B1. Is the Power Company at Fault ??

Electrical power companies around the country strive hard to generate clean, steady, dependable electricity. By the time this new, shiny electricity gets delivered to electronic equipment across the land, this electrical power has become polluted with spikes and surges and all manner of interference.

Not Healthy.

How did this happen?

Thousands of external spike, surge and interference sources act upon AC Power before it reaches your delicate equipment. Industrial machinery, office equipment, traffic lights, household appliances, radio & TV stations and Mother Nature are only a few of many factors, which contribute to AC electric power corruption and pollution.

Heavy duty machinery or controlled devices may not be electrically isolated from controllers or computer.

Lightning and other natural events often induce severe spikes, surges and interference on power lines, phone lines, network and video cables.. Lightning, more common and severe in summer, is a major cause for concern year round.

Broadly speaking, lightning is an electrical arc discharge between a charged cloud and earth; or between two oppositely charged clouds. A visible arc or ‘‘bolt’’ is created by the discharge current path. Discharge current continues between these two oppositely charged points until sufficient voltage equilibrium is reached so current can no longer maintain the arc.

Engineering studies show that it requires several million volts to initiate the lightning ‘‘bolt’’ or arc.

Studies also show that ‘‘bolt’’ or arc current may reach several million amps.

As this massive ‘‘bolt’’ or arc current begins to flow, a gigantic magnetic field is created. This large magnetic field spreads out from the ‘‘bolt’’ and sweeps across the country side, cutting across everything in its path.

Commercial electricity is generated by passing a wire loop through a magnetic field in the power company generating station alternators. (Actually many loops, dynamo driven through a very strong magnetic field)

Similarly, electricity is generated in wires that are swept by this gigantic, lightning caused magnetic field.

Electrical power lines, telephone lines, coaxial network and video lines (even metal clothes line !) have large voltage spikes and surges (up to 6,000 volts!) and interference inductively coupled by this sweeping magnetic field. These spikes, surges and interference are applied to all line connected equipment.

After the ‘‘bolt’’ or arc is extinguished, the built up magnetic field collapses, inducing another series of spikes, surges and interference.

From the preceding discussion, it’s obvious power, phone, data, video or network lines need not suffer direct lightning hits to develop damaging high voltage spikes, surges and interference.

Other natural events, such as spherics from wind, dust or snow storms also induce severe interference, surges and transient spikes on lines and cables. Although results from spherics can damage equipment and disrupt operation, they are seldom as severe as lightning.

Man Made Problems - Industrial machinery, electric motors, air conditioners, relays, power company switch gear and other heavy duty power equipment create high voltage surges, spikes and interference year round.

Even a simple home vacuum cleaner or refrigerator may create these problems. Surges and spikes from these sources can reach 2,000 volts and often inflict serious damage to Industrial controllers, computers and measurement equipment.

Of course, connected phone, data or network lines are liable to pick up power line induced transients, surges and interference.

Bear in mind that not all AC Power, data, network, video or phone line spikes/surges are severe enough to cause immediate equipment damage. Delicate circuits can be over stressed. Each over voltage hit degrades circuits and components a bit more; becoming more prone to interference or damage. After a number of hits, failure finally results.

A couple of severe storms could degrade the equipment, with actual system breakdown occurring much later when a shop vacuum cleaner was switched on!

High performance protective systems, as discussed in the next sections, clamp power, phone, video and data line surges and spikes to safe limits, holding over-stress to a minimum level, prolonging equipment life. Filtering systems are presented that remove disruptive interference.

We've talked about the problems - But You want some answers - read on

C. What Can be Done ??

Unfortunately there is no quick fix to the combined dilemma posed by nature, man and machine.

In this Section, we are going to present an overview of factors that should enter into your system protection analysis.

Efforts to insulate/ isolate your system from the man-machine-nature menace must take into account all possible paths these damaging and disruptive spikes, surges and transient can enter your system.  The overview presented in this section will point out vulnerable elements of your system.  Problems can't be subdued until you know where they originate.

C1. It Can't be Lightning - our Building has Lightning Rods !!

Huh???

I've heard that lament 2 or 3 times a week for the last 25 years.  Lightning rods are good for protecting the structure, but sadly they don't do a thing to protect electronics.  It can be argued that they aggravate interference.

Since corona discharge (the beginning of a lightning bolt or natural spherics discharge) starts most easily at a point, lightning rods have a pointed element extending several feet above the "protected" structure. If lightning were going to hit the structure anyway, these extended rods will conduct most of the discharge current to earth - and damage or destruction would be avoided. Alleluia!

But lightning discharge elsewhere, such as to a tree on a hilltop or between clouds, often will initiate significant spherics discharge into those protruding, sharp pointed rods.

