Information on lightning and surge protection in Smarthome and Industry
Updated on 1 July 2020
There are two real dangers for modern electronic products in Smarthome and Industry: compatibility problems due to technical progress and destruction due to surges. You can avoid the former by adopting the right strategy when selecting bus systems and components, and the latter by providing consistent protection against surges from the mains or from lightning strikes.
PROCESS AND EFFECT OF A LIGHTNING STROKE
Apart from cloud-to-cloud lightning, lightning is a spontaneous charge equalisation between the cloud and the earth. The charge equalisation occurs when the field strength exceeds a critical threshold (about 170,000 volts/m). The voltage is often several hundred million volts.
In a typical cloud-to-earth lightning flash, an excess of negatively charged water droplets initially causes a conductive flash towards the earth. This change in the electric field causes a massive increase in the positive charge carriers in the ground (due to influence). From the ground, the guiding flash from the cloud is met by a catching flash. This conductive flash ionises the air and makes it conductive. Now follows the actual main discharge, which can consist of several individual discharges in quick succession. This main discharge causes charge carriers to be exchanged between the cloud and the earth, and the current intensity can reach 100,000 amperes. In the case of an earth-cloud flash, the conditions are reversed. Typically, there are then several rapid, strong discharges.
The exchange of charge carriers leads to an average of negative charges being transported from the atmosphere to the earth, which globally increases the potential difference to the earth. A thunderstorm therefore only provides a local charge balance, but globally over the entire atmosphere it leads to an increase in the voltage, which is only gradually reduced by the transport of ions.
Due to the resistance of the ground, the high current flow leads to high voltage drops and thus to very considerable potential differences. In addition to the danger from a direct hit and mechanical and thermal effects, people are particularly endangered by these potential differences in the voltage funnel around an impact. Even the usual length of step can lead to a potential difference of several hundred to several thousand volts between the two feet in the close vicinity of the impact point (10 to 50 m, depending on the ground), which is compensated for by the body.
This effect also occurs in buildings, as their equipotential bonding system is connected to the ground. In the event of a nearby lightning strike, the earth potential (increased by the lightning strike compared to the surroundings) is conducted into the house via the equipotential bonding and distributed throughout the building via PE. PE is conductively connected to all metallic building components via the equipotential bonding rail ("PAS"). In the wider surroundings around the point of impact, the earth potential is lower. The potential difference will want to equalise itself there and will use all metal supply lines to the house (water and gas pipes, possibly sewage) as well as all electrical lines to telecommunication and especially to the remote earth in the local transformer station via the house connection. In order to be able to take the route via as many cores as possible, this voltage will attempt to penetrate the insulations between the protective equipotential bonding and the outer conductors.
The overvoltage created by the lightning strike wants to discharge itself via the house feeder towards the distant earth in the transformer station - and via the earth of all other house feeders. This is also one of the ways in which a surge voltage enters the house even in the case of a more distant strike. Via the foundation earths of the buildings closer to the point of impact and their house connection lines into the grid to the distant earths of the transformer station and the other buildings.
In addition, there are induced voltages due to the effects of the electromagnetic field around the lightning current in conductor loops.
What all these scenarios have in common is that these overvoltages seek compensation in their own or in distant earth potentials, thereby breaking through insulation. The main technical damage caused by lightning is the destruction of insulation and overloading of electrical and electronic components.
EXTERNAL LIGHTNING PROTECTION
The external lightning protection according to DIN EN 62305-3 is installed on the outer shell of the building. It consists of the air-termination systems, the down conductors and the earthing system. The task of the external lightning protection is to catch the lightning, to discharge it into the ground and to distribute it over a large area in the ground. The planning and installation of an external lightning protection system should be carried out by a certified specialist company.
Important: Whether external lightning protection is required for your building depends primarily on the building and possibly the fire protection and operational safety regulations. If you have external lightning protection installed, then it is mandatory that you also install internal lightning protection in accordance with DIN EN 62305-4. Because the external lightning protection is connected to the equipotential bonding rail. Any lightning strike approached by the external air-termination system is conducted to the ground earth electrode and thus the PAS, and is thus also conducted into the building.
INNER LIGHTNING PROTECTION
You cannot stop the surges from lightning. The main measure against the breakdown of insulation and the prevention of dangerous sparking is the short-circuiting of all lines at the moment of the overvoltage by means of suitable components, which can carry the lightning current.
Effective surge protection consists of several stages in accordance with the lightning protection zone concept as per IEC 62305-4:2010. Buildings are divided into zones with different levels of risk potential. Depending on the zone, the appropriate arrester types are to be used.
We manufacture surge arresters and surge protection modules for the bus systems commonly used in smarthomes and offer them under the name "BlitzART" in this shop.
BLITZART OVER VOLTAGE PROTECTION MODULES
Under the brand name "BlitzART" we offer surge protection modules as insulation and device protection for electronic bus systems and serial interfaces. Our modules are highly optimised and are characterised by:
The most modern components.
Extremely low protection levels
Extremely short response time
At present, we only offer the surge protection module for KNX. It is characterised above all by a fourfold lower protection level - compared to the competition - which means that KNX components are considerably better protected (1/4 voltage means a reduction to 1/16 of the power that still has to be withstood by the KNX device itself). In addition, our surge protection module switches significantly faster than the modules of the competition.
In a few weeks we will offer modules for 1-Wire, RS-232, RS-485 (also Modbus RTU and DMX) and CAN. Please subscribe to our newsletter and you will be informed promptly.