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In order to provide uninterrupted power to the service sectors as well as others for economic growth and prevent equipment damage with varying voltage level and frequency, undoubtedly power quality improvement is utmost important.


For that, different CUSTOMERS have relied on experts, like us, able to provide a complete Power Quality and AC Energy Backup solutions with the proper equipment and consultancy. But, why customers have developed this trust on us? As you could see from Our Value Offer video here you will find some of the reasons:

Factories Integration experience
  • We have made deep contacts with more than two hundred factories internationally, in products related to our area of work, developing strict OEM and ODM agreements with many of them.

  • These contacts have led to continuous adaptation processes and improvements of products and solutions, according to various markets and specific customer needs.

  • As a result, we are able to lead projects together with the factories, which are all ears to our requirements with extreme confidence. We have achieved that special "passport" that allows us to break the ice and the differences, both corporate and cultural, that many others have tried to overcome without any success.

  • This has allowed us to group or integrate different factories, when a customer or a market needs solutions that involve the combination and interconnection of state-of-the-art technologies from different companies, making them work together and in unison, offering the end customer, as you will see in detail later; a complete solution, with a unified guarantee and under our total guidance and leadership.

Then, using the power of our Integration Coefficient IC Marketing and Manufacturing model, we are able to provide state of the art Power Quality with Energy Backup Solutions, for example, like this:

Power Quality best solutions

Where for any site we can arrange the provision of all elements needed to make your installation free of the problems caused for inconsistent power as limited run-time, physical plant issues and high maintenance costs. And all of this just integrating for you, from the best suppliers in every kind of technology needed, equipment to solve the Power Quality Disturbances types described below and that are detailly explained in the following links:


Power Quality concepts

Power Quality Disturbances types

Power Quality Equipment Solutions

       SCR Based

       Servo-Motor Based

       Standard Isolation with high CMRR

       K-Factor Rating

       U.S Standards

       Eurasia Standards

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Power Quality concepts


Power distribution systems, ideally, should provide their customers with an uninterrupted flow of energy at smooth sinusoidal voltage at the contracted magnitude level and frequency. However, in practice, power systems, especially the distribution systems, have numerous nonlinear loads, which significantly affect the quality of power supplies an the purity of the waveform of supplies is lost. During this explanation we are showing different "critical loads environments" that are commonly affected for these disturbances.

Critical Computer Data Centers
Critical Robotic cars assembly
Critical load dispatch centers

Institute of Electrical and Electronic Engineers (IEEE) Standard IEEE1100 defines power quality as “the concept of powering and grounding sensitive electronic equipment in a manner suitable for the equipment”. Power quality imposes pre-specified quality and reliability of supply. This pre-specified quality may contain a combination of specifications of the following: low phase unbalance, no power interruptions, low flicker at the load voltage, and low harmonic distortion in load voltage, magnitude and duration of over voltages and under voltages within specified limits, acceptance of fluctuations, and power factor of loads without significant effect on the terminal voltage.

Critical Surgery Room
Critical Chemical process

Apart from nonlinear loads, some system events, both usual (e.g. capacitor switching, motor starting) and unusual (e.g. faults) could also inflict power quality problems. In critical backup energy and power quality applications even brief power outages can be extremely costly.

Critical stock exchange centers
Critical betting centers

Also, under heavy load conditions, a significant voltage drop may occur in the system. Voltage sag and swell can cause sensitive equipment to fail, shutdown and create a large current unbalance. These effects can incur a lot of expensive from the customer and cause equipment damage.

TV control centers
Critical radio stations

The performance of electronic devices is directly linked to the power quality level. Quality phenomenon or power quality disturbance can be defined as the deviation of the voltage and the current from its ideal waveform.. Faults at either the transmission or distribution level may cause voltage sag or swell in the entire system or a large part of it.

Critical cashier and ATM machines
Critical casino machines

Along with technology advance, the organization of the worldwide economy has evolved towards globalization and the profit margins of many activities tend to decrease. The increased sensitivity of the vast majority of processes (industrial, services and even residential) to Power Quality problems turns the availability of electric power with quality a crucial factor for competitiveness in every activity sector. The most critical areas are the continuous process industry and the information technology services.

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Power Quality Disturbances Types

and Potential Solutions 

We are increasingly reliant upon sensitive electronics to perform critical functions for manufacturing processes, communications, commerce and government, which are inherently susceptible to power quality problems. Facilities utilizing sensitive electronics for data processing and automated process control can improve operating efficiencies by the implementation of a Power Quality Audit that can be achieved for our Group as Power Quality Specialists to determine actions and the equipment needed to minimize to the lowest level any operation disruption or load failure.


Some of these power disturbances are obvious, while many are almost unnoticeable; but they all cause problems that can seriously disrupt your productivity, from lost data and system lock-ups to communications errors and hardware failures.


Power disturbances can have their source in either the utility or customer wiring system and/or equipment. These disturbances can be classified into categories that can vary in effect, duration and intensity. The chart below lists the most common categories of disturbances, their causes and some potential solutions.

