LV generator protection - engineering site - Schneider Electric

E88738Setting exampleWhat is the overload-protection threshold of aCompact NS400 circuit breaker equipped withan STR23SE (or STR23SV) trip unit setto Io = 0.5 and Ir = 0.8 ?IoIr.8 .9 .9 .93.7 1 .88 .95.63.85 .98.5.8 1x Inx IoAnswerIn x Io x Ir = 400 x 0.5 x 0.8 = 160 A.The identical trip unit, with identical settings butinstalled on a Compact NS630 circuit breaker, willhave an overload-protection threshold of:630 x 0.5 x 0.8 = 250 A.Fault indicationsA LED signals the type of fault:b overload (long-time protection) or abnormal internal temperature (> Ir)b short-circuit (short-time protection) or instantaneous (> Isd)b earth fault (if earth-fault protection option installed) (> Ig)b microprocessor malfunction:v both (> Ig) and (> Isd) LEDs ONv (> Ig) LED ON (if earth-fault protection option (T) installed).Battery powered. Spare batteries are supplied in an adapter box. The LEDindicating the type of fault goes OFF after approximately ten minutes to conservebattery power. The information is however stored in memory and the LED can beturned back ON by pressing the battery/LED test pushbutton. The LEDautomatically goes OFF and the memory is cleared when the circuit breaker isreset.TestA mini test kit or a portable test kit may be connected to the test connector on thefront to check circuit-breaker operation after installing the trip unit or accessories.The test pushbutton tests the battery and the (% Ir), (> Ir), (> Isd) and (> Ig)LEDs.Self monitoringThe circuit breaker trips if a microprocessor fault or an abnormal temperatureis detected.OptionsFour options are available:b earth-fault protection Tb ammeter Ib zone selective interlocking ZSIb communications option COM.trip units STR23SE (U y 525V) STR53UE (U y 525V)STR23SV (U > 525V) STR53SV (U > 525V)ratings (A) In 20 to 70 ° C (1) 150 250 400 630 150 250 400 630circuit breaker Compact NS400 N/H/L b b b - b b b -Compact NS630 N/H/L - - - b - - - boverload protection (Long time)current setting Ir = In x … 0.4...1 0.4...1adjustable, 48 settingsadjustable, 48 settingstime delay (s) fixed adjustable(min.…max.) at 1.5 x Ir 90...180 8...15 34...50 69...100 138...200 277...400at 6 x Ir 5...7.5 0.4...0.5 1.5...2 3...4 6...8 12...16at 7.2 Ir 3.2...5.0 0.2...0.74 1...1.4 2...2.8 4...5.5 8.2...11short-circuit protection (Short time)pick-up (A) Isd = Ir x … 2...10 1.5...10accuracy ± 15 % adjustable, 8 settings adjustable, 8 settingstime delay (ms) fixed adjustable, 4 settings + "constant I 2 t" optionmax. resettable time y 40 y 15 y 60 y 140 y 230max. break time y 60 y 60 y 140 y 230 y 350short-circuit protection (instantaneous)pick-up (A) Ii = In x … 11 1.5...11fixedadjustable, 8 settingsprotection of the fourth poleneutral unprotected 4P 3d no protection no protectionneutral protection at 0.5 In 4P 3d + N/2 0.5 x Ir 0.5 x Irneutral protection at In 4P 4d 1 x Ir 1 x Iroptionsindication of fault type - b (standard)zone selective interlocking ZSI - b (2)communications COM - b (2)built-in ammeter I - b (2)earth-fault protection T - b (2)(1) If the trip units are used in high-temperature environments, the setting must take into account the thermal limitations of the circuit breaker. The overloadprotection setting may not exceed 0.95 at 60° C or 0.9 at 70° C for the Compact NS400, and 0.95 at 50° C, 0.9 at 60° C or 0.85 at 70° C for the Compact NS630.(2) This option is not available for the STR53SV trip unit.55