How to prevent electricity theft

How to prevent the electric meter from stealing electricity

As a special commodity, electric energy has the characteristics of simultaneous production and use and no physical visible characteristics. In order to avoid unnecessary losses in the circulation of electric energy, our power supply department must do a good job in all aspects of management, especially in the aspect of preventing electricity theft. According to many cases of electricity theft, electricity theft mostly starts with the metering device. Because the metering box is concealed and difficult to be discovered, it is necessary to be meticulous as an anti-electricity-stealing officer. The electric energy meter measured by the electric energy meter is determined by the product of the three elements of voltage, current, power factor and time. Therefore, changing any one of the three elements can make the electric energy meter rotate slowly, stop or even reverse.

First, the common way of stealing electricity from the meter

1.1 Change the current coil of the short-circuit metering device. Usually, the current coil is short-circuited with a wire inside or outside the electric energy meter. The more common practice is to use a wire or a parallel resistor to insert the input terminal and output terminal of the electric energy meter into the phase line to play the role of shunt. The wire is short-circuited, and the wire resistance is almost zero, most of the current will pass through the short-circuit wire, and the current coil of the electric energy meter has almost no current, causing the electric energy meter to stop; if the resistance is less than the resistance value of the current coil, the current The coil and the parallel resistor form a parallel circuit. According to the shunt principle of the parallel circuit, most of the current will pass through the parallel resistor, and only a small current will pass through the current coil. This method of stealing electricity is called undercurrent method stealing electricity.

1.2 Disconnect the voltage connection piece or connect a voltage divider resistor in series on the voltage coil. Disconnecting the voltage coil is to depressurize the voltage coil and cause the meter not to run. The common method is to loosen the voltage connection piece of the electric energy meter. This method does not need to open the meter seal. It is a lower-level electricity stealing method. The new ordinary electric meter has short-circuited the connection piece inside the electric meter. Second, open the meter cover and connect a resistor in series with the voltage coil. The resistor in series is covered with insulating tape or insulating sleeve (with concealment). The principle is to divide the voltage and share part of the voltage to At both ends of the resistor, the voltage at both ends of the voltage coil is reduced to achieve the purpose of reducing the amount of electricity. This method is also called under-voltage method stealing electricity.

1.3 Transfer the zero live wire to steal electricity. This method of stealing electricity is to connect the hot and neutral lines of the incoming line of the electric energy meter in advance. According to the internal circuit structure of the electric energy meter, the input and output of the zero line end are short-circuited with a joint chip. Therefore, the electricity thief can use the The self-set (or connected) neutral line uses electricity, and the electric energy meter stops running because there is no current loop in the opposite direction passing through the current coil of the electric energy meter. This method of stealing electricity must be equipped with an inversion control switch indoors, so that the neutral line of the electric energy meter and the self-set ground line (or another neutral line) can be freely controlled. However, the self-built ground wire will bring serious threat to the user’s safe electricity consumption.

1.4 Zero theft of electricity. This method of stealing electricity must disconnect and conceal the neutral line at the incoming line of the electric energy meter in advance. Similar to the power-stealing method, you need to connect or set up your own ground wire, and install a switch in the room. After disconnecting the input zero line of the meter, the current coil can still pass the current, but the voltage coil will lose voltage. When the electricity thief wants the meter to rotate and measure, the zero potential can be reversely connected from the output terminal of the zero line of the meter (that is, another zero line or a self-set ground line), the voltage coil can obtain the voltage, and the meter rotates. Second, connect a resistor in series on the wire that is reversely connected to zero potential, which is similar to the undervoltage method, and plays a role in reducing the amount of electricity. This method is also known as the zero-break method.

1.5 The specific method of replacing the counter gear is to replace the meter of the large-capacity electric energy meter with the meter of the small-capacity electric energy meter. The power is doubled. For example, replace the 10 (20) A 900r/kWh meter with a 5 (10) A 1800r/kWh meter. Since the current coil and voltage coil of the energy meter have not changed, the speed of the aluminum plate will remain unchanged. However, after the meter was replaced, the original 900 revolutions counted the actual electricity consumption per degree, and it turned into 1800 revolutions to count the actual electricity one degree, and the metered electricity was reduced by half compared with the actual electricity consumption. The main point of this method of stealing electricity is to use the same brand of energy meter to exchange the meter, otherwise the mechanical size cannot be matched. Using this method to steal electricity, the first step is to open the meter seal. But now the electricity meter seals used by the power supply department are all new seals, which have good anti-theft performance.

