CN109521265B - A voltage and current combined digital electronic transformer - Google Patents

Abstract

The embodiment of the present invention discloses a voltage-current combined digital electronic mutual inductor, which relates to the technical field of electronic mutual inductors for power systems, and has a large dynamic measurement and linear measurement range. The voltage-current combined digital electronic mutual inductor comprises: a sensor module and a signal processing module; the sensor module comprises: a voltage sensor and a current sensor; the voltage sensor is used to measure the phase voltage signals of the three-phase high-voltage bus respectively and output them; the current sensor is used to measure the phase current signals on the three-phase high-voltage bus respectively and output them; the current sensor comprises three PCB closed Rogowski coils; the output voltage of the PCB Rogowski coil is proportional to the current differential of the measured current-carrying conductor; the PCB closed Rogowski coil is specifically: the printed conductors are evenly arranged on the PCB; the signal processing module is used to process the phase voltage signal and the phase current signal, convert them into digital signals, and output them.

Description

A voltage and current combined digital electronic transformer

Technical Field

The invention relates to the technical field of electronic mutual inductors for power systems, and in particular to a voltage-current combined digital electronic mutual inductor.

Background technique

Power transformer is an indispensable high-voltage equipment used for protection, monitoring and metering.

Power transformers, including voltage transformers and current transformers, are important equipment for measuring electric energy and obtaining electromechanical protection signals in power systems. Their accuracy and reliability are closely related to the safety and economy of power systems. However, traditional electromagnetic power transformers face some unresolved problems in the process of power grid development towards large capacity and ultra-high voltage, such as voltage transformers cannot be short-circuited, current transformers cannot be open-circuited, they are easy to saturate, have ferromagnetic resonance, are large in size, heavy in mass, and signal transmission is easily affected by interference.

The primary and secondary integrated distribution switchgear mainly adopts traditional electromagnetic current transformers and iron core electronic transformers. Although they can meet the current operation needs after long-term operation practice, with the increasingly complex grid structure, the continuous increase of system capacity, the increasing short-circuit current of the system, and the higher level of informatization and automation, the disadvantages of traditional electromagnetic current transformers are becoming more and more obvious.

The existing electronic voltage transformer uses resistor and capacitor voltage division. The level of the capacitor voltage transformer to withstand lightning impulse is limited by the capacitor withstand voltage rating, and it is impossible to guarantee that it will not be damaged when subjected to random lightning impulse. In comparison, the resistance voltage sensor is much stronger than the capacitor type in terms of its ability to withstand lightning impulse. However, the large-scale use of resistance voltage sensors will cause the resistance value of the distribution line to the ground to decrease, which will bring difficulties to the detection of the insulation resistance of the line to the ground.

Traditional electromagnetic current transformers have magnetic saturation. When a short circuit occurs in the system during operation, the transformer core will retain residual magnetism, and the core will be severely saturated, which will deteriorate the transient performance of the transformer and fail to correctly reflect the primary current, causing protection refusal or malfunction; narrow frequency response range, poor linearity; weak analog signal transmission, weak anti-interference ability; narrow dynamic measurement range, difficult to achieve large-range measurement; large size, heavy weight, large self-loss; secondary conversion is required with primary and secondary fusion computer systems, and there are matching problems; open circuit of the secondary winding will generate high voltage, causing equipment or personal damage. As an improvement of the traditional electromagnetic current transformer, the iron core coil type low-power electronic current transformer improves the saturation characteristics of the core and expands the measurement range, but it also has inherent problems of intimate transformers such as magnetic saturation.

Summary of the invention

In view of this, an embodiment of the present invention provides a voltage-current combined digital electronic transformer, which, compared with traditional electromagnetic voltage and current transformers, has no saturation problem and no ferromagnetic resonance phenomenon, and thus has a larger dynamic measurement and linear measurement range.

