Discussion on the application of input switching v

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Talking about the application of input switching value in the accident treatment of microcomputer protection device


the experimental unit can set it arbitrarily according to the demand

the outstanding advantages of automatic detection of microcomputer protection device. It has many self-test items, and the self-test of input switching value is one of them. When the protection device detects that some input switching values change, some functions of the microcomputer protection device will be locked and printed out by the printer. At the same time, the self-test of input switching value also provides us with great help in dealing with the accidents of microcomputer protection devices

1. Definition of switching value and classification of input switching value

switching value refers to contact state (on or off) or logic level, etc. The switching value can be divided into input switching value and output switching value, and the input switching value can be divided into:

(1) internal switching value: the switching value that reflects the state of the internal contact installed in the switching value is called internal switching value. For example, the input circuit of the change-over switch of various working modes, the operating keyboard contact, reset button and other buttons used in the regular inspection of the protection device during commissioning or operation is shown in figure (a)

(2) external switching value: from the outside of the microcomputer protection device, the contact of the device is introduced through the terminal block. This kind of switching value mainly includes various pressing plates, connecting pieces, switching switch contacts and operating relay contacts on the protection screen. The input circuit is as shown in figure (b). Due to the connection with the external circuit, such contacts cannot be input as shown in figure (a), but need to be isolated by optocoupler to avoid the interference caused by contact input

2. Application of input switching values in accident handling

after these switching values are input to each CPU, the CPU will read the status of each switching value and store it in the address specified in the RAM area. In the self-test, the current input switching value state is continuously read and compared with the original switching value state. If it is found that the input switching value changes, a call signal will be sent, and the status of each input switching value before and after the input switching value changes will be printed. When dealing with the accident of microcomputer protection device, we should make full use of the changes of these switching values to shorten the accident processing time

first, when dealing with the failure that the transceiver of LFP-901A (or 902A) protection device cannot start sending signals, we should make full use of the relevant switching value of protection device CPU1. We have used these switching values to deal with such an accident: 220kV Qingyuan substation 220kV Qinghong line A-phase protection (the protection device is LFP-901A, equipped with sf600 transceiver) when the transceiver uses the channel test button, the transceiver cannot start sending messages, as shown in the following figure. The processing process is:

(1) enter the input switching value status submenu of CPU1, find out Chnl (channel test), and the status is 0 at this time. When the button is pressed, Chnl changes from 0 to 1. This indicates that the test button and + 24V power supply are normal, which eliminates the possibility of button damage or + 24V power supply abnormality

(2) look down under the input switching value status submenu and find that SX (receiving empty contact) is 1. At this time, the transceiver does not receive any high-frequency signal (measured on the high-frequency cable side with a level meter). Because SX is 1, the protection device locks the signaling procedure because the transceiver is in the receiving state for a long time

(3) then pull out the transceiver 10 plug-in (demodulation output plug-in) and measure the output null contact of sxj. It is found that it is conductive in the normal state and the contact is stuck. After replacing another pair of spare contacts, it is normal to open the signal with the button

if such an accident does not make full use of the switching value, most relay protection personnel think that there is a problem with the opening circuit of the transceiver itself, so it is impossible to accurately and quickly find out the cause of the accident and solve the problem in time

secondly, when the reclosing of the protection device cannot be charged, we should make full use of these switching values: hhkk (KK after closing), HYJ (pressure locking reclosing empty contact), bsch (locking reclosing pressing plate or contact), TWJ (tripping position contact), etc. For example, when testing the 110kV line protection device of LFP-900 series, it is customary to close the analog circuit breaker, and then turn the control KK to the closed position, there is a phenomenon that the CD light (reclosing charging light) does not light (that is, it cannot be charged), while other displays are normal. So the input of the protection device is on, so these departments are becoming the submenu of the off state of domestic hydrostatic forklift users. It is found that at this time, HYJ is 0; TWJ is 0; Hhkk is 0; Bsch is 0. It can be seen that the reason why reclosing cannot be charged is that hhkk is 0. It is found by consulting the drawing (as shown in the figure): Although the KK is turned to the closed position ⑤⑧, the positive power supply cannot be turned on to make the kkj act, so after closing the analog circuit breaker according to the steps of normal operation switch, the CD light is on

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