Answer to Question 1
An island occurs when sections of the grid are disconnected from other sections, leaving one small section as the only section that is powered. In this case, the electrical power in the island typically is not strong enough to provide practical power to all customers in that section. Solar photovoltaic panels typically have anti-islanding circuits in them to protect from this condition.
Answer to Question 2
The linear power supply uses a transformer and a four-diode full-wave bridge rectifier to produce the pulsing DC output waveforms. A capacitor is used as a filter to smooth out the DC. The remainder of the circuit contains a regulator and the load. The regulator is the part of the circuit that makes a linear power supply different from the newer switch-mode power supplies. The linear power efficiency is quite poor, in the range of 30 to 40.
Switch-mode power supplies
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