# three phase fault detection system using a microprocessor based relay

#### rihdus

Joined Jul 20, 2017
2
Trying a project for fault detection in a three phase system using a microprocessor based relay and tripping the system using a contactor whenever the fault occurs. I have got some ideas on that but not fully impressed by that if anyone has an idea on this i am eagerly waiting for his idea to follow thank you

Joined Jul 18, 2013
20,021
Do you mean over-current in any phase? If so, it is done very simply now by a over load sensor in each phase, usually now attached to the bottom of the contactor.
Why the complexity of the Micro?
There are contacts on the O/L for sensing a trip condition that could be used.
Max.

#### KeepItSimpleStupid

Joined Mar 4, 2014
3,897
Many years ago, I discovered Symcomm. e.g. http://www.littelfuse.com/~/media/protection-relays/datasheets/voltage-monitors/littelfuse_protectionrelays_102a_datasheet.pdf

The ones I used for for 208/240 systems with an auto-restart adjustable delay. The motor starters were wired with an on/off auto mode. So, they would drop out or stay out and/or drop out and re-start. The application was vacuum pumps. One box was also single phase 208.

I never had a moments trouble with them. They were $100-$150. The building lost a phase and all sort of stuff died. It was money well spent.
Some stuff would cost $5000.00 USD to fix and others$10,000.00. Ventilation fans that just needed a new motor we left alone. There were about 40 of them. Production stuff mattered.

Near the end of my career, I did replace one motor starter with a solid state variety. I still liked the Symcomm options and kept it in place.

So, your looking at phase reversal, phase imbalance and, I believe, phase coherence. It's all done with voltage. I always added the re-start delay option.

#### rihdus

Joined Jul 20, 2017
2
A microprocessor based system is the requirement i need for my purpose . This is the block diagram of my system. Could you recommend me a book for three phase fault detection system using a over current relay. Thank you in advance

#### Attachments

• 152.3 KB Views: 12

Joined Jul 18, 2013
20,021
The O/L option detects over current if that is all you need as per your OP.
You could feed the detected contact closure into a micro for processing.
Max.

#### KeepItSimpleStupid

Joined Mar 4, 2014
3,897

Joined Jul 18, 2013
20,021
Typically these contactor O/L's do not remove power themselves, they often have a N.C. and a N.O. contact fitted and in a hardwired situation, on fault or O/L, the N.C. contact opens the coil circuit.
The N.O. can be used to monitor and report the O/L condition, e.g. input into a PLC or Alarm system etc,
Max.

#### Sudhir Kharl

Joined Apr 28, 2018
1
can i get the arduino code of this project. now i am using a arduino instead of a microprocerssor chip so, if you could provide me with the code i would be thankful.

Joined Jul 18, 2013
20,021
can i get the arduino code of this project. now i am using a arduino instead of a microprocerssor chip so, if you could provide me with the code i would be thankful.
What project?
Besides I don't use Arduino myself, just Picmicro.
As already stated, the O/L option would be the easiest but you would need the type that has Both N.O. and N.C. contacts, one to interlock the contactor coil and the other (N.O) to monitor via the μp as a simple fault when closed.
Max.