Analysis of several types of alternative operation

Analysis of several types of alternative operation in substations

[Abstract] alternative operation is a common switching operation form in substations. Due to the requirements related to secondary circuits, a little carelessness, that is,

may lead to misoperation. Combined with the actual situation, this paper analyzes the relevant links that should be paid attention to in several common circuit replacement switching operations in substations, points out the errors that are easy to occur, and introduces the correct operation steps and precautions

[keyword] substation; Routing operation; Precautions

there are many types of switching operation of electrical equipment in substations, among which the business substitution operation, which will continue to expand in China in the future, is a more common form of switching operation. This kind of operation requires the operators to understand some intermediate links, especially the requirements related to the secondary circuit of relay protection. If there is a problem in this regard, it may lead to misoperation, 14% of which is used for combustion or energy recovery, which directly threatens the safe operation of people and equipment. Now, the relevant links that should be paid attention to in several common alternative switching operations in substations are analyzed as follows

1 alternative operation between distribution switches

1.1 alternative operation between distribution switches on the same power bus through the bypass bus

alternative operation between distribution switches is usually common in 10 kV distribution systems, that is, when the switch encounters maintenance, pre-test, protection verification and other work and the line does not allow power failure, the method of alternative operation through the bypass bus is often used to stop the working switch

as shown in figure shapeways scale 1, the correct operation sequence of "621 is led by 623, and 621 switch is turned from operation to maintenance" is as follows: (1) check that the bus is normal; (2) Close the knife switch; (3) Remove the 623 switch control fuse; (4) Remove the 621 switch control fuse; (5) Close the knife switch; (6) Check that the load distribution of 621 and 623 is normal; (7) Apply 621 switch control fuse; (8) Apply 623 switch control fuse; (9) Open the 621 switch; (10) Open the knife brake; (11) Open the knife brake; (12) Check the electricity and seal the ground on both sides of 621 switch

in actual operation, the following incorrect operation sequences are easy to occur, which brings varying degrees of hidden dangers to the safe operation of equipment and the reliable power supply of lines. The specific analysis is as follows:

(1) before closing the bypass switching of the substitute switch, the control fuse or control switch of the substitute switch has been removed, that is, the sequence of the above operation items (2) and (3) is reversed. This switching operation sequence is obviously incorrect. From the perspective of operation regulations, although it is allowed to open or close the no-load bus with the disconnector, the precondition must be that the no-load bus is fault free. If the operation sequence is followed, once there is a problem with the bypass bus (usually refers to the bypass bus without a special bypass switch), because the control insurance of the substitute switch 623 has been removed, the substitute switch 623 will not be able to trip in time, causing the upper switch 201 to skip the level and expand the scope of power outage. The correct order of filling in the operation ticket is to close the bypass knife switch of the substitute switch 623 first. At this time, if the bus is faulty, the protection of the switch 623 will act correctly to make it fall off quickly, so as to avoid the expansion of the accident

(2) operate without taking the control insurance of the switch or only taking the control insurance of one switch, that is, cancel the operation item (3), (4) or any one of them. 4. Replace the window diaphragm in a clean and dust-free environment. In this way, at the moment when the bypass knife switch of the replaced switch 621 is operated in turn, if the switch line fault protection action without control insurance falls off or the switch falls off by mistake, the accident of directly closing the knife switch to the faulty line or closing the knife switch with line load will occur