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MODs in new substations

MODs in new substations

MODs in new substations

(OP)
Are MODs recommended or used in new substations? If so what advantages do they provide?

RE: MODs in new substations

Ministry of Defence? Perhaps a worthwhile security measure in substations around Middlesbrough: a pair of Challenger tanks might deter the cable thieves... winky smile


More seriously, it's best if TLA's are explained, especially in a multi-national forum where devices have different names in the NEMA/FM world compared to the IEC world.

RE: MODs in new substations

(OP)
TLA's?




EDIT: Motor Operated Disconnects

RE: MODs in new substations

Not Motor Operated Disconnects?

Do you use interlocks?

RE: MODs in new substations

In my neck of the woods, they are used all the time as 345 kV line disconnects. Controls are both in the control house and SCADA. In our region, I have not seen MOD's utilized for any other purpose in Air Insulated stations. I have seen MOD's applied extensively in Gas Insulated Switchgear around breakers and lines.

I believe the advantages are #1 safety (at higher voltages), #2 faster connecting / disconnecting and #3 System Operations can isolate lines, particularly for remote stations.

RE: MODs in new substations

(OP)
Motor Operated Disconnects, again, my mistake.

RE: MODs in new substations

At 115 kV, MODs can be used to automatically/remotely isolate a section of bus or a transformer after a fault. An MOD is lower in both capital cost and ongoing maintenance than a circuit switcher. My state requires visible air gaps to isolate equipment, so we end up need both a circuit switcher and a separate regular disconnect if we go the circuit switcher route. As the switches get physically bigger to accommodate higher voltages, they become unrealistic to manually operate at a reasonable speed.

RE: MODs in new substations

(OP)
Are the MODs interlocked in any way? ID imagine accidentally opening one would wreck the switch if not more.

RE: MODs in new substations

That's what switching procedures are for. Lots and lots of ways for a cowboy to totally wreck havoc.

RE: MODs in new substations

(OP)
I agree, but an accidental operation via SCADA?

RE: MODs in new substations

MBrooke: TLA - three-letter acronym. winky smile

RE: MODs in new substations

"I agree, but an accidental operation via SCADA?"

Most SCADA systems I've worked with utilize SBO (Select before operate), giving the system operator that extra chance to verify the intended operation. As Davidbeach said, there are switching orders developed, which generally have a review process between system operations and the operations crew in the field.

Other than in GIS (Gas insulated Switchgear), I have not seen electrical interlocks, however there are things that go on in EMS (Energy Management System) / SCADA that the system operators see that I can not in the field. The MOD's I've worked with have a control switch (we call them 101 switches) and a local / remote switch (we call it a 43 switch) in the control house. The MOD controls are wired such that the 43 Switch, which is normally in the remote position, electrically blocks operation of the 101 switch, thus preventing an accidental bumping of the 101 switch.

Many MOD's have Open/Close switches and a Local/Remote switch located in the motor operator box. This is provided for maintenance / testing. I've seen switching orders that call for verifying the proper status of the Local/Remote switch in the box. I have also seen utilities disable this function in the motor operator box.

RE: MODs in new substations

(OP)
Do these MODs have position indicator switches so SCADA knows there current state?

RE: MODs in new substations

My utility does not use interlocks to prevent opening MODs via SCADA. If the MOD is used as a clearance point during maintenance, it will be disabled both via the 43 switch DTR mentioned, and by removing the mechanical linkage between the motor and the shaft going up the tower. When MODs are operable via SCADA, we usually bring back position indication. We also have some MODs on transmission lines that operate based on locally sensed loss of voltage where we do not have any communication to the site.

RE: MODs in new substations

(OP)
There is no way to "lock" the shaft when performing maintenance as you would lock the lever on a hand cranked unit?

One of the down sides to SCADA (at least a concern for myself) is that correct operation of the switches can not be verified.

RE: MODs in new substations

Most MOD's have multiple auxiliary switches for local and remote indication. Some are internal and reflect the motor travel, while others are connected to the vertical operating shaft. For SCADA purposes, I have seen the external shaft coupled auxiliary switches used most.

Some utilities I've worked for are very specific about how the indication should come in, relative to the travel of the switch. All MOD's I've worked on have a means of decoupling / locking out operation. I've seen these same coupling mechanisms used to lock the switches closed (Wind Farms rather than utilities).

I believe system operations utilizes line side VT's and or bus VT's to confirm operation if field operations personnel are not on site.

Southern States Motor Operator Switch Flyer

Pascor Atlantic also makes MOD's. S&C may, I have not checked.

