Sepam - HV/MV Protection and control units (ENG) - Trinet

Directional earth fault (cont’d)Commissioning, settingEarth fault current is measured:c by a CSH core balance CT through which 3 phaseconductors pass and which directly detects the sumof the 3 currents. This solution is the most accurateone,c by a 1A or 5A current transformer, using a CSH30interposing ring CT which acts as an adapter.c by the phase CTs. The measurement is obtainedby taking the internal vector sum of the three phasecurrents.c by a core balance CT with a ratioof 1/n (50 i n i 1500) using the ACE 990 interface.It becomes falsified when the CTs are saturated.Saturation may be due either to overcurrent or to thepresence of a DC component in a transformer inrushcurrent or in a phase-to-phase fault current.Residual voltage is measured by:c 3 voltage transformers. The measurementis obtained by taking the internal vector sumof the three phase voltages,c 3 voltage transformers with secondary windingsconnected in an open delta arrangement.Check:c the connections,c the positions of the microswitches SW1 associatedwith the current and voltage inputs,c the general parameters in the status menu.Set the following using the pocket terminal:c Iso current: Iso is set in rms, amps or kiloamps.The 999 kA setting may be used to inhibit theprotection: all the outputs are set to 0.c characteristic angle θo,c T time delay: T is the operation time delay.The θo setting depends essentially on the earthingsystem:v ungrounded: the earth fault current is capacitive.The recommended setting is θo = 90°,v resistive neutral: the protection should only detectresistive earth fault current and should not besensitive to capacitive current. The recommendedsetting is θo = 0°,v solidly grounded: the earth fault current is onlylimited by the cable and source induction coils.The recommended setting is θo = -45°.Characteristicscharacteristic angle θosetting (3) 0°, 15°, 30°, 45°, 60°, 90°, -45°accuracy (1) ±5°Iso set pointsettingresolution0.05 Ino i Iso i 10 Ino (2) expressedin ampsusing CT sum 0.05 In to 10 Inwith CSH core bal. CT2 A rating 0.1 A to 20 Awith CSH core bal. CT30 A rating 1.5 A to 300 Awith CT + CSH30 0.05 In i Iso i 10 In (0.1 A min)with core bal. CT+ ACE 990 0.05 Ino i Iso i 10 Ino (2) (0.1 A min.)accuracy (1) ±5%inhibition0.1 A or 1 digit999 kAdrop out/pick-up ratio (93.5 ±5)%T time delaysettingaccuracy (1)resolutionϕo measurement50 ms i T i 655 s±2% or -10 ms to 25 ms10 ms or 1 digitmeasurement range 0° to 359°accuracy (1) ±2°resolution 1°characteristic timesinstantaneous tripping timetime delayed tripping timememory time timefault recognition timereset time20 ms < t < 65 msT< 40 ms< 40 ms< 40 msoutputs available for control logicinstantaneous F50X/1 for normal zone 1 i X i 2F50X/3 for inverse zonetime delayed F50X/2 for normal zone 1 i X i 2Please note:When several directional earth fault protections areincluded in the same Sepam 2000, the characteristicangle setting is common.remote reading, remote setting* (4)function code F5050hidentification number X (5)F50X/4 for inverse zoneparameters Iso set point unit : 0.1 x A(order of parameters) characteristic angle unit : degreeT time delayunit : 10 x ms(1)in reference conditions (IEC 60255-6).(2)Ino = In if the sum of the three phase currents is used for the measurement.Ino = sensor rating if the measurement is taken by a CSH core balance CT.Ino = In of the CT is the measurement is taken by a 1 A or 5 A current transformer.Ino = core balance CT rating if the measurement is taken by a core balance CT other than CSH.(3)this setting is common to both modules.(4)the data formats are defined in the manuals which describe each communication protocol.(5)the number of protection function modules depends on the type of Sepam 2000.* function available as of version 9802 SFT2800.2/14 Protection functions