Long distance secondary current display is inaccurate
Thread Content
It is more than 200 meters from the power distribution room to the site, and the on-site ammeter shows incorrectly. The ammeter is 5A.
You'd better change the ammeter to a 1A one, which will reduce the voltage drop on the line and make it relatively accurate.
Is the line too thin? Also, is the digit 0 on the field table accurate? Is the watch itself inaccurate? This post was last edited by jessehjx on 2009-4-12 20:21 ]
At present, the long-distance transmission of 5A transformer and 5A meter is not accurate. This is a common problem. The wire designed by the design institute is 1.5, and the induced voltage of the control wire in the cable bridge is tens of V.
We have also encountered it on site. We found that the main reason is that the power cable and the control cable are worn in the same protective tube, or the control cable is unshielded and is subject to strong electric induction by the power cable. It is recommended to replace the control cable with a shielded layer as the on-site control or current signal cable. It is recommended that the on-site operation column separate the control and current signal cables (double protective tube)
The transformer is not powerful enough, the wires are not shielded and should be kept separate from the power cables.
5A transformer 5A meter long-distance transmission, I pulled it out alone, it is not accurate even 150 meters
Logically speaking, the current signal is farther away than the voltage signal. Look at the shielding.
1. The capacity of the transformer may be small. There are 2 solutions. Change the transformation ratio to 1A. Or replace it with a large-capacity transformer. 2. Power interference may exist. 3. The cable is too thin. In the project I did, 200 meters should be normal, but 4 control cable cores are used, that is, 2 * 2x1.5
Increase the capacity of the transformer. I have encountered this situation before. After increasing the capacity of the current transformer from 5 VA to 10 VA, OK! The display is normal!
Transformers have their own capacity and volt-ampere characteristics. If the line is too long, the impedance is large, so the error is large. Just increase the diameter of the line! Or replace the large-capacity transformer.
The current digital display meter can be used for remote transmission through communication, which can completely solve this problem.
It is recommended that you follow GB/T 7676-96 Selection Standards for Electrical Voltage and Ammeters to better solve the problem you mentioned!
How many specifications are there for current transformers? The ones I have seen before seem to be 5A.
How far can a 1A transformer transmit? How big is the line? If you bring a few 1A meters, it will show normal.
It is not easy to buy large-capacity transformers used in low-voltage equipment. We contacted the manufacturer directly and did not buy a 20VA one. We only bought a 3.75~10VA one, but it has the same volume and appearance as the 5VA one. We don’t know whether it is authentic or fake. Therefore, you need to use a 1A transformer or a current transmitter~~~
Increase the wire diameter, use 4 square meters or 2.5 square meters of shielded cable instead, and change the current transformer and ammeter to 1A.
There are two recommended methods for long-distance transmission, as mentioned before, one is to use communication protocol, and the other is to use a transmitter.
Two ways: 1. The transformer and current converter are replaced with 1A. 2. The capacity of the transformer is increased.