Proper transfer switching can maintain an integrated, secure power supply. This is where Transfer Switching Equipment (TSE) comes into play: It disconnects a load from one provider and connects it to another. If the main power supply of one system suffers an outage, for example, it switches to the backup supply. In addition to classic infrastructure installations, transfer switching is also playing a leading role in control panels.
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Transfer switching equipment can be categorized according to their actuating method:
- Manual Transfer Switching Equipment (MTSE) enables manual switchover between two supply sources. The switchover is carried out with a rotary operator.
- Remotely Operated Transfer Switching Equipment (RTSE) has an integrated motor operator. This is controlled via external signaling, switching remotely between the two supply sources.
- Automatic Transfer Switching Equipment (ATSE) also features an integrated motor. In addition, it is equipped with a control unit, along with a monitoring function. In case of a fault in the main supply source, the network transfer switching equipment registers a drop in the voltage and frequency and automatically switches to the backup supply.
Unlike transfer switching equipment that switches between two supply sources for a uniform load, load break switches on a uniform supply source switch between two load lines.
Time as a factor:
Operators should adjust the downtime of the transfer switching solution to the key performance indicators of the connected loads.
- IT hardware can frequently tolerate only very brief interruptions, which is why they ought to be additionally safeguarded with an uninterruptible power supply.
- Motors running out or power supply units ramping up rely on a certain reversing time for smooth functioning.
Distribution boards as a factor:
Depending upon the distributor board, various types of switches are suitable for transfer switching.
- Main power distribution boards are usually fed by air circuit breakers – that is why they are also a good option for transfer switching.
- Sub-distribution boards can be transfer switched between networks both with circuit breakers and switch disconnectors.
- Critical loads involve matters of personal safety and during downtimes can lead to severe economic loss. A backup supply is an absolute necessity here, as in combination with automatic transfer switching, it guarantees a virtually continuous power supply.
- The downtime of a critical load can cause partial impairment of production processes, which can lead to moderately severe economic loss. Even for loads like these, a backup supply is recommended, whereby transfer switching can be remote or manual. Particularly in the latter case, supply reliability can only be guaranteed, however, if there are persons on-site who can activate the switchover.
- In case there is a failure of non-critical loads, there is little or no impairment of production processes. This is where possible load shedding can occur: By excluding non-critical loads from the emergency power supply, operators can deploy smaller units.
- Transfer switching equipment switches between transformers and generators (the most typical application), between two transformers, or between two generators.
- Outputs for the machine control system ensure that an automatic transfer switch can independently start up and stop a generator that is not in continuous operation.
- Electrical or mechanical interlocking prevents the switching of non-interlocked switches at the same time in one transfer switch.
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