Michel Landry

An Improved Vibration Analysis Algorithm as a Diagnostic Tool for Detecting Mechanical Anomalies on Power Circuit Breakers

This paper deals with the successful application of vibration analysis for circuit-breaker (CB) diagnostic testing with the aim of detecting mechanical anomalies in CB drive mechanisms and other moving parts in the interrupting chamber. An improved dynamic time warping algorithm was developed. Several case studies of defective mechanical components of SF6 power CBs equipped with hydraulic or spring-loaded drive mechanisms are presented. It is foreseen that vibration analysis can be used as a diagnostic tool for all CBs whenever mechanical anomalies are suspected.

A Complete Strategy for Conducting Dynamic Contact Resistance Measurements on HV Circuit Breakers

Dynamic contact resistance measurement (DRM) is known as an effective technique for assessing the condition of power circuit-breaker (CB) main contacts and arcing contacts. In some SF6 gas CBs, the metallic fluorides (white or gray powder) produced during the arc quenching process mask the actual breaker contact resistance. In this case, the standard DRM method of injecting 100 A dc is no longer applicable. The following paper proposes a complete strategy for conducting DRM on high-voltage CBs based on three relevant parameters: breaker contact speed (low or rated), injected current values (100-2800 A dc), and the presence of metallic fluorides deposited on breaker contacts.

A New Measurement Method of the Dynamic Contact Resistance of HV Circuit Breakers

The proposed paper will present a new dynamic contact-resistance measurement method that has been validated by field tests which were performed on air-blast and SF6 gas circuit breakers. The unique measurement method allows reproducible resistance curves to be obtained, which is not the case with the conventional method. Dynamic contact resistance curves obtained by using both the conventional technique and the new method are compared. By applying the novel measuring method, the dynamic contact resistance curve is easy to interpret. It is believed that the new measuring method can be used as a diagnostic tool for SF6 gas circuit breakers whenever contact anomalies are suspected. This new measurement method allows for an accurate evaluation of both main- and arcing-contact conditions without dismantling the circuit breaker. Moreover, it provides the maintenance crew with relevant criteria for selecting the interrupting chambers that should be internally inspected.

Comparing direct and synthetic tests for interruption of line-charging capacitive current

Using a validated arc model, this paper analyzes current distortion and voltage waveforms during both direct and synthetic tests for interruption of line-charging capacitive current by power circuit breakers. Although the voltage of the electric arc drawn between breaker contacts may produce significant current distortion, it is demonstrated that the most significant parameter affecting the breaking capacity of power circuit breakers in capacitive-current switching tests is the voltage jump appearing across breaker contacts immediately after current interruption. It is essential to correctly define the supply circuit impedances and the associated voltage jump so as not to reduce or increase this test severity unduly.

Comparison of waveshape quality of artificial lines used for short-line fault breaking tests on HV circuit breakers

The authors present a comparison of the waveshape quality of six different artificial-line circuits used to produce the high rate-of-rise of recovery voltage specified by ANSI and IEC standards. For a purely capacitive and inductive pi-section circuit, it is shown that even eight pi sections do not meet the requirements. With the addition of a resistance in the first branch, this circuit design produces adequate solutions but requires a large number of components. The analysis reveals that the KEMA circuit easily meets the requirements for the rated peak factor of 1.6 but for the 1.8 peak factor a compensation would be required for the initial part of the wave. The simplest circuit comprising only three (RLC) components meets the specifications with a high voltage-peak overstress factor of 1.3. >

Hydro-Quebec's concerns related to performances of SF/sub 6/ circuit-breakers

Hydro-Quebecs concerns regarding circuit breaker reliability are presented. Emphasis is placed on two aspects crucial in determining line charging current breaking capacity, i.e., the arc duration and the test circuit configuration. The importance of manufacturing quality for the arcing contacts, nozzles and gasket is discussed. Test criteria at 20 degrees C for simulating breaking tests at -50 degrees C are given. Hydro-Quebecs requirements for testing the tightness of SF/sub 6/ breakers are presented together with a reliable leakage-measuring method. >

Comparative Performance of Paraffinic and Naphthenic Insulating Oils Under ARC-Quenching Conditions

An investigation into the arc-quenching characteristics of two experimental paraffinic oils made from western Canadian crudes was performed in Conparison with Voltesso 35. The approach chosen was to subject low-voltage circuit breakers to both resistive and short-circuit arcing conditions. The arc-interruption performance of the two experimental oils was equivalent to Voltesso 35. Gas formation was also similar in composition and rate.