Islanding in power system can be intentional or unintentional. In the past most of the methods were developed for the phenomenon of unintentional islanding. Recently as the distributed generator (DG) sources are able to control voltage and frequency in the islanded part, the phenomenon of unintentional islanded is not common. If the autonomous operation of sources or intentional islanding is desired, then a fast islanding detection technique is necessary. The main philosophy of detecting an islanding situation is to monitor the DG output parameters and system parameters to decide whether or not an islanding situation has occurred from change in the parameters. islanding detection techniques can be classified as remote techniques and local techniques, and local techniques can be divided into passive methods, active methods and hybrid methods. In this paper, several remote and local techniques (passive, active, and hybrid methods) for islanding detection are briefly described. The advantage and limitation of each technique are also introduced. Meanwhile, the comparison of these methods is also discussed.

A 20-year-old male with Marfans syndrome complained of gradual progressive diminution of vision in the right eye (RE) for 6 months. A slit-lamp examination revealed bilateral inferior lenticular coloboma with cataractous changes involving the visual axis in RE. The patient underwent phacoemulsification with a foldable intraocular lens and capsular tension ring implantation in view of zonular dehiscence in the RE. Other eye was managed conservatively.

A 56-year-old male underwent cardiac balloon angioplasty for coronary artery stenosis and after 1 week presented with sudden painless diminution of vision in the left eye. On examination, the best-corrected visual acuity was 6/6, and hand movement was close to the face in right and left eye, respectively. The detailed evaluation revealed hemicentral retinal artery occlusion in the left eye, whereas the right was within normal limits. The patient was treated with anti-glaucoma medication and referred to a cardiologist for further evaluation and treatment. The patient underwent left internal carotid artery balloon angioplasty and stenting. At 2 weeks follow-up, reperfusion was noted in the left eye.