3 reasons for inaccurate measurement of multi-function power
Release time：2018-12-08 Times of browsing：
Multi-function smart power meters are widely used in industries, enterprises and buildings. They are mainly used to monitor the power parameters of power grids and equipment, and provide reliable evidence for the normal operation, pre-judgment and maintenance of equipment. Therefore, the accuracy of the smart power meter measurement is the basis.
In general, the inaccurate measurement of digital power meter is like below:
1. Problem: Three-phase voltage, three-phase current, three-phase active power, power factor and display are functional, energy measurement is inaccurate.
Solution: If the above situation occurs, firstly check whether the inflow and outflow wiring of the three-phase current on the secondary side of the current transformer are reversed, because the current is connected from the transformer secondary side to the meter, and is divided into two ends, inflow and outflow.
2. Problem: Three-phase voltage, three-phase current and display is normally functioning. Three-phase active power, power factor, energy metering and display is abnormal.
Firstly check whether the inflow and outflow lines of the secondary current coming from the secondary side of the current transformer are reversed. If the current inflow and outflow are reversed, the energy is measured in EP-; if one or two phases are reversed , the active power will be offset, so the active power will be smaller, and the active elctric energy will be smaller too. At the same time, check whether the wiring phase sequence of the current transformer is misaligned. For example, the secondary side line of the phase A current transformer is connected to the Ib port of the meter, or the line of the secondary side of the phase B current transformer is connected to the Ic port of the meter and so on. Also check whether the wiring of the three-phase voltage UA UB UC UN is correct, for example, the line Ua is connected to the meter Ub, the line Ub is connected to the meter Uc, and so on.
If there is any wrong connection, the active power display will be inaccurate, so the energy metering will be inaccurate.
Normally, if the electric energy value is smaller, it means the active power is small. The reason for the smaller active power is that the CT ratio in the multi-function power meter is smaller than the set value. The current transformer model doesn't match the CT ratio set in meter menu.
At the same time, the wiring of the current or voltage is wrong, and the inflow and outflow are reversed, which will cause the active power to be offset, so that the active power displayed is smaller than the actual value, resulting in a smaller electric energy measurement.
3. If the three-phase active power display is not normal, the energy metering must be abnormal, and the pulse output is abnormal, either.
Voltage ratio PT, PT is set to 1 when it is low voltage, if the instrument menu PT ratio isn't 1, it means the three-phase voltage display is inaccurate. When it is under high voltage 10/0.1KV, the PT voltage ratio needs to set to be 100. For CT current ratio, If the current transformer is 100/5A, the meter menu CT ratio is set to 20.
Typically, multi-function power meter current, voltage transformation ratio has been set up at the factory. The reason of energy metering incorrect appears is mostly because of wiring problems.
Therefore, the multi-function meter should be checked under power failure starus before it is officially used. After a period of use, a live check should be performed.
Common problem