difference between quick and ultra rapid blow fuse ?

[nour]

what is the difference between quick and ultra rapid blow fuse ?

which is better for 220v plug?

[wraper]

which is better for 220v plug?

There is no better. There is a right thing to use depending on the load it protects.

[nour]

which is better for 220v plug?

There is no better. There is a right thing to use depending on the load it protects.

ok it's a standard 13 amps 220v (250v) bs1363 plug , that was the second half of the question 

[nour]

to be Clearer, the plug is for generic use

[mmagin]

Aren't there fuses which are specifically safety approved for use in bs1363 plugs?

[ade]

Just use a standard fuse conforming to BS 1362, which has its own speed requirements.  The fuse is there to protect the cable, not to protect the load or appliance. 

Appliances / devices which are very sensitive to shorts tend to have one or more additional fuses in them already.  Plus there is another fuse in the fuse box.

[Gyro]

You've said nothing to indicate that the ultra rapid fuse has a high enough fault current interrupt rating. Use a standard BS 1362 conforming fuse as ade says.

[wraper]

which is better for 220v plug?

There is no better. There is a right thing to use depending on the load it protects.

ok it's a standard 13 amps 220v (250v) bs1363 plug , that was the second half of the question 

There is a special fuse type for this. Usual fuses won't fit there because of the different dimensions.

[wraper]

There are two common misconceptions about the purpose of the fuse in a BS 1363 plug, one is that it protects the appliance connected to the plug, and the other is that it protects against overloading. In fact the fuse is there to protect the flexible cord between the plug and the appliance under fault conditions[47][48] (typical British ring circuits can deliver more current than appliance flexible power cords can handle). BS 1363 plugs are required to carry a cartridge fuse,[49] which must conform to BS 1362. Post-War Building Studies No. 11, Electrical Installations included the recommendation that Provision should be made in the plug for the accommodation of a cartridge type of fuse for 13 amps., and alternatively, for 3 amps. Fuses of these ratings should be interchangeable and be readily identified.[50] The original BS 1363:1947 specified fuse ratings of 3 A, 7 A and 13 A.[51] The current version of the fuse standard, BS 1362:1973, allows any fuse rating up to 13 A, with 3 A (coloured red) and 13 A (coloured brown) as the preferred (but not mandated) values when used in a plug. All other ratings are to be coloured black.
Plugs when supplied separately from any appliance should be available with either a 3 A or 13 A fuse fitted. The fuses are mechanically interchangeable; it is up to the end user or appliance manufacturer to install the appropriate rating.
BS 1362 specifies sand-filled ceramic-bodied cylindrical fuses, 1" (25.4 mm) in length, with two metallic end caps of 1/4" (6.3 mm) diameter and roughly 1/5" long. The standard specifies breaking time versus current characteristics only for 3 A or 13 A fuses.
For 3 A fuses: 0.02–80 s at 9 A, < 0.1 s at 20 A and < 0.03 s at 30 A.
For 13 A fuses: 1–400 s at 30 A, 0.1–20 s at 50 A and 0.01–0.2 s at 100 A.

[SeanB]

Quick blow and ultra quick blow fuses are meant to be installed inside the final equipment. The plug fuse must be the BS1362 approved type, to