1.6 Stealing electricity by bypassing the metering device The electricity stealing by bypassing the metering device is mainly reflected in the private connection of the public line. When the electricity thief learns that there is an electricity check, he will forcefully tore the electricity stealing wire away in time, so that the electricity checking personnel cannot obtain evidence. Due to the high contact resistance of the privately connected wires of electricity thieves, coupled with the oxidation reaction with the air when exposed or the insulating tape is not tightly closed, the contact resistance further increases, and under the thermal effect of the current, flashovers, strand breaks or even disconnections will occur. . This type of electricity theft will bring serious threats to the safe operation of power lines.

2. Precautions for electricity consumption inspection

2.1 Before checking electricity theft, the production and operation status, load and electricity consumption of the inspected user should be checked If you encounter a sudden drop in power consumption, you should check and check carefully, and never let any clues go. When we want to inspect suspicious users, we must arrive at the installation site of the electric energy metering device as soon as possible, and conduct a surprise inspection to prevent it from damaging the electricity theft site.

2.2 During the inspection, it is necessary to carefully check whether the seal of the metering device is in good condition, whether the wiring of the metering device is correct, whether the operating condition is in line with the actual situation, whether there is overheating, poor contact, etc., special attention should be paid to the inspection of details . The author once discovered a case of electricity theft. The electricity thief used high-voltage metering to supply power. The 10KV metering box was connected to the meter box with a cable. The electricity thief short-circuited the current line cable with a short-circuit ring, and then wrapped it with the same color tape. Although this method of stealing electricity is simple, it is often more difficult to detect because of its delicate technique.

2.3 Pay attention to check whether the configuration of the metering equipment is consistent with the actual load of the user. If it is found to be inconsistent, it should be replaced in time. For example, when the primary current of the current transformer is between 20% and 120% of the rated current, the proportion of the excitation current is small, and the measurement is more accurate. When the current transformer works at more than 120% of the rated current, due to the saturation of the iron core, the excitation current is large, resulting in a serious negative error, and a lot of electricity is underestimated. When the current transformer works below 20% of the rated current, the phenomenon of “big horse-drawn trolley” occurs, and a large negative error occurs when it is below 5%.

2.4 Electricity inspectors should be patient when they go to the site for inspection. When we conduct electricity inspection, because the relevant personnel of the electricity supplier are required to be at the scene, especially the dedicated transformer users, we cannot arbitrarily cut off the power for inspection in the absence of the person in charge to avoid affecting the production. Therefore, when some electricity thieves evaded when they learned that we were going to check electricity, we had to wait patiently. , there is no evidence of electricity theft.

2.5 Pay attention to the procedures of electricity use inspection and do a good job in collecting evidence in each link. When the relevant personnel of the electricity thief are not there, you cannot enter the home of the electricity thief privately to check the electricity, so as to avoid electricity thieves. cause unnecessary misunderstanding. With the continuous progress of science and technology, the methods of stealing electricity are becoming more and more diversified and technical. Therefore, it is necessary to regularly conduct technical training and exchange of experience for electricity inspectors, and use inspectors to continuously improve their technical level, timely support and control the dynamics of electricity theft, and better combat, stop, and prevent illegal acts of electricity theft.

1 Theft of electricity by the meterPrinciple analysis

The purpose of electricity theft is to obtain electricity for free. Metering watt-hour meters do little or no metering. Therefore, we must start from the working principle of the watt-hour meter when we study electricity stealing. We know that the watt-hour meter uses the eddy current generated by the voltage and current coils on the aluminum plate to interact with the alternating magnetic flux to generate electromagnetic force, so that the aluminum plate rotates, and at the same time, a braking torque is introduced, so that the speed of the aluminum plate is proportional to the load power. , Through the axial gear transmission, the electric energy is measured by accumulating the number of revolutions of the turntable by the counter. Therefore, the main structure of the watt-hour meter is composed of a voltage coil, a current coil, a turntable, a rotating shaft, a braking magnet, a gear, and a meter. From the working principle of the watt-hour meter, changing the current, voltage, phase of the input watt-hour meter, changing the speed of the watt-hour meter, gear ratio, etc. can all achieve the purpose of stealing electricity. The following is an analysis of the commonly used electricity stealing methods in terms of changing the electrical parameters (current, voltage, phase) and mechanical parameters (speed, gear ratio) of the watt-hour meter.

