Differences between TVS diode and Zener diodes, in diagrams and in practice?
The reason the same symbol is sometimes used for TVS diodes (Transorbs) and Zeners, is a Transorb has a lot in common with a Zener. An ideal Zener and an Ideal TVS-diode would be indistinguishable in their characteristics. This leads to ... laziness in library management (or ignorance) and the same symbol is used.
Regulator Zeners and TVS-Zener diodes differ in aspects of their construction to facilitate either higher continuous rating or high pulse capability.
Zener TVS devices are constructed with large area silicon p-n junctions designed to operate in avalanche and handle much higher currents than their cousins, Zener voltage regulator diodes
Only uni-directional TVS diodes are created at wafer level. The bidirectional TVS diodes you can buy are just two such dies packaged in series.
Examples of symbols for some TVS devices:
From your images
- Zener diode unless the part number calls up a TVS
- TVS
- TVS
- Back-to-back Zeners unless the part number calls up two unidirectional TVS
http://www.onsemi.com/pub_link/Collateral/HBD854-D.PDF
Using a TVS diode instead of, or in addition to a MOV for AC line protection?
From a practical point of view (and not so much looking at the symbols), the biggest difference is the pulse handling capability. The underlying effect is the same for all - they are designed for a fairly precise avalanche breakdown (strictly speaking, the Zener effect is for low-ish breakdown voltages, the avalanche breakdown is for higher voltage ratings). However, as you say already, TVS diodes can handle energy pulses far better than Zeners designed for voltage stabilization.
Concerning the symbols: There are also unipolar TVS (surge suppression) diodes, and the symbol is the same as for (voltage stabilization) Zeners. Sometimes, only the application (in the context of the surrounding schematic) or a Mfg./Part number will tell you the whole story...