This paper presents the results of an experimental and theoretical study of the stability and protection of small test coil assemblies wound with second-generation (2G) high-temperature superconducting (HTS) wires. The study, conducted as a part of the efforts to improve the design and applicability of YBCO wire technology to real-life power devices, such as magnets, focused on two specific issues: 1) internal voltage developed within the winding resulting from a spatially nonuniform normal zone in a coil that is effectively short-circuited across its terminals; and 2) detection of a localized ldquohot spotrdquo with acoustic emission (AE) signals to complement the usual resistive voltage technique. Each test coil assembly, a stack of four single YBCO pancakes electrically connected in series and shunted by a ldquopersistent-moderdquo switch, simulated a power-supply driven magnet a moment after a quench zone appeared within the winding. A heater was incorporated into each pancake coil to drive 25% (one pancake), 50%, 75%, or 100% (four pancakes) of the test coil assembly. Measured internal voltages arising from different quench sizes and distributions are compared with the results of the simulation. ldquoHot-spotrdquo induced AE signals are also presented on a single coil to determine if AE signals may be useful to facilitate the early detection of a normal zone in HTS windings.