There are not. A fuse is rated in amperes. Power, in watts, is the product of the voltage times the amperage. A fuse protecting a 600 watt circuit can, at one end, be 600 amps in a 1 volt circuit (not likely), or a 1 amp fuse in a 600 volt circuit (somewhat more likely).
Additionally, you do not fuse, say, the output of a klystron outputting 600 watts of microwave energy. The fuse will not be able to interrupt the current, as the RF energy will cause an arc. You place the fuse so as to interrupt the AC supply current into the circuit, or in a DC supply line. High frequencies cause arcing.