Technical Presentations

Simulation of Inductive EM Interference Caused by an HVDC Underground Cable Link on a Railway System853

Abstract
Scope of the presentation is to present results regarding inductive electromagnetic interference (EMI) between a real HVDC link and the nearby communication cables of a railway system under pole-to-gr... see moreound fault conditions.
?he HVDC and the railway system route in parallel at a part of the onshore section of the HVDC link. The inductive EMI on the communication cable arises from magnetic field variation of the high-frequency components contained in the transient response of the fault current, excited by the HVDC link.

Consequently, it is expected that no inductive EMI will occur by the DC current in the case of the HVDC system normal operation (steady-state) either in bipolar or monopolar (current return though the electrode) mode. The induced transient voltages and currents are calculated using the Electromagnetic Transients Program (EMTP).

Tag(s): emi, wb cable, hvdc, interference

Real Case of a Resonance in a Power Plant851

Abstract
Overvoltages were identified on the MV and LV networks of a Hydro Power Plant as the cause of the trip of the LV maximum voltage protection, compromising the normal operation of the system. Following ... see morethis event, measurements were conducted and the presence of a very high 23rd harmonic, potentially responsible for the various overvoltages, was identified associated to the operation of the Plant’s Synchronous Machine Frequency Control System (FCS). It was concluded then that this harmonic would have its origin in the FCS and would be amplified due to a possible resonance in the Power Plant internal network. A digital simulation study, using EMTP, was conducted to identify and characterize the resonance in the system and to propose mitigation solutions. The simulation models were developed using the equipment data and the system characteristics. The models were duly validated with measurements made both in time and frequency domains and it was possible to identify the origin of the overvoltages and their propagation in the system. It was concluded that the resonance occurred between a 30/11 kV Power Transformer and a 30 kV cable with 850 m.

This conclusion was supported by the results obtained in the measurements. Several alternatives were analyzed as mitigation solutions: - Installation of capacitors; - Different bonding techniques of the 30 kV cable sheaths; - Changing the 30 kV cable length; - Installation of a harmonic filter; The advantages and disadvantages of each solution were weighed also considering the ease of implementation, namely the available room. It was concluded that the installation of capacitors would be the best option. Measurements were conducted after the capacitor’s installation confirming the success of this solution.

Tag(s): harmonics, power uality, resonance

EMTP Development Roadmap: New Line/Cable data in EMTP 4.2829

Abstract
1. Brief review of transmission line equations

2. Per unit length parameter
- Traditional line data and cable data
- MoM-SO and Extended TL theory

3. New Line/Cable dat... see morea
- Mask options
- Application examples

Tag(s): EMT simulations, transmission, cable data,

Modeling and evaluation of overvoltage792

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.

Switching overvoltages studies for Live Working791

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.