ppsh41pro • 10 mo. Not sure if that's the technical name or not. It could also prohibit a corner grounded 240V delta since using a grounding transformer a 240V system could be grounded with a L-G voltage of only 139V. You only need two current transformers to monitor the power in a 3 phase, 3 wire system. I have multiple 240v single phase loads and (1) 240v 3 phase load. It's a three-winding transformer - grounded wye primary, corner-grounded delta tertiary, grounded wye secondary with neutral grounding resistor. 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. For a fault current of 5A, primary current will be 5 divided by 3, or 1. 36 requires where fuses are used for motor overload protection that a fuse be also inserted in the grounded conductor if the supply system is a corner-grounded delta system. High-leg Delta. This system can operate either at 480 volts or at 240 volts. Wye-wyes are extremely rare in <600V systems. Three-Phase, 240 Volt, 3-Wire Corner Grounded Delta: The 3-phase, 3-wire, delta corner grounded electrical system is used generally for the same applications as the. Louis. A grounded wye system has each phase at line voltage divided by the square root of three above ground. Apr 28, 2020. However, some utilities still provide this system, and many old installations still exist. A new transformer was set for a motor load to step up to 480 volt. A corner grounded delta power system is a configuration where one of the phases (typically B phase) is solidly grounded. Think about this a little more. 408. Read also : what is an operational amplifier. Aug 14, 2018. 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. While the rail-rail DC component of the rectifier output is the same in both wye and corner. What we have is 4160V feeding 4 step down transformers that step it down to 230V Grounded B. 220. Save. I recently had and issue with a 240v three phase Delta system while on the job. Location DFW, Texas. Used to be more corner ground around, but some POCO don't offer it at all anymore and have even converted any they had to three phase 4 wire whether it be. Phase ab 240v, ac 240v, bc 240v, a to ground 120v, b to ground 0v, c to ground 120v. , Premises wiring systems generally are required to be supplied by a system that is ? and includes a grounded conductor. In most cases a corner grounded delta is a very poor choice of supply as it has a. . 3 pole breakers may also be used for single phase loads which will be connected through the outside poles. 155, 517. System also requires a. A. Home. Corysan said: 240V 3ph corner grounded delta will definitely yield: A-Grd: 240V. Just because your house has 240 single phase doesn't mean there isn't any 240 3 phase systems. three-phase, 3-wire, corner-grounded delta system? 120V 240V 277V 480V Correct Answer: 480V. Do not install them on corner-grounded, resistance-grounded, or ungrounded systems. Subsection 250. 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. "C" phase is solidly bonded to ground. Square D carries a 2 pole breaker rated at 240V ( not slash. The corner grounded delta (CGD) is one of the earliest forms of grounded systems in electrical installations. One-line diagram symbol for a corner-grounded delta transformer _____ l. ® (UL®) Listed products for this application. ) Branch-circuit fuses do not have to be marked with their ampere rating. Grounding center of one side (high leg 240/480 delta) might still be too high a voltage. , the neutral point of a wye-connected transformer and the phase on a corner-grounded delta connection. Almost as if the utility decided to run an EGC for giggles. Although delta windings are often operated ungrounded, a leg of the delta can be center tapped and grounded, or a corner of the delta can be grounded. ) A 480/277-volt, 3-pole circuit breaker can be applied on a 480-volt corner-grounded delta. I believe that you are not supposed to connect any single phase loads between the high leg and the neutral. 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. As detailed above, a delta secondary Transformer cannot have a neutral, while a center-tapped delta secondary Transformer, once the center-tap is bonded to the nearest earth ground per the NEC by the installer, can have a limited. Measured voltage on tenant panel 480 A-B, A-C, B-C. Then leg to ground 480 479 0. Some connections like ungrounded wye grounded wye are not feasible, but something like delta grounded wye or ungrounded wye corner grounded delta is doable and operational. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. There is of course the resistance-grounded wye, if needed, for industrial. T. NEC actually calls it the "grounded conductor" which would seem to open up the possibility of corner grounding one of the three phase conductors. ¿Busca un manual de instalación rápida para el convertidor de frecuencia ACH580-01 de ABB? Descargue este documento en formato PDF y siga las instrucciones paso a paso para configurar el dispositivo y conectarlo a su sistema HVAC. 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. micromind · #7 · May 3, 2023. However, the grounded phase is still current carrying just like a neutral is current carrying and is grounded. 