CN106410869A - Induction power supply, with lightning-protection ground wires, of high tension transmission line - Google Patents

Abstract

The invention discloses a high-voltage transmission line lightning protection ground wire induction power supply. The induction power supply extracts electric energy from a transmission wire through an overhead ground wire network, and provides continuous and stable energy supply for transmission line monitoring equipment after power conversion. It is characterized in that the primary end of the power-taking transformer is connected in series to the overhead ground wire network, and the induction circulation formed by the space-closed plane composed of two lightning protection ground wires and iron towers is used to take power; A decoupling coil makes the induction power supply not affect the line lightning protection performance and zero-sequence protection performance; the invention reduces the dependence of the power supply system on energy storage equipment, prolongs the maintenance period and reliable working time of the power supply system.

Description

A Lightning Protection Ground Wire Inductive Power Supply for High Voltage Transmission Lines

technical field

The invention relates to the field of inductive power supplies, in particular to a lightning protection ground wire inductive power supply for high-voltage transmission lines.

Background technique

With the national requirements for smart grid construction and condition-based maintenance of power equipment, transmission line online monitoring technology has made great progress in recent years. Especially after the large-scale ice disaster occurred across the country in 2008, relevant management departments have increased the intensity of intelligent transformation of transmission line status monitoring.

By the end of 2014, about 100,000 sets of on-line monitoring devices for domestic transmission lines had been installed. While these devices provide effective technical support for equipment condition maintenance of transmission lines, many problems have also been exposed. According to the statistics of China Electric Power Research Institute, only 20% of the transmission line online monitoring devices installed within the scope of the State Grid can operate normally.

Among the faulty equipment, most of them are caused by power failure. At present, the power supply mode adopted by the transmission line online monitoring device is "photovoltaic panel + battery". The acquisition of light energy is greatly affected by the environment. In weather with insufficient light such as rain, snow, and heavy fog, the power generated by photovoltaic panels cannot meet the needs of normal operation of the equipment. No more than 5 hours. Therefore, a large-capacity battery has to be used to ensure that the battery provides working power for the monitoring equipment in rainy, snowy, foggy and other insufficiently illuminated weather. Judging from the lead-acid batteries and nickel-cadmium batteries commonly used in the on-line monitoring equipment of transmission lines, the average service life of the batteries is less than one year. The reasons mainly include the following aspects:

1. High-current charging of photovoltaic panels shortens battery life: Since solar power is intermittent, in order to ensure that the monitoring equipment can meet the working requirements of 7×24 hours in the case of insufficient light energy for a long time, the battery capacity used is very large. Large (100 ~ 200AH), in order to fully charge the battery in a short time, it is generally charged with a high current, and frequent high current charging will cause the battery life to decline.

2. Prolonged rainy weather may cause the charging controller to fail to start: all charging controllers are powered by batteries at present. When the battery voltage is lower than 7V, the charging controller will stop working. If the board is covered with ice or snow and the light is insufficient, the power of the battery will be exhausted, and the charge controller will not be able to charge the battery even if the light is sufficient afterwards.

3. Dust reduces the efficiency of photovoltaic panels to take electricity: photovoltaic panels have been exposed to the wild for a long time, and the dust on the surface will become thicker and thicker, which will gradually reduce the electricity extraction efficiency of photovoltaic panels and cause the battery to be undercharged for a long time. Covered with ice, the problems mentioned in point 2 are more likely to occur.

Based on the above three reasons, it is difficult to ensure the long-term reliable operation of the monitoring device only by photovoltaic panels.

Contents of the invention

The technical problem solved by the invention is to provide a ground wire induction power supply, which extracts electric energy from a power transmission wire through an overhead ground wire network. As long as the right amount of current flows on the transmission line, energy can be harvested from overhead ground lines.

