DC High-Voltage Generator Procurement Survey: Why 80% of Power Testing Labs Purchase the Wrong Specifications

Last month, the team leader of the testing department at a municipal power supply company contacted me. The ZGF-120/2 DC high-voltage generator they purchased six months ago frequently triggered overload protection during 35kV cable DC withstand voltage tests. The equipment came from a reputable manufacturer, and the specifications met national standards. So where was the problem? It wasn’t that the equipment was faulty; it was that the selection logic was completely wrong.

There is a peculiar phenomenon in the procurement of power testing equipment: the error rate in selecting DC high-voltage generators is particularly high. This isn’t due to technical complexity, but because procurement decision-makers fall into the misconception that “the higher the voltage, the better,” while forgetting the most critical questions: What is your test subject? What are the specific requirements of your testing standards? How frequently will you use the equipment?

• Voltage Rating Matching: An 80kV unit is suitable for testing power equipment rated at 35kV or below.
• Current Capacity Limitations: A 5mA current is suitable for small-capacity test specimens; high-capacity cables require 10mA or higher.
• Test Type Restrictions: Primarily used for DC withstand voltage and leakage current testing; cannot perform AC withstand voltage testing.

In plain terms: The ZGF-80/5 is simply an “adjustable high-voltage power supply.” Z stands for DC, G stands for high voltage, F stands for generator, 80 represents the maximum output voltage of 80 kV, and 5 represents the maximum output current of 5 mA. Its function is to perform a “health check” on power equipment—by applying DC high voltage to verify whether the insulation performance meets standards.

But here’s a key point to understand: a DC high-voltage generator is not a universal device; it has a clearly defined scope of application:

If you need to test 110 kV transformers, long-distance high-voltage cables, or perform AC withstand voltage tests, the ZGF-80/5 is simply not suitable. In such cases, you should consider the ZGF-200/5 or a series resonance test set.

• Substations at 35kV and below: Routine preventive testing, acceptance testing
• Distribution equipment testing: 10kV/35kV cables, switchgear, current transformers, surge arresters
• Small and medium-sized power companies: Annual testing volume of 50–200 test items, moderate usage frequency
• Power construction companies: Acceptance testing after cable installation
• Electrical equipment manufacturers: Factory testing, quality inspection

• 110kV and above substations → Requires ZGF-200/5 or higher
• Long-distance high-voltage cable testing (>5km) → Requires higher current capacity (10mA or above)
• AC withstand voltage testing required → Should consider a series resonance test set
• Annual testing volume → Consider leasing or third-party testing services
• Budget → Consider used equipment or simplified configurations

Having reviewed hundreds of DC high-voltage generator procurement proposals, I’ve identified a pattern: the more a buyer focuses solely on voltage parameters, the more likely they are to fall into a trap. True decision-making should consider these 5 dimensions:

• Output Voltage Stability: National standards require ≤1%, but in practice it should be ≤0.5%. Key Consideration: Excessive voltage fluctuations can cause measurement errors in leakage current, affecting the accuracy of test conclusions.
• Ripple Coefficient: Should be ≤1.5%; high-quality equipment is ≤1%. Important Note: Excessive ripple can interfere with microampere meter readings, especially during low-current testing.
• Overcurrent Protection Response Time: Note: Slow response may damage the test specimen or the equipment itself.
• Temperature Drift: Should be ≤0.1%/°C. This parameter is critical for on-site testing where ambient temperature varies significantly.

• LED Display vs. LCD Screen: Does not affect test results; LCD screens are more expensive.
• Remote control range: The standard 10-meter range is sufficient; a 100-meter range is rarely needed for everyday use.
• Data storage function: Most organizations have their own independent test management systems, so the device’s built-in storage is rarely used.
• Bluetooth/Wi-Fi connectivity: Strong electromagnetic interference at the test site makes wireless connections unstable and introduces additional points of failure.

• Fixed voltage rating: 80 kV is the upper limit; cannot test 110 kV equipment
• Limited current capacity: 5 mA is unsuitable for high-capacity test objects (e.g., long cables, large transformers)
• DC testing only: Cannot replace AC withstand voltage test equipment
• Strict environmental requirements: Temperature -10°C to 40°C, humidity <85%; derating required at high altitudes

1. Compile a list of testing requirements: List all equipment types, voltage levels, and annual testing volumes that need to be tested.
2. Review relevant standards: Specific requirements for DC withstand voltage tests in standards such as GB/T 16927 and DL/T 474
3. Obtain quotes from at least 3 suppliers: Request detailed configuration lists and compare core component brands
4. Visit existing users: Contact organizations in your industry that have already purchased the equipment to understand their actual user experience
5. Confirm calibration services: Consult local metrology institutes or third-party calibration agencies to verify calibration capabilities and costs
6. Calculate the total 5-year cost: Purchase price + 5 years of calibration fees + maintenance costs + potential spare part costs

If you have completed all the above steps and are still torn between a particular brand or model, the issue may not lie with the equipment itself, but rather with the fact that your requirements are not yet clear enough. Often, clarifying your requirements is more important than selecting the equipment.