DC power meter and transformer installation details

1. The connection process of the terminal block: The connecting parts of the DC power meter, the terminal block of the current transformer terminal, the fastening screw and the like are easily contacted when the moisture is corroded and loosened, and the contact resistance is increased.

2. Improper selection of secondary wire: The secondary wire connected to the DC power meter through the transformer should be a single-strand hard copper wire according to the requirements. However, although some people chose the copper wire, the soft copper wire was chosen for the convenience of wiring. In fact, the soft copper wire was used. Line under the pressure of the bolt at the junction is easy to produce broken strands, so that the effective cross-sectional area of ​​the wire becomes smaller, thereby increasing the loop resistance, resulting in increased measurement error; In addition, when using high-voltage measurement, the current transformer, voltage transformer The cross-sectional area and length of the secondary lead also have an effect, because the cross-sectional area of ​​the wire and the length of the wire are directly related to the loop resistance, if a single stranded hard copper wire has a small cross-sectional area or the wire length is too long. Will increase the loss, affect the measurement accuracy.

3, the secondary wire to obtain the voltage location did not take the appropriate measures: In the rural distribution transformer low voltage metering device voltage circuit, if for the convenience of the drawing voltage measurement directly from the transformer low voltage pillar nearest break T connection method, due to the general transformer low voltage outlet Aluminum conductors are used, but the metering voltage leads are copper conductors, which form a copper-aluminum connection. The operation time is long. An oxide film will be formed at the copper-aluminum connection, increasing the loop resistance, increasing the voltage loss and affecting the accuracy of metering.

4. Current transformer current ratio: The accuracy of the current transformer is related to the current it passes. The primary current is too large or too small. The output of the secondary current and the ratio of the primary current will increase the error.

In order to ensure measurement accuracy and reduce unnecessary power losses, in addition to the normal check of the meter and the transformer, the details of the impact measurement should also be incorporated into the measurement system to manage it. Strengthen the inspection of the connection terminal process, timely replace and deal with the corrosion terminal, the connection line should avoid the direct connection of the copper and aluminum wire, it is necessary to carry out tin treatment on the wire end; select the appropriate current ratio, make the current The primary current of the transformer should be about 30% to 120% of the actual load current during normal operation. It is best to reach about 60%; the secondary wire of the metering circuit should be single-stranded hard copper wire, and the cross-sectional area of ​​the secondary wire must meet the requirements in order to reduce the voltage loss and current loss on the wire. According to requirements, the measuring voltage lead adopts 2.5 square millimeters single stranded hard copper wire, the current lead is not less than 4 square millimeters single stranded hard copper wire; the length of the secondary loop wire connection process generally requires horizontal and vertical, as short as possible, and best The use of a hue phase line not only facilitates installation, reduces wiring errors, but also facilitates routine safety surveys and eliminates errors.

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