Are OCR's on taps rated in adjacent sizes allowed to drop down by two sizes?

In the context of electrical systems and lineman practices, Overcurrent Relays (OCRs) play a critical role in protecting circuits from overloads and short circuits. When it comes to applying OCRs on taps, particularly those rated in adjacent sizes, it is indeed permissible for them to drop down by two sizes.

This flexibility allows for the proper coordination of protection devices in a given system. Dropping down the size of the OCR ensures that the relay can effectively detect and respond to fault conditions without tripping unnecessarily for normal operating conditions. This adaptability can be essential in maintaining system reliability and ensuring that circuits are protected adequately without compromising safety.

It’s also important to understand the function of OCRs in relation to the overall system design. By allowing for the use of OCRs rated in adjacent sizes, electrical engineers can optimize the protection scheme, ensuring that devices are matched correctly to the load they are protecting. This can lead to enhanced system efficiency and reduced downtime in case of faults.

While there are scenarios where special approvals or conditions apply, the standard practice permits this sizing flexibility to enhance the operability and reliability of the electrical system.