Substation Gantry Jumper drop down 1

KillBill7 · Mar 24, 2020

Hi Guys

What are the thoughts on maximum drop of the jumpers without the post insulator support. Please see the attached sketch, I am contemplating between these two option, both options would required approximately 5m vertical drop. So couple of questions:

1) What is the max drop you guys have used in your design without the jumper support (Conductor is 795 Drake ACSR and its 138kV system)?
2) From the two options in the sketch which one would you consider as a better design. Option 1 will be more cost effective, whereas I think operation guys will prefer Option 2 due to accessibility to the arrester.

cuky2000 · Mar 25, 2020

I vote for Option 1 since it will require less steel and labor.

Here is a couple of suggestions that may further enhance your design:
_{1) Explore the use of a polymer housing surge arresters installed underhung (or upside down) mounting on top of the gantry. That will simplify the design and save material and labor.

2) See if you can use an H-frame gantry instead of an A-frame. That will save space, steel, and the number of foundations.}

For reference see the following Link

prc · Mar 25, 2020

I will select Option 2. Jumper can swing due to wind and also during fault current flow exerting forces on the equipment terminal ( surge arrester or transformer bushing).Please see Substation vertical dropper swing angle under wind blow
thread238-440626

stevenal · Mar 25, 2020

Seismically, option 1 looks better. If the arrester is on the A-frame, it's too far away from the insulation it needs to protect (the transformer).

cuky2000 · Mar 25, 2020

We never have a failure for this arrangement. Clearance in the gantry is selected to avoid any flashover for the most severe wind swing expected on the site.

Perhaps one of the reasons we do not have an issue is that we do not connect transformer directly from the gantry. Instead, we connect first to a disconnect switch and circuit breaker before reach the transformer.

KillBill7 · Mar 25, 2020

Thanks for the suggestions. Do you guys see any concerns with 5m conductor drop, which would be same for both options?

cuky2000 · Mar 25, 2020

Should not be a problem assuming that the gantry phase-to-phase and phase-to-ground distances are at least 12.0'(3.66m) and 4.3'(1.32m) respectively, should not be any problems for wind speed up t0 90mi/hr (145 km/h).

For general references, see a typical design guide below.

bacon4life · Mar 25, 2020

When I looked at supporting 7m of pipe bus by a 115 kV bushing, switch, or surge arrestor, the short circuit forces exceeded the equipment ratings. Perhaps the short circuit forces on cable are less than pipe bus? I have certainly seen long runs of flexible conductor.

We had an underhung arrest fail many years ago, and one theory about the cause of the failure was that excessive mechanical strain may have opened a gap and allowed water to penetrate between the base and the polymer housing.

Eng-Tips is the largest engineering community on the Internet

Intelligent Work Forums for Engineering Professionals

Substation Gantry Jumper drop down 1

KillBill7

Electrical

Recommended for you

cuky2000

Electrical

prc

Electrical

stevenal

Electrical

cuky2000

Electrical

KillBill7

Electrical

cuky2000

Electrical

bacon4life

Electrical

Similar threads

Part and Inventory Search

Sponsor