Discussion on hidden failures in relay protection of power systems;

This research defined hidden failures of protection schemes and showed that these kinds of failures have contributed in the degradation of 70-80 percent of the wide-area disturbances.

This paper defines the regions of vulnerability of hidden failures by analyzing the action mechanism of the hidden failures in protection equipment.

To find out effective measures to reduce the risk of cascading failures in power grids,by means of IEEE RTS 96 system a cascading failures searching model is used to analyze the impacts of the faulty probability of key lines,probability of hidden failures and transmission limits of key lines as well as adopting new control measures on risk index of cascading failure.

Protection system hidden failures is one of the main causes of large-scale blackouts, which inevitably will lead to disastrous consequences of power grids from cascading failures.

In order to avoid relay settings from being a hidden failure source,an idea of relay settings examination and rectification is proposed and a software for relay settings examination and rectification is developed.

Analytic method for relay protection importance with consideration of hidden failures;

The basic process and theory of power system cascading failure considering protection system hidden failures were analyzed to decrease bulk blackout failure.

For the purpose of investigating how the failures spread in the power grids, finding out the key-lines affecting the cascading failures, this paper presents an approach to calculate the risk of line outage and identify key-lines causing blackouts based on the hidden failure model and risk theory.

The hidden failure,power system vulnerability and adaptive control regarding.

Hidden failures in protection system are great threats to the operation of power grids,while there are almost no on-line diagnostic methods for hidden failures so far.