RE: MODs in new substations

(OP)
Is it heard of, or common to have a switch in a position other than what the indicators indicate? My concern is under loop splitting a wrongful position indicator can do a lot of damage.

RE: MODs in new substations

The gas insulated equipment I used to work on had indication such that:

1 1 1 1 - travelling
1 1 0 0 - closed
0 0 1 1 - open

Other states were declared as illegal and locked out operation, and the two paired switches had to operate more-or-less together with a defined time-out.

RE: MODs in new substations

We interlock MODs with the status from their respective Breakers. Also Bus and/or Transformer Block close.

RE: MODs in new substations

(OP)

Quote (sn00ze)

We interlock MODs with the status from their respective Breakers. Also Bus and/or Transformer Block close.

Thats what I was thinking. Blocking any switching unless the breaker is opened or the line is in parallel with the transfer buss. Any scenario that puts full load across the departing disconnect contacts.

RE: MODs in new substations

@MBrooke . Correct. Also, most of our clients preference to disable by removing the internal wiring for the manual push button in the MOD cabinet to avoid "human error". so it only opens/close from the control module or SCADA

RE: MODs in new substations

(OP)
Makes sense then. As for advantages, it is considered safer to open / close disconnects from a distance?

RE: MODs in new substations

i'd say so, never a good idea to open it under load to begin with. not just for safety but you'd damage the equipment.

RE: MODs in new substations

(OP)
Correct, but general off load switching for breaker maintenance. Is anything gained via remote control opening and closing?

RE: MODs in new substations

Gained would be that there is not a switching agent standing generally somewhere underneath the device being manually operated that might be subjected to a rain of molten copper if something goes agley...and who must depend upon personal protective equipment as a last line of defense against such occurrences. The likelihood of this happening is of course a function of the quality, age and condition of the equipment being operated.

The down side is that there is more equipment to maintain.

As for switching from remote locations: as long as Work Protection is not a consideration, we as controllers/operators will commonly use as many tools as are at our disposal to confirm that equipment is operating or has operated correctly. The more ways we can verify that something is working the way it's supposed to, the more we like it. Switch position check-back is the primary information source; potential indicating devices are a close second, although which source or piece of equipment these are connected to will sometimes impose limits on how we can use them.

When switching transformers out of service, we don't like to remove them from potential without an agent there to confirm the three phases of the primary disconnect open; we would only contemplate doing such in the presence of three-phase transformer bushing potential devices to confirm proper switch operation such that the transformer is not being single-phased...and even then, there is no guarantee that if the switch has a problem and we close it back in that all three phases will close, and we don't want to be the ones on the hook if a bank gets damaged from such causes...single-phasing a circuit or cable doesn't carry the same risk of damage.

Spoken from an operations standpoint only, as I'm not an engineer, just a lowly operator...hopefully somewhat redeemed by years of experience and having worked with many, many different types of equipment...

CR

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

RE: MODs in new substations

For new work we use MODs at 500kV due to the high phase-phase spacing and manual disconnects everywhere else. The old 57 and 115kV MODs have a huge variety of failure modes we'd just as soon be rid of that we won't (presently) consider MODs in lieu of manual switches.

RE: MODs in new substations

(OP)
@Davidbeach: Including 345kv? I am really curious about the failure mods of these MODs. How old are they and what is being encountered?


While this video does not reflect IEEE/ANSI equipment, 1:56 and 5:52 onward demonstrates a potential benefit in using MODs when it comes to worker safety:


https://www.youtube.com/watch?v=sr42AGaIayU


Has this ever been documented in North America that you are aware of?


RE: MODs in new substations

We don't have any 345, so that's moot. Ideally a disconnect is used to drop/pick up the charging current between the switch location and the adjacent breaker. We use MODs on 500kV simply because the phase spacing becomes to larger for a single handle manually operated switch. Others do various fancy automatic MOD operations following breaker trips, we don't; they're isolation devices. Older installations still use MODs where we'd only consider circuit switchers today.

RE: MODs in new substations

(OP)
I checked and it is possible to get away with MODs at 345kv (some utilities choose not to have them at that level). In fact Id say many utilities share your philosophy and its probably 50/50.


As for the the failures you experience, they are within the operator itself?

RE: MODs in new substations

Use of motor operated disconnects (MOD) is largely a customer preference. I know of utilities that utilize MODs for all 345 kV and above equipment and others that prefer manual operation. Even if a MOD is operated locally (at the switch) time delays can be built into the operator to allow personnel to get clear of the switch before it is is operated.

Depending on the P&C (Protection & Control) employed the motor operator can be easily interlocked to eliminated improper operation.