Power Quality disturbances types
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Power Quality Equipment Solutions

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True On Line UPS's

Typical Modular on line UPS models

Data & IT:

In an increasingly connected world, downtime in data processing of all kind and in IT operation is not an option. Any power failure can have a devastating impact on mission-critical computers, communications and data, resulting in costly downtime. For utility-scale data center, we have made strong partnerships with significants suppliers to provide tailored solutions to customers’ needs for protection against main failures and secure power to avoid any data loss and guarantee the continuity of operations.

General Industry:

In manufacturing, quality and availability of power are essential to maintaining uptime and meeting production schedules. An unplanned outage stops production, diverts labor and creates waste, particularly if you have to discard unfinished or damaged products as a result of the outage. Maintaining uptime is even more essential with so many manufacturing companies running production lines 24/7. UPS systems can reduce downtime (and its cost) in manufacturing by providing reliable backup power in an emergency and can also support your daily operations with power conditioning that keeps your equipment safe and functioning at peak efficiency.

Oil & Gas:

Mission-critical applications in the up, mid and downstream segments of the Oil & Gas and Petrochemical industry need 100 % available highly reliable electrical power to protect the people, the assets involved in the processes, the environment and guarantee the continuity of sensitive operations. We strive to be innovative by offering state-of-the-art customized solutions, combined with a package of full project life cycle services to ensure exceptional reliability, even in extremely harsh environments..


Medical and healthcare services now generally rely on micro-processor based technologies. In addition to diagnostic equipment, UPS systems provide battery backup for life-sustaining medical equipment in the event of an emergency. Patients relying on ventilators, dialysis, respirators, anesthesia machines and more need a continuous power supply to provide care and support as they recover. 

In a medical environment, reliable power distribution is critical. UPS offers systems that enables the load to maintain operation seamlessly during this transfer, sure uninterrupted power during operation. In the event of a black- or brownout, UPS can provide backup power to life-support equipment until generators or solar-wind energy backup are available.


When communication is mentioned as a mission critical application, satellite systems and tall microwave towers come to mind. But in today's marketplace, communications encompass far more, such as video conferencing, VoIP networks, 5G, and IoT. With UPS systems to support your communications network, you can maintain critical access for your customers. Whether supporting a hyperscale or edge data center, your telecom backup power needs to be reliable and that’s just what you get with UPS power.

Government, Education, Broadcasting Radio & TV Stations:

Power is one of the most critical factors in running your business – even the telephone now requires a plug socket! It is no mean feat designing and implementing a power protection program. It only takes one slip up to bring a corporation to its knees. All public and private services are subjected to fail for unproper or lack of Power Quality program. We can help you with a quality service solution regardless of your businesses technological requirement. Our UPS power providers selection can ensure a full life cycle protection program from conception to decommissioning, giving end-to-end service and support for all your computing environments.

Voltage Stabilizers & Power Conditioners

Voltage sags and extended under or over voltages have large negative impact on industrial productivity, and could be one of the most important type of power quality variation for many industrial and commercial customers. Voltage sags may either decrease or increase in the magnitude of system voltage due to faults or change in loads. Momentary and/or sustained over voltage and under voltage may cause major problems including equipment failure, overheating and complete shutdown. In order to maintain the load voltage constant in case of any fluctuation of input voltage or variation of load some regulating device is necessary.


Voltage sags is mainly due to the fault occurring in the transmission and distribution system, loads like welding and operation of building construction equipment, switching of the loaded feeders or equipment. Both momentary and continuous voltage sags are undesirable in complex process controls and household appliances as they use precision electronic and computerized control.


Applications of Voltage Stabilizers have became a need. Different types of Voltage stabilizers are available now with different functionality and works. The latest advancements in technology like Microprocessor chips and Power Electronic Devices have changed the way we see a Voltage Stabilizer. They are now fully automatic, intelligent and packed with a lot of additional functions. They also have an ultra fast response to voltage fluctuations and allow their users to adjust the voltage requirements remotely including start/ stop function for the output.

When adding an Isolation Transformer (a shielded transformer is a two-winding transformer, usually delta–wye) connected to the Voltage Stabilizer, a Power Conditioner is created able to provide up to 85% solutions against power disturbances through the following functions:

  • Voltage transformation from the distribution voltage to the equipment’s utilization voltage.

  • Converting a 3-wire input power to a 4-wire output thereby deriving a separate stable neutral for the power supply wiring going to sensitive equipment.

  • Keeping third and its multiple harmonics away from sensitive equipment by allowing their free circulation in the input delta winding.

  • Softening of high-frequency noise from the input side by the natural inductance of the transformer, particularly true for higher frequency of noise for which the reactance becomes more as the frequency increases. 

  • Providing one or more electrostatic shield between the primary and the secondary windings will avoid transfer of other noise frequeenciies and some surge/impulse voltages passing through inter-winding capacitance.

