JPH062196A - In-line insulation monitoring method for continuous electrical processing equipment for metal strips - Google Patents

Abstract

(57) [Summary] [Purpose] Inspecting the insulation condition while the line is in operation,
And identify the location of the defect. [Structure] In the electroplating equipment for steel strip 1 using n rectifiers 4 as a power supply, the earth current can be continuously measured by rotating the earth rolls 8 and 8'to the steel strip 1 and the line speed can be continuously measured. Is set to a speed that can be covered by (n-1) rectifiers, the circuit is sequentially disconnected from the line and opened for each rectifier, and the earth resistance of each rectifier is obtained by measuring the earth current at that time. Monitor insulation.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a continuous electric treatment facility for metal strips such as steel strips and wires equipped with a large number of large capacity rectifiers.
For example, it relates to an in-line insulation monitoring method for electroplating, electrolytic lines, and the like.

[0002]

2. Description of the Related Art Conventionally, in order to inspect the insulation state of each rectifier or electrode in a continuous electric treatment facility for steel strips, wire rods, and other metal strips having a large number of large-capacity rectifiers, such as electroplating and electrolytic lines It was usual to measure the insulation resistance one by one using a measuring device called a tester or a megger while the power was cut off on a line rest day. However, this method not only takes a lot of time and effort when the number of rectifiers increases, but also cannot measure during operation, so it is not possible to deal with the insulation failure that gradually deteriorates during operation, and the insulation deterioration part It even generated heat and caused a fire.

Further, since the resistance value of the plating solution, bus bar, steel strip, etc. in a normal state is usually extremely lower than the resistance value of the leakage current circuit, it is impossible to detect insulation deterioration by a change in voltage or the like. Almost impossible. Even if the power was partially turned off during the operation, it was necessary to drain the conductive processing liquid such as the plating liquid for the insulation measurement, and the line had to be stopped for a certain time.

On the other hand, Japanese Patent Laid-Open No. 3-36291 discloses adjusting the current distribution to the electrodes while measuring the ground potential at the contact point between the current-carrying roll and the steel strip in the electrolytic cell. However, this is intended to reduce the circulating current flowing through the earth roll due to the difference in ground potential across all lines, and does not measure the leakage current due to defective insulation during operation.

Further, the applicant of the present invention has previously mentioned that "a ground current suppressing device in electrolytic equipment such as electroplating" (Japanese Utility Model Application No. 3-8511).
No. 8) filed, it measures the current flowing through the earth roll to judge the insulation failure of the entire line, but since it is not possible to identify the defective part when many rectifiers are grounded, these Neither is an effective means for solving the problems to be solved by the present invention.

[0006]

SUMMARY OF THE INVENTION It is an object of the present invention to provide an in-line insulation monitoring method capable of measuring the presence or absence of insulation failure in a line operation state, that is, in-line, and identifying the location of the failure.

[0007]

DISCLOSURE OF THE INVENTION The present invention provides a continuous electrical treatment facility for metal strips using n rectifiers as a power source.
An earth roll is rotatably contacted with the metal strip to make it possible to continuously measure the earth current, and the line speed of the continuous electric processing equipment is set to a speed that can be covered by (n-1) rectifiers. This is an in-line insulation monitoring method in a continuous electrical treatment facility for metal strips, characterized in that the ground resistance of each rectifier is determined by sequentially disconnecting the circuit from each line and opening the circuit and measuring the ground current.

[0008]

[Operation] In continuous electrical treatment equipment for metal strips that is subjected to electrolytic treatment, electroplating, etc., a large number of rectifiers are used in parallel to configure the circuit. Therefore, electrical treatment depends on the difference in the voltage drop of each rectifier circuit. A potential difference may occur between the entry side and the exit side of the section, and in order to absorb this potential difference and avoid problems such as electrolytic corrosion, a conductive earth roll is installed,
A metal strip is brought into contact with the surface of the earth roll and grounded to the ground via a conductive brush.

The present invention is based on the fact that the leakage current flows through the earth roll even when the electrodes have poor insulation, and the earth roll current is basically measured. The method for identifying a defective electrode among a large number of electrodes is as follows. Taking a continuous strip galvanizing line for steel strips as an example, the amount of plating metal deposited on the steel strip surface, the so-called basis weight, is
It is proportional to the current flowing and inversely proportional to the line speed. That is,

[0010]

[Equation 1]

There is a relationship of Therefore, it is not necessary to energize all the rectifiers to perform normal plating except when performing plating with a particularly high basis weight, and if the line speed is limited, basically one rectifier is not energized per side. can do. Therefore, after adjusting the line speed so that it does not fall below the predetermined basis weight, cut the rectifier circuit one by one, switch the rectifiers that are sequentially cut, and measure the earth roll current at that time. Recognize.

