IEEE C62.22-1991 pdf download.IEEE Guide for the Application of Metal Oxide Surge Arresters for AC Systems.
1.1 Scope. This guide covers the application of metal oxide surge arresters (see IEEE Std C62.1l-1987 [9]) to safeguard electric power equipment against the hazards of abnormally high voltage surges of various origins. Such overvoltages may cause flashovers and serious damage to equipment and thereby jeopardize the supply of power to users. It is essential to prevent this by the proper coordination of surge-protective devices with the insulation strength of the protected equipment.
The subject is broad, with many ramifications, and it requires a volume of considerable bulk to explain all possible cases in detail. Section 3 of this guide covers the basic cases for stations used to supply and switch electric power transmission, subtransmission, or distribution feeders. Information is included in Section 4 on application of arresters for protection of overhead and underground distribution systems, aU distribution transformers, and other electric distribution equipment.
Step-by-step directions toward proper solutions for various applications are provided. In many cases, the prescribed steps are adequate. More complex and special situations requiring study by experienced engineers are described, but specific solutions may not be given. These procedures are based on theoretical studies, test results, and experience.
2. General Considerations
2.1 Overvoltages. Overvoltages in power systems may be generated by lightning or by system conditions (such as switching operations, faults, load rejection, etc.), or both. Broadly, the overvoltage types will be classified herein as lightning-generated and all others as switching generated. The magnitude of these overvoltages can be above maximum permissible levels and therefore need to be reduced and protected against if damage to equipment and possible undesirable system performance are to be avoided.
2.1.1 Lightning Currents and Overvoltages. Lightning surge voltages that arrive at the tine entrance of a station are caused either by
(1) A lightning flash terminating on the overhead shield wire or structure with a subsequent flashover to the phase conductor (denoted as a backulash) or by
(2) A lightning flash termination on the phase conductor (denoted as a shielding failure).
The lightning surge voltage magnitude and wave shape that enter a station are functions of the magnitude, polarity, and shape of the lightning stroke current, the tower and line surge impedance, the tower footing impedance, and the lightning impulse critical flashover voltage (CFO) of the line insulation. IEEE C62.22-1991 pdf download.