Lightning over Table Mountain

Want to protect your electronic systems from Lightning and Load-shedding?

The lightning density on the highveld is increasing as the globe warms up. The 2018/2019 rainy season has been one of the most intense lightning seasons experienced in Southern Africa in recorded history.

Scientists say that the increase in violent thunderstorms is an accurate measure of climate change and global warming.

This means that thunderstorms in Southern Africa and especially here on the highveld are going to become more intense and violent. Coupled with the high soil resistivity levels we have on the highveld, and we can expect to experience huge losses of electronic equipment from thunderstorms.

To make things worse, we have a power utility with ageing infrastructure and the inability to keep up with the power demands of the nation.

This guide is intended to provide you with the knowledge you need to protect your electronic systems and those of your clients.

News Headlines

“South Africa has one of the highest lightning ground-flash densities in the world,” says SA Weather Service’s Tracey Gill, who has made it her life’s work to study and document this phenomenon.

Mail and Guardian, 15 April 2008

“The insurance division of one of South Africa’s and Africa’s largest banks reported in 2012 there has been… a 402% increase year-on-year in weather-related damage claims including from lightning,” Molewa said.

News24, 12 November 2015

South Africa has the highest soil resistivity in the world.

Prof. Ian Jandrell (University of the Witwatersrand), 25 April 2017

According to the SA Weather Service, South Africa has one of the highest incidences of lightning related injuries and deaths in the world (more than 200 deaths on average each year), with only the USA and India experiencing more deaths on average per year.

The Citizen, 20 December 2018

What is lightning?

Lightning is the occurrence of a natural electrical discharge of a very short duration and high voltage between a cloud and the ground or within a cloud, accompanied by a bright flash and thunder.

Did you know that it takes 30,000 volts to ionise the air and have an electrical spark that jumps 1centimeter?

What is a power surge?

Power surges, (sometimes called voltage surges) are fast, temporary spikes (transients) in voltage within an electrical circuit. These surges, which are unavoidable, occur when something boosts the electrical charge at some point in the electrical circuit.

What are power spikes?

The words spike or surge are often used to describe electrical transients. These transients are very fast temporary increases in voltage, current or a transferred electrical energy in an electrical circuit.

These transients can be caused by lightning, electrical switchgear, electrical motors or electrical power generation machines. This means that your electrical and electronic equipment can be damaged by spikes from other sources other than lightning.

Eskom’s ageing infrastructure and their implementation of load-shedding is a major cause of electrical transients in South Africa.

The following diagram illustrates the waveform of a typical mains supply and that of the same mains supply with transients.

Overvoltage transients on 220Volt mains sinewave

Does lightning protection work?

Yes, lightning protection does work! Watch this video.

How does lightning cause transients that damage your electronics?

Lightning causes transients in 2 ways:

  1. Resistive coupling
  2. Inductive coupling

Let’s look at these in more detail. Although we are referring to a CCTV system, the same will apply regardless of whether it’s a CCTV, IT or other electronic communications system.

1. Resistive Coupling

Resistively coupled transients are caused by the difference in potential between two earth points.

Resistive coupled lightning damage

In the diagram above lightning strikes a nearby tree causing the camera’s local earth to rise to a very high potential. The monitor in a nearby building is connected to its own local earth which is at a much lower earth potential. The camera and the monitor are not only referenced to their own local earth points but they are also connected to each other by video, data and power cables. This causes a difference in potential (voltage) between the camera and the monitor.

The difference in potential results in current flowing through the system and damaging the electronics of the system. Remember that this happens very fast, in microseconds.

You can only protect against this type of damage by connecting the 2 earthing points together with a large enough conductor to ideally achieve a resistance of 10 ohms or less between the 2 earthing points. This is known as an Equipotential Bonding Earth.

2. Inductive Coupling

Inductively coupled transients are caused by electromagnetic pick-up.

Inductive coupled lightning damage

In this diagram, lightning discharges to a lightning conductor creating an electromagnetic field. The video, data and power cables of the CCTV system happen to be in the path of the electromagnetic field. A portion of the electromagnetic field is induced onto the CCTV system cabling causing a transient (surge) overvoltage across the equipment of the CCTV system.

