David G. Loucks

A Step Closer Toward Maintenance-Free Gear

A difficult-to-predict electrical failure is the continuity failure. Pressure junctions are common problem sources for continuity failures. Available tools to search for pressure-junction problems include low-resistance testing, temperature monitoring using physical contact between sensor and heated part, pyrometer temperature monitoring, infrared photography, and visual inspection. While each method is effective, each of these methods has one or more disadvantages. This paper will describe a breakthrough patented method of directly calculating conductor and pressure-junction impedance, resistance, and reactance using the noisy harmonic-laden switching-transient-laced (in other words, normal) load current flowing through an electrical distribution system. This technique then provides the solution to the problem of how to detect a conductor-path-impedance change of only a few tens of micro-ohms using conventional protective and metering devices without the need to de-energize the equipment or without the need to inject currents.

Calculating Incident Energy Released With Varying Ground Fault Magnitudes on Solidly Grounded Systems

The IEEE Standard 1584-2002 is the recognized standard regarding the calculation of incident energy output from an ac three-phase arcing fault. While that standard does not provide incident energy calculations for the much more common single-phase-to-ground fault, it explains that the expectation is that such a ground fault will either self-extinguish or escalate into a three-phase fault. If the fault escalates, the three-phase calculations can be used. The amount of time that the arc burns as a single-phase fault before escalation is not defined, but a reference document used by the 1584 standard defines this escalation time as one to two cycles. No attempt is made to calculate the incident energy released during this escalation period. While exact answers to the question of how much additional energy would be released are best answered through additional testing, this paper attempts to bracket likely high and low ranges of incident energy that could be released from an arcing single-phase-to-ground fault prior to escalation into a three-phase fault. As this paper only provides a theoretical basis for the calculation of additional energy released from arcing ground faults prior to escalation, it is the opinion of the author that future standards should include testing of incident energy released from faults that begin as low-level arcing ground faults.

Infrared windows applied in switchgear assemblies: taking another look

Maintenance of electrical power distribution assemblies applied in industry has been critical in assuring facility uptime and reliability. One important metric in assuring reliability is electrical terminations of energized conductors. During normal energized service, terminations both at conductor bus joints and at cable terminations are subject over time to thermal expansion and contraction, ultimately resulting in loosened connections and excessive heat. Deteriorating terminations left unchecked will ultimately fail, resulting in electrical hazards for personnel and also costly loss of production. Infrared (IR) inspection has proved to be an excellent maintenance method used to identifying problems with loose electrical terminations. However, the design of Internal Arc Classified (lAC) switchgear assemblies to address arc-flash concerns has changed assembly designs that now limiting line of sight access necessary for IR inspection via windows. This paper will discuss global Standards, how they affect switchgear designs and application ofIR windows, then present some alternative technologies that in some applications may be more suitable.

Infrared windows applied in switchgear assemblies: Taking another look

Maintenance of electrical power distribution assemblies applied in industry has been critical in assuring facility uptime and reliability. One important metric in assuring reliability is electrical terminations of energized conductors. During normal energized service, terminations both at conductor bus joints and at cable terminations are subject over time to thermal expansion and contraction, ultimately resulting in loosened connections and excessive heat. Deteriorating terminations left unchecked will ultimately fail, resulting in electrical hazards for personnel and also costly loss of production. Infrared (IR) inspection has proved to be an excellent maintenance method used in identifying problems with loose electrical terminations. However, the design of internal arc classified switchgear assemblies to address arc-flash concerns has changed assembly designs that are now limiting line of sight access necessary for IR inspection via windows. This paper will discuss global standards, how they affect switchgear designs, and application of IR windows and then present some alternative technologies that, in some applications, may be more suitable.