FIPRES references of preventing fire hazards in electrical panels

vFPT reference operation

FIPRES - Fire Prevention and Overheating Control system, namely vFPTs – visual Fire Prevention Thermolabels were installed in Power Factor Correction panels on contactors’ cables and on fuse disconnectors’ cables. vFPT is a solution to help maintenance personnel during inspections to give the information about overheating occurred between two checks.

Installation of vFPT on contactors’ cables and on fuse disconnectors’ cables

After installation, some of vFPTs got activated after reaching activation temperature of 90°C. Mostly, 2 out of 3 vFPTs on the cable entry of a contactor have irreversibly turned to black.

vFPT operated on contactors’ cables

vFPT operated on fuse disconnectors’ cables

Reasons that could have led to overheating of live wires:

• overloading above the permissible rated operating current or rated active power;
• uneven distribution of the load over the phases;
• mismatch of operating conditions in terms of temperature conditions of ambient air, malfunctioning of natural or forced ventilation, malfunctioning of air conditioning devices in enclosed spaces;
• aging of the cable insulation over time;
• improper selection of equipment due to incorrectly selected cable cross-section;
• presence of internal hidden defects;
• overheating of capacitor banks connected to contactors of fuses.

 Actions that should be taken to eliminate the defect:

• performing an unscheduled infrared thermography control of the elements of the electric power unit in order to clarify the degree of heating;
• setting the element to a more frequent control (reducing the frequency of visual inspections);
• taking measurements of load currents and unloading of electric installation or distribution of loads more evenly by phases;
• checking the operating temperature of capacitor banks where cables got overheated.

It is essential to control temperature of capacitor banks in power factor correction panel as the increase in capacitor operating temperature every 10 °C above the normal operating temperature cause the service life of the battery reduced by 2 times. Due to overheating capacitor banks also might blow up and lead to all consequences of fire: threat to life, material damage, power supply interruption.

rFPT and FPA reference operation

FIPRES was installed in Rajasthan, India, photovoltaic (PV) plants of power 350 MW, 250 MW, 390 MW, 300 MW. 

Photovoltaic plant, Rajasthan, India

FIPRES was installed in combiner boxes of PV plants using FPA 24(4S) – Fire Prevention Alarm with 4 corded sensors and rFPT 130XL – remote Fire Prevention Thermolabel with activation temperature 130 °C and XL size that can be placed in the volume 1-4 m³. The dry contact output of FPA is connected to circuit breaker (CB) so that after detection of overheating the panel got tripped.

FPA 24(4S) installation in combiner boxes

The client has already faced the problem with blowing combiner boxes that led to stop of production of the whole PV plant. After installation of FIPRES, FPA got alarms from several panels due to overheating of contact connections.

rFPT 130XL operation reaching the activation temperature of 130 °C

Corded sensor of FPA 24(4S) and rFPT 130XL installation in combiner boxes

The information that client received after FIPRES operation:

• The panels were not designed to be installed in such extreme conditions as Rajasthan, the hottest state in India, where 50 degrees is an average temperature.
• Due to bimetallic connection between cable and insulated pin lugs, all connections were prone to overheating.
• Some of the connections were loosened due to improper torque during assembly.
• On some of the panels there were no shade to cover the panel.
• There was no clearance between two adjusted panels.

 Actions that should be taken to eliminate future overheating in combiner boxes:

• The panel design will be reconsidered to meet the environmental conditions.
• All contact connections with bimetallic connections will be changed to one metal connection.
• All contact connections will be tightened.
• The clearance between two panels will be increased.
• The shade will cover all combiner boxes.