Q21. Which of the following 3-phase connection of a transformer causes interference with the neighbouring communication lines:

Q22. Which type of connection is employed for current transformers for the protection of delta- star connected 3-phase transformer?

Q23. Two transformers connected in open delta supply a 500 kVA balanced load operating at 0.866 power factor lagging. Load voltage is 440 V. kW supplied by each transformer will be

Q24. A T-T transformer can not be parallel with              transformer

Q25. Laminated cores, in electrical machines are used to reduce

Q26. Multistep core is used in transformer mainly to

Q27. Cross over windings are used for

Q28. Concentric windings are used in core type transformer with

Q29. Under normal conditions the dielectric strength of transformer oil is expected to be \(_{-----------}\) for 2.5 mm of gap.

Q30. Which of the following is not a part of transformer installation?