Sa pagkamalikhain sa mga sistema sa kuryente, ang mga electronic voltage transformers (EVTs), isip mga pangunahon nga mga panukid sa pagsukod sa mga sistema sa kuryente, ang ilang matumong pagkamalikhain ug pagkareliable kay importante para sa maayo ug malihok nga operasyon sa mga sistema sa kuryente. Ang electromagnetic compatibility (EMC) performance, isip usa ka core indicator sa mga EVTs, direkta naka-ugnay sa abilidad sa panukid nga makapagtuman sa normal nga pagtuman sa komplikado nga mga electromagnetic environment ug kung mahimong magdala og electromagnetic interference sa uban pang mga panukid. Ang paghimo og in-depth research ug disenyo sa EMC performance sa mga EVTs labi nga importante aron mapataas ang kabuokan nga stability ug seguridad sa mga sistema sa kuryente.
1 Overview of Electromagnetic Compatibility Performance of Electronic Voltage Transformers
1.1 Definition and Requirements of Electromagnetic Compatibility
Ang electromagnetic compatibility (EMC) nagpasabot sa abilidad sa usa ka panukid o sistema nga makapagtuman sa normal nga operasyon bisan sa presensya sa specific electromagnetic environment ug dili magdala og intolerable electromagnetic harassment sa uban pang mga butang sa environment. Para sa mga EVTs, sila kinahanglan magpadayon sa stable nga pag-sukod performance sa komplikado nga mga electromagnetic environments ug dili magdala og electromagnetic interference sa uban pang mga panukid. Diliha, sa panahon sa disenyo ug pagbuhat sa mga EVTs, kinahanglan imong hinganan ang EMC performance, ug ihimo ang kasagaran nga mga safeguard measures.
1.2 Working Principle of Electronic Voltage Transformers
Ang mga EVTs gamiton ang principle sa electromagnetic induction ug high-precision electronic measurement technology aron mopagbalhin ang high-voltage signals sa mga sistema sa kuryente ngadto sa low-voltage signals. Kasagaran sila gisusunod sa primary sensor, secondary conversion circuit, ug signal processing unit. Ang primary sensor responsable sa pagpagbalhin sa high-voltage signals ngadto sa weak current/voltage signals proportional sa primary voltage; ang secondary conversion circuit molihok pa og pagbalhin sa weak signals ngadto sa standard digital/analog signals; ang signal processing unit mag-improve sa accuracy ug stability sa pagsukod pinaagi sa filtering, amplifying, ug calibrating. Ang mga EVTs makakapot sa iba't ibang forms, sama sa electronic voltage transformers para sa pag-sukod sa single-channel/multi-channel voltages, electronic current transformers para sa pag-sukod sa single-channel/multi-channel currents, o integrated transformers sama sa Figure 1 nga sukad sa one-way voltage, current, ug corresponding power simultaneously.
1.3 Analysis of Electromagnetic Harassment and Electromagnetic Sensitivity
Ang mga EVTs vulnerable sa external electromagnetic harassment sa electromagnetic environment, sama sa lightning strikes ug transient overvoltages gikan sa switch operations, nga mahimo mogawas sa problema sama sa increased measurement errors ug unstable data; samtang ang high-frequency harmonics ug electromagnetic radiation gikan sa mga EVTs mismo usahay mag-interfere sa uban pang mga electrical equipment. Diliha, sa panahon sa pag-disenyo sa mga EVTs, kinahanglan imong hinganan ang issues sa electromagnetic harassment ug electromagnetic sensitivity, ug gi-implementar ang suppression ug protection measures.
Ang EMC performance test sa mga EVTs usa ka key link aron masiguro ang ilang stability ug accuracy sa actual operation. Ito focus sa anti-interference ability ug classify ang evaluation standards isip Class A ug Class B sumala sa severity sa test results:
2 Analysis of Electromagnetic Compatibility Performance Tests of Electronic Voltage Transformers
2.1 Test Content and Evaluation Standards
Class A: Gitumong nga ang mga EVTs, bisan na-expose sa electromagnetic harassment, ang measurement accuracy magpadayon sa within the specification limits, ug ang output voltage signal consistent sa actual value ug dili makaapekto sa monitoring ug control sa sistema sa kuryente.
Class B: Gitugutan ang temporary decline sa measurement performance (ang bahin dili related sa protection) sa mga EVTs, pero dili dapat makaapekto sa execution sa protection functions, ug ang equipment dili gikinahanglan i-reset/restart; ang output voltage kinahanglan kontrolado sa within 500V aron dili maka-interfere sa sistema sa kuryente.
2.2 Conducted Interference Tests
Ang conducted interference propagates pinaagi sa conductive paths sama sa wires ug metal pipes ug usa sa primary types of electromagnetic harassment faced by EVTs. Kini nagsama sa duha ka types of tests:
Electrical Fast Transient/Burst Test: Simulates the transient harassment (with a wide frequency spectrum) when inductive loads such as relays and contactors are disconnected. Applies a fast-transient burst to the EVT, observes the stability and accuracy of the output voltage signal, and evaluates the anti-interference ability.
Surge (Impact) Immunity Test: Simulates transient overvoltages/overcurrents caused by switch operations and lightning strikes (with large energy and short duration). Applies a surge voltage of a certain amplitude to the EVT to test the equipment's withstand capacity and performance stability.
