All EPDs occupy two spaces, with or without Alarm Switch option. Systems from Intermittent Ground Faults Introduction Many papers and standards [1][2][3][4][5][6] have discussed grounding of an electrical distribution system. might occur when Phase A goes to ground on a 480V, B-phase, corner grounded delta system. The grounded conductor is treated like a neutral in 120 V and 240 V single-phase systems. A corner grounded delta system will put more stress on the insulation between windings and ground. In a 240-volt corner-grounded delta, what is the voltage between C phase and ground? 0 volts. B would be 180 (ish) to ground. system in which the transformer secondary is delta-connected with one corner of the delta solidly grounded. Perhaps it should be extended to cover the grounded conductor of a corner grounded delta with a 170% factor. In a 480V, three-phase, 3-wire delta system, the voltage-to-ground is always 480V whether it is ungrounded or corner-grounded. The other two will be 240v to ground. Two ways to use the Grounded Conductor on 3Ph 3W Delta Two ways to use the Grounded Conductor on 3Ph 3W Delta Check out these Schematics, regarding a 3 Phase 3 Wire Corner-Grounded Delta, and the Two ways the. Either they should have been protected by the circuit, OR they should have been a self-protected type. GameStop Moderna Pfizer Johnson & Johnson AstraZeneca Walgreens Best Buy Novavax SpaceX Tesla. The three phase two wire corner grounded delta is the same as typical delta configuration and rarely used in the recent systems. 73) - Upon ground fault, the faulted phase L-G reading is zero and the other two. A corner grounded delta is not ungrounded. This section classifies the systems that must be grounded – unless prohibited elsewhere in the Code – into four categories. In residential, supplied transformer by the utility is normally one leg with center tap delta transformer. 3. That corner grounded delta system still needs equipment grounding conductors run beyond the service disconnecting means, you do not bond any equipment to the current carrying B phase at equipment you run separate EGC like you do for other voltage systems. ago. The grounded leg is no more dangerous than the grounded neutral leg in a 120 volt circuit. True. Sep 4, 2019. J. This is a system where one of the phase conductors of the 3-phase delta bank is intentionally grounded. I-Line) often require special breakers for 240V which are built using 3-pole housings. M. , In addition to the grounding. 26(4) for conductor to be grounded. 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. T. A two-pole circuit breaker applied on a 3-phase. 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. 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. This system exists to keep voltages stable, limit or reduce surges, and/or be required in compliance with electrical code. In this case, the breaker manufacturer must be consulted to verify interrupting ratings and proper application. "C" phase is solidly bonded to ground. 120V. 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. EPD circuit breakers may not be used in systems with phase to ground voltages other than 277 Vac. I recently had and issue with a 240v three phase Delta system while on the job. 3 phase 480 corner grounded delta. iceworm Curmudgeon still using printed IEEE Color Books. 120V. False Note: “Straight” rated circuit breakers are rated at 240, 480, or 600 volts and not 277/480 volts; which is a slash rating: Interrupting ratings on AC rated circuit breakers are used for ? . This supply system configuration is often used where high powers are required, for example for large motors. Image used courtesy of Lorenzo Mari . You can calculate the phase current of a delta transformer winding by dividing the phase VA by the phase volts: I Phase = VA Phase ÷E Phase. We use our. See figure 8. Corner grounded Delta transformer systems are known to confuse people. NEC 430. A phase is connected to each corner of the delta. 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. 2778 posts · Joined 2014. 208V. Location. For alarm switch, add the suffix BA. A lot of drives have surge suppressors that are designed for standard line to neutral voltages and don’t work with. Only one voltage is available from such a system, there would be no choice of 120/240 or 120/208 or 277/480 as would be available from other service types. 3–Phase Corner-Grounded Delta System using 2-Pole Circuit Breakers. 2) Adding a grounding autotransformer. High-leg Delta. to ground on a 480 volt corner grounded delta system. Commercial buildings require 3P4W and ground. High-Leg Delta power is only available in 120/208/240, and is not put in any longer as Wye circuits are. I believe it also allows you to save wire, but I am not sure. 5. three-phase, 3-wire, corner-grounded delta system? 120V 240V 277V 480V Correct Answer: 480V. rbulsara (Electrical) 16 Jun 05 20:28. System grounding is the connection to the ground – solidly or through impedance – of current-carrying conductors – e. The Article 100 definition for neutral was added in the 2008 NEC. There is absolutely zero reason to design B phase cornered system if you designing a new system. For a fault current of 5A, primary current will be 5 divided by 3, or 1. 