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Safety precautions for using AC/DC withstand voltage testing equipment
2025-07-09The arrangement of the AC/DC withstand voltage test device must ensure sufficient safety distance between people and their surroundings. Try to avoid placing equipment and high-voltage testing lines in personnel walkways as much as possible.The test site should be fenced and a "Stop! High Voltage Danger" sign should be hung.Testing high-voltage lines must have supporting or traction insulators. Protective devices should be installed at every interval and at the other end of the cable to prevent people from approaching and passing underneath.The microampere meter for DC high voltage testing should be at a high potential. In addition to the shielding box, there should also be an automatic overcurrent protection device to prevent the instrument from suddenly breaking down, short circuiting, or burning out during discharge.Power frequency withstand voltage test, please pay attention to checking whether the equipment capacity is sufficient to avoid resonance.The working grounding wire (high
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Comparison between Parallel Power Supply and Series Power Supply
2025-07-09Parallel resonant intermediate frequency power supply is the mainstream intermediate frequency power supply in China, which adopts parallel resonant inverter technology. This technology originated from the former Soviet Union. The power supply has low technical requirements for components, and there are many manufacturers of supporting components. The manufacturing cost of the power supply is low, and its performance is stable. Especially, the popularity of medium frequency furnaces with small and medium capacities is high. However, with the continuous improvement of energy conservation and consumption reduction requirements, the shortcomings of this technology are increasingly being concerned by people. Its main manifestations are:(1) The power regulation of low power factor parallel inverters mainly relies on changing the rectified voltage of the three-phase fully controlled bridge. When the control pulse a of the rectifier bridge is ≤ 0 ° (DC voltage is lower than the maximum value)
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A Comprehensive Guide to Series Resonant Pulse Modulation Methods
2025-07-08The amplitude modulation control method is achieved by adjusting the output voltage Ud of the DC voltage source (inverter input) (which can be achieved by using a phase-shifting voltage regulation circuit or a filtering circuit composed of a chopper voltage regulation circuit and inductors and capacitors) to regulate the output power. The output power of the inverter is regulated by the input voltage, and the phase control between current and voltage is achieved by a phase-locked loop (PLL) to ensure a high power factor output.The pulse density modulation method is to control the output power by controlling the pulse density, which is actually to control the time of feeding energy to the load. The control principle and basic idea of this control method are: assuming there are a total of N power regulation units, among which M power regulation units, the inverter outputs power to the load; And the remaining N-M units of inverters stop working, and the load energy gradually decays in a n
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What is the BDV test for oil?
2025-07-08The Oil BDV Tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.What is the BDV Test for Oil?The BDV Test refers to the Breakdown Voltage Test.BDV stands for Breakdown Voltage.Purpose of the TestIt is used to evaluate the electrical insulation strength of insulating oils (e.g., transformer oil, switchgear oil, cable oil). Simply put, it measures the oil’s ability to resist electrical breakdown (formation of a conductive path) under an electric field.Test Principle1.Sample Preparation: An oil sample is poured into a standardized test cell.2.Electrode Setup: Two electrodes (typically spherical or spherical-plane) are positioned at a precise standard gap (usually 2.5 mm).3.Voltage Application: An increasing AC voltage (typically 50/60 Hz) is applied between the electrodes.4.Breakdown Observation: Voltage rises until a sudden breakdown occurs (visible spark/arc), causing a surge in current.5.Result Recording: The voltage (in kilovolts, kV) at th
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How does a circuit breaker tester work?
2025-07-07The Circuit Breaker Tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.Core Working Principle Steps:1.Simulating Fault Current:The tester contains a high-current generator (typically based on transformers or power electronics) capable of outputting currents ranging from hundreds to tens of thousands of amperes.Adjustable parameters: Users can set current values (e.g., 1.5x, 10x rated current), duration (0.01s to several seconds), and current waveforms (DC, AC sine wave, or transient pulses).2.Connecting the Tested Circuit Breaker:Connect the tester’s high-voltage output terminals to the circuit breaker’s input terminals (e.g., main contacts) and its ground terminal to the breaker’s output or grounding busbar.Use control wires to interface with the breaker’s trip/close coils (for remote triggering).3.Triggering Tests and Data Acquisition:Manual mode: The user manually initiates the test; the instrument outputs preset current.Automatic mode:
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What is the difference between ductor test and contact resistance test?
