Grounding through a switch 1

[EASTON23]

What does it mean to ground through a switch?

 

[crshears]

Here's what it means at the utility where I am employed as a Power System Operator:

_________ / __________
. . bus A . . . .bus B . . .


Work to be done on bus A

Either there's no handy spot for the tradespeople to apply working grounds or there are no permanently installed grounding devices on it

Bus B either DOES have a handy spot for the tradespeople to apply working grounds or has permanently installed grounding devices on it

[1] Remove both the A and B busses from all sources of potential and lock out / tag out

[2] Close or check closed the intervening switch and lock out / tag out in the closed position

[3] Either

​

[a] close permanently installed grounding devices on bus B and issue Work Protection on bus A with intervening switch guaranteed closed for grounding continuity, or

​

issue Work Protection with intervening switch guaranteed closed for grounding continuity, making the requirement for the trades people to apply working grounds a condition of issuance, with this listed in the safety precautions and instructions of the Work Protection


CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[dpc]

Not enough information. Grounding switches are actually a thing, or it could be a temporary switching arrangement as noted by crshears. Some additional context would be helpful.

 

[crshears]

Hey dpc, I took "grounding THROUGH a switch" [uppercase mine] at face value, hence my response.

That being said, I take your point; for sure I've grounded WITH a [grounding] switch plenty of times, and I've also grounded through a breaker, which I can explain if there's enough interest.

Circumstances, circumstances . . . in other words, "it depends."

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[EASTON23]

What I meant was, in a substation. What does it mean to ground through a switch? Hanging ppg through a disconnect switch.

 

[crshears]

Hey Easton, if I'm understanding your question correctly, I believe my description is the right one; the method I described is quite routine and taken as a matter of course whenever applicable. Where trades groups apply for Issued Work Protection ["Operator Administered" in the old lingo] and are not planning to apply Self-Administered Work Protection, any requirement to have switches closed for grounding continuity must be specified by the applicant on their paperwork.

Incidentally, there's no reason why the same rationale cannot be applied to transmission circuits.

[PPG-personal protective grounds?]

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[che12345]

Dear Mr EASTON23

Q. What does it mean to ground through a switch(in a substation)?
A. In the IEC land, earth=ground in NEC. Therefore, "to ground through a switch" is equal to "to earth through a switch" i.e. connecting the part the incoming or the busbar to earth, by an [earthing switch].
This is practiced in LV, MV and HV. The purpose is to discharge the part and maintaining it at zero potential to ensure safety, while the man is at work.

FYI: Earthing switches are mechanical switching devices (i.e. it [do not open] when switched on to a fault accidentally ) for earthing and short-circuiting circuits. They are capable of carrying currents for a specific time under abnormal conditions , but are not required to carry normal operating currents.

Che Kuan Yau (Singapore)

 

[davidbeach]

I think I understand the question the same as crshears did. Our practices would generally not allow grounding through a switch. The exception is in GIS installations. Otherwise our policies don’t provide for the tagging of a closed switch. Find a way of hanging grounds on the work side of the switch.

 

[tinfoil]

We would allow grounding through a switch as long as the CLOSED state of that switch is guaranteed in the permit (motor decoupled if motorized, etc), and one can visually confirm continuity from the permitted zone to the actual grounded point(s).

For this reason, we would not normally accept a breaker or circuit switcher to 'ground through' on an overhead system/station.

 

[cuky2000]

Ground switches can be furnished for single pole or group operated applications to provide grounding for inspection, maintenance, repair, or replacement of other substation equipment such as capacitor banks, circuit breakers, circuit switchers, etc.

It is interesting to observe that still today many utilities using a fast grounding switch (called fault-initiating switches) to create a short circuit and protect circuits.

Below are some of the application for grounding switch.

 

[crshears]

Tinfoil wrote: we would not normally accept a breaker or circuit switcher to 'ground through' on an overhead system/station.

Very true; the procedure I described stipulates that use of the "grounding through a switch" procedure is only allowed in cases where a galvanic connection through the device can be visually confirmed. This therefore precludes the presence of a circuit breaker, a circuit switcher with "targets," or any other such device in the series grounding continuity path.

Previous to very recently, the position of all of our SF6 switchgear could be visually confirmed either by eye and flashlight through viewing ports, periscopes with prisms [long since retired from active service but still available as back-ups], or, more recently, by means of closed circuit battery powered cameras and LCD screens mounted on lightweight poles.

At our very latest SF6 station however individual cameras have been mounted for each in-line or ground switch and comm bundled to one central viewing station; we controllers are not happy about it, but we've been overruled.

Incidentally, due entirely to my poor description, I may have implied that we do in fact sometimes depend on ground paths through breakers, but that is not the case; what I meant by "grounding through a breaker" is a specific procedure for either the application to, or removal of working grounds from, high voltage circuits in corridors with a high degree of induced circulating current where specialized grounding switches as described by cuky2000 have either not been installed or are unavailable.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[che12345]

Hi friends
The inquiry raised by Mr EASTON23 on 5 Mar 2019 at 2305h was
Q. "What does [it mean] to ground through a switch (in a substation)?"
A. My answer dated 6 Mar 19 08:48 was ...It means " ....to earth through a switch i.e. connecting the part the incoming or the busbar to earth, by an [earthing switch]".

