Self Destruct - (Why no accidental destructions)?

[Deks]

EPS conduits run throughout the ship (EPS grid).
They are conducting plasma if I recall.

While the self-destruct of the 24th century frequently begins with the Warp core... the 23rd century SF may have did it differently... by overloading the EPS grid instead... however, as opposed to a single fully synced blowup, you get a series of reactions.

At any rate, its also possible that the 24th century can alternate between a Warp core overload and an EPS grid overload (depending on which one is chosen).
We saw in the early season of VOY (Deadlock episode) that the explosions began in the upper section of Voyager... not engineering - in this case, Janeway may have opted for the explosions to start at the top of Voyager and work their way down because the Vidiian ship was along Voyager's Z axis (to maximize damage and finish it off with a massive Warp core explosion).

The USS Equinox did explode 'correctly' (visually that is).

 

[Deks]

There are many ways to destroy a ship, actually.
* Fly into star.
* Fly into black hole.
* Fly into pretty much anything if it's going fast enough.
* Seperate. Fly star drive into saucer section.
* Accelerate out of control.
* Warp core breach.
* Rupture antimatter container.
* Violent collapse of warp field.
* Cause all consoles to explode at once.
* ?????

Fly into a star - Multiphasic shields (at least offer protection as far the Sun's corona is concerned) - but should be sufficient (unless the ship ends up in the Q continuum by mistake).

Fly into a black hole - VOY got out of a singularity before... twice... meanwhile the hunter ships even got their nacelles torn off by the sheer force of the gravity on the second occasion while Voyager was intact - we also don't EXACTLY know if flying into a black hole would destroy the ship... who knows what kind of automated defenses exist to prevent that.

Fly into pretty much anything if its going fast enough - probably not, because this will depend on the size/mass of the object the ship flies into... so some aspects of the vessel, if not a major part could potentially survive.

Separate. Fly star drive into saucer section - this one has much higher chances of success.

Accelerate out of control - eh, not necessarily most reliable because it can generally be controlled with more power being diverted into structural integrity fields... but could do if you accelerate PAST the ship's maximum sustainable speed and manage to MAINTAIN that speed.

Warp core breach - should work...if the self-destruct mechanism is working... but breaching antimatter pods or disrupting the containment field should also do the trick.

Rupture antimatter container - high degree of success.

Violent collapse of Warp field - possible but not 100% guaranteed to destroy the ship. Ships were violently knocked out of Warp before without major issues - I guess it would depend on HOW the field is collapsed.

Cause all consoles to explode at once - not guaranteed to do anything except prevent the crew from interacting with the ship's controlls physically.. .there's still computer verbal interface to consider, and what about the crew not anywhere near any console?

???? - sky is the limit?