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The power in a 3-phase, 3-wire load is measured using two 100W full-scale wattmeters W1 and W2. W1 is of a accuracy class ± 1% and reads 100 W. W2 is of accuracy class ± 0.5% and reads – 50 W. Then the uncertainty in the computation to total power is
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- ± 1.5%
- ± 0.5%
- ± 4%
- ± 3%
Correct Option: D
W1 = 100W + 1W;
W2 = – 50 + 0.5W
| ∴ W1 + W2 = |  | 50 ± |  | × 100 = ± 3% | |
| 50 |
