Analysis of Common Field Faults in Three-Phase Energy Meter On-Site Calibration Instrument



Analysis of Common Field Faults in Three-Phase Energy Meter On-Site Calibration Instrument:

1. Common Faults

(1) Incorrect wiring of the device

(2) Fault in the energy meter

(3) Fault in the CT part

2. Experience-Based Judgment of the Three-Phase Energy Meter On-Site Calibration Instrument

(1) When the metering device is normal, the comprehensive error (including CT error, secondary wiring error, and meter error) is within ±3%.

(2) When the comprehensive error is between -10% and -3%, the possible causes are generally:

a. Inaccurate meter

b. Heavy load on CT secondary side

c. Negative error of CT

(3) When the comprehensive error exceeds 10%, the possible causes are:

a. Incorrect secondary wiring of CT

b. Incorrect CT ratio

c. Missing phase or wrong phase sequence

Generally, during on-site work, the comprehensive error can be measured first. If the comprehensive error is within ±3%, the system is basically fine. When the comprehensive error is large, separate checks of CT error, meter error, and line diagnosis can be performed.

3. Common Problems in Three-Phase Four-Wire Circuits with the Three-Phase Energy Meter On-Site Calibration Instrument

(1) Missing one phase

When a certain phase voltage or current is missing, it can be directly observed from the "Measurement Parameter 1" or "Vector Diagram" function items of the analyzer. The reason for the missing phase is generally a fault in one of the three components of the metering device or an open circuit in the wiring. Specific possible causes are as follows:

a. One phase of the voltage coil in the energy meter is open (coil open circuit, lightning strike, voltage hook not in contact with the screw)

b. A certain phase fuse in the primary side of the metering circuit is blown or has poor contact

c. A phase line in the voltage secondary circuit is open (fuse blown or poor contact)

d. The current coil of a certain phase in the meter or CT itself is open, or the CT secondary winding is open (coil burned out, poor contact at the meter terminal or secondary wiring terminal)

e. A certain phase current is open in the secondary current circuit

(2) Missing two phases in the three-phase energy meter on-site calibration instrument

The causes and situations are similar to those of missing one phase.

(3) One or several phases of current are reversed

Current reversal can be observed from the "Vector" function. For example, the situation shown in the figure above is that phase A current is reversed. After reversal, the angle should differ from the normal by 180°.

The causes of this phenomenon are:

a. K1 and K2 of phase A CT are reversed

b. The cable of phase A CT is threaded in the opposite direction

c. K1 and K2 on the CT do not match the actual markings

(4) Voltage and current phase mismatch