Multifunction relay 4

[slavag]

Hello.
What is your opinion about "new" generation of low impedance BBP is include bay protection.
We commissioned three such systems and I'm hope we contniue with it.
Isn't commercial thread. Please w/o types and companies.
I see the tread, as continues of two previous 521AB's threads.
Thanks for advance.
Regards.
Slava

 

[slavag]

Sorry, forgot attached them:
thread238-211587
thread238-211068

 

[521AB]

Slavag, make it more clear.
You want a comparison with the "old" way?

 

[slavag]

Hi.
Sorry, I try make Q. clear. I told about low-impedance BBP ( busbar protection 87B)
1.Before about 15 years BBP was separate protection relay/relays w/o BFP( breaker failure protection 50BF),it was additional relay. For provide more secutity used additional relay for the overall check-zone, etc. Very " old" generation of BBP+BFP relays
2. At middle 90's ( I think) start "new old" generation of numerical BBP+BFP protection, it was relay include both of protections BBP+BFP into one box w/o current switching and included end fault protection ( fault between CT and CB).
3. New generation ( started before about 5-7 years) are include also feeder protection functions: overcurrent ( 50,51), earth fault ( 51N, 50N), etc. in the same box for each feeder.
Before 5 years for excperement we puted in operation one such system and warm discussion continue up today ( I told about utilities).
As I saied isn't commercial issue, intresting your's opinions. For such protective relay , I prefer used term protective system.
Regards.
Slava

 

[lz5pl]

My preferable concept for feeder protection (66-110 kV and above) is to have Main protection, Back-up protection and BBP+BFP as 3 separate relays.
In Bulgaria it is not acceptable to combine Bay controller functions with protection functions in one box for HV bays, but I cannot see why not to use combined Bay controller and Back-up protection, at least for 110 kV level. If Back-up is only O/C and E/F I don't think the processor will be very busy with additional load from control functions. Well, I wouldn't use Bay controller combined with distance protection, although I cannot explain rationally why :~/.

In my opinion, it will be better not to combine back-up protection with BBP in one box. Busbar protection is something very specific and it happens that it to be set out of operation for maintenance or due to problems with some of bay controllers. In such cases it is possible that(depending on type of failure or testing) bay units should be switched-off and bays will remain without Back-up protection.

By the way, cost of BBP always is looking for me too high for the amount of protection functions included (the amount of science inside, as my professor from the University said for other type of relays). I compare with distance or generator protections, the price difference is several times. The price level is similar with all manufacturers, probably they have some serious reason out of my limited understanding of the problem. Well, this is another story, let's concentrate on engineering ! ;-)

With current level of computer technology possibly we could protect even one small switchgear from one box, but where will be backing-up then?! "Old" concept for separate CT-cores, separate VT-circuits, separate tripping coils, etc. couldn't be replaced only by increased power of processors.

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It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant

 

[slavag]

Plamen, thanks a lot for your opinion.
Actually, my ask is about your feeling, not who, why, etc.
Best Regards.
Slava

 

[lansford]

I recently did a setting study for a large industrial main service where all of the relays were essentially numerical relays that did everything. Every relay had a book of about 500 pages and each relay did everything uder the sun even though we only needed one function in many of the relays such as bus diffenetial.
And this was the case for all of the overcurrent and various types of differential and voltage relays.
In this project, it was very costly, time consuming and confusing and my preference would have been to use a much simpler and for many protective functions, single function relays.
JIM

 

[521AB]

I would try too see the problem from this simple point of view: what is the reliability of an old system compared with the reliability of the new one?
It is possible to do such calculations, putting together theoretical models with data collection from the experience, but these people do not work in our field, and we do not ask them to help us. It is very difficult to talk about statistics with relay people, but it would be the only way to get facts in our hands.

I think the new system is much more reliable than the old ones. But of course, new systems need education. You must be a specialist, or almost.
On the other side, such "virtual cubicles" are complicated because you are concentrating a complex system in a small box. If you know what to do with the separate pieces, you should be able to manage the boxes with everything inside.

A "standard" cubicle, containing 30 wired relays, CANNOT be more simple than a box where the 20 relays are software functions connected with some lines drawn on the PC screen.

Do you think that the so called "busbar replica" was / is an easy and reliable system?

A lot of people still buy used cars because they want to repair them by themselves. If everybody would do like this, there wouldn't be any progress in the automotive industry, so...

