chknhwk
chknhwk HalfDork
5/17/19 4:39 p.m.

I am currently administering a course for distribution dispatchers and supervisors through a web-based classroom which gives me the ability to pre-build exam/quiz questions.  

Question for anybody in the know - what are some good questions regarding ferroresonance in an electrical utility distribution system?

Hey, I've seen weirder questions answered on here, haha.

Jcamper
Jcamper Reader
5/17/19 5:28 p.m.

Something like “Why are gang operated switches preferred over solid blades?” Choose all that apply. One reason is to mitigate the chances of ferroresonance. 

Could also have something about more likely to have it occur on underground due to increased capacitance, especially higher voltages and larger, unloaded transformers. 

Last one off top of my head, ferroresonance is more likely to be a problem in which, single pole or 3 phase tripping?

jcamper

chknhwk
chknhwk HalfDork
5/17/19 5:36 p.m.

Ugh.  Of all the questions I've come up with I hadn't actually thought of asking the WHY we do what we do.  Instructor fail, LOL.  Thanks!

Already had the other two.  wink

russde
russde New Reader
5/17/19 5:37 p.m.

I read "gang operated switches preferred over solid blades" and thought you were being funny...

chknhwk
chknhwk HalfDork
5/17/19 5:42 p.m.

Why do we prefer operating three phase devices over single phase devices on our distribution system with regards to ferroresonance?

  • It reduces the impedance available at the transformer
  • It reduces the capacitance available at the transformer
  • Three phase devices prevent ferroresonance
  • Less switching steps for the switch person
bluej
bluej UberDork
5/17/19 5:43 p.m.

Came in expecting this to be about the ferrous fluid dampeners in some newer vehicles. 

chknhwk
chknhwk HalfDork
5/17/19 5:45 p.m.

In reply to bluej :

That's a topic for another day.  More electrical here than mechanical...  ;)

chknhwk
chknhwk HalfDork
5/17/19 6:16 p.m.

Just need to find another four questions and I'll be good for now...

Robbie
Robbie UltimaDork
5/17/19 9:16 p.m.

1. Name a large word that normal people have never heard that ryhmes with terroresonance

2. Choose the correct spelling below

A. Feroresonance

B. Ferroresonance

C. Ferorresonance

3. What phemonemon starts with the letter "f" and ends with "erroresonance"?

Robbie
Robbie UltimaDork
5/17/19 9:17 p.m.

4. If you could create a superhero who's superpower was ferroresonance, what would you call him or her?

Robbie
Robbie UltimaDork
5/17/19 9:18 p.m.

5. T/F - the word ferroresonance has 6 syllables.

chknhwk
chknhwk HalfDork
5/18/19 8:37 a.m.

In reply to Robbie :

Nice.  I may (or may not) use those!

Probably not though, haha.

chknhwk
chknhwk HalfDork
5/18/19 9:46 a.m.

Boom, got my fifteen:

 

Question1 pts

 

All of the following are methods of preventing distribution system ferroresonance EXCEPT:

 

 

 

Question1 pts

 

What conditions are necessary to create ferroresonance in the distribution system?

 

 

 

Question1 pts

 

We do not experience ferroresonance on the distribution system in single phase transformers because circulating current doesn't occur between the separate phases.

 

 

 

Question1 pts

 

Ferroresonance in the distribution system is more likely to be experienced during geomagnetic disturbances.

 

 

 

Question1 pts

 

Ferroresonance in the distribution system can occur when an unloaded but energized three phase transformer loses one of the phases feeding it.

 

 

 

Question1 pts

 

We do not commonly experience ferroresonance on the distribution system in three phase transformer partial power situations because:

 

 

 

Question1 pts

 

On the distribution system ferroresonance can cause voltage spikes resulting in insulation and oil damage, causing permanent fault to the transformer.

 

 

 

Question1 pts

 

On the distribution system our three phase transformers are equipped with current limiting fuses (CLFs) to eliminate ferroresonance.

 

 

 

Question1 pts

 

Ferroresonance in the distribution system is more pronounced in single phase transformers than three phase.

 

 

 

Question1 pts

 

S&C transformers installed on our distribution system experience ferroresonance more than Elastimolds.

 

 

 

Question1 pts

 

Why do we prefer operating three phase devices over single phase devices on our distribution system with regards to ferroresonance?

 

 

 

Question1 pts

 

Electrical phenomenon caused when single-pole switching on three phase transformers results in an overvoltage condition in the transformer is known as what?

 

 

 

Question1 pts

 

Diagram A is an example of what electrical phenomenon as two phases of a three phase distribution system are closed to energize a three phase transformer?

Diagram A

 

 

 

Question1 pts

 

We generally do not experience ferroresonance on the distribution system during outages because _______________.

 

 

 

Question1 pts

 

_________________ is a complex nonlinear interaction between the saturation characteristics of the transformers and a capacitance. Most often, the capacitance involved is the internal winding-ground capacitances of the transformers. If there is overhead line or cables connected to the transformer bank, downstream of the open point, the line or cable capacitance can also contribute to the interaction. For __________________ to occur, there must be little or no load on the transformer bank. 

chandler
chandler PowerDork
5/18/19 10:51 a.m.

Hope none of your students are GRMers!

chknhwk
chknhwk HalfDork
5/19/19 5:52 a.m.

In reply to chandler :

I wish they all were!  There is a distinct lack of car people where I work and I feel very alone at times...

AngryCorvair
AngryCorvair MegaDork
5/19/19 6:54 a.m.

If not for recognizing OP’s name, I would have come in here to report thread title that smells of Native American watercraft.

chknhwk
chknhwk HalfDork
5/19/19 8:11 a.m.

In reply to AngryCorvair :

Haha, thanks for not reporting me!  It was a legit question looking for input.

I have to rebuild an entire five month course built by somebody that had no experience in electric utilities.  He did a great job creating a skeleton course but I have about 30 exams that need scrubbed for accuracy and edited to add more questions.  Ferroresonance isn't something widely understood in our industry and we have no training or OPs/OIs/OGs on how to mitigate it.

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