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. ” Following areYou are correct in that a corner grounded delta would have 240V L-L x3, the corner would have 0V to ground. The system has accidentally become a corner-grounded delta system with little, if any, current flow. 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. , Premises wiring systems generally are required to be supplied by a system that is ? and includes a grounded conductor. For nominal 480 volts that high leg voltage is about 416. Remove EMC AC, VAR. The service is a corner grounded 240V delta. Consider the relative sizes of the tank and the electrodes. Next Last. 9A. This is a delta - delta transformer. B-PHASE SYSTEMS . But guess what, any line to ground fault will be 480v. Refer to the Digest, CAD drawings, or device wiring diagram(s. But how is the corner grounded of a Δ. I know right now there is a customer that is served by the POCO with ungrounded wye primary - corner ground 480 volt delta secondary, three transformers totaling 1000kVA. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. The utilty provider is coming in with 480 delta corner grounded c phase. Two of the most significant tests performed on a TVSS are the measured limiting voltage test and a series of abnormal overvoltage. Location NW Florida Occupation Electrical Jul 20, 2023 #8 Phase to neutral are 124, 214, 124. Check Details. e. Use QO-H circuit breakers only. The two pole breakers can handle 240V or more to ground, as would be seen in a 416Y/240 system or a 240/480 three wire single phase or a corner grounded 240 delta, but not the 480V to ground seen in a corner grounded delta. The system is a 240v 3phase corner grounded delta system with "B" phase intensionally grounded. A grounded wye system. Perhaps it was intended to be connected to a transformer. test Learn with flashcards, games, and more — for free. Glenwood landings for lipa has one. Its a separately derived system. For example, a 480 V, 3-phase, corner-grounded, delta-connected system cannot use a 480Y/277 V circuit breaker because the voltage of two phases to the ground exceeds 277 V. However, some utilities still provide this system, and many old installations still exist. ground continuity, enclosure impact, adequacy of mounting, and many others. They have 3 phase delta 480. 2. Grouch1980 said: Actually I didn't specify it. The motor will. ago. CMP said: Sounds like you have an ungrounded delta system, and your getting a capacitive voltage reading to your ghost ground. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. waross (Electrical) 6 May 15 10:54. JimmySki23 Member. 22 does not apply to the B phase of a center tapped 120/240 volt delta system. A diagram of such a system is shown at __ in figure 304. I came across a code a while back about NEC not allowing circuits to. A two-pole circuit breaker applied on a 3-phase, corner-grounded delta system must be marked 1Φ-3Φ. 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. Whichever you want to call it. Safety Switches Table 4 lists two-pole safety switches that are UL Listed for use on 240 and 480 Vac grounded B phase systems. Solidly (effectively) grounded (LRG) Solidly (or effectively) grounded systems connect (bond) the system neutral directly to earth ground. Square D carries a 2 pole breaker rated at 240V ( not slash. Open delta provides 57% (iirc) of the power that straight delta does with the same size transformers. 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). Select one: True. 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. 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 . 120 V, single-phase, 2 W, solidly grounded II. Best be taking some voltage readings and confirming what you have before making too many plans I would think. I've been given two different answers for the same set-up. Go. We have addressed neutral loads using individual 480V x 480/277V. I would not worry about it, but don't buy into the "kit" concept, tell them you want a 240V drive, or just use a 480V drive. Schneider Electric has tested equipment for use on corner-grounded delta systems to provide Underwriters Laboratories Inc. The other solution would have been to corner ground the 480 Delta, but I've posted before why I don't like that setup. 362K subscribers in the electricians community. When the bond is made from B phase to ground, you are simply creating a reference point. This parasitic capacitance appears in the zero sequence network as an impedance (XC) connected to the neutral bus. However, just like the 120/240 split phase secondary, it does carry current despite having zero volts relative to ground. The purposes are to: limit overvoltages due to lightning, line surges, or accidental contacts with higher-voltage. Might be more economical to just order 240V equipment and use whats there. The easiest way to ground a delta is at a corner, which also happens to be convenient in converting/upgrading ungrounded systems. However, some utilities still provide this system, and many old installations still exist. In a corner grounded delta system, one of the three phase legs is intentionally grounded. Because of the disadvantages of not grounding systems, electrical designers had to integrate a ground reference to existing configurations. 