Wye vs Delta Connection in Current Transformer (CT) Secondaries: Pros and Cons?

Hi everyone.Can anyone help me to understand the difference between a wye and delta connection in CT's secondaries?
Being honest, I've never seen a delta connection in a CT. Can anyone tell me the pros and cons of these connections (once again, in a CT) ?Thank you.

Sérgio...  I'm not really a power guy but no one else has replied, so thought I'd have a go.  I work for an electricity distributor so have seen a few CTs around work (though I'm not on that side work-wise).  There are a lot of good resources on the net - try googling "delta connected current transformers".  There are some you tube tutorials (like this one) and a PDF which goes into the theory of CTs in some detail.  But what they are short on is WHY you would use delta instead of Y connection.  It does seem to offer some advantages in driving protection relays (which is the primary purpose of a CT in electricity networks) but you may get more out of it than me in this regard - my knowledge of protection is pretty basic.   There's also this PDF which may have a bit more on the subject.  I will try asking some of the substation technicians at work about this and if I get any gems of knowledge out of them I will post them here.

I'm not a power engineer either but I work for a company that designs equipment for the power industry.
Here's my thoughts from the point of view of the protection relay. Almost all protection relays have two connections for each CT (current in and return) so in that sense it doesn't matter if the CTs are in a Wye or Delta configuration.On the other hand, the relay needs to measure the currents as accurately as possible to perform correctly. If you connect the CTs in a Delta configuration, some of the current that you are trying to measure gets diverted into the delta which will change the characteristics of the current. I suspect this is why you never see a delta connection in a CT secondary.

Elizabeth - from some of the stuff I posted above - particularly the you tube tutorials which are very good on HOW but not much good on WHY - they talk about phase differences and stuff and I think if a transformer is wired delta input, Y output there may be advantages to using a delta configuration on the CTs.  But this is way out of my area of expertise.  Unfortunately I'm on leave at the moment so my asking the substation techies at work will have to wait till next week.

Thank you all.
I've read many papers and articles (and watched the videos that David mentioned). These documents go through the theory and the behavior of currents in the secondary of the CTs but I just couldn't see a situation where I would use a delta connection.
After researching a lot and posting in different foruns, I found an answer:
Basically a delta connection in CTs secondaries is used just in a protection configuration of a power transformer connected in delta / wye or vice versa. In this case the CTs are connected in wye / delta just to equalize the phase displacement between HV and LV windings and provide the correct current phase angles to the relay (87 - ANSI).
Nowadays, however, the relays (IED's) are able to perform such correction and CTs in delta are even more rare to find.
According to engineers who I talked to, that's the only situation that we'll see such connection. Once again, thank you all who replied to my question.

Sérgio...nice work.  Good to see that I was not too far off in my 2nd comment.  I do know that modern protection systems need VERY fast responses which is why phase may be critical.Cheers // David

Delta connected CTs filter out the zero sequence currents. They are essentially a zero sequence trap where the zero sequence current circulates inside the delta and cannot come out  to the protection relays. As you have mentioned they are used with older 87 relays. While they do match the phase difference they also filter out the zero sequence current.
They can also be used to protect zig-zag  transformers from internal faults by using an overcurrent relay.Please seehttp://rpa.energy.mn/wp-content/uploads/2016/07/network-protection-and-automation-guide-book.pdf
Look at Figure 16:18

" need VERY fast responses which is why phase may be critical." - phase is critical for stability - if you get your phase correction wrong you won't be able to turn on the transformer. It will "see" a differential current and trip.