The present invention provides a voltage-current combined digital electronic mutual inductor, comprising: a sensor module, a signal processing module;

The sensor module includes: a voltage sensor and a current sensor;

The voltage sensor is used to measure the phase voltage signals of the three-phase high-voltage busbars respectively and output them;

The current sensor is used to measure the phase current signals on the three-phase high-voltage busbar respectively and output them; the current sensor includes three PCB closed Rogowski coils; the output voltage of the PCB Rogowski coil is proportional to the current differential of the measured current-carrying conductor; the PCB closed Rogowski coil is specifically: the printed conductors are evenly arranged on the PCB;

The signal processing module is used to process the phase voltage signal and the phase current signal, convert them into digital signals, and output them.

The electronic mutual inductor further comprises:

The electronic transformer housing is used to provide a supporting structure for the sensor module and the signal processing module. The electronic transformer housing is composed of high-voltage insulating material and is provided with an external signal interface.

The signal processing module includes: a voltage signal conditioning circuit, a current signal conditioning circuit, an analog-to-digital conversion circuit, a microcontroller circuit, and an isolated RS485 data communication interface;

The voltage signal conditioning circuit is used to adjust the phase voltage signal to within the measurable range of the analog-to-digital conversion circuit;

The current signal conditioning circuit is used to adjust the phase current signal to within the measurable range of the analog-to-digital conversion circuit;

The analog-to-digital conversion circuit is used to convert the adjusted phase voltage signal and the phase current signal into voltage and current digital signals;

The microcontroller circuit is used to output the voltage and current digital signals through the isolated RS485 data communication interface;

The isolated RS485 data communication interface is used to output the voltage and current digital signals.

The current conditioning circuit comprises:

an amplifier circuit, used for amplifying the phase current differential signal;

An integrating circuit converts the amplified phase current differential signal into a voltage signal corresponding to the current object being measured;

The voltage follower circuit is used to isolate the integrated signal.

The sensor module is specifically placed in a pole-mounted switch, a high-voltage busbar passes through the pole-mounted switch, and three-phase carrier fluids simultaneously pass through the sensor module.

The voltage sensor includes: a high-voltage thick film resistor R, a high-voltage ceramic capacitor C, and an isolated current transformer T;

The first end of the high-voltage ceramic capacitor C is connected to the high-voltage bus, the second end of the high-voltage ceramic capacitor C is connected to the first end of the high-voltage thick-film resistor R, and the second end of the high-voltage thick-film resistor R is connected to the first input end of the isolation type current transformer T; the second input end of the isolation type current transformer T is grounded, and the isolation type current transformer T outputs a current signal proportional to the voltage.

The three PCB closed Rogowski coils are arranged on the same PCB board respectively. The PCB is manufactured by a four-layer board process. The top and bottom layers of the PCB are respectively copper-clad as shielding, and the middle two layers of the PCB are used as wiring layers of the PCB closed Rogowski coil.

The PCB closed Rogowski coil is specifically as follows: each Rogowski coil comprises an input line, an output line, an upper winding, a lower winding and a return line, the input line and the output line are arranged in parallel on the two middle layers of the PCB, each group of the upper winding and the lower winding are connected through a through hole between the two layers, and adjacent winding groups are connected through oblique leads, all winding groups are wound around the center of the current-carrying conductor once, and then a full circle of winding is returned to the output line through the return line, completing a complete phase current Rogowski coil.

In the above embodiment, a PCB closed Rogowski coil is used as a current sensor. Compared with the traditional electromagnetic voltage and current transformer, it has no saturation problem and no ferromagnetic resonance phenomenon, and thus has a larger dynamic measurement and linear measurement range.

BRIEF DESCRIPTION OF THE DRAWINGS

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

FIG1 is a connection diagram of a digital electronic mutual inductor provided by the present invention;

FIG2 is a schematic diagram of the overall structure of a digital electronic mutual inductor provided by the present invention;

FIG3 is a structural block diagram of a sensor module of an electronic mutual inductor provided by the present invention;

FIG4 is a schematic diagram of the principle of a voltage sensor provided by the present invention;

FIG5 is an embodiment of a phase current PCB Rogowski coil provided by the present invention;

FIG6 is a schematic diagram of local details of the phase current PCB Rogowski coil winding provided by the present invention;

FIG7 is a structural block diagram of a signal processing module provided by the present invention;

FIG8 is an embodiment of a voltage sensor provided by the present invention installed in a housing structure;

FIG. 9 is an embodiment of the current sensor provided by the present invention installed in a housing structure.

