LV generator protection - engineering site - Schneider Electric

In shortVia the Micrologic releases of theMasterpact and Compact NS circuitbreakerranges, Schneider hastaken into account the specificfeatures of the set generators.These devices perform:b the essential protection functionsb additional monitoring functionssuch as measurement of relevantproper operation parametersb connection functions, …This switchgear guaranteesoptimised continuity of supply foroperators.The Schneiderprotection solution4 .1. Micrologic and generator protectionWith respect to generator protection, the Micrologic releases of the MasterpactNT, NW and Compact NS ranges allow optimised settings for fine generatorprotection.4.1.1. Long Time Delay protection of the “InverseDefinite Minimum Time Lag” type of phases (3)The Micrologic P and H include in the microprocessor the various IDMTL typecurves. These curves of variable slope are used to enhance:b discrimination with fuses placed upstream (HV) of the power circuit-breakerb co-ordination with the MV protection relays that may be of the IDMTL typeb protection of specific applications.Five slopes are proposed:b definite Time DTb standard inverse time SIT, curve in i0.5tb very inverse time VIT, curve in itb extremely inverse time EIT, curve in l2tb high voltage fuse HVF, curve in i4tThe slope is calculated as per the formula:( ) .()Tr =time delay bandB = type of curve DT, SIT, VIT, EIT, HVFFor the various time delay bands and slopes, the tripping thresholds in secondsat 1.5 lr are as follows:E89636time delay 0,5 s 1 s 2 s 4 s 8 s 12 s 16 s 20 s 24 sbandDT 0,5 1 2 4 8 12 16 20 24SIT 3,2 6,4 12,9 25,8 51,6 77,4 103 129 155VIT 5 10 20 40 80 120 160 200 240EIT 14 28 56 112 224 336 448 560 672HVF 159 319 637 1300 2600 3800 5100 6400 7700b intermittent overloads and IDMTL slopesAs long as the circuit-breaker remains closed, the intermittent overloads aretaken into account to simulate their effects on the conductors. This functionoptimises the circuit-breaker tripping time.29