24(C) Grounded Conductor Brought to Service Equipment and immediately below in (C)(1) is a reference to 250. We have addressed neutral loads using individual 480V x 480/277V. This is a system where one of the phase conductors of the 3-phase delta. "C" phase carries current just like a ungrounded delta or a 3 phase 4-wire wye. This freaks people out, but it is totally legit. 20 informational not refers to a corner grounded delta tranformer. Corner grounding a delta secondary, will most likely cause more equipment damage than you currently are having. I have a job where they want to install a Dan Foss FC202 on a pump. We have a 480 only corner grounded delta service. However, some utilities still provide this system, and many old installations still exist. The secondary in this building is a 480V Corner Grounded Delta or Grounded "B" Phase Delta, whatever it is called. Pretty curious though. Hi, Our company rented an old warehouse and this is the first time I've ever seen corner ground delta (CGD) panel. It is used to reduce wiring expenses by utilizing a service cable that has only two insulated conductors instead of the three insulated conductors typically. There are multi-tap ballast units, which can be 480V, 240V, or 208V, in addition to 277V, all of which are Line-to-Line connections. For use on 480 V systems, LH type circuit breakers must be ordered as 600 V versions and with a 5861 suffiix (i. Mr. Jan 26, 2017. If phase B is intentionally corner-grounded, then contact from phase B to ground is not a ground fault. A and C to ground could be 120 (ish), 128. 796v is what's marked on a motor used on these 830 systems. The primary goal for a solidly grounded system is to open the circuit as quickly as possible to limit damage and risk to life. 415V. Being that a GF would. e. teal854t Discussion starter · Oct 13, 2010. Two phase-ground voltages = 480V and one phase-ground. #4. In the setup the OP describes, the maximum voltage to ground would be 240, so he must use a straight 240 V breaker. Could be the outlet is miswired or mis-breakered and has two of one line and one of a second. These connections do. #20. to ground on a 480 volt corner grounded delta system. One of the phases, normally A phase, is connected to a grounding electrode. Where a service is supplying from a corner – grounded system, and the ungrounded conductors are sized at 750 kcmil copper, What is the minimum size required for the grounded conductor?. If the phase line was solidly grounded you would be reading 0 volts. If that isn't possible, then the drive should be labeled as unsuitable for the floating delta and/or corner grounded delta. 5. M. corner grounded delta systems, considers the circuit breakers’ individual pole interrupting capability. Now, there are exceptions. This demonstration video shares the wiring, voltage and history of a corner grounded delta bank. 5869 posts · Joined 2009. A corner grounded power system is a system that is fed from a delta transformer winding with one phase grounded. I came across a code a while back about NEC not allowing circuits to. The 277 volt is interesting but, not relevant. The only time you will see delta B corner grounded is when original older system was ungrounded and it was modified to be grounded by taking B phase and intentionally grounding it. The motors operate at a nominal supply voltage of 220 volts, 3 phase. Informational Note: An example of a system permitted to be grounded is a corner-grounded delta transformer connection. Nov 24, 2010 #1. When you open the secondary side of the 500kva transformers the center phase has a 500mcm bare. Now if your delta distribution system is corner grounded or ungrounded with an unrepaired ground fault you will have serious problems. Location Roughly 5346 miles from Earls Court. This is an important marking to note as we. - All Line to ground voltages read (L-L/1. The motor will. I figured at the least it would cause a phase loss alarm, but wasn't sure if there. i agree. Section 250. Open delta provides 57% (iirc) of the power that straight delta does with the same size transformers. It is not a phase conductor, it is a grounded circuit conductor just like the neutral on the common 120/240 volt single phase system. 85 of the 2002 NEC was changed to read: 240. We are doing this to avoid required ground fault protection in the breakers. 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. 22 does not apply to the B phase of a center tapped 120/240 volt delta system. If the leg chosen is the B phase, then the voltage to ground for A and C will be 240 volts, while for B it will be zero. See Figure 11. So all of the breakers you need to. Corner grounded Delta (One phase conductor is connected to the grounding electrode system. A phase is connected to each corner of the delta. J. This system exists to keep voltages stable, limit or reduce surges, and/or be required in compliance with electrical code. 1. What about a corner grounded delta? This is still a grounded system but does not have a "neutral" per say. 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. kclark8799 Member. A circuit breaker with a slash rating, such as 120/240V or 480Y/277, shall be permitted to be applied in a solidly grounded circuit where the nominal voltage of any conductor to ground does not exceed theOne thing I think would work is if the 480V delta had center-tapped windings, 240/480V. Leave EM1 connected. Circuit Breakers for Grounded B-Phase (BØ) (Corner-Grounded Delta) Systems. 