Detailed ways

The embodiments of the present invention are described in detail below with reference to the accompanying drawings.

It should be clear that the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

Figure 1 is a connection diagram of a digital electronic mutual inductor provided by the present invention; Figure 2 is a schematic diagram of the overall structure of a digital electronic mutual inductor provided by the present invention; Figure 3 is a structural block diagram of a sensor module of an electronic mutual inductor provided by the present invention; Figure 4 is a schematic diagram of the principle of a voltage sensor provided by the present invention; Figure 5 is an embodiment of a phase current PCB Rogowski coil provided by the present invention; Figure 6 is a schematic diagram of the local details of the winding of a phase current PCB Rogowski coil provided by the present invention; Figure 7 is a structural block diagram of a signal processing module provided by the present invention; Figure 8 is an embodiment of a voltage sensor provided by the present invention installed in a housing structure; Figure 9 is an embodiment of a current sensor provided by the present invention installed in a housing structure. The following is a description in conjunction with each figure.

As shown in FIG1 , the present invention provides a voltage-current combined digital electronic transformer, including: a sensor module 11 and a signal processing module 12;

The sensor module 11 is specifically placed in a pole-mounted switch, a high-voltage busbar passes through the pole-mounted switch, and three-phase carrier fluids simultaneously pass through the sensor module.

The sensor module 11 includes: a voltage sensor 111 and a current sensor 112;

The voltage sensor is used for 111, respectively measuring the phase voltage signals of the three-phase high-voltage bus and outputting them; the voltage sensor 111 comprises: a high-voltage thick film resistor R 1111, a high-voltage ceramic capacitor C 1112, and an isolated current transformer T1113; the first end of the high-voltage ceramic capacitor C is connected to the high-voltage bus, the second end of the high-voltage ceramic capacitor C is connected to the first end of the high-voltage thick film resistor R, and the second end of the high-voltage thick film resistor R is connected to the first input end of the isolated current transformer T; the second input end of the isolated current transformer T is grounded, and the isolated current transformer T outputs a current signal proportional to the voltage.

The current sensor 112 is used to measure the phase current signal on the three-phase high-voltage busbar respectively and output it; the current sensor includes three PCB closed Rogowski coils; the output voltage of the PCB Rogowski coil is proportional to the current differential of the measured current-carrying conductor; the PCB closed Rogowski coil is specifically: the printed conductors are evenly arranged on the PCB; the three PCB closed Rogowski coils are arranged on the same PCB board respectively, the PCB is made by a four-layer board process, the top and bottom layers of the PCB are respectively copper-clad as shielding, and the middle two layers of the PCB are used as the wiring layers of the PCB closed Rogowski coil. The PCB closed Rogowski coil is specifically: each Rogowski coil includes an input line, an output line, an upper winding, a lower winding and a return line, the input line and the output line are parallelly routed in the middle two layers of the PCB, each group of the upper winding and the lower winding are connected through a through hole between the two layers, and the adjacent winding groups are connected by oblique leads, all the winding groups are wound around the center of the current-carrying conductor, and then the return line is wound through a full circle to return to the output line, completing a complete phase current Rogowski coil.

The signal processing module 12 is used to process the phase voltage signal and the phase current signal, convert them into digital signals, and output them.

The electronic mutual inductor further comprises:

The electronic transformer housing 13 is used to provide a support structure for the sensor module and the signal processing module. The electronic transformer housing is made of high-voltage insulating material and is provided with an external signal interface.

The signal processing module 12 includes: a voltage signal conditioning circuit 121, a current signal conditioning circuit 122, an analog-to-digital conversion circuit 123, a microcontroller circuit 124, and an isolated RS485 data communication interface 125;

The voltage signal conditioning circuit 121 is used to adjust the phase voltage signal to within the measurable range of the analog-to-digital conversion circuit;

The current signal conditioning circuit 122 is used to adjust the phase current signal to within the measurable range of the analog-to-digital conversion circuit; the current conditioning circuit 122 includes: an amplifier circuit 1221, used to amplify the phase current differential signal; an integration circuit 1222, used to convert the amplified phase current differential signal into a voltage signal corresponding to the current object being measured; a voltage follower circuit 1223, used to isolate the integrated signal to play a stabilizing buffering role.