What happens when Lightning or spherics discharge current flows from lightning rod to ground?  A gigantic magnetic field is generated around the rod, extending outward for hundreds of feet in all directions. This is a vast, moving magnetic field which induces voltage in all metallic elements the magnetic field encompasses. A single bolt may generate up to 10 ebbing and flowing magnet fields, spawning many spikes, surges and transients for miles around.

Lightning strikes between overhead clouds or between cloud and some nearby object will similarly induce gigantic magnetic fields, inducing disruptive and damaging voltages.

You could probably even measure some transient voltage induced in a paper clip lying on your desk if you were quick with the meter or scope !

Needless to say, your AC power lines, modem-fax-phone lines, network and video cables are awash in this stuff.

Needless to say, your AC power lines, modem-fax-phone lines, network and video cables should be protected.

C2. Priorities

AC Power Lines and Phone Lines, being the longest lines entering your premises, are most likely to be subjected to  lightning or man-made spikes, surges, transients and interference somewhere along their length.  And that damaging, disrupting pollution walks right down the lines into your equipment.

Efforts to combat the spike and interference threat should address AC power, modem-fax-phone lines, data lines, control lines as well as network, video and monitor cables.

Most damage is suffered on power line connected equipment.  Since almost all equipment connects to AC power somewhere, it is wise to install a high performance transient-spike-surge suppressor and quality interference filter at the point equipment connects to the AC line. Improved performance, reduced down time, lowered repair costs and extended equipment life will more than pay for the slight added cost of high performance, quality protection.

Modem and Fax equipment is predominantly phone line connected.  Phone lines spikes, transients and surges rank slightly behind AC power lines for number of hits suffered.  Since modems, phones and Fax machines are relatively low  cost, monetary damages are generally lower.  If down time, lost productivity and repair costs are factored in, a damaged modem may take on considerable value. Again, relatively small additional cost for high quality modem/fax/phone protectors will purchase longer equipment life, reduced down time and improved performance.

C3. A Very Important Point

Reduced down time and longer equipment life have been mentioned several times as reasons to consider high quality protection equipment.  

Why?

Spikes, surges and transients show up on power, phone, video, data and control lines all the time. 

Luckily, immediate catastrophic damage seldom occurs.

Unluckily, equipment components are overstressed by each high voltage spike or surge.  Each overstress incident can cause minute component deterioration, ultimately resulting in failure.  Here, again, high performance suppressors (on power, phone/modem line, data, video, etc) will reduce or eliminate the damaging impact of overstress.

In summary, we have shown you over the past tutorial segments numerous factors that contribute to creating an unfriendly operating environment in which your equipment is expected to function.

D. Finally - Some Solutions ! !

Efforts to combat damaging, disruptive spike, surge and interference threat should address data lines, network cables, phone- modem lines and AC power lines individually. We'll address AC Power in this segment.

D1. AC Power considerations

Wire in Filter Suppressors

In many cases, high performance wire in AC power Line Filter/Suppressor can be installed in the electronic equipment junction box or mounted directly within sensitive equipment. A typical wire in unit is shown in Figure 1. Generally wire in units are available with ratings up to 30 Amp load capacity. Models designed for 125/250 Volts, 250 Volts and 3 Phase Voltage ratings  are manufactured. The power line  filter attenuates electrical, RFI and noise interference, while the integral suppressor absorbs high voltage spikes, transients and surges. Models are available with wire leads, push on tabs, screw or solder terminals.

Several companies offer distinct filter grades to combat various interference conditions & problems. Electronic Specialists offer Commercial, Industrial and Laboratory grades suitable for most industrial situations likely to be encountered.

Effective interference filtering requires presence of both differential mode and common mode filters. Spike-surge suppressors should also provide differential and common mode suppression. In addition, quality suppressors should provide high current, high energy suppression, with a very fast response time.

Filter/Suppressors similar to that shown in Figure 1 can also be installed at machines which are known to cause interference or spikes. Be certain  to specify correct operating voltage & current, as well as temperature and mounting criteria.

Line Cord filter suppressors

Stand alone controllers, computers or other apparatus can readily be protected by line cord type protective systems. Figure 2 shows an Industrial grade line cord unit. This model is typical of the over 50 line cord models which are manufactured by Electronic Specialists. Additional models are available for Direct Plug wall socket connection, 250 Volt operation and 3 Phase electrical systems.

Again, quality manufacturers offer choices of several grades and models to permit adapting to industrial situations as encountered. Twist type industrial electrical connector systems can be protected with Twist Protect models similar to the unit illustrated in Figure 3. Standard NEMA Twist Type socket designations for voltage, phase and current can be accommodated.

