Cable type phase-zero sequence integrated three-phase sensor for ring main unit

Abstract

The utility model discloses a cable-type phase-zero sequence integrated three-phase sensor for a ring main unit, and the sensor comprises three phase sensors which are the same in structure and are integrated in phase and zero sequence, and the three phase sensors are respectively an A-phase sensor, a B-phase sensor and a C-phase sensor. Each sensor is used for measuring and outputting a voltage signal of a corresponding phase; and the zero-sequence circuit is connected with the A-phase sensor, the B-phase sensor and the C-phase sensor and is used for detecting and outputting a zero-sequence voltage signal. According to the utility model, voltage measurement, protection and zero sequence functions can be realized.

Description

Technical Field

[0001] The utility model relates to the field of electrical detection of power systems and sampling control of distribution network automation, and particularly relates to a cable-type phase-zero-sequence integrated three-phase sensor for a ring main unit. Background Technique

[0002] With the construction of smart grids, as an important device for distribution network sectioning, branching, demarcation, and connection, the ring main unit needs to have an adaptive integrated in-situ feeder automation function, short-circuit / ground fault detection, realize single-phase ground fault in-situ line selection, section positioning and isolation, and cooperate with the primary closing of the substation outgoing switch and the secondary closing of the outgoing switch. To ensure the stable and reliable electrical performance of the above devices, the voltage sensor for voltage measurement and protection signals should fully reflect the characteristics and requirements of "low loss, energy conservation and environmental protection, high efficiency, economy, stable and reliable performance, and miniaturization".

[0003] At present, traditional electromagnetic voltage transformers are mainly used in ring main units. Although traditional electromagnetic voltage transformers can meet the current operation needs through long-term operation practice, with the increasingly complex power grid structure, continuous increase in system capacity, and higher and higher levels of informatization and automation, the disadvantages of traditional electromagnetic voltage transformers are becoming more and more obvious. The disadvantages of traditional electromagnetic voltage transformers in the integrated application of the primary and secondary of ring main units are mainly reflected in the following aspects: there is a magnetic saturation phenomenon. When a short circuit occurs in the system during the operation of a traditional electromagnetic voltage transformer, the transformer will be burned out, causing equipment or personal injuries; the frequency response range is narrow, the linearity is poor, and the anti-interference ability is weak; the dynamic measurement range is narrow, and it is difficult to achieve large-range measurement; the volume is large, the weight is heavy, and the self-loss is high; when connected to relay protection and automation instruments, it needs to go through secondary conversion, and there are matching problems between devices; the consumption of resource-based materials is large, and the economy is poor.

[0004] Therefore, the space inside the traditional ring main unit is extremely small and it has a fully insulated structure, which is not conducive to directly installing traditional transformers. With the in-depth development of the distribution network automation transformation work, a large number of secondary devices are put into use. However, how to collect signals, measure, monitor, and protect them remains a thorny problem, and a special voltage transformer needs to be equipped, resulting in high costs and large floor areas; especially for the already put-into-operation ring main units, it is extremely difficult to add traditional transformer devices, and the cost is extremely high.

[0005] In addition, to achieve the measurement of line losses for each line in the distribution network, new requirements need to be put forward for the primary equipment voltage transformer to meet the requirements of measurement accuracy. With the rapid development of electronic technology, microcomputer-based relay protection devices have gradually occupied the dominant position. In relay protection and measurement, the energy flow and information flow in the control part are separated, so the monitoring equipment no longer requires a voltage transformer sampling with high power output. At the same time, due to the rapid development of the power industry and the more complex power grid situation, intelligent voltage transformers that improve the power factor and the power grid quality are widely used. Due to the particularity of the intelligent ring main unit, therefore, it is extremely urgent to develop a cable-type phase-zero-sequence integrated three-phase voltage sensor for the ring main unit to provide voltage acquisition signals for the distribution terminal RTU, which has functions such as voltage sampling, measurement, protection, zero-sequence and voltage measurement, and protection, and zero-sequence function. Summary of the Invention

[0006] The purpose of the present invention is to provide a cable-type phase-zero-sequence integrated three-phase sensor for a ring main unit, which can realize voltage measurement, protection and zero-sequence functions.

