Cable Core Identifier

[Dave C]

I need a Cable Core Identifier to establish the phase rotation in an un-energised three phase H.V. Cable. prior to jointing. My thoughts were by using three coloured LEDs to confirm correct connection.

I recall seeing a circuit back in the 80's - 90's where three LED's were used in a transmitter that had three leads that connected to the cable at one end and a reciever was connected to the other end by three leads. The leads were swapped until all LED's were lit.

All that I can find on the internet is a instrument that is already built and for sale, but not a circuit.

Can anybody help with the design of a circuit.

Regards

 

[DaveC2]

Is this a Delta or Y 3 phase power source?

 

[Musicmanager]

Hi

In the good old days .. .. LOL

1. Mark cores at one end 1,2 & 3 or A,B & C then ..

Link 1 & 2 or A & B together.

2. Look for continuity at other end and mark linked pair.

3. Return to other end and join 2 & 3 or B & C

4. Look for continuity at other end again – one of them will be marked and that is 2 or B – mark as 2 or B

5. Return to other end and join 1 & 2 or A & B

6. Look for continuity again, one will be marked 2 or B, the other is 1 or A

7. Remaining tail will be 3 or C


Simples !

S

 

[dr pepper]

I put together a fox/hound circuit, but it just does 1 channel, instead of just having a probe on the detector I put a plug in inductor on it, this is good for finding a short on a cable run as it detetcs the magnetic field.

I have a commercial identifier, I thought of building one prior to having to buy one, most multimeters these days have a frequency counter built in, if you assembled a 4060 and a xtal circuit you'd have multiple freq o/p's, each one dropping half the freq, these connected to a mutlicore cable would be easily detectaable at the other end, just start with the lowest freq and go up in doubles freq wise.

 

[Reloadron]

Hi

In the good old days .. .. LOL

1. Mark cores at one end 1,2 & 3 or A,B & C then ..

Link 1 & 2 or A & B together.

2. Look for continuity at other end and mark linked pair.

3. Return to other end and join 2 & 3 or B & C

4. Look for continuity at other end again – one of them will be marked and that is 2 or B – mark as 2 or B

5. Return to other end and join 1 & 2 or A & B

6. Look for continuity again, one will be marked 2 or B, the other is 1 or A

7. Remaining tail will be 3 or C


Simples !

S

Absolutely! Taught that to my technicians and it served me for over 40 years. Process of elimination! Now if you want a box that does that just build it around the above description.

Ron

 

[DaveC2]

{}--------------------------- traveler-------------|{}--------------+27VDC
| |
Rled Rled
4.7K 4.7K 9VDC battery
'--------------------, |
{}----------------------------traveler ------------|{}--------------+18VDC
| | |
Yled | Yled
4.7K 18V zener 4.7K 9VDC battery
'-----------, | |
{}----------------------------traveler ------------|{}--------------+9VDC
| | | |
Gled | | Gled
4.7K 9V zener | 4.7K 9VDC battery
| | | |
{}----------'---------'-------------------------- Grd{} ---------bare wire or metal conduit

My post does not look correct and editing it won't change it...just envision the batteries and the leds in series on the right side and the leds and the zeners are in series to ground on the left.

Maybe this arrangement would do what he's thinking about...if the traveler wires are hooked up correctly at the opposite end,
wouldn't the leds light up indicating the same order at the originating end? Observer polarity of the leds and zeners!
Or just measure the voltage from Grd and mark with tape.
Just use alligator clips {} for the attachment at both ends.

 

[KeepItSimpleStupid]

Dave:

I think I have an idea how to make one:

1. On the transmit side use a DTMF transmitter and for smplicity's sake, use same analog switches to sequentially transmit
DTMF 1 on A & B
the DTMF 2 on B & C and
DTMF 3 on C&A

Now on the receiver side, use three DTMF receivers and look for
DTMF 1 between A & B; i.e. light a LED

etc.

You could do it as fast as the circuit allows or let it be three sequential lights.

See Holtek for some parts ideas.

The transmit side would use an single ended in differential out instrumentation amplifier.

 

[DaveC2]

Wouldn't hooking up 3 - 9volt batteries in series and clipping them to one side and measuring the opposite end with a voltmeter be simpler? You'd use the bare wire/ground/conduit as the 4th if it is delta configuration.

 

[KeepItSimpleStupid]

Per post #6. Who says you need a ground? Use a two resistors and a constant current source. Say 6 and 3 volts.

Then, one or more selector switches on the end. In the firs case your trying to find two wires with +6 between them and then a confirm for the last

 

[DaveC2]

You're right 3 phase doesn't necessarily have a ground if placed in a non-conductive conduit but then again, the equipment might want one so a 4th wire might go into it too. If that wire is the ground or zero potential of the battery combination, then measuring from that wire would definitely identify all three other wires and confirm continuity too. It just seems easier to use 9VDC batteries instead of finding constant current sources.

 

[KeepItSimpleStupid]

TI and Linear make 2 terminal current sources.

 

[KeepItSimpleStupid]

With a ground or reference, suppose you had 3, 6 and 12 Volts. Then it's easy. Use a voltmeter as the receiver.

No ground or reference, it gets a bit harder.
Suppose you had 3 V, and 9

So you look for the wires with a 3V positive difference and confirm the 9V one.
i.e.
AtoB has 3V
A to C has 9.
A(0),,,,,,,,,,B(3),,,,,,,,C(9)

bad example number wise, but you can't mistake the reference in this case.

Voltage like 1, and 5 with a 9V supply and a constant current source,

 

[KeepItSimpleStupid]

RE: Post #10

You don't want the voltages between two pairs equal.

In the previous post, once you find the wires with the positive one volt between them, your home free. If you happen to find -1 between them, reverse them.

 

[DaveC2]

That why I like the idea of using a zero voltage wire...everything is positive from it and there's no mistaking 9, 18, & 27 V ...batteries like that are everywhere and battery clips are in all kinds of defective devices for the taking. IMHO, DaveC2

 

[KeepItSimpleStupid]

The LT part LT3092 https://www.linear.com/product/LT3092 and the TI LM334 https://www.google.com/url?sa=t&rct...2I1OLMSDSuB2IOTaAgSUFoQ&bvm=bv.86475890,d.cWc are easy to come by.

You only need one,say set for 0.5 mA, One battery and a few resistors. Possibly put a low power LED on the xmitter.

Uneven voltages make finding the correct sequence much much easier. You could easily make it work for 4-wire systems.

Say 1 V, 1.5 V and 4 V, so a 6 .5V drop total.

Take any two and you get a unique voltage, so you effectively KNOW which wires you have with one measurement.

Assume 3 wires and a reference (ABCD) for the moment, If you measure 2.5 V, you have the top two wires or C&D. If you measure -2.5 V, you have C&D reversed.

Measure -0.5V, (on the other two wires) which wires do you have?

So with just TWO voltage measurements, you have the sequence.

 

[Brevor]

If you are talking about identifying wires in a bundle I have a circuit I built sometime back that does this. It uses a remote box that contains 9 resistors, 11 leads with alligator clips come out of the box. One is labeled common and the others are labeled 0 through 9. A common wire is needed between the ends of the wire run, the common lead on the remote box and on the readout box connect together through this wire. When the input lead on the readout box is connected to each wire in the bundle a 7 seg. display shows the lead number it connects to at the remote unit.