The author presents a bibliography and survey of the literature concerned with theory and measurement of the stochastic behavior of pulsating partial-discharge (PD) phenomena that can occur when insulation is subjected to electrical stress. The types of PD phenomena considered include AC and DC generated electron avalanches, pulsating positive and negative corona in gases, and PD that occur in liquid media and in the presence of solid dielectric surfaces. The basic physical mechanisms of discharge initiation, growth, and memory propagation that determine the probability distributions for pulse occurrence times and pulse amplitudes are discussed. Consideration is also given to special problems associated with the measurement and interpretation of data on the various statistical properties of PD phenomena. >

Stochastic properties of partial-discharge phenomena

Calculations have been done to evaluate the effects of the semiconducting screens, the conductors, and the surrounding earth on the propagation constants of electromagnetic waves in concentric underground power cables. The theory, based on Maxwell's field equations, is reviewed. Results of calculations of both speed and attenuation are presented for a variety of practical configurations. Limited comparisons with experimental results are included. In addition to their direct application, the results can be employed to calculate the cable characteristic impedance from an algebraic expression which is presented.

Wave Propagation Characteristics In Underground Power Cable

This paper describes an automatic fault location technique for permanent faults in underground LV distribution networks (ULVDNs). It uses signals from an existing time domain reflectometry (TDR) instrument. It pre-processes TDR signals to eliminate reflections due to single-phase tee-offs, and to locate 3-phase open or short circuit faults and also uses adaptive filtering to compare the TDR signals to locate faults. In essence, the procedure minimizes the interpretation skill required from a user of a typical TDR based fault location instrument. The relative performance of the system is demonstrated using real field data.

Automatic fault location for underground low voltage distribution networks

A cable fault detection component (168) receives input data indicative of a fault in an electrical power system. The component (168) analyzes the input data to determine if the fault is indicative of a self-clearing cable fault and generates corresponding output data (276). In one implementation, the cable fault detection component (168) is implemented as a software module which operates on a computer (105) of a substation intelligence system (104).

Cable fault detection

This paper deals with the subject of incipient faults in underground distribution systems and their progression over time leading to an eventual permanent failure. Field data recorded from an underground distribution feeder were analyzed in both time and frequency domain to identify the symptom parameters and characterize the observed incipient behavior. This exploratory data analysis sheds additional light on the progressive characteristics and nature of these self-clearing faults and advances the fundamental knowledge in an effort to detect such pre-mature failures before developing into a full-blown fault.

Field investigation and analysis of incipient faults leading to a catastrophic failure in an underground distribution feeder

The location and repair of faults in underground transmission lines is a difficult and time-consuming operation. The Department of Energy has sponsored research in the development of instrumentation to detect and locate incipient fault sites. Some of these methods rely on reflectometry techniques in either the time or frequency domain. NBS has investigated the feasibility of using such methods in extruded polyethylene cables.

John D. Ramboz

Papers

The Detection of Incipient Faults in Transmission Cables Using Time Domain Reflectometry Techniques: Technical Challenges