6 are permitted to be used in services, feeders. Since one phase is already grounded this 4th wire is somewhat redundant. Good points. No magic and no mysteries. 85. Yes, that is my understanding too. Introduction Grounded systems offer many benefits over ungrounded systems [1][2][3]. Aside from the corner-grounding of the delta, this is a fairly common configuration for transmission substation transformer in the US. You have a different problem. 240V. Open delta 480 volt service. An open Delta is (almost) always a high-leg added to a typical 120/240v 1ph to supply a smaller 3ph load. Looking at a 120/208 wye system, the phase voltage would be 120V and the phase-to-phase voltage would be 208V. D325NT, D325NTR, D326NT, D326NTR, T327N and T327NR accept only 300Vac Class T fuses. Is the transformer output an ungrounded or corner grounded delta? If ungrounded, a ground detector must be provided. However, some utilities still provide this system, and many old installations still exist. ® (UL®) Listed products for this application. This creates a three-phase, corner-grounded system, sometimes referred to as an end-grounded system. Abstract Many factors must be considered when designing the electrical system for critical facilities, especially the type of ground system used. Systems from Intermittent Ground Faults Introduction Many papers and standards [1][2][3][4][5][6] have discussed grounding of an electrical distribution system. In a delta configuration, the three windings are connected end-to-end to form a closed path. D. The inverters may not like the elevated voltages to ground. If you built the system using say a corner grounded delta (say B phase grounded) then you would see high current from A to B and from C to B but I suspect. Electric circuit : open & short circuits instrumentation toolsTransformer phase wiring 480v 208v diagram 480 delta wye 15kva vac Diagram of delta connectionThree phase transformer connections. Corner-grounded systems were used to supply services serving only a 3-phase load such as a well pump. So enter the corner grounded delta secondary. - All Line to ground voltages read (L-L/1. We have an old system in our plant that is the grounded B phase or the corner grounded delta. Corner-Grounded Delta System. Also note the one can use a slash rated breaker on a corner grounded 240 delta, it just has to be a 480/277 rated breaker. For use on 480 V systems, LH type circuit breakers must be ordered as 600 V versions and with a 5861 suffiix (i. 2 pole fusible disconnects and 120/240V panels are sometimes rated for 240V three phase. b. One phase center tapped to derive a different voltage. If grounded, then a ground fault protector may be desirable although not required. The type of service that you are referring to is a 4wire, mid point grounded Delta; VTP99 is describing a 3wire, corner grounded Delta. MRG, Article 200. L. It's a three-winding transformer - grounded wye primary, corner-grounded delta tertiary, grounded wye secondary with neutral grounding resistor. Remember, voltage is a difference in potential. Because of the disadvantages of not grounding systems, electrical designers had to integrate a ground reference to existing configurations. 480V – 3-Phase, 2-Wire – Corner Grounded – Delta. Not available in E04 or F04. Warning: If two-pole circuit breakers are installed in a corner-grounded delta system, they must be marked to indicate such suitability. The ratings on the gen set are for 1 ph, 190 kVA - 240V 3 ph, 237 kVA 0. An ungrounded (floating) delta should have a ground indicator to alert maintenance personnel because a second ground may be catastrophic. 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 is also a. Furthermore, 3-phase, corner-grounded, delta circuits can only use two-pole circuit breakers marked 1ɸ-3ɸ. If one phase is zero volts to ground, you probably have a corner grounded delta. Informational Note: An example of a system permitted to be grounded is a corner-grounded delta transformer connection. When the bond is made from B phase to ground, you are simply creating a reference point. When you open the secondary side of the 500kva transformers the center phase has a. The delta system can also be grounded, as shown in Figure 2 below. True. 120 V, single-phase, 2 W, solidly grounded II. Assuming you adjusted the taps at 2. A corner grounded power system is a system that is fed from a delta transformer winding with one phase grounded. Once wired up as a delta bank, the system is now a three phase system and has a phase-to-phase voltage of 240V, the same voltage as the phase voltage. The secondary in this building is a 480V Corner Grounded Delta or Grounded "B" Phase Delta, whatever it is called. 480V. . It could also prohibit a corner grounded 240V delta since using a grounding transformer a 240V system could be grounded with a L-G voltage of only 139V. This supply system configuration is often used where high power is required, for example for large mo-tors. 6. For use on 240 V systems, circuit breakers may be ordered as 480 V. 4. If that isn't possible, then the drive should be labeled as unsuitable for the floating delta and/or corner grounded delta. Grounding B phase is standard when working with older. Sections 503. See figure 8. The other two will be 240v to ground. 