Transient/intermittent faults

Transient/intermittent faults Transient faults occur once and then disappear. The majority of DCS or computer system faults (80—90% [4]) are the transient type, for example, a message is sent but does not reach the recipient, but when it is resent, it reaches the recipient. There is a peculiar characteristic of transient faults. This is termed intermittent fault, which occurs and vanishes in a cyclic manner. A simple loose connection in a component can cause such a situation. Transient and intermittent faults are mainly caused by random failure of components and the faults stay for short while and are then diagnosed or tested. 

The most important characteristic of fault is duration. So, fault can he classified utilizing this characteristic feature. Based on duration, the fault can he classified as a permanent/solid/hard fault and a transient/intermittent/soft fault. In most systems the majority of faults are transient faults (above 80%). Transient faults, or intermittent faults, can be defined as random failures that prevent the proper operation of a unit for only a short period of time—not long enough to be tested and diagnosed as a permanent failure. 

This plant was operated with three electrical generators TG-2, TG-3 y TG-4. The power electrical system was synchronized to the public network through a "link" principal transformer. The electric network of this plant was ungrounded during a fault or there was not ground reference in system by a previous fault. Subsequently, in another site a fault occurs in a switchboard called "extension bus bar of TG-2" at voltage level of a 13.8 kV. The fault consists of an arc flash between bus bar and switchboard walls when the network was steady. Transient oscillations of the frequencies derived of the arc were timed to the circuit, and it was in resonance. The evidence shows that intermittent arc flash occurs, pa-omoted electro-erosion as is shown in Fig. 3.5.2.1. 

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