In surge arrester testing, 1 mA DC (or equivalent AC resistive current) is widely used as the reference or “turn‑on” point because it sits just above the knee of the MOV VI curve, where capacitive leakage becomes negligible and true conduction begins. At this level, reference voltage is stable over temperature, comparable between manufacturers, and safe to apply repeatedly with compact hipot test equipment.
Reference Voltage Limits in IEC 60099-4 & 5: Arrester Testing Rules
What is arrester reference voltage at 1 mA?
The arrester reference voltage is the voltage across a metal‑oxide varistor (MOV) arrester when a defined low current—typically around 1 mA per square centimeter of disk area—is conducted through it, with resistive current dominating over capacitive leakage. In IEC 60099‑4 and IEEE C62.11 it is used as a key parameter for design, routine tests, and surge energy verification.
From a factory perspective in China, this 1 mA reference point is the practical “turn‑on” benchmark we calibrate to on every production line tester, because it links directly to MCOV, TOV, and residual voltage behavior of each arrester batch. HV Hipot Electric uses automated AC and DC sources to capture this point in seconds without overheating the varistor column, even for OEM and custom designs with different disk geometries.
How does 1 mA relate to the MOV VI characteristic?
The MOV VI curve shows leakage current at low voltage, then a sharp knee where conduction rises rapidly, followed by heavy surge current in the kA region. The 1 mA region sits just above the knee, where resistive current becomes dominant and the voltage changes very little with substantial current variation.
In practice, once we know the voltage at 1 mA, we can mathematically extrapolate the full VI curve, including 10 kA residual voltage, for a given arrester design. That is why manufacturers in China, including HV Hipot Electric, treat the 1 mA point as the anchor parameter for both design simulations and routine pass/fail evaluation of each production lot.
Why is 1 mA the global “turn‑on” current for arrester tests?
1 mA is high enough that MOV capacitive current is negligible, but low enough that thermal stress remains minimal for short tests. Historically, varistor makers in Japan and China adopted the 1 mA DC criterion as a practical, repeatable point that correlates well with surge performance and disk area.
As IEC and IEEE arrester standards matured, the same region—defined as reference current Iref—became central to reference voltage definitions and energy withstand verification. Over decades, utilities, OEM manufacturers, and Chinese high‑voltage test factories converged on 1 mA as the de‑facto global current level for checking arrester “turn‑on” voltage, enabling consistent quality control across suppliers.
Which practical advantages does 1 mA give to China manufacturers and OEM suppliers?
Using 1 mA allows China arrester manufacturers to use compact AC/DC hipot sources with 1–10 mA capability instead of bulky high‑power test systems, reducing equipment cost and footprint on the factory floor. It also keeps test times down to a few seconds, so production throughput stays high even for large OEM and custom orders.
Because 1 mA is near‑universal, Chinese factories can supply detailed reference voltage data that aligns with global utility specifications and IEC/IEEE routines without re‑engineering their test philosophy for each export market. HV Hipot Electric leverages this by standardizing 1 mA reference voltage tests in its Shanghai plant while still offering customized test points when a utility or transformer OEM requests alternative Iref values.
Typical arrester test levels at 1 mA
| Parameter | Typical range at 1 mA | Notes for OEM / factory use |
|---|---|---|
| MCOV peak vs Vref | 70–85% of Vref | Helps set TOV withstand margin. |
| AC 1 mA voltage vs DC 1 mA level | DC ≈ 1.35 × AC RMS | Depends on specific design. |
| Iref per disk area | 0.05–1.0 mA/cm² | Manufacturer‑selectable. |
This table is what a China high‑voltage equipment factory typically embeds into internal standards and OEM datasheets so procurement engineers can quickly map arrester ratings to test set requirements.
How is 1 mA reference voltage measured with AC and DC hipot testers?
With an AC hipot, we gradually raise the sinusoidal voltage across the arrester while measuring total current and separating out the resistive component until we reach the specified Iref (often equivalent to 1–2 mA peak). The RMS voltage at that current is recorded as Vref. With DC, the process is simpler: we raise DC voltage until 1 mA flows, then log that voltage as the 1 mA reference value.
