Application of Input Switching Value in Accident Treatment of Microcomputer Protection Device

The outstanding advantages of automatic detection microcomputer protection device. It has a lot of self-test items, the self-test of the input switch is one of them. When the protection device detects the change of some input switching value, it will lock some functions of the microcomputer protection device and print them out through the printer. At the same time, the self-test of the input switch also provides us with great help in dealing with the accident of the microcomputer protection device.

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

The switching value is the contact state (on or off) or the level of the logic level. The switching quantity can be divided into input switching quantity and output switching quantity, and the input switching quantity can be divided:

(1) Internal switching quantity: The switching quantity that reflects the state of the internal contact installed in the switching quantity is called the internal switching quantity. For example, the switch of various working modes, the operation keyboard contact, reset button and other buttons used by the protection device during debugging or periodic inspection in operation, and the input circuit is shown in Figure (a).

(2) External switching value: from the outside of the microcomputer protection device, the contacts of the device are introduced through the terminal block. This kind of switch mainly includes various pressure plates on the protection screen, connected pieces, switch contacts and contact points of operating relays. The input circuit is shown in Figure (B). Such contacts cannot be input as shown in Figure (a) due to their connection with the external circuit. They need to be isolated by photoelectric couplers to avoid interference caused by contact input.

2. Application of input switching value in accident treatment

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

First, when dealing with the failure that the transceiver of the LFP-901A (or 902A) protection device cannot start transmitting, the relevant switching value of the protection device CPU1 should be fully utilized. We have used these switching values to deal with such an accident: when the 220kV Qingyuan substation 220kV clear red line phase a protection (the protection device is LFP-901A, equipped with SF600 transceiver) transceiver uses the "channel test" button, the transceiver cannot start sending a signal, as shown in the following figure. The process is:

(1) Enter the input switch state submenu of CPU1 to find out "CHNL" (channel test), and the state is "0" at this time ". When the button is pressed, "CHNL" changes from "0" to "1". This shows that the test button and the +24V power supply are normal, and the possibility of button damage or abnormal +24V power supply is excluded.

(2) Look down again under the input switch state 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 blocks the start-up procedure for the transceiver in the receiving state for a long time.

(3) Then the transceiver #10 plug-in (demodulation output plug-in) was pulled out to measure the output empty contact of SXJ, and it was found that it was turned on in the normal state and the contact was stuck. After replacing another pair of spare contacts, it is normal to use the button to start the letter.

If such an accident does not make full use of the switching quantity, most of the relay protection personnel think that there is a problem with the transceiver itself, and the cause of the accident cannot be accurately and quickly found, and the problem cannot be solved in time.

Secondly, when the reclosing of the protection device cannot be charged, these switching values should be fully utilized: HHKK (closed KK), HYJ (pressure locking reclosing empty contact), BSCH (locking reclosing pressure plate or contact), TWJ (trip position contact), etc. For example, when testing LFP-900 series 110kV line protection devices, it is customary to close the analog circuit breaker and then turn the control KK to the closed position, resulting in the phenomenon that the "CD" lamp (reclosing charging lamp) is not on (I. e. cannot be charged), while other displays are normal. Then enter the sub-menu of the input switch state of the protection device and find: HYJ is "0" at this time; TWJ is "0"; HHKK is "0"; BSCH is "0". It can be seen that the reason why the reclosing cannot be charged is that the HHKK is "0".