[0007] To solve the above technical problems, the present invention provides a cable-type phase-zero-sequence integrated three-phase sensor for a ring main unit, including:

[0008] Three phase sensors with the same structure and phase-zero-sequence integration, namely A-phase sensor, B-phase sensor, and C-phase sensor; each sensor is used to measure and output voltage signals of corresponding phases; and

[0009] A zero-sequence circuit, connected to the A-phase sensor, the B-phase sensor, and the C-phase sensor, for detecting and outputting zero-sequence voltage signals.

[0010] Furthermore, the phase sensor includes a cable head, an outer sleeve, an epoxy tube, a high-voltage resistor, a bushing, a low-voltage resistor, a secondary capacitor, an adjustable resistor, an isolation transformer, a base, and a four-core shielded wire;

[0011] The cable head is installed at one end of the outer sleeve;

[0012] The other end of the outer sleeve is connected to the bushing, and the outer sleeve and the bushing form a hollow cylindrical structure;

[0013] The epoxy tube is located on the inner side wall of the hollow cylindrical structure and is connected to the cable head;

[0014] The high-voltage resistor is located inside the hollow cylindrical structure, and one end is connected to the cable head, and the other end is connected to the low-voltage resistor and the secondary capacitor;

[0015] The end of the low-voltage resistor far from the high-voltage resistor is connected to the adjustable resistor;

[0016] One end of the adjustable resistor away from the low-voltage resistor is connected to the negative terminal of the isolation transformer and the secondary capacitor;

[0017] The base is connected to one end of the sleeve away from the outer sleeve;

[0018] The isolation transformer is connected to the four-core shielded wire, and both are located inside the base;

[0019] One end of the four-core shielded wire away from the isolation transformer extends outside the base.

[0020] Further, the phase sensor further includes a transient protection tube; one end of the transient protection tube is connected between the high-voltage resistor and the low-voltage resistor, and the other end is connected between the adjustable resistor and the isolation transformer.

[0021] Further, the material of the base includes: aluminum alloy material.

[0022] Further, the base is of a hollow structure and is communicated with the hollow cylindrical structure; the inside of the base and the hollow cylindrical structure is filled with a closed insulating material.

[0023] Further, the closed insulating material includes epoxy resin.

[0024] Further, the material of the outer sleeve includes silicone rubber material.

[0025] Further, the material of the sleeve includes semi-conductive silicone rubber material.

[0026] Further, the zero-sequence circuit includes an A-phase resistor, a B-phase resistor, a C-phase resistor, an A-phase overvoltage protection device, a B-phase overvoltage protection device, and a C-phase overvoltage protection device;

[0027] One ends of the A-phase resistor, the B-phase resistor, and the C-phase resistor are respectively connected to the A-phase sensor, the B-phase sensor, and the C-phase sensor;

[0028] The other ends of the A-phase resistor, the B-phase resistor, and the C-phase resistor are respectively connected to the A-phase overvoltage protection device, the B-phase overvoltage protection device, and the C-phase overvoltage protection device;

[0029] The A-phase overvoltage protection device is connected to the B-phase overvoltage protection device; the B-phase overvoltage protection device is connected to the C-phase overvoltage protection device.

[0030] Further, the A-phase overvoltage protection device includes an A-phase capacitor, an A-phase adjusting resistor, an A-phase mutual inductor, and an A-phase discharge coil; the B-phase overvoltage protection device includes a B-phase capacitor, a B-phase adjusting resistor, a B-phase mutual inductor, and a B-phase discharge coil; the C-phase overvoltage protection device includes a C-phase capacitor, a C-phase adjusting resistor, a C-phase mutual inductor, and a C-phase discharge coil;

[0031] Both ends of the A-phase capacitor are respectively connected to both ends of the A-phase adjusting resistor; one end of the A-phase adjusting resistor is connected to the A-phase resistor and the A-phase mutual inductor, the other end of the A-phase adjusting resistor is connected to the first end of the A-phase discharge coil and is grounded; the end of the A-phase mutual inductor away from the A-phase adjusting resistor is connected to the second end of the A-phase discharge coil; the third end of the A-phase discharge coil is connected to the fourth end of the B-phase discharge coil;

