Reliability and computational simplicity are of primary importance in developing on-line instability detection methods. With regard to these requirements, this paper has proposed a new method for instability detection based on generator angles, angular velocities, and their rates of change. According to the developed method, system instability or out-of-step condition is detected by identifying the characteristics-concave or convex-of a surface on which the post-fault system trajectory lies. The variation mode and probabilistic property of the proposed index are investigated by using the 10 machine 39 bus IEEE test system.

A new method for power system transient instability detection

When interconnected power system out of step occurs, it is imperative to detect it rapidly, and islanding should be taken to prevent widespread blackout. This paper presents a review of the main aspects on power system islanding. Out of step detection methods are classified to six categories. Islanding schemes are outlined according to graph partitioning, minimal cutset enumeration and generator grouping. In addition, four types of load shedding schemes after islanding operation are discussed. Synchronized phasor measurements and AI technologies facilitates the out of step detection, and makes the adaptive islanding and load shedding scheme

Aspects on Power System Islanding for Preventing Widespread Blackout

Out-of-step protection of generator using analysis of angular velocity and acceleration data measured from magnetic flux

Pole slipping of synchronous generators operating in parallel with a utility supply system is a complex phenomenon. This paper provides an overview of a new solution for pole slipping protection, together with a review of conventional techniques. Immediate advantages of the new approach are that it simplifies relay settings and avoids the need for extensive simulation studies. Results from simulation studies and field tests are used to demonstrate the performance of these systems. The new technique is shown to offer a significant improvement in performance over conventional schemes.

A study into a new solution for the problems experienced with pole slipping protection [of synchronous generators]

This paper describes the development and implementation of an acceleration trend relay (ATR) which is in operation for generator stabilization at Colstrip, Montana. The ATR is unique in that it uses only local signals at the remote generation site to selectively trip generating units based on a real-time assessment of the severity of a disturbance. Local inputs to the ATR are generator shaft speed from magnetic pickups and generator electric power from a watt/VAr transducer. Based on these inputs the appropriate amount of generation to trip is determined in order to maintain stability of the remaining system. Details on how the device works, how trip decisions are arrived at, and operating experience with the device are presented.

The acceleration trend relay for generator stabilization at Colstrip

The purpose of the equipment described is to separate the power system when an out-of-step between two groups of generators within it is predicted. The out-of-step prediction method is based on the generator's angular-velocity data measured by electromagnetic sensors and gears that are fastened directly to the rotors. The equipment was tested by the large-scale power system simulator APSA (Advanced Power System Analyzer) and was also field tested. The results are presented. >

K. Sawai

Papers

System separation equipment to minimize power system instability using generator's angular-velocity measurements