Access to EMTP user presentations, webinars, and slide deck presentations.
30 presentations for Overvoltage:
Author(s): Jin Yang - Ener-Phase Solutions
Type:Technical Presentation
Date: 2021-06-21
Abstract
A case study will be presented demonstrating modeling of overvoltage in a moderately sized system involving medium voltage vacuum breakers, cables and transformers. The focus is on simulating high fre... see morequency overvoltage generated by circuit breaker prestrikes and re-ignitions and evaluating the impacts on transformer insulation.
-Results obtained from a customized breaker TRV model which is capable of controlling the capability of switching high frequency current will be presented.
-The methodology of analyzing severity of overvoltage in the frequency domain was applied in this project. Results and discussions regarding frequency domain analysis will be shared.
-Simulation results regarding typical system configurations with variation of key parameters such as cable lengths, load power factors will be briefly presented.
-Application of EMTP study results in assisting equipment specification, as well as overvoltage mitigation methods including optimizing switching sequences, necessity of snubber circuits will be discussed.
-Case specific strategies to improve simulation speed and work flow with EMTP will be introduced and discussed.
Author(s): Sofía Aparicio, Andrea Pizzini, Nicolás Morales - UTE
Type:Technical Presentation
Date: 2021-06-21
Abstract
In order to obtain the distances required to perform live working maintenance on the Uruguayan transmission network under secure conditions, electromagnetic transient (EMT) studies are conducted to ob... see moretain the maximum switching overvoltage that can be found in 500-150 kV transmission network. Two different approaches were considered for these studies. On one hand, a simple approach is used, analyzing line switching transients on simplified two line network models. On the other hand, a detailed approach is considered, analyzing line switching overvoltage transients on a complete network model.
This complete model considers 500 kV and 150 kV overhead lines, 500/150 kV transformers, cables, reactive power shunt compensation, hydraulic and thermal generators. Electromagnetic transient studies and the complete network model are performed in EMTP software. Finally, a comparison between the results obtained considering each approach is performed.
Author(s): Angelica Rocha & Gustavo Oliveirra - ATG Engenharia & Federal Univ. of Parana
Type:Technical Presentation
Date: 2021-06-21
Abstract
The presentation will discuss the analysis of successive dielectric failures of inductive voltage transformers (VT) at a 500 kV GIS of Jirau hydroelectric plant in Brazil. All the failures involved th... see moree same region of the high voltage winding and the cause was undetermined. These incidents motivated a series of actions to identify the cause and improve the reliability of these equipment in the field.
One possibility the effect of very fast transients (VFTO) expected to occur during frequent switchings of disconnector and/or circuit-breaker at GIS. It well known that VFTO may stress inductive equipment insulation leading to a dielectric failure.
In this context, different switching conditions were simulated with the EMTP to determine the transient overvoltage at the potential transformer terminals. A special high frequency model of the VT was developed based on its frequency admittance matrix measured in the field. The result of the simulations was discussed together with the VT manufacturer and a final diagnosis of the failures was achieved.
Author(s): N.K.Nathan - KNR Engineers
Type:Technical Presentation
Downloaded: 11
Date: 2021-06-17
Abstract
Gas Insulated Substations provide cost effective solution due to reduced land requirements particularly in metropolitan area where power demand is registering steep growth. With the use of GIS technol... see moreogy, it is required to assess the risk of failure due to overvoltage. The Insulation Coordination study forms a very important aspect in design stage. This presentation deals with the IC study carried out for a large – 765/400/220kV GIS substation in a SUPER THERMAL POWER STATION in UTTAR PRADESH.
Due to the decreasing ratio of lightning impulse withstand voltage to the system voltage, the difference between LIOV and VFTO decreases and this factor calls for VFTO performance analysis for 765kV GIS as well.
The discussion includes modeling of Extra High Voltage GIS, Temporary Overvoltage (TOV), Lightning Impulse Overvoltage (LIOV), Switching Overvoltage (SOV) and Very fast transient Overvoltage (VFTO) performance analysis on 765kV GIS substation.
TOV typically caused by fault to ground, load rejections and energization of long lines are analyzed to decide the rating of the surge arrester.
LIOV simulation studies are carried out for possible onerous paths including longer and short paths to decide the location of the arrester. SOV analysis deals with the overvoltage due to switching operations during line energization, re-energization and fault occurrence and clearance.
The LIOV and SOV results have been validated with reference to protective levels prescribed. The VFTO analysis is performed with various GIS disconnector operations in accordance with the methodology and guidelines as per CIGRE WG D1.03-TB 519 and the results are validated with the limits specified.
Keywords: Insulation Coordination, VFTO, EHV, GIS, 765kV, Protective ratio.
Author(s): Diego F. Rodríguez - GERS
Type:Technical Presentation
Date: 2021-06-17
Abstract
Temporary overvoltages (TOV) are oscillatory overvoltages mainly caused by switching or faults, which are of relatively long duration and undamped or slightly damped. Maximum overvoltages under faulte... see mored conditions can require considerable energy magnitudes absorbed by surge arresters.
These energies may overpass maximum limits and lead to equipment damage.
This project presented a study to identify the maximum TOV at the MV equipment of a PV power plant during fault-clearing events. Two methods of TOV suppression are evaluated, including grounding transformers and fast grounding switches under two different configuraions. An electrical model was elaborated in EMTP to perform the simulation of the transient overvoltage due to the un-balanced fault clearance, considering each inverter of the PV plant. The results show that considering no grounding technologies at the feeders, the energy absorption limit is overpassed in the islanded system.
Therefore, a fast grounding switch or a system with grounding technology at each feeder is needed in order to protect the substation equipment.
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