220. See Figure 11. 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. . Running the 480 as ungrounded presents a whole other set of issues. 480V. Jun 21, 2023. If you choose the corner grounded delta, you will lose your three phase power that you need. If all are zero to gnd, then probably a floating delta. Good points. This system has multiple transformers that go from 480-208 delta-delta and also 480v delta-208/120v wye. 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. #3. 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 to indicate such suitability. Phase ab 240v, ac 240v, bc 240v, a to ground 120v, b to ground 0v, c to ground 120v. The line is also safe to touch even when it is not properly bonded only when the load is shut off. #1. 85 Applications. For starters the xformer 480 side, if grounded, all the load side gear and equipment must be approved for corner grounding-not likely. Its hard to visualize attaching 1 of 3 energized lines to ground. Compared with the solidly-grounded wye system of Figure 1 this system grounding arrangement has a number of disadvantages. It would seem to me, that there is no difference in principle between the grounded conductor in a 3 phase, 4 wire delta system, the grounded conductor in a 3 phase, 4 wire Y system, or the grounded conductor of of a 3 wire 240/120 volt system, or the grounded corner of a delta system as being disscussed. e. It kind of freaks me out measuring 0 volts to ground on a open buss 4-5 thousand amps switchgear in the powerplant. teal854t Discussion starter · Oct 13, 2010. 3, July 2022 -Corner-grounded delta grids not supported at voltages of 400V / 480V. High-leg Delta "HLD" B/HL A N C G High-leg Delta This supply system configuration is not used in Europe. And Delta ground monitor. It is quite common as a separately derived system for 230 volt equipment in a plant with a 480 volt service. Corner grounded delta. 1. Similar to the methods used to Ground all other Solidly Grounded AC Power Systems, the "Corner Grounded" Delta has Ungrounded. 4. If that isn't possible, then the drive should be labeled as unsuitable for the floating delta and/or corner grounded delta. Corner-grounded delta: One line conductor is grounded directly. The minimum size of the grounded service-entrance conductor is a. The corner grounded delta (CGD) is one of the earliest forms of grounded systems in electrical installations. 4. . 480 V, 3-phase, 3 W, ungrounded or high resistance grounded VII. The delta system has a phase-to-phase voltage of 240 V. Corner grounded is normally in industrial and commercial applications. Aside from the corner-grounding of the delta, this is a fairly common configuration for transmission substation transformer in the US. 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. BTW, this is a grounded system. Same with "wild leg" center grounded delta, which is also becoming obsolete. "C" phase is solidly bonded to ground. 85 of the 2002 NEC was changed to read: 240. Introduction Corner-grounded delta systems are not re commended for new installations. Get a new disconnect with a neutral bar and run the incoming corner grounded phase into the neutral bar. Introduction Corner-grounded delta systems are not re commended for new installations. is located/eliminated asap. Trying to determine if I have a ground fault somewhere or a bad leg or breaker. From there a grounded phase conductor and equipment ground go to the disconnect and remain separate. e. NEMA Type 7/9 SCCR 10 kAIR 600 Vac maximum. to ground on a 480 volt corner grounded delta system. Aside from the corner-grounding of the delta, this is a fairly common configuration for transmission substation transformer in the US. Evans said: Yes, 3 phase/3 wire is used sometimes. 240V. However, the grounded phase is still current carrying just like a neutral is current carrying and is grounded. The three pole breakers are designed for the higher voltage to ground found in a corner grounded. Only for use with 480V Wye systems. 3 pole breakers may be used for 3 phase loads with grounded phase connected through a breaker pole. What is the minimum size required for a copper grounded conductor of three phase, three wire, corner grounding delta system if the ungrounded. 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. Remote Operation (MN/MX Voltage Release) Let-Through Curves and Trip Curves. Corner Grounded Delta. 23(A)(2) show instances. Now, there are exceptions. Trust is hard to come by in St. I agree it appears to be a corner grounded 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. 85 covers the requirements for straight rated and slash rated CBs. thebigmt Member. 