Discussion on the application of input switching v

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

introduction

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