Hollywood has illustrated this concept beautifully as weapons in science fiction movies like the Matrix. In the Matrix, an electromagnetic pulse weapon is discharged damaging all electrical and electronic systems within the range of the weapon thereby disabling all the machines that are attacking the movie’s heroes. In reality, such an electromagnetic pulse discharge would not be visible but would be felt by everyone in close proximity.

In the above diagram, the two earthing points would need to be connected just like the resistive coupling example and surge arresters on the communication and power lines would be required. These surge arresters will safely arrest the transients (surges) and dissipate the transient (surge) through the earthing network. But if the transients (surges) exceed the rating of the surge arresters, damage to electrical and electronic equipment can be expected.

Which type of damage should you protect against?

The answer is simple… BOTH! We do not know when and where lightning will strike. We do not know what the environmental conditions will be at the time. We need to protect our systems for both eventualities.

How do electrical systems cause transients?

The current flowing in a circuit creates a magnetic field in which energy is stored. When the current source is turned off and the current ceases to flow in the circuit. The stored energy is then released and manifests itself as a transient (surge).

Sources of transients (surges) in an electrical system are ageing switchgear, the back electromotive force (EMF) from inductive loads such as transformers and motors, and LED lighting. Our electricity provider’s network is also a source of transients (surges), which will be explored in the next section.

Here are some examples of transients (surges) that occur both within our own electrical system and external to our electrical system (from the electricity provider).

Example 1

Trasient caused by a load-dump

Load Dump from Inductive Supply or Load such as an electric motor

Example 2

Trasient caused by a switch opening

Transients Caused by Switch Opening

Example 3

Trasient caused by a ring wave

100 kHz Ring Wave Surge caused by a voltage surge exciting the natural resonant frequency of the indoor wiring

Example 4

Overvoltage surge

Mains overvoltage resulting from the temporary loss of the neutral

Standard mains surge protection only offers threshold clamping which is ideal for protection against most lightning transients (surges) and for protection against a temporary overvoltage condition as shown in example 4.

Active sinewave tracking surge protection is required to protect against all these different transients (surges) highlighted above.

How do you protect your electronic systems when everything is working against you?

Let’s start with the most important component, your electrical mains supply.

What is an electrical earthing system?

In an electrical installation, an earthing system connects the exposed-conductive parts of the installation by means of protective conductors to a main earthing terminal. The main earthing terminal is connected to an electrode network that is in contact with the Earth’s conductive surface for safety and functional purposes.

What a mouth full! It simply means that the appliance’s exposed metal parts are connected to an electrical earth point. The electrical earth point, in turn, is connected to a network of earth rods in the ground. This is for your safety, it means that you won’t be electrocuted if your appliance goes faulty because that electrical energy is safely directed to the earth.

What a mouth full! It simply means that the appliance’s exposed metal parts are connected to an electrical earth point. The electrical earth point, in turn, is connected to a network of earth rods in the ground. This is for your safety, it means that you won’t be electrocuted if your appliance goes faulty because that electrical energy is safely directed to the earth.

So, if you find someone cutting the earth wire of a CCTV or IT system to resolve a ground fault, stop them! They are making the installation dangerous! The electrical earth is there to protect the people that occupy that structure from electrocution.

How do you install an electrical earthing system?

A soil resistivity test is conducted. Soil resistivity is a measure of how much the soil resists the flow of electricity. Based on the results of this test the number of earth rods required, the length of the earth rod and the spacing of the earth rods are calculated. Remember that the soil resistivity changes from the rainy season to the dry season. The earthing network must be adequate to provide a good conductive surface during the dry months.

Fluke Soil Resistivity Meter

Fluke Soil Resistivity Meter

The earth rod network is connected to a central earthing point in the electrical distribution board. Each electrical point in the building has a protective conductor (earth wire) connecting it to the central earthing point.

Does a single earth rod make a good electrical earthing point?

NO! You must know what the soil resistivity is to determine what will be adequate.

What about crow’s foot arranged earth rods?

NO! You must know what the soil resistivity is to determine what will be adequate.

Earthrods in a crows foot formation

The theory behind the crow’s foot arranged earth rods is that the three vertical earth rods are supposed to make it possible to find ground of different types to reduce the earth resistance.

The problem is that the earth rods are so close together that the likelihood of finding different kinds of soil is unlikely, especially here on the Highveld where the ground is generally dry. I will agree that three earth rods are better than just installing one.

