Current's direction on relay for generator 1

[Morquea]

I would like to find documentation about how the current direction could affect the proper fonctionning of a protective relay.

We are connecting a 600V power house (PW1) to a 4160V power house (PW2) throught a step-up transformer.
The grid configuration can allow to feed PW2 with PW1 and vice versa. There is a GEC ALSTHOM (now AREVA) LGPG111 multifunction relay at PW2 that we wish to use. Actually, we want to mainly use the voltage dependent overcurrent proctection function (51V). I have an option to set it as a simple overcurrent protection (51). I discussed with Areva about it. They told me that it is possible but that I should beware of the current direction.

So I look for a better understanding on how the current direction could affected the relay.

Thank you

Danny Garant, ing.jr
Groupe Stavibel Inc.

http://www.stavibel.qc.ca

 

[dpc]

We will need to know the intended function of the relay - what is it trying protect?

Normally, a 51V is used as backup phase fault protection for a generator. The voltage control or restraint allows the relay to be set to pick up below the load current of the generator during close in fault conditions. A 51V is non-directional, but they may have been referring to the fact that the fault current will vary tremendously depending on the location of the fault wrt to the relay CTs.

For faults where the relay sees only current coming its generator, fault current will be relatively low. For faults where the relay may see fault current from the grid, the current could be many times higher.

 

[slavag]

Hello Danny.
Could you please send us connection scheme.
As Dave saied, 51V( voltage controled) or 51/27 ( voltage restraint)functions used as block gen-trafo backup protection and are non directional.
We used several time directional overcurrent 67, but for decoupling detector, not as generator protection.
Regards.
Slava

 

[Morquea]

Thank you

I attached a scheme of the connection between the two powerhouse. The relay in question will protect a transformer on the 4160V side. The winding are Delta on 600V and WYE (without ground) on 4160V. The 4160V bus bar is at the main power house and is tie with an other bus containing a set of three generator (not shown)

The temporary power feeds a MCC, a permanent accomodation facility (PAF) and Administration & Services buildings (ASB). This when the PAF and ASB are not fed by the main power house.
When the main power house feed the PAF and ASB, the power from the temporary power will be rerouted to the main one.

I had found that 51V was not directionnal before reading your answer. I still need to study the functions of the relay to choose wich one I could use, must use or disabled (87G, 51N, 59N-1/59N-2, 67N, 32R/32L, 46,,40, 27, 59, 81U, 81O, 60, 51V). I had already do my preliminary analysis but I might have more questions about that installation in a near futur.

Thank you dpc, it gives me a new angle to study. Thank you Slava, I will look for more about decoupling detecting.

Danny Garant, ing.jr
Groupe Stavibel Inc.

http://www.stavibel.qc.ca

 

[slavag]

Hello Danny.
Several additional Q's.
1. Are you have connection to utilities too?
2. Are possible some power flow from PW1 to PW2.
3. Are you have VT(PT) on bus with broken delta connection?
( on PW1 and PW2).
4. What is ground protection used today on generators?
5. Are you used some load shedding functionality?

From first reading:
Maybe you need directional overcurrent 67.
It's detect where is fault : direction to PW1 or it's PW2 internal. Final soolution request serious protection study:
1. Fault on the PW1 side , after trafo.
2. Fault on the PW2 bus
3. Fault on the PW2 outgoing feeders.
Trip of this 52CB request coordination with generator CB's, with outgoig feeders and bus-tie CB.
please see fault on the PW1 side also different:
1. Before trafo
2. After trafo.
Are different level of current and voltage
This is a reason why Areva recommended to you use direction
current detector in additional to 51V function.
BTW, possible use function 32(reverse power) for this porpouse, is more sensetive and simple than 67.
Ground fault:
At ungrounded systems is very problematic.
I see option used 67N ( directional ground fault) only in
PW1 direction, that means 1pf fault on cable up to trafo.

Function 81< ( underfrequency) in case of power flow to PW1
and underfreq situation, possible send trip to this coupling CB ( as option only).
function as 40,46,21,27,59, 87G are generator protection functions and for my pinion you don't need used them.
Good Luck.
Wait to other response and your answers.
Regards.
Slava

 

[Morquea]

Answers to new questions :

1. No, there is no connection to utilities. The context is a remote mining site, where tundra is the kind of vegetation. There are 13 generator including the fives shown in the scheme. Seven of them are supposely dedicated for back-up supply.

2. Yes. When the PW1 won't be used to supply the PAF and ASB, the client want to be able to use PW1 to power PW2 in parallele with PW2's generator. Synchronisation will occur on PW1. Meaning that PW2 would supply the phase and voltage level on PW1 and PW1's generator will synchronise themselves on PW1 before closing their line breakers.

3. I will answer later. I have to do some research to know if it's the case.

4. PW1 and PW2 are each grounded through zig-zag transfo and inpedance (rated 5A). KCGG-110 relay monitor ground fault (51G) on PW1. It trips all generators. The CT's is connected between impedance and ground (Bus Bar - Zig Zag - Impedance - CT - ground).

5. I'm totally unaware of it. I'll do some research on the question.

I will take more time to assimilate your answer before I make any commentary.

