Switch image
The switch image shows the switching status of an electrical system, e.g. B. a switching station or a substation .
task
It is used to control the relevant system and enables the selection of system parts or areas. In this way, certain commands only reach parts of the system which, according to the switch image, have a certain state - ON or OFF. A lock various parts of the plant or primary devices ( circuit breaker , disconnectors ) against each other is usually realized by means of a switch image. At the same time, it can be used to duplicate auxiliary contacts on the primary devices.
functionality
Primary devices are usually equipped with auxiliary contacts. These report z. B. the state of the respective device, z. B. "Circuit breaker on" = contact closed. Such auxiliary contacts are attached to the primary device and thus z. B. distributed in a switchgear over a fairly large area. In order to reduce material and assembly costs, relays are also controlled by these auxiliary contacts . B. Auxiliary contact closed = relay picked up.
Due to the compact design of the relays, several relays, which are controlled by different primary devices, can be accommodated in the smallest of spaces (e.g. control cabinet, control panel). Instead of wiring all control signals directly via the auxiliary contacts on the primary devices, the contacts of the switch image relays can be used. Since the relays used have several contacts, there is also a multiplication of contacts: a relay can provide several NO / NC contacts. The auxiliary contact of the primary device, for. B. generate acoustic and visual messages.
advantages
In order to recognize the switching status of the system or certain primary devices, it is sufficient to look at the relays of the switch image or the signal transmitters controlled by them (lamps, indicators ).
Contact multiplication : Theoretically, the auxiliary contacts can be multiplied almost infinitely if several relays are connected in parallel.
Cost savings through shorter cable runs: control signals can be routed via the contacts of the switch replica relay instead of directly via the auxiliary devices on the primary device (e.g. off signals from breaker failure protection or busbar protection )
Electrical isolation: The coils of the relays are z. E.g. controlled with 230 V, but the contacts can switch other and different voltages (depending on application e.g. 24 V, 60 V, 100 V etc.)
disadvantage
Additional sources of error: In the event of a faulty signal flow, the error can now lie with the auxiliary contact on the primary device or with the relay or relays in the switch pattern.