Many problems are evident to the trained eye. Look at all of the leads to appliances. These should just have the outer insulation revealing. If that is damaged, the guide should be shortened, cutting out the damaged piece, or replaced entirely.
Damage generally occurs at either end of the guide. If the lead doesn’t enter the plug, the plug needs to be rewired (see arrows); likewise in the other end.
If the guide has been damaged in the middle (a frequent occurrence with vacuum cleaner, hedge trimmers, lawn mowers, etc.), the guide should be replaced or reconnected with a suitable lead connector (two or three core based on if the guide is earthed or not), which has appropriate cable grips for the lead going in and out. Using ‘choc. Cubes’ or insulation tape for reconnecting leads isn’t advised. You can also see more advantages of Relays for home appliances and office equipment through online websites.
Any damage to the casing of appliances should be mended. Live components should be well shielded from the exterior casing, and when this contains any alloy, generally the appliance needs to be earthed. (Many old tables and floor lamps, especially homemade ones, aren’t earthed even when they have metal components.
These should be re-wired with 3 core cable.) It’s allowed for ‘double insulated’ products do not have a ground (even some with metal external parts). In this case, there have to be at least two layers of insulation between live parts and the exterior. If the product was purchased from a reputable trader in the past couple of decades and isn’t earthed, it’s most likely OK.
Lots of men and women think seeing sparks at switches (more commonly in the dark) suggests an issue, but that is normal in most cases. Special switches can be found which don’t ignite, but these are costly and only necessary in environments where there are inflammable substances around.