SCR based AC Voltage Stabilizers & Power Conditioners

SCR AC power conditioner

Our AC Power Conditioners & Voltage Stabilizers based in Non contact Brush-less SCR tap changers ranged from 10kVA to 1000kVA (more power under special design), single and three phase, with excellent regulation tolerances, integrated shielded isolation transformer among other extraordinary features are compatible with almost all industrial and commercial equipment having strict regulation and power conditioning needs.

Basically the SCR Based AC stabilizers have been mainly designed to supply electronic loads, which need a constant power supply over time, so, they do not support any voltage fluctuation, unless it is inside the output window. The Stabilizers are fully static and with independent phase regulation for three phase equipment, the response time is very fast and with a very narrow output accuracy. 


There are many industrial processes where voltage stability is essential: from a wide range of applications where numerical control processors and robots are responsible for guaranteeing the final result with the highest precision, up to all types of computing centers, peripherals IT, transmission and communication equipment, laboratory equipment, etc.

Our models feature a small footprint, high efficiency design, LCD display monitoring, front, lateral and back access for easiest electronic maintenance, testing and wiring installation procedures and RS232-RSS485 communication interface options. They are featured with an electronic microprocessor controlled tap switching power conditioning voltage stabilizer which consist of an all cooper (or aluminum) single or multiple shielded isolation output transformer according to  customers selection. In conjunction with the electrostatic shield(s), the low output impedance of the transformer assures computer grade performance with excellent noise and transients attenuation.

For each of every tap per phase, independently controlled inverse parallel electronic switches (SCRs) provide a tight output voltage regulation meanwhile digital processing provides fast response for accurate regulation. Manual Maintenance By-Pass option is provided. Last but not least, size, weight, audible noise and operational efficiency are all optimized. Voltage and Frequency  worldwide configurations are fully available.

Servo-Motor based AC Voltage Stabilizers & Power Conditioners

Servo Motor AC Power Conditioner

Servo Motor AC Voltage stabilizers are based on the use of a continuously variable auto-transformer on which a brush driven by a servomotor is positioned. Our patented adjusting transformer’s transmission mechanism adopts the unique machine tool guide rail slider drive technology with the following advantages:

  • Very low transmission resistance, move smoothly, lowest audible noise.

  • Very high adjusting and positioning accuracy.

  • Beautiful and reasonable structure design output accuracy.


Its precision is much higher than that of an electronic SCR tap changer stabilizer, its typical value being less than 4% and normally 1% and from 10kVA to 1000kVA and even more according to special requirements. Its response speed is slower than SCR based units and depends on the speed of the servomotor, which will respond faster to small variations and slower to large variations in input voltage. Like electronic stabilizers, they filter out noise and some transient spikes.


Servo motor based voltage stabilizer consist of adjusting transformer and compensation transformer, with sensors and control system, managed by a state-of-art digital computer system. The computer system calculates the difference between output voltage and programmed value; identifies the solution; the electro-servo motor rises or lowers the actuator bar which changes the winding ratio to either increase or decrease the outgoing voltage.

Servo voltage stabilizer is best suited for large loads at the output. This is because servo voltage stabilizer has large power and current handling capacities as compared to other type of stabilizers. Our servo motor based stabilizer has been specially designed to work in unstable networks and safeguard critical loads, especially those of a complicated nature: large points of starting current, marked reactive character, great powers, etc. This is why it is widely used in virtually all forms of residential, commercial and industrial: telecom, factories, offices, petrol stations, department stores, residential apartment blocks, leisure-anywhere that needs to maintain constant output voltage, save power, costs & protect equipment from premature failure.

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Isolation Transformers: CMRR & K-Factor

High CMRR K-Factor rated isolation transformers

Standard Isolation with high CMRR


Isolation Transformers have primary and secondary winding that are physically separated from each other. It offers hundred percent isolation from the input AC line. It reduces the cumulative leakage current of the isolation and connected equipment. Secondary neutral to ground bonding virtually eliminates common mode noise, providing an isolated neutral-ground reference for sensitive equipment.


This is also known as 'insulated' because the winding are insulated from each other. Isolation transformers remove EMI/RFI noise, utility switching transients, and harmonics generated by other onsite loads (see K Factor Transformers) and utility or lightning related surge conditions. Our group offers units from 3kVA to 1000kVA, single or 3-phase. Due to the effective design, there are four main advantages that come with using an isolation transformer.



Perhaps the biggest advantage that isolation transformers offer is improved safety. This is particularly important in a setting such as a hospital or nursing home where expensive, life-supporting equipment has the potential for getting damaged. Using an isolation transformer also reduces the potential for doctors and patients to experience electrical shock as the result of defective equipment.


Reduces Surges:

Another advantage of isolation transformers is that they reduce power surges. Electrical equipment can run smoothly without the risk of power surges because the DC signals from a power source are isolated. This means that equipment can function at a high level even if there is a power malfunction.