30 (A) (1) (3) (c) in the 2020 NEC pertains to Delta-Connected Systems, in particular 3-phase, 3-wire delta systems with a grounded conductor. Do not remove EMC AC or VAR. No, it is not showing the high side delta winding is corner grounded. If an electrical system is grounded as a requirement or by choice, all the rules related to grounded systems must be applied. Corner grounded delta. See 250. Have to physically see the MBJ to. 02. 1) The neutral system has lower line-ground voltages 2) In a corner grounded HRG system, detecting ground faults in the grounded circuit conductor would be more difficult. Perhaps it was intended to be connected to a transformer. When wiring up electrical service configured as 3-phase corner-grounded delta, it would seem that the appropriate way to connect overcurrent protection would be to make the 2 ungrounded wired breakable, and pass the grounded wire straight through. While it is a grounded conductor, the grounded phase of a corner-grounded delta grid is not technically a neutral. Furthermore, 3-phase, corner-grounded, delta circuits can only use two-pole circuit. On this latter type, one phase is indeed grounded and is 0 volts to ground. 230 is also a 3 phase system voltage that comes in a couple of different flavors: Corner grounded Delta, or a mid point grounded Delta with the B phase bastard leg. Corner grounded delta. Always wear your gloves. The B phase to ground voltage should be 1/2 of the line voltage. ”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. This section requires a surge arrester connected to each. For me, its a textbook corner grounded delta. Installations with this system require a 480-120V transformer to supply 120V lighting. 9A. Neutral Conductor. Commercial buildings require 3P4W and ground. g. If a phase opens, that is still a phase loss. Figure 4 – Fault to Ground on a Corner-Grounded Delta System A disadvantage of Corner-Grounded Delta systems is the inability to readily supply voltage levels for fluorescent or HID lighting (277V). 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. Our PoCo will not supply it, but many factories install it currently. 10656 posts · Joined 2007. Hi, Our company rented an old warehouse and this is the first time I've ever seen corner ground delta (CGD) panel. Section 242. 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. 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. For 240V delta corner ground, it's 240V three phase, or 240V single phase, what I said was that you can't use the B phase as a single phase anyway, because it's ground, therefore your potential is zero! For 240V delta high leg, you can get 120V, 240V, and 208V (only single pole). IESNA. Version 1. 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. Next Last. L-N: 277V L-L: 480V 480V. Introduction Corner-grounded delta systems are not re commended for new installations. They are available. The NEC® addresses slash voltage ratings for circuit breakers in 240. 8. Directions Advertisement. Perhaps some. 277V. 2, September 2021 - updated list of supported inverters . corner grounded Delta system. -John. Corner grounded delta bank is three wire, grounded delta. The NEC® addresses slash voltage ratings for circuit breakers in 240. Otherwise the delta would be corner grounded (grounded 'B' phase). 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. This system exists to keep voltages stable, limit or reduce surges, and/or be. Small residential is normally single phase 2 wire or single phase 3 wire. You must also bond the phase to the case with a jumper sized to 250. By "fail", it would have to mean a GROUND FAULT. . Because of the disadvantages of not grounding systems, electrical designers had to integrate a ground reference to existing configurations. The maximum continuous operating voltage is measured from phase to phase for impedance grounded and ungrounded systems. PowerPacT B-Frame 15/20 A Thermal-Magnetic Trip. I've been given two different answers for the same set-up. NEC section 250. corner grounded Delta system. looking for advice on working on a 3 ph, 3 wire 480 delta that i believe fits the definition of a corner grounded delta. Location AIken SC. PowerPacT B-Frame 15/20 A. zbang Senior Member. Such a system changes to a corner. SPD requirements. Occupation. . 24(D)(4) This section covers impedance grounded services. GameStop Moderna Pfizer Johnson & Johnson AstraZeneca Walgreens Best Buy Novavax SpaceX Tesla. So on A phase to ground you have straight 480V. Running the 480 as ungrounded presents a whole other set of issues. 20(A). For nominal 480 volts that high leg voltage is about 416. The corner-grounded phase acts in much the same way as the grounded neutral of the single-phase Edison system, carrying current and maintaining ground potential. A high-leg system is a hybrid between a standard 3-wire single phase and a 3-phase system. 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. If it is a 480 volt system, you should read 480 v between each phase. This video is based. Utilities are trying hard to get rid of corner grounded delta systems. 