Protection configuration of switchgear

10kV feeder switchgear generally adopts two-stage current protection with reclosing, and important lines will adopt optical fiber longitudinal differential protection.

(a) Basic concepts

Two-level current: over-current level is also called current quick-break protection; there is no time limit, set higher than the maximum short-circuit current at the end of this stage; over-current two-stage is also called time-limited current quick-break protection. Set according to the maximum operating current higher than the lower-level protection current quick-break protection. It can be used as backup protection for the first section of the line. The operation trip time is generally 0.5-1 second.

Reclosing: When the overhead line fault is cleared, the circuit breaker is closed in a short time, which is called reclosing; in fact, most overhead line faults are instantaneous or temporary, so reclosing is a self-recovery power supply often used in operation One way.

(2) Types and structures of commonly used protection devices

We often use two types, one is electromagnetic protection, the other is microcomputer protection

1. The composition of the protection device:

(1) Electromagnetic protection is composed of current relay, time relay, intermediate relay, signal relay, reclosing relay, pressure plate, etc.

(2) Microcomputer protection is composed of power plug-in, export plug-in, CPU plug-in, AC plug-in, man-machine dialogue plug-in, pressure plate, etc.

2. Protection device action information and description:

(1) The action information of the electromagnetic protection is reflected on the signal relay and the reclosing charging lamp. After the protection is activated, the corresponding signal relay will operate the dr card until it returns manually. In addition, after the electromagnetic protection device itself is abnormal, there will be no obvious abnormality under normal circumstances, and it is not easy to find.

(2) When an action or alarm occurs during the operation of the microcomputer protection, the LCD backlight will automatically turn on, and the action information will be displayed on the LCD (see the following table). At the same time, it will be uploaded to the protection management machine or local monitoring for timely detection and processing.