Noise Reduction:

Another reason why isolation transformers are efficient is because of their noise reducing capabilities. The design of these devices naturally filters noise from power lines by using what are called separated Faraday or electrostatic shields. These shields help to block electric fields from interrupting the power flow. In turn, there is less electromagnetic noise involved with running electrical equipment. Shielded isolation transformers have all the feature of the standard isolation transformers plus it also incorporates a full metallic shield between the primary and secondary windings. 

These electrostatic shields or 'faraday shields' are connected to earth ground. It attenuates (filters) voltage transients (voltage spikes) and filters common mode noise. The shielded isolation transformer is preferred over a standard isolation transformer because it provides protection for sensitive and critical equipment and vastly improves power quality.

Isolation transformer electrical diagram

CMRR stands for Common Mode Rejection Ratio. It's a number that describes how well an Isolation Transformer will reject noise. It is relatively easy to calculate CMRR, it is a logarithmic scale and is expressed as so many dBs of level of attenuation of noise for the Isolation transforrmer with shields. Its calculation comes out as a negative number. If you can get a manufacturer to tell you the CMRR of a specific device, you can "understand" the numbers like this:


  • -40 dB CMRR: very poor noise rejection.

  • -50 dB CMRR: poor noise rejection.

  • -60 dB CMRR: average noise rejection.

  • -70 dB CMRR: good noise rejection.

  • -80 dB CMRR: very good noise rejection.

  • -90 dB CMRR: excellent noise rejection.

  • -100 dB and up CMRR: world class noise rejection.

Shielded Isolation Transformers with Single Electrostatic Shield: This is the simplest type of shielded transformer with one grounded shield extending from top to bottom between the primary and secondary windings. This will typically supply a CMRR of -60dB from 100Hz through 1MHz.


Shielded Isolation Transformer with Double Electrostatic Shields: This has two grounded shields extending top to bottom between the primary and secondary winding and between the secondary winding and the core. This will typically supply a -60 to -80dB CMRR from 100Hz through 1MHz.


Shielded Isolation Transformer with Triple Electrostatic Shields: This has three grounded shields extending top to bottom between the primary and secondary winding and between the secondary winding and core and covering the outer winding. Little benefit is gained by having the third shield. This will typically supply 65-85dB of CMRR from 100Hz through 1MHz.


Better Power Quality:

There is usually better overall power quality when users employ an isolation transformer. The Faraday shields also help with efficiency because they reduce the potential for current leakage. As a result, important electrical devices can function at an optimized level

K-FACTOR Rating Isolation Transformers

Typical K rated transformer sticker

Over the past several years there has been dramatic growth in the use of equipment incorporating switching type power supplies. Examples are personal computers, video display terminals, fax machines, copiers, electronic high efficiency ballasts, UPS systems, variable speed drives and various medical electronic monitors. The nature of all these loads is non-linear; they only demand current during part of the cycle and/or change their impedance during the voltage cycle. This type of load creates harmonic currents, which in turn generate heat in the distribution equipment, neutral conductors and distribution transformers.


A K-Factor rated transformer is one which is used to deal with harmonic generating loads. Harmonics generate additional heat in the transformer and cause non-K-rated transformers to overheat possibly causing a fire, also reducing the life of the transformer.


K-rated transformers are sized appropriately to handle this additional heat. Also, the K-factor number tells us how much a transformer must be derated to handle a definite non-linear load or, conversely, how much it must be oversized to handle the same load. K-rating is a heat survival rating, not a treatment of associated power quality issues like voltage distortion, and efficiency isn’t typically discussed. Surviving the extra heat means using more core and coil material, and sometimes use of different construction techniques. Depending on the manufacturer’s design, harmonic losses may be reduced to varying degrees.


Also when the isolation transformer is built Delta-Wye, these harmonics produced by non linear loads are trapped in the input Delta winding then avoiding their propagation and affectation to the rest of the loads that are sharing the same electrical circuitry.


A K-Factor rating is an index of the transformers ability to supply harmonic content in its load current while operating within it temperature limits. For Dry Type Transformers a K-Factor calculation is made to determine the amount of the harmonic content present in a power system. K-Rated transformers are sized to handle 100% of the fundamental 60 Hz load, plus the non-linear load specified. The neutral of the K-Rated transformer is sized at 300% of the current rating of the phase connections.

K factor rating table

K-factor values range from 1 to 50. K-factor of 1 is used for linear loads only, and a K-factor of 50 is used for the harshest harmonic environment possible. A K-factor of 13 is typical. When transformers use a K-factor value, they are said to be K-rated. Prime uses of K-rated transformers would be in factory automation, computer rooms, and office buildings because of the high harmonic content in these areas. Typically a K-13 rated transformer is sufficient for most applications. Loads approaching 100% non-linear or more than 75% THD should incorporate a K-20 rated transformer.


The following rules will generally result in an acceptable choice of K-factor value and usually it is a successful practice in sizing the transformers:

  • Where the harmonic current producing equipment is less than 15 percent, use a standard transformer K-1.

