Quasi-neutrality is violated by, for example, charged particle beams (jets) and double layers, though the containing plasma as a whole will still maintain charge neutrality, but local regions may not. [see depolar, neutral]
The magnitude of the size of the violation of quasi-neutrality is typically a few 10s times the Debye length. In other words, if the Debye length for a particular plasma is about 1cm, then charge separation regions around 10 - 20 cm may occur.
But note that while the distance between two charge separation regions may be quite small, the overall size of each each region may be enormous. For example, the jet emerging from the galaxy M87, has been estimated to be 5400 light-years long. http://www.plasma-universe.com/index.php/Quasi-neutrality
3.14 - Vortex Theory of Atomic Motions 13.04 - Atomic Subdivision Atomic Atomic Cluster X-Ray Emission Atomic Clusters Atomic Force atomic mass atomic number atomic theory atomic triplet atomic weight Debye Continuum Debye length Debye length in a plasma Debye length in an electrolyte Debye, Peter Debye Sphere diatomic Etheric Orbital Rotations Figure 13.06 - Atomic Subdivision Force-Atomic Formation of Atomic Clusters Inert Gas Interaction of Intense Laser Pulses with Atomic Clusters - Measurements of Ion Emission Simulations and Applications TD69.pdf InterAtomic Laser Cluster Interactions Law of Atomic Dissociation Law of Atomic Pitch Law of Oscillating Atomic Substances Law of Pitch of Atomic Oscillation Law of Variation of Atomic Oscillation by Electricity Law of Variation of Atomic Oscillation by Sono-thermism Law of Variation of Atomic Oscillation by Temperature Law of Variation of Atomic Pitch by Electricity and Magnetism Law of Variation of Atomic Pitch by Rad-energy Law of Variation of Atomic Pitch by Temperature Law of Variation of Pitch of Atomic Oscillation by Pressure Models of Laser Cluster Interactions monatomic Nanoplasma Plasma Plasma holes Quasi-neutrality Quasi-neutrality and Debye length Specific Heat Stria Violation of quasi-neutrality