Technical scheme of the present invention is:

Provide a high-voltage transmission line lightning protection ground wire induction power supply, the induction power supply extracts electric energy from the transmission wire through the overhead ground wire network, and after power conversion, provides a continuous and stable energy supply for the transmission line monitoring equipment, which is characterized in that , the primary end of the power-taking transformer is connected in series to the overhead ground wire network, and the induction circulation formed by the spatially closed plane composed of two lightning protection ground wires and the iron tower is used for power taking.

Utilizing the ground wire insulation gap of the segmented grounded overhead ground wire network, the ground wire induction power supply is connected between the ground wire and the iron tower, so that a closed current path is formed between the tension tower, the ground wire, and the straight tower.

A decoupling coil is installed between the power supply and the ground wire, so that the induction power supply does not affect the line lightning protection performance and zero-sequence protection performance.

Both the input end and the output end of the induction power supply are equipped with overvoltage and overcurrent protection circuits.

The inductive power supply includes a power-taking transformer, an anti-surge current circuit, an input overvoltage protection circuit, a rectifying and filtering voltage stabilizing circuit, a monitoring circuit and a backup lithium battery circuit.

The anti-surge current circuit includes a TVS tube, and the input overvoltage protection circuit is completed by a bidirectional thyristor.

The input overvoltage protection circuit includes a varistor R20, an RC snubber circuit, a bidirectional diode D0, a bidirectional thyristor Q1, the two ends of the varistor R20, the two ends of the RC snubber circuit, and the cathode and anode ends of the thyristor Q1 Both are connected in parallel to the output terminal of the power-taking transformer. The RC snubber circuit is composed of resistors R0 and C0 connected in series. One end of the bidirectional diode D0 is connected to the series connection point of R0 and C0, and the other end is connected to the control terminal of the bidirectional thyristor Q1.

The rectification, filtering and voltage stabilizing circuit converts the AC power taken from the high-voltage transmission line into a DC output through full-bridge rectification, and outputs different DC voltages using a linear voltage regulator after filtering by a capacitor.

The beneficial effects of the present invention are: the present invention can continuously obtain energy from the lines with a certain load all the year round, which greatly reduces our demand for intermediate energy storage components. In the present invention, an energy storage component (such as a supercapacitor) with a longer service life and more convenient use but lower capacity than a storage battery can be selected as the energy buffer pool. Its status has changed from the main energy supply part to the power regulation part, and its role has also changed from the need for continuous discharge to instantaneous power regulation, thus greatly reducing the dependence of the power system on energy storage equipment, making the maintenance cycle of the power system from the current 6 From 12 months to more than 3 years, the reliable working time of the power supply has been greatly improved. In addition, due to the continuity of the power supply of the ground wire induction power supply, it can use a small output current when supplying external power. In this case, even if the battery is still used as the energy buffer pool at the back end, because it is continuously charged with a small current, the battery lifespan will be greatly increased.

Description of drawings

Figure 1 Schematic diagram of ground induction current;

Figure 2 is a schematic diagram of the principle of power extraction;

Figure 3 is a schematic diagram of the power system connected to the ground wire network;

Figure 4 schematic diagram of equipment on-site installation;

Figure 5 thyristor application circuit diagram;

Figure 6 rectifier filter voltage regulator circuit.

detailed description

As shown in Figure 1, according to Maxwell's principle, when an alternating current flows through a wire, an alternating magnetic field will be generated in space, and when the alternating magnetic field cuts a space-closed plane composed of two lightning protection ground wires and iron towers, it will be in this plane. An induced electromotive force is generated on the plane, and once the conductor of the plane forms a loop, an induced circulation current will be formed on the point-to-point plane.

According to the calculation example in "Design Manual of High-Voltage Power Transmission Lines in Electric Power Engineering (Second Edition)", for a 220kV line with a conductor current of 436A, a power loss of 376 watts will be generated on a 1-kilometer ground loop. Therefore, induced electricity on the ground has long been regarded as a negative effect of transmission lines.

The ground wire induction power supply series products convert the loss on the ground wire network into usable electric energy, which can provide continuous and stable energy supply for transmission line monitoring equipment.