  • Where the electronic equipment represents up to 35 percent of the load, use a K-4 rated transformer.

  • Where the electronic equipment represents up to 75 percent of the load, use a K-13 rated transformer.

  • Where 100 percent of the load is electronic equipment, use a K-20 to K-40 rated transformer.


Higher K-factor ratings are generally reserved for specific pieces of equipment where the harmonic spectrum of the load is known.

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Transient Voltage Surge Suppressors  (TVSS)

Surge Protective Devices (SPD)

Multiple lightning picture

Until now we have been talking about power quality disturbances that cause mostly operation disruption and slow degradation to the loads, but now we need to show you the most dangerous kind of power disturbances that causes, mostly, complete destruction and faster degradation to the critical systems connected to the AC utility.

If high energy surges or transients in the electrical wiring of any system that can be produced by external lightning may cause the kind of disasters as showed bellow, can you figure out the severe damages that these disturbances would cause to sensitive and critical electronic power loads?

Disasters caused by lightning

Surge and Transient Voltage Surge are temporary rise in voltage and current on an electrical circuit. Their voltage ranges are greater than thousands of volts and current ranges are greater than hundreds amperes. Typical rise time is in the 1 to 10 microsecond range. Transients or surges are the most common power quality problems and cause significant damages such as electrical or electronic equipment failure, frequent downtime, lost data, lost time and business downtime, etc.

Transient effects vs voltage magnitude table
transients effects on electronic loads table

Being more specific, the three most prevalent types of system failure are: Catastrophic Failure, usually caused by arcing components or destroyed printed circuit traces; System Degradation of the sensitive electronic components and chip sets, continuously weakening until the component fails (normally this damage is not visible); and System Disruption, caused by power quality disturbances which are responsible for most of the unexplained and more elusive system lock-ups, data errors, communication errors and slow system operation faults.


These transients occur whenever there are sudden changes in a power distribution system, whether resulting from lightning or utility-switching disturbances on incoming power lines: the major of electronics damage from surge is lightning strikes.


The most damages is not caused by direct lightning strikes, but is the result of transient voltage and current surges induced on power, telecommu-nications or RF transmission lines by the strong electromagnetic fields created by during a lightning strike.

These can create transients so intense they literally destroy sensitive electronics. Energy changes within the system are responsible for more than 80% of surge suppression events. With such changes, voltage spikes are created by the energy stored in reactive components.


These voltage impulses can destroy semi-conductor devices, reduce the dielectric strength of insulation, damage electro-mechanical contacts and cause errors of logic circuitry by stray signals imposed on logic reference levels.

Electronic boards damages by transients

Transients may occur either in repeatable fashion or as random impulses. Repeatable transients, such as commutation voltage spikes, inductive load switching, etc., are more easily observed, defined and suppressed. Random transients are more elusive. They occur at unpredictable times, at remote locations and require installation of monitoring instruments to detect their occurrence.


Frequently, random transient problems arise from the power source feeding the circuit. These transients create the most concern because it is difficult to define their amplitude, duration and energy content. Random transients are generally caused by switching parallel loads on the distribution system, although they also can be caused by lightning. They are more common causes of power surge and examples are the operation of high-power electrical devices, such as elevators, air conditioners and refrigerators by switching on-off compressors and motor. Other sources of power surge include faulty wiring, utility power supply failure and electrical noise. So, you can find transients almost from everywhere, then it is imperative to be protected against them.

In the last years due to the increment of modern and high technology electronics loads, the losses due to transient voltages have been increasing dramatically as shown in the graphic bellow:

Direct strikes vs transients losses graphic

Surge Protector also known as Transient Voltage Surge Suppressors (TVSS), Surge Protection Devices (SPD) or Surge Suppression Equipment (SSE) are the solution designed to protect electrical and electronic critical loads from power surges and voltage spikes.

Surge suppressors pictures

How does Surge Protector work?

Surge protector diverts the excess voltage and current from transient or surge into grounding wire and prevents it from flowing through the electrical and electronic equipment while at the same time allowing the normal voltage to continue along its path. This excess energy can cause damages in electrical and electronic equipment, process control instrument-equipment. So, the two main functions of the surge protector are:


  • Provides low impedance path for conducting a lot of current to eliminate the extra voltage.

  • Absorbs and diverts the extra current to ground for protecting the effects of transient or surge.

A simple statement and it sounds great, but what does it really mean? How does a surge protector know how to do this? To understand that, we just need to simplify a little terminology. Understanding voltage and amperage can help you better grasp how surge protectors work:

How does surge suppressor work

Voltage: Using the analogy of water in a hose, voltage is the equivalent of electrical pressure.

Amperage: Using the same analogy, amperage is the flow rate, or amount of fluid running through the hose.

Using our trusty hose analogy, applying too much pressure in a hose can eventually cause it to burst. In the situation of electrical excesses, however, rather than bursting, electrical lines and loads may burn up, or at the very least wear down over time. By diverting excess pressure in the hose (your home’s wires) surge protectors safeguard wiring and loads together. To accomplish this, they need the help of special components. 