2.3 Radiated Interference Tests
Kini nagsama sa apat ka types of tests aron simularon ang interferences sa different electromagnetic environments:
Power Frequency Magnetic Field Immunity Test: Applies a power frequency magnetic field of a certain intensity to the EVT, observes the stability and accuracy of the output voltage signal, and evaluates the anti-interference ability in the power frequency magnetic field environment.
Damped Oscillatory Magnetic Field Immunity Test: Simulates the damped oscillatory magnetic field (with fast attenuation and high frequency) generated when the disconnector in a high-voltage substation switches the bus. Applies the corresponding magnetic field to the EVT to test the stability of the measurement performance.
Pulse Magnetic Field Immunity Test: Simulates the pulse magnetic field (with fast rise and high peak value) generated by lightning strikes on metal components. Applies a pulse magnetic field to the EVT to verify whether the insulation performance and measurement accuracy of the equipment are affected.
Radio Frequency Radiated Electromagnetic Field Immunity Test: Simulates parasitic radiation from industrial electromagnetic sources, radio broadcasts/mobile communication base stations, etc. Applies a radio frequency electromagnetic field of a certain intensity to the EVT, observes the stability of the output signal, and evaluates the anti-interference ability.
3 Design Principles for Electromagnetic Compatibility of Electronic Voltage Transformers
3.1 Circuit Design Principles
Floating Ground Design: Adopt floating ground technology to insulate the circuit signal lines from the chassis, block the coupling of interference currents on the chassis to the signal circuit, reduce noise, and improve signal accuracy and stability.
Reasonable Wiring Layout: Optimize the layout of power supplies, grounds, and signal lines. Reduce the parallel distribution of lines and minimize the coupling interference between lines through methods such as layered wiring and orthogonal wiring.
Filter Capacitor Design: Configure filter capacitors at the input end of the module power supply. Select the capacitors based on factors such as capacitance value, voltage resistance, and frequency characteristics to filter out high-frequency noise and interference introduced by the power supply.
Low-level Logic Design: Give priority to low-level logic devices (such as 3.3V level devices) to avoid unnecessary high logic levels, reduce circuit power consumption and the generation of high-frequency interference.
Rise/Fall Time Control: Select the slowest rise/fall time allowed by the circuit function to suppress unnecessary high-frequency components, reduce high-frequency noise in the circuit, and improve signal stability and accuracy.
3.2 Internal Structure Design Principles
Fully Enclosed Shielding Structure: The chassis shell adopts a fully enclosed shielding design to ensure good contact and grounding of each surface, effectively block external electromagnetic field interference, and protect the internal electronic circuits.
Minimization of Exposed Wiring: Shorten the length of exposed wiring in the chassis by optimizing the layout and reasonably arranging components to reduce electromagnetic radiation and coupling interference.
Group Bundling of Wires: Bundle wires according to signal types (separate digital signals and analog signals), and keep a certain distance to reduce the mutual influence between wires and improve signal clarity and accuracy.
Conductive Adhesive Bonding: Use conductive adhesive for bonding at the chassis interface to ensure electrical connection and shielding effect, reduce contact resistance, and improve shielding efficiency.
4 Strategies for Improving Electromagnetic Compatibility Performance of Electronic Voltage Transformers
4.1 Anti-interference Design of Power Ports
Install Power Filters: Select suitable power filters according to the rated power and working environment of the EVT, and install them close to the power inlet to filter out high-frequency noise and transient pulses and ensure power purity.
Adopt Redundant Power Design: Configure multiple power modules. When a single module fails, the remaining modules quickly take over the power supply, improving the power supply reliability, anti-interference ability, and overall stability of the EVT.
Strengthen Shielding and Grounding of Power Lines: Use shielded cables to wrap power lines to reduce electromagnetic radiation and coupling; ensure good grounding of the lines, introduce interference currents into the ground, and avoid damaging the EVT.
4.2 Electrostatic Discharge Protection of Signal Ports
Install Transient Harassment Absorption Devices: Select suitable transient voltage suppression diodes (TVS), varistors, and other devices. These devices can quickly absorb energy during electrostatic discharge, control the voltage within a safe range, and protect internal electronic components.
Adopt Differential Signal Transmission Method: Divide the signal into positive and negative channels for differential transmission. Use the signal difference between channels to extract effective information, resist common-mode interference, improve signal transmission quality, and reduce the interference of electrostatic discharge.
4.3 Optimization of Chassis Shielding Performance
Select High-Permeability Materials: Give priority to materials with high magnetic permeability such as iron plates to make the chassis, enhance the magnetic field shielding ability, absorb and disperse magnetic field energy, and reduce interference to the inside of the EVT (the relative magnetic permeability of metals is shown in Table 1).
Optimize Chassis Structure Design: Adopt a fully enclosed shielding structure to ensure good contact and grounding of each surface of the chassis and enhance the shielding effect.
Strengthen Chassis Grounding Treatment: Ensure a reliable grounding connection between the chassis and the ground, introduce interference currents into the ground, and improve shielding efficiency.
5 Conclusion
This paper conducts in-depth research on the EMC performance of EVTs, proposes principles from the aspects of circuit design and internal structure design, and formulates strategies such as anti-interference design of power ports, electrostatic protection of signal ports, and optimization of chassis shielding. The aim is to improve the anti-interference ability and stability of EVTs in complex electromagnetic environments, ensure their accurate and reliable measurement of voltage signals in power systems, and lay a solid foundation for the safe and stable operation of power systems.
