How to test SEL 121G 4

[22574]

Hi All,

We have a SEL 121G for lab use, but my problem is I dont
how to test it, does anybody have test procedures on this relay using doble f6150?

 

[Eleceng01]

You might want to start by contacting SEL - they are good about providing assistance for things such as this. This is an older relay that I haven't seen for some time.

 

[oldfieldguy]

22574--

The SEL 121 is a rather complex little mess to test, but in a lab setting, it will provide a lot of valuable insight into the workings of various elements of a distance relaying scheme.

With the Doble 6150, you should be able to locate test programs that automate most of the testing, but again speaking of a lab environment, you might be better served learning how to set up the voltages, currents and phase angles to manually test the relay. This will give you a whole lot better understanding of the relay's function and ultimately a better understanding of how to handle problems and investigations.

Not implying that YOU fit the bill, but in my opinion, connecting a bunch of wires to a relay and punching "run" on somebody else's automated test program does not make for a good engineer or technician.

old field guy

 

[davidbeach]

connecting a bunch of wires to a relay and punching "run" on somebody else's automated test program does not make for a good engineer or technician

Hear! Hear!

 

[Eleceng01]

oldfieldguy - GREAT observation. I also am not implying that 22574 fits the bill, but I did work at a maintenance company that had "relay technicians" who had no idea of what the test was really doing for the more complicated tests. If it was set-up wrong or the relay did not operate as expected (i.e. pass) they were clueless about the cause.

No better learning than having to bang your head against the wall until you figure it out (especially in a lab)!

Eleceng01 (with many bruises to the forehead)

 

[slavag]

Hi Folks.
In additional to OldFieldGuy and Eleceng01 posts, I would like add: 22574, don't learn testing of relay SEL121G, learn test protective functions. Don't learn Double F6150( BTW according to my partners is excellent tester), learn what you need inject for right relay operation and don't inject Z---> please inject U and I and phase angle between.
Regards and Good Luck.
Slava

 

[Eleceng01]

Great points Slavag!

 

[subtech]

A simple sign in procedure at the SEL website will provide you with access to not only a user manual for the 121, but a wealth of related info as well..

http://www.selinc.com

 

[521AB]

... Hi Folks.
In additional to OldFieldGuy and Eleceng01 posts, I would like add: 22574, don't learn testing of relay SEL121G, learn test protective functions. Don't learn Double F6150( BTW according to my partners is excellent tester), learn what you need inject for right relay operation and don't inject Z---> please inject U and I and phase angle between.
Regards and Good Luck.
Slava...

COMPLETELY IN AGREEMENT.
GOOD POST SLAVAG!
A fault is represented by voltages and currents. NOT impedance. Automatic test plans are not good to understand the relays.

And then again.... we can go to my old post: what does TEST mean?
I am fully convinced that:

- Commissioning/routine tests of the relays must be done according to recommendation in relay manufacturer, and NOT acording recommendations of relay test sets. Only the manufacturer knows how the relay works, and only the manufacturer can tell you how to test it in order to understand that it is working fine.

-Performance tests can be done "as you want", not considering how the relay works. But then you must make sure that your tests are realistic tests, because if somenthing doesn't work, you must be able to give a good and significative report to the manufactuer without that you imply 3 persons working for you to discover you are testing the relay OUTSIDE of its application, which is protection of power systems and not just response to some currents and voltages. Testing the characteristic, is not a performance test.

 

[DTR2011]

This is a good relay to see how far things have come. If I recall correctly, old SEL relays use hexidecimal settings and masks. I had mu arse handed to me years ago in this application.

I believe the older SEL manuals do a good job at helping the tester through some basic examples. Not picking on SEL, but most new manuals do not give much in explaination of what to test, how to tests,etc. The old Basler manuals were very helpful as well.

Volts, amps and phase angle is a very good approach. Some test set SW has the ability to show both that ,sequence components and impedance plane in vector diagrams.

Oh, how I wish I had that years ago in school rather than fortran programs and a mainframe computer.