High performance protection designs have contributed to longer equipment life and improved system performance for thousands of computer, audio, industrial and scientific installations throughout the world

Note that some manufacturers offer direct plug suppressors with   specifications identical to line cord models.  Eliminating the line cord, direct plug units offer a  more compact system installation.

Computer stores, office supply outlets, computer supply catalogs and local hardware stores sell spike-surge suppressors. Some suppressors are quite good, some not so good, and some are little more than (poor quality) extension cords. Unfortunately, it is a bit difficult to determine quality.  Price alone is not always a good indicator - some units with very low suppression capabilities and no interference filtering sometimes sell for about the same price as good units.

Later in this tutorial segment I'll give you some evaluation criteria to aid your purchase decisions.

D2. Isolators and Power Line Interaction

I Know This is Hard to believe - But

Some systems suffer from AC Power Line interaction. This is particularly true for systems employing sensitive test and measuring equipment together with high power controllers or heavy duty units under test. A typical line cord model Isolator is shown in Figure 4.  Reports have indicated a remarkable "settling down" of here-to-fore erratic test set-ups.

High performance audio or home theatre systems have also shown considerable power line interaction vulnerability.  Power amplifier demands subtly affect power entering the low level pre-amp and balancing stages, casting  a discernable distortion into the reproduced sound (and sometimes affecting video). Audio and video enthusiasts (a discriminating group) describe the effect of filter-Isolator installation as "lifting a veil that enshrouds the performance".

Significant performance improvement, in those systems suffering from equipment interaction, can be achieved using line cord or wire in filter Isolators. Isolators incorporate filter isolated channels coupled with high performance suppression; a particularly effective combination which isolates protected equipment from power line pollution in addition to providing isolation between  interacting components.   Not needed for every installation, these AC Power Line filter Isolators have rendered many erratic systems blissfully stable.

Offered by several manufacturers, Isolators are available with various grades of performance.

We'll present a segment later, with much more on AC Power Line Equipment Interaction

D3. Other AC Power Devices

This tutorial segment has introduced several devices widely used to convert unfriendly industrial or commercial electronic systems into the very model of docility.

A later segment will discuss voltage regulators, isolation transformers, power interrupters and filter-isolators.

E. AC Power Specifications to consider

E1. First - Suppressors

Most folks refer to any AC Power protector as a "suppressor".   That's the reason many people question why they should pay $25, or $50  or even $100 for a real suppressor since their dealer "threw in" a perfectly good $7.50 suppressor when they purchased their equipment.

Allow me to explain - -

A great majority of suppressors on the market today employ MOV technology - some in a hybrid version with other type suppression devices.  Some units use only one MOV; Others use an array of 10 (or more) suppressing devices.

At the very low end, units are sold with a single 6,500 (or 4,500 !) ( or worse - 2,500 !!) Surge Amp MOV suppressor positioned between the power line "hot" and "neutral" bus.  I've seen many of these where the MOV got hit hard and literally vaporized. All that remained were 2 wire stubs where the MOV used to be - the suppressor case inside was coated with fine dust!

Between the time the MOV vaporized and the time I inspected the device, these owners thought they were protected!

Their equipment was continuously being stressed by lower level spikes and surges which exist on power lines almost daily. Luckily, a major surge hadn't wiped them out.

A slight improvement, but...

Once you get past the bottom-feeding single MOV suppressors, you encounter 3 MOV devices.  These are usually 6,500 surge amp MOVs, but I've seen 4,500 surge amp units used.  These suppressors may give up to 3X more protection than a single MOV device, but that's still a very slim safety reed to lean on. I've seen vaporized MOV's   in these, with power still being delivered to the sockets.  Connected equipment was still unprotected!

Three MOV units might advertise as 18,500 Surge Amp, or 5,000,000 Surge Watts, or .... some of their specifications may get a little rubbery! They might talk about common and differential mode protectors (which they are) without any protection level indication.  Sometimes there is no protection information - relying on a snappy package and glib salesman to move product.

And the good stuff ....

Quality suppressors generally provide a minimum 39,000 Surge Amp capability, ranging upwards to 60,000 Surge Amps.

Note that spike-surge feed through voltage decreases as a unit's Surge Amp capability increases.  Feed through spike / surge voltage for large energy hits may cause equipment stress.  Higher Surge Amp units provide more protection

Many will give a "Surge Watt" and "joule" rating.   Surge Watts sound quite impressive - from 10 to 50 million Surge Watts !! for a 2 micro-second surge pulse, while energy dissipation ranges between 400 and 2,500 joules.   These numbers can be calculated making various assumptions (all more or less valid), while Surge amps is more often based upon device manufacturers ratings.