The motor operators I am familiar with are designed such that you can uncouple them from the switch and lock out. They also do no allow for getting them out of sync (switch is closed but indicate an open switch)

The majority of the 345 kV and above switches I see are MODs but again not always. The splits is ~75/25.

RE: MODs in new substations

Even if you choose to employ MODs at a HV station, it isn't a good idea to operate them remotely without having boots on the ground to verify correct operation.

Sometimes you may want to initiate a DS operation via protection, ie: automatically, so in that case you will need MODs.

Whatever equipment you choose, it's important to know that operating practices need to reflect what equipment has been installed.

RE: MODs in new substations

(OP)
Thanks, it really is a preference based on pros and cons. One utility I know of only has MODs directly on the outgoing lines and all the remaining disconnects within the station being manual. Personally I think that might be the best route for me. Anyone have any idea of how long a MOD lasts versions a standard manual operating means?

RE: MODs in new substations

I am not sure if there is a definite answer on life expectancy of a MOD, however if there was, I'd assume it was based
on what kind of maintenance philosophy was applied and how often it was operated. I often see spare arcing horns available in the substation, which leads me to believe these are components that are likely to wear over time.

Like any disconnect switch, proper setup and adjustment are critical. As far as the motor drive unit, proper sealing and heating are critical. Most internal components are not all that different that what one would find in a breaker cabinet (limit switches, terminal blocks, control switches, indicating lamps). Of course, one get what one pays for in terms of quality and component selection.

I was at a generating station this week and there were MOD's on all 3 345 kV lines and 3 GSU connections. I asked the staff about MOD issues and none were reported since installation in 2005. All 6 MOD's had the external shaft coupled auxiliary switches (52a & 52b connected). Additionally the lines were connected to an auto reset 86 (or 94L) when the line was opened after a fault to allow the ring bus to be closed up after a permanent fault.

In our case, wasps seemed to like the the control cabinets - always something to look out for!

RE: MODs in new substations

(OP)
Id argue thats because they were never opened (assuming no line faults) in the first place. I've heard of switches that just failed when called upon 20 years latter for the first time. But now that you mention it I have been thinking about setting an auto open for bay MODs after a line trip.

RE: MODs in new substations

Switches that fail to close properly seem to love following me around. It seems that 40% of the time I am doing work (P&C upgrades, etc), when it's time to switch back in, we have issues. Its funny watching all of the associated crew members making that call / text to the wife (It may be a long day). Last January, after a transformer replacement, we went to close the 138kV breaker disconnects (40+ year old switch) and the porcelain separated from the base on one phase. That phase fell towards, but did not touch the adjacent phase. Manually operated switch with a low profile bus.

RE: MODs in new substations

(OP)
Like what happened in the Russian video? I guess thats would be a + for MODs.

RE: MODs in new substations

Do not waste time and money buying the cheap stuff... specifically cheap HV areva MODs. save yourself a tonne of money and buy the expensive stuff.

RE: MODs in new substations

(OP)
What are reputable, high quality brands?

RE: MODs in new substations

I've worked with the cheaper Areva 500kV switches and we are still dealing with issues 6 years later. Sorry I don't have a model # off hand.

I've heard the "more expesnive" Areva ones are better, but I've never seen them personally.

I think the industry trend (at least in my area) is to cheap out on the primary equipment.

RE: MODs in new substations

(OP)
How does Southern States rank?

RE: MODs in new substations

I've heard good things, but never seen one in person.

RE: MODs in new substations

Quote (Mbrooke)

But now that you mention it I have been thinking about setting an auto open for bay MODs after a line trip.

Is this on ring bus or breaker and a half? Those are the only applications where I see it making sense.

Do you plan on reclosing the breaker after MOD open? Any concern over positive switch opening?

RE: MODs in new substations

(OP)
Main and transfer. No reclose after the open. Though where would it hold merit in breaker and a half? Positive switching?

RE: MODs in new substations

I don't think you buy anything by operating the DS after a line automatic.

Some SF6 breakers will want to open their DS's based on SF6 levels... There are some transformer configurations where you may want to open the DS's as part of a protection. Think of a transformer terminated directly on a BUS. If the transformer trips, it will take out the entire bus. An automatic DS operation could potentially speed up restoration of the bus.

Remember that Breakers are 'Protection' devices. DS's are 'Operating' devices. DS's can in no way be relied on to actually open automatically, and any MOD operation in a switchyard really should have someone on the ground to verify correct operation. If you really want to trust in remote DS operation without field personnel confirming the operation you could look at using cameras, but imo that's just adding to much stuff for not much gain. Maybe a good idea in very remote locations.

RE: MODs in new substations

Quote (Mbrooke)

....Though where would it hold merit in breaker and a half? Positive switching?