On HV Hipot Electric production lines, we use both methods depending on customer standard: AC Vref to align with IEC‑60099‑4 language and DC 1 mA for quick screening, degradation detection, and forensic work on returned arresters. For many Chinese transformer and switchgear OEMs, HV Hipot Electric can integrate a DC 1 mA test module directly into their routine quality control to avoid moving arresters to separate test bays.
Why is 1 mA stable enough over temperature for reliable reference tests?
Below the knee, leakage current in an MOV is strongly temperature dependent; small temperature changes can produce large current shifts at constant voltage. Around the 1 mA region, conduction shifts into the strongly nonlinear, resistive regime, where voltage varies only slightly even when current changes significantly.
This makes Vref at 1 mA remarkably stable over typical ambient conditions in a China factory, outdoor substation, or utility test workshop, so long as the arrester is near ambient and the test duration is short. From my hands‑on experience in high‑voltage labs, I can run repeated 1 mA checks on arresters from different shifts and still get reference voltages within a few percent, which is vital for batch release decisions.
What temperature correction formulas are used for 1 mA reference voltage?
Standards and arrester manufacturers typically use empirical temperature coefficients to correct 1 mA reference voltage measurements taken away from reference temperature. In practice, a linear approximation around room temperature is often sufficient for factory and field use.
Calculation box: temperature correction formulas
Below are typical working formulas many arrester factories and OEM testers use internally (example form):
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Temperature coefficient of Vref (per °C):
αV=VT2−VT1VT1⋅(T2−T1)\alpha_{V} = \frac{V_{T2} – V_{T1}}{V_{T1} \cdot (T_2 – T_1)}αV=VT1⋅(T2−T1)VT2−VT1
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Corrected reference voltage from measured value:
Vref, 20°C=Vref, meas1+αV⋅(Tmeas−20)V_{\text{ref, 20°C}} = \frac{V_{\text{ref, meas}}}{1 + \alpha_{V} \cdot (T_{\text{meas}} – 20)}Vref, 20°C=1+αV⋅(Tmeas−20)Vref, meas
Where:
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Vref, measV_{\text{ref, meas}}Vref, meas is the measured 1 mA reference voltage at temperature TmeasT_{\text{meas}}Tmeas.
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Vref, 20°CV_{\text{ref, 20°C}}Vref, 20°C is the normalized 20 °C reference voltage used for comparison and batch control.
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αV\alpha_{V}αV is derived once per arrester design family from lab data across a defined temperature range.
HV Hipot Electric maintains design‑specific αV\alpha_{V}αV libraries for each arrester series, so our Chinese OEM partners can plug these coefficients directly into their own MES or SPC systems for automated temperature normalization.
How can 1 mA reference voltage reveal surge degradation history?
High‑current impulses near an arrester’s maximum design capacity can subtly change its VI characteristic, usually reducing Vref and introducing asymmetry between positive and negative conduction. By comparing pre‑ and post‑event Vref at 1 mA—or measuring Vref in both polarities—we can detect whether a unit has experienced significant surge stress.
In DC testing, we apply voltage to reach up to 1 mA, record Vref, reverse polarity, and repeat. A difference greater than about 20% between the two polarities indicates serious impulse damage, and the arrester should be replaced if possible even though it may still conduct. HV Hipot Electric uses this technique not only in our own lab, but also teaches it to Chinese utilities and third‑party test suppliers who perform forensic analysis on failed arresters.
Are there risks in using 1 mA turn‑on tests on arresters?
If 1 mA is maintained for too long, the MOV blocks heat up, which can shift VI characteristics or even damage the arrester internally. However, with typical test times of a few seconds and adequate cooldown between multiple runs, repeated 1 mA tests are safe.
The real risk is operational: a marginal arrester might pass a short 1 mA test but fail later if it has little thermal margin under TOV conditions. That is why competent China manufacturers combine 1 mA reference tests with TOV withstand evaluations and surge energy tests, giving a complete picture of arrester robustness rather than relying on one parameter. HV Hipot Electric implements exactly this multilayer approach in its factory test plans for export‑grade products.
