corner taped delta system

[fse2@aol.com]

can someone please help me understand why corner taped delta is used and how is it that one of the phases are being bonded to the panel hence bldg steel, A to B ,B to C, A to C are all 480v, yet your one phase to ground is 0volts. I can not wrap my head around this concept. All the books say the same thing, it does not make sence to me, please HELP.
Art.

 

[iwire]

Delta is used where you do not need a neutral. If you had a building or a section of a building that most of the loads where 3 phase motors that area would be a good canadate for a Delta service or feeder.

Once you decide to go Delta you need to decide if it is going to be grounded or not.

Ungrounded delta works well in industrial facilities that can not have down time but requires ground fault indication and personal to find and repair the ground fault ASAP.

Grounded delta does not need ground fault indication or people to keep an eye on it.

By bonding one phase of the delta system a ground fault on either of the other phases will be a line to line fault and quickly operate the over current devices.

The short answer is the bonding of one phases in a Delta system insures a reliable ground fault path to operate over current devices, just the same way as bonding the neutral in a Wye system does.

 

[rattus]

can someone please help me understand why corner taped delta is used and how is it that one of the phases are being bonded to the panel hence bldg steel, A to B ,B to C, A to C are all 480v, yet your one phase to ground is 0volts. I can not wrap my head around this concept. All the books say the same thing, it does not make sence to me, please HELP.
Art.

Look at this way:

With an ungrounded delta, the L-G voltages are determined by a divider network formed by stray leakage and capacitance. If you ground one corner of the delta, you merely short out one of the high impedances, and this forces the L-G voltage to zero. You have not changed the L-L voltages by doing this.

There is no difference in principle between the corner grounded delta and the grounded neutral of a wye servcie or a 120/240V residential service.