 480V Correct Answer: 480V. The voltages are 480 volts between phases, 480 volts between phase a and ground, 480 volts between phase c and ground and 0 volts between phase b and ground. If that isn't possible, then the drive should be labeled as unsuitable for the floating delta and/or corner grounded delta. In a corner grounded delta system, one of the three phase legs is intentionally grounded. 1 of 2 Go to page. Class R fuses are rated for 100 kA, however without the rejection fuse clips - system is limited to 10 kA since Class H or K fused could be installed in the future. Reply. Grounding B phase is standard when working with older. In the setup the OP describes, the maximum voltage to ground would be 240, so he must use a straight 240 V breaker. IESNA. 4. Corner ground Delta, A higher line to ground voltage exists on the other two phase in a neutral - grounded system along with fault switching (opening) is much more severe for cleaning devices and ratings may be greatly reduced, and stabilizing voltages of the ungrounded phases to ground . 36 Overcurrent Protection > (C) Delta Breakers. D325NT, D325NTR, D326NT, D326NTR, T327N and T327NR accept only 300Vac Class T fuses. So all of the breakers you. to ground on a 480 volt corner grounded delta system. 240V. The maximum continuous operating voltage is measured from phase to ground for solidly grounded systems. ) Branch-circuit fuses do not have to be marked with their ampere rating. 85 permits one pole of a motor controller to be placed in a permanently grounded conductor provided the controller is designed for all conductors. grounded TN-S systems (center-grounded wye) Corner-grounded delta and midpoint-grounded delta systems IT systems (ungrounded or high-resistance grounded) TT systems 1) 2) 1) A residual current device must be installed in the supply system. It is a Delta and Split-phase hybrid. Recently and in the past there have been numerous posts/questions re: corner ground delta systems and the responses have been quite varied. A phase 490-ground B phase 490-ground C phase 0. Also explains your 480v to ground readings. Jun 10, 2019 #5 B phase on the Delta system is grounded. 120/240 V, single-phase, 3 W, solidly grounded III. teal854t Discussion starter · Oct 13, 2010. There is absolutely zero reason to design B phase cornered system if you designing a new system. Now that I’ve wrote all this, if it’s truly an ungrounded system there should be ground fault monitoring somewhere to alarm of such ground fault. Informational Note: An example of a system permitted to be grounded is a corner-grounded delta transformer connection. 20. CryptoDelta has no obvious grounding location; the AC lines are generally all floating relative to earth. You must also bond the phase to the case with a jumper sized to 250. Introduction Corner-grounded delta systems are not re commended for new installations. #1. Corner grounded delta. Could be the outlet is miswired or mis-breakered and has two of one line and one of a second. Occasionally you may have an application that is a delta voltage source with a grounded “B” phase, also known as corner grounded. ) 480 3ø, 3W Wye connected Impedance grounded system. Frame size EMC filter (+E200) screw Ground-to-phase varistor screw R10,. 208, 240 and 480 are all common 3 phase systems. In case of a power failure, when the generator motor reaches the correct speed, a set of ___ is energized to disconnect the load from its normal source and to connect it to the generator output. ago. They are available. 208 Y/120 V, 3-phase, 4 W, solidly grounded IV. Therefore, many historic structures still have operating delta-delta service transformers where one corner of the transformer has been grounded to provide 120 V/240 V power within the facility. Introduction Corner-grounded delta systems are not re commended for new installations. If it is a corner grounded delta, the grounded phase must be* grounded AT the transformer terminal, meaning you will be able to SEE the ground. Where a delta-fed system must be grounded for detection of stray current to ground or protection from surge voltages, a grounding transformer (usually a zigzag transformer) may be connected to allow ground fault currents to return from any phase to ground. 22, 2005 nec. Furthermore, 3-phase, corner-grounded, delta circuits can only use two-pole circuit. Could be as jraef mentioned. 2 pole fusible disconnects and 120/240V panels are sometimes rated for 240V three phase. A circuit breaker with a special “straight” rating of 277/480 volts may be used on a corner-grounded delta system. 22, 2005 nec. 277V. This is a non sequitur. So on A phase to ground you have straight 480V. SSDriver said: I have a job that is 240v open Delta with B phase grounded . I came across a code a while back about NEC not allowing circuits to. B to Earth = 0, C to Earth = 524Delta, open or ungrounded 230 (or 460) volt A to B 230 (460) B to C 230 (460) A to C 230 (460) Any phase to ground will read random values. These connections do. A building needs to be taken off it's primary feed, so we can service it's 4. