Urs Krüsi, Bestimmung und Beurteilung der Charakteristika von ...

Abstract
Numerous publications show that controlled switching is nowadays an established
means to reducing switching transients in HVAC networks. Effective
controlled switching requires the closing characteristic of the circuit-breaker
to be reproducible. For this the closing characteristic and the dependencies
of the closing time from such parameters as temperature, drive energy,
close-coil voltage and idle time are required to be available. These dependencies
are not known for circuit-breakers that are already installed in the
network, and it is usually impossible to get the data from the manufacturer.
Furthermore, no method is available that efficiently identifies the closing
characteristic and dependencies and is capable of calculating the remaining
scatter of the closing time of the circuit-breaker. Finally no method exists
that would allow the evaluation of the suitability of the circuit-breaker for
controlled switching.
In a first step, a method is developed that calculates the closing characteristic
(RDDS) and the dependencies of the closing time from the
parameters on an installed circuit-breaker. With these results, the nondeterministic
scatter of the mechanical closing time can be determined. A
specifically developed mathematical model simulates the circuit-breaker
closing characteristic. In the investigated range, the value of the nondeterministic
scatter does not affect its efficiency. Laboratory tests on a
145 kV SF6 circuit-breaker with a compressed-air drive verified the applicability
of the method. Initially, the dependencies of the closing time on
drive energy, close-coil voltage and idle-time are independently measured,
varying only one parameter at a time. Subsequently, all three parameters
are varied at the same time and the measured prestrike instants are evaluated
using the proposed method. The closing times varied between -6.5 ms
and 7.3 ms. The identified dependencies are in good agreement with the
former that were independently determined. The non-deterministic mecha-