AC power quality and surge protectors

Since years the Surge Protective Devices (SPD) are widely used to protect the sensitive equipment connected to the AC distribution network against lightning or switching surge voltages. The international standards for SPDs are now widely spread and make the new generation of AC surge protectors more efficient and more secure. But an important issue is not really described on the standards and even on the related guides for surge protection application: what is the real influence of the AC surge protector on the AC network, especially during their operation? As we know, the Power Quality (PQ) is a key point for the process continuity, the safety and even for the life expectancy of the sensitive devices connected to the AC distribution network: during their operation on surges, the surge protectors could generate some phenomena which could create disturbances or troubles on the AC network. Because the AC surge protectors are from different technologies and because the AC networks could have several configurations, many cases are possible, even the worse... Market analysis shows sometimes a low confidence of the end user in the surge protection, not because he thinks it is not efficient, but because he supposes the use of SPD could bring extra disturbances on his installation. For this reason, an in depth information about the real interaction would be useful.