IEEE C62.22A-2013 pdf download IEEE Guide for the Application of Metal-Oxide Surge Arresters for Alternating-Current Systems Amendment 1: Supplement to Consider Energy Handling Capabilities
2. Normative references
Add the following to Clause 2:
IEEE Std C62.11TM-2012, EEE Standard for Metal-Oxide Surge Arresters for AC Power Circuits (> 1 kV).
4.General considerations
Delete the three paragraphs of the existing 4.2.5 preceding 4.2.5.1. Insert the new 4.2.5, 4.2.5a, and4.2.5b before 4.2.5.1:
4.2.5 Energy handling capability
When a metal-oxide surge arrester (MOSA) is subjected to a surge from the system to which it is installedit responds by shunting surge current thereby limiting the overvoltage on the protected equipment. Theaction of the arrester results in the transfer of charge and in the absorption of energy from the system.which is rapidly converted to heat. The charge transfer is quantified as coulombs and the energy absorptionis quantified as joules. Both types of arrester durability (energy absorption and charge transfer) are testedfor each arrester design to allow arrester users to compare the capability of the arrester with therequirements of the system. The energy absorption capability is characterized by the switching surgeenergy rating test. The charge transfer capability is characterized by the single impulse withstand ratingtest.
When metal-oxide arresters are energized at steady state. valve elements will conduct leakage current atlow levels, which is converted into heat at a low rate. Under these normal operating conditions (i.e.absence of overvoltage), there is a balance between the heat generated by the valve elements and the headissipated by the arrester through conduction, convection, and radiation, such that a stable operatingcondition is maintained. Overvoltage and surge cvents disturb this stable condition by causing the valytelements to absorb increased levels of energy for some limited amount of time. The subsequent responseand temperature rise of the arrester depends greatly on the mmagnitude and rate of energy input and on thespecific design of the arrester.
For simple applications where overvoltages are well defined, the resulting energy absorbed by the arrestelcan be determined by calculation (use arrester minimum voltage characteristics for energy calculation). Forcomplex situations, computer simulation studies using electromagnetic transient simulation software mayye required. These studies require knowledge of the arrester minimum and maximum voltage-currentcharacteristics, which are usually available from the arrester manufacturer. With these types of studies, theswitching surge energy rating (energy absorption) and single impulse withstand rating (charge transfer) asstated by the manufacturer can be compared to the requirements of the system.
4.2.5a Switching surge energy rating
This station and intermediate class arrester characteristic is related to the energy absorption capability ofthe arrester. Typical switching surges can last for a few milliseconds to many milliseconds and in somecases can arrive at the arrester one or more cycles apart. This rating quantifies the maximum energy anarrester is capable of absorbing and remain thermally stable after the event with ac voltage applied.