ABB Relion REG670 Product Manual

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Contents

ABB Relion REG670 Product Manual Manual pdf 23 page image

By using optional metering class CT inputsaccuracy of 0,5% can be achieved for steamturbine applications.Negative sequence time overcurrent protection formachines NS2PTOC (46I2)Negative-sequence time overcurrent protection formachines NS2PTOC (46I2) is intended primarily forthe protection of generators against possibleoverheating of the rotor caused by negativesequence component in the stator current.The negative sequence currents in a generator may,among others, be caused by:• Unbalanced loads• Line to line faults• Line to ground faults• Broken conductors• Malfunction of one or more poles of a circuitbreaker or a disconnectorNS2PTOC (46I2) can also be used as a backupprotection, that is, to protect the generator in caseline protections or circuit breakers fail to clearunbalanced system faults.To provide an effective protection for the generatorfor external unbalanced conditions, NS2PTOC(46I2) is able to directly measure the negativesequence current. NS2PTOC (46I2) also has a timedelay characteristic which matches the heatingcharacteristic of the generator 22I t K= as definedin standard IEEE C50.13.where:I2 is negative sequence currentexpressed in per unit of the ratedgenerator currentt is operating time in secondsK is a constant which depends of thegenerators size and designNS2PTOC (46I2) has a wide range ofK settings andthe sensitivity and capability of detecting andtripping for negative sequence currents down to thecontinuous capability of a generator.A separate output is available as an alarm feature towarn the operator of a potentially dangeroussituation.Accidental energizing protection for synchronousgenerator AEGGAPC (50AE)Inadvertent or accidental energizing of off-linegenerators has occurred often enough due tooperating errors, breaker head flashovers, controlcircuit malfunctions, or a combination of thesecauses. Inadvertently energized generator operatesas induction motor drawing a large current from thesystem. The voltage supervised overcurrentprotection is used to protect the inadvertentlyenergized generator.Accidental energizing protection for synchronousgenerator (AEGGAPC, 50AE) takes the maximumphase current input from the generator terminal sideor from generator neutral side and maximum phaseto phase voltage inputs from the terminal side.AEGGAPC (50AE) is enabled when the terminalvoltage drops below the specified voltage level forthe preset time.6. Voltage protectionTwo step undervoltage protection UV2PTUV (27)Undervoltages can occur in the power systemduring faults or abnormal conditions. Two stepundervoltage protection (UV2PTUV, 27) functioncan be used to open circuit breakers to prepare forsystem restoration at power outages or as long-time delayed back-up to primary protection.UV2PTUV (27) has two voltage steps, each withinverse or definite time delay.Two step overvoltage protection OV2PTOV (59)Overvoltages may occur in the power system duringabnormal conditions such as sudden power loss,tap changer regulating failures, open line ends onlong lines etc.OV2PTOV (59) has two voltage steps, each of themwith inverse or definite time delayed.OV2PTOV (59) has an extremely high reset ratio toallow settings close to system service voltage.Generator protection REG670 ANSI 1MRK 502 031-BUS BCustomizedProduct version: 1.2ABB 23