[0032] Both ends of the B-phase capacitor are respectively connected to both ends of the B-phase adjusting resistor; one end of the B-phase adjusting resistor is connected to the B-phase resistor and the B-phase mutual inductor, the other end of the B-phase adjusting resistor is connected to the first end of the B-phase discharge coil and is grounded; the end of the B-phase mutual inductor away from the B-phase adjusting resistor is connected to the second end of the B-phase discharge coil; the third end of the B-phase discharge coil is connected to the fourth end of the C-phase discharge coil;

[0033] Both ends of the C-phase capacitor are respectively connected to both ends of the C-phase adjusting resistor; one end of the C-phase adjusting resistor is connected to the C-phase resistor and the C-phase mutual inductor, the other end of the C-phase adjusting resistor is connected to the first end of the C-phase discharge coil and is grounded; the end of the C-phase mutual inductor away from the C-phase adjusting resistor is connected to the second end of the C-phase discharge coil.

[0034] By the above technical solution, the present utility model has the following beneficial effects:

[0035] Through three phase sensors with the same structure and integrated phase and zero sequence, namely the A-phase sensor, the B-phase sensor, and the C-phase sensor; each sensor is used to measure and output the voltage signal of the corresponding phase; and a zero sequence circuit, which is connected to the A-phase sensor, the B-phase sensor, and the C-phase sensor, is used to detect and output the zero sequence voltage signal. This device can realize voltage measurement, protection, and zero sequence functions.

[0036] In addition, the voltages of the A-phase sensor, B-phase sensor, and C-phase sensor of this device adopt high-precision columnar non-inductive thick-film resistors to output small voltage signals, and the temperature drift coefficient of this device is small. It can ensure that when this device works outdoors and within the temperature range of -40°C to +70°C, the error range of this device hardly changes, thus having strong anti-interference ability. By means of isolation transformation, dual-group output of small voltage signals is achieved, ensuring that the phase sequence and zero-sequence voltage small signals are output separately, without interfering with each other or affecting each other, and the measurement and protection signals work independently, ensuring the more reliable performance of this device.

[0037] Furthermore, the voltage part of this device samples through high-precision resistors. It can not only achieve zero-sequence, measurement, and protection functions, but after the integration of the two, it is integrally encapsulated and insulated with epoxy resin. The secondary wiring is connected through three four-core shielded wires, and the output signal can be connected in parallel to a six-core shielded paired twisted cable with a length of 15 meters and the accuracy at the end remains unchanged. This combined structure is convenient for installation, reduces on-site wiring, saves space, and is easy to maintain. In addition, since the output of this device is a small voltage signal, it can avoid damaging the controlled equipment and can be directly interfaced with secondary integrated automation equipment such as meters and relay protection devices, thereby realizing voltage measurement, protection, and zero-sequence functions. It not only has complete functions, is simple and convenient to install and use, reduces energy consumption during operation, but also does not require equipment maintenance. Brief Description of the Drawings

[0038] Figure 1 It is a schematic diagram of the overall structure of the cable-type phase-zero-sequence integrated three-phase sensor for a ring main unit cabinet in an embodiment of the present invention;

[0039] Figure 2 It is a circuit schematic diagram of the voltage sensor of the cable-type phase-zero-sequence integrated three-phase sensor for a ring main unit cabinet in an embodiment of the present invention.

[0040] In the figure, 1. Cable head; 2. Outer sleeve; 3. Epoxy tube; 4. Enclosed insulating material; 5. High-voltage resistor; 6. Bushing; 7. Low-voltage resistor; 8. Secondary capacitor; 9. Transient protection tube; 10. Adjustable resistor; 11. Isolation transformer; 12. Base; 13. Four-core shielded wire. Detailed Description of the Embodiment

[0041] The following will describe in more detail a cable-type phase-zero-sequence integrated three-phase sensor for a ring main unit cabinet of the present invention with reference to the drawings, which shows the preferred embodiments of the present invention. It should be understood that those skilled in the art can modify the present invention described herein while still achieving the advantageous effects of the present invention. Therefore, the following description should be understood as a broad guidance for those skilled in the art and not as a limitation to the present invention.

[0042] The present utility model will be described more specifically by way of example with reference to the accompanying drawings in the following paragraphs. According to the following description, the advantages and features of the present utility model will be clearer. It should be noted that the accompanying drawings are all in a very simplified form and use non-precise scales, only for the purpose of conveniently and clearly assisting in explaining the embodiments of the present utility model.

