Trip relay mal-operation - Electrician Talk - Professional Electrical Contractors Forum

m.s.j · 12-03-2007, 11:38 AM

In a bus bar protection scheme applied for a double bus high voltage substation, protection systems design group have chosen high speed trip relay with operation time equal to 4 ms and a 2.5W DC bobbin; because they want to decrease the thermal stresses on output contacts of protection relays. As you know in high impedance bus bar protection scheme they must start several trip relays in bus bar faulty conditions simultantinusly.Therfore, dc circuit currents specially the circuits that involve to protective relays, must be considered carefully in detail design step.

But in practice they met some mal-operation of trip relay in pre-commissioning stage. According to pre-commissioning reports,
mal-operation had been accompanied with a DC battery system alarm for earth leakage.
Can you explain the reason of that mal-operation?

BEST REGARDS
MSJ

Creative thinking is enjoyable,Then think about your surrounding things and other thought products. http://electrical-riddles.com

brian john · 12-07-2007, 08:45 PM

SWAG
I assume this is a high impedance grounded system, the fault current required to alarm a system of this type is based upon the impedance of the system and trip currents are typically in the 10-25 amp range. Arriving at this level fault current is easy with a battery.

John Valdes · 12-08-2007, 12:12 PM

m.s.j.
I mean no disrespect, but why are you in this forum? Are you an engineer? Physics teacher?
I have read several of your post's and never understand anything you are talking about. You seem to be very intelligent, so why here?
Respectfully......John Valdes

brian john · 12-08-2007, 12:31 PM

For a while I was avoiding his post as possibly trick. Now It does not seem to matter as he never post an answer or critique of answers.

Speedy Petey · 12-08-2007, 12:34 PM

That's what bothers me. It seems he is trolling for something.

There are very few here that understand his posts.

te12co2w · 12-08-2007, 12:39 PM

Quote:

Originally Posted by Speedy Petey

There are very few here that understand his posts.

Thank goodness for that. I was beginning to feel like I never had a handle on electrical at all.

m.s.j · 12-10-2007, 03:19 AM

According to commissioning report, even without any load current on that mentioned cable, they had measured more than 2A in secondary side of core balance CT.
Regarding to cable length, I think that problem involved to AC cable capacitance current of three phase medium voltage cables.

What is your opinion?

m.s.j · 12-10-2007, 03:29 AM

Quote:

Originally Posted by John Valdes

m.s.j.
I mean no disrespect, but why are you in this forum? Are you an engineer? Physics teacher?
I have read several of your post's and never understand anything you are talking about. You seem to be very intelligent, so why here?
Respectfully......John Valdes

I never asserted to know anything about electrical or non electrical subjects, I just designed many practical questions consist some deep electrical conception and tried to share our knowledge and experience for more discussion and technical dialogue.
As you know each question can be had several correct answers and there are some things for thinking in each new answer. However this activity is a mental try to share our knowledge, experience and practical information in electrical engineering. I hope you participate in this unison that has been constructed for science propagation.

I don't need to show off.
I like the beautiful minds.

My watchword is "THINKING IS ENJOYABLE THEN THINK ABOUT YOUR SURROUNDING THINGS AND OTHER THOUGHT PRODUCTS"

BEST REGARDS
MSJ

Speedy Petey · 12-10-2007, 07:41 AM

Quote:

Originally Posted by m.s.j

However this activity is a mental try to share our knowledge, experience and practical information in electrical engineering.

This is our point entirely. Very few of us here are EEs. We are mainly contractors and electrical related tradespeople. We all deal with electrons long after they leave the places you are talking about.
Personally, apart from a childish curiosity, I really don't care how a power generation plant works. I have far too many jobs to keep my mind occupied. Jobs that I need to know how to do, and to do well.
And this usually has nothing to do with high speed trip relays with operation time equal to 4 ms and a 2.5W DC bobbins.

If I am being rude or I am off base someone please let me know.

bigredc222 · 12-10-2007, 08:53 AM

I think m. s. j. has good intentions. He's trying to help us expand our knowledge. The problem is, it's to much of a leap from were we are to were he is. Like about 4 years of school, maybe more. Most of us became electricians because we weren't any good in school. We are good with our hands. If you gear your questions for maybe a first year student, then maybe we would have a chance. As it is they are so far over our heads, it might as well be Latin. On the other you might be some genius that likes to make fun of the dumb guys.

brian john · 12-10-2007, 11:53 AM

I think the intentions are all good. Not sure if my responses are.

gilbequick · 12-10-2007, 01:52 PM

MSJ's intentions and thoughts are good. The difference comes in where he is coming from with his electrical knowledge and understanding of how it is created and distributed and our knowledge about how it used and put to work.

I understand verrrrrrrrrrrrrrrrry little of his questions, but they do make think and I appreciate them, and I do look up some of the references.

So, I don't understand it, but thanks for making me think outside of my normal realm.

brian john · 12-10-2007, 08:18 PM

Assuming my responses are close? I can answer some questions you may have regarding high resistance ground systems.

m.s.j · 12-11-2007, 02:50 AM

Please excuse me. I always like dialogue especially with good peoples similar you.

I will never annoy you in future.

BEST REGARDS
MSJ

bigredc222 · 12-11-2007, 08:21 AM

It just occurred to me that English isn't his first language. That may be part of the problem. I still wouldn't have any idea what he's talking about. I think he should keep posting is questions. I feel bad now.

DBack Elec · 12-11-2007, 10:36 AM

Quote:

Originally Posted by m.s.j

According to commissioning report, even without any load current on that mentioned cable, they had measured more than 2A in secondary side of core balance CT.
Regarding to cable length, I think that problem involved to AC cable capacitance current of three phase medium voltage cables.

What is your opinion?

This is true MSJ, the power company often does what we call "bleeding down the line" or removing the power that is stored in the cable.

Speedy Petey · 12-11-2007, 03:24 PM

Quote:

Originally Posted by m.s.j

Please excuse me. I always like dialogue especially with good peoples similar you.

It's not a matter of annoy. It's that everything you post is out of our scope of work, education, experience, etc. Well, most of us at least.

Keep posting, just maybe you can bring it down to our level a bit?