Technical Presentations

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

Single Pole Auto Reclosure and NGR Analysis 794

Abstract
Unsuccessful auto reclosure has been observed in 765 kV HVAC transmission lines connected with Generation Bus. Back up Impedance Protection of Line reactor triggered during AR dead time due to power f... see morerequency oscillations in faulty phase (disconnected phase). It triggered tripping of Non Switchable Line Reactor at one end, which resulted tripping of 765 kV HVAC Line and avoidable Generation loss.

These Unsuccessful AR operations triggered us to study and model entire phenomena in Power System Analysis software (EMTP).


Initially, two circuits of 765 kV Transmission Line commissioned between Generation Station and Transmission Station with Line Reactor and NGR in both line at either end. Successful auto reclosure observed during single-phase faults on these lines. Intermediate Switching station constructed and both lines were divided in 4 section as per new requirement. Same configuration (rating) of Line Reactor and NGR adopted at newly constructed station on each line. Unsuccessful AR observed during AR running cycle on these lines after new configuration. Backup Impedance protection of Line Reactor found operated during AR Dead time.
Different sets of simulations has been carried out to understand the phenomena:

- Single Phase fault and Auto reclosure in 765 kV Transmission line in different section of entire corridor with Varying Shunt compensation (Value of Line Reactor)
- Different NGR values and observations for above simulations
- Trip the Line Reactor Breaker during Auto Reclosure Phenomena to avoid operation of Backup Impedance protection and its consequences

After EMTP Simulations and study, it was concluded that:

- Line Reactor (Degree of compensation) should be adjusted with adequate value while line length altered from its original design.
- NGR re-sizing can address the issues at some extent. Suitable value of NGR (based on Line Length and amount of shunt compensation) should be employed
Appropriate Solution and mitigation suggested after detail simulation & study.

Tag(s): single pole, analysis, auto reclosure, line reactor

POWERGRID experience with EMTP793

Abstract
To meet the increasing power demand, a number of extra high voltage (EHV) transmission lines is being added to the power system network, which enhances the complexity of power system network. It is es... see moresential duty of power engineer to fulfill the growing demand ensuring the reliability, stability & security of GRID. Transient simulation tools like EMTP play a vital role to provide the flexibility to power engineer for simulating/studying the various case scenarios which couldn’t be simulate in physical power system.


Such tools eventually help power engineer to build a sustainable and secure GRID. In POWERGRID, being a central transmission utility, various studies are being carried out to arrive the technical particular of new transmission system and optimize or fine tuning of existing system. Some of them i.e. Transient Recovery Voltage (TRV) study of 1200kV Transmission network, Smart Power from insulated earth wire of EHV transmission line and 1200kV Transformer Inrush current study are discussed in presentation. 1200kV National Test Station was established & successfully charged along with the transmission line in state of BINA in India.


TRV study was carried out for assessment of various test duties of 1200kV Circuit Breaker. Presentation cover the detailed discussion of 1200kV TRV study and a brief about the facilities like HIL, HVDC control Replica setup, STATCOM replica setup available at Powergrid Advanced Research and Technology Centre (PARTeC).

Composite testing of HVDC-connected offshore wind farms in Great Britain778

Abstract
Transmission connections to offshore wind generation typically consist of multiple technologies supplied by different manufacturers with each tested at the factory, but with limited composite modellin... see moreg and testing of the combined system control and protection performance.

To start to address these technical challenges, the HVDC Centre with the support of ESO connections team commissioned the COMPOSITE project with RTE International to identify practical guidelines and best practices for composite testing and compliance of complex electricity connections, leveraging the experience we share across multi-vendor and multi-device testing we have delivered.

This joint webcast by HVDC Centre in collaboration with RTE International and EMTP® will describe key findings and lessons learned from the COMPOSITE project, including a demonstration of EMTP® modelling the composite models and their test cases.

Speakers:
- Benjamin Marshall – HVDC Technology Manager
- Dr. Oluwole Daniel Adeuyi - Simulation Engineer & Offshore Networks Lead
- Hani Saad - Power system expert engineer

A new resource is available to explain step-by-step how to create a DLL in EMTP.776

Abstract
A new step-by-step resource is available to explain how to create a DLL in EMTP®.

The DLL (Dynamic Link Library) function is designed to allow EMTP® users to develop advanced program mode... see morel modules and interface them directly and intimately with the EMTP® engine. It is for advanced users and offers advanced capabilities.

Users interested in programming language-based model development should use this feature to develop and maintain models. Such models can be placed in a specified location, attached to a device with graphical user interface features in EMTPWorks and maintained in a library just as any other built-in EMTP model.

This option may be used by converter manufacturers to interface real code into EMTP®, to perform Software In the Loop.

For this purpose, EMTP® is also compatible with the Joint IEEE TASS Task Force and CIGRE B4.82 Working Group “USE OF REAL-CODE IN EMT MODELS FOR POWER SYSTEM ANALYSIS”.