Impedance Testing ,

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Fordean

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Xray supplier, Has requested the Z values are to be check at three separate points, What type of instrument/procedure should be followed. Job was designed and they informed us after the fact.


Have a 180 foot 4wire (4/0- # 4G) To Main 480 Volt Panel Fused at 200. Then to two different points for the xray unit..
There is no Transfromer. We are cannot To Bus Bar type assembly that travels up the Tower.



I will upload a photo if anyone requests.

Thank You
 

junkhound

Senior Member
Location
Renton, WA
Occupation
EE, power electronics specialty
2 channel scope is easiest
2 different known loads, take voltage and current and phase relationship, plus open circuit with small resistive load.

calculate impedance
 

Tony S

Senior Member
The OP was about the three readings required for Z.

Ze, Zs and Zpn are the ones I know of, are there others?

It would have helped if the OP had included the manufacturers required values and some detail.
 
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Fordean

Senior Member
Location
New Jersey
Occupation
Electrical Contractor
Load Values,

Load Values,

The OP was about the three readings required for Z.

Ze, Zs and Zpn are the ones I know of, are there others?

It would have helped if the OP had included the manufacturers required values and some detail.

Yes, There are 3 Required. I believe ZL, ZT, ? I will upload drawings. ZT is at Trans, ZL may be Load, and third was at disconnect means I think, I will load more data. Since I am getting good response here. My reason on posting, IS the Xray company Stated it WILL NOT hook up if values aren't within specs. This job went thru many levels before the go ahead, And I am not sure if the Engineer even had these values, ( Since we were given at the Job meeting). But bid job without them, Because we were never given those 3 sheets.
 
I would like to see your project photos.

Thank you


Xray supplier, Has requested the Z values are to be check at three separate points, What type of instrument/procedure should be followed. Job was designed and they informed us after the fact.


Have a 180 foot 4wire (4/0- # 4G) To Main 480 Volt Panel Fused at 200. Then to two different points for the xray unit..
There is no Transfromer. We are cannot To Bus Bar type assembly that travels up the Tower.



I will upload a photo if anyone requests.

Thank You
 

Tony S

Senior Member
Yes, There are 3 Required. I believe ZL, ZT, ? I will upload drawings. ZT is at Trans, ZL may be Load, and third was at disconnect means I think, I will load more data. Since I am getting good response here. My reason on posting, IS the Xray company Stated it WILL NOT hook up if values aren't within specs. This job went thru many levels before the go ahead, And I am not sure if the Engineer even had these values, ( Since we were given at the Job meeting). But bid job without them, Because we were never given those 3 sheets.


I will reply this evening (its mid day here). It will be easer if I knock a quick drawing together as the terminology we use is different to you. A pictures worth a 1000 words as they say. The principal is the same where ever we are.
 

Tony S

Senior Member
Sorry this has taken so long. I?m supposed to be retired and have been on the damn phone for 3 hours with everyone else?s problems.

You will need to beg, borrow, steal or even hire a loop impedance tester. The meter I listed earlier has it built in but thinking about it I?m not sure how it would cope with your crazy systems.

Until I sat down to do this drawing I hadn?t thought of the extra tests a three wire system involves.

TP1/5 will give the supply impedance, from this you can calculate your Maximum Prospective Fault Current. TP6/10 will give you the impedance at the load and again the MPFC. Along with the integrity of the GEC by giving it an actual value, this is what the X-Ray equipment manufacturers will be concerned with.

These are standard tests for a UK domestic installation, commercial/industrial it gets worse.

Loop%20Am_zpsipqhyxic.jpg
 
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