Martin T. Bishop

Development and Testing of an Electro-Mechanical Relay to Detect Fallen Distribution Conductors

If undetected by phase or ground overcurrent relaying methods, fallen distribution conductors or high impedance faults may be a fire hazard and a threat to public safety. Four promising relay schemes to detect these faults are evaluated using both digital and analog techniques and one scheme was chosen for prototype construction. In the light of economic and performance data, a prototype Ratio Ground Relay has been constructed for installation and testing on six Pennsylvania Power and Light distribution feeders.

Performance Testing of the Ratio Ground Relay on a Four-Wire Distribution Feeder

Digital fault investigations on six Pennsylvania Power and Light 12 kV distribution feeders led to the development of a prototype Ratio Ground Relay to theoretically provide better detection of broken conductor faults. Further assessment of the relays performance was provided through analog computer tests followed by staged fault testing on an operating distribution feeder. Performance tests are described and documented. These positive test results provided the incentive to monitor the performance of the Ratio Ground Relay on several PP&L distribution feeders.

A Comparison of Measured High Impedance Fault Data to Digital Computer Modeling Results

Staged fault tests were-cohducted by Pennsylvania Power and Light Company to verify the performance of the Ratio Ground Relay concept. Previous development and tasting efforts, regarding this relay have been reported (1, 2). This paper presents the field measured fault current data in entirety and compares the field. data with SCADA collected data and digital computer data. The paper documents that a 12-kV four-wire multi-grounded neutral distribution feeder can be accurately modeled on a. digital computer, and that the computer results are field verifiable. The favorable results of this comparison provide confidence in the modeling method for use in development, testing, and application of new relay methods.

Distribution System Line Loss Reduction through Enhanced Capacitor Location Techniques

Many approaches can be taken when evaluating the replacement of PCB-filled capacitors on overhead distribution feeders. Pennsylvania Power and Light Company utilized the opportunity to reevaluate capacitor application techniques as well as capacitor placement. This paper summarizes a joint PP&L/Westinghouse effort to determine the value of a complete capacitor engineering evaluation as compared with a strict one-for-one unit replacement. Examination of seven feeders yielded significant reduction in real line losses, formulating the justification for future capacitor application efforts.

Innovative Differential Protection of Power Transformers Using Low Energy Current Sensors

Traditional differential protection systems are applied on large power transformers using current transformers (CTs). However, because of high secondary currents (often exceeding 100 kARMS), differential protection systems for electric arc furnace transformers have not been applied in the past due to the lack of commercially available CTs. This paper will present differential protection systems that have been in use for many years using Rogowski coil current sensors. These protection systems use high-precision printed circuit board Rogowski coil current sensors. This paper reviews the characteristics, designs, and application of these Rogowski coil sensors for advanced protection, control, and metering systems with new multifunction relays. This paper compares performance characteristics of new solutions based on Rogowski coil sensors with the conventional differential protection systems based on CTs, demonstrating that the new systems do not have the limitations of conventional technology. Operating experience from several site applications is included.

Innovative Differential Protection of Power Transformers Using Low-Energy Current Sensors

Traditional differential protection systems are applied on large power transformers using current transformers (CTs). However, because of high secondary currents (often exceeding 100 kARMS), differential protection systems for electric arc furnace transformers have not been applied in the past due to the lack of commercially available CTs. This paper will present differential protection systems that have been in use for many years using Rogowski coil current sensors. These protection systems use high-precision printed circuit board Rogowski coil current sensors. This paper reviews the characteristics, designs, and application of these Rogowski coil sensors for advanced protection, control, and metering systems with new multifunction relays. This paper compares performance characteristics of new solutions based on Rogowski coil sensors with the conventional differential protection systems based on CTs, demonstrating that the new systems do not have the limitations of conventional technology. Operating experience from several site applications is included.

Comparative characteristics of iron-core current transformers and Rogowski Coils for applications for protective relaying purposes

This paper compares the operating characteristics of non-conventional current sensors, Rogowski Coils, and conventional iron-core current transformers for protective relaying applications.

Coiled for protection

In this article, the authors describe an advanced protection system that incorporates Rogowski coil current sensors and multifunction relays that provide primary and backup power system protection.

Analysis of Time Varying Distribution Circuit Current and Loss Characteristics

Increased capital and generation costs coupled with the expense of losses are providing motivation to distribution engineers to improve their knowledge of the distribution system and apply that knowledge to improve its operation. Balancing of distribution circuit loads is an economic loss reduction technique to improve distribution system efficiency which is inexpensive and can be quickly accomplished. This paper demonstrates a relatively simple way to analyze potential distribution loss reductions and provides documentation, through presentation of system data, that verifies the validity of this approach.