20. However, just like the 120/240 split phase secondary, it does carry current despite having zero volts relative to ground. A corner grounded delta power system is a configuration where one of the phases (typically B phase) is solidly grounded. That would be a fairly simple fix in the panel, assuming that the panel is 3ph, not 1ph. ” Following areYou are correct in that a corner grounded delta would have 240V L-L x3, the corner would have 0V to ground. 480V. Is this a corner grounded delta secondary as. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. By doing so, we are creating a split phase supply as well as a three-phase delta connected supply. Joined Jan 25, 2011. 20, Informational Note. It is a 240v CGD. And Delta ground monitor. Grounding is important as it provides a current path back to the source should an ungrounded conductor fault to ground. 120/240 V, single-phase, 3 W, solidly grounded III. Corner-Grounded Delta System. Aquavar CPC For R4 or N4 frame size, remove EM3. It does NOT carry current like a neutral, a neutral carries the unbalance of the load. Use of a slash rated breaker on a corner grounded delta is not ruled out by it not being solidly grounded but by the voltage to ground on the two ungrounded wires being greater than the second number in the rating. Aside from the corner-grounding of the delta, this is a fairly common configuration for transmission substation transformer in the US. Similar to the methods used to Ground all other Solidly Grounded AC Power Systems, the "Corner Grounded" Delta has Ungrounded. Menu. These are obsolete methods but can still be found, mostly in older industrial areas. 1) The neutral system has lower line-ground voltages 2) In a corner grounded HRG system, detecting ground faults in the grounded circuit conductor would be more difficult. According to mike holt one random? corner phase is to be grounded and bonded to the case of the transformer. Location Kentucky Occupation Electrician Jan 21, 2021 #1 Our system had 490 phase to phase. 61 (A) Exception has a requirement for a 140% factor for calculating the neutral load from the unbalanced load on a 2-phase feeder. The correct application is 480 V or 600 V straight voltage ratings. B phase is bonded to ground at the transformer lugs, not in the switchgear. On the utility side, the transformer can either be. Der PE-Schutzleiter (GND) darf keinen Strom tragen! Der Neutralleiter N (Grounded Conductor) ist dabei als getrennter Leiter anzulegen und erst innerhalb der Verbraucherablage abzugreifen. AC systems of less than 50 V. To obtain UL certification, the TVSS unit must pass all tests. #5. Circuit breakers marked “1-phase – 3-phase” or “10I – 30I “are suitable for use on are removed. Corner grounded is normally in industrial and commercial applications. The other two phased are at the line voltage above ground. Jun 21, 2023. Location. Trying to determine if I have a ground fault somewhere or a bad leg or breaker. rbulsara (Electrical) 16 Jun 05 20:28. The maximum continuous operating voltage is measured from phase to ground for solidly grounded systems. 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). For use on 240 V systems, circuit breakers may be ordered as 480 V. 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. 120V. This can be avoided by simply checking more than one leg, but the plain fact is that the customer doesn't like corner-grounded delta, and doesn't want it used. #4 · Oct 2, 2020. According to mike holt one random? corner phase is to be grounded and bonded to the case of the transformer. Industrial mostly, and irrigation pumps. In this case, the breaker manufacturer must be consulted to verify interrupting ratings and proper application. Typically in my area BOY is used for any 480 volt power and if a grounded conductor involved, it is grey or marked grey. Corner-Grounded Delta (Grounded B Phase) Systems 2700DB0202R2/09 Data Bulletin 02/2009. About Quizlet; How. 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”. 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. 242. BUT you have a 2 to 1 transformer (480/240=2 to 1) at 208 in you would get 416 out. NEC 240. The minimum size of the grounded conductor for a 3-phase, 3-wire, corner-grounded, delta connected service is a. 8]. The grounded conductor of a service is usually a neutral conductor, but it can also be a phase conductor, depending on the type of system supplied. We use our. They have 3 phase delta 480. iceworm Curmudgeon still using printed IEEE Color Books. 67A; secondary current will be 1. Its a separately derived system. A corner-grounded or an un-grounded. 3-phase corner-grounded delta or single-phase circuits (NEC 240. They were common about 50 years ago or more. 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. Corner Grounded Delta Solidly (effectively) grounded (LRG) Solidly (or effectively) grounded systems connect (bond) the system neutral directly to earth ground. 5869 posts · Joined 2009. The MOV surge protectors in your drives will not like one or two legs of a higher voltage to ground. My question is on the secondary side I need to take a bonding conductor from any of the three phase to ground to created a corner grounded delta, I know I've done a set up like this in the past but grounding a phase always makes me. 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. Corner Grounded Delta. NEC 430. 600 Y/347 V, 3. About us. • 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. Corner-grounded delta system. .