[0043] As Figure 1-2 shown, an embodiment of the present utility model provides a cable-type phase-zero integrated three-phase sensor for a ring main unit, including: three phase sensors with the same structure and phase-zero integration, namely an A-phase sensor, a B-phase sensor, and a C-phase sensor; each sensor is used to measure and output the voltage signal of the corresponding phase; and a zero-sequence circuit, connected to the A-phase sensor, the B-phase sensor, and the C-phase sensor, for detecting and outputting a zero-sequence voltage signal.

[0044] In a specific embodiment, the phase sensor includes a cable head 1, an outer sleeve 2, an epoxy tube 3, a high-voltage resistor 5, a bushing 6, a low-voltage resistor 7, a secondary capacitor 8, an adjustable resistor 10, an isolation transformer 11, a base 12, and a four-core shielded wire 13.

[0045] More specifically, the cable head 1 is installed at one end of the outer sleeve 2; the other end of the outer sleeve 2 is connected to the bushing 6, and the outer sleeve 2 and the bushing 6 form a hollow cylindrical structure; the epoxy tube 3 is located on the inner side wall of the hollow cylindrical structure and is connected to the cable head 1; the high-voltage resistor 5 is located inside the hollow cylindrical structure, and one end is connected to the cable head 1, and the other end is connected to the low-voltage resistor 7 and the secondary capacitor 8; the end of the low-voltage resistor 7 far from the high-voltage resistor 5 is connected to the adjustable resistor 10; the end of the adjustable resistor 10 far from the low-voltage resistor 7 is connected to the negative end of the isolation transformer 11 and the secondary capacitor 8; the base 12 is connected to the end of the bushing 6 far from the outer sleeve 2; the isolation transformer 11 and the four-core shielded wire 13 are connected and are both located inside the base 12; the end of the four-core shielded wire 13 far from the isolation transformer 11 extends outside the base 12.

[0046] Among them, by setting the secondary capacitor 8, the phase difference between the high-voltage resistor 5 and the low-voltage resistor 7 can be adjusted, so as to adjust the distributed capacitance inside the device, ensuring that the phase difference of the device is not interfered by the external electromagnetic field.

[0047] In this embodiment, the present embodiment outputs signals by using a four-core shielded wire 13 (i.e., a four-core paired shielded twisted pair), ensuring that the phase sequence of all voltages of the device and the zero-sequence paired signals are output simultaneously. There are a total of four signals for three phases, and their marks are: u1, u2, u0+, and u0-.

[0048] In one embodiment, the adjustable resistor 10 can adopt a potentiometer with the model number 3296W-502, which can adjust the ratio difference between the high-voltage resistor 5 and the low-voltage resistor 7 at any time, so that the device can meet the ratio difference requirements under different load conditions.

[0049] Preferably, the phase sensor further includes a transient protection tube 9; one end of the transient protection tube 9 is connected between the high-voltage resistor 5 and the low-voltage resistor 7, and the other end is connected between the adjustable resistor 10 and the isolation transformer 11.

[0050] In this embodiment, the material of the base 12 includes: aluminum alloy material. By providing a base 12 with a metal shell and grounding it, the surface zero potential can be touched, so it is safe and reliable.

[0051] Furthermore, the base 12 is a hollow structure and is connected to the hollow cylindrical structure; the inside of the base 12 and the hollow cylindrical structure is filled with a closed insulating material 4.

[0052] Among them, the closed insulating material 4 includes epoxy resin. This embodiment adopts a fully sealed technology, and the entire device is internally filled and integrally formed with epoxy resin, improving the overall safety.

[0053] Preferably, the material of the outer sleeve 2 includes silicone rubber material. It effectively isolates the internal components of the device from the external environment and protects the internal circuit from external electric field interference.

[0054] Preferably, the material of the bushing 6 includes semi-conductive silicone rubber material. By using silicone rubber as the outer insulating material, and the outer surface of the outer insulating material is coated with semi-conductive silicone rubber, not only the shielding effect is good, but also because the surface of this device is coated with semi-conductive silicone rubber and the base 12 with a metal shell, the surface zero potential of this device can be touched and it is safer and more reliable.