The analog-to-digital conversion circuit 123 is used to convert the adjusted phase voltage signal and the phase current signal into voltage and current digital signals;

The microcontroller circuit 124 is used to transmit the voltage and current digital signals to the output through the isolated RS485 data communication interface;

The isolated RS485 data communication interface 125 is used to output the voltage and current digital signals.

In the above embodiment, a high-voltage thick film resistor and a high-voltage ceramic capacitor are used as voltage sensors, and a PCB closed Rogowski coil is used as a current sensor. Compared with traditional electromagnetic voltage and current transformers, there is no saturation problem and no ferromagnetic resonance phenomenon, and thus a larger dynamic measurement and linear measurement range is provided.

The present invention has the following beneficial effects:

1) Compared with traditional electromagnetic voltage and current transformers, there is no saturation problem and no ferromagnetic resonance phenomenon, so it has a larger dynamic measurement and linear measurement range;

2) It only collects signals from the power grid, absorbs almost no energy, and can work well with microcomputer protection, monitoring and control.

3) The present invention has the advantages of small size, light weight, high integration, wide transmission frequency band, no resonance, and data transmission signal will not be affected or interfered, and can meet the requirements of measurement and protection.

4) The present invention provides a digital electronic transformer for 10kV pole switches. The transformer is based on the principle of high-voltage ceramic capacitor thick film resistor voltage division measurement and Rogowski coil current measurement, and integrates voltage and current sensors, and outputs through signal conditioning digital sampling. The transformer overcomes the shortcomings of traditional power transformers, has the characteristics of small size, high precision, wide frequency band, no magnetic saturation phenomenon, etc., integrates measurement and protection functions, and reserves a communication interface with the host computer, which can be deeply integrated with the primary and secondary fusion system data to upload the status of the power grid.

Detailed embodiments of the present invention are described below.

The present invention provides a (for example: 10kV) voltage and current combined digital electronic transformer, which can be applied to a digital electronic transformer of a primary and secondary integrated power distribution switchgear, and specifically relates to the sensor composition, circuit composition and appearance structure of the digital electronic transformer.

The new digital electronic mutual inductor developed by the present invention connects the primary voltage signal of 10kV resistor-capacitor voltage division and the current signal mainly composed of Rogowski coil on the switch side. The high-voltage resistor, high-voltage capacitor and Rogowski coil are cast into one body. After conversion and sampling, they are transmitted downward to the back-end power distribution equipment in the form of data stream.

The present invention adopts a novel RC voltage divider and Rogowski coil as the main sensors of the mutual inductor, and respectively starts with the phase voltage and phase current measurement objects, improves and optimizes the form of the RC voltage divider and the PCB Rogowski coil. The output signal of the sensor is conditioned through an integrator, an amplifier, etc., and a digital signal is output by a microprocessor through an isolated RS485 communication interface through an analog-to-digital converter.

The digital electronic mutual inductor provided by the present invention comprises three parts: a sensor module, a signal processing module and an electronic mutual inductor housing.

The sensor module is composed of a voltage sensor and a current sensor. The voltage sensor is used to measure phase voltages of 5.7 kV and higher, and is composed of a high-voltage ceramic capacitor and a thick film resistor in series, and outputs a current signal proportional to the voltage through a small current isolation transformer; the current transformer is mainly used to measure phase current, and is composed of a PCB Rogowski coil, and the output voltage is proportional to the current differential of the measured current-carrying conductor, that is, the output voltage signal can reflect the size of the AC current in the measured conductor.

In the signal processing module, the signal input mainly consists of three-phase voltage signals and three-phase current signals from the sensor module. The signal processing module mainly includes a microprocessor circuit, a voltage signal conditioning circuit, a current signal conditioning circuit, an analog-to-digital conversion circuit, and an isolated RS485 data communication circuit. The signal processing module processes the voltage and current signals and finally converts them into digital signals and sends them to the primary and secondary fusion system computer. The digital signal has a strong anti-external electromagnetic interference characteristic, directly provides data for the distribution monitoring and protection device, and the main body is deeply integrated with the pole switch to become one.

