Technical Presentations

Implications of faults on insulation coordination of dedicated metallic return on bipolar HVDC overhead transmission lines887

Abstract
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... see more, 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.

Tag(s): HVDC, Insulation Coordination, Faults

Insulation coordination study of 220 kV transmission line for reliability improvement against lightning-induced overvoltages877

Abstract
This presentation shows a detailed insulation coordination verification using EMTP. It includes an accurate representation of transmission line components considering actual site data such as conducto... see morer arrangement, line length, line parameters, insulator details, tower structure and location, tower grounding resistance, and lightning data.

Tag(s): Insulation Coordination, Lightning Strike, LIOV, Line Surge Arresters, Back-Flashover

Insulation Coordination Study of 765kV GIS SUBSTATION788

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.

Wind & Solar Generation Impact on Negative Sequence & Power Swing Protection759

Abstract
<p>This presentation investigates the impact of wind generation on the performance of negative-sequence-based protection.</p><p>
Overview: - Main differe... see morence between EMT-type and phasor domain software. - Load-flow simulations - Time-domain simulations - Frequency Scan - Statistical runs for Insulation Coordination studies - Switching - Lightning - Transient Recovery Voltage (TRV) - Ferroresonance - FACTS/HVDC - Transient stability - Renewable - Power quality - LVTR/OVRT - Sub-synchronous resonance (SSR) - Overcurrent protection - Differential protection - Distance protection - Power-swing and out-of-step detection - Loss of field protection - Open-phase</p>

Modeling of Transmission Line and Substation for Insulation Coordination Studies546

Abstract