This paper aims to characterize accurately each incident main cause, to analyse their occurrence with the intrinsic characteristics of the Portuguese territory, including geographical and meteorological data, and to define the requirements and guidelines to use this information as input for a risk assessment methodology, whose main purpose is to support control room operators in their continuous task.
Transmission system operators have to consider multiple contingencies in the security analysis whenever lightning or active forest fires exist or are expected, in order to be prepared and prevent harmful situations. This paper presents a method to integrate multiple contingencies in the security analysis.
The objective of this paper is to describe a process which was developed in the Portuguese TSO (REN -Rede Eléctrica Nacional, SA) whose main purpose is to identify voltage collapse situations without the need for the specific EMS module. The process is based on the Power Flow Module of PSS/E software from Siemens Power Transmission Distribution, Inc., running automatically through an application developed in Python, which performs a SV analysis. Its results are available via browser from control room PC's and are updated every 30 minutes, allowing to monitor the system security levels and to take suitable remedial actions to prevent a voltage collapse situation. The need to develop a process to identify voltage collapse situations in the Portuguese Transmission System arose with voltage problems identified in a specific substation when performing N-1 Contingency Analysis. The operator training simulator, an important tool to analyse and understand the power system behaviour, was also used to study and demonstrate the voltage collapse phenomenon.
Nowadays when utilities are faced with increasing requirements regarding Quality of Service, it is important to be aware that severe contingencies can happen, in an unpredictable way which far exceeds all the security principles used for planning and system operation. In any electricity transmission system, a security condition must be assuredeither in steady or in transient state -otherwise the essential service provided to costumers could be severely jeopardized. Present day Quality of Service requirements that are imposed on the electrical utility companies force them to develop efficient processes to analyze and react to incidents that can happen in an unpredictable way and far exceed all the security principles used. The simulation and analysis of these scenarios allow us to minimize the risk of system unbalance and voltage collapse. The steady state simulations of the Portuguese Transmission System were made in PSS/E software from Siemens Power Transmission Distribution, Inc., using savecases that represent pictures of the real system. The simulation results presented focus on aspects like energy not supplied, generation lost and topological changes resulting from an incident, which will affect mainly the power flow distribution within the grid elements that will remain in service (connected) and the voltage level in the system bus-bars. These results allow us to be better prepared to face these severe disturbances, defining procedures for emergency situation and training the control room operators.
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