DC High-Voltage Generator Procurement and Usage: A Record of Pitfalls Avoided — Straight Talk

Last month I went to a wind power project site for a technical briefing. The owner's electrical engineer slammed the table and asked: "Doesn't the national standard already say XLPE cables can't be tested with DC? So what did you buy this batch of DC high-voltage generators for?" The several manufacturer sales reps present looked at each other, and no one could field the question. I have to admit, he hit the nail on the head. The DC high-voltage generator (known in the industry as "Zhi Gao Fa") category has had a roller-coaster reputation in the industry in recent years due to the revision of GB 50150-2016 — on one hand, a large number of existing units are still in use; on the other hand, voices saying "the new national standard doesn't allow DC" are everywhere. I've done high-voltage testing for ten years and have been involved in the procurement and model selection of no fewer than fifty DC high-voltage generators. Today's article won't recite manuals or copy encyclopedias. It will stand from the perspective of someone who both buys and uses equipment, and lay out clearly what a DC high-voltage generator can do, what it cannot do, how to choose a model, and how not to be led into a ditch by manufacturer sales talk.

Contents

• 01 What exactly is a DC High-Voltage Generator?
• 02 When it’s the only choice—and when you absolutely shouldn't use it
• 03 The one key formula for model selection
• 04 Real-world case study: Guodian Zhongxing ZGS-300kV/50mA supports the State Grid Anhui Electric Power Research Institute's icing tests
• 05 Standard vs. Intelligent models: Higher price doesn't always mean better
• 06 Debunking the rumor that "the new national standard bans DC testing"
• 07 Delivery acceptance checklist
• 08 FAQ

First, what exactly is a DC high-voltage generator? Its basic operating principle is actually quite straightforward: it takes standard 220V AC mains power and converts it into stable, controllable high-voltage DC through a process involving inversion, voltage step-up, and voltage-multiplier rectification. The equipment consists of two main components—a control unit (main console) and a high-voltage multiplier column (voltage-multiplier cylinder)—connected by an intermediate-frequency cable. The entire system fits into an aluminum alloy flight case, allowing it to be carried by a single person. Output specifications range from 60kV to 300kV, with rated currents varying between 2mA and 10mA. Below is the complete specifications table for the Guodian Zhongxing ZGF series; this is the series frequently used by testing teams across the industry:

Note the pattern in this table: the model number = voltage/current. ZGF-120/5 means 120kV, 5mA. Voltage determines how high a test voltage you can apply; current determines how long a cable you can drive. The weight data tells you whether one person can carry it.

There is an easy trap here — some manufacturers put a 60kV unit and a 120kV unit in the same-sized enclosure, but the internal transformer insulation class is completely different. When reading specifications, don't judge by external size alone. The height and weight of the HV multiplier cylinder are the hard indicators.

II. In These Scenarios, a DC High-Voltage Generator Is the Only Choice — But in Some Scenarios, Never Use One

Scenarios where a DC high-voltage generator must be used:

Surge arrester testing — no alternative. Whether for handover or preventive testing, the measurement of U1mA and the leakage current at 0.75U1mA for zinc oxide surge arresters can only be done with DC. Neither series resonance nor very low frequency (VLF) can replace it. This alone locks the DC high-voltage generator firmly onto every test team's equipment list.

According to Clause 20.0.5 of GB 50150-2016, the measurement of the DC reference voltage and the leakage current at 0.75 times the DC reference voltage for metal oxide surge arresters is a mandatory test item. The standard explicitly stipulates that the leakage current at 0.75 times the DC reference voltage shall not exceed 50μA, and if the ripple factor in the rectifier circuit exceeds 1.5% during testing, a filter capacitor shall be added.

Oil-paper insulated cables. For the large number of oil-paper insulated structures in older cables, DC withstand voltage testing remains a compliant and effective detection method. Many cables in old power plants and mines are still oil-paper insulated, and the annual preventive test still requires a DC high-voltage generator. Clause 17.0.4 of GB 50150-2016 provides explicit calculation formulas and tables for the DC withstand test voltage of paper-insulated cables, and DC withstand voltage testing of paper-insulated cables remains a method recognized by the standard.

DC withstand voltage testing of generator stator windings. Clause 4.0.5 of GB 50150-2016 states it clearly: 1-minute DC withstand voltage testing cannot be avoided in specific scenarios. The test voltage shall be 3 times the rated voltage of the machine, raised in stages of 0.5 times the rated voltage, with each stage held for 1 minute and the leakage current recorded. For hydrogen-cooled machines, there are also mandatory clauses requiring that the test must be carried out before hydrogen filling, and it is strictly prohibited to conduct the test during the hydrogen replacement process.

Scenarios where you must never use it blindly:

XLPE cable handover tests, especially for new projects. This is not a question of "can it be used" — using it could lead to serious consequences. The DC electric field causes space charge accumulation inside XLPE insulation, which "hides" defects — you issue a passing report, and the cable breaks down six months after being energized. No one can bear that responsibility. For 110kV and above XLPE cables, DC is explicitly prohibited. GB/T 11017 and IEC 60840 state this clearly.

Wet weather or dirty surfaces on the silicon stack column. Once the HV multiplier cylinder gets damp, surface leakage will prevent you from raising the voltage to the rated value at all.

III. There is only one core formula for model selection—the primary selection formula: I = C * dU/dt. Here, I is the charging current (mA), C is the capacitance of the test object (μF), and dU/dt is the voltage rise rate (kV/s).

Model Selection Quick Reference Chart – ZGF Series

IV. A Real Case: Guodian Zhongxing ZGS-300kV/50mA Supports Icing Tests for State Grid Anhui Electric Power Research Institute

After covering the theory, let me share a real delivery case. In February 2026, State Grid Anhui Electric Power Research Institute needed to carry out transmission line icing tests — winter cold waves and snowstorms occur frequently, and icing poses a real threat to power equipment. Icing test data directly affects the formulation of the power grid's anti-icing and ice-resistance plans. Their requirements for test equipment were clear: high enough voltage, large enough current, and reliability that could withstand extreme environments.

The final solution delivered was two sets of ZGS-300kV/50mA DC high-voltage generators from Guodian Zhongxing. With a voltage level of 300kV and a rated current of 50mA, this is a large-scale specification among DC high-voltage generators. The HV multiplier cylinder reaches 1250mm in height, and the power output capability of the entire set covers the charging demand for large-capacitance test objects under icing scenarios.

From February 5 to 7, 2026, the Guodian Zhongxing technical team went to the site and completed installation, commissioning, and delivery. During commissioning, they fully calibrated the output voltage and current parameters, repeatedly tested the overvoltage protection, overcurrent protection, and zero-position closing protection functions, and simulated icing test conditions to verify stability. In the end, all indicators of the two sets of equipment met the standards, and they were successfully delivered.

This case illustrates two things:

• First, a specification like 300kV/50mA is not just for show — in scenarios such as icing tests, which demand extremely high equipment capacity and reliability, it is genuinely needed.
• Second, model selection cannot rely only on the parameter table. Whether the manufacturer can customize, and whether they can send people to the site for installation and commissioning, is equally important for large equipment like this.

If we look back at the earlier selection quick-reference table, ZGF-300/5 (300kV/5mA) corresponds to this kind of high-end scenario — it is not suitable for routine 10kV cable inspection, but in special tests at power grid research institutes and large power plants, it is an unavoidable configuration.