2025-07-07The Contact Resistance Tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.1.Conductor Testing:What it measures: The conductor material itself (e.g., a single wire, a metal busbar).Purpose: To see how well the conductor conducts electricity overall (how low its resistance is).Focus: Material, cross-sectional area (thickness), length, continuity (no breaks).Result: Typically on the order of Ohms (Ω).2.Contact Resistance Testing:What it measures: The point where two conductors connect (e.g., switch contacts, terminals, plug/socket interfaces).Purpose: To see how good the connection point is (how tight the contact is, how clean the surfaces are).Focus: Contact pressure, surface oxidation, contamination, connection method.Result: Typically on the order of milliohms (mΩ).Key Difference in One Sentence:Conductor testing checks the conductive capability of the "wire itself", while contact resistance testing checks the conductive quality of the "con
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How does a vacuum interrupter work?
2025-07-04The Vacuum Interrupter Tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.A vacuum circuit breaker (VCB) is a type of circuit breaker that utilizes a high vacuum environment (pressure below 10 ⁻⁴ Pa) as an arc extinguishing and insulating medium. Its core working principle is to use the excellent insulation performance and arc extinguishing ability of vacuum to quickly and reliably cut off current, especially in the event of faults (such as short circuits).1.Core Component: Sealed Vacuum Interrupter Chamber (contains moving & fixed contacts).2.Breaking Process:Contacts separate → Creates a vacuum arc (sustained by vaporized metal).At AC current zero crossing, arc energy input is minimal.Vacuum Advantage: Minimal particles → Charged particles (electrons/ions) in the arc plasma diffuse extremely rapidly and condense onto the cool condensing shields/contacts.Instant Insulation Recovery: The gap almost immediately returns to a high-insulation v
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What device detects partial discharge?
2025-07-04What equipment can detect partial discharge?Let's analyze Partial Discharge Testers – instruments specifically designed to capture, measure, and analyze partial discharge phenomena occurring within electrical equipment. Based on detection principles and application scenarios, the main types are:1.Pulse Current (IEC 60270):Measures: Current pulses in ground connection.Pros: Most accurate quantification (pC).Cons: Needs direct connection, often offline, sensitive to noise.Use: Lab/factory tests, critical offline diagnostics (transformers, cables).2.Ultra-High Frequency (UHF):Measures: Radio waves (300MHz-3GHz) from PD.Pros: Non-contact, good noise immunity, online capable.Cons: Hard to calibrate (pC), complex signal paths.Use: Online monitoring (GIS/GIL), transformers, switchgear.3.Ultrasonic (Acoustic):Measures: Sound waves (20kHz-300kHz) from PD.Pros: Pinpoints location, immune to electrical noise, online capable.Cons: Hard to quantify (pC), signal weakens through material.Use: Loc
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What is a PD inspection?
2025-07-03The PD tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.PD Inspection (Partial Discharge Inspection)Definition:A critical non-destructive testing and diagnostic technique for assessing the insulation systems of electrical equipment (especially high-voltage assets). It detects, measures, and analyzes partial discharge phenomena within insulation structures.1. Purpose of PD InspectionEvaluate insulation integrity.Provide early fault detection.Ensure manufacturing/installation quality.Enable predictive maintenance (avoid unplanned downtime).Diagnose root causes post-failure.2.How to conduct PD examination? (Main detection methods)PD can produce various physical and chemical effects, therefore there are multiple detection methods:Electrical measurement method:Pulse current method: the most classic and standardized method. By detecting the pulse current signal generated by PD collected by coupling capacitors or high-frequency current transform
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What is the difference between primary and secondary current injection test set?
2025-07-03The Primary Injection Test Set under Wuhan UHV can help many power workers conduct various power tests more conveniently.Primary Current Injection Test Set1.Injection Point: Test current is injected directly into the primary circuit (e.g., onto the busbar, cable lug, or the primary terminals of the Current Transformer (CT)).2.Current Magnitude: Generates very high currents (hundreds or thousands of Amperes) to simulate real-world fault conditions flowing through the primary conductors and the CT.3.What it Tests/Verifies:The entire current path: Primary conductors, CT primary winding, CT core, CT secondary winding, secondary wiring (cables, terminals), connections, and finally the protective relay itself.CT Performance: Accuracy, ratio, polarity, saturation characteristics under high fault current.Wiring Integrity: Correctness of the entire secondary circuit from CT terminals to relay inputs (phasing, grounding, shorts, opens).Overall System Performance: Verifies that the entire protect
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What is the difference between primary and secondary injection kit?