The electronic mutual inductor housing provides a supporting structure for the sensor module and the signal processing module, has certain high-voltage insulation performance, and leaves an external signal interface.

The digital electronic mutual inductor provided by the present invention has a highly integrated measurement system and adopts a new type of sensor to collect voltage and current signals. It is different from the traditional electromagnetic electronic mutual inductor and overcomes various hidden dangers existing in previous technologies. It can adapt to the development needs of the current rapidly developing ultra-high voltage and large-capacity power system.

Fig. 2 is the overall structure diagram of the 10kV digital voltage and current combined electronic transformer provided by the present invention. The electronic transformer can replace the position of the traditional electromagnetic transformer (CT) and be placed in the pole switch. The 10kV high-voltage busbar passes through the switch, and the three-phase current carrier simultaneously passes through the sensor module. The voltage sensor converts the 5.7kV phase voltage into a small current signal corresponding to the voltage through the resistor-capacitor circuit and the small current transformer, and outputs it to the voltage conditioning circuit of the signal processing module; the current sensor samples the current signal on the high-voltage busbar through the new PCB Rogowski coil, and outputs it to the current conditioning circuit of the signal processing module. In the signal processing module, the current signal and voltage signal measured by the sensor module are adjusted to the acceptable measurement range of the analog-to-digital converter through their respective signal conditioning circuits, converted into digital signals through the analog-to-digital conversion circuit, and the current and voltage digital signals are sent to the FTU of the primary and secondary fusion equipment through the isolated RS485 data communication circuit, so as to realize the measurement and protection of the 10kV medium-voltage line status.

FIG3 shows the internal structure of the sensor module, which includes a voltage sensor and a current sensor.

Figure 4 is a schematic diagram of a voltage sensor in a sensor module provided by the present invention. In the figure, C represents a high-voltage ceramic capacitor; R represents a high-voltage thick film resistor; and T represents an isolated high-precision current transformer.

The technical route of the voltage transformer provided by the present invention has obvious advantages over the existing capacitor transformers and voltage transformers on the market. The present invention provides a method of connecting a high-voltage resistor in series with a high-voltage capacitor: the random lightning impulse voltage is borne by the high-voltage resistor, thereby improving the lightning impulse resistance of the voltage transformer provided by the present invention; the DC insulation detection voltage of the insulation resistance to the ground is borne by the high-voltage capacitor (currently, most megohmmeters are used to measure the insulation resistance of the circuit to the ground, and a DC voltage is applied to the line), thereby avoiding the potential impact of the product of the present invention on the ground insulation detection. To realize the technical route of the voltage transformer provided by the present invention, the selection of high-voltage capacitors and high-voltage resistors is very important. The present invention requires that the selected high-voltage ceramic capacitors and high-voltage resistors have good performance in terms of consistency, temperature drift value and withstand voltage.

The voltage sensor provided by the present invention measures the primary side rated 5.7kV phase voltage, and the maximum measured value is 200% of the rated value. The secondary side signal is processed by the voltage conditioning circuit and sampled by the analog-to-digital conversion circuit. From the perspective of equipment safety and stability, it is important to isolate the primary and secondary sides of the medium-voltage phase voltage transformer of this specification. The present invention provides a 2mA/2mA high-precision current transformer to isolate the primary and secondary side voltages, thereby preventing the secondary side equipment from being destructively affected by the primary side fault.

The phase current sensor uses Rogowski coil for current sampling. Rogowski coil is a coil formed by winding a wire evenly on a frame of non-magnetic material with uniform cross-section. Compared with the traditional electromagnetic current transformer, Rogowski coil has the characteristics of light weight, wide bandwidth, good linearity and no magnetic saturation phenomenon. It has been widely used in current measurement devices, but it has not yet been used in the primary and secondary fusion equipment of the power system. It is necessary to further adopt new Rogowski coils to adapt to the primary and secondary fusion equipment. When using a closed Rogowski coil to measure current, it is necessary to first pass the current-carrying conductor through the center of the closed Rogowski coil. When the AC current to be measured flows through the current-carrying conductor, the AC current to be measured will generate an alternating magnetic field around the current-carrying conductor. The magnetic lines of force are approximately a circle with the center of the current-carrying conductor as the center. The change of magnetic flux generated in the volume surrounded by the ring winding of the closed Rogowski coil can be converted by the closed Rogowski coil into a voltage signal proportional to the differential of the total magnetic flux of each turn. Later, a voltage signal proportional to the AC current can be obtained through an integral amplifier circuit.

