Fault levels generator circuits

For a switching device (which has not been previously tested for a short-circuit test). This should be closed and held in the normal service position. The test voltage (that would generate the required level of fault current) may be applied on one set of terminals, the other terminals being shorted. The test may be continued until the short-circuit device operates to clear the fault, but in no case for less than 10 cycles. In LT assemblies the point where the short-circuit is created should be 2 0.4 m from the nearest point of supply. 

At low p.f.s the generator operates at a low level of excitations (armature reaction demagnetizing). During a fault, therefore, when the p.f. of the circuit falls it will also cause a fall in the excitation level and in turn in the terminal voltage. A low voltage, however, would reduce the severity of the fault. 

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. 

---