FIG. 2 is a conceptual diagram in the vicinity of the electrodes, schematically showing only one rectifier and one electrode. 1 is a steel strip, for example
Reference numeral 3 is a conductor roll (cathode), 4 is a rectifier, 5 is an anode, and 8 is an earth roll. A normal plating current e ₁ flows from the anode 5 through the steel strip 1, but is insulated near the rectifier 4 or the anode 3. If there is a defective portion 7, the leakage current i _e1 flows through this defective insulating portion 7 to the earth roll 8.

Now, it is assumed that there are n rectifiers and there is no potential difference before and after the processing tank due to the voltage drop of the rectifiers. The leakage current flowing through the earth roll when the i-th rectifier is cut is I _ei (A), the voltage of the i-th rectifier is E _i (V), and the insulation resistance of the i-th electrode is r _i (Ω).
When (i = 1, 2, 3, ... N), the following equations hold.

[0014]

[Equation 2]

Therefore,

[0016]

[Equation 3]

By solving, the insulation resistance r _k (Ω) of the k-th rectifier among the n units is

[0018]

[Equation 4]

Thus, the insulation degree of each rectifier can be known. Actually, there is a current due to the voltage drop that was assumed to be 0, and there are other error factors, but
This method is sufficient for insulation condition management to avoid troubles such as fire. As a result, it is possible to temporarily turn off the power of the rectifier determined to be defective and continue the operation.

[0020]

EXAMPLE FIG. 1 is a system diagram showing an example of the present invention in an electrogalvanizing line for steel strips. 1 is a steel strip, 2 is a plating tank, 3 is a conductor roll, 5 is an electrode (anode), 4 Is a rectifier, 6 is a bus bar that connects the rectifier 4 to the conductor roll 3 or the electrode 5, 8 and 8'is an earth roll, 9 and 9'is an ammeter, 10 is a rectifier switching commander, 11 is a control device, and 12 is a steel strip. It is a drive roll device. The earth rolls 8 and 8'rotatably contact the steel strip 1 before and after the plating tank 2 and the earth rolls 8 and 8 '
The ground current, which is grounded via the, can be measured by the ammeters 9 and 9 '. The ground rolls are provided before and after the plating tank 2 because when the number of rectifiers is large and the length of the entire plating tank is long, the ground resistance value through the steel strip for the length of the plating tank is large. And, the backup is taken into consideration when the grounding failure of the grounding roll itself occurs.

This line has a rated capacity of DC 40V, 150
There are 18 00A rectifiers on each side of the steel strip, 36 on both sides. The basis weight of zinc is 40 g / m ² per side, plate width
Assuming a line speed of 1 m and a line speed of 120 m / min, the total current calculated by equation (1) is about 262400 A, and about 14.6 kA per rectifier. However, if the upper and lower units are cut for measurement, the required current per unit is 15.4 kA, which exceeds the capacity of the rectifier. Therefore, the controller 11 instructs the steel strip drive roll unit 12 to set the line speed to 116 m / After lowering to about a minute, a rectifier switching command is issued from the insulation monitoring device 10 to sequentially switch the rectifier 4 and disconnect it from the line. At that time, the earth rolls 8 and 8 ′ arranged in front of and behind the plating tank 2 are removed. The flowing current value is measured by the ammeters 9 and 9 ', and when this current value exceeds the reference value, the insulation resistance value is calculated by the above-mentioned formula (3) that issues an alarm, and the insulation failure point is specified. When a larger current is detected, the controller 11 can be instructed to stop the line.

The normal earth roll current in this line is about 10 to 20 A at the most, but 1000 A or more sometimes flows when insulation failure occurs. Therefore, we adopted 500A as the criterion value for issuing an alarm, but this value must be empirically determined for each line. In addition to the current value itself, it is also effective to issue an alarm when the current value tends to increase, that is, when the numerical value increases with each measurement.

[0023]

According to the present invention, the insulation state of each rectifier circuit can be monitored during the operation of the line, and if an abnormality occurs, only that circuit is cut off and the operation is continued. You can also inspect and repair,
It has the excellent effect of preventing accidents such as fires and improving safety and productivity.

[Brief description of drawings]

FIG. 1 is a system diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram illustrating the concept of the present invention.

[Explanation of symbols]

 1 Steel strip 2 Plating tank 3 Conductor roll 4 Rectifier 5 Anode 6 Busbar 8 Earth roll 10 Insulation monitoring device 11 Control device 12 Steel strip drive roll device

Claims (1)

[Claims] 1. In a continuous electrical treatment facility for metal strips using n rectifiers as a power source, an earth roll can be rotated in contact with the metal strips so that the ground current can be continuously measured. Line speed of continuous electric processing equipment (n-
1) A metal strip material that is set to a speed that can be covered by a single rectifier, and that the circuit for each rectifier is sequentially disconnected from the line and opened to measure the ground current to determine the ground resistance of each rectifier. In-line insulation monitoring method for continuous electrical processing equipment in Japan.