Views: 0 Author: Site Editor Publish Time: 2026-09-22 Origin: Site
The most immediate divergence lies in terminology. IEC defines the continuous operating voltage as Uc — the maximum power-frequency voltage the arrester can withstand indefinitely without thermal runaway or accelerated ageing. IEEE uses the term MCOV (Maximum Continuous Operating Voltage) for the same concept. As industry guides note, Uc and MCOV “differ only due to deviations in type test procedures”, meaning the numerical values are often identical, but the verification methods behind them are not.
For a 36 kV (Um) system, the minimum continuous voltage rating follows the rule of thumb Uc ≥ (Um/√3) × 1.05, which for a solidly grounded system yields approximately 21.8 kV. A standard 36 kV-rated arrester typically carries an MCOV of 29 kV, comfortably exceeding this threshold. Rated voltage (Ur) is then derived as approximately 1.25 × Uc, giving a typical Ur of 36 kV for this voltage class.
IEC 60099-4 and IEEE C62.11 classify arrester energy capability using fundamentally different frameworks. IEC employs line discharge classes 1 through 5, which define increasing energy handling demands based on transmission line parameters including surge impedance and peak discharge duration. For distribution-class arresters up to 36 kV, Class 1 or Class 2 is typically specified.
IEEE C62.11 instead classifies distribution arresters by duty level — Light Duty (LD), Normal Duty (ND), and Heavy Duty (HD) — with heavy-duty units offering higher single-impulse energy capability for applications subject to greater lightning or switching surge exposure. Station and intermediate class arresters are further categorized by thermal energy ratings expressed in kJ per kV of MCOV. This structural difference means that a 36 kV arrester meeting IEC Class 1 may not automatically satisfy an IEEE heavy-duty distribution requirement, even though the physical device could be identical.
Temporary overvoltage (TOV) capability represents another area of meaningful divergence. IEEE C62.11 requires a TOV test as a mandatory design test, whereas the IEC approach historically placed greater emphasis on the operating duty test as the primary verification of thermal stability. In practice, manufacturers publish TOV withstand curves showing permissible overvoltage magnitude versus duration — typically 1-second and 10-second ratings. For 36 kV distribution systems, where ground faults or load rejection can produce sustained overvoltages, verifying that the selected arrester’s TOV capability exceeds the maximum expected temporary overvoltage duration is critical. IEEE C62.11-2020 requires arresters to survive 20 operations at rated energy duty without degradation exceeding 10%, a durability requirement that complements the TOV verification.
Configuration practice also differs by region. IEEE C62.22.1-2024 specifically addresses surge arrester installation methods for distribution cable systems up to 46 kV, covering terminal-pole mounting, dead-front equipment, and the role of connection lead length and inductive voltage drop in determining protection margins. In IEC-influenced markets, configuration guidance is consolidated in IEC 60099-5, which provides selection and application recommendations for arresters across all voltage classes.
For 36 kV systems, a practical configuration typically involves polymeric-housed, gapless metal-oxide arresters with a nominal discharge current of 10 kA and an 8/20 µs residual voltage of approximately 90–108 kV peak. Arresters should be installed as close as possible to the equipment being protected, with lead lengths minimized to reduce the inductive voltage drop that degrades effective protection levels.
The IEC and IEEE standards committees have been actively working toward harmonization since at least 2018, with the goal of defining a unified set of test requirements so that one comprehensive test programme can demonstrate compliance with both standards. IEEE C62.11-2020 already shares approximately 80% of its requirements with IEC 60099-4, and a joint dual-logo standard (IEC/IEEE 60099-11) for transmission line arresters is projected for publication in 2027.
For engineers specifying 36 kV arresters today, the practical recommendation is to determine the governing standard from the project’s regulatory environment, then verify that the selected arrester’s MCOV/Uc, energy classification, and TOV capability align with both the standard’s requirements and the actual system conditions. When both standards are relevant, requesting test data demonstrating compliance with both IEC 60099-4 and IEEE C62.11 offers the most robust assurance of performance.