Figure 2 shows the working principle of the induction power supply using a constant voltage source. The primary end of the power-taking transformer is connected in series to the overhead ground wire network. Since the primary end of the power supply has a large impedance, when the current flows, a voltage U is generated at the input port of the power supply. So according to Ohm's law:

P=U×I U: Power port voltage I: Current flowing through the primary of the power supply

power can be obtained. In practical application, the ground wire induction power supply is bridged between the ground wire and the iron tower by using the ground wire insulation gap of the segmented ground overhead ground wire network.

Attached Figure 3 is a schematic diagram of the power system connected to the ground wire network. As shown in Figure 3, the ground wire induction power supply is installed on the "straight line tower 2". In this segmented grounding section, the grounding point of the ground wire is on the "tension tower 1", and the overhead ground wires on other towers and the iron tower are connected through insulator strings with discharge gaps, so we can put the input of the power system One end is connected to the "ground wire 1", and the other end is connected to the "straight line tower 2". ", "Straight Line Tower 2", "Ground Wire 2" and "Tension Tower 1" form a closed path, and the induced current flows in this closed path. According to the principle in Figure 2, we can Connect the power supply in series to the ground network.

Attached Figure 4 is the main installation method of the ground wire induction power supply on the transmission line. An insulator with a discharge gap is installed between the overhead ground wire and the iron tower where the power supply is installed. It can be seen that there is a retreat between the power supply and the ground wire. coupling coil. When the lightning strikes the overhead ground wire, since the decoupling coil is equivalent to an inductance for the frequency of the lightning wave, the instantaneous blocking effect of the inductance will cause the discharge gap on the ground wire to discharge first. Therefore, the access of the ground wire power supply will not affect the original lightning protection discharge characteristics of the overhead ground wire.

At the same time, the zero-sequence protection of the line means that when the wires are short-circuited, a large current will be generated on the ground wire due to the unbalanced three-phase power transmission. When this large current is detected, the corresponding protection of the substation will protect and operate. As in the case of lightning starting, the instantaneous zero-sequence current change will cause a reverse electromotive force to appear in the decoupling coil between the ground wire and the power supply, preventing the current from flowing through the power supply equipment, so that the protection action still operates according to the circuit design requirements.

On the other hand, the front end of the power system has over-voltage and over-retention protection, and uses a transformer for isolation, so it has strong anti-interference ability. In addition, output over-voltage protection and output over-current short-circuit protection devices are also designed at the output end of the power supply. These measures are sufficient to ensure the stable operation of the back-end monitoring equipment.

In actual use, different configuration schemes can be adopted according to different site requirements:

1) Ground induction power supply + super capacitor (recommended solution)

Under this configuration scheme, the power supply of the monitoring system completely abandons the photovoltaic + battery system, completely

All are powered by HM5002 ground induction power supply, and its specific configuration is ground induction power supply + super capacitor. The applicable conditions are as follows:

The transmission line load is heavy, generally greater than 200-300 amperes;

The electricity load is not large and does not require continuous heating (average annual power consumption <10W);

The advantage of this solution is that the power supply is light in weight, has a long service life, does not need to replace the battery, and has low maintenance costs; the disadvantage is that only the "charge-discharge" intermittent working mode can be used when the line is under low load, and the energy storage capacity of the power supply itself is not high.

