15 KV cap bank

[cornbread]

Question, I'm writing a SOP to lock out a arc furnace and we have a 15 KV cap bank associated with it. Ths SOP calls for the caps to be discharged. The cap bank has a shorting switch that connect the bank to ground to discharge the caps. We are debating if a visual inspection of the stabs making a grounded connection is adequate or should we have the electricans use a high voltage DC meter to measure for any charge.

My personal opinion is to test the circuit with a meter, but the electrical folks are resisting as checking with a meter would require PPE and typically the area is over 100 deg F.

I would appreciate your thoughts or comments.

 

[weressl]

Question, I'm writing a SOP to lock out a arc furnace and we have a 15 KV cap bank associated with it. Ths SOP calls for the caps to be discharged. The cap bank has a shorting switch that connect the bank to ground to discharge the caps. We are debating if a visual inspection of the stabs making a grounded connection is adequate or should we have the electricans use a high voltage DC meter to measure for any charge.

My personal opinion is to test the circuit with a meter, but the electrical folks are resisting as checking with a meter would require PPE and typically the area is over 100 deg F.

I would appreciate your thoughts or comments.

TBT=Test Before Touch is one of the cardinal rules of electrical work. Even if you can verify each and every phase conductors path to the ground, you would not know if the caps actually discharging to the ground.

Ask them how hot is it going to be in the coffin and will they care?

 

[cornbread]

Appreciate the reply....I thought I testing would be correct thing to do.

 

[MaysteelTrinetics]

Question, I'm writing a SOP to lock out a arc furnace and we have a 15 KV cap bank associated with it. Ths SOP calls for the caps to be discharged. The cap bank has a shorting switch that connect the bank to ground to discharge the caps. We are debating if a visual inspection of the stabs making a grounded connection is adequate or should we have the electricans use a high voltage DC meter to measure for any charge.

My personal opinion is to test the circuit with a meter, but the electrical folks are resisting as checking with a meter would require PPE and typically the area is over 100 deg F.

I would appreciate your thoughts or comments.

Which manufacturer built the caps, and what are the specifics on them?

The vast majority of Medium-Voltage capacitors used in the United States incorporate internal bleed resistors that will discharge the caps to a safe voltage level within 5 minutes. The grounding switch is an extra safety mechanism that is not commonly required for MV Cap Banks.

That said, any electrical worker who isn't concerned about checking the circuit directly prior to starting work is violating a number of standard practices, regardless of the PPE issues. Given that you "probably" have bleeder resistors and that your grounding switch "probably" works correctly, the likelihood of a cap retaining a hazardous charge is slim. However, if I were in your position, I would question whether "probably" is acceptable when the result of a one-in-a-million failure mode is potentially so severe.