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. Corner grounded delta systems are common in old industrial facilities around St. In a Delta system, you must either have one corner grounded, or you must have ground current monitoring if it is an ungrounded Delta system. Feb 3, 2009. Wye connections, ungrounded delta connections, and corner-grounded delta (“ghost”) leg configuration connections are all examples of three-phase supply. Corner-grounded delta: One line conductor is grounded directly. The three phase two wire corner grounded delta is the same as typical delta configuration and rarely used in the recent systems. For services they used to hook the 600 volt and under seondaries anyway you wanted. Areas of concern converting a corner ground to a wye include: In a properly installed corner grounded system, the corner conductor should be white or gray. Jul 20, 2023Other system configurations, such as 3-wire corner-grounded delta system, ungrounded system, or high resistance grounding system are permitted by the National Electrical Code, but they are rarely installed, except in industrial applications. 240. In a Delta system, you must either have one corner grounded, or you must have ground current monitoring if it is an ungrounded Delta system. #3. #4 · Oct 2, 2020. My proposed fix is: 1). ”The VFD that I have now is an older model Woods E-trac X2C-40150 and the manual does not say anything about corner grounded delta. Nema motor voltages so 460*1. The corner-grounded Delta system has an obvious economy in wiring costs, and the grounded phase can be used to physically protect the other two phases from accidental grounding. We would like to show you a description here but the site won’t allow us. This supply system configuration is often used where high powers are required, for example for large motors. However, some utilities still provide this system, and many old installations still exist. Although delta. NEC 240. Corner grounded delta. & below. It is quite common as a separately derived system for 230 volt equipment in a plant with a 480 volt service. 67A; secondary current will be 1. It has (in this instance) 480v relative to the two other phases, and is 1/3 of the 3 phase circuit. 3, July 2022 -Corner-grounded delta grids not supported at voltages of 400V / 480V Version 1. A second fault, on a different phase, however, presents a problem. 2) Adding a grounding autotransformer. Other types of three-phase supplies are wye connections, ungrounded delta connections, or corner-grounded delta ("ghost" leg configuration) connections. In another thread about imbalanced voltages and currents the POCO decided to change a corner grounded delta well service to a delta with high leg. . PowerPacT B-Frame 15/20 A Thermal-Magnetic Trip. ® (UL®) Listed products for this application. . It requires connecting the impedance grounding conductor according to sections 250. • Ground fault sensing is undefined for the grounded phase, so typically cannot be used at locations where GF is required, such as healthcare facilities Figure 2. High Leg Delta Transformer Connectionmight occur when Phase A goes to ground on a 480V, B-phase, corner grounded delta system. The primary goal for a solidly grounded system is to open the circuit as quickly as possible to limit damage and risk to life. 480V. -John. The 277 to ground seems weird. Be careful when installing slash-rated breakers on a solidly grounded high-leg delta system. 6. On 600 V, 200 A switches, 100,000 A max. If such systems are grounded, they shall comply with the applicable provisions of this article. PowerPacT B-Frame Let-Through Energy Curve. Ground Fault Circuit InterruptersUL Listed 5000 A short circuit current rating for corner grounded Delta systems. System grounding is the connection to the ground – solidly or through impedance – of current-carrying conductors – e. might occur when Phase A goes to ground on a 480V, B-phase, corner grounded delta system. test Learn with flashcards, games, and more — for free. On a 480 v corner grounded to transformer 120/208 Y is the grounded leg of 480 v delta always bonded to the frame of the transformer. Installations with this system require a 480-120V transformer to supply 120V lighting. There is no way of grounding a 480V system (or any over 260V L-L) to meet the 150V L-G standard. 1KV breaker at nearby sub. 36 (C) Equipment for General Use, Delta Breakers. 120 V, 3-phase, corner-grounded delta. Another variation is a "corner grounded" delta system, which is a closed delta that is. Another disadvantage, as given on page 33 of IEEE. The only solution i have come up with is pulling the pump, and changing them to 277/480 wye,. ALL 3 PHASE. You can run a typical two-wire line-to-line load off just a single pole breaker because on this. 'power' panels (e. I partially agree. Such faults are typically high impedance and at unspecified locations. 2, the transformation ratio is 4160 divided by 120, or 34. Exactly what one would use for 13. 