Basler BE1-87G Instruction Manual
Also see for BE1-87G: Instruction manual
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BE1-87G - Testing And Setting 5-11I d10004.16× 30.15×200138.830 4.6 × CT ratingInequality (1) is met with CT #2, but not with CT #1. However, since the locked rotor current is only 4.8 timesCT rating [vs. the assumption of 20 times rated for inequality (1)], the application is suitable.SFR = (100/50)*(0.36/0.19) = 3.8Using the SFR 4 column of Table 5-1, a 0.8 ampere setting is indicated. However, based on the noteaccompanying this table, choose the next higher setting of 1.6, because CT #1 has a T classification, and CT#2 has a C classification. The T classification indicates that the CT has significant secondary leakageinductance which somewhat degrades the transient performance. This is a concern during motor startingbecause a slowly decaying offset component develops in at least one phase.Setting Example Number TwoSelect the pick-up setting for the generator application in Figure 5-9. In this application, the settings need to bebased on the probability of significant dissimilar CT saturation during an external fault. Since the generator isresistance grounded, the three-phase fault current will be much larger than the ground fault level. Moreover,the resistor will rapidly dampen any offset-current component. Accordingly, determine the subtransient current(I" d ).Figure 5-9. Generator Differential ApplicationSince the three-phase fault is involved, one-way lead burden is used to determine the total CT burden. Eachphase CT carries just the burden for the lead for that phase.(R t ) 1 = R l + R w = 0.22 + 0.14 = 0.36 ; (Vce) 1 = 50 ; R t < 0.007(Vce) 1 = 0.35(R t ) 2 = 0.09 + 0.10 = 0.19 ; (Vce) 2 = 100 ; R t < 0.007(Vce) 2 = 0.7 |
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