[0055] In this embodiment, the phase sequence and zero-sequence voltage acquisition signals of each phase are output through the isolation transformer 11. The zero-sequence voltage of each phase is connected in an open delta to form a three-phase zero-sequence voltage signal output. Each phase of this device uses a shielded twisted pair cable for the primary and secondary integration of distribution equipment, and uses a four-core paired shielded twisted pair to output signals. After the three phases are connected, the phase sequence and zero-sequence four pairs of signals of the voltages of the A-phase, B-phase, and C-phase circuits are output simultaneously. This embodiment integrates the functions of three-phase voltage measurement, protection, and zero-sequence through the intelligent combination of external lines. It is applied to the primary and secondary integration ring main unit of distribution equipment, thus realizing the function of deep primary and secondary integration. And the internal components of this device are arranged in an orderly manner and intelligently combined to avoid electromagnetic field interference, and six-way voltage small signals are output simultaneously without mutual interference. Therefore, the function of this device is stronger and the performance is more superior than that of three phase sequence voltage transformers plus three zero-sequence voltage transformers.

[0056] More specifically, this embodiment is based on the principle of resistor-capacitor voltage division. The high-voltage resistor 5 (such as a high-precision columnar non-inductive thick-film resistor) is used for voltage division to convert the high voltage into a low-voltage signal, and the phase sequence and zero-sequence voltage acquisition signals of each phase are output through the built-in phase-zero-sequence isolation transformer 11. The secondary capacitor 8 and the adjustable resistor 10 are used for phase difference adjustment and ratio difference adjustment to ensure the accuracy and stability of the signal. At the same time, this embodiment uses four-core paired shielded twisted-pair cables for signal output to ensure the anti-interference ability of the signal. In addition, this device adopts a fully sealed technology and is potted with epoxy resin, ensuring the miniaturization, stability, and reliability of this device, being applicable to harsh outdoor environments, and being able to realize the voltage measurement, protection, and zero-sequence functions of the distribution terminal RTU.

[0057] In this embodiment, the voltages in the circuits of the A-phase sensor, B-phase sensor, and C-phase sensor are divided by a high-precision columnar non-inductive thick-film resistor (i.e., the high-voltage resistor 5) to output small voltage signals, with a small temperature drift coefficient, so that when this device operates outdoors at -40°C to +70°C, the error range remains unchanged and the anti-interference ability is strong. In addition, this embodiment outputs small phase-sequence and zero-sequence voltage signals through the isolation transformer. The output is linear throughout the measurement range, ensuring that the small phase-sequence and zero-sequence voltage signals are output separately, without interfering with each other or affecting each other, so that the measurement and protection signals work independently.

[0058] Therefore, this embodiment adopts a non-traditional voltage sensor technology, making the voltage sensor in the form of a cable accessory. Without adding a new ring main unit cabinet, it can acquire signals, obtain measurement, monitoring, and protection without damaging the original cables and various cable accessories in the cabinet. This device obtains signals through the bus voltage method, and the phase-zero-sequence voltage sensor is built into the cable accessory to collect signals. It is applied to the primary-secondary integrated ring main unit cabinet of distribution equipment, meeting the development needs of "digitization, intelligentization, and networking" in various fields of the power industry.

[0059] In addition, this device can achieve the following operating performance:

[0060] 1. Ambient temperature: -40°C to +70°C.

[0061] 2. Altitude: not exceeding 1000m.

[0062] 3. There is no obvious dust, smoke, corrosive gas, steam, or salt and other contaminants in the ambient air.

[0063] 4. Relative humidity: The average relative humidity measured within 24 hours shall not exceed 95%.

[0064] 5. The voltage integrated sensor is allowed to operate continuously at 1.2 times the rated current and voltage.

[0065] In a specific embodiment, the zero-sequence circuit includes an A-phase resistor R1a, a B-phase resistor R1b, a C-phase resistor R1c, an A-phase overvoltage protection device TVa, a B-phase overvoltage protection device TVb, and a C-phase overvoltage protection device TVc.