In both you only get a benefit if the breaker is reclosed after the line switch is open.
The benefit is greater on a ring. With a ring, any other subsequent fault will break the ring.
In a breaker and a half scheme the benefit is the continued access to both busses by the associated line. I can't remember all of the details but one of the West Coast US blackouts impacting LA and Pheonix was from two sequential tree faults on lines blocking access to SVC.

The better fix was to not pair SVC with lines.

RE: MODs in new substations

(OP)

Quote (marks1080)

I don't think you buy anything by operating the DS after a line automatic.
There are SEL relays (and others) that can be configured to open after a breaker has locked out.


Quote:

Some SF6 breakers will want to open their DS's based on SF6 levels...

I've been thinking about this. My understanding is that once the breaker trips on low low, the breaker will still hold is dielectric properties. Just not be able to interrupt any current.


Quote:

There are some transformer configurations where you may want to open the DS's as part of a protection. Think of a transformer terminated directly on a BUS. If the transformer trips, it will take out the entire bus. An automatic DS operation could potentially speed up restoration of the bus.

Yup, seen those. Often the transformers are directly attached to the line or at a remote substation without a breaker protecting the transformer. When the transformer faults a transfer trip is initiated. Once the transformer's MOD opens, the line then re-closes. Such philosophy can be taken further into line sensationalizing. However all new substations that I design have the transformer protected with a breaker (or fuse on the smaller units). Thus MODs in this application are rapidly declining for me.



Quote:

Remember that Breakers are 'Protection' devices. DS's are 'Operating' devices. DS's can in no way be relied on to actually open automatically, and any MOD operation in a switchyard really should have someone on the ground to verify correct operation.

Unfortunately not in my case. MODs are often controlled automatically or via SCADA for a variety of reasons. In ring buss designs once a line locks out its line MOD will open and breakers will then re-close. In split buss stations with 2 lines, one breaker and 2 transformers mods will isolate a faulted line and then re-close the center breaker. In dual feed substations MODs (usually these MODs have SF6 bottles in these cases) are used to open the faulted line and close the normally open line to restore service. All this done automatically. In single breaker double buss applications possessing only a single buss zone a buss fault is dealt with by opening all the MODs on the main bus via SCADA and then closing the mods connected to the auxiliary buss. The breakers are then remotely closed to bring the station back into service before the main buss can be inspected and repaired.


However these concepts are starting to fade in new substations. In my world disconnect switches are starting to become service/isolation switches rather than being part of an integral protection and relaying scheme.


Quote:

If you really want to trust in remote DS operation without field personnel confirming the operation you could look at using cameras, but imo that's just adding to much stuff for not much gain. Maybe a good idea in very remote locations.

I've though about that. But come serve weather it question visibility.

RE: MODs in new substations

(OP)

Quote (MatthewDB)

In both you only get a benefit if the breaker is reclosed after the line switch is open.
The benefit is greater on a ring. With a ring, any other subsequent fault will break the ring.
In a breaker and a half scheme the benefit is the continued access to both busses by the associated line. I can't remember all of the details but one of the West Coast US blackouts impacting LA and Pheonix was from two sequential tree faults on lines blocking access to SVC.

The better fix was to not pair SVC with lines.


Thanks, makes sense. :) Where an SVC is present or critical auto transformer with breaker and a half its best to have its own bay with only 2 breakers.

RE: MODs in new substations

I've heard arguments that the ideal dual voltage transmission substation is a breaker and a half, with two auto-transformers situated between the higher and lower sections. Loss of a bus means loss of 1/2 of the transformer capacity, but no fault can cascade to the loss of both transformers.

Another idea is to put the two transformers on the same bay, but run with MODs on the center breaker normally open. Same limitations on cascading faults, but if a bus is lost, it is possible to return both transformers to service.

RE: MODs in new substations

Ok, I'm entirely not following the 1/2 capacity bit. The transformer is either connected on both sides (full capacity) or it isn't (no capacity). How the heck does one come up with half capacity?

RE: MODs in new substations

(OP)
I think (I think) he is referring to each buss having its own direct transformer connection, and the loss of one buss results in losing one transformer leaving only the other (half the total station capacity) I however do not follow " no fault can cascade to the loss of both transformers."

RE: MODs in new substations

A transformer is a position; built the same way as a line position; transformer is connected between two breakers. If one breaker trips for a bus fault the transformer is still connected, no capacity is lost.

RE: MODs in new substations

(OP)
Correct, but many utilities will attach the transformers directly to the buss. That and its possible if you loose a line on the other side of the center breaker while a bus is out you will also loose a transformer.

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