In the field of electrical engineering, a relay is a relay device designed to trip a switch when an error is detected. The first protection relays were electromagnetic devices based on mobile coils in motion to guarantee abnormal operating conditions such as over current, over voltage, inverse flow, over frequency and reduced frequency.
The digital protection relays based on microprocessors now emulate the original devices, in addition to providing non-practical protection and non-mechanical monitoring with electromechanical relays.
PSM in relay
Electromechanical relays provide only rudimentary indications of objectives in phases and areas. In many cases, a single microprocessor relay offers functions that would require two or more electromechanical devices.
Combining multiple functions in a single case, the numerical relays also save maintenance costs and maintenance costs of electromechanical relays. However, due to its long service life, tens of thousands of these “silent sand jets” still protect the transmission lines and the world from electrical appliances.
The main transmission lines and generators have dedicated protection cabinets with numerous individual electromechanical devices or one or two microprocessor relays.
The theory and application of these protective devices is an important part of the education of an energy engineer who specializes in the protection of energy systems. The need to act quickly to protect circuits and equipment, as well as the general public, often requires protection relays to respond and activate a switch in a few milliseconds. In some cases, these release times are prescribed by law or by operating rules.
A maintenance or test program is used to determine the performance and availability of protection systems.