ZDB-03 Countercurrent protection device

1 Overview

Figure (a) countercurrent protection device

The countercurrent protection device mainly has two kinds of protection functions, namely, the reverse current protection function and the positive overcurrent protection function. The device is specially designed

It is composed of a counter-current special sensor, a counterflow detector and a dedicated cable.

In the parallel power supply system of two or more rectifier units, if there is a short-circuit fault in the DC bus within a sub-station DC bus or rectifier, it will cause the total bus to feed back current to the fault point, that is, to form a reverse flow. Especially in the case of high DC voltage, it will form a great countercurrent, which will cause the failure to expand and even explode, resulting in greater losses.

ZDB-03 type countercurrent protection device is a kind of DC high-current reverse current protection device which can effectively prevent the accident from expanding due to backflow, and can be used as the DC backup protection element when each sub-station DC bus and the rectifier device internal DC bus short circuit fault. Positive overcurrent can be detected and alarms in the 100%-150% range.

The ZDB type countercurrent protection device was originally applied to the copper smelting industry in 1995. Later, in some aluminum smelting industries, there were many back-flow accidents and even some individual explosion accidents occurred. Therefore, the ZDB type countercurrent protection device was also widely used in the aluminum smelting industry. In particular, many units using the company's ZDY-N sensors have been put into use according to design requirements.

In response to the phenomenon of reverse flow failure due to large currents in aluminum electrolysis, our company developed the new type of countercurrent protection device ZDB-03 on the basis of the original countercurrent protection technology. After field use, ZDB-03 type countercurrent protection device is accurate and reliable as long as it is correctly installed and used as required.

2 . working principle

The ZDB-03 type countercurrent protection device detects the direction of the current at the dedicated sensor installation. When there is a reverse current equal to 10% of the forward current, the counterflow detector has an output signal to trip the circuit; when a reverse flow fault occurs, the counterflow detection occurs. The instrument can directly start the AC side (network side) of the microcomputer protection circuit (or relay protection circuit), so that the AC side (network side) corresponding circuit breaker breaking, cut off the fault current; ZDB-03 type backflow protection device can also be positive Connected to the sensor, when positive overcurrent occurs, there may be a signal output to the alarm loop, adjustable from 100% to 150%. See figure (b)

Figure (II) Schematic diagram of working principle of ZDB-03 countercurrent protection device

3. Technical indicators

Product Model: ZDB-03;

Working power: ~ 220V ± 10%;

Accuracy: 1%;

Protection setting: countercurrent 1KA-9KA adjustable; overcurrent 100%-150% adjustable;

Input: Detection signal of special countercurrent sensor;

Positive DC high current sensor detection signal 0-1V (or 0-5V);

Output: reverse flow, 2 normally open contacts, with load capacity: AC 2A, ~220V, DC 0.4A, 220V,

Positive overcurrent 100%-150%, a normally open contact, with load capacity: AC 2A, ~ 220V, DC 0.4A, 220V;

Response time: <10 ms ;