Analysis and treatment of problems in the use of electric energy meters

1. The master table and the sub-table are not matched

1. The performance of the problem

A dormitory community found that the total amount of electricity accumulated by its total meter and the amount of electricity accumulated by several sub-meters brought by it did not match, and there was a big difference.

2. Analysis and processing

This meter is a three-phase four-wire meter, and its accumulated power should be the sum of the accumulated power of several sub-meters brought by it, so it is the basis of the charging standard.

However, under normal load, I suddenly found that the accumulated power of this meter has dropped, which is very different from the accumulated data. From the appearance of the watch, no abnormality was found, and the rotation of the dial and the function of the meter were normal. Then check whether there is a virtual connection phenomenon in the wiring at the end of the meter, and no abnormal phenomenon is found, and the wiring method is correct. However, when one of the lines at the end of the active table (phase B voltage line), it was found that this line has a very soft section (the line uses single-strand plastic hard wire), and it is suspected that the internal metal part has been disconnected. After careful inspection, this phase circuit has been disconnected.

In this way, the accumulated electricity of this meter will be lost to 1/3 of the accumulated electricity in normal time. When the B-phase voltage circuit is open, the accumulated power of this table is only the sum of the power of A-phase and B-phase. Because the B-phase is disconnected from the voltage loop of this meter instead of the current loop, it does not affect the normal use of the loads carried by each submeter and each user.

According to the above analysis, the occurrence of this fault is very abnormal. Because the wires connected to the end of the general table are single-strand plastic hard wires, and the metal parts are thicker, it is generally not easy to disconnect from the inside. Therefore, after many investigations and understandings, it is fully proved that this fault is indeed caused by man. Because the cover of the watch is sealed with pliers and cannot be disassembled, the internal metal has to be broken with pliers, but the insulation skin is intact and difficult to be discovered by people, thus achieving the purpose of stealing electricity. This issue has been referred to the relevant departments for handling.

Second, the correct selection of the measurement data of the field energy meter

In recent years, people have paid more and more attention to the high accuracy measurement of on-site current, voltage, phase, power and energy meters. In order to achieve this goal, it is often necessary to repeatedly disconnect and wire the current transformer of a high-accuracy measuring instrument into the circuit, which is both unsafe and time-consuming. At the same time, as the number of tests continues to increase, it will cause the wiring screws of the junction box to slide, resulting in poor contact and even open the current loop, causing accidents. However, due to the opening of the current clamp-type current transformer, this will greatly reduce the magnetic permeability, and at the same time, it has a great correlation with the position, which greatly limits the improvement of the measurement accuracy and causes the measured data to be generated. Suspicious. In order to solve this problem and make full use of existing measuring instruments, the method is to first clarify the additional error generated by the clamp current transformer itself before measuring, and then subtract the additional error itself from the data measured in the field This is the actual measured result.

Generally, the on-site calibrator is divided into two steps during periodic calibration. One is to connect the voltage and current input terminals of the calibrator and the voltage and current output terminals of the calibration device through wires respectively, and then measure a set of data. The second is to use the connection method of the clamp current transformer. Under the same load point, the second set of data is measured. Finally, the second set of data is subtracted from the first set of data to be the additional error of the current clamp.

In this way, this problem is basically solved, and at the same time, the efficiency of on-site testing is greatly improved. In the past, when the time was measured on the test site table, the error was too large or even out of tolerance. The metrology tester blindly concluded that the table was unqualified or the performance was not good. In fact, otherwise, these test data are likely to be inappropriate with the test method and processing method. Relationship, this should never be forgotten.

3. The speed of the energy meter is unstable

Generally, the unstable speed of the electric energy meter is caused by mechanical failure. Such as:

1. When the upper and lower bearings of the energy meter increase the friction torque due to lack of oil, sometimes accompanied by the squeak of friction vibration noise, the rotation speed of the energy meter becomes slower.

Treatment method: Open the watch case and add a little oil to the upper and lower bearings to solve the problem. If the upper and lower bearings are damaged or the shaft tip is worn seriously, you can replace it with a new device.

2. Due to the long-term use of the energy meter or the poor quality of the brake magnet, the phenomenon of demagnetization is caused, the braking torque is reduced, and the dial speed becomes faster. Treatment method: magnetize the brake magnet or replace the magnet.

3. When there is debris or iron slag between the magnets, it will make the dial rotate faster and slower. Treatment method: clean up debris and correct the uneven dial.

The above phenomena are the main reasons for the unstable speed of the electric energy meter, but this cannot be generalized. The rotational speed of the energy meter is not only related to the reasons mentioned above, but also related to the nature of the load it carries. Taking the three-phase three-wire energy meter as an example, when its load is purely resistive (that is, when the power factor is 1.0 and the Φ angle is 0 °), its two sets of components will produce a rotating torque on the turntable. Its power calculation formula is: PZ = UABIAcos (Φ + 30 °) + UCBICcos (Φ-30 °) (where: PZ is the total power; Φ is the angle between the phase voltage and the phase current; (Φ + 30 °) and (Φ-30 °) are both the angle between the line voltage and the phase current].

When the load is inductive or capacitive (when the power factor is 0.5 and the Φ angle is 60 °), the power of one of the two sets of components is zero, so that its total power is half of the original total power, of course the speed It is slower than the speed when the load is purely resistive. Because the load of the line is constantly changing, the speed of the energy meter changes accordingly, but this is normal.

4. The two meters are used alternately, causing power loss

1. The performance of the problem

According to a dormitory electrician in a certain unit, a user judged according to his actual load and normal power consumption, and the accumulated power consumption of the household electricity meter suddenly dropped, and no abnormality was found after inspection.

2. Analysis and processing

According to the above, the relevant personnel decided to observe and analyze the scene. After a period of time, the relevant measurement personnel came to the site to observe the watch. The watch box was not locked. During the observation, it was suddenly found that the bottom number and the number of the watch and the original record were not correct. The tail cover is not sealed. Judging from this series of circumstances, the user may have replaced the watch. In order to prove whether this user has stolen electricity, it is decided to come again on the meter reading day. Sure enough, on the day of meter reading, this form changed its face again. Both the base and the number of the form matched the original record. Undoubtedly, this household used the alternate use of the two watches to steal electricity. That is, the new watch is used in the first half of the month, and the original watch is used in the second half of the month (the end of the month is the meter reading day). In this way, the accumulated power of the original meter is only 1/2 of the normal accumulated power.

This issue has been handed over to the relevant measurement department for processing.

Through the above analysis, the root cause of this problem is summarized, mainly due to poor management. Such as: no formal watch box, lead seal is not in place, and work is not serious. Therefore, measurement staff must attach great importance to ideology. Only by closely coordinating the management work and the measurement work can we effectively avoid such problems.

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