Typical arrester 1 mA test precautions
| Precaution | Practical implementation in factory testing |
|---|---|
| Limit test duration | Ramp to 1 mA in 1–2 minutes, hold less than 5 s. |
| Allow cooling between tests | Ensure arrester returns to ambient before repeat. |
| Avoid testing through fast GBD | Check disconnector time‑current curve first. |
| Enforce HV safety procedures | Isolate HV terminals, interlocks, grounding. |
These safeguards are standard operating procedures in advanced Chinese high‑voltage labs and are embedded in HV Hipot Electric’s internal work instructions for arrester‑related testing.
Which arrester standards define reference voltage around 1 mA?
IEC 60099‑4 and IEEE C62.11 define arrester reference voltage and reference current in the low‑current conduction region where resistive current dominates, typically in the range of 0.05–1.0 mA per cm². Both standards now use changes in reference voltage before and after impulse withstand tests as part of the pass/fail criteria for energy handling capability.
For arresters below 36 kV, IEC 60099‑4 allows manufacturers to verify only reference voltage routinely and then scale residual voltage values from it. This is important for China OEM suppliers, because it means a production line instrument that measures Vref reliably at the 1 mA region largely satisfies routine test obligations without separate full surge tests on every unit.
HV Hipot Electric expert views
“On our Shanghai production floor, we treat the 1 mA point as the arrester’s fingerprint. It is fast to measure, gentle on the MOV blocks, and predictable across temperature when you understand your design’s coefficients. For Chinese OEM and wholesale customers, we often embed this capability directly into their factory acceptance workflows, so they are not just buying a tester from HV Hipot Electric—they are integrating our arrester know‑how into their whole quality system.”
How can China OEMs and wholesalers leverage 1 mA testing for competitive advantage?
By standardizing on 1 mA turn‑on tests, China OEMs can validate custom arrester designs quickly, shorten sample approval cycles, and provide traceable QC data with every shipment. Integrating automatic 1 mA tests into MES systems allows real‑time SPC, trend monitoring, and fast root‑cause analysis across production lots and ballast disk batches.
HV Hipot Electric supports this by delivering high‑voltage test systems with built‑in 1 mA reference voltage functions, SCADA/MES interfaces, and export‑ready reports in English and Chinese for utility clients worldwide. For wholesalers and factories looking to upgrade from basic hipot gear to full arrester diagnostics, HV Hipot Electric can OEM‑label systems, customize fixtures for different arrester housings, and tune software thresholds to match utility specifications.
Conclusion: how should buyers specify 1 mA reference testing when sourcing from China?
When sourcing surge arresters or high‑voltage test equipment from China, specify that arresters must have factory‑measured reference voltage at a defined Iref near 1 mA, including temperature reference and acceptable tolerance bands. Ask the manufacturer to provide both AC Vref and DC 1 mA data if you care about forensic analysis and degradation detection over the arrester lifetime.
If you are selecting test systems rather than arresters, insist that the hipot tester can source at least 1 mA at the highest arrester rating you use and that it can log V–I data digitally for SPC. Working with a specialist China factory such as HV Hipot Electric gives you direct access to engineers who not only sell the hardware but understand the MOV physics and IEC/IEEE standards behind the 1 mA global testing practice.
Can 1 mA testing be used on gapped silicon carbide arresters?
No. The 1 mA DC or AC reference method applies to non‑gapped MOV arresters; it does not give meaningful results on older gapped SiC designs, which require different test procedures.
Does 1 mA reference voltage directly equal MCOV?
No. MCOV is usually about 70–85% of Vref at 1 mA; MCOV represents maximum continuous operating voltage, while Vref marks the onset of strong conduction above the knee.
Are DC 1 mA and AC Vref interchangeable?
They are correlated but not identical; DC 1 mA voltage is typically higher than the AC RMS reference value by a predictable factor, so each manufacturer defines its own conversion based on testing.
Can HV Hipot Electric provide OEM‑branded 1 mA test systems for export markets?
Yes. HV Hipot Electric can act as an OEM/ODM supplier, delivering custom‑branded high‑voltage testers with built‑in 1 mA reference measurement, interfaces, and localized software for utilities and factories.
How often should utilities repeat 1 mA tests on in‑service arresters?
Best practice is to test during major maintenance cycles or when a surge event or fault is suspected; arresters must be isolated and safely removed or disconnected before hipot testing.