Even it sounds a little bit odd the protection of professional and home equipment against current rushes and lightning has its own philosophy. Its correct comprehension by the producer as well as by the user of the protection devices is equally important. We call your attention that the direct case in point is the equipment protection and indirectly is the human health and life. For example, after a current rush there could be generated a dangerous voltage in the appliance’s body. By the protection, you could eliminate the risk of generating such voltage. In order to be more useful for that topic, we shall soon publish a series of advises how to behave when lightning and in cases of injuries by electricity.
     The protection philosophy has two parts – technical and financial. We shall try here below to explain the technical part so to be easy understandable even by non-specialists.
     The easiest way to protect an appliance against high voltage is to switch it immediately off when the voltage begins to exceed its standard values. It could be implemented by a relay. The necessary break time of a relay is of the order of hundredths of the second. In most cases, the time during which a peak generated by a lightning or a current rush reaches tenfold and even hundred-fold higher value than the standard is in the order of thousandths of the second. That is 10 times quicker than the time necessary to a relay to cut out. All said shows that the described method of protection is applicable only for slow voltage changes. Most of the electronic appliances have a protection exactly of that kind and a lot of people are mistaken that it would help while arising of over voltage generated by current rushes, lightning, etc.
     To solve the problem surge protectors are so constructed that they instantly discharge the surplus energy of the appliances where it is dispersed without causing damages or at worst to be damaged only the protection device. It is done by quickly acting components that resist great loadings for a short period, and while the voltage is in standard values they do not disturb the normal work of the appliance and do not consume electricity. Such types of components are gas discharge tube surge arresters, metal-oxide varistors, special diodes, etc. Sono Ltd uses for its surge protectors gas arresters produced by the Japanese company “Sankosha”, metal-oxide varistors – by “Siemens”, “Uppermost”, and others, which guarantee their protection quality.
With all that the technical question is not settled but the practical decisions are problems of the specialists, so we tackle them seriously.
     Now we would like to bring the other side of the over voltage-protection philosophy – the financial – to your notice. The most essential part of that philosophy is the correlation protection capacity – price. We are very often asked “Do you guarantee 100% that if I use your protectors, my appliances will not be damaged by a current rush or lighting?” Of course, we would like to and could answer positively to that question, but the price of such 100% protectors would exceed several times the price of the protected equipment. Would you buy it yourself?
The world wide experience which we carefully studied shows that the reasonable combination is when the protection device’s price is between 5% and 10% of the protected appliance’s price, and the protection to be effective in the range of 70-90% of the cases of current rushes. Sono Ltd adopted that viewpoint for the production of protection devices. Of course, if there is an interest by our customers, we can create more “luxurious” protectors, respectively with higher efficiency and price. A protection efficiency over 95% leads to considerable raising the costs, so it is applied only to projects an equipment with strategic values.
The above mentioned percents are results of many years researches of the biggest companies in the frequency and strength of the current rushes, generated by lightning, failures, etc., and the technological abilities for production of protection components.