Technical Presentations

Ferroresonance Phenomena for Voltage Transformer failure – Simulation & Analysis using EMTP and Mitigation Technique874

Abstract
Ferroresonance is an oscillating phenomenon between a non-linear inductance and a capacitor that can results in highly distorted over voltages and overcurrent. Ferroresonance phenomenon occurs when a ... see moreferromagnetic core inside an electrical device – primarily a voltage transformer or an unloaded power transformer – operates in the saturated condition, under which inductance has become a non-linear element. In practice, ferro resonance can be triggered even by a temporary introduction of core into saturation, e.g. resulting from switching operations or a change in voltage resulting from an earth fault.

Tag(s): Ferroresonance, Transformers, Low-Frequency Transients, Overvoltage, Non-Linear Element

Measurement and EMTP Simulation of Ferroresonance Phenomenon849

Abstract
Ferroresonance is difficult to predict because its occurrence in the power system depends on several parameters, some of which are unknown (parasitic capacities). In addition, measuring electrical con... see moreditions during high voltage ferroresonance is very difficult to achieve. In order to check the possibilities of numerical calculations of ferroresonance, the ferroresonant circuit was made as a low voltage circuit in which all parameters were known.

Measurement of ferroresonant current and voltages in a single-phase low voltage circuit will be described. The system consists of an AC voltage source, a capacitor, a switch and the single-phase transformer. These electrical elements are connected in series. The magnetic flux-current points of the magnetization curve of the transformer was experimentally obtained and used in the simulation. When the switch closes, ferroresonance takes place since all conditions were met for its occurrence. The waveforms of the transformer current and the voltage at the transformer terminals were measured after switch closing.

During the ferroresonance, transformer voltage and current reach relatively high values. At the beginning of the ferroresonance (during its transient part), the voltage of the transformer reaches values that are about two times higher in amplitude than the amplitude of the AC source. The primary side of the transformer was modelled with a series connection of the ohmic resistance and leakage inductance. The core was modelled with a parallel connection of the ohmic resistance and nonlinear inductance. The ohmic resistance represents the core losses while the nonlinear inductance models the magnetizing characteristic of the transformer.

A comparison between simulated and experimentally obtained results shows that EMTP successfully simulates the ferroresonance phenomenon for this specific electrical system as simulated results are in a good agreement with the measured results.

Tag(s): ferroresonance, tov, saturation

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

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>