Shockingly Insightful
The infamous “voltage spike” lasts for microseconds, yet its damage is often permanent – and most of
the time is catastrophic. Most often, the questions relating to these spikes (transient surges in voltage
or current) asked are where do they come from? And what should one do about them?
Transients are usually presented through lightning bolts due to the fact that they make for dramatic
images, but they are not the only source of such events. Transients also occur within the utility grid for
various
reasons but most of the time, transients originate from inside a certain given facility. A
well-known and common source is that of switching loads on or off.
Transient surge protection can come in several forms. For example, one can prevent the surge at its
origin by using a soft-start motor. However with sources like lightening, prevention is impossible. In
such cases, one should cope with the surge rather than try to prevent it from happening. For those
surges that take place within the surroundings of the facility, one can divert the surge to the
grounding of the service entrance by making use of the surge protective device (SPD). For those that
tend to originate inside the grounds of your facility, one should make use of SPD’s in order to reduce
the surge level at the inside distribution panels as well as at key points of use. By protecting the
distribution SPD’s from outside surges, one can make use of smaller SPD’s which will ultimately save
you money when the number of distribution panels is high.
SPD’s operate in one of two modes:
• Surge arresting: this limits surge voltages on the primary side of the meter by discharging or
bypassing surge current
• Transient voltage surge suppression (TVSS): Limits transient voltages on the secondary side of the
meter by diverting or limiting surge current
In either case, the device prevents continued flow of follow current whilst remaining capable of
repeating these functions. How long it remains capable depends on the number of times it carries out
these functions as well as the severity of the transients.
SPDs cannot reduce swell in power nor can they reduce harmonic conditions and SPD’s alone
cannot provide energy savings or reduce one’s utility bill. But, SPD’s can absorb or divert surge
energy, most use the diversion method and provide a shunt path for transients before they can enter
the equipment. Consider the following analogy: the pressure relief valve that protects a water
mill
does nothing until a surge occurs within the water supply. When this happens, the valve opens thus
allowing for the extra pressure to be pushed out, therefore it will not reach the water wheel. Even if
the relief valve is in the correct place and is working properly, a remnant of the surge will still reach
the wheel but it will have been reduced enough to prevent damage.
An SPD will not function properly unless the system is grounded according to legislation. Many often
forget to reduce the difference in ground reference between port connections for multi-port
appliances. One must ground all communication systems to the same grounding electrode system as
the power. Providing separate grounds for the power system and communication systems is a
violation as you are inviting a flashover from one system to the other.
AC/DC Dynamics offers our customers a full range on Lightning and Surge protection devices,
for more information on these devices please call 010 202 3400 or Visit our website on
www.acdc.co.za