Pause switch
A pause switch , English sectionalizer is, in the electric power industry a special type of disconnector with a very small switching capacity. It primarily serves to increase the average security of supply for overhead lines in the medium-voltage network and limits a long-term power failure to a smaller supply area.
In the medium-voltage networks in Europe, break switches are comparatively seldom found, as earth fault compensation is an effective measure to increase security of supply. By contrast, in countries such as Australia and South American countries, where medium-voltage networks are operated without earth fault compensation, which is inevitably the case in the Single-Wire Earth Return system , break switches are common in the individual sections of a branched medium-voltage network.
function
A break switch increases the reliability in a segment of the medium-voltage network by separating the faulty overhead line section from the rest of the network, so that the rest of the fault-free part of the medium-voltage network can continue to operate after only a short interruption thanks to the automatic reclosing function . The automatic restart after a fault detected by the network protection is carried out by the upstream circuit breaker in the centrally located substation , which disconnects a larger section of the network in the event of a fault. Since the cause of the fault in overhead lines is eliminated in many cases by the arcing fault occurring at the fault location , e.g. B. a branch that has fallen on the line burns, an automatic restart is carried out after a short interruption. If the error persists, however, a certain number of reclosing attempts are attempted via the circuit breaker. In this sequence, the individual break switches can disconnect the faulty network section, so that the remaining network sections can continue to be supplied after the last successful restart attempt.
To detect a fault in the relevant line section, the break switch has its own, integrated current transformers , which also serve to supply power to the control electronics integrated in the switch. The pause switch has a built-in counter so that the number of incorrect reclosing attempts can be assessed. If a certain counter reading is reached in the break switch, this corresponds to a number of unsuccessful attempts to switch on the circuit breaker in the substation, the break switch disconnects the line while the voltage is off. In this way, it separates the faulty line section from the rest of the network. As part of the configuration of the break switch, the limit values of the internal counters must be set in such a way that larger parts of the supply network are successively shed if a short circuit persists. Once the break switch has been triggered and opened, it can only be closed again manually on site using a switching rod , since the permanent fault in the line section must first be found and eliminated by the maintenance staff.
Break switches are much cheaper in their design than circuit breakers, as they only disconnect the line when the power is off and therefore do not have any complex arc extinguishing device .