 

[slavag]

Hi.
Thanks a lot Jim and 521AB for your opinion.
Jim, I see such projects, where multifunction relys are used as single-function relay. It's crazy, but, what we can do, customer want and pay for it.
Of course, I say about feeder protection at BBP are used as back-up protection not as main, btw main and back-up protection terms are not so clear. For example, what is amain or back-up: distance or differntial?
Plamen. distance protection and control in one box relay, today is possible, but I don't sure, if we start with this option, maybe???? only used this as back-up control option.
Don't know , I'm only start think about it.
What is intresting?
We can put all function of generator, transformer and distance protections at one box, we connect BBP and BFP and end-fault protections at to one box too, but next step is so hard for us.
See simple application:
infeeds- bus- trafos.
for infeed, we need for example 50,50N,51,51N ( overcurrent and earth/ground protections), for bus 87B and 50BF and for trafos 87T ( trafo differntial) and 50,50N,51 and 51N. Customer request redundancy protection , no control.
Possible put:
1. 50,50N,51,51N at one relay for the feeder
2. 87T at the one relay for the trafos.
3. One BBP+BFP+ 50,50N,51,51N for each infeed and trafo.
Now, what we save:
one CT core per feeder
one cable from CT to protection panel per feeder
one relay per feeder
additional materials: wiring, MCB's, terminals, spare parts, maybe cubicles.
extra work: design, commissioning, settings.
What is disadvantage:
More complex system
Not simple maintanance of BBP+BFP.
For change some setting you need change it at relay is responsible for whole system.
if you need add some feeder, you need change whole BBP+BFP, not simple and probably costly. But you need provide this job in all cases.
521AB, but same with interlocks are base on the GOOSE messages.
Now, next step, customer request also control:
1. We put bay controller with 50,50N for infeedes
2. We put bay controller with 87T for the trafos. Actually with tap-changer control included. All trafo protections ( Buhholtz, Oil level and temp, etc) we connect to bay controller and to BI's of BBP+BFP relays in parallel.
I know, it seems crazy, but why not do it.
Regards.
Slava

 

[521AB]

We have the technology for integration of functionality since more than 10 years.
The problem is not in the technology, but in the philosophy.
If you want to have MAIN 1 under battery 1 and MAIN 2 under battery 2 and control under battery 2 (but from a different feeder, so actually you can call it battery 3), then you cannot integrate protection and control in the same box.

As I said, I think it is more complicate to make the busbar replica with aux. relays then a system with bay units.... and if you ask to one recently graduated engineer, that has studied z-transform and not the air gap in one coil for calculating the magnetic flux necessary to the electromechanical relay, he will tell you the same.

So, the only serious way to compare the systems is to have a statistical approach and find out the reliability of the two methods. We will probably see that the integrated approach is more reliable.
Something gets broken? You need to change mentality here, you cannot have the screwdriver in your drawer . You may have a copy of the bay unit in your drawer.

And now I tell you a true story, which happened to me:

I was in a taxi some times ago, a young taxi driver. He was driving me from one city into another city. I told him the address and he wrote it in the GPS navigator.
Then I asked him: do you know where we are going? He said "no".
So, without GPS you would not be able to work.
"Exactly", he said.
And how do you do if it gets broken?
"If it gets broken?..." He opened the front drawer of the car and showed me: "I have another one, of course!".

The taxi driver has accepted the technology and uses it without trying to use the old methods. He is "native" in the technology.
We are not, that's why we are questioning so much. We would like to use the new technology with the old methods, and I think that we should learn more from the taxi driver....

 

[slavag]

512AB, thanks a lot. Good points. Very intresting and important for me. If EE like to you, according to all your posts you are like new technologies, against....
Isn't important, that I'm not so agree with you, we haven't here " right--not right".
Of course used old methods.
Believe me, I'm not "native" in the technologies.
Regards.
Slava

 

[lz5pl]

Excellent story 521AB ! Our young engineers think exactly this way and may be they are right. But it will take some time before they take decision-making positions in utiliies. Until this moment our generation of "electromechanical relay thinking" dinosaurs will duplicate and triplicate multifunction "black boxes".

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It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant

 

[DiscoP]

This is a good topic !

I think that if you had 2 separate boxes, run off 2 separate batteries, CTs, Trip coils etc, then technically there is no reason you couldn't have an 'X' Multifunction relay and a 'Y' Multifunction relay.

As slavag says, this is common practice now for generator protection.