The traditional wound closed Rogowski coil is usually wound manually or by a winding machine. It is difficult to make the coil evenly wound and the cross-section of each coil turn equal. It also has disadvantages such as easy wire breakage and increased error due to interlayer capacitance. It is difficult to ensure parameter consistency in industrial production, which affects the characteristics of the Rogowski coil when measuring current. In order to overcome the shortcomings of the traditional closed Rogowski coil, a new type of closed Rogowski coil made of PCB, referred to as PCB closed Rogowski coil, is used to evenly arrange the printed wires on the PCB. When measuring current, the annular winding not only picks up the magnetic field changes generated by the AC current to be measured, but also picks up other alternating interference magnetic fields in the space.

The phase current sensor provided by the present invention measures the 30A to 600A AC current of the pole switch. The three-phase AC phase difference is 120 degrees. It is necessary to measure the three-phase AC current simultaneously and have the function of resisting external magnetic field interference. Its design is shown in Figure 5. The three Rogowski coils are arranged on a PCB board at the same time without any connection with each other. In order to meet the requirements of resisting external magnetic fields, the entire PCB is made of a 4-layer 3mm board process, in which the top and bottom layers are respectively coated with large areas of copper as shielding, and the middle 2 layers are used as the wiring layer of the Rogowski coil, so as to shield the external electromagnetic field interference.

As shown in Figure 6, a partial view of the coil that is resistant to external magnetic field interference, each Rogowski coil consists of an input line, an output line, an upper winding, a lower winding and a return line. The input line and the output line are parallelly routed on the two middle layers of the PCB. Each group of upper windings and lower windings are connected through a through-hole between the two layers. Adjacent winding groups are connected by oblique leads. All winding groups are wound around the center of the current-carrying conductor for one circle, and then the return line is wound around a full circle to return to the output line, completing a complete phase current Rogowski coil.

FIG7 is a signal processing module provided by the present invention. The function of this module is to perform analog-to-digital conversion on the data collected by the above-mentioned sensor module, and the microcontroller sends the current and voltage signals to the receiving end (such as FTU and other equipment). The signal source of this module is the output of the sensor module. S1 represents the signals at both ends of CT+ and CT- in the voltage sensor principle circuit diagram 3, including A, B, and C three-phase voltage signals; S2 represents the Rogowski coil phase current output signal, including A, B, and C three-phase current signals.

The voltage conditioning circuit (i.e., IV conversion circuit) provided by the present invention is shown in FIG6. As described above, the input signal S1 of FIG7 is connected to the output signal of FIG3, and the high-precision small current transformer in FIG3 is regarded as a constant current source. The voltage conditioning circuit can use a high-precision sampling resistor R with a suitable resistance value to realize IV conversion, and then transmit the converted voltage signal to the next-level analog-to-digital conversion circuit.

The current conditioning circuit provided by the present invention. The phase current signals on S2 are respectively amplified, integrated and voltage followed. Signal amplification is to adjust the output signal of the Rogowski coil to the sampling range of the analog-to-digital conversion circuit. The Rogowski coil outputs a micro-voltage signal of the measured current, so in the signal conditioning process, the micro-voltage signal needs to be converted into a suitable voltage signal, and integrated to restore the real current information. In order to improve the stability of the sampling signal, the integrated signal is isolated by a voltage follower circuit to play a buffering role.

