Unsa ang gilabay sa pagsulay sa mga photovoltaic transformers?

1. Espesipikidad ug Mga Rekwirimento sa Pagsulay alang sa Photovoltaic Transformers

Isip teknisyan sa bag-ong sistema sa energia, nakakita ko sa unikong disenyo ug aplikasyon sa mga photovoltaic transformers: Inverter - ang output na AC adunay daghan nga 5th/7th - order na odd harmonics, uban ang PCC harmonic current distortion nga nakaabot sa 1.8% (mas taas nga voltage distortion sa low load), nagdulot sa overheating sa winding ug mas maong pag-edad sa insulation. Ang mga photovoltaic systems gigamit og TN - S grounding, kini nagkinahanglan og reliable N - phase output gikan sa secondary side aron mapugos ang short circuits. Sa kalibutan, kini kinahanglan molihok sa 60°C sa desert, coastal salt spray, ug industrial EMI.

Ang mga espesipikidad niini nagdisyahan sa unikong pagsulay: Hinumdumi sa tradisyonal nga DC resistance, voltage ratio, insulation, ug withstand voltage tests, idugang ang harmonic detection (Fluke F435 para sa THD), temperature rise monitoring (infrared imagers), grounding system checks (four - terminal method para sa ≤0.1Ω contact resistance), ug short - circuit impedance testing. Ang core aim mao ang paglihok sa safe operation sa power electronic environments samtang i-prevent ang harmonic, thermal, ug grounding - related risks.

2. Tradisyonal nga Mga Item sa Pagsulay ug Pagpili sa Tool alang sa Photovoltaic Transformers
2.1 DC Resistance Test

Kini nga key test nakakita sa inter - turn short circuits o loose connections sa windings. Ang four - terminal method gigamit aron mapugos ang line resistance interference, uban ang mga prosedura kasagaran ang power-off discharge, winding cleaning, temperature measurement, current selection (1A/10A), ug temperature correction. Ang ZSCZ - 8900 DC resistance tester (accuracy: 0.2%±2μΩ, resolution: 0.1μΩ) nakakatubag sa high - precision requirements. Ang measured values kinahanglan ipagkumpara sa standards/historical data; significant deviations mahimong mag-indikar sa faults - as seen in a case where poor winding contact was detected via DC resistance testing and later repaired.

2.2 Voltage Ratio Test

Kini nagpatuman kung ang winding turns ratios naka-align sa design specifications aron sigurado ang stable voltage output under load. Ang dual - voltmeter method nagkuha sa ratios pinaagi sa pag-measure sa primary/secondary voltages under no - load conditions, samtang ang voltage ratio bridge method naghatag og mas taas nga precision. Isip eemplo, ang voltage imbalance sa low - voltage output sa 800V/400V transformer, gihatagan sa high - voltage side open circuit, nakakita pinaagi sa voltage ratio testing.

2.3 Insulation Performance Test

• Insulation Resistance Test: Gamiton ang MI - 2094H megohmmeter, measure insulation resistance between windings and between windings and the core (required ≥300MΩ).

• Withstand Voltage Test: Apply 2× rated voltage for 60 minutes to check for breakdown. Ensure power is off, disconnected from live equipment, and surfaces are clean before testing.

2.4 Short - Circuit Impedance Test

Ang volt - ampere method evaluates short - circuit tolerance: one side is shorted, and a test voltage is applied to the other side to drive rated current through windings, measured by a CS - 8 impedance tester. A change >±2% from the factory value may indicate winding deformation. Note: Test current should be controlled at 0.5% - 1% of rated current to avoid waveform distortion.

2.5 Temperature Rise Test

After full - load operation, measure temperatures of windings, core, and casing using thermometers or infrared thermometers. Temperature rises should be ≤60K for oil - immersed transformers and ≤75K for dry - type transformers. A dry - type transformer operating in a 60°C environment that maintained a temperature rise within 65K extended its service life effectively.

2.6 Grounding System Test

The four - terminal method measures grounding continuity to avoid misjudgments from the two - terminal method. Common faults include rusted connections or plastic washer misuse, requiring regular inspection. Four - terminal ground resistance testers ensure measurements meet the 0.1Ω standard.

2.7 Harmonic Detection

A unique test for photovoltaic systems, using Fluke F435 at the PCC to detect harmonics up to the 50th order (focusing on 5th/7th orders). Results must comply with GB/T 14549 - 93, providing data for equipment optimization.

3. On - site Testing Procedures and Safety Specifications for Photovoltaic Transformers
3.1 Pre - testing Preparation

Develop detailed plans specifying project information, testing items, and equipment lists (including high - precision power analyzers, power quality testers, infrared thermal imagers, etc.). Check equipment integrity and power voltage (220V&plusmn;10%), and monitor environmental conditions - such as irradiance &ge;700W/m&sup2;, irradiance variation <2% in the preceding 5 minutes, no strong winds or clouds - to ensure test accuracy.

3.2 Electrical Connection Inspection

Use a phase volt - ampere meter to verify inverter output polarity matches the transformer's primary corresponding terminal, preventing circulating current losses. Inspect cable connections for tightness. For oil - immersed transformers, check oil level and color; for dry - type transformers, verify cooling fans operate normally.

3.3 Insulation Resistance Test

With power off, use a megohmmeter to test high/low - voltage windings and grounding, recording 1 - minute stable values. A sudden resistance drop indicates insulation issues. Detailed test reports must be compiled post - testing.

3.4 AC Withstand Voltage Test

Connect the withstand voltage device's output to test points, set parameters to 2&times; rated voltage, gradually increase voltage while monitoring for breakdown, and maintain for 60 minutes before reducing voltage.

3.5 Load Test

Measure output voltage, current, and power under full - load operation to calculate efficiency and voltage regulation rate, while monitoring temperature rise. Increase load current gradually and record parameter changes for analysis.

3.6 Short - Circuit Impedance Test

Apply voltage to the high - voltage side with the low - voltage side shorted (using wires with sufficient cross - section). Control test current at 0.5% - 1% of rated value and correct results for temperature (75&deg;C for oil - immersed, 120&deg;C for dry - type) to avoid misjudging winding deformation.

3.7 Harmonic Detection

Use a power quality analyzer at the PCC to monitor odd - order harmonic content and calculate THD, ensuring compliance with national standards for safe operation in harmonic environments.