2 The method of stealing electricity from the meterAnalysis

2.1 The method of changing the electrical parameters of the electricity meter

2.1.1 Short-circuit the current coil of the watt-hour meter

This method of crime is usually to short-circuit the current coil with a wire inside or outside the watt-hour meter. The two ends of the wires with needles are inserted into the input and output ends of the current coil respectively, so that the current flowing into the watt-hour meter is reduced. This method can slow down the speed of the watt-hour meter to achieve the purpose of stealing electricity. Many people think that this method can stop the watt-hour meter, but in fact it cannot, because the resistance of the current coil of the watt-hour meter is very small. After the external wire is short-circuited, the short-circuit wire can only divide part of the current flowing into the current coil. It will still turn, but the part of the load divided by the short-circuit wire is undercounted. Therefore, it is wrong to judge whether the user has stolen electricity by simply observing whether the watt-hour meter will be turned on for such a method of electricity stealing.

2.1.2 Connect a voltage divider resistor in series with the voltage coil or disconnect the voltage coil.

For a single-phase watt-hour meter, it is easy to disconnect the voltage link of the watt-hour meter, which will cause the meter to not turn, but it is easy to detect. If a resistor is connected in series to the voltage coil, the load end is directly connected, and the series resistor is covered with insulating tape or insulating sleeve, which can be very concealed. purpose of measurement.

2.1.3 Swap the neutral and live wires of the input watt-hour meter so that the neutral line flows into the current coil of the watt-hour meter.

This method of stealing electricity is to exchange the zero wire with the neighbor or take another ground wire to form a one-to-one-fire system when using electricity, so that the zero wire of the self-electricity meter is suspended, because the current coil is suspended. There is no current flowing, so the watt-hour meter will not turn. When the power supply department checks the electricity, restore the zero line of its own watt-hour meter, and the watt-hour meter measurement is normal. This method is easy to control the stealing and non-stealing of electricity indoors, and it is difficult for the power supply personnel to find out the truth. The key to stealing electricity is to swap the neutral and live wires flowing into the watt-hour meter.

2.1.4 Use auxiliary transformer.

When stealing electricity, the secondary output of the transformer is used to reverse the current coil of the watt-hour meter to reverse the watt-hour meter. There is no trace of this method. Electricity thieves only need to reverse the watt-hour meter and reduce a certain amount of electricity before the power supply department reads the meter every month. Of course, this requires a more professional level.

2.1.5 The load end is connected with a phase shifter to adjust the electrical angle of the current and voltage to reverse the watt-hour meter (valid for three-phase watt-hour meters).

2.2 Change the mechanical parameter method of the watt-hour meter

2.2.1 Drill a small hole at the top of the watt-hour meter, insert iron nails or other objects when stealing electricity, The turntable of the watt-hour meter is stuck or the counter-rotation torque is increased, so that the watt-hour meter is less measured.

2.2.2 Adjust the brake magnet to increase the braking torque and slow down the speed of the meter, so as to achieve the purpose of stealing electricity.

2.2.3 Adjusting the transmission gap between the axial gear and the counter gear

Tightening the gap will increase the transmission resistance, the turntable will be blocked, and the speed will be slowed down , if it is larger, the transmission between the axial gear and the counter gear will be poor. Although the turntable rotates normally, the counter gear will not rotate when it rotates, which will reduce the power output of the counter. The cleverness of this electricity stealing method is to use the working principle of the electricity meter to conceal the fact of electricity stealing in the form of manufacturing faults.

2.2.4 Replace the gear ratio of the counter, so that the electricity output by the watt-hour meter is doubled. This method is a power thief’s secret weapon.

