Disconnect Procedure - Comments Please

[busman]

Linemen,

Most of my work in the past has been 4160V with a little 13.2 kV. Anyway, the new system I'm being asked to tackle is 35kV and for obvious reasons, I want to get this right. There is no intention for any of us sparkies to work on any live MV parts, but we need a switching procedure to place the switchgear in an electrically safe condition. The substation in the following is privately owned with primary metering by the PoCo, so they don't do the switching. The setup:

35kV is provided by the PoCo at the substation to a GOAB that serves an underground feeder of about 1000' length.
At the end of the feeder is a Sectionalizing Cabinet that has 4 bushings on each phase. The bushings are for:

1) Incoming feeder
2) Surge Suppressor
3) Outgoing feeder to Switchgear #1 and Transformer #1
4) Outgoing feeder to Switchgear #2 and Transformer #2

The following is the planned switching procedure:

1. Remove all loads from the power system and open all LV circuit breakers in the MDP.
2. Install Ground Grid mat and ground to substation structure. Using Class 2 gloves and protectors and standing on the grounded grid, open the Gang Operated Air-Break Switch (GOAB) at the substation.
3. Visually verify that all three blades of the GOAB have opened and are clear. If blades cannot be verified to be open, DO NOT PROCEED.
4. Install LOTO on the GOAB operating handle.
5. Open the Sectionalizing Cabinet at the pad site.
6. Using a Hot-Line Tool (HLT), open the test ports on each of the three 35kV elbows.
7. Using a line voltage tester on a HLT, test for voltage at each of the three test ports. If voltage is indicated, DO NOT PROCEED.
8. Using a HLT, remove each of the feeder elbows (line side) from the bushing and place securely on the grounded parking stand.
9. Using a HLT, secure ground clamp of three-phase URD grounding set to ground cable in the Sectionalizing Cabinet.
10. Using a HLT, install each of the three grounding elbows of the three-phase URD grounding set to the bushings.
11. Close and LOTO the Sectionalizing Cabinet.

Comments welcome and encouraged. And, as always, thanks for your time.

Mark

[Lineman North Florida]

If this is a radial run and has no way to be loop fed I see no problems with your switching order.

[busman]

If this is a radial run and has no way to be loop fed I see no problems with your switching order.

LNF,

Thanks for the comment. Yes. This is radial. It is a dedicated supply to an experimental system (no residences or businesses). I should have mentioned that. It's also relevant because this system is only going to be used on an intermittent basis and it is not an issue to have long dedicated outages to perform work on the switchgear.

Also should have mentioned that the reconnect will be the reverse procedure.

Also, I specified Class 2 gloves for the GOAB only because that is the highest voltage the sparkies will have. There has been previous debate about using gloves for this type of switching here in the past, but I feel that even with grounding, you could have a few hundred volts of potential drop and gloves are an extra layer of protection that won't interfere with this operation.

Thanks again,

Mark

[Rob]

Agreed. Looks OK