How to do Troubleshooting on Phase Failure ?

[Anthony Mak]

I met with the following case and get stuck on how to troubleshoot and repair the following problem:-

• The location is a town house in a complex, with a 3 phase supply. The client has been living in this premises for 20 years. Recently ( 9 months ago) they have renovated the house and have already moved back for about 5 months.
• Initially the power was normal, but approx. a month's ago, some outlets and lights were not on, and after checking by a qualified electrician, it was found one of the Incoming Line is not powered, which means One of the phase voltage is zero.
• Checked on the Electrical Room of the Town House Complex, all the 3 Incoming lines from the BC Hydro Breaker of this unit is normal; but at the Main Panel of the Unit, the Middle Phase Line voltage is zero; the other two lines are normal.
• Checked at the Electrical Room, there is a Large Teck Cable ( 100A) outgoing from the electrical room, going through the concrete slab, and get into the main panel of the house. There is no construction work and the concrete slab does not seems to have any broken point or damage. This means the possibility of the incoming line damaged and broken in between the electrical room to the house is very very minimal.
• It looks like right now one of the line cable is broken in between and so the solution is to replace the incoming cable or wire a new incoming cable from the electrical room to the Main Panel of the house.
• Is there any tests that I can do to troubleshoot the problem and fix it without rewiring ?
• Already checked the house and there is no other junction box or fuse box in between the Electrical Room and the Main Panel Box.

Your advices and recommendations will be very much appreciated.

Anthony

 

[Lucien Nunes]

It is unusual for one conductor of a larger cable to be completely severed while the others remain intact.
Has the continuity been tested at the actual conductors of the cable, rather than the terminals / lugs to which they are connected which might have a film of corrosion that has progressed and broken the connection.
Is the cable copper or aluminum?
Has the insulation resistance of the cable been tested? Low insulation on the unbroken cores would be further evidence of physical damage.

If the conductor is confirmed to be broken, it might be possible to locate the damage using a TDR instrument which measures the transit time of an impulse from the end of the cable to any anomaly. Whether it is helpful to know the location is moot if the cable is embedded in the slab anyway.

 

[Pete999]

I met with the following case and get stuck on how to troubleshoot and repair the following problem:-

• The location is a town house in a complex, with a 3 phase supply. The client has been living in this premises for 20 years. Recently ( 9 months ago) they have renovated the house and have already moved back for about 5 months.
• Initially the power was normal, but approx. a month's ago, some outlets and lights were not on, and after checking by a qualified electrician, it was found one of the Incoming Line is not powered, which means One of the phase voltage is zero.
• Checked on the Electrical Room of the Town House Complex, all the 3 Incoming lines from the BC Hydro Breaker of this unit is normal; but at the Main Panel of the Unit, the Middle Phase Line voltage is zero; the other two lines are normal.
• Checked at the Electrical Room, there is a Large Teck Cable ( 100A) outgoing from the electrical room, going through the concrete slab, and get into the main panel of the house. There is no construction work and the concrete slab does not seems to have any broken point or damage. This means the possibility of the incoming line damaged and broken in between the electrical room to the house is very very minimal.
• It looks like right now one of the line cable is broken in between and so the solution is to replace the incoming cable or wire a new incoming cable from the electrical room to the Main Panel of the house.
• Is there any tests that I can do to troubleshoot the problem and fix it without rewiring ?
• Already checked the house and there is no other junction box or fuse box in between the Electrical Room and the Main Panel Box.

Your advices and recommendations will be very much appreciated.

Anthony

Most likely a fuse gone OC at the feeder pillar

 

[Anthony Mak]

It is unusual for one conductor of a larger cable to be completely severed while the others remain intact.
Has the continuity been tested at the actual conductors of the cable, rather than the terminals / lugs to which they are connected which might have a film of corrosion that has progressed and broken the connection.
Is the cable copper or aluminum?
Has the insulation resistance of the cable been tested? Low insulation on the unbroken cores would be further evidence of physical damage.

If the conductor is confirmed to be broken, it might be possible to locate the damage using a TDR instrument which measures the transit time of an impulse from the end of the cable to any anomaly. Whether it is helpful to know the location is moot if the cable is embedded in the slab anyway.

Thanks for your comments. We did tested the cable and cleaned the contacts. These are copper cables. It is unbelievable that such a big cable can be broken in between ( with only one cable broken inside).

 

[Anthony Mak]

Most likely a fuse gone OC at the feeder pillar

I have checked the Incoming from BC Hydro and there is only a breaker and the Power Meter, No other Fuse Box

 

[Pete999]

I have checked the Incoming from BC Hydro and there is only a breaker and the Power Meter, No other Fuse Box

Looks like a DNO problem then