Busbar 'ductor' testing

[Micksparky25]

Just been asked to carry out a busbar 'ductor' test on a new busbar installation , I understand it's a form of low resistance test checking the joints etc... But have'nt a clue how to test it ?! I know you use a 'ductor' tester but that's about it !

any tips or help would be much appreciated lads

 

[telectrix]

tony's your man here. or eng54.

 

[Micksparky25]

Great stuff cheers . How can I get hold of him ?

 

[telectrix]

remember that guiness ad. ? he waits and waits......... tony's usually on forum late ish.

 

[spark 68]

There are usually 4 leads with the ductor tester, this nulls out the resistance of the test leads, you will have to follow the instructions that come with the tester, some have two leads each with two prongs (giving a total of 4),and some come with 4 separate leads.

You will be measuring micro-ohms across the fishplates/connections, this is a high current test, usually you are given what current you should be testing at, ie. @ 100A etc.
Some testers also give the voltage drop reading on the display alongside the micro-ohm value, sometimes I have recorded this too.

Sometimes you are given tables with the expected micro-ohm values for a given size of copper bus-bar, and sometimes you are just making comparative tests.

The comparative test works by first selecting your 'control joint' , this is first checked by checking the bolts are correctly torqued up, and then the reading is taken at the selected current, this is your reference or ball park reading, and all other similar sized coppers and joints are compared to this reading, and they should be substantially the same/very similar (for the same sized coppers/connections). The leads should be kept the same distance apart for all subsequent tests. Remember you are measuring micro-ohms (0.00001 of an ohm)

I have just taken and recorded the readings before, and apparently the engineers compared this to known values in a spread sheet.

You really need more information on what type of test you are being expected to make.

Sometimes I have been instructed to take each reading three times and take an average, it all depends on the testing regime being implemented.

 

[Knobhead]

A Ductor injects high current and measures the volt drop between the test points. It gives the reading directly in µΏ.

1[SUP]st[/SUP] question, are there any joints in the busbars?
2[SUP]nd[/SUP] question are the risers from the busbars solid copper or cable?

The main point of a Ductor test on busbars is to find any high resistance joints. By high resistance a variance of a few µΏ should set alarm bells ringing. The main thing with busbars is to ensure the joints are torqued up correctly. I also found a slight smear of Vaseline on untined joints helps, tined joints should be dry. Vaseline dropped the temperature on a set of 4000A bars by 7°C.
As for the joint bolts, I use EN8.8 high tensile, do not use spring washers.

You don’t say what current is involved.

Drop me a PM.

 

[Engineer54]

Further to Tony's above post.... Read the instructions closely, incorrect positioning of testing probes or incorrect probe polarity will give totally inaccurate results. Ductor testing is generally now only done on new installations BEFORE being energised and put into service. Regular or ongoing testing during the installations lifetime, is now carried via thermal imaging cameras.


I use a Ductor test kit on all our Switchboards and MDB's during initial commissioning to check all bus bars joints and connections and ACB/GCB/VCB/MCCB's connections and breakers switch contact resistances. You always need to see a steady/stable reading on each test application. Any swinging or up and down reading displays indicates you have a problem, either in the joint your testing, or more commonly in human error in placing the probes correctly ...lol!!

Main point in conducting these tests is to be methodical in both approach and implementation, these units are very accurate and very small discrepancies can mean the difference between having a problem and not having a problem with the system you're testing!!

 

[Micksparky25]

Thanks lads , I'm still in the dark to what manufacturer of the busbar is etc as I'm not there to see it yet but it's brand new solid copper rising busbar , and yes not sure what ductor tester they will be supplying me so will have to see on that one , but wasn't sure if there was a general procedure ie testing between cores or linking them all out ?

cheers