Some models incorporate thermal shutdown or surge fuses to disconnect equipment in the event of a catastrophic surge.  Surge fusing operates independently of other fuse or circuit breaker protection and is not intended as a primary fuse.

What about hybrid configurations?

Hybrid suppressor technology refers to the practice of employing 2 or more device types in an arrangement designed to augment equipment protection.

High Speed suppressor diodes and gas tube suppressors are devices most often used with MOVs for hybrid designs.

Gas tubes..

Gas tubes respond to surges and spikes in 1 or 2 microseconds, slightly slower than MOV devices. Additionally they will pass more surge current than MOVs, leading to impressive (but suspect) Surge Current and Surge Watt numbers.

On the negative side, they are less reliable than MOVs. Further, once a surge or spike activates the gas tube, it will continue to pass large current until the AC cycle reverses.  If a spike occurs early in the AC cycle, massive power line current could be drawn throughout half the AC cycle.

Suppressor diodes ..

Suppressor diodes respond to surges and spikes within 1 - 10 pico-seconds; over 1,000 x faster than either gas tubes or MOVs. They are ideal for suppressing sub-nanosecond spikes generated by thyrister controlled devices which now exist in every facet of our life. Sub-nanosecond spikes show up, do their damage, and are gone before the MOV even begins suppressing activity.  Very high short term current and extremely fast response make suppressor diodes a natural for  eliminating damage and disruptive threats from sub-nanosecond spikes

On the negative side - suppressor diodes do their work so fast they add virtually nothing to Surge Amps, Surge Watts or joule specification numbers.

To Sum up Suppressor specifications ...

Surge Amp ratings are the critical rating to check. Look for a minimum 39,000 Surge Amp rating.  Units with less capability generally provide no surge amp information.

Remembering that Surge Watt and joule rating values are calculated, varying widely and are not always provided, units claiming 10 million surge watts and / or 400 joules will provide adequate protection. 

Note that Electronic Specialists line cord and direct plug units provide a minimum 58,500 Surge Amp suppression.  Surge Watts conservatively specified at 30 million watts, while an alternative calculation yields 60 million. Energy dissipation is specified at 620 joules, with an alternative computation yielding 2,500 joules.

Electronic Specialists wire-in filter-suppressors are available with ratings from 39,000 Surge Amps to 200,000 Surge Amps. Wire-in filter-suppressors offer options of Commercial, Industrial or Laboratory Grade RFI and noise interference filters

And, of course, we are always available to design protection for your special applications.

E2. Filter Networks

Interference can get onto your power lines either via conduction or radiation. 

Power station generated noise interference, as interference caused by connected electrical equipment is carried to your system via conduction down the power lines. 

Interference generated by lightning or other spheric conditions, from various radio / TV stations, RFI from automobile ignition systems or noise from arcing motors gets onto power lines by radiation.  Once on the line, interference is conducted to your system. 

Needless to say, this interference can extend up to 200 MHz with wide amplitude variations.

Depending on interference amplitude and frequency, your equipment may suffer very little, some or extreme reaction.  In extreme cases programs behave erratically, sometimes even causing system crashes.

What to look for

Some low cost, single MOV suppressors claim to have "filtering".   Usually this is a cheap capacitor. A few low end units claim the inherent MOV capacity provides filtering!

Better units offer various filter grades - - the most common filtering specifications are about 45 db attenuation over a range of 100 KHz to about 10 MHz.   This performance level is usually sufficient to clear up average interference problems. 

Since interference is occasionally present on all power lines, many manufacturers design some filtering into all but their lowest cost units.  These are routinely  installed as a low cost insurance policy by many system owners.

A few companies offer filter-suppressor filtering choices, permitting system operators to purchase capability consistent with their environment requirements.

Filtering ranges extend to about 65 db attenuation between interference frequencies of 10 KHz to 250 MHz.

When coupled with high performance suppressors a wide band, high attenuation filter can tame the wildest system.

F. Costs

Avoid "cheapies" like the plague! Mostly, these offer a false sense of security. If the sales person offers you one "free" when buying a new system - ask for the money.

To get an idea of prevailing costs, browse computer stores, catalogs and computer magazines.  You'll see lots of low end units, a fair number of passable units and maybe a few high performance units. This will give you a price - performance claim range.  There most likely will not be advertisements for very high performance protection.

Why the predominance of "cheapies"? Almost no one understands the interference and spike-surge threat presented to systems, therefore they feel they get adequate protection - maybe a "Suppressor" label will protect them!

High performance units usually cost little more than medium priced filter-suppressors. When weighed against the down time and equipment replacement cost, shortened system life due to undetected spike-surge over voltage stress and general aggravation, the added security and peace of mind is well worth the added cost.