Electronic System Protection
Specialist contractors installation of surge protection devices partner to Furse, Thomas and Betts Nottingham
Questions & Answers
Q. What are "spikes" and "surges"?
A. The words "spike" and "surge" are often used to describe transient overvoltages: "very short duration increase in voltage between two or more conductors". Transient overvoltage (sometimes shortened to transient) is the more accurate and technically correct term. "Surge" should be used with caution as it is sometimes used to refer to sustained overvoltage.
Q. What are the causes of transient overvoltages?
A. Transient overvoltages are caused by the secondary effects of lightning or by electrical switching events.
Q. I've got a lightning protection system, why do I need Electronic Systems Protection?
A. A Lightning conductor systems are intended to protect the fabric of the building only. Specific protection against the secondary effects of lightning is required for the electronic contents of the building
Q. How does lightning cause transient overvoltages?
A. The secondary effects of lightning cause transient overvoltages in two main ways: resistive coupling and inductive coupling.
Resistively coupled transients are caused by differences in potential between two connected earths. Lightning strikes to, or near to a building will cause the local earth to rise to a very high potential. Equipment within the building will be referenced to this earth and so will be at the same high potential. Other buildings, even neighbouring ones, will be at a much lower potential. Often these two earths, or equipment referenced to them, are linked by a power or (conducting) data communications line causing the difference in potential to be shared between the line and the equipment at each end. The voltage present across the components of the equipment is a transient overvoltage. See Figure 1. Inductively coupled transients are caused by electromagnetic pick-up. Lightning discharges create an electromagnetic field. If a power or conducting data communications line passes through this EM field then a portion of its voltage can be picked up by, or induced onto, the line. As before this transient overvoltage will appear across components within the equipment. See figure 2.
Q. Does lightning have to hit a building to cause transient overvoltage?
A. No. In fact the vast majority of transients, which are caused by lightning, are not the result of direct strikes.
Q. Is it true that underground cables will not be affected by the secondary effects of lightning?
A. No. underground cables are just as susceptible to resistively coupled transients as overground cables are. However underground cables are unlikely to be affected by the usually smaller inductively coupled transients.
Q. Is it true that lightning never strikes twice in the same place?
A. No. Multiple strikes, within a matter of months, to the same site are not uncommon.
Q. How does electrical switching cause transient overvoltages?
A. Current flowing through a conductor creates a magnetic field in which energy is stored. When equipment is switched off, the current ceases to flow and so the stored energy is released - manifesting itself as a transient overvoltage.
Q. I've got an uninterruptible Power Supply - do I still need Electronics system Protection?
A. The short answer is yes. Many UPS systems don't incorporate any transient overvoltage protection At all. Those UPS that do calm to provide transient overvoltage protection often incorporate a small filter. This provides protection against quite low level transients but not against the larger transients which cause damage. Furthermore many UPS systems have a bypass connection which operates during faults, overloads, UPS or routine maintenance- leaving equipment connected to a raw power supply. The installation of Electronic Systems Protection on the supply to the UPS will ensure the equipment fed by the UPS is protected against all transient overvoltages It will also protect the UPS and its solid state circuitry against damage and degradation caused by transient overvoltages.
High Level Maintenance
Tall buildings, structures, shafts and flare-stacks (above and below ground) require specialised access. This may be for inspection, alteration or maintenance purposes. Due to the awkwardness or heights of the inspection works the client may not be...
Lightning Protection
Visit our new lightning protection site. Design, Installation, Certification, Maintenance & Annual Testing. Work carried out on: Churches & Historic Buildings, Industrial Factories and Plant, Military & Institutional Establishments,...
Restoration, Consolidation and Conservation
Rope Access, Vegetation Control & Masonry Conservation on Ancient Monuments, Churched, Listed and Historic Buildings, eg. Bolton Priory and Barden Tower, Marsden Cliffs. Ladder and Rope Access Surveys of High Structures (+video, CCTV,...