2) Ground induction power supply + battery

Under this configuration scheme, the power supply of the monitoring system does not use photovoltaic panels but adopts battery management

The system is powered by HM5002 ground wire induction power supply and battery energy storage. This solution is suitable for most application scenarios. Its advantage is that the battery has a strong energy storage capacity, and the battery can provide a longer continuous power supply capacity when the line load is insufficient, and can provide greater power to equipment with heating requirements for a longer period of time. This solution is very convenient for replacing the power supply of the existing online monitoring equipment. It only needs to remove the photovoltaic panel and then connect the ground wire to get the power supply. In this scheme, since the ground wire induction power supply is a sustainable power supply, the capacity of the required storage battery can be greatly reduced. Generally, it can be reduced from the existing 100-200AH to 20-30AH. The service life will be much longer than that of using photovoltaic panels alone. The applicable conditions are as follows:

The transmission line load is heavy, generally greater than 200-300 amperes;

The electricity load is not large, and continuous heating is not required (the annual average power consumption is <10W)

3) Ground induction power supply + photovoltaic panel + battery

Under this configuration scheme, the power supply of the monitoring system adopts photovoltaic panels and ground wire induction power supplies at the same time. The two complement each other and can meet most field applications.

When the transmission line is short-circuited instantaneously, a very high short-circuit current will be generated, and this short-circuit current will be coupled to the power-taking circuit through the current transformer, which will cause irreversible damage to the components in the circuit. This circuit design uses a TVS tube to prevent the impact of surge current.

The TVS tube is a transient voltage suppressor, and its characteristics are: the response speed is extremely fast (nsec level); the pulse peak current is from 0.52A to 544A; the breakdown voltage is from 6.8V to 550V, which is convenient for various voltages There is a distinction between bidirectional TVS and unidirectional TVS, and bidirectional TVS tubes are used on AC power lines.

Even if there is no instantaneous short circuit in the high-voltage transmission line, it is possible to work with a large current for a long time, so the voltage induced from the current transformer may exceed the maximum allowable input voltage of the voltage regulator circuit, so the overvoltage protection The main purpose of the circuit is to protect the follow-up voltage stabilizing chip, and the present invention mainly adopts a bidirectional thyristor to complete.

The bidirectional thyristor is developed on the basis of ordinary thyristors. It can not only replace two thyristors connected in parallel with reverse polarity, but also only needs one trigger circuit. It is an ideal AC switching device at present. Triacs can be turned on by applying a positive or negative gate signal. A triac can be turned on by a gate signal when a forward or reverse voltage is applied. In order to prevent spurious pulses from triggering the triac, causing uncontrolled conduction, resulting in unstable operation of the motor and increased noise, the circuit of the 4Q bidirectional thyristor always includes additional protection components. In a typical circuit, the RC snubber circuit is connected in parallel with the main triac. Between terminals, it is used to limit the rate of change of voltage. In some cases, a large-capacity inductor is required to limit the rate of change of current during switching. The snubber circuit components are chosen to limit the dVCOM/dt to a level ensuring that the triac is not triggered. Under this condition, choosing the largest R value and the smallest C value can minimize the possibility of damage caused by the discharge of the snubber capacitor. The specific application circuit is shown in Figure 5. D0 in the figure is a bidirectional diode. When the current on the transmission line is too large, the voltage at point C will continue to increase through the RC charging circuit. When it reaches the breakdown voltage of the bidirectional diode (about 37v), The thyristor is triggered and turned on to protect the subsequent voltage regulator chip, so that the input voltage of the voltage regulator chip is below 377v.

The rectifier circuit mainly converts the AC power taken from the high-voltage transmission line into a DC output. The present invention adopts the commonly used bridge rectification method to achieve the purpose of converting AC to DC, as shown in Figure 6. Because the current flowing through the bridge rectifier circuit may be very large, and the directional voltage it bears may also be relatively high. Therefore, three parameters should be paid attention to when selecting the rectifier bridge model: one is the maximum forward conduction current; the other is the reverse breakdown voltage; the third is the maximum power dissipation.

The filter circuit mainly adopts the method of capacitor filtering, and a large capacitor and a small capacitor are connected in parallel at the output end of the rectifier circuit. The large capacitor is used for filtering low frequencies, and the small capacitor is used for filtering high frequencies.

