Communications Problems - Can TVSS Provide The Answer?

Mick Burgoyne, Chief Engineer at Power Solutions specialist Advance Galatrek
looks at how telecoms and data installations can benefit from the installation of the latest voltage surge suppression technology.

It's an all too familiar scenario. You're on the phone to an important customer, and - far from being able to hear whether he's about to place the
biggest order of the year - all you hear is an irritating crackling on the
line. Worse still, your plea to repeat the last sentence for the third time
just doesn't seem to be getting through.

Well, if it's any comfort at all, you are not alone. Every year, thousands of users report that their critical business calls have suffered, for some inexplicable reason, from intermittent hissing, buzzing, crackling and
general interference. And, when the phone companies investigate the phenomenon, they find nothing untoward. It's a phenomenon that frustrates IT departments, telecoms engineers, sales managers, directors - in fact anyone that has to use the phone on a regular basis for business.

But, this understandable annoyance that many of our industries suffer as a
result of poor quality voice communications is nothing compared to the
potential loss of revenue that can arise if their data systems suffer the
same fate. And yes, you'd better believe that this is exactly what all too
many businesses are experiencing at this very moment. But the worse thing,
however, is most organisations are unable to attribute their voice and data
processing errors to anything other than the occasional glitch.

Make no mistake, every click and crackle on the phone, as well as every PC
crash or data error has a cause somewhere. And, although I'm not suggesting
that spikes and surges in the power supply are at the root of each and every
problem, there is little doubt that they contribute to a significant number
of these anomalies and aberrations. In fact, no lesser source than IBM's
Systems Development Division comments that 'More than 80% of mains power
problems are transient and noise related.'

On top of the annoyance caused by crackling and other interference on voice
calls, many organisations suffer from more sinister problems and damage.
Many of us have used modems that, inexplicably, have refused to work one
morning; usually we just shrug our shoulders, and attribute their failure to
wear & tear. Equally, some of us will have heard of phone systems that
simply refuse to operate, even though they might have just been serviced.
Then again, there are countless stories of computer power supplies failing
prematurely, network cards breaking down before their time and hard drives
ceasing working, with the loss of vital data.

All these incidents have a cost implication, of course. In the first
instance, there is the obvious bottom line financial penalty associated with
repairing, or more likely replacing, damaged equipment. After all, many of
these highly sensitive electrical components are performing essential tasks
that cannot easily be switched to other equipment. As such, business
continuity will be severely compromised if the damaged equipment remains
inoperable, even for a short duration.

As well as the physical cost of replacing damaged and broken components and
equipment, there are the wider costs associated with critical system
downtime. For example, if an organisation's phone system is out of
commission for even just a few minutes, who is to say which vitally
important calls might have been missed during that time? Moreover, If data
belonging to the company is damaged, erased or corrupted as a result of some
power problem, there is the incalculable cost of trying to piece together
what has been lost. Given that many organisations do not possess back ups of
their data, it is hardly surprising to hear that some companies never
recover from such a disaster.

So, what's the real cause of these potentially business threatening problems
and, equally, what remedies can we propose? Well, the first thing to
remember is that there are many sources of electricity all around us. Mains
power, generated in the usual way and distributed to us via the national
grid, is only one of the many ways in which electricity enters our daily
lives. Static electricity, generated by clothing for example, can wreak
havoc with sensitive microchips and processors.

Even more destructive is the awesome power contained in a lightning strike.
As an example, a typical strike can lead to a voltage surge of well over
20,000 Volts being transmitted through the mains supply. Not surprisingly,
this can cause instantaneous and catastrophic equipment failure, resulting
in immediate operational shut down and long term disruption of business.

Remember however that research indicates that up to 80% of voltage surges
come from internal sources such as motors, fluorescent lights, photocopiers
and other switching devices. This leaves the remaining 20% of transients
arising from external phenomena such as lightning. Of course, this doesn't
mean that either is more deleterious than the other. In fact, even though
internally generated transients will normally be of a lower peak voltage,
they will often cause cumulative damage, leading to premature failure over a
period of time. It's just that external transients receive more publicity
and interest, largely because they are more spectacular and, more often than
not, the cause of immediate equipment failure.

