C84, Annex A: Secondary Grounding Illustrations

The following Images demonstrate common Utility Transformer Secondary side Grounding techniques, for 1Ø and 3Ø Systems.
Images reflect what would be found in "C84, Annex A3"



Fig. 1: Single Phase Systems

"(i)" = 1Ø 2 Wire, Grounded "End" configuration:

This is a Single (secondary) Coil with no "Center Tap", which results in a single voltage single phase 2 wire output.
This image denotes the System's Secondary side is Grounded at the "Lower End" of the Coil, which results in the Conductor at the "Lower End" to be the Grounded Conductor.

"(ii-a)" = 1Ø 3 Wire, Center Tap Grounded configuration:

This is a Single (secondary) coil with a "Center Tap", which results in a "Dual Voltage" - or single phase 3 wire output.
This image denotes the System's secondary side is Grounded at the "Center Tap" of the Coil, and there is a Conductor brought out from the Center Tap - this is the System's "Neutral" Conductor, and it is the Grounded Conductor in this example.

"(ii-b)" = 3 Wire, "Open Wye" configuration:

This is a Multi (Secondary) Coil arrangement, connected in an "Open Wye" configuration, with the "Common Points" of the Coils being Grounded.
No Grounded Conductor in this example.

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Fig. 2: Three Phase Three Wire Systems

***NOTE***
These (4) examples DO NOT have a Grounded Conductor on the Secondary side

"(iii)" = 3Ø 3 Wire, Wye configuration:

This 3 wire Wye has no Grounded Conductor, it is only Grounded at the Transformer(s) - at the "Common Connection Point" of the 3 secondary Coils.

"(iv)" = 3Ø 3 Wire, "Tee" configuration (Open Delta "Tee"):

This Grounded AC System is an Open Delta "Tee", grounded at the "50% Tap" of the "Main Coil", along with the "Kicker Coil" being connected at the same tap point.
System also does not have a Grounded Conductor in this example.

"(v)" = 3Ø 3 Wire, Delta configuration ("Full" or "Closed" Delta):

This is a Configuration which uses 3 Transformers/Coils, to form a "Closed" Delta.
System's Secondary is Grounded via "Center Tap" on one Winding (Coil).
System does not have a Grounded Conductor in this example.

"(vi)" = 3Ø 3 Wire, Delta configuration (Open Delta "Vee"):

Same Grounding data as "(v)" above, only this setup uses 2 Transformers/Coils, to form an Open Delta "Vee" (one "side" is left "open").

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Fig. 3: Three Phase Four Wire Systems

"(vii)" = 3Ø 4 Wire, Wye configuration:

This is the "Typical", commonly used 4 Wire Wye configuration, which is Grounded at the "Common Connection Points" of the 3 Secondary Coils.
To achive a Dual Voltage Output (via a Common Conductor), a Conductor is terminated at the same "Common Point", and this 4th Conductor becomes the System's Grounded Conductor in this example.

"(viii)" = 3Ø 4 Wire, "Tee" configuration (Open Delta "Tee"):

This arrangement is similar to the Open Delta "Tee" setup shown in the "3Ø 3 Wire" examples, only this setup has a Grounded Neutral Conductor, and allows for a Dual Voltage output.

"(ix)" = 3Ø 4 Wire, Delta configuration ("Full" or "Closed" Delta):

Similar to the 3Ø 3 Wire Closed Delta example shown above (centermost schematics frame), this setup taps a Conductor at the Center Tap point, and the system is grounded at the same tap point.
This results in a Dual Voltage system with a Grounded Conductor (from the Center Tap point)

"(x)" = 3Ø 4 Wire, Delta configuration (Open Delta "Vee"):

Similar to the 4 Wire "Closed Delta" counterpart above, this setup uses only 2 Transformers/Coils, which results in an Open Delta "Vee" arrangement.

Any questions or comments??? Feel free to create a new thread in one of the open forums.

Scott35

05.12.2005

...end.

edited to correct text

[This message has been edited by Scott35 (edited 05-12-2005).]
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Scott " 35 " Thompson
Just Say NO To Green Eggs And Ham!