3. NEC expert Mike Holt explains how to properly ground a corner grounded delta system and the special characteristics of these rare systems. 208 Y/120 V, 3-phase, 4 W, solidly grounded IV. g. I would normally only use a solid corner ground on a. Kettle's on. You have a different problem. Installations with this system require a 480-120V transformer to supply 120V lighting. 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. More. A two-pole circuit breaker may not be used for protecting a 3-phase, corner-grounded delta circuit unless the circuit breaker is marked 1Φ—3Φ to indicate such suitability. Version 1. At the MV level corner grounded delta is exceptionally rare. Circuit Breakers for Grounded B-Phase (BØ) (Corner-Grounded Delta) Systems. I had NEVER heard of corner grounded delta, so my head was full of confusion when line to line, and line to ground were equal. 102(C)(1) for sizing the grounded conductor. 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 theThe system is “corner grounded”, one leg of three phase delta is tied to ground. We have a industrial setting with a corner grounded delta system. 240. ® (UL®) Listed products for this application. - One phase is intentionally grounded. 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. It's a three-winding transformer - grounded wye primary, corner-grounded delta tertiary, grounded wye secondary with neutral grounding resistor. Retired Electrical Engineer - Power Systems. For use on. 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. This supply system configuration is often used where high power is required, for example for large mo-tors. 5% each you coould. We have an old system in our plant that is the grounded B phase or the corner grounded delta. High leg delta has the mid point of one side. One method of grounding a three-phase, three-wire, delta-connected system is to ground one of the phase conductors. The cost of running a neutral to the service disconnect seems like a cheap way to save expensive headaches. 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. Furthermore, 3-phase, corner-grounded, delta circuits can only use two-pole circuit. Perhaps some. Proper grounding reduces. Select one: a. PowerPacT B-Frame Let-Through Energy Curve. Louis. 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. Typically in my area BOY is used for any 480 volt power and if a grounded conductor involved, it is grey or marked grey. It's 830 wye. corner grounded delta systems, considers the circuit breakers’ individual pole interrupting capability. The solidly-grounded wye secondary is the modern way to go for 600V. 408. If you choose the high leg delta, you'll need to pull a grounded conductor anyway. That 'neutral' is of course not a neutral, but a parallel 'grounded phase' conductor. Per the NEC, you need either GROUND FAULT MONITORING, OR you need to use a Corner Grounded Delta system. Not available with HA option. For use on 480 V systems, LH type circuit breakers must be ordered as 600 V versions and with a 5861 suffiix (i. Corner-Grounded Delta Circuits. 3131 Delta St Victoria BC V8Z 1A6 (250) 884-1942. However, some utilities still provide this system, and many old installations still exist. I've seen corner-grounded systems where one phase is tied to earth. Be careful when installing slash-rated breakers on a solidly grounded high-leg delta system. Corner grounded delta systems are good in theory, but only with older types of loads. You will measure 480 volts from either A phase or C phase to ground, B phase to ground will measure 0 volts. 2 requires a grounded conductor in all premises wiring. ) Only standard ampere rated fuses and circuit breakers found in 240. D325NT, D325NTR, D326NT, D326NTR, T327N and T327NR accept only 300Vac Class T fuses. -John. It requires connecting the impedance grounding conductor. Occasionally you may have an application that is a delta voltage source with a grounded “B” phase, also known as corner grounded. 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 ungrounded delta system except the transformer windings are grounded. LHL361005861). 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. In most cases, the delta is "buried" with no leads. ® (UL®) Listed products for this application. You still must run a separate grounding conductor to bond non current carrying components - so you are running 4 wire circuits either way you do it. Other standard delta is one with mid point of one phase grounded - this leaves you with a high leg to ground on the opposite corner of the grounded point. 20(A). D. 1 of 2 Go to page. Because of the size and complexity of Grounding and Bonding, Article 250 is subdivided into the. But, what I could do is put an auto-transformer between center of one side and the opposite corner. T. 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. 