[0066] Specifically, one end of the A-phase resistor R1a, B-phase resistor R1b, and C-phase resistor R1c are respectively connected to the A-phase sensor, B-phase sensor, and C-phase sensor; the other ends of the A-phase resistor R1a, B-phase resistor R1b, and C-phase resistor R1c are respectively connected to the A-phase overvoltage protection device TVa, B-phase overvoltage protection device TVb, and C-phase overvoltage protection device TVc; the A-phase overvoltage protection device TVa is connected to the B-phase overvoltage protection device TVb; the B-phase overvoltage protection device TVb is connected to the C-phase overvoltage protection device TVc.

[0067] In this embodiment, the primary high voltage is converted into a low voltage, and after processing, a secondary voltage that meets the standard is output. By setting the overvoltage protection device, once the B-phase resistor R1b is damaged, the increase in the secondary voltage can be limited to protect the measurement system.

[0068] In this embodiment, the A-phase overvoltage protection device TVa includes an A-phase capacitor Ca, an A-phase adjusting resistor R2a, an A-phase inductor La, and an A-phase discharge coil; the B-phase overvoltage protection device TVb includes a B-phase capacitor Cb, a B-phase adjusting resistor R2b, a B-phase inductor Lb, and a B-phase discharge coil; the C-phase overvoltage protection device TVc includes a C-phase capacitor Cc, a C-phase adjusting resistor R2c, a C-phase inductor Lc, and a C-phase discharge coil.

[0069] Specifically, both ends of the phase-A capacitor Ca are respectively connected to both ends of the phase-A regulating resistor R2a; one end of the phase-A regulating resistor R2a is connected to the phase-A resistor R1a and the phase-A inductor La, and the other end of the phase-A regulating resistor R2a is connected to the first end Xa of the phase-A discharge coil and grounded; the end of the phase-A inductor La far from the phase-A regulating resistor R2a is connected to the second end A of the phase-A discharge coil; the third end dna of the phase-A discharge coil is connected to the fourth end db of the phase-B discharge coil; both ends of the phase-B capacitor Cb are respectively connected to both ends of the phase-B regulating resistor R2b; one end of the phase-B regulating resistor R2b is connected to the phase-B resistor R1b and the phase-B inductor Lb, and the other end of the phase-B regulating resistor R2b is connected to the first end Xb of the phase-B discharge coil and grounded; the end of the phase-B inductor Lb far from the phase-B regulating resistor R2b is connected to the second end B of the phase-B discharge coil; the third end dnb of the phase-B discharge coil is connected to the fourth end dc of the phase-C discharge coil; both ends of the phase-C capacitor Cc are respectively connected to both ends of the phase-C regulating resistor R2c; one end of the phase-C regulating resistor R2c is connected to the phase-C resistor R1c and the phase-C inductor Lc, and the other end of the phase-C regulating resistor R2c is connected to the first end Xc of the phase-C discharge coil and grounded; the end of the phase-C inductor Lc far from the phase-C regulating resistor R2c is connected to the second end C of the phase-C discharge coil.

[0070] In this embodiment, the voltage part of the device is sampled by high-precision resistors. It can not only achieve zero-sequence, measurement, and protection functions, but also after the integration of the two, it is integrally encapsulated and insulated by epoxy resin. The secondary wiring is connected by three four-core shielded wires 13, and the output signal can be connected in parallel with a six-core shielded paired twisted cable with a length of 15 meters and the accuracy at the end remains unchanged. This combined structure can facilitate installation, reduce on-site wiring, save space, and is convenient for maintenance. In addition, since the output of this device is a small voltage signal, it can avoid damaging the controlled equipment and can be directly interfaced with secondary integrated automation equipment such as meters and relay protection devices, thereby realizing voltage measurement, protection, and zero-sequence functions. It not only has complete functions, is simple and convenient to install and use, reduces energy consumption during operation, but also does not require equipment maintenance.

[0071] Therefore, this embodiment has the following advantages: 1. The product is small, flexible, and easy to install without damaging the original design. Especially for cabinets that are already in operation, the product can be installed in the existing space without modifying the original equipment or adding new floor space, saving a large amount of costs for users, greatly reducing the construction difficulty, enabling many ring main units that originally did not have the conditions for transformation to obtain measurement, monitoring, and protection functions, and providing a brand-new solution for the secondary equipment of the distribution automation of ring main units. 2. This device is equipped with a special cable accessory adapter, which solves the installation difficulties caused by the large number of cable accessory manufacturers on site and different sizes, improves the adaptability and installation success rate of this device, and greatly reduces the on-site power outage time, construction difficulty, and the risk of construction failure. 3. This device saves materials, is energy-saving and environmentally friendly, reduces the use of copper and iron, thereby greatly reducing copper loss, iron loss, and its own loss, and can greatly reduce the accident rate of line ferromagnetic resonance faults easily occurring due to iron core transformers. 4. This device collects signals through the principle of resistor-capacitor voltage division, which is stable and reliable. And when system faults such as single-phase grounding and phase loss occur, it can still provide stable analog signals.