One day this might be the norm. The busbar is a different zone of protection to the feeder / transformer / generator so there is no back-up issues.

The technology is there, but in my opinion from a practical perspective setting this up in the relays currently available would be too confusing.

We use Low Z BBP relays and have decided to keep it as simple as possible. The consequences of an incorrect BBP trip can be severe !

It would also be hard for a manufacturer to make a relay flexible enough for the number of different busbar configurations out there and also make it easy to use.

From my experience, the more flexible the relay is, the harder it is to set it up.

Also, I am not sure if it is out there, but the relays we use only offer overcurrent as the back-up feeder protection.

To have Distance protection or transformer differential it would need a lot more AC inputs. The relays are big and heavy enough as they are.

I think it is practicality of the idea that prevents it from happening, but as a concept it would be OK.

 

[slavag]

DiscoP.
Thank you too.
I continue warm discussions with customers and designers.
But big part of discussion is comercial part. Isn't important at this thread.

99% of them thinks exactly as you, but... few customers would like check this option.
Best Regards.
Slava

 

[slavag]

O.K.
I would like continue and add next step. BBP+BFP isn't one box solution, are slave units are connected to one Master unit via FO.
Now we have some old substation and have provide retrofit. As usually, retrofit go bay by bay, several monthes.
Customer decide add BB+BFP protection. But, OOPS, havent spare cores for the BBP+BFP. And customer won't add additional cabels. What is your solution???
My way are:
1. I check this system at the some test field for the check zone statuses and BFP logic.
2. Install slave unit, check all, except BBP ( BFP internaly connected into the slave), check all signals and trips.
3.Continue with each slave and at end of the retrofit connect all to the master unit.
3. Now dissconect in the master all "BBP+BFP" trips, check diff current in several options and connect all to trips.
Please see I didn't add and change any control and current cables. didn't replace CT. Only add few FO jumpers.
And additional bonus. Customer would like connect new relays to some SCADA system. Instead connect each bay, I need only connect and synch by GPS only one Master unit.
Please your comments.
Thank you for your answers.
Best Regards.
Slava

 

[slavag]

Plamen, forgot something. Today one customer asked me:
BTW, way you don't design control functions into distance protection with back-up control into diff protection??? For what I need pay for additional contol relay???
About five min I was w/o any words.
Customer from some utilities!!!!!

 

[lz5pl]

slavaq, according to me your approach in this retrofit is the correct one. I would do it the same way.

About your second customer: Ask him for double price for engineering and duplicate control in both relays. Or even better: advice him to back-up software interlockings with hardwired ones and ask triple price ;-) !

Seriously speaking I had several cases when I advised the customer not to do something what he initially wanted from me, although I lost profit from this job. The only positive outcome was my good reputation (possibly only in my own eyes ). Not every client is ready to take good advice as something that costs money, unfortunately.

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It may be like this in theory and practice, but in real life it is completely different.
The favourite sentence of my army sergeant

 

[slavag]

Hi Plamen.
At this case, it's really triple price!!!. But at another case, I'll think, maybe for some small substation , of course w/o any back-up control,it is possible. For MV I'll get to this solution w/o any problems.
I never do any design according to customer request, if I see some poor solution or dangerous. Good reputation isn't simple words, especialy for you, Plamen. And we always try found for customer optimal solution ( price--technical). We are small local company, after design and commissioning we "merage" to customer for many years .
Start thinks about multifunction BBP, guys, it's future, maybe;-).
Regards.
Slava

 

[521AB]

You can integrate in MV systems because there is usually one battery only, and then "main", "back-up" and "control" are under the same dc (even if from diffrent DC feeders).
On higher voltage levels, the main requirement is the CLEAN DC solution. SO you cannot integrate because you cannot have different DCs in the same cubicle, to make it simple.
But this is the yesterday extrapolated in the today (I am using the yesterday solution, two batteries etc) for the today's solution (integration).
For new installations, maybe it is a good idea to start to think directly in the new technology... but I also don't know, I am not 25 years old. I see what and how younger engineers (and not only engineers) think, and I try to respect it and to learn from it, but the solution I don't have, right now. Continue with two batteries and don't integrate.

 

[slavag]

Hi.
No, No and next time NO. Of course only two DC, isn't Q.
And prefer for combinated protections or protection/control used relays with double power supply and for inputs some changeover DC relay. I told about Main1 with control option and Main 2.
Regards.
Slava