So, the answer is some sort of component that can be placed before the
critical component - be it comms or data hardware - that will successfully
absorb and dissipate the transient energy from both internal and external
sources. But don't think that this is a problem that only affects the mains
input. There are plenty of documented instances of phones, modems, faxes and
data servers being damaged by transient energy transmitted down the
telephone line or communications cabling.

This is where the transient voltage surge suppressor - or TVSS - comes into
play. Briefly, a TVSS is a passive device that limits the amount of energy
arising from a transient surge and, as a result, protects electrical
equipment from damage. Equally, however, a TVSS can also be used in
circumstances where certain equipment known to produce transients - such as
photocopiers - needs to be isolated from more sensitive hardware.

One of the most damaging events for the highly sensitive modern
communications equipment that we all have in our offices and factories is a
lightning strike actually hitting a telephone line. Just as when lightning
surges through a mains supply, the peak voltage produced can be in excess of
20,000 Volts. Not surprisingly, the electronics contained in our telephones,
faxes and modems cannot withstand this level of voltage spike, even for a
few milliseconds. What we need, therefore, is to install a transient voltage
surge suppression module upstream of the comms hardware, in exactly the same
manner as we would with a mains TVSS unit.

The same principle applies equally to data comms and cabling installations.
Imagine for a moment the likely consequences of several thousand volts
coursing unchecked through the back of your PC, via your network connection,
serial port or USB. Even those of us with a less than vivid imagination will
be able to foresee the makings of an IT disaster. Fried motherboards,
inaccessible hard drives and unusable memory would all be on the menu. And,
as I mentioned before, even though the actual replacement costs might just
be containable, the longer-term consequences might not be surmountable.

Even if we disregard the effects of an average strength lightning strike on
our data and comms hardware, there is still the more insidious effect of
lower energy surges and spikes to consider. Because transient energy has
many sources, highly susceptible data and voice communications cabling can
be subject to wide ranging variations in voltage. In practice, this means
that components that were designed to accept just a few millivolts can see
many times their rated voltage, time and time again.

Over a period of time, this exposure to unwanted transients can lead to
dramatically accelerated wear and tear, with the result that the design life
of each critical component is significantly reduced. And what's the
consequence of this effect? Well, rather like the metal fatigue that sets in
when a component is stressed beyond its design parameters, the electronics
will inevitably suffer failure when you least expect it. And the likely cost
of such a failure? Again, if you value the data on your system, and have
some inkling of what a full IT infrastructure crash could do to your
organisation, you'll be able to answer that one yourself.

It's worth touching briefly on the types of TVSS that are commercially
available. There are three basic types of surge suppressor on the market -
the gas discharge tube (GDT), the metal oxide varistor (MOV) and the silicon
avalanche diode (SAD). Each unit has its own characteristics, although the
manner in which the individual components are assembled also affects the
efficiency of the device. Tests have indicated that a combination of SADs
and MOVs provides the best overall solution. Because the SADs react very
quickly, they prevent the clamping voltage of the device rising as more
current is dissipated by the MOVs.

The ideal component structure for a TVSS device is the matrix configuration.
This is an entirely passive solution, where the individual SADs and MOVs are
arranged in separate assemblies, allowing individual components to
self-sacrifice without compromising the performance of the TVSS as a whole.
Because of this, the matrix solution offers all the advantages of SADs and
MOVs as individual components, but provides additional reliability and
crucial performance where they are most needed.

Even if one of the SADs or MOVs should fail, the remaining components will
continue to protect sensitive equipment from possible damage. In fact, TVSS
devices using matrix technology have an anticipated survival time of 100,000
lightning strikes, even allowing for individual component self-sacrifice.
And after all, there can be little doubt that the occasional replacement of
a passive component such as a voltage surge suppressor is a far better
option than risking your organisation's entire business in the event of
critical component failure.

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