5. This type of grounded system is 3-phase, delta-connected and is called a corner-grounded system, because one corner of the delta is grounded (figure 1). Circuit Breakers for Grounded B-Phase (BØ) (Corner-Grounded Delta) Systems. NEC 240. 240. Also, with the same KVA and impedance transformers, the available fault. The delta system can also be grounded, as shown in Figure 2 below. When the bond is made from B phase to ground, you are simply creating a reference point. But, what I could do is put an auto-transformer between center of one side and the opposite corner. Check Details. The primary goal for a solidly grounded system is to open the circuit as quickly as possible to limit damage and risk to life. Trust is hard to come by in St. I've seen a center-tap on one phase that's tied to earth. IN reference to. The utility company says it is an un-grounded delta secondary at 480V/3-phase/3-wire system. The grounded leg is no more dangerous than the grounded neutral leg in a 120 volt circuit. It does NOT carry current like a neutral, a neutral carries the unbalance of the load. Frame size EMC filter (+E200) screw Ground-to-phase varistor screw R10, R11 EMC AC VAR Drive. LHL361005861). For use on 240 V systems, circuit breakers may be ordered as 480 V. 6. 2778 posts · Joined 2014. ) A 480/277-volt, 3-pole circuit breaker can be applied on a 480-volt corner-grounded delta. 20(A). We own the transformer. #4. If you do not ground one of the. Per the NEC, you need either GROUND FAULT MONITORING, OR you need to use a Corner Grounded Delta system. Grounded B-Phase Systems (Corner-Grounded Delta) PowerPacT B Electrical Accessory Wiring Diagrams. Also be aware that your gear will have to be listed for use with corner grounded delta and some loads are not acceptable for use on a corner grounded supply. A 120/240 breaker is intended for use on a system where the maximum voltage to ground is 120, and the maximum voltage line to line is 240. NEC 430. Marking on 3 phase matters especially with corner grounded delta as this sets up a wild leg that is required to be marked B leg and identified with orange phase tape the phases are 120 degrees out of phase so it matters how they are connected. grounded, corner grounded delta and ungrounded delta. 12,470/7200 grounded Wye primary and. Thread starter thebigmt; Start date Nov 24, 2010; Status Not open for further replies. This video is based. g. Its corner ground Delta 3 phase , 208 V , 30 horsepower. 26(4) and 250. W. Perhaps it should be extended to cover the grounded conductor of a corner grounded delta with a 170% factor. You cannot use a slash-rated 480/277V breaker on a 480V corner-grounded delta circuit because the line-to-ground voltage from two of the conductors. If you do ground one leg, you will only get zero on that one leg. We have a industrial setting with a corner grounded delta system. Not sure why you would see a voltage increase if you lost a primary phase, though. 480 Y/277 V, 3-phase, 4 W, solidly grounded VI. Re: Ground Fault Protection in Corner Grounded Delta System. Three single phase 480 transformers in a wye configuration. In Figure 4 below, we model an ungrounded (capacitively grounded) delta-connected power system connected through a single-phase fault to ground using a. Measured voltage on tenant panel 480 A-B, A-C, B-C. In a corner grounded delta system, one of the three phase legs is intentionally grounded. Now, there are exceptions. Not a corner grounded delta. Agreed, corner grounded delta, but strange that they have two separate conductors for 'grounded phase conductor' and 'neutral conductor'. is located/eliminated asap. Corner grounded delta systems produce crazy voltages, and crazy ground faults. I was planning on reverse feeding it with 208v, and getting 480v. It is found that, although this type of service is less expensive than solidly grounded wye service, 480 V corner-grounded delta service may not provide a safe working environment if used for oil-field service. It is both, ground and hot. Since one phase is already grounded this 4th wire is somewhat redundant. 86 restricting their use to solidly grounded systems where the line to ground voltage does not exceed the lower of the two values and the line voltage does not exceed the higher value. The grounded conductor is treated like a neutral in 120 V and 240 V single-phase systems. Occasionally, (especially in older facilities or in oil well and irrigation applications), you may encounter a three-phase delta service with one phase (leg) connected to ground, called a “corner grounded delta” or “grounded leg service”. Corner Grounded Delta Solidly (effectively) grounded (LRG) Solidly (or effectively) grounded systems connect (bond) the system neutral directly to earth ground. A lot of drives have surge suppressors that are designed for standard line to neutral voltages and don’t work with. An AC system supplying premises wiring must be grounded where the maximum voltage to ground from any. The ratings on the gen set are for 1 ph, 190 kVA - 240V 3 ph, 237 kVA 0. Therefore, it is not correct to refer to all grounded conductors as neutral conductors, although that is the case in the majority of electrical distribution systems. B phase to ground you have 0V. 7. With the corner grounded, you'll wind up with two phase to ground voltages equal to the phase to phase voltage and the third will be equal to zero. 6 are permitted to be used in services, feeders. It's a three-winding transformer - grounded wye primary, corner-grounded delta tertiary, grounded wye secondary with neutral grounding resistor. (2) In ungrounded systems, impedance grounded systems, or corner-grounded delta systems unless listed specifically for use on these systems. A grounded wye system. 