796v is what's marked on a motor used on these 830 systems. If you had a corner grounded delta, B phase grounded and A phase shorts assuming you protected everything per the NEC you would have a ground fault and the fuses would blow or the CB open. Not sure if that's the technical name or not. ain't going to end well. Location. Corner grounded delta will read 480 anywhere you put a meter, except one phase will be 0 volts to ground. It has (in this instance) 480v relative to the two other phases, and is 1/3 of the 3 phase circuit. Along with the 'slash rating', Corner Grounded (grounded B phase) systems can impact the AIC ratings of breakers. The earth as a conductive body can serve as an effective ground-fault current path to facilitate the operation of fuses or circuit breakers protecting the system. A corner grounded delta power system is a configuration where one of the phases (typically B phase) is solidly grounded. 277V. ) Branch-circuit fuses do not have to be marked with their ampere rating. Informational Note: An example of a system permitted to be grounded is a corner-grounded delta transformer connection. System also requires a. 208, 240 and 480 are all common 3 phase systems. Remember, voltage is a difference in potential. This video is based on the 2020 NEC and was extracted. Corner Ground Delta. However, some utilities still provide this system, and many old installations still exist. The others will be your expected phase to phase voltage to eachother and ground. Ungrounded Delta: - No phase is intentioally grounded. The size of the step-down transformer is. Corner grounding a delta secondary, will most likely cause more equipment damage than you currently are having. Grounded B-Phase Systems (Corner-Grounded Delta) PowerPacT B Electrical Accessory Wiring Diagrams. On the primary side, what is the voltage to ground on each phase? If one is zero and the other two are 480 or 525 then yes it is a corner grounded system. Could be as jraef mentioned. Also, you can save. The only equipment bonded together is the main panel board case to the cable tray. No 120/240VAC circuit breakers may be used on any corner grounded delta system. When solving for phase current, don’t forget to divide the overall transformer kVA rating by 3. 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. 240V. Neutral Conductor. We would like to show you a description here but the site won’t allow us. [9] 22 k AIR main circuit breaker UL Listed for use ahead of QO, QOT and QO-PL 10 k AIR branch circuit breakers to permit their application on systems with up to 22 kA available fault current. They were very popular on rural farms where the predominant building load was single phase, but the milking parlor. 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). Equipment ground bonds to disconnect and grounded phase connects to unfused pole. So all of the breakers you need to. not smaller than the required grounding electrode Corner grounded Delta. (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. Corner grounded systems often employ 2 pole circuit breakers and distribution panels which would need to. Particularly common if only building open delta, though there is still some existing full delta, but most new systems with three transformers are going to be 480/277 anymore. J. One-line diagram symbol for a start push button _____ and a stop push button _____ Step-by-step solution. This question references Article 240. gap, is maximum. If phase B is intentionally corner-grounded, then contact from phase B to ground is not a ground fault. Question I have is I believe I need to utilize a corner grounded delta on the 480v side, otherwise the system is not grounded. It is a 240v CGD. 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. Installations with this system require a 480-120V transformer to supply 120V lighting. They based it on current measurements they took at the pole after checking and cleaning all connections. The MOV surge protectors in your drives will not like one or two legs of a higher voltage to ground. Almost as if the utility decided to run an EGC for giggles. . 67, or 57. 10656 posts · Joined 2007. Rick It is both, ground and hot. Minnesota Electrical Code 2020 > 4 Equipment for General Use > 408 Switchboards, Switchgear, and Panelboards > 408. 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. Abstract Many factors must be considered when designing the electrical system for critical facilities, especially the type of ground system used. This video covers voltage relationship for a Delta source or load. 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. Also don't forget that NEC doesn't apply on the utility side of the interconnection point. The inverters may not like the elevated voltages to ground. - All Line to ground voltages read (L-L/1. 73 =830v; I don’t think it’s a wye system, could just be an oddball system. 242. 160, 668. On a 240V 3 phase grounded delta system, the voltage to ground is 240V from 2 of the poles. OccupationHey this happens all the time. In addition, if you have any sort of rectification stage, for example in a VSD, then the DC rail voltages relative to ground will be very different. See data bulletin 2700DB0202. 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. A.