How to conduct continuity test for cable sized 250 sq. mm?

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Discussion Overview

The discussion revolves around methods for conducting a continuity test on a 250 sq.mm cable, specifically in the context of identifying and verifying cable connections from a main circuit breaker to a concrete post. The scope includes practical testing techniques and safety considerations.

Discussion Character

  • Technical explanation
  • Debate/contested
  • Experimental/applied

Main Points Raised

  • One participant inquires about the suitability of using a digital or analog multi-tester for testing a 15-meter, 250 sq.mm cable, emphasizing the need for suggestions on the testing method.
  • Another participant suggests that a VOM (digital or analog) is adequate for continuity testing if the goal is to identify cables, but recommends more robust methods if there are concerns about cable integrity.
  • A participant explains the context of the testing, noting that the markings on the cables have been erased and that previous attempts to connect the cables resulted in a fuse cut-out tripping.
  • One participant proposes a method involving shorting pairs of conductors to identify groups of cables, suggesting that this could be a quick and effective approach.
  • Another participant shares an alternative method of connecting the cables to a voltage source and measuring the voltage on the other side to match the cables.

Areas of Agreement / Disagreement

Participants express varying opinions on the best method for conducting the continuity test, with some supporting the use of a multi-tester and others proposing different techniques. No consensus is reached on a single preferred method.

Contextual Notes

Participants mention the importance of safety and compliance with codes, especially given the high current involved. There are also references to the challenges posed by the lack of clear markings on the cables and the absence of the building's electrical engineer.

Who May Find This Useful

Electrical engineers, technicians involved in cable testing, and individuals interested in practical methods for identifying and verifying electrical connections may find this discussion relevant.

xiv_wolf
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Good day everyone!

I would like to ask if it's ok to use a digital or analog multi-tester in testing a 15 meters, 250 sq.mm cable? We are tracing buried cables from the main circuit breaker to the concrete post. We are connected to Delta X'mer, 230 V, 4 wire w/ ground System. The x'mer will not be connected to the system while testing. I've attached the schematic diagram of the proposed method of testing. I appreciate any suggestions/recommendations. Thank you very much.

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If the purpose of the continuity test is to verify which cable is which, then a VOM (digital or analog) will certainly do the job. If you have known, or suspect issues with the integrity of the cables then you should consider more robust testing methods suggested and approved by a certified engineer. 500kVA is a lot of current, and demands rigid compliance with codes and safety guidelines.

Fish
 
Thanks for the reply Fish4Fun! We're conducting continuity test to verify which cable is which so that the provider of x'mer can connect the correct cable for each phase. When the provider initially connects all the 4 wires of each phase, the fuse cut-out of the x'mer tripped off. We are instructed to determine the correct groupings of the cable because all of the markings have been erased. The Electrical Engineer of the building has passed away and the blue print that left is quietly old.
 
ok You have stated ALL power is disconnected!

so you don't have to extend the meter leads between the far ends of the cables.
At the top of the post end in the first group of 4 conductors strap a pair of them together
at the main panel board end look for a s/c between a pair of cables in that group
you can then use that to identify the other 2 cables of the group.
Once those 2 cables have been marked you can remove the short between the the initial 2 you shorted together and identify them individually using a short between one of them and one of the 2 marked cables.
10 minute job ... piece of cake :)

Dave
 
Dave's idea seems pretty good. We did that once.

You could also try connecting the cables to a voltage source one at one side and measure the voltage on the other side. Maybe use a car battery. Two wires one to + and other to -ve terminal of battery. Measure the voltage on the other side and you'll have a match.
 

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