[0072] In summary, a cable-type phase-zero-sequence integrated three-phase sensor for a ring main unit proposed by the present utility model has the following advantages:

[0073] Through three phase sensors with the same structure and integrated phase-zero-sequence, namely the A-phase sensor, B-phase sensor, and C-phase sensor respectively; each sensor is used to measure and output the voltage signal of the corresponding phase; and a zero-sequence circuit, which is connected to the A-phase sensor, B-phase sensor, and C-phase sensor, and is used to detect and output the zero-sequence voltage signal. This device can achieve voltage measurement, protection, and zero-sequence functions.

[0074] In addition, the voltage in the A-phase sensor, B-phase sensor, and C-phase sensor of this device uses a high-precision columnar non-inductive thick film resistor to output a small voltage signal, and the temperature drift coefficient of this device is small; it can ensure that when this device works outdoors and at -40°C to +70°C, the error range of this device is almost unchanged, so the anti-interference ability is strong. By isolating and outputting a small voltage signal in two groups, it is ensured that the phase sequence and zero-sequence small voltage signals are output separately, without mutual interference or influence, and the measurement and protection signals work independently, ensuring the more reliable performance of this device.

[0075] Furthermore, the voltage part of this device samples through high-precision resistors, which can not only achieve zero-sequence, measurement, and protection functions, but also be integrally encapsulated and insulated with epoxy resin after integration. The secondary wiring is connected through three four-core shielded wires, and the output signal can be connected in parallel to a six-core shielded paired twisted cable with a length of 15 meters and the accuracy at the end remains unchanged. This combined structure can facilitate installation, reduce on-site wiring, save space, and is convenient for maintenance. In addition, since the output of this device is a small voltage signal, it can avoid damaging the controlled equipment and can be directly interfaced with secondary integrated automation equipment such as meters and relay protection devices, thereby realizing voltage measurement, protection, and zero-sequence functions. It not only has complete functions, is simple and convenient to install and use, reduces energy consumption during operation, but also does not require equipment maintenance.

[0076] Obviously, those skilled in the art can make various changes and modifications to the present utility model without departing from the spirit and scope of the present utility model. Thus, if these modifications and variations of the present utility model fall within the scope of the claims of the present utility model and their equivalent technologies, the present utility model also intends to include these changes and modifications.

Claims

1. A cable-type phase zero-sequence integrated three-phase sensor for a ring main unit, characterized in that: include: Three phase sensors with the same structure and integrated phase zero sequence, namely phase A sensor, phase B sensor, and phase C sensor; each sensor is used to measure and output the voltage signal of the corresponding phase; as well as The zero-sequence circuit is connected to the A-phase sensor, the B-phase sensor, and the C-phase sensor, and is used to detect and output a zero-sequence voltage signal.

2. The cable-type phase zero-sequence integrated three-phase sensor for ring main unit according to claim 1, characterized in that: The phase sensor includes a cable head, a jacket, an epoxy tube, a high-voltage resistor, a casing, a low-voltage resistor, a secondary capacitor, an adjustable resistor, an isolation transformer, a base and a four-core shielded wire; The cable head is mounted at one end of the outer jacket; The other end of the outer sleeve is connected to the sleeve, and the outer sleeve and the sleeve form a hollow cylindrical structure; The epoxy tube is located on the inner side wall of the hollow cylindrical structure and is connected to the cable head; The high-voltage resistor is located inside the hollow cylindrical structure, and one end of the high-voltage resistor is connected to the cable head, and the other end is connected to the low-voltage resistor and the secondary capacitor; One end of the low voltage resistor away from the high voltage resistor is connected to the adjustable resistor; One end of the adjustable resistor away from the low voltage resistor is connected to the negative end of the isolation transformer and the secondary capacitor; The base is connected to an end of the sleeve away from the outer sleeve; The isolation transformer and the four-core shielded wire are connected and both are located inside the base; One end of the four-core shielded wire away from the isolation transformer extends to the outside of the base.

