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HV safety May 2020

Posted by tiziano on
HV safety May 2020

Introduction to safety

In a site where experiments with high voltage are shown and explosions and other crazy stuff are described, a section about safety cannot be missed.

As everyone has their own safety “needs” but, before starting experimenting or taking components we would suggest this list thanks to which you could learn or understand how to practise this hobby. Of course, we will never stop learning so there will be changes or updates of this safety guide and all your advises are welcome.

“Up to the coffin, you learn”

Italian proverb

If you are unfamiliar with high voltages start with something harmless and when you begin to understand those things, gradually increase the level: mosquito blade, electronic neon transformer (3kv), MOT (dangerous but very long discharges! Before using it watch the discharges made from others or on the high voltage sources section), etc…

Electrical hazards

Just a few tens of mA for a few milliseconds are enough to kill you! MOT, neon sign transformer, potential transformer and specially charged capacitors can supply much higher currents! Do not underestimate that!

Distances and safety

High voltage can jump even at impressive distances, voltages above 15kv become unpredictable, the distance between two live objects is 0.5m for 100kv. The distance between you and the powered part must be much greater. Above 5kv of potential 2 meters are recommended. If you have a 100kv source, you should already know what to do.

Safety with capacitors

After their usage, capacitors must be discharged and short-circuited (in particular if they do NOT have discharge resistors): they have been able to keep their charge for long periods or to be electrostatically charged. For small capacitors (<5J), the discharge resistance, after the test, is sufficient, however, discharge them with a cable: the discharging resistance takes several minutes to discharge the capacitor, otherwise it will discharge them during the test or it will dissipate too much power.

Electronics and… safety


High voltage discharges could create problems for electronic pieces of equipment or interference with them, so try to stay in a room with the least pieces of equipment as possible and to have a good grounding. Pacemakers are also electronic devices, so if you have spectators, warn them and DO NOT CARRY OUT such experiments if you had one.


If you have high voltage components, remember that they must NOT present a danger to those who access to them: high voltage components can contain toxic substances, especially PCBs (Polychlorinated biphenyl).

If you find a label like this you can be sure that it DOES NOT contain PCBs.
More information in files on this article.

PCBs is a family of additives added in oil to improve its electrical characteristics. Many people think it is nothing special but you should avoid it. In most parts of the world, it was used until 1982/1984, however, in Russia, it was used until the 90s.

Before taking old appliances filled with oil, try checking this list:

If you find that your equipment contains PCBs but is too good to be thrown away, use it AT YOUR OWN RISK, maybe try to clean it. When it is very neat put it in some containers to avoid oil spills after a leak. Disposing pieces of equipment containing PCBs can be very complicated and it is currently prohibited to use them.


Another thing not to be underestimated is ozone, produced in large quantities by discharges and corona effect. Above certain concentrations, it is particularly toxic so it is recommended to keep your room vented or do those experiments at open-air spaces.

Be safety with radiation

Vacuum tubes, bulbs etc, if subjected to high voltage can produce x-rays.

Electric arcs, especially high currents (MOT) can produce UV radiation so it is recommended to wear sunglasses or welder lenses during such experiments.

Other safety pieces of advises

Discharges with capacitors, faults and electric arcs can be very noisy so it is better to wear ear protections and have lenient neighbours!

High energy discharges can cause explosions and project splinters and pieces of incandescent metal everywhere, so it is better to contain them in a fairly resistant container with vent holes for hot air.

Discharges or breakdowns could cause a fire so you must always be ready to extinguish it. Obviously, before throwing water or doing such things, remember to make yourself electrically safe disconnecting power and discharging capacitors!

See you later!

That is all for now. There will be other safety updates in the future. If you are interested in our blog go and read other posts.

 see you later!

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