It is unfortunate, but a fact of life, that computers, computer related products, process control and data communications equipment can be damaged by high-voltage surges and spikes. Such power surges and spikes are most often caused by lightning strikes but can also be caused by power cuts, for example load shedding.
A lot can be done as far as protection is concerned. However, it is best to begin by describing the magnitude of the threat from which you need protection.
The first stroke of lightning during a thunderstorm can produce peak currents ranging from 1,000 to 100,000 Amperes with rise times of 1 microsecond. It is hard to conceive of, let alone protect against, such enormous magnitudes. Fortunately, such threats only apply to direct hits on overhead lines. Hopefully, this is a rare phenomenon.
More common is the induced surge on a buried cable. When lightning hits the ground, it creates a ripple effect such as when a drop falls into water. These ripples can travel up to 5km through buried cable and can damage unprotected equipment.
Another cause of damage to equipment comes from power cuts or power surges. This can be described by viewing electricity like a river, flowing into different channels. When a channel is closed, the water must still go somewhere causing some of the other channels to reach peak levels.
Computer equipment has often been damaged by lightning, not because of the absence of a protection device, but because inadequate attention was paid to grounding. Good quality ground connection cannot be emphasized enough.
Conceptually, lightning protection devices are switched to ground. Once a threatening surge is detected, a lightning protection device grounds the incoming signal connection point of the equipment being protected. Thus, redirecting the threatening surge on a path-of-least-resistance (impedance) to ground where it is absorbed.
When providing surge protection for a building, there are three components that need protection:
- The Street Power Distribution Box from Eskom will take the highest spike and therefore one must install the flash/trap. This installation must be executed by a qualified electrician.
- Some buildings have only one Distribution Box where others have one on each floor depending on the size of the building. In each and every one of these DB Boxes it is necessary to install an NLFC1S
350/NLFC3S350, depending on whether 1-phase or 3-phase power is used. In case of a strike the trip switch will trip and will not be able to be reset again before the blown fuse, indicated by a red LED light, is replaced with a (NLRF350ST/NLRFN350ST). This ensures that no strike will go unnoticed and that the equipment might be left unprotected for only a short period of time, until the fuse in question has been replaced.
In the server room cabinet, it is necessary to install either the Netshield NLMAINLITE-2U-E, NLPROCLITE-2U-E or NLEDU-PROCxx-1U depending on the need of the user:
Basic entry level Class I & II surge protection for cabinets:
NLEDU-PROC16-1U or NLEDU-PROC32-1U Basic Entry Level Cabinet Lightning and Surge Arrestors
- 16 Amp comes with 3-pin SA plug and 32 Amp comes with a hubble industrial plug
- 16 Amp has C19 connector to feed through to UPS and the 32 AMP has a direct feed to UPS
- Both not SNMP Manageable
- Cannot add sensors
- No V11/X21 Protection
- Monitored by LCD status display
High entry level Class I & II surge protection for cabinets:
NLMAINLITE-2U-E and NLPROCLITE-2U-E High Entry Level Cabinet Lightning and Surge Arrestors
- The NLMAINLITE-2U-E offers protection to X21/V11 Telkom lines. There are two more slots available to expand to X21/V11 (NLPROV11R2)
- The NLPROCLITE-2U-E does not have these additional features.
- Both have an internal SNMP device that enables the user to connect to monitoring software. (NLMSNMP)
- Both have a Power Distribution Unit (PDU) containing 8x kettle (IEC) Connectors. It gives out 16A max
- Both can connect RS485 sensors such as temperature and humidity
- Both have Class I & II Protection
- Both have Equipment stage surge protection with Electrical VAC power measurement
- Both are monitored by LCD status display
- Both have 16 Amp feeding power sockets
- Both have 4 x 1.8Meter C13 to C14 type power cord supplied with the unit.