After the output signal of the sensor module passes through the voltage/current conditioning circuit, the analog signal is converted into a digital signal by the analog-to-digital conversion circuit, in which the main component is the AD conversion chip. The digital electronic mutual inductor proposed in the present invention reaches the 0.2P level in terms of accuracy, so it is difficult to meet the standard requirements in terms of accuracy using the AD conversion integrated inside the microcontroller. The electronic mutual inductor of the present invention selects an analog-to-digital conversion chip with a sampling channel number of not less than 11, a sampling frequency of not less than 1MHz, and a high resolution (≥16 bits) to sample the voltage and current signals, and sends the sampling results to the microcontroller. After receiving the data, the microcontroller calculates the original data through the correction parameters (the correction parameters are calibrated by the test equipment and stored in the non-volatile memory), and outputs it to the outside through the isolated RS485 communication interface, thereby serving other devices on the primary and secondary fusion equipment system.

The layout of the voltage sensor side of the shell structure in the embodiment of the present invention is shown in Figure 8. According to the voltage sensor measurement principle in Figure 4, the layout of the phase voltage sensor example is shown in Figure 8. First, the lead is drawn from the high-voltage bus to the high-voltage end of the high-voltage capacitor, and then the low-voltage end of the capacitor is introduced into the high-voltage end of the high-voltage resistor, and then the low-voltage end of the high-voltage resistor is introduced into the primary side of the current transformer on the isolation circuit board to connect to the ground wire to form a high-voltage measurement loop, and then the corresponding current signal is output by the secondary side of the current transformer to the corresponding input of the signal processing module. In the embodiment of the present invention, the sensors of the three-phase voltage are all arranged on one side of the shell to measure the high-voltage bus voltages of phases A, B, and C respectively.

The layout of the current sensor side of the housing structure in the embodiment of the present invention is shown in Figure 9. The current sensor is a PCB Rogowski coil, and its specific embodiment is shown in Figure 5. It is arranged on the other side of the voltage sensor, and the three-phase high-voltage busbar passes through the centers of the three holes of the structure respectively, and the three-phase current signal is directly sent to the corresponding input of the signal processing module through the docking interface.

As the integration of primary and secondary power distribution networks of the State Grid Corporation of China advances, the original electromagnetic transformer technology is increasingly unable to meet the requirements of distribution network management. More and more people realize that it is an inevitable trend to adopt electronic transformers in the future power distribution field.

Compared with the original electromagnetic electronic mutual inductor, the electronic mutual inductor involved in the present invention has the following characteristics:

(1) The electronic mutual inductor involved in the present invention does not contain an iron core, thereby eliminating problems such as magnetic saturation and ferromagnetic resonance.

(2) Large dynamic range, high measurement accuracy, and wide frequency response range. It can meet the needs of measurement and relay protection at the same time.

(3) The primary and secondary sides are completely electrically isolated, there is no danger of open circuit high voltage on the low voltage side, it is highly safe and has excellent insulation performance.

(4) Strong anti-interference ability in data transmission. Due to the use of local digitization function of measured data, the anti-interference ability in the data transmission process is greatly increased compared with electromagnetic electronic mutual inductors.

(5) Small size, light weight and low cost. Its weight is much smaller than that of electromagnetic electronic transformers of the same voltage level, with simple structure and lower cost, and it can achieve deep integration with various forms of distribution networks.

(6) The electronic transformer uses a high-voltage resistor and a high-voltage capacitor in series to form a high-voltage arm. By sampling the high voltage on the primary side, a small current corresponding to the high voltage is formed, and the sampling is performed through current transformer isolation. This is different from the existing resistance-dividing and capacitance-dividing electronic voltage transformers.

(7) The electronic mutual inductor uses PCB Rogowski coils to collect phase currents and integrates three-phase current sampling on a PCB board. The top and bottom copper grounds are used to shield the electromagnetic field of the winding layers of the middle two layers of Rogowski coils. Return lines are set for each phase of the Rogowski coil winding group and the tinning process on the edge of the PCB board is used to further shield the surrounding electromagnetic field.

(8) The voltage conditioning circuit in the signal processing module uses IV conversion to convert the voltage signal (current) collected by the three voltage sensors into a voltage signal corresponding to the voltage object being measured, and then adjusts it to the measurable range of the analog-to-digital converter through an amplifier.

