3.3 KV MOTOR OVER CURRENT PROTECTION SETTING VALUES? 1

[afzumannu]

DEAR ALL,
WE HAVE 3.3 KV 160 KW MOTOR, 7SJ600 NUMERICAL PROTECTION RELAY USING FOR MOTOR PROTECTION
MY QUESTION IS WHAT SHOULD BE THE SETTING VALUES FOR OVER CURRENT PROTECTION I> LOW SET I >> HIGH SET I>>> INSTANTANEOUS SET AND IE> IE>> SETTING WITH DEFINITE TIME, MOTOR IS CONTINUOUS OPERATION, PLEASE GIVE ME IDEA WITH REFERENCE OF MOTOR RATED CURRENT, CT RATION IS 40/1 A,
I HOPE ALL WILL HELP ME

 

[ScottyUK]

PLEASE STOP SHOUTING and turn the damned caps lock off.

Is this a contactor feeder or a vacuum circuit breaker? With backup fuses you don't need the instantaneous elements, the fuses should look after anything above the contactor's breaking capacity (which isn't all that high). With a breaker you'll need the instantaneous element.

 

[afzumannu]

Vacuum contactor feeder..but what should be the set value of definite time over current for low stage I> and high stage I >>

 

[ScottyUK]

Difficult to say - you need to know a lot more information about your cable's damage limit, the characteristics of the upstream protection you're coordinating with, the starting behaviour of the motor, the overload capability of the motor, and so on. Generally you'd set the protection as low as you can without risking nuisance trips. Most of the time this would be modelled as a system using Powertools or ETAP, although you can do it manually with a bit of effort. If you've never done it before it would help immensely if someone could take you through it step by step.

 

[afzumannu]

You are true that you need to know more information. It is Siemens Motor. 160Kw, 3.3 kv. I am just general asking how much % should be set value of motor rated current, 150 % or what?, I am not looking for upstream co-ordination, just want to protect the Motor, just give me the general setting value

 

[jraef]

You should discuss this with Siemens. It's their motor, their relay.


" We are all here on earth to help others; what on earth the others are here for I don't know." -- W. H. Auden

 

[afzumannu]

Dear, setting was wrong and it was from past 15 year installed the Motor and relay...now we have to correct the set value..so I m asking

 

[davidbeach]

First off, how do you know the setting was wrong? Bad settings don't generally last for 15 years.

 

[afzumannu]

Setting was wrong it was setted in infinitive and our one motor Burnt already..
I am asking General question same as we know the thermal overload setting of motor should be 125% of Full load current

 

[ScottyUK]

I'm pretty conservative (small 'c') when it comes to protecting equipment and I would generally set a motor relay to pick up just a little above full load current, maybe 105% - 110% of rated current. Very few motors are required to deliver their nameplate rating to the load, so in practice setting the protection tight doesn't generally have any detrimental effect on motor operation. There's no way I would set pickup as high as 150%, modern motors just don't have that much margin built into them and your relay will sit passively watching while your motor burns.

 

[afzumannu]

What should be the time delay

 

[afzumannu]

Please I am waiting someone should help me

 

[edison123]

afzumannu

What jraef said.

Muthu

http://www.edison.co.in

 

[waross]

Google is your friend.
Link
The Thermal overload protection (49) described on page 9 may be a better option than inverse time for motor protection.



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

 

[waross]

"
afzumannu (Electrical)(OP)
What should be the time delay "
When using inverse time, the time delay is inversely proportional to the overcurrent.
When using inverse time, chose a curve that will allow the first quarter cycle inrush without tripping and that will allow the normal starting surge without tripping.
But best, ask Siemens.
To recap:
Good: Inverse time.
Better: Thermal Overload Protection. (This models the motor heating and has a memory of motor heat from recent running.)
Best: Ask Siemens.

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

 

[Parchie]

Your controller falls under Class 8198 (~150kW), the allowed overload factor is 1.15. These motors have service factors of 1.0.

 

[ScottyUK]

Based on the voltages and metric measurements in the OP I doubt the standards from the ANSI world will apply here. IEC motors don't have a service factor.

 

[marks1080]

afzumannu I'm not sure how much protection knowledge or experience you have, but as a professional engineer I take issue with you coming onto a site like this and basically asking professional engineers, who would normally be expected to make a paycheck off doing this kind of work (that obviously requires specialized talent) to give you this work for free.

Folks here are more than happy to help you understand. I don't think many folks here are happy to give you free information that is more involved than you realize.

You want someone to give you an answer like "1500 Amps primary" or whatever. That's not going to happen. You will get help here, but not a free ride.

 

[afzumannu]

Based on study I will set the definite value 120% of rated current, but I need the the time setting...because I don't want motor to trip unnecessary during starting time. All we know motor starting current 6 to 8 times of rated current.if I put 5 sec may be it will trip in starting because pick value and set time achieved during starting.. .now all you guys understand my problem...once again what should be time setting

 

[Parchie]

Perhaps you are confused about the "definite time" characteristics of a relay and the inverse-definite minimum time" (IDMT).
On a definite time relay, the relay trips instantly the moment the trip setting is breached.
The greater the current, the faster the OCP trips on an "IDMT" relay. That said, you will know the trip time if you refer to the relay's TCC curve at some chosen trip setting.