Floating delta ground fault location 1

[oldfieldguy]

Some of my stations still have floating delta 480 volt systems. Last week I drove a thousand miles round trip to help a station I&E (more "I" than "E") technician locate a ground fault.

I hate to resort to the "turn off one circuit at a time and see when it goes away" method of fault location. Installing a grounding transformer is not in the cards right now due to budgetary considerations.

At one time I had access to a ground fault locator for delta systems. It basically took an ungrounded phase to ground through a resistor and a pulsing contactor so the fault could be located using a tong-type ammeter around all three phases of a branch circuit.

It's been too many years since I had my hands on that detector. Does anyone know of a manufacturer for that sort of set, or do I have to build one myself?

old field guy

 

[waross]

You can probably build it quicker than you can find it, oldfieldguy.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[trosepe]

http://www.i-gard.com/showPage.asp?id=7

I use the I-Guard 'Sleuth'. You can fault locate without interuption using a standard clamp-on ammeter.

 

[xxjohnh]

In China they are installing MV ungrounded systems and have developed a relay developed a system to detect faults.
Beaman would turn in his grave.
The system you describe is an old US method with a contactor that made the pulse through a 5 amp resistor. Powell may have something they could make up. If it was me I would contact

http://www.selinc.com/

they are the cutting edge on relaying these days, they have a relay they use on medium voltage and may have something for low voltage.

 

[slavag]

Hi oldfielfguy.
Try this:

http://www.bender.org/portable_ground_fault_location.aspx

Intresting, you remind me some very useble locator for the DC ungrounded systems. I try found some scheme.

Best Regards.
Slava

 

[oldfieldguy]

Slava--

Thanks! Now, does anybody have any experience with this unit? the old things I used in the past used 10-20 amps of detection current.

old field guy

 

[steamdog]

One question that bugs me here, with 1000 mile round trip, why not fly?

 

[oldfieldguy]

Steamdog--

Because by the time I got to the airport, got on a plane, flew through interconnecting stops to the closest airport to the destination, then rented a car and drove the the actual remote site, the time element would have been a wash.

In the cited case, I actually stopped by one of my other stations on the return trip, so I killed two birds with one stone.

I have a company car and a fuel card and a thousand miles of pipeline, 24 compressor stations including two offshore platforms (I fly to those)spread over four southern states. Natural gas pipelines are terribly inconveniently located.

It's a fun job! Kind of like a hobby with a paycheck.

old field guy

 

[steamdog]

Actually, I like driving, too. We are lucky in our area, being the Fisher rep we sell a lot of gas regs, but also being in the NYC metro area, there are not many miles to travel (but many hours in traffic!!)

 

[burnt2x]

Since you said 480V systems, the typical charging currents are around 1 - 2 amps. Basically depends on the length of the cables though.
Respectfully.

 

[oldfieldguy]

Steamdog--

The only thing I have that is close to a city is a station northwest of Houston. Twenty years ago it was out in the boondocks. Now suburbia has flooded in around it. Naturally the neighbors complaint loudly about the noise from our engines, no matter that the engines were there forty years before any of their houses. the rest of my stations are out in the countryside, bucolic park-like locations.

Twiceburnt--

That sounds like my system. One option I'm looking at going forward is a zig-zag grounding transformer, or maybe an wye/broken delta. I have to see what fits in our (non-existent) budget.

old field guy