The issue is fundamentally the difference between phrases (where noun1 is a verbal noun):
noun1
of noun2
(A verbal noun being part of an Entity. Relatively more noun-like.)
noun1
on noun2
(A verbal noun applied or directed to an Entity. Relatively more verb-like)
In this case, "of" is being used as follows:
Define of: (Oxford Dictionary)
6.) Expressing the relationship between an abstract concept having a verb-like meaning and a noun denoting the subject of the underlying verb:
the opinion of the directors
the decision of the County Council
6.1) Where the second noun denotes the object of the underlying verb:
the murder of two boys
payment of his debts
an admirer of Dickens
And "on" is used as follows:
Define on: (Oxford Dictionary)
5.) Having (the thing mentioned) as a target, aim, or focus:
five air raids on Schweinfurt
thousands marching on Washington
her eyes were fixed on his dark profile
Examples of the noun-like use of of:
- X of Y.
- War of 1812.
- Development of Character.
- Analysis of Variance.
- The Battle of Gettysburg. (In 1863, in the Battle of Gettysburg, General Lee's initial attack on Union forces appeared to be a sign of success.)
- Act of Kindness. (This is provided to show that not all forms follow this pattern. In this case, "Kindness" is describing the type of "Act". "Act" is not a verbal property/relation of "Kindness".)
Examples of the verb-like use of on:
- X on Y.
- War on Terror.
- Debate on Immigration.
- Effects on Tourism.
- Agreement on Terms.
There are not as many cases where you can use both "of" and "on". Consider the following which further demonstrates the differences:
- Construction of the new tower will begin January of next year. Focus is construction of the the tower as a whole.
Construction on the new tower will begin January of next year. Focus is on the construction as an activity performed to create the building.
payment of his debts. This phrase is natural when discussing the full payment. Payment is like a property of his debt, resulting in a noun-like meaning.
- payment on his debts. This might be a partial payment. Payment is an action applied to his debt, resulting in a verb-like meaning.
When you can use both "on" or "of", the difference can often be quite small, especially when seen in isolation. However, a skilled writer might make a decision
on one over the other
for subtle rhetoric, style, or other distinctions
of meaning
.
Note: @user42307's fine answer provides a great example of what I mean by a skilled writer choosing a single word for rhetorical purposes!
X at Y means X is a place, and Y is close enough to X that if we wanted to find Y, we'd first have to find X. A place is large amount of space where things can be built or where things can happen.
X in Y means X surrounds Y, either physically or logically.
Buildings surround you, so when you enter a building, you are said to be in it, and can say you work in a building.
Businesses sometimes aren't just a building or room in a building, they have a campus, etc. Or maybe they have multiple buildings. So then they can be elevated to "place status" and therefore you use at.
I work in a kindergarten.
You're saying there's a room or building labeled "kindergarten" and that's where you work. If it's part of a school or greater institution, this is proper to say.
I work at a kindergarten.
You're saying there's a place called a kindergarten and you work there. This gives the impression it's a separate building, with it's own parking lot, etc.
Best Answer
This is a great question!
The first and third options - "in a power plant" and "at a power plant" - are both correct for this specific example of work, so long as you mean "doing some job inside an existing power plant".
The second option "on the power plant" would mean something different - e.g. that you are an engineer or labourer involved with the construction of a new power plant. For instance:
However, in other cases, the "on" preposition will be appropriate. The general principle is that:
The following examples illustrate.
Examples where "in" or "at" are (largely) interchangeable
Note that in these examples, the "at" preposition will generally be more appropriate where the workplace is a specific workplace (preceded by "the").
Examples where "on" is essential
Examples where "on" or "at" are largely interchangeable
Examples where "at" is essential