List one advantage and one disadvantage of one wattmeter method.
Advantages:
1) Only one wattmeter is used.
2) Less number of connections.
3) Cost required is less.
Disadvantages:
1) Used only for 3- Φ balanced load and not for unbalanced loads.
2) Star point must be accessible for connecting the Pressure coil.
3) Delta connection must be opened to connect current coil.