Managing the Pressure: How is all that pressure, or excess electrical energy, diverted? When voltage reaches a certain point, surge protectors simply re-route that extra energy with the help of what is essentially a pressure-sensitive valve. With the correct voltage, current flows through as normal, but with a spike or surge, the device kicks-in immediately and redirects the excess.


Commonly used devices for managing this pressure in Surge Protectors Devices include Metal Oxide Varistors (MOV), Zener Diodes (SAD) and Gas Discharge Tubes or arresters or a combination (hybrid) of two or three of them, which allow electrical devices to continue operation while diverting excess energy to grounding wires.

Typical Surge protector components pictures
Explanation table about different surge protector components


Surge Protectors will be only as good as your grounding conditions. Older sites with un-grounded outlets or, basically, facilities with improper wiring and grounding will not be helped by a Surge Protector Device without the necessary upgrades. Even the best Surge Protector Device will fail if there is no proper escape route via grounding for excess electricity to go. If your site has grounding issues, have them addressed quickly (we can help), as wiring repair or upgrade costs will pale in comparison to replacing "fried" equipment.

What U.S Standards are applicable to SPDs?

Typical UL listed surge protectors
cUL listed logo

Listing: In the U.S all AC power connected SPDs must be installed in accordance with NEC wiring rules. This requires that the product be listed for such a purpose. To be "listed", an SPD must be approved by a Nationally Accredited Testing Laboratory (NTL). One example of a NTL listing service is Underwriters Laboratories Inc. (UL).


UL1449 2nd and 4th Edition Listed: The primary concern of UL is safety. To this end they have developed a Standard “UL 1449 Edition 2 and 4 Standard for Safety, Transient Voltage Surge Suppressors” for the testing of TVSS/SPDs. Under Edition 2 and 4 of this Standard, an SPD is taken through an extensive test regimen to ensure that it will not pose a safety hazard under normal operations as well as under potential failure modes, such as abnormal utility supply events. However, UL 1449 is not considered a performance standard, but it does assign a Suppressed Voltage Rating to the SPD being tested. To some extent this allows the performance of two SPDs to be compared, however it is important to note that this test is conducted at a very low energy level to accommodate the smaller SPDs on the market. It does not adequately demonstrate performance for branch and service entrance products. A shortcoming of UL 1449 is that it only requires products to remain operational on voltages up to 110% of nominal. SPDs are allowed to (safely) permanently fail if voltage exceeds this. To limit the possibility of frequent SPD replacements due to Transient Over Voltages, it is recommended that customers additionally specify that the Maximum Continuous Operating Voltage be at least 125% of nominal. 


It is also important to note that UL 1449 does not test that an SPD meets the manufacturer’s claimed surge rating. While this may appear a severe oversight on the part of the Standard, it becomes more understandable when we consider that the primary concern of UL is safety and not performance.


ANSI/IEEE C62.41: In addition to considering the SVR figure provided for an SPD under UL 1449, customers should also request let-through voltages in accordance with ANSI/IEEE C62.41 Location categories A3 & B3 Ring waves and B3 & C3 Combination waves. This will test the SPD's clamping performance with currents up to 10kA 8/20µs.


ANSI/IEEE C62.45: Compliance with life cycle testing in accordance with ANSI/IEEE C62.45 should also be requested. This will ensure that products have been tested with at least 10-1000 sequential impulses.

Typical Surge Suppressor installation diagram

Proper Current Protection: To comply with standards and safety, the AC surge protectors must be protected against a possible end of life in short-circuit: the user must install on each SPD branch, a protection against short-circuit current (fuses or breaker). The rating of this fuses is given by the SPD manufacturer in the product data sheet or installation instructions. The choice of this rating depends of 2 criteria:

  • Withstand of the short-circuit current test in the UL1449 or IEC61643-11 standard: the fuse must cut safety the short-circuit current before a harsh destruction of the SPD.

  • Withstand of the discharge currents (Inominal or Iimpulse): the fuse must be able to conduct the discharge current of the SPD without blowing.

The fact that the responsibility to seek for the SPD manufacturer is left to the customers, evidence that they are supporting claimed surge ratings from manufacturers. Should be better that customers decisions about choosing any SPD may be provided in the form of in-house test results or preferably independent third party test certificates and/or supported by power quality audits done by experts.

So, how to connect and choose the right Surge Protection Devices in the U.S?

Typical Surge Suppressor installation site

In the U.S Surge Protectors are typically applied at several points throughout a facility. First, the unit needs to be listed by a safety standard like UL under UL1449 Edition 2 or 4 standards to comply with NEC. But complying with ANSI/IEEE C62.41-1991 and C62.45 standards that define three categories of AC surge level, based on strategic location within a facilities wiring network, where power problem may be encountered, is the right way to go. They classify the surge protector type, the potential impact of transient surge or spikes, and location as follows:

C62.41 standard for surge suppressor classes and locations
  • Category A: Defined as any outlets and long branch circuits extending more than 10 meters (30 ft.) from category B location or 20 meters (60 ft.) from category C. Surge protector for this location category is applied at the outlets or individual circuit level for individual protection of a specific piece of equipment such as computers, weighting bridges, measuring equipment, process control equipment and DC power supplies, etc.