Thank you very much for your insight

Danny Garant, ing.jr
Groupe Stavibel Inc.

http://www.stavibel.qc.ca

 

[slavag]

Hi Danny.
O.K. now situation is more clear.
1. From my point of view, you don't need any 67N too, just connect to KCGG110 relay in parallel and it trip all generators and coupling breaker too.
2. I assume you haven't broken-delta PT connection and you don't need it.
3. What I think: yes, used function 81,27,59,46 as generator protection, but with lower settings than at generators.That means, in case of some fault, first of all disconnect PW1 and PW2.
4. yes, used 51V with 32 reverse power detector , on this moment I think in case of power flow from PW2 to PW1.
But, on this moment, difficult say something w/o power/fault flow study.
Regards.
Slava

 

[slavag]

Small additionals.
Please check, if KCGG110 relay have additional(free) trip stage and free contact.
If yes, used for trip to coupling breaker with lower setting too.
Next option, if CT ground have additional core , connect it directly to new relay.
I would like back to 51V with direction current detector.
Maybe need simplicity this issue.
Used two sets of 51V+32 function w/o many variation:
1. fault on PW1
2. fault on PW2.
or more simple, used 51V w/o any direction detector.
Next issue, that need think: coordination between 600V and 4KV trafo CB's.
From my point of view, also do it simple: cross trip to both CB's.
In several words. Not important what happend in the system and where, first of all disconnect coupling between PW1 and PW2, PW2 it's exsiting system, don't change anything, disconnect PW1 and system will operated as " island", samr for PW1.
Regards.
Slava

 

[Morquea]

Wow, thanks. It left me with one more interrogation.

About note 3 from your 23:35 post, I thought I could disabled those function. PW1 generator have each their own generator protection set provide by the manufacter (That point might not have been clear in my previous post). Since each generator is monitored, I thought it wouldn't be necessary to use those functions.

I mentionned this cause we thought of suggesting to connect the 4160V side where only a KCGU* would protect the feeder. I was to discarded those functions thinking the weren't necessary.

However, I think it would be nice to keep them if only I could established why we shall keep them. So, I'll checked again today to see if I can explain to my colleagues why it is needed. I will post my understanding if I happen to find it before you point it.

*Note : The main power house switchgears already contained the protection device we want to use (may it the LGPG111 or the KCGU). They are already connected with the proper CT's and PT's and their settings already set. Ultimately, we think that all we need is to adjust the settings and testing.

(I'm not in charge of the power/fault flow study. I'm waiting for the Tempory power house study and I don't expect it to take care of the whole systems. The step-up XFO was not originally in that project)

Regards

Danny Garant, ing.jr
Groupe Stavibel Inc.

http://www.stavibel.qc.ca

 

[slavag]

Hello Danny.
I see this system as two separate system.
What I would like say.
You have PW2 exsiting system with all protections, logics
was tested and good for the customer.
You add new system PW1. This new system will operated as load or as source of energy.
Instead recalculated all setings, change and test again all protection, I recommend, first of all decoupled PW1 and PW2 and will give to each one chance for "live".
For example: underfrequncy situation, 81 function , we don't know what is a reason, problem at PW1 or at PW2. assume at the PW1, we disconnect systems and cancelled risk for PW2's generators. setting for generator trip, I don't know, assume, 58.5Hz 10 sec, put setting on the coupler for the 59.2HZ for 2 sec. Same for the unbalance situation, 46 function.
51G function, monitor on the zig-zag see ground fault, where, we don't know, on PW2 or on the cable to trafo. First of all disconnect coupler between PW1 and PW2 and each system continue as "island".
Are just ideas, my view of system, of course aren't solutions.
Best Regards.
Slava

 

[slavag]

You know, on this moment, is not so important, used or not used those functions. Very important choice relay, is suitble for all situation and with spares of inputs and outputs. I know, people start with: this relay very expensive, we don't need it, put simple 50,51,50N,51N is enouph. Don't do it, put this relay ( maybe Areva have more modern relay, with logical functions) connect all analogues inputs and digitalies input and output and put not "needed" function in disable. For this project price of one relay="zer" Believe me, after one , two year, customer will add this functionality.
Good Luck.
Slava

 

[Morquea]

Hello Slava
Thank you very much for your help.

I'm confident now that we will be able to make our recommandation about the option of using the existing LGPG111 in regards to the option.
The second option is to replace the LGPG111 by a relay with only 25-27-50-51-50GS-51GS (KCGU-140). Such configuration already exist on their system (not shown on the scheme) to connect the backup power house to the main one.
If the second option is prefered, the LGPG111 would be kept as a spare part.

I'll keep you informed about the final decisison.

Regards


Danny Garant, ing.jr
Groupe Stavibel Inc.

http://www.stavibel.qc.ca

 

[slavag]

Hello Danny.
Of course, 25 ( synchrocheck) functionality. I see it as part of separate synchronazing/control system, not as protection part.

Tundra, tundra, is cold!!!!!
Regards.
Slava

 

[slavag]

Hello Danny.
I understand that GEC Alstom ( today Areva ) relays are your standard. Please pay attention on the MiCOM P12x sreies
of Areva, P127 seems is nice relay, maybe not at this projects, but for the future.

Regards.
Slava

 

[Morquea]

Lastest feedback on the project

They decide to install a SEPAM-1000+. They won't dismantle the currently installed LGPG111 since there is room to install the new equipment. So they will just disconnect it and reconnect the CTs to the SEPAM.

Thank you Slava for the continuous assistance you provised. Thank you dpc for your contribution.

Regards



Danny Garant, ing.jr
Groupe Stavibel Inc.

http://www.stavibel.qc.ca

 

[slavag]

Hi Danny.
Thank you too.
From my point of view, isn't best choice, prefer new SEPAM devices or SEPAM2000, but it's customer choice.
Best Regards.
Slava

 

[waross]

Hi Morquea;
A tip on site etiquette;
If you have found Slava's information to be helpful, don't forget to click below his answer where it says
"Thank slavag
for this valuable post!"
Yours

Bill
--------------------
"Why not the best?"
Jimmy Carter