Earthing System?

Status
Not open for further replies.
M

matthewmurphyj

Member
Location
Allentown, PA, USA
Hello all,

This is my first post, but I have been coming here for information for a very long time. I am well versed in IEC and EN directives as most of the work I have done in the past has been on equipment intended for Europe. I need some help converting a IEC concept to an NEC one. My question is in regards to High Leg Delta and earthing systems in the US. I am installing a Siemens VFD in a control panel. I have everything else worked out except I don't know how to figure out what earthing system is in use at the facility. The facility uses high leg delta where the B leg is high. According to Siemens, the G120 converter will not have any problem with this supply, but they could not give me any information on the earthing system used. My best guess is that it is a TT system because there is a neutral wire supplied from the transformer, but there is no path to ground provided by the service. Also, a RCD should be used on the main feeder circuit. The earthing system will have a great impact on how the filtering and line reactor are set up according to the manufacturer. Can anyone tell me wether or not my interpretation of the high leg delta supply is correct?

Thanks all!
 
A High-Leg Delta earthing system in the US is handled in the same manner as a three phase 208Y/120, or single phase 240/120 system.
The "neutral", grounded conductor, is bonded at the service and a grounding electrode system is established there.

(Note 3 wire ungrounded delta systems and corner grounded delta system are also in use in some areas but "earthing" is pretty much handled the same)
 
Last edited:
Augie,

Thank you for clarifying that, I believe it is actually a TN system then. The neutral comes off of the transformer, into the facility, and is then bonded to the protective earth at the point of use.

Thank you for the help!
 
matthewmurphyj said:
Augie,

Thank you for clarifying that, I believe it is actually a TN system then. The neutral comes off of the transformer, into the facility, and is then bonded to the protective earth at the point of use.

Thank you for the help!
Click to expand...
There is no direct correlation with an IEC earthing system. If there was, the earting diagram would look something like this...

Delta%20hghi%20leg%20earthing.gif
 
matthewmurphyj said:
Augie,

Thank you for clarifying that, I believe it is actually a TN system then. The neutral comes off of the transformer, into the facility, and is then bonded to the protective earth at the point of use.

Thank you for the help!
Click to expand...
Here in the US it would be bonded both at the utility transformer and at the service disconnect.
 
Status
Not open for further replies.
Top