2025-07-02The Primary Current Injection Test Kit under Wuhan UHV can help many power workers conduct various power tests more conveniently. The difference between primary and secondary injection kits lies in where they inject test current and what part of the protection system they test. Here's a breakdown:1. Secondary Injection Kit:Target: The relay itself (specifically its input terminals).Injection Point: Directly into the secondary terminals of the Current Transformers (CTs) and Voltage Transformers (VTs) - which is where the relay normally connects.Current Level: Low current (typically milliamps to a few amps). Simulates the secondary signals the relay sees from the CTs/VTs.Purpose:Verify the relay's internal functionality: Settings, logic, timing, pickup/dropout, characteristic curves (e.g., IDMT), output contacts, communications.Test the relay in isolation from the actual primary circuit and instrument transformers.Commissioning, routine maintenance, troubleshooting relay-specific
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How often should protection relays be tested?
2025-07-02The Relay Protection Tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.Protection relays act as the "safety guardians" of power systems. While there is no absolute uniform standard for testing frequency—as it depends on multiple factors—regular testing is mandatory to ensure reliable operation during critical events and prevent catastrophic failures.Key Factors Influencing Testing IntervalsManufacturer RecommendationsThe primary reference. Relay manuals or maintenance guides typically specify recommended testing intervals. Always prioritize these guidelines.Equipment CriticalityCritical assets (e.g., generators, main transformers, essential busbars, high-capacity feeders):Failure may cause widespread outages, major equipment damage, or safety hazards.→ Highest frequency: Annual comprehensive functional and calibration testing at minimum.Less critical assets (e.g., general distribution feeders, motors):→ Lower frequency: Testing every
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How to check motor DC or AC?
2025-06-30The AC/DC Motor Test Bench under Wuhan UHV can help many power workers conduct various power tests more conveniently.1.Check the Nameplate (Most Reliable):Locate the nameplate on the motor housing.Look for voltage markings: "DC" or "V DC" (e.g., 12V DC) indicates a DC motor. "AC" or "V AC" (e.g., 220V AC) or a frequency rating (50Hz/60Hz) indicates an AC motor.Check the model number: "DC" or "BLDC" usually means DC; "AC" usually means AC. 2.Inspect Physical Structure & Wiring:Commutator and Brushes visible (open the rear cover to see segmented copper rings and spring-loaded carbon blocks): Very likely a Brushed DC Motor.No Commutator/Brushes: Could be an AC motor or a Brushless DC (BLDC) motor.Number of Power Wires:Only 2 wires: Could be a DC motor or a simple single-phase AC motor (needs further testing).3 main wires (labeled U/V/W): Typically an AC Three-Phase Motor.3 wires (may include capacitor leads): Typically an AC Single-Phase Motor. 3.Measure Resistance (Multimeter):Three-Phas
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What is an electrical test bench?
2025-06-30The Transformer Test Bench under Wuhan UHV can help many power workers conduct various power tests more conveniently.An Electrical Test Bench is a comprehensive platform used for testing, verifying, diagnosing, and evaluating the performance of various electrical equipment, components, systems, or circuits. Its scope is broader than a Motor Test Bench, encompassing not just rotating machines (motors/generators), but also transformers, switchgear, circuit breakers, relays, contactors, controllers, power supplies, wiring harnesses, cables, electronic circuit boards, and even entire electrical systems. Core Functions & Test Items1.Performance Characterization:Input/Output Characteristics (voltage regulation, load regulation, efficiency).Start-up/Shut-down Characteristics.Steady-State and Dynamic Response (e.g., response to load/input steps).Power Factor Correction (PFC) Performance.Output Ripple & Noise.2.Safety & Compliance Testing:Insulation Resistance Test: Verifies insulation integrit
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What is the standard for motor testing?
2025-06-27The Motor Test System under Wuhan UHV can help many power workers conduct various power tests more conveniently.I. Core International StandardsIEC 60034 SeriesIEC 60034-1: General performance & safety requirements (temperature rise/voltage withstand baseline)IEC 60034-2-1: Precision efficiency testing (basis for IE classification)IEC 60034-30-1: Defines global IE1-IE5 efficiency classesII. Regional Mandatory StandardsChina:GB 18613 (Mandatory efficiency, equivalent to IE3/IE4)GB/T 755 (Aligns with IEC 60034-1)North America:NEMA MG-1 (Core industrial motor specification)IEEE 112 (Primary efficiency test method)European Union:EN 60000 Series (Full adoption of IEC standards)EU Regulation 2019/1781 (Mandates IE3/IE4 efficiency)III. Key Test Item StandardsEfficiency: IEC 60034-2-1 or IEEE 112Temperature Rise: IEC 60034-1 Section 6 (limits by insulation class)Voltage Withstand: IEC 60034-1 Section 8.3 (2Un + 1000V/1 minute)Vibration: IEC 60034-14 (Class A/N levels)Noise: IEC 60034-9 (graded
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What does a CT meter do?
