8

Transmission System Operation

8.1 Introduction

Transmission systems in many countries are facing ever more demanding operating conditions with increasing penetrations of renewable energy generation, larger flows and greater cross-border trading of electricity. The variability of the power output of renewable energy sources and unplanned flows through transmission grids are causing difficulties for the system operators, who are responsible for maintaining the stability of the system. Excessive power flows in transmission circuits and large variations in busbar voltages may arise during steady-state operation so that when faults and network outages occur, they can lead to system collapse.

In order to aid the transmission system operators to monitor, control, and optimise the performance of generation and transmission systems, a suite of Applications collected into an Energy Management System (EMS) is used. As the monitoring and control functions for EMS are often provided by SCADA, these systems are also referred to as EMS/SCADA. The EMS is normally located in the System Control Centre and effective real-time monitoring and remote control exist between the Control Centre and the generating stations and transmission substations.

With the growing availability of measurements from Phasor Measurement Units (PMUs), it is expected that, in future, PMU measurements will be integrated with EMS. However, at present, PMUs are mainly incorporated into separate Wide Area Applications. It is ...

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