The implementation of distributed generation sources with islanding microgrid capabilities can introduce new challenges for engineers integrating new large generators to existing power systems. The generator interconnection transformer winding configuration and the generator winding pitch greatly impacts the flow of circulating currents and can result in unexpected generator heating, as well as high grounding resistor operating temperatures. This presentation presents a case study of the flow of 3rd order harmonic currents in a microgrid power system, and how EMTP was used to design equipment modifications necessary to reduce the current. A review of generators and how they can lead to 3rd order harmonic current generatio, along with additional options for correcting this condition will be presented.

Faults within a transmission system can greatly impact the capability for power transfer. Isolating a fault by removing the line from service can further diminish the power transfer capacity, compromising the system`s stability margin. Single-phase-to-ground faults, which are the most frequent, can be effectively isolated by taking only the affected phase out of service, while keeping the remaining two phases active. This approach, referred to as single-pole switching (SPS), permits the line to carry two-thirds of its power and preserve synchronization between the sources at both ends of the line, However, it presents distinct challenges. In a long line, a small AC current can still sustain even after the breakers open. This current is called the secondary arc current and it is due to electromagnetic coupling between the phase conductors. If the breaker pole is reclosed before this current extinguishes, the fault will reoccur, leading to unsuccessful reclosure. The aim of this work is to identify the key factors that significantly influence the secondary arc current and to evaluate different methods to reduce its amplitude. For successful reclosure, the circuit breaker`s dead time must be longer than the secondary arc`s extinction time. This study models the secondary arc using the EMTP program to simulate its interaction with the transmission system and estimate the necessary dead time for the circuit breaker. The study analyzes the self-extinguishment of the secondary arc by monitoring its magnitude and the recovery voltage using EMTP. It concludes with recommendations for reducing the secondary arc current and determining the minimum dead time required for the successful reclosure of a 380KV transmission line.

Since 2022, the National Electric Coordinator in Chile has requested standardization of the dynamic models of the power plants or parks connected to the National Electrical System (SEN). As a company (EEMT), we have participated in the development of dynamic models for various wind and photovoltaic parks, carrying out a series of EMT homologations, both for equivalent and complete models. This involves analyzing their operation and validating them through records. Once this process is completed, it is possible to conduct tests and systemic verifications on the model, performing different short circuits and analyzing the LVRT. Thanks to the development and homologations of these models, in their complete and equivalent stages, different analyses can be carried out where electromagnetic phenomena exist for complete models, while with the equivalent models analyses can be carried out in a delimited area, generating faults and comparing them with real cases that have occurred. Within the framework of this conference, EEMT wants to present what the development of the homologation of these models has meant, the results that have been obtained in their different stages, and the usage that can be given to them for the performance of different analyses. On the other hand, as a consulting firm, we have been developing our own model of the Chilean National Electrical System based on various studies and based on the experience we have acquired as a leading consulting in EMT models. With the progress of homologations and the development of EMT models, it is expected that in the future there will be a systemic Database of the SEN that contains a greater number of aggregated models and that reliably allows for a large scale systemic analysis, such as, failures in the 500 kV transmission line, among other phenomena.

In this hydroelectric generation project, connection is established in a 500 kV system, which includes series compensation. A comprehensive TRV analysis was conducted to evaluate the existing circuit breakers. Based on this analysis, it was determined that implementing opening resistors is necessary to mitigate the adverse effects of TRV and ensure compliance with Peruvian electrical regulations.

This presentation will focus on a specific issue of bipolar HVDC lines with a dedicated metallic return (DMR). DMR is insulated to a lower level than the pole and its insulators are shorter. One event, for example, pole-to-ground-fault will cause a fault on both the pole insulation and the DMR insulation simultaneously because the DMR insulation fault will be supported by the DC current and will turn into a DC arc. To ensure independent pole operation, these types of events should be avoided or, if the DMR does flashover, to extinguish the fault as soon as possible. This is phenomena are presented and how different solutions are tested with EMTP software to protect the DMR.