2025-06-27The CT Tester under Wuhan UHV can help many power workers conduct various power tests more conveniently.I. Core Testing Functions1.Turns Ratio TestingPrecisely measures the actual primary-to-secondary current ratio of CTs.Verifies compliance with nameplate ratings (e.g., 1000A/1A).Criticality: Incorrect ratios cause metering errors or protection maloperation.2.Polarity VerificationDetermines the relative polarity (dot convention) of primary and secondary windings.Criticality: Polarity errors may lead to meter reversal, differential protection failure, or false tripping.3.Excitation Characteristic (V-I Curve) TestingPlots the excitation current vs. voltage curve (I-V curve) of secondary windings.Derives key parameters:Knee-Point Voltage/Current: Identifies CT core saturation threshold.Accuracy Limit Factor (ALF): Evaluates protection-class CT accuracy under fault currents.Composite Error: Core performance metric for protection CTs.Criticality: Determines CT reliability during fault cond
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Which instrument should be used to perform a dielectric watt loss test?
2025-06-26The core instrument used for dielectric loss testing (loss tangent tanδ measurement) is a Dielectric Loss Test Set, also known as a Tan Delta Tester or Schering Bridge. Based on technical principles and automation levels, the main types are:1. Traditional Schering BridgePrinciple: Classic balanced bridge method requiring manual adjustment of resistive/capacitive arms to achieve balance for calculating tanδ and capacitance.Characteristics:High accuracy (historically the laboratory standard).Complex operation, demanding skilled personnel.Slow testing speed.Requires external HV source (e.g., test transformer) and reference capacitor.Application: Laboratory precision measurements or calibration reference. Rarely used for field preventative testing today.2. Digital Automatic Dielectric Loss TestersPrinciple: Uses digital measurement techniques (e.g., digital sampling, vector analysis) to automatically measure current magnitude/phase difference under applied voltage. Directly calculates and
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What is the purpose of transformer turns ratio test?
2025-06-26Transformer Turns Ratio (TTR) testing (also known as ratio testing or turns ratio testing) is a core and fundamental test in transformer manufacturing, installation, and maintenance. Its main purposes include the following aspects:1.Verify Design Intent and Manufacturing Correctness:This is the most fundamental purpose. The turns ratio is one of the most critical design parameters of a transformer, directly determining the proportional relationship between input and output voltage (neglecting losses and excitation current).The test ensures that the windings were wound with the exact number of turns specified by the design, confirming the transformer can provide the intended voltage transformation function.2.Detect Winding Defects:Interturn Short Circuits: This is one of the most important fault detection purposes. Even a short circuit involving only a few turns will significantly alter the effective number of turns in that winding, causing the turns ratio for that phase to deviate from
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What is a DC winding resistance test?
2025-06-25A DC Winding Resistance Test is a fundamental electrical measurement used to determine the ohmic resistance of windings in devices like transformers, motors, generators, and reactors. Performed with direct current (DC), it eliminates inductive effects, providing precise resistance values for quality control, diagnostics, and performance validation. Purpose1.Baseline Data: Establish reference resistance for future comparisons.2.Fault Detection: Identify issues like loose connections, broken conductors, or uneven winding turns.3.Loss Calculation: Compute copper (I²R) losses for efficiency analysis.4.Temperature Validation: Verify winding temperature rise during heat runs. Test EquipmentPrimary Tools:Micro-ohmmeter (4-wire Kelvin method, accuracy ±0.1%).DC resistance bridge (Wheatstone/Kelvin bridge for high precision).Alternatives:Voltmeter-ammeter method (less accurate, requires stable current source).Accessories:Temperature sensor (infrared gun or RTD), current clamps, heavy-duty leads
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What is variable frequency AC series resonant test system?
2025-06-25A Variable-Frequency AC Series Resonant Test System is an insulation performance testing device that utilizes the principle of series resonance and variable-frequency technology to achieve efficient high-voltage output. It is specifically designed for on-site AC withstand voltage testing of large electrical equipment (such as power cables, transformers, GIS, etc.). Its core principle is to adjust the power supply frequency to achieve resonance in the circuit, thereby generating the required high voltage using a relatively small-capacity power supply.I. System Components1.Variable-Frequency Power SupplyThe core control unit, outputs a sine wave with adjustable frequency (typically 30-300 Hz).Automatically scans for the resonant point and adjusts the frequency in real-time to maintain resonance.2.Excitation TransformerProvides voltage step-up and isolation, boosting the output voltage of the variable-frequency power supply to the initial voltage required for resonance (designed with smal
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