  • Category B: Defined as all major sub-feeders, bus systems, and short branch circuits such as distribution panels, industrial bus-bars and feeder systems, heavy appliance circuits, lighting systems in large building. The protection at this location is very effective in suppressing the much more frequent internally generated transients, ever-changing transient conditions, especially, sensitive equipment and other equipment which are fed from the substations.

  • Category C: Defined as outside and main service entrance which includes main supply lines, transformer, service connections, and feeder line to main service entrance panels, any overhead or sub-feeders lines, underground lines to well pump. This surge protector type is applied to protect against externally caused power disruptions. This installation will help guard against lightning strike entering a facility via the power line.


Every transient or surge expected in every location is also defined by this standard as showed bellow:



B and C categories surge V-I wave types
A, B and C surge current and voltage categories table

These three categories A, B and C determine which surge protector or TVSS should be used at which location. But the most important thing is that a complete protection against surges will be achieved only by “combining” or “coordinating” the installation of a proper surge protection device for every part (category) of the building.

C and B Categories locations for surge suppressors

What International "EURASIA" Standards are applicable to SPDs?

In Europe and Asia or “Eurasia” a similar approach (as in the U.S) is taken into account for proper AC and even DC Surge Suppression and it is related with the standard IEC 62305-4, broadly used for most of the countries in that region. The similarity between both standards is based in the fact that the transient over-voltage protector’s ability to survive and achieve a suitable let-through voltage, clearly depends upon the size of the transient it will be subjected to. Then, this, in turn, depends upon the protector’s location. Additionally, to comply with a safety standard similar to UL 1449 the international standard IEC 61643-11 is also mandatory for those regions.

IEC 61643-11 standard logo
Typical DIN rail SPD devices

IEC 61643-11 International Standard. Surge Protective Devices meeting standards in Eurasia: Surge protective devices (SPDs) must provide defined protective functions and performance parameters in order to be suitable for use in corresponding protection concepts. As such, they are developed, tested, and classified according to their own international series of product standards. Surge protective devices connected to low-voltage power systems are subjected to the requirements and test methods specified by the latest IEC 61643-11 International Standard.

A true mark of quality is a product certification and approval from an independent testing institute. This confirms the fulfillment of the latest state-of-art product standard to ensure highest safety and integrity of the SPDs. The regulatory requirements placed on SPDs often require highly complex tests that only a few testing laboratories in the world are fully capable of carrying out.


How do you know? The quality and performance of surge protective devices are hard for a customer to assess. Correct functioning can only be tested in suitable laboratories. Besides the external appearance and hap-tics, only the technical data provided by the manufacturer can provide any guidance. Even more important is a reliable statement from the manufacturer and certification/approval regarding the performance of the SPD and the execution of the tests specified in the respective product standard from series IEC 61643-11.

IEC 62305-4 (part 4): While ANSI/IEEE standards C62.41 and C62.45 has classified the critical load location environment as Categories C, B and A, International (EURASIA) IEC 62305-4 is intending to describe or categorize the critical load locations as protection zone concepts named Lightning Protection Zones (LPZs). IEC 62305-4 provides information for the design, installation, maintenance and testing of a Lightning Electromagnetic Impulse (LEMP) protection system (now referred to as Surge Protection Measure (SPM) for electrical/electronic systems within a structure.

So, how to connect and how to choose Surge Protection Devices in EURASIA?

IEC 62305-4 standard for SPD

Lightning current or equi-potential bonding SPDs are used on overhead service lines feeding the structure that are at risk from a direct strike. However, the use of these SPDs alone “provides no effective protection against failure of sensitive electrical or electronic systems”, to quote IEC 62305-4, which is specifically dedicated to the protection of electrical and electronic systems within structures. Lightning current SPDs form one part of a coordinated set of SPDs that include over-voltage SPDs which are needed in total to effectively protect sensitive electrical and electronic systems from both lightning and switching transients.


Lightning Protection Zones (LPZs): IEC 62305-4 defines the concept of Lightning Protection Zones (LPZs) as illustrated in the following figure:

Lightning protection zones for SPD
Lightning protection zones description

The picture above looks very "modern" and "dynamic" and may create some confusion when trying to explain the way to install SPDs, but, fortunately, it can be drawn in another way to find how to categorize these zones set by IEC 62305-4 (EURASIA) with a similar approach as ANSI/IEEE C62.41 and C62.45 in the U.S.:

Comparing IEC 62305-4 with ANSI/IEEE C62.41 and 45

Within a structure a series of LPZs are created to have, or identified as already having, successively less exposure to the effect of lightning. Successive zones use a combination of bonding, shielding and coordinated SPDs to achieve a significant reduction in LEMP severity, from conducted surge currents and transient over-voltages, as well as radiated magnetic field effects. Designers coordinate these levels so that the more sensitive equipment is sited in the more protected zones.