The specific method is to replace the meter of the large-capacity meter with the meter of the small-capacity meter. The electricity measured by the replaced meter is higher than the actual electricity consumption. The amount is doubled. For example, replace the 10 (20) A 900 rpm/KWH meter with a 5 (10) A 1800 rpm/KWH meter. Since the current coil and voltage coil of the watt-hour meter have not changed, then the aluminum plate The rotation speed remains the same, but after the counter is replaced, the actual power consumption of the original 900 rpm is calculated as one degree, and it becomes a 1800 rpm to calculate one degree. The calculated electricity is less than half of the actual electricity consumption. The main point of this method of stealing electricity is to use the same manufacturer’s watt-hour meter to be able to exchange the meter, otherwise the mechanical size cannot be matched. At the same time to sacrifice a watt-hour meter as a price. Do not replace the power meter surface during operation, so the power supply personnel cannot identify it. This method of stealing electricity is the highest method of all the above methods of stealing electricity. Because the current and voltage coils have not changed, the turntable of the watt-hour meter rotates normally, but the gear ratio of the watt-hour meter is changed, and the electricity measured by the watt-hour meter does not correspond to the actual electricity consumption. The current method of calibrating the accuracy of the watt-hour meter revolution cannot detect its error, and even if the watt-hour meter is disassembled, it is difficult to see the flaw. So far, no articles have publicly disclosed this method of stealing electricity. This method of stealing electricity has strong concealment, and the calibrator cannot verify the nature of electricity stealing, which is the most harmful.

In addition to the above-mentioned various electricity stealing behaviors, there is another type of electricity stealing by collusion between the inside and outside. It is a great threat to power supply companies, and it is worthy of a high degree of emphasis by industry insiders.

For the electricity stealing method of changing the current and voltage of the input watt-hour meter or changing the current and voltage coils of the watt-hour meter, the power supply personnel only need to strengthen the visual inspection and verify the watt-hour meter of the suspected user. can find out the truth. For users who use the mechanical method to steal electricity, it is difficult to find out the truth because there is no obvious trace of electricity stealing. Few articles have disclosed the method of stealing electricity in this regard before, so the power supply personnel are reminded to take special precautions against such means of stealing electricity.

Combining the above various methods of stealing electricity, except for the two methods mentioned in 2.1.4 and 2.1.5, which do not require the use of the watt-hour meter, other methods require the use of the watt-hour meter, or even dismantle the watt-hour meter. Electricity theft can only be achieved by turning on the watt-hour meter, which makes electricity thieves study how to remove the lead seal of the watt-hour meter. In fact, it is not difficult to remove the lead seal of the existing watt-hour meter with a little brains: use a small flat-blade screwdriver or a needle to loosen the wider end of the lead seal, and then pull out the lead seal wire with force. When reassembling, use a needle of suitable size to expand the lead sealing hole, so that the originally drawn thread can be passed back from its original position. After installation, use smooth pliers or other tools on both sides to press slightly so that the wire cannot be pulled out. As long as the force is appropriate, the markings on the original lead cover will not be damaged, and no traces of being removed can be seen.

3. Electricity meter anti-stealing measures

By analyzing the above various electricity stealing methods, it can be seen that the electricity thieves are very clever and covert. On how to prevent the behavior of electricity stealing, the following countermeasures are put forward in a targeted manner:

3.1 Centrally install the watt-hour meter, and seal and lock the watt-hour meter screen cabinet, so that the users themselves Do not touch or adjust the watt-hour meter casually.

In view of the characteristics that most electricity stealing methods need to use the watt-hour meter, the power supply department can effectively eliminate various electricity stealing methods by using this method. Many places have already adopted this approach, but it is difficult to implement in rural areas, scattered housing and other places. However, the watt-hour meter should also be installed in a more obvious place, and should not be installed in the houses or walls of households using electricity, so as to avoid theft. At the same time, the power supply personnel should strengthen the inspection and replace the watt-hour meter for users who are suspected of stealing electricity.

3.2 Improve the lead seal design of the watt-hour meter.

In view of the characteristics that the current lead seal is easy to pry open and restore, it is recommended that the power supply department study the use of a sealing method that cannot be restored after the seal is pressed down.

3.3 Use a watt-hour meter with a non-reverse function.

In order to prevent electricity theft by reversing the watt-hour meter, a watt-hour meter with anti-reverse function should be installed. The single-phase watt-hour meters currently used do not have a back-stop function, and the manufacturer is required to install a back-stop device when ordering. For a three-phase three-wire or three-phase four-wire watt-hour meter, you should also purchase a watt-hour meter with a non-reverse function to prevent the use of reverse-phase current to steal electricity.

3.4 Use a watt-hour meter with anti-theft function.

Now many manufacturers have produced a new type of watt-hour meter with anti-reverse, anti-decoupling, anti-current short-circuit, and anti-one-line-one-ground. It has advanced functions such as record of electricity stealing time and alarm, which can effectively prevent electricity stealing from happening.