Thermographic analysis of parallelly cables: A method to avoid misdiagnosis

• A method that conduces to more assertive diagnosis in parallelly conductors.
• In some cases, the colder connection may be the defective connection.
• Paper gives a model to estimate temperatures and currents in parallelly conductors.
• The experimental evaluation led to estimations with acceptable errors.

Thermography infrared technique is quite used in predictive maintenance. Thermographic analysis consists in associating regions with high surface temperatures to defects and failures. However, for some situation, such as parallelly conductors of the same phase, the warmer connection may be in accordance, and the colder one may be defective. If there is a “poor contact” failure in one lead, electrical current can be significantly higher in the cable with lower contact resistance and, consequently, lower intensity on the cable where the connections have higher resistance. This paper develops an analysis method that conduces to more assertive diagnosis regarding the identification of the faulty connection of parallelly conductors in low voltage electrical installations, non-invasively and under operation.