For instance, think of station areas where typically every platform will be it’s own sub-section. Because of this, the electrical sections are typically split into multiple sub-sections where these sub-sections are traditionally electrically separated via switch disconnectors. Because these electrical sections are typically in the 10’s of miles long, there are times when it may be necessary to reduce the electrical section (typically when maintenance is being completed or there is an incident). The railway’s devices may look a little bit different, but they are the same function as this article.įrom a railway perspective, each overhead line electrical section is supplied via circuit breakers. I should be able to provide a scenario for the purpose of switch disconnectors with regards to the UK railway. Reference: Low-Voltage Switchgear and Controlgear – Rockwell Automation Circuit breakers are often designed so that they can fulfill the requirements for disconnectors. They thus also fulfill the requirements of (load) switches. Circuit breakers Schneider Electric’s low voltage moulded case circuit breaker (MCCB) type Compact NSXĬircuit breakers are mechanical switching devices, capable of making, carrying and breaking currents under normal circuit conditions and also making, carrying for a specified time and breaking currents under specified abnormal circuit conditions such as those of short-circuit (IEC 60947-2). Switch disconnectors combine the properties of (load) switches and disconnectors. In this case, too, there are a variety of designs such as “normal” switch disconnectors, fuse- switch-disconnectors and circuit breakers.įuse-switch-disconnectors are not legally permitted in all countries.Ĥ. Switch disconnectors Switch disconnectors Left – ABB’s motorized switch disconnector 160-2500A Right – Schneider Electric’s low-voltage disconnect switch with free tripping 80-3200A (photo credit: ) Load switches (or only “switches”) are mechanical switching devices capable of making, carrying and breaking currents under normal circuit conditions which may include specified operating overload conditions and also carrying for a specified time currents under specified abnormal circuit conditions such as those of short-circuit.ģ. Load switches 4 pole load break switch with visible breaking and a remote tripping function (photo credit: ) The isolator function can be realized with a variety of devices such as for example in disconnectors, fuse-disconnectors, switch-disconnectors, fuse-switch disconnectors and circuit breakers with isolating function.Ģ. short-circuit currents) for a certain period. Under normal conditions it can conduct operational currents as well as under abnormal conditions larger currents (e.g. This is to be verified by testing.Īccording to IEC 60947-3, an isolator must only be able to make and break a circuit, if either a current of negligible size is switched on or off, or if during switching no noticeable voltage difference between the terminals of each pole occurs. This position indicator must be linked in a secure, reliable way to the actuator, whereby the position indicator can also serve as actuator, provided that it can only display the position “Open” in the “OFF” position, when all moving contacts are in the “Open” position. It must also be equipped with an indicator device in relation to the position of the movable contacts. Isolation must be guaranteed from pole to pole and from input to output, whether this is by means of a visible isolation gap or by suitable design features within the device (mechanical interlocking mechanism).Ī device fulfills the isolating function stipulated under IEC 60947-1 when in the “Open” position the isolation at a defined withstand voltage is assured between the open contacts of the main circuit of the switchgear. The key factor here is the opening distance. The purpose of the isolating function is to cut off the supply from all or a discrete section of the installation by separating the installation or section from every source of electrical energy for reasons of safety.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |