IEEE C62.48-2005 pdf free download – IEEE Guide on Interactions Between Power System Disturbances and Surge-Protective Devices.
2. Normative references
The following rcfernced documents are indispensable for the application of this guidc Fur dated references, only the edition cited applies. For undated references, the latest edition of the rcfrrenced document including any amendments or corrigenda) applies.
ANSI CK4 I (112005), American National Standaisi for Electric Power Systems and Equipment—Voltage Ratings (60 I-Ir).
IEEE Sid C62 41.1 “. IEEE Guide on the Surge Environment in L.ow- Voltage (1000 V and Less) AC Power Cireuita’
3. DefinItions
For the purposes of this guide, the following tcnns and detinitions apply. The Au,hurirarise Dkrionarv of IEEE Standard,. Tr,rni 1F)3I should be refenencted for telnss not defined in this clause.
3.1 nunli,war load: An elecincal load that draws current discontinuously or sshsise impedance vanes during the cycle of the input ac voltage wavcform.
3.2 nonlinear load currant: l.oad currtrnt thai is d:scontinut,wt or is nut pmpwtiunal to the ac soliage.
3.3 power cross: An event in an electrical distribution system where a higher voltage conductor, such as
trurn a transmission line, falls on a lower ssiltage conductor, such as a distribution or secondary line.
4. Power system disturbances
Power system disturbances arc increases or decreases in the system voltage or the power frequency beyond what is considered the nonnal toletaitce (e.g.. a. described by ANSI C84. li). The changes in voltage on the ac mains can range from complete loss (no voltage) for various durations lasting up to seconds. minutes, or even hours to very high-magnitude, short-duration impulses of 50 or more times the normal system voltage lasting for no more than a few millionths of a second, Some of thcsc disturbances can have an undesirable
on the connected equipment, including SPDs. ‘T’he SPDs discussed in this guide are connected to the low-voltage mains (100-1000 V ac), though some ot the disturbances onginate on the high-voltage distribution system. SPDs arc intended to reduce the severity of some power sy.lcin disturbances but can be unable to do anything shoal others
Before discussing the interactions between p(n5’O’ system disturbances and SPDa in detail. thc power system disturbances will be described along with a bricf summary of the interactions Tablc I preucnts a ol’the interactions.
4.1 Surges
Surges are described in IEEE Std C6141.t-2002. They include short-duration, high-energy surges; bursts of high-frequency transient’s; and high-energy, lower-voltage, and lower-frequency shsiurhances due to power-system operations.
Surges can be subdivided into externally generated and internally generated surges. Extensal surges are those surges generated outside a facility and brought into the facility by the utility wires Internal surges are generated within a facility by the uses’s own equipment. External surges are typically more severe hut less frequent than internal surges.
Externally gent-rated surges can result from lightning, power system switching, and operation of overcurrent protective devices (OUPOs), such as circuit breakers, recloaers, and fuses. Lightning surges can result from a direct strike to the power sersice or induced by strikes to nearby lines or to earth. Ftuned power cables are not immune to lightning surges Lightning currents can how along the sheath of a buried cable and induce voltages on the csinshictors within the cable- Wires inside a plastic conduit are also subject to induced voltages that might be capable of damaging vulnerable equipment Capacitor switching can also generate s’siltage surges in the secondary supply system
Internally generated surges typically result from switching inductise or capacitive loads. They can also result from an OCPI) opening in an inductive circuit. The operation of an SN) can also result in internal surges.
SPDs are intended to reduce surge voltages by conducting the surge currents to neutral, gnmurid. sir to another phase. In the process, there is voltage division with the impedance of the rest of the current path:
hence, there is less surge voltage at the point of connection of the SP[) than there would he without the SN). SPDs absorb some surge energy and dissipate it in the form of heat (a gas tube or an air gap would absorb very little energy) They are typically intended to do this for surges ranging in duration front less than I palo 10 ms. Surges outside the specified capability of the SPD might damage or destroy the SN).
4.2 Swells
SwelLs might result from switching operations in the utility distribution system, power switching from one source to another, intermittent loss of a neutral connection, a phase-to-ground fault, such as a flaslioser of an insulator ott one phase of a multiphase system, or possibly a higjt-soltage conductor contacting a low- voltage conductor A phase-to-ground fuulh on an ungrounded three-phase supply sy-ssem can result in the soltage of the unfaulted phases increasing to 1.91 times the normal amplitude (13 times the nominal phase- to-neutral voltage plus nominal sysaent tolerance), and in extreme cases, for up to several seconds. In a multiple ground system (typical in North America), it is extremely unlikely that the phase voltage will esceed I .35 tinses nominal voltage for overhead systems and I .45 tints’s nominal voltage for underground distribution (8131.
A swell can result from sw-itching a heavy load quickly from one power wince to another. An example of this is a load with motors switched from a standby generator to commercial power. IEEE C62.48 pdf download.