Electrical Arc Across Conductors
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Electrical Arc Bridging Open
Electrical Arc Bridging Open
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Safety
Figure 10. Series Arcing
A parallel arcing event occurs when an additional current path to a conductor outside of the designed
current loop becomes available. The original current path of the system may not be interrupted; partial
power may still be generated on the string. Parallel arcs can be caused by insulation damage or other
damage to the system.
Figure 11. Parallel Arcing across strings
Detection of parallel arcing can be implemented with regular measurements of all the string currents and
neutral lines; an arcing event is indicated when the individual string currents in and out of the inverter do
not match. In
, the currents i1 and i1’ should be equal in normal operation. Any significant current
difference can be considered a dangerous condition. Parallel arcs can also be detected by the RD-195.
Detection of a series arcing event is not as straightforward as checking for imbalanced currents; using an
RD-195 is necessary. Use of current measurements in conjunction with an RD-195 provides a method to
detect and differentiate both types of arcs.
The appropriate response to detection of an arc is system dependant. While a series arc can be
extinguished be opening a relay in the path, which stops the current flow and therefore the arc,
disconnection can actually exacerbate a parallel arcing condition by forcing more current though the arc.
For many situations, shorting all positive and negative strings lines to ground will extinguish arcs. However
this may not be possible for some systems. How to handle an arcing event should be considered during
system design.
16
Safety
Caution must be used at all times while generating arcs. The high voltages present in a PV system pose a
lethal hazard. Incandescent metal sparks and open flame can be present. Use all necessary safety gear,
including Eye/Face protection, electrical gloves rated for the electrical conditions, and any other equipment
appropriate for the conditions. Texas Instruments assumes no liability for any damage or injury that may
occur.
17
Bench Evaluation Procedure
The RD-195 Photo-voltaic arc detection system is designed for reliable detection of electrical arcing
events without producing nuisance false positive detections. Evaluating the RD-195 poses some difficulty,
as the recommended setup requires a complete PV installation, including several PV modules and an
inverter. Inclement weather can also restrict the time available for evaluation. Basic evaluation can be
done using equipment available in a standard lab.
Required Equipment:
1. DC power supply with 200V/2Amps
2. DC power supply with 6v/150mA
11
SNOA564F – June 2011 – Revised December 2012
AN-2154 RD-195 DC Arc Detection Evaluation Board
Copyright © 2011–2012, Texas Instruments Incorporated