3. The cable-type phase zero-sequence integrated three-phase sensor for ring main unit according to claim 2, characterized in that: The phase sensor further comprises a transient protection tube; one end of the transient protection tube is connected between the high voltage resistor and the low voltage resistor, and the other end of the transient protection tube is connected between the adjustable resistor and the isolation transformer.

4. The cable-type phase zero-sequence integrated three-phase sensor for ring main unit according to claim 2, characterized in that: The material of the base includes: aluminum alloy.

5. The cable-type phase zero-sequence integrated three-phase sensor for ring main unit according to claim 2, characterized in that: The base is a hollow structure and is communicated with the hollow cylindrical structure; the base and the hollow cylindrical structure are filled with closed insulating material.

6. The cable-type phase zero-sequence integrated three-phase sensor for ring main unit according to claim 5, characterized in that: The encapsulating insulating material includes epoxy resin.

7. The cable-type phase zero-sequence integrated three-phase sensor for ring main unit according to claim 2, characterized in that: The material of the outer shell includes silicone rubber material.

8. The cable-type phase zero-sequence integrated three-phase sensor for ring main unit according to claim 2, characterized in that: The material of the sleeve includes semi-conductive silicone rubber material.

9. The cable-type phase zero-sequence integrated three-phase sensor for ring main unit according to claim 1, characterized in that: The zero-sequence circuit includes an A-phase resistor, a B-phase resistor, a C-phase resistor, an A-phase overvoltage protection device, a B-phase overvoltage protection device, and a C-phase overvoltage protection device; One end of the A-phase resistor, the B-phase resistor and the C-phase resistor is connected to the A-phase sensor, the B-phase sensor and the C-phase sensor respectively; The other ends of the A-phase resistor, the B-phase resistor and the C-phase resistor are connected to the A-phase overvoltage protection device, the B-phase overvoltage protection device and the C-phase overvoltage protection device respectively; The A-phase overvoltage protection device is connected to the B-phase overvoltage protection device; The B-phase overvoltage protection device is connected to the C-phase overvoltage protection device.

10. The cable-type phase zero-sequence integrated three-phase sensor for ring main unit according to claim 1, characterized in that: The A-phase overvoltage protection device includes an A-phase capacitor, an A-phase regulating resistor, an A-phase mutual inductor and an A-phase discharge coil; the B-phase overvoltage protection device includes a B-phase capacitor, a B-phase regulating resistor, a B-phase mutual inductor and a B-phase discharge coil; the C-phase overvoltage protection device includes a C-phase capacitor, a C-phase regulating resistor, a C-phase mutual inductor and a C-phase discharge coil; The two ends of the A-phase capacitor are respectively connected to the two ends of the A-phase regulating resistor; one end of the A-phase regulating resistor is connected to the A-phase resistor and the A-phase mutual inductor, and the other end of the A-phase regulating resistor is connected to the first end of the A-phase discharge coil and is grounded; one end of the A-phase mutual inductor away from the A-phase regulating resistor is connected to the second end of the A-phase discharge coil; the third end of the A-phase discharge coil is connected to the fourth end of the B-phase discharge coil; The two ends of the B-phase capacitor are respectively connected to the two ends of the B-phase regulating resistor; one end of the B-phase regulating resistor is connected to the B-phase resistor and the B-phase mutual inductor, and the other end of the B-phase regulating resistor is connected to the first end of the B-phase discharge coil and is grounded; one end of the B-phase mutual inductor away from the B-phase regulating resistor is connected to the second end of the B-phase discharge coil; the third end of the B-phase discharge coil is connected to the fourth end of the C-phase discharge coil; The two ends of the C-phase capacitor are respectively connected to the two ends of the C-phase regulating resistor; one end of the C-phase regulating resistor is connected to the C-phase resistor and the C-phase mutual inductor, and the other end of the C-phase regulating resistor is connected to the first end of the C-phase discharge coil and is grounded; one end of the C-phase mutual inductor away from the C-phase regulating resistor is connected to the second end of the C-phase discharge coil.

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