Why is electrical earthing so important?

The electrical earthing system makes your electrical installation and your appliances safe so that you don’t get electrocuted when a fault occurs.

Lightning and surge protection devices have an electrical earthing terminal that must be connected to the electrical earthing system. The electrical earthing provides a path for safely dissipating overvoltage transients (surges).2

Why do you need Mains Supply surge protection?

Today’s electronics, appliances and equipment need consistent and clean power. Transients (surges) on the power input can damage your favourite sound system or any other electrical device either by a single transient (surge) or by multiple transients (surges) over time.

In the mid-1990s a European Study by Unipede found that 80% of all transients (surges) have an amplitude of up to 1.2KV (Kilo Volts) and have a duration of 1 to 10micro-seconds. At the time, these transients (surges) occurred more than 10 times per day and were caused by multiple sources on the power grid. This is on a power grid that is considered stable.

Here we focus on transients (surges) from the Power Utility and other inductive loads like motors but let’s not forget what we learnt in Part 1 about Lightning.

Damage from transients (surges) can be classified as follows:

  1. Hard failures.This permanent damage is caused by a single transient (surge) of significant amplitude. This is typical of lightning transients (surges).
  2. System interruptions.This is a temporary malfunction that can be rectified by cycling the power of the equipment and no permanent damage occurs.
  3. Latent failures.This type of damage is the most disputed by insurance companies and occurs from continuous exposure to transients (surges) and Electromagnetic Interference (EMI) or Radio Frequency Interference (RFI). These transients (surges) erode the performance of electronic equipment and eventually cause permanent damage. Typically, this damage is caused by transients (surges) from the utility power provider or inductive loads such as motors on the property. EMI/RFI is the most under-protected type of transient (surge) and requires an Active Sine Wave Tracking Surge Protection Device.

What type of surge protection do you need?

Most mains surge protection devices available in the market place use one of the following technologies:

  1. Threshold Clamping Technology.This is traditional surge protection technology whereby surges are clamped once the threshold of a Metal Oxide Varistor (MOV) is reached. This is the most common technology as it’s small and can be housed within most existing electrical distribution boards. The disadvantage of these devices is that the left-through overvoltage transients (surges) can be substantial, as much as the voltage threshold clamping rating of the device.

  2. Threshold Clamping Technology surge arrester

    Threshold Clamping Technology

  3. Sine Wave Tracking Technology. This technology is active surge protection and:
    1. suppresses high frequency, low energy ring wave transients (surges) at any phase angle that the surge may occur. This is typical of loads that generate a back EMF.
    2. suppresses RFI and EMI.
    3. with conventional light bulbs being replaced with LED bulbs, household appliances being fitted with energy-saving electronics instead of mechanical controls and the use of inverters has led to EMC (Electromagnetic Compatibility) interference. Sine Wave Tracking surge protection suppresses the noise generated by EMC related interference.

    These devices have very small left-through voltage transients (surges) but are substantially larger in size.

    Sine Wave Tracking Technology surge arrester

    Sine Wave Tracking Technology

Which is the best technology?

The best mains surge protector is one that incorporates both Threshold Clamping Technology and Sine Wave Tracking Technology. This hybrid surge protector not only offers excellent protection from lightning but is also an excellent protector from what South African’s call load-shedding.

Load-shedding is a term used in South Africa for when our electricity provider can’t manage the load requirements of the country and implements scheduled rolling black-outs.

Who can install Mains Surge Protectors?

In South Africa, you will require an electrician to fit these devices.

How are Mains Surge Protectors deployed on-site?

Let’s look at a house as an example. You would install a 60KA or 40KA device at the electrical distribution board on the incoming Mains. Then you would fit a 20KA unit at points not under the same roof, such as your pool motor and sliding gate motor.

Should you have sensitive electronics such as your sound system or home theatre system then an inline 20KA device can be used to protect them and filter out the side effects of transients (surges) on the performance of these devices.

Below is a picture and a diagram of a 3-phase unit. These units are wired to the secondary (output) of an earth-leakage breaker.

In the case of the 20KA units which are connected close to the appliance (such as a gate motor); the unit can be wired directly to the back of the power socket or the secondary of isolator local to the device being protected.