Any other additional information though important, are [irrelevant] to the question asked.
Che Kuan Yau (Singapore)

 

[davidbeach]

Except that’s not correct. Grounding through a switch - having a closed switch between where a ground is required and where the ground is applied - is very different than closing a ground switch.

 

[crshears]

I wrote: "... "grounding THROUGH a switch" [uppercase mine] at face value, hence my response. That being said, I take your point; for sure I've grounded WITH a [grounding] switch plenty of times..."

Perhaps it is one of the downfalls of the English language, but unfortunately the OP was phrased with a nuance that may not be readily apparent, and it is to that nuanced question that I responded. I therefore submit, with all due respect to my much more learned colleagues, that my response was not irrelevant.

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]

 

[davidbeach]

Not only not irrelevant, but more correct than the post that called it irrelevant. Through and with are not the same.

 

[Coco_HueHueHue]

I have seen grounding switch in a lot of utilities. Cuky2000 has good examples.
I have also seen some to ground capacitor banks when they are de-energized and you want to work on them.

It can also be a good idea to set an interlock between this switch and the breaker feeding. This way, you cannot close the switch if the breaker feeding is not open.

By the way, NEC and Canadian Electrical Code stipulates that public utilities are not covered by the code. So I don't know if you can use those switches in any industrial applications, but i have seen them a lot on public utilities though.

 

[LionelHutz]

che12345 - "Ground through a switch" is vague. It could be interpreted either way it's been discussed in the thread. So, it is completely wrong to be dismissive about the answers discussing "grounding through a switch" as meaning the switch is between 2 circuits. All parties have interpreted it to mean "to earth through a switch", but it's certainly not worded well enough to mean the switch must be a grounding type switch.

Myself, I would tend towards it meaning the switch is between 2 circuits and not towards it meaning a grounding switch. If I was describing applying a safely ground via a ground switch I would write something like "grounded by the grounding switch" or "grounded with the grounding switch" or "by closing the grounding switch".

Besides, the responders interpreting it as being a switch between 2 circuits outnumber the ground switch responders 3 to 2.

 

[cuky2000]

Below is one application "Ground through a switch" a phase conductor. This is an old protection scheme still used by several utilities.

 

[RRaghunath]

Easton 23,
If my understanding s correct, you are talking of portable ground.
As we know when portable ground is applied there will be momentary arcing due to capacitive charge.
If we have a portable ground with a switch, the arcing is avoided as the switch is open.
After applying the ground, the switch is closed and since the switch is enclosed, the arc is contained inside.
This makes the process safer for the technician.

 

[crshears]

davidbeach wrote: I think I understand the question the same as crshears did. Our practices would generally not allow grounding through a switch. The exception is in GIS installations. Otherwise our policies don’t provide for the tagging of a closed switch.

Here's the part of our Utility Work Protection Code that prescribes our practice in these situations:


When there is an intervening device

IF: de-energizing of any equipment is dependent upon the position of a device which is located between the equipment and a guaranteed, permanently installed de-energizing device,
THEN: the position of the intervening device must be guaranteed in the proper position in order to provide continuity of de-energization.

and

De-energizing with temporary devices

IF permanently installed devices do not provide the de-energizing condition required,
THEN the Holder must:
• ensure the necessary additional de-energizing operations have been performed once the Work Permit is issued/accepted, and
• before work commences.
The Holder must do the following when de-energizing with temporary devices:
• Select a qualified person to perform the necessary de-energizing operations if the Holder is not qualified to perform these operations.
• Make temporary de-energizing device(s) highly visible using an orange conductor jacket, a marker or a flag. This will ensure the temporary de-energizing devices are not overlooked.
• Record the number of temporary de-energizing devices on the Work Permit form or tag.
• The intent of this rule is to record the number of grounds in use, not the current status of the grounds.
• This will help to ensure all temporary de-energizing devices are removed on completion of the work.
Responsibility:
Maintaining the record of the temporary de-energizing devices in use is the responsibility of the Holder(s) who requires the devices.

Purpose: the purpose of a De-energizing Device (PC4) tag is to identify the person or work group relying on a temporary de-energizing device. Never use De-energizing Device tags in place of a Work Permit.

De-energizing Device tags required

In line locations, each work group relying on the same temporary de-energizing device(s) must place separate De-energizing Device tags.
In station locations, each work group must identify their temporary de-energizing devices with a De-energizing Device tag.
[highlight #FCE94F]• IF de-energizing of any equipment in a station is dependent upon the position of a device which is located between the equipment and a temporary de-energizing device,
• THEN the intervening device must be tagged in the appropriate position with a De-energizing Device tag.

Notice
This Work Protection Code was prepared for the internal use of my company and its subsidiaries.
Neither my company, its subsidiaries, or any person acting on behalf of any one of the foregoing,
(a) makes any warranty, express or implied, with respect to the use of any information, equipment, method or process disclosed in the Work Protection Code or that such use may not infringe privately owned rights; or
(b) assumes any liabilities with respect to the use of, or for damages resulting from the use of, any information, equipment, method or process disclosed in this Work Protection Code.
[/highlight]

CR

"As iron sharpens iron, so one person sharpens another." [Proverbs 27:17, NIV]