An integrated autonomous protection system against voltage instability based on Load Tap Changers

Abstract

In this paper we propose a local, completely autonomous protection system against voltage instability that can be readily integrated in the controller of each bulk power delivery LTC transformer. The protection system will identify an imminent voltage instability and will subsequently apply the necessary corrective measures to restore stable operation by properly adjusting the distribution voltage setpoint of the LTC. Application of this system on a 52-bus test system showed excellent performance for two unstable cases. For reasons of comparison, the indirect load curtailment proposed in a severe instability case is compared with direct load shedding schemes based on the local detection of instability, as well as on a global detection of instability assuming wide area measurements.

A short survey of methods for voltage instability detection

“…A different voltage monitoring method was introduced in [26], further tested in [27] and extended in [28]. The method monitors the distribution voltages controlled by Load Tap Changers (LTCs) on bulk power delivery transformers.…”

Overview of local identification of emergency and protection against voltage collapse

“…In Case 2 loads in the base case are reduced, so that the system is marginally unstable after the same disturbance. System data are as in [1].…”

“…In this paper we review an integrated protection scheme, proposed in [1], which is based in the LIVES method (Local Identification of Voltage Emergency Situations) presented in [2][3][4][5]. The method is based on monitoring the secondary (and eventually the primary) voltages of Load Tap Changers (LTC) of bulk power delivery transformers.…”

“…The method is based on monitoring the secondary (and eventually the primary) voltages of Load Tap Changers (LTC) of bulk power delivery transformers. The protection system is composed of three separate modules, running simultaneously at each LTC controller, dealing with different implementation aspects encountered in [1][2][3][4][5]. The first module is called LIVESalarm, and is responsible for detecting an imminent voltage instability by monitoring the secondary voltages after each LTC movement.…”

Voltage stability monitoring and control studies in the Hellenic interconnected system

“…We investigate also the impact of dispersed and concentrated static compensation, located in wind farm (WF) connection substations and a central power plant respectively, on the loadability limit of the system. Finally, we review some preliminary results of the operation of an autonomous protection system against voltage instability [5], [6] based on Local Identification of Voltage Emergency Situations (LIVES) [7], [8].…”