Should there be extreme over-voltage transients (surges) the surge protector will trip the earth-leakage breaker or the circuit breaker for the local circuit.

3-Phase Active Sine Wave Tracking Surge Arrester

3-Phase Active Sine Wave Tracking Surge Protector

The Inline Mains Protector

If you are not an electrician and you only want to protect the system you are installing, we have an inline device available for you. Details are available at

That being said we strongly recommend that the entire electrical system be protected.

Why do you need Low Voltage Signal protection?

Low voltage signals can be transmitted over extraordinary cable lengths. In the case of RS-485, these cable lengths can be up to 1000m and in the case of computer networking cable up to 100m. However, considering that the most widely used networking switches have 24ports, this means up to 24 signal cables with a maximum length of 100m.

Your simple IT network at the office has up to 2400m or 2.4km of cable. That is 2.4km of wire that is suspectable to electromagnetic pick-up from lightning during a thunderstorm. I consider this to be a broad antenna array. The question is not whether your electronics will be damaged by lightning but rather when will you experience lightning damage.

Use the correct surge arrester!

Choose the correct surge protector for the signal type; that is if you have a Gigabit PoE signal use a Gigabit PoE surge arrester. Should you have a HD-TVI or HDCVI signal use the correct surge arrester for these signal formats. The bottom line is, use the correct arrester for the specified data line.

Surge arrester design.

A surge arrester should consist of TVS diodes and GDT components.

A TVS (Transient-Voltage-Suppression) diode is a clamping device, suppressing all overvoltage transients (surges) above its breakdown voltage. It automatically resets when the overvoltage transients (surges) go away. They can respond to overvoltage transient (surge) events faster than most other types of circuit protection devices. TVS diodes are available with operating voltages from 5volts to 500volts and transients (surges) suppression up to 10KA (Kilo Ampere). TVS Diodes are generally used to protect against lightning strikes, inductive load switching, and electrostatic discharge (ESD).

A GDT (Gas-Discharge-Tube) is a glass-enclosed device that is sealed and contains a special gas mixture which is trapped between two electrodes. GDTs conduct electrical current after they become ionized by overvoltage transients (surges). These devices can conduct a relatively high amount of current for their size and can handle some very large transients or several smaller transients.

GDTs also take a long time to trigger, which permits a higher voltage spike to pass through before conducting a significant amount of current. They are available with operating voltages from 75volts to 6000volts and transient (surge) suppression up to 20KA. It should also be noted that Gas-Discharge-Tubes (GDT) has a specified life-span which should be quoted on the specification sheet of the surge arrester, at end-of-life the Gas-Discharge-Tubes (GDT) should be in short-circuit and your communications link will stop working until such time as the surge arrester is replaced.

Put in simple terms TVS diodes do the light work but respond very fast to transients (surges) and GDTs do the heavy lifting but respond slower than TVS diodes. Therefore, a combination of both technologies is required to produce an effective surge arrester.

Note that circuits designed with these components are designed to safely dissipate transients (surges) to an electrical earth. Think of it as a device that removes transients (surges) and redirects them to a safe place (the electrical earth).

Let’s have a look at some examples of surge protection devices

Example 1

This example is a very popular (in South Africa) Gigabit PoE surge arrester. Note the electronic circuit board on the left-hand side was removed from the plastic enclosure on the right-hand side for this illustration.

Poor quaility POE surge arrester

Examine the electronic circuit board closely and note the 8 white components on the circuit. These white components are the Gas-Discharge-Tubes (GDT), they are the only components on this electronic circuit board. This surge arrester has no Transient-Voltage-Suppression (TVS) diodes, also the GDTs have a rating of 90volts. What does this mean?

  1. This surge arrester responds slowly to transients (surges) as the fast responding TVS diodes are missing.
  2. PoE is a 48volt signal and the Gas-Discharge-Tubes (GDT) only start working from 90volts. This means that there is a window from 50volts to 90volts that is not protected. The equipment being protected by this surge arrester could be damaged by the transients (surges) before this surge arrester even starts working.

Note the metal tag at the bottom of the electronic circuit board, this is the connection point for an electrical earth.

