Identification of Critical Hidden Failure Line Based on State-failure-network

The hidden failures generally exist in power systems and could give rise to cascading failures.Identification of hidden failures is challenging due to very low occurrence probabilities.This paper proposes a state-failure-network(SF-network)method to overcome the difficulty.The SF-network is formed by searching the failures and states guided by risk estimation indices,in which only the failures and states contributing to the blackout risks are searched and duplicated searches are avoided.Therefore,sufficient hidden failures can be obtained with acceptable computations.Based on the state and failure value calculations in the SF-network,the hidden failure critical component indices can be obtained to quantify the criticalities of the lines.The proposed SF-network method is superior to common sampling based methods in risk estimation accuracy.Besides,the state and failure value calculations in the SF-network used to re-estimate the risks after deployment of measures against hidden failures need shorter time in comparison with other risk re-estimation methods.The IEEE 14-bus and 118-bus systems are used to validate the method.

Improving the performance of power system protection using wide area monitoring systems

Wide area monitoring(WAM) offers many opportunities to improve the performance of power system protection. This paper presents some of these opportunities and the motivation for their development. This methods include monitoring the suitability of relay characteristics,supervisory control of backup protection, more adaptive and intelligent system protection and the creation of novel system integrity protection scheme. The speed of response required for primary protection means that the role WAM in enhancing protection is limited to backup and system protection. The opportunities offered by WAM for enhancing protection are attractive because of the emerging challenges faced by the modern power system protection. The increasingly variable operating conditions of power systems are making it ever more difficult to select relay characteristics that will be a suitable compromise for all loading conditions and contingencies. The maloperation of relays has contributed to the inception and evolution of 70 % of blackouts,thus the supervision of the backup protection may prove a valuable tool for preventing or limiting the scale of blackouts. The increasing interconnection and complexity of modern power systems has made them more vulnerable to wide area disturbances and this has contributed to several recent blackouts. The proper management of these wide area disturbances is beyond the scope of most of the existing protection and new, adaptive system integrity protection schemes are needed to protect power system security.