The LPZs can be split into two categories: 2 external zones (LPZ 0A, LPZ 0B) and usually 2 internal zones (LPZ 1, LPZ 2) although additional zones can be introduced for a further reduction of the electromagnetic field and lightning current if or when required.

External Zones:

  • LPZ 0A: Is the area subject to direct lightning strokes and therefore may have to carry up to the full lightning current. This is typically the roof area of a structure. The full electromagnetic field occurs here.

  • LPZ 0B: Is the area not subject to direct lightning strikes and is typically the sidewalls of a structure. However the full electromagnetic field still occurs here and conducted partial lightning currents and switching surges can occur here.

Internal Zones:

  • LPZ 1: Is the internal area that is subject to partial lightning currents. The conducted lightning currents and/or switching surges are reduced compared with the external zones LPZ 0A and LPZ 0B. This is typically the area where services enter the structure or where the main switchboard is located.

  • LPZ 2: Is an internal area that is further located inside the structure where the remnants of lightning impulse currents and/or switching surges are reduced compared with LPZ 1. This is typically a screened room or, for mains power, at the sub-distribution board area.


Protection levels within a zone must be coordinated with the immunity characteristics of the equipment to be protected, meaning that the more sensitive the equipment is, the more protection for the zone is required. The existing fabric and layout of a building may make readily apparent zones, or LPZ techniques may have to be applied to create the required zones.

Coordinated SPDs: Same as U.S. standards, the complete protection is possible when Surge Protection Devices (SPD’s) are installed in a coordinated way. Coordinated SPD’s simple means that a series of SPD’s installed in a structure (from the heavy duty SPD at the service entrance through to the over-voltage SPD for the protection of the terminal equipment) should compliment each other such that all AC dangerous energy transient effects are completely nullified. 


Said in a better and precise way, according to IEC 62305-4 whose emphasizes the use of coordinated SPDs for the protection of equipment within their environment, it does mean a series of SPDs whose locations and LEMP handling attributes are coordinated in such a way as to protect the equipment in their environment by reducing the LEMP effects to a safe level.


So there maybe a heavy duty lightning current SPD at the service entrance to handle the majority of the surge energy (partial lightning current from a Lightning Protection System (LPS) and/or overhead lines) with the respective transient over-voltage controlled to safe levels by coordinated plus downstream over-voltage SPDs to protect terminal equipment including potential damage by switching sources, for example, large inductive motors. Appropriated SPDs should be fitted wherever services cross from one LPZ to another. Coordinated SPDs have to effectively operate together as a cascade system to protect equipment in their environment. For example, the lightning current SPD at the service entrance should handle the majority of surge energy, sufficiently relieving the downstream over-voltage SPDs to control the over-voltage.


Poor coordination could mean that the over-voltage SPDs are subject to too much surge energy putting both itself and potentially equipment at risk from damage. Furthermore, voltage protection levels or let-through voltages of installed SPDs must be coordinated with the insulating withstand voltage of the parts of the installation and the immunity withstand voltage of electronic equipment.

Classification of Surge Protective Devices in EURASIA region: As described before, Surge Protective Devices are items of equipment whose key components are varistors, suppressor diodes or spark gaps. SPDs are used to protect other electrical equipment and electrical systems against impermissible high surge voltages and to create equi-potential bonding.


By IEC 62305-4 and IEC 61643-11, SPDs are grouped according to their application and protective function. The national installation specifications for low-voltage systems must be observed for product selection and installation, such as IEC 62305-4. These locations determine using SPDs in low-voltage systems with a nominal voltage of up to 1000 V and the product standard for safety in this range of voltage is IEC 61643-11.


According to these standards the SPDs are then splited into three types:


  • Type 1: Lightning current SPDs for the effects caused by direct or close-up strikes designed to protect the installation and equipment at the interfaces between lightning protection zones LPZ 0 and LPZ 1 (incoming supply). Type 1 SPDs are always recommended if the building has an external lightning protection system.

  • Type 2: SPDs for the effects caused by remote strikes, inductive or capacitive coupling, and switching surge voltages designed to protect the installation, equipment, and terminal devices at the interfaces between lightning protection zones LPZ 1 and LPZ 2 (main distribution and sub-distribution).

  • Type 3: Additional SPDs designed to protect particularly sensitive terminal devices in lightning protection zones 1 or 2, in order to further reduce the voltage level. These may include devices for permanent installation in distributions or portable protective devices in the socket area directly upstream of the terminal device that is to be protected.

Do you remember ANSI/IEEE C62.41 and C62.45 categories C, B, and A? You can see now that similarities with IEC 62305-4 are more than obvious. As well as UL 1449 and IEC 61643-11 fulfill the same function as a safety standard in each international region. 

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