Example 2

2KA POE surge arrester

In this example, we have a DIN-Rail mount BFR Digital Gigabit PoE surge arrester. Note the 8 white Gas-Discharge-Tubes (GDT). Also at the bottom of the electronic circuit board note the 8 small black diodes with a large black axial diode underneath them; these are the TVS diodes that offer the fast response to transients (surges).

Again, note the green/yellow wire at the top of the electronic circuit board for the electrical earth connection.

Can this circuit be improved? Yes, as this is for a Gigabit high-speed signal, isolation can be offered between the Gas-Discharge-Tubes (GDT) and the electrical earth. This added isolation would ensure that no electrical interference is introduced onto the Gigabit signal from the electrical earth.

This is done by placing a MOV (Metal-Oxide Varistor) between the Gas-Discharge-Tubes (GDT) and the electrical earth.

A varistor is an electronic component with an electrical resistance that varies with the applied voltage. That means that when the applied voltage across the varistor reaches the rating of the varistor, the varistor starts conducting (let’s current flow).

Let’s look at the next example.

Example 3

10KA POE surge arrester

Above is a picture of our POE-GSA-01 (Gigabit PoE surge arrester). Note the dark yellow components, these are the Metal-Oxide Varistors (MOV) that offer the isolation from the electrical earth.

What is the difference between the device, in example 2 and example 3?

  1. Example 3 offers isolation from the electrical earth.
  2. Example 3 has Gas-Discharge-Tubes (GDT) with a higher current transient (surge) rating, 10KA compared to 2KA in example 2.
  3. The Gas-Discharge-Tubes (GDT) in example 3 has a failsafe. It’s the metal cap on the Gas-Discharge-Tubes (GDT) and its function is to facilitate another path to the electrical earth in the event of the surge exceeding the rating of the Gas-Discharge-Tubes (GDT) or in the event of the Gas-Discharge-Tubes (GDT) failing.

What happens if the transient (surge) exceeds the rating of the surge arrester?

Should the transient (surge) exceed the rating of the surge arrester chances are that the equipment being protected will suffer damage. This is where the failsafe functionality offered by the Gas-Discharge-Tubes (GDT) used in example 3 (BFR Digital, POE-GSA-01 arrester) would offer additional protection beyond the rating of the Gas-Discharge-Tubes (GDT).

NOTE: In the above examples, we have only discussed Gigabit PoE surge protection but the principles remain the same regardless of the signal format you wish to protect. Some slower signal formats may not require the isolation from the electrical earth as explained in example 3.

What is an insertion loss?

An insertion loss is the loss of signal power resulting from the insertion of a device in a transmission line or optical fibre line. In the case of surge protection, the signal will experience an insertion loss for every surge arrester inserted on the line. Remember that both sides of the communication line will need to be protected, which means two surge arresters on the communication line, each with its insertion losses.

The implications to your installation are that you will not achieve the maximum cable distance specified by the transmission equipment.

How do you to install surge arresters?

Installing surge arresters

Above is an example of an IP POE CCTV system, remember that the principle remains the same regardless of the signal format.

Starting on the camera end; install an outdoor POE surge arrester as close to the camera as possible, preferably within 30cm and connect the surge arrester’s earth wire to the electrical earthing point.

Inside the field enclosure, install one surge arrester per incoming network cable. Keep the incoming field cables away from the surge arrester’s output cables. Should you keep these two cables together you risk electromagnetic induction on the surge arrester’s clean output, this in effect bypasses the surge arrester. Again, connect the surge arrester’s earth wire to the electrical earthing point.

Don’t forget to install a mains surge arrester on the incoming 220volt mains supply.

All surge arresters must connect to their local earth rod network. An Equipotential Bonding Earth Wire connects the two earth rod networks. The resistance of this earth connection must be less than 10 ohms. Also, the incoming 220volt mains earth must connect to the local earth rod network. Remember, the objective is to ensure that there are no differences in potential between any of the earthing points.

Many technicians ask if they can use a metal structure such as a metal pole for earth bonding. Although you could make use of a metal structure, you can’t ensure the electrical continuity of the metal structure. Additionally, in most cases, the electrical resistance of the metal structure is much higher than 10 ohms. It is better to use a copper or aluminium earth wire of the correct thickness.

What is the difference between surge protection and opto isolation?

