How to Determine if Electricity Theft Occurs by Using Live and Neutral Wires?
Three-phase meters mainly determine if electricity theft has occurred by checking for voltage loss, while single-phase meters mainly determine it by comparing the difference in current between the live and neutral wires. The principle of judgment is: during normal electricity use, at the same point in time, the current flowing through the live and neutral wires... The values should be the same.
Two factors can affect the analysis results:
1. The live wire and neutral wire currents are very small, causing the ratio to exceed the tolerance due to measurement error;
2. When the concentrator reads different values for the live wire and neutral wire currents remotely, in the DL/T645-2007 protocol, the live wire and neutral wire currents are two different data identifiers. For the same meter, the concentrator needs to read the live wire and neutral wire currents twice, with a time difference of a few seconds. If the user is starting an appliance (such as a microwave oven), the concentrator reads the live wire current before starting and the neutral wire current after starting, resulting in inconsistent values for the live wire and neutral wire currents.
Therefore, the analysis strategy for the current at four time points is as follows:
la represents the live wire current, In represents the neutral wire current. If Ia < In, and In ≥ 0.1, and the following conditions are met:
Condition 1: At least one data point satisfies Ia/In ≤ 0.5.
Condition 2: No data point satisfies Ia/In ≥ 0.8. Note: Condition one is that not all data points across the four time points can be analyzed. For example, at some points, both the live and neutral wire currents may be zero, which is normal. Therefore, at least one data point must satisfy condition one.
Condition two is based on the fact that electricity theft is a continuous process. When the live and neutral wire currents at one point are relatively close, it indicates that the user is not stealing electricity. Other anomalies may be due to differences in the time of data reading.
After meeting the above conditions, the following situations may occur:
1. The live wire is short-circuited at the meter terminals;
2. The meter cover is open, and the live wire is short-circuited inside the meter;
3. An additional live wire is connected, bypassing the electricity meter before entering the household;
4. The live wire enters the household from the electricity meter's neutral wire, and the user takes the nearest neutral wire;
5. The components in the live wire measurement circuit inside the meter are damaged;
6. Multiple users share a neutral wire (this is non-standard construction and needs rectification).
If Ia>In, and Ia≥0.1, and the following conditions are met:
Condition 1: At least one data point satisfies In/Ia≤0.5;
Condition 2: No data point satisfies In/Ia≥0.8.
The following situations may occur:
1. The components in the neutral wire measurement circuit inside the meter are damaged;
2. The user has a leakage current.
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