The voltage stabilization circuit mainly includes two-pole voltage stabilization: one is the front-end switching power supply voltage stabilization circuit, because the switching power supply has the characteristics of large input voltage range and high efficiency, so it is placed in the first stage of voltage stabilization; the other is linear voltage regulation, linear voltage regulation It is characterized by small ripple and stable output voltage. The switching power supply chip is LM2576. This series of regulators is a monolithic integrated circuit, which can provide various functions of a step-down switching regulator and can drive a 3A load. The linear switching power supply chip is LM1086. LM1086 is a typical low-dropout linear voltage regulator integrated circuit. The input and output voltage difference is as low as 1.5V, and the output current can reach 1.5A. LM1086 can provide a fixed output of 1.8V, 2.5V , 2.85V, 3.3V, 3.45V, 5V, also provides output adjustable regulator LM1076-adj.

The above-mentioned specific embodiments are only to illustrate the technical concept and application characteristics of the present invention, and its purpose is to allow engineering designers familiar with this field to understand the connotation and essence of the present invention and apply it, but it cannot limit the protection scope of the present invention. Therefore, any physical location during actual application is within the scope of protection of this patent. No matter how detailed the above description appears, the invention can be practiced in many ways. The details of the above-described control schemes can vary considerably in their implementation details, yet are still encompassed by the invention disclosed herein. All equivalent changes or modifications made according to the spirit of the present invention shall fall within the protection scope of the present invention.

Claims (8)

1. A high-voltage transmission line lightning protection ground wire induction power supply, the induction power supply extracts electric energy from the transmission wire through the overhead ground wire network, and after power conversion, provides a continuous and stable energy supply for the transmission line monitoring equipment, its characteristics That is, the primary end of the power-taking transformer is connected in series to the overhead ground wire network, and the induction circulation formed by the spatially closed plane composed of two lightning protection ground wires and iron towers is used to take power. 2. The lightning protection ground wire induction power supply for high-voltage transmission lines according to claim 1, characterized in that, the ground wire induction power supply is bridge-connected between the ground wire and the ground wire insulation gap of the segmented ground overhead ground wire network. Between the iron towers, a closed current path is formed between the tension tower, the ground wire, and the straight tower. 3. The lightning protection ground wire induction power supply for high-voltage transmission lines according to claim 2, characterized in that a decoupling coil is installed between the power supply and the ground wire, so that the induction power supply does not affect the line lightning protection performance and zero sequence protection performance. 4. The lightning protection ground wire induction power supply for high-voltage transmission lines according to claim 2 or 3, characterized in that both the input end and the output end of the induction power supply are equipped with overvoltage and overcurrent protection circuits. 5. The lightning protection ground wire induction power supply for high-voltage transmission lines according to claim 2 or 3, characterized in that the induction power supply includes a power-taking transformer, an anti-surge current circuit, an input overvoltage protection circuit, and rectification, filtering, and voltage stabilization circuit, monitoring circuit and backup lithium battery circuit. 6. The lightning protection ground wire induction power supply for high-voltage transmission lines according to claim 5, wherein the anti-surge current circuit includes a TVS tube, and the input overvoltage protection circuit is completed by a bidirectional thyristor. 7. The high-voltage transmission line lightning protection ground wire induction power supply according to claim 6, wherein the input overvoltage protection circuit includes a piezoresistor R20, an RC snubber circuit, a bidirectional diode D0, a bidirectional thyristor Q1, and the The two ends of the varistor R20, the two ends of the RC snubber circuit, the cathode and the anode of the thyristor Q1 are all connected in parallel to the output end of the power-taking transformer. The RC snubber circuit is composed of resistors R0 and C0 connected in series. The bidirectional diode One end of D0 is connected to the series connection point of R0 and C0, and the other end is connected to the control end of the bidirectional thyristor Q1. 8. The lightning protection ground wire induction power supply for high-voltage transmission lines according to claim 5, characterized in that, the rectification, filtering and voltage stabilization circuit converts the AC power removed from the high-voltage transmission line into a DC output through full-bridge rectification, After being filtered by a capacitor, a linear voltage regulator is used to output different DC voltages.