  1. Surge Protection
    Surge protection devices or surge arresters are devices designed to protect electrical and electronic equipment from transients (surges). This is done by dissipating the transients (surges) safely through an electrical earthing network.
  2. Opto isolation or Optical Isolation
    With opto isolators we convert the electrical signal to light, this light is then transmitted across an air-gap, received and converted back to an electrical signal. The size of the air-gap determines the isolation rating of the device. It is the same principle as in the case of fibre optic transmission.

Why would you need opto isolation?

To date, our largest opto isolation demand is for the protection of the wiegand ports on biometric readers.

Wiegand opto isolator

Here is a picture of our I-WIE5, this product was specifically designed to protect the wiegand port of a Morpho fingerprint biometric reader but it will work on any wiegand port. This particular model offers opto isolation for D0, D1, LED1 and LED2. The power is isolated through the built-in 12volt DC-to-DC convert.

With the I-WIE5 there is no electrical connection between the input and the output. When installing the I-WIE5 device do not power your reader via the PoE port, rather power the reader from 12volts through the I-WIE5 12volt port. Should a standard Ethernet connection be used, the Ethernet magnetics (communications transformer) offer isolation between the switch and the reader.

However, should PoE power be used then this isolation is broken as PoE power is injected into and extracted from the circuit before the magnetics (communications transformer). The PoE portion of the connection introduces the potential for ground faults and the reader will no longer be completely isolated from its external environment.

It is still good practice to install an Ethernet surge arrester on the Ethernet port.

Surge Blockers

Surge Blockers save client 1 million Rand and land him a multimillion Rand deal.

In 2019, I’m sitting at home thinking I have this new Surge Blocker technology but how do I tell people about it? How do I show people that it works? My wife suggests that I make a video, can you believe it? Introverted me making a video! Anyway, what’s there to lose? So, I make two low budget videos with my cell phone.

So far, one has had 130 views and the other 60 views. Not a roaring success but they have increased sales from nothing to sales of 400 units last month.

Then an old client calls me out of the blue. He wanted to know what magic trick I used in the video. I said come have a look at the lightning simulation test for yourself.

After confirming the simulation for himself, he revised a deal he had been working on by removing all the surge arresters, earth rods and earthing conductors. By replaced it with Surge Blockers, this saved R11,000 per perimeter camera and R1,023,000 across 93 cameras. This saving has helped him close a multi-million Rand deal.

This video showcases the earthing concepts we have covered and our latest Surge Blocker technology.

What is a Surge Blocker?

Our new series of High-Speed Surge Blockers are designed to protect against faults caused by short circuits, induction and lightning surges. Unlike traditional surge arresters, Surge Blocker Devices do not need an Electrical Earth connection.

The Surge Blockers will trip in less than 1 microsecond when the surge current reaches 750mA. They work like a switch, when a surge is detected the surge blocker disconnects the field cable from the equipment you want to protect.

Surge Blockers, block surges and provide an effective barrier behind which sensitive electronics will not be exposed to large voltages or currents during surge events. After the surge event, the Surge Blocking Device will automatically reset.

How to install Surge Blockers

Installing surge blockers

Above is an example of an IP POE CCTV system, remember that the principle remains the same regardless of the signal format.

Starting on the camera end; install an outdoor POE Surge Blocker as close to the camera as possible, preferably within 30cm. It is essential to isolate the camera from the metal pole.

Inside the field enclosure, install one surge blocker per incoming network cable. Keep the incoming field cables away from the surge blocker’s output cables. Should you keep these two cables together you risk electromagnetic induction on the Surge Blocker’s clean output.

Again, don’t forget to install a mains surge arrester on the incoming 220volt mains supply.

Here is the BIG SAVING, there is no need for earth rods and Equipotential Earth Bonding. However, it is essential that you isolate all field equipment from all metal structures.

In summary:

  1. You must protect both ends of the signal cable.
  2. You must protect the 220 volts mains supply.
  3. You must avoid any potential difference between multiple earthing points. This is done through the installation of Equipotential Earth Bonding.
  4. Know what you are buying! Now that you understand what the components in your surge arrester do, only buy quality surge arresters.
  5. Surge Blockers simplify the installation by doing away with the need for Earthing and Equipotential Earth Bonding.

Surge protection is an all-in affair. It won’t work if you don’t install all the components.

Thanks for reading my blog!

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