10656 posts · Joined 2007. This creates a three. It's 830 wye. You are correct in that a corner grounded delta would have 240V L-L x3, the corner would have 0V to ground. 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. #1. 86 restricting their use to solidly grounded systems where the line to ground voltage does not exceed the lower of the two values and the line voltage does not exceed the higher value. #1 · Feb 28, 2020. #5. Location. Its incoming utility service is 480V, corner-grounded delta. - All Line to ground voltages read (L-L/1. System also requires a. 5. The size of the step-down transformer is. The correct application is 480 V or 600 V straight voltage ratings. Typically in my area BOY is used for any 480 volt power and if a grounded conductor involved, it is grey or marked grey. For starters the xformer 480 side, if grounded, all the load side gear and equipment must be approved for corner grounding-not likely. One of the phases, normally A phase, is connected to a grounding electrode. Most utilities would require for you to request a variance to get ungrounded Delta now, so if you don't ask for it, you get corner grounded. The earth. You have a different problem. Per NEC, not for use with ungrounded systems, impedance grounded systems or corner grounded systems (com-monly known as Three Phase Three Wire Delta, Three Phase High Leg Delta and Three Phase Corner Grounded Delta systems). You need transformers with a wye secondary and ground the center of the wye. . The center of the Y, which is usually grounded, must not be connected to anything. High-leg Delta "HLD" B/HL A N C G High-leg Delta This supply system configuration is not used in Europe. One phase center tapped to derive a different voltage. On a standard wye transformer, you would read 277v to ground on all three legs. looking for advice on working on a 3 ph, 3 wire 480 delta that i believe fits the definition of a corner grounded delta. not smaller than the required grounding electrodeCorner grounded Delta. My recommendation on corner grounded delta is to bolt all three phases together and hire a monkey to throw the main switch! But seriously, you'll have nightmares with corner grounded delta, it causes wierd ground. Other 2 phases = line voltage. One phase connected to ground. a delta winding, with the corner ground not causing any difference to actual operation unless the higher voltage from tap to ground is a specification issue, or. . You have a different problem. In a 240-volt corner-grounded delta, what is the voltage between C phase and ground? 0 volts. 73 =830v; I don’t think it’s a wye system, could just be an oddball system. . A high-leg system is a hybrid between a standard 3-wire single phase and a 3-phase system. That is a corner-grounded delta system. A ground fault in a floating delta circuit is a foreseeable event, no surprise, and ought to be protected against. on corner grounded delta when using Class J or R fuses. If you don't have VFDs or servos to contend with, then the NEC requires that you have EITHER a continuous ground fault monitoring system on an ungrounded Delta service, or you must use a "corner grounded" Delta system, wherein you tie one leg of your 480V transformer output directly to ground. 26(4) for conductor to be grounded. Aug 14, 2018. False. This is a system where one of the phase conductors of the 3-phase delta bank is intentionally grounded. This is coming from the corner grounded delta that is feeding the buss. i agree. Section 242. No magic and no mysteries. For example, corner-grounded delta systems contain a grounded conductor that is not a neutral conductor. In a delta configuration, the three windings are connected end-to-end to form a closed path. Grounded B-Phase Systems (Corner-Grounded Delta) PowerPacT B Electrical Accessory Wiring Diagrams. A high leg delta connection is a configuration in which one of the windings in a delta connected secondary of a transformer is centre-tapped and grounded. If that isn't possible, then the drive should be labeled as unsuitable for the floating delta and/or corner grounded delta. You're describing "high leg" or "wild leg" delta. 415V. Delta system. "A" or "B" phase short and the the OCP operates. Just because your house has 240 single phase doesn't mean there isn't any 240 3 phase systems. 160, 668. Section 250. It consists of a maximum current and the voltage at which the device is rated to interrupt the circuit. An open Delta is (almost) always a high-leg added to a typical 120/240v 1ph to supply a smaller 3ph load.