Technical Presentations

Dynamic Overvoltage Conditions Experienced at a PV Solar Power Plant838

Abstract
We present the results from an investigation of the cause of dynamic overvoltage conditions experienced at a solar power plant, that resulted from energizing the PV solar plant 34.5 kV collection syst... see moreem feeders using a back-up diesel generator. The diesel generator unit was installed at the solar plant for emergency back-up power to the project, in case of power outage from the connecting transmission utility system.
The back-up power source was provided to allow the operation of the solar power tracking system during emergency conditions. A subsequent study was performed using EMTP software program, to investigate the cause of these dynamic overvoltage conditions at the solar power plant. A detailed transient model of the solar plant and the diesel generator were developed using EMTP.


The EMTP simulations were useful in replicating the overvoltage event measurement recordings from the site, and the simulation results from the study, concluded that the diesel generator did not have sufficient capability to pick up capacitive loads and therefore, the unit was unable to control the overvoltage conditions which led to the overvoltage event that caused equipment damage to the PV inverters and their auxiliary systems. The study evaluated various solution alternatives and mitigation strategies to reduce these dynamic overvoltages to acceptable conditions.

Tag(s): pv park, tov, diesel generator, temporary overvoltage

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.

Transient immunity assessment of wind and solar parks773

Abstract
Abstract
Inverter-base Resources (IBRs), such as solar photovoltaic (PV) and wind parks are subject to transients which may cause more issues as compare to traditional generation due to the colle... see morector grid and the geographical spread between converters. In this webinar, we present several challenges which may be faced by planners and park developers:
- Transient immunity against utility-owned capacitor bank switching. Assessment of IEEE Std 1547-2018.
- Ferroresonance after open-phase faults.
- Temporary overvoltage (TOV) in a PV parks after a phase-to-ground fault
Events and EMTP simulations will be described and analysed during the webinar.
This work was performed with the collaboration of Bob Arritt, EPRI and Chest Li, Hydro One

Presenters:
• Hossein Ashourian - Power System Modeling and Simulation Specialist

• Anton Stepanov - Research And Development Specialist