Check the secondary wiring of the high-voltage power metering box
So easy,teach you to check the secondary wiring of the high-voltage power metering box.
◆The first step: check the voltage loop and current loop
The high-voltage power metering box is basically used for power load metering in a three-phase neutral point ungrounded system, using a three-phase three-wire wiring method, as shown in the following figure:
Before analyzing the wiring, it is necessary to check whether the voltage circuit, the current is disconnected and there is no load. The way to confirm is to switch the multimeter to the voltage range. Corresponding to the 5 and 8 holes of the electric energy meter, whether the voltage is 100V, if there is about 57V or 173V, the transformer may have reverse polarity or disconnection; then change the phase voltammeter to the current range and clamp the current Clamp it on the inlet wire of the watt-hour meter 1 and 7 respectively, the current should meet 0.1A or more, and confirm whether the current of the inlet wire of the watt-hour meter 1, 7 is balanced.
◆Step 2: Find phase b:
In this connection:
① Uab= Ucb= Uac=100V
② Ua, Uc voltage to ground=100V
③ Ub voltage to ground=0V
Therefore, you can use the voltage range of the [multimeter] to confirm phase b; the way to confirm is to change the multimeter to the voltage range. The (black pen) of the multimeter is opposite to the ground, and the (red pen) corresponds to 2, 5, and 8 of the electric energy meter. If the voltage of that phase is "0", it is phase b.
◆Step 3: Determine the voltage phase sequence
As everyone knows, there are 6 kinds of phase sequence of three-phase three-wire electric energy meter:
① Normal phase sequence: abc, bca, cab
② Reverse phase sequence: cba, bca, acb
Therefore, you can use the function of [Phase Sequence Table] to confirm whether the phase sequence of the connected electric energy meter is positive or negative. The confirmation method is to connect the yellow, green and red of the phase sequence table to the 2, 5, and 8 holes of the electric energy meter respectively, and observe Turntable or sound. Confirm the true phase sequence based on the result. For example: the measured voltage of the electric energy meter 5 holes to the ground is 0, and the phase sequence meter measures the phase sequence of the electric energy meter to be the reverse phase sequence, then it can be judged that the actual voltage connection of the electric energy meter is 2, 5, 8 corresponding to c, b, a;
Phase angle:
The phase angle of the three-phase three-phase electric energy meter is basically measured according to the angle between the current coil and the voltage coil of the independent element, that is, the first element measures the angle between U12^I1 and the second element measures U32^I2 The angle between.
Therefore, you can use the function of [Phase Voltammeter] to confirm the angle between the first element and the second element. The confirmation method is to switch the phase voltammeter to the phase range, and the red and black terminals of the voltage test terminal U1 are connected to electric energy. For holes 2 and 5 of the meter, clamp the current clamp I2 to the 1 hole wiring of the electric energy meter respectively, and measure the data and record it. Then connect the red and black of the voltage test terminal U1 to the 8 and 5 holes of the electric energy meter respectively, and clamp the current clamp I2 to the 7-hole wiring of the electric energy meter respectively, and the data is measured and recorded.
◆Step 4: Carry out vector analysis according to the nature of the load
For example, a certain load is perceptual;
The first step is measured: Uab= Ucb= Uac =100V; Ia= Ic =1A
The second step is measured: the voltage of the 8 holes of the electric energy meter to the ground is 0V
Measured in the third step: the voltage at holes 2, 5, and 8 of the electric energy meter is in reverse phase sequence
The fourth step is measured: U12^I1=2300, U32^I2=3100
Analytical method
① Draw the corresponding relationship diagram of U1, U2, U3 and Ua, Ub, Uc, (U1, U2, U3 correspond to the voltage of 2, 5, and 8 holes)
According to the analysis of the second and third steps;
U1, U2, U3
Ua, Uc, Ub
② Draw the reference vector diagram according to the phase sequence