(9) The phase current signal collected by the Rogowski coil is a differential voltage signal corresponding to the change in the measured current. The current conditioning circuit in the signal processing module uses the amplifier circuit to condition the signal to a range that can be measured by the digital-to-analog converter, and then converts it into a voltage signal corresponding to the measured current object through an integrator. The subsequent voltage follower circuit buffers and isolates the signal, which can be sampled by the analog-to-digital conversion circuit.

(10) The microprocessor in the signal processing circuit converts the three-phase voltage and three-phase current into digital signals through the analog-to-digital conversion module, and uses the RS485 serial port isolation circuit to send the digital signals to the pole-mounted switch computer system. Different from the analog signal transmission of traditional electromagnetic electronic transformers, it has a more reliable signal transmission path and signal integrity.

The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any changes or substitutions that can be easily thought of by a person skilled in the art within the technical scope disclosed by the present invention should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.

Claims (1)

1. A voltage and current combined digital electronic transformer, characterized by comprising: a sensor module and a signal processing module; The sensor module includes: a voltage sensor and a current sensor; The sensor module is specifically: placed in a pole switch, a high-voltage busbar passes through the pole switch, and three-phase current carriers simultaneously pass through the sensor module; The voltage sensor is used to measure the phase voltage signals of the three-phase high-voltage busbars respectively and output them; Wherein, the voltage sensor comprises: a high-voltage thick film resistor R, a high-voltage ceramic capacitor C and an isolated current transformer T; The first end of the high-voltage ceramic capacitor C is connected to the high-voltage bus, the second end of the high-voltage ceramic capacitor C is connected to the first end of the high-voltage thick film resistor R, and the second end of the high-voltage thick film resistor R is connected to the first input end of the isolation type current transformer T; the second input end of the isolation type current transformer T is grounded, and the isolation type current transformer T outputs a current signal proportional to the voltage; The current sensor is used to measure the phase current signals on the three-phase high-voltage busbar respectively and output them; the current sensor includes three PCB closed Rogowski coils; the output voltage of the PCB closed Rogowski coil is proportional to the current differential of the measured current-carrying conductor; the PCB closed Rogowski coil is specifically: the printed conductors are evenly arranged on the PCB; The three PCB closed Rogowski coils are arranged on the same PCB board respectively. The PCB is manufactured by a four-layer board process. The top and bottom layers of the PCB are respectively copper-clad as shielding, and the middle two layers of the PCB are used as wiring layers of the PCB closed Rogowski coil. Specifically, the PCB closed Rogowski coil comprises: each Rogowski coil comprises an input line, an output line, an upper winding line, a lower winding line and a return line, the input line and the output line are parallelly routed in the middle two layers of the PCB, each group of the upper winding line and the lower winding line are connected through a through hole between the two layers, and adjacent winding groups are connected through oblique leads, all winding groups are wound around the center of the current-carrying conductor, and then a full circle of winding turns is returned to the output line through the return line, completing a complete phase current Rogowski coil; The signal processing module is used to process the phase voltage signal and the phase current signal, convert them into digital signals, and output them; Wherein, the signal processing module includes: a voltage signal conditioning circuit, a current signal conditioning circuit, an analog-to-digital conversion circuit, a microcontroller circuit and an isolated RS485 data communication interface; Wherein, the voltage signal conditioning circuit is used to adjust the phase voltage signal to within the measurable range of the analog-to-digital conversion circuit; Wherein, the current signal conditioning circuit is used to adjust the phase current signal to within the measurable range of the analog-to-digital conversion circuit; Wherein, the current signal conditioning circuit comprises: an amplifier circuit, used for amplifying a phase current differential signal; An integrating circuit converts the amplified phase current differential signal into a voltage signal corresponding to the current object being measured; A voltage follower circuit is used to isolate the integrated signal; Wherein, the analog-to-digital conversion circuit is used to convert the adjusted phase voltage signal and the phase current signal into voltage and current digital signals; Wherein, the microcontroller circuit is used to output the voltage and current digital signals through the isolated RS485 data communication interface; Wherein, the isolated RS485 data communication interface is used to output the voltage and current digital signals; The electronic transformer housing is used to provide a support structure for the sensor module and the signal processing module. The electronic transformer housing is made of high-voltage insulating material and is provided with an external signal interface.