Solving Field Challenges in DC Withstand Voltage Testing for Photovoltaic And Energy Storage Projects
Publish Time: 2026-08-25 Origin: Site
In large-scale ground-mounted photovoltaic power plants and energy storage system projects, the quality of DC withstand voltage and leakage current testing directly affects grid connection nodes, equipment lifespan, and asset safety. However, field conditions often differ significantly from the ideal conditions in the manual. Commissioning engineers frequently encounter practical challenges such as electromagnetic noise from inverters, high temperatures and sandstorms in deserts and Gobi, and the confined working space of energy storage containers. The correct deployment and operation of equipment directly determine the reliability of test data and field safety.
ZGF series includes multiple specifications and models. This article takes the ZGF-60kV/2mA DC high-voltage generator as an example. This model is the mainstream equipment recommended for new energy field testing, with complete original factory accessories, and is suitable for most DC withstand voltage testing scenarios in photovoltaic and energy storage projects. This article analyzes the typical operating challenges of new energy power plants based on the hardware characteristics of this split-type equipment, shares key points for field operation, and helps engineers fully utilize equipment performance to ensure test safety and data reliability.
Testing Challenges Brought by New Energy Power Stations
The core of a DC high-voltage generator is to output a stable and controllable DC high voltage. However, new energy power stations can easily disrupt the two key conditions of "stability and measurability."
High-Frequency Harmonics and Electromagnetic Interference
The DC side of photovoltaic power plants is not a pure DC environment. String and centralized inverters generate a large number of high-frequency switching harmonics, which are conducted along the cables and interfere with the test circuit, causing continuous fluctuations in leakage current readings. In most cases, this is not due to equipment failure, but rather insufficient anti-interference measures in the test circuit. Once the leakage current reference drifts, the insulation condition judgment loses its basis; when performing leakage current-voltage trend analysis, noise will mask the true signal, causing deviations in test conclusions. When using the ZGF-60kV/2mA, strict implementation of grounding and shielding can significantly suppress the disturbance of harmonics to the microammeter readings.
Two Extreme Operating Conditions: Desert and Container
Ground-mounted photovoltaic power stations are mostly located in deserts and tidal flats, where summer surface temperatures exceed 45°C, accompanied by sandstorms. Coastal projects also face salt spray corrosion. The ZGF-60kV/2mA is a split-type structure, including a main frame, high-voltage multiplier cylinder, microammeter, discharge rod, current-limiting resistor, various connecting cables, fuses, and other complete accessories. On-site wiring for multiple components is required. Dust and severe temperature differences can affect the insulation of the multiplier cylinder; therefore, protective measures are necessary to prevent abnormal output alarms.
The internal aisles of the energy storage container are narrow, allowing only one person to pass sideways. With proper layout planning, the ZGF-60kV/2mA can fully perform withstand voltage tests on the DC cables inside the container.
Key Points for On-site Operation of ZGF-60kV/2mA
▎Rated operating ambient temperature: -10℃ ~ +40℃; relative humidity ≤85% (non-condensing) at 25℃; rated load allows continuous operation for 30 minutes.
Handling Dust and Thermal Stress
ZGF-60kV/2mA voltage multiplier rectifier unit has a sealed structure, but windblown dust and salt spray can still corrode the external insulation surface.
Store the voltage multiplier cylinder and microammeter properly before and after testing to prevent dust accumulation and surface creepage;
Avoid prolonged withstand voltage tests at midday temperatures exceeding 40°C; if unavoidable, provide shade and shorten the pressurization time;
Do not apply rated load for extended periods when the ambient temperature is below -10°C or above 40°C.
Proper protection measures will maintain stable leakage current and output voltage, minimizing test interruptions.
Compact Layout Scheme for Energy Storage Compartment in Confined Spaces
The core of energy storage compartment operations is rapid entry and exit, and safe wiring. Practical strategies include:
Placing the voltage multiplier at a ventilated location near the compartment door, and placing the main unit frame in a safe area outside the door, eliminating the need for the entire unit to enter the compartment;
Using the shortest possible high-voltage lead wire, keeping cables straight to minimize bending and dragging; the four-core control cables are also routed with shorter lengths;
Connecting the grounding wire to the nearest grounding point on the container shell, and pre-positioning the discharge rod and current-limiting resistor;
One person operates the main unit outside the compartment, while personnel inside only perform wiring confirmation. All personnel must evacuate the container during the pressurization phase.
This scheme avoids the risks of high-voltage cable compression and accidental contact, allows for rapid relocation after single-circuit testing, and improves the efficiency of multi-battery compartment testing.
Noise Suppression to Ensure Microammeter Measurement Accuracy
In environments with strong electromagnetic interference, the reliability of inverter readings depends on the grounding and shielding process:
All grounding wires must be fully connected; omissions are strictly prohibited.
High-voltage circuits must be kept away from the inverter's power cables.
Four-core signal cables must not be bundled with high-voltage or power cables.
When conditions permit, temporarily shut down the inverter in the adjacent circuit under test to reduce on-site noise.
Following these procedures ensures stable and reproducible microammeter readings, providing a reliable basis for insulation assessment.
Key Points for Safety Protection Operations in Energy Storage Testing
The DC side of the energy storage system is directly connected to the battery cluster. Fault currents generated by flashover breakdown can damage the battery modules and BMS sampling board. When using the ZGF-60kV/2mA surge arrester, the following must be observed:
Before testing, ensure the **discharge rod and current-limiting resistor are intact.** Do not conduct withstand voltage tests if any parts are missing.
In the event of a flashover, immediately adjust the voltage to zero, disconnect the input power supply, and use the discharge rod with the current-limiting resistor to fully discharge the test object multiple times before contacting the object under test.
If conditions permit, prioritize disconnecting the battery cluster and the cable under test to block the flow of fault energy to the battery at its source.
Practical Points for Surge Arrester Testing
According to IEC 60099-4 requirements, zinc oxide surge arresters for photovoltaic power plants need to be tested for leakage current at a DC reference voltage and 0.75 times the reference voltage. The ZGF-60kV/2mA surge arrester does not have a 0.75U automatic range; testing must be completed manually by adjusting the voltage.
1. Read the DC reference voltage Uref from the surge arrester nameplate and calculate in advance: U0.75 = 0.75 × Uref ;
2. Slowly increase the voltage to Uref and record the leakage current;
3. Decrease the voltage to U0.75, and read the leakage current after the voltage stabilizes;
4. Test to zero and disconnect power, then fully discharge using a discharge rod;
5. For batch testing, pre-calculate parameters, increase the voltage slowly and evenly, and record the readings only after they have completely stabilized.
Grid Connection Compliance Requirements
Acceptance of new energy projects has shifted from "test passed" to data traceability and process auditability. IEC 60060-1, IEEE 400.2, and IEC 60099-4 clearly define the specifications for DC withstand voltage and surge arrester testing.
When conducting tests using the ZGF-60kV/2mA, engineers must simultaneously and completely record the test voltage, microamp leakage current, withstand voltage duration, and protection action information, creating paper or electronic test records to meet the data submission requirements of the owner, power grid, and third-party auditing agencies.
DC withstand voltage testing for photovoltaic energy storage places higher demands on equipment operation and on-site protection. The ZGF series of split-type DC high-voltage generators, represented by the ZGF-60kV/2mA, offers complete original factory accessories, mature and reliable performance, and is suitable for most photovoltaic and energy storage on-site tests
Mobile/Whatsapp/Wechat: +86 15123029885
→To learn more about our products, please click here.