ABB RELION REB500 Technical Manual page 161

1MRK 505 406-UEN B
Since the dead time settings do not correspond to the effective total dead times, especially in
a scheme with two circuit-breakers (see Figure 60), the period during which the circuit-breaker
is actually open must be measured. This entails adjusting the dead time until the measured
breaker time minus arcing and pre-ignition times and the inevitable CB tolerances result in an
adequate composite dead time.
Providing the circuit-breakers at both ends of the line are of the same type and thus permit the
same tolerances to be assumed at both ends, the same dead time t
terminal stations. Where this is not the case, the tripping and closing times of the two circuit-
breakers must also be measured in addition to the dead times. The dead times set for the two
autoreclosure functions must then ensure that a sufficiently long "overlapping" dead time
exists to enable the circuit-breakers to deionize.
Bay protection functions REB500
Technical manual
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Section 5
Bay protection functions
can be set in the two
p
155