AM1 Arc Monitoring to PV-Systems
An electric arc, or arc discharge, is an electrical breakdown of a gas that produces an ongoing plasma discharge, resulting from a current through normally nonconductive media such as air. An arc discharge is characterized by a lower voltage than a glow discharge, and relies on thermionic emission of electrons from the electrodes supporting the arc. An archaic term is voltaic arc, as used in the phrase "voltaic arc lamp". (source: wikipedia)
General trigger in the reality of PV systems are:
Poor solder joints (cold solder joint), loose connections, corrosion, ground fault, Faulty insulation (Source: TÜV Rheinland)
Why Arc Detection is important to photovoltaic systems
- permanent flow of energy in a solar generator during light/sun exposure with high DC voltages up to 1000 volts and fairly high DC currents is critical to all parallel and series resistances in a string like cable connectors, junction-box connectors, bypass diodes, but also decreasing insulation resistance of solar cables, aging effects and many others
- permanent climatic influences like temperature, humidity and others mean a permanent stress (corrosion) to contact materials inside connectors and junction boxes, increasing the contact resistance
- on animal farms ammoniac gases could occur with accelerated corrosion of contacts forcing the emergence of arcs.
- once an arc occurs, there is an extremely dangerous brightness of light and a very high temperature of the plasma of about 3000C causes many materials to catch fire immediately with consequential damages
- older solar generators are especially critical to arcs as their cabling and connector system lost insulation resistance (mechanical influences) or have increased contact resistance due to corrosion
- a detection of arcs can prevent fire and consequential damages by turning off/short- circuit the solar generator, preferably each module in the string as realized by " PV SAFETY BOX" procedure. depending on the size of the PV generator and number of strings, there is need for integration of several arc detect circuitries in only one box
AM1 is offering a very inexpensive and space saving application for arc detection. A small box was developed to carry one to five single arc detect circuitries built as daughter boards to be plugged in a motherboard.