The article mainly discusses the role and composition of power system relay protection, and puts forward relevant protection measures, which is of great significance in relay protection work.
1 The role, composition and requirements of power system relay protection
1.1 The role of relay protection
When the protected component of the power system fails, the relay protection device can automatically and selectively remove the faulty component from the power system to ensure that the fault-free part returns to normal operation, so that the faulty component can be prevented from continuing to be damaged. In order to reduce the scope of power outages; if the protected component is in an abnormal operating state, the relay protection device can react in time to issue a signal, reduce the load or trip the action command according to the maintenance conditions. At this time, it is generally not required to protect the rapid action, but a certain delay is imposed according to the degree of damage to the power system and its components to avoid unnecessary actions. At the same time, the relay protection device is also a monitoring device of the power system, which can measure the current and voltage of the system in time, thereby reflecting the operating state of the system equipment.
1.2 Composition and requirements of relay protection
Relay protection generally consists of an input part, a measurement part, a logic judgment part, and an output execution part. The field signal input part is generally required to perform necessary pre-processing, such as isolation, level shifting, low-pass filtering, etc., so that the relay can effectively check the physical quantity of each site. The measurement signal is converted into a logic signal. According to the size, nature, logic state, output order and other information of each output quantity of the measurement part, the operation is combined according to a certain logical relationship, and the final execution task is completed by the output execution part.
The basic requirements for relay protection should meet the requirements of selectivity, quickness, sensitivity and reliability. Selective means that when the protection device is in operation, only the faulty device is cut off from the power system, so that the scope of the power failure is reduced as much as possible to ensure the normal operation of the fault-free part of the system; the quick action means that the protection device should cut off the short-circuit fault as soon as possible. Its purpose is to improve the stability of the system, thereby reducing the damage degree of faulty equipment and lines, reducing the range affected by the fault, and improving the automatic input of automatic reclosing and standby equipment. Sensitivity refers to the ability to respond to faults or abnormal operating conditions within the scope of protection. Reliability refers to the degree of reliability of the relay protection device when it operates within the protection range.
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