MODs in new substations
MODs in new substations
(OP)
Are MODs recommended or used in new substations? If so what advantages do they provide?
When was the last time you drove down the highway without seeing a commercial truck hauling goods?
Download nowINTELLIGENT WORK FORUMS
FOR ENGINEERING PROFESSIONALS Come Join Us!Are you an
Engineering professional? Join Eng-Tips Forums!
*Eng-Tips's functionality depends on members receiving e-mail. By joining you are opting in to receive e-mail. Posting GuidelinesJobs |
|
RE: MODs in new substations
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
EDIT: Motor Operated Disconnects
RE: MODs in new substations
Do you use interlocks?
RE: MODs in new substations
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
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations
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
RE: MODs in new substations
RE: MODs in new substations
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
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
RE: MODs in new substations
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
RE: MODs in new substations
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
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations
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
RE: MODs in new substations
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
RE: MODs in new substations
As for the the failures you experience, they are within the operator itself?
RE: MODs in new substations
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
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
RE: MODs in new substations
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
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations
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
RE: MODs in new substations
RE: MODs in new substations
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
RE: MODs in new substations
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
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
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.
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.
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.
I've though about that. But come serve weather it question visibility.
RE: MODs in new substations
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
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
RE: MODs in new substations
RE: MODs in new substations
RE: MODs in new substations