The mysterious voltage transformer

[m.s.j]

The mysterious voltage transformer

Voltage transformers are occasionally used to adapt voltage protective relays and instruments with nominal voltage of main circuit in low voltage switchgears.

In an electrical panel test program an interesting thing was observed. In the panel a three phase voltage transformer with following technical characteristics was used to adapt one 110 V AC under voltage relay with main bus bar voltage.

Voltage Ratio: 380/110 V

Connection: YnYn

Rated power: 60 VA

Construction: Core type

Accuracy class: 3P

The under voltage relay was three phase and microprocessor base made by an authentic company.

The acceptance tests on the individual relay were done successfully, but the under voltage relay in combination with voltage transformer didn’t have suitable reflection against actual one phase under voltage in primary system that was simulated by removing one of three phase fuses in primary side of the voltage transformer.(Really, no under voltage was observed

by the relay.) All wire interconnections and related circuits also voltage transformer was rechecked again and every thing was very well. The relevant test men couldn't explain the reason of behavior of circuit. It seemed that interface circuits or devices didn’t work correctly.

How can you explain the reason of non activity of that protection system against primary under voltage?

FOR SIMILAR DISCUSSION PLEASE REFER TO htt://electrical-riddles.blogfa.com

[Brian G]

M.S.J.,

I don't know what kind of electrical panel your testing was done on, but it isn't anything like what we're accustomed to seeing in our work. I doubt if anyone will respond.

Brian G.

[Jim Katen]

Originally posted by m.s.j

The mysterious voltage transformer

Voltage transformers are occasionally used to adapt voltage protective relays and instruments with nominal voltage of main circuit in low voltage switchgears.

In an electrical panel test program an interesting thing was observed. In the panel a three phase voltage transformer with following technical characteristics was used to adapt one 110 V AC under voltage relay with main bus bar voltage.

Voltage Ratio: 380/110 V

Connection: YnYn

Rated power: 60 VA

Construction: Core type

Accuracy class: 3P

The under voltage relay was three phase and microprocessor base made by an authentic company.

The acceptance tests on the individual relay were done successfully, but the under voltage relay in combination with voltage transformer didn’t have suitable reflection against actual one phase under voltage in primary system that was simulated by removing one of three phase fuses in primary side of the voltage transformer.(Really, no under voltage was observed

by the relay.) All wire interconnections and related circuits also voltage transformer was rechecked again and every thing was very well. The relevant test men couldn't explain the reason of behavior of circuit. It seemed that interface circuits or devices didn’t work correctly.

How can you explain the reason of non activity of that protection system against primary under voltage?

FOR SIMILAR DISCUSSION PLEASE REFER TO htt://electrical-riddles.blogfa.com

You tried to create an under-voltage condition by removing the fuse from one leg on the primary side of the transformer.

Did anyone check to see that this actually created an under-voltage condition on the secondary side?

Did any try to recreate the problem with a different relay?

Are you an engineering student who's trying to cheat on his test by posting the question here?

- Jim Katen, Oregon

[kurt]

Originally posted by ozofprev

Am I the only one who believes this is a joke? We are answering questions about batteries and transformers for someone in Iran? What's next - remote garage door opener theory?

Might be. One never knows who's going to show up on an internet forum asking honest questions.

Not that the information isn't available freely on the Internet, but don't we look stupid taking these questions at face value???

Not really. At least, not yet. If there's a punch line coming, it's not going to be a sonic boom. Seems relatively low level trolling, if it is such.

Maybe he dreamed of home inspecting, and while following his vision, simply stumbled in the door(?)......

I can't always tell unless I can see the white's of their eyes.

[ozofprev]

Pruned myself.[]

[hausdok]

m.s.j.,

I don't know whether you've figured it out yet, but this is a site used by professional home inspectors. You're not likely to find very many here who're prepared to discuss electrical theory at the level of those who participate in the discussions on your website.

Home inspectors, in general, don't need to have such an in-depth understanding of electrical issues as the questions posed on your website. There are some exceptions. A small number of inspectors are former engineers or electricians; one I know of is even an ex-rocket scientist, but most of us have only a rudimentary understanding of electricity - about on the level of what one learns in a high school science class.

ONE TEAM - ONE FIGHT!!!

Mike O'Handley, Editor

[m.s.j]

Originally posted by hausdok

m.s.j.,

I don't know whether you've figured it out yet, but this is a site used by professional home inspectors. You're not likely to find very many here who're prepared to discuss electrical theory at the level of those who participate in the discussions on your website.

Home inspectors, in general, don't need to have such an in-depth understanding of electrical issues as the questions posed on your website. There are some exceptions. A small number of inspectors are former engineers or electricians; one I know of is even an ex-rocket scientist, but most of us have only a rudimentary understanding of electricity - about on the level of what one learns in a high school science class.

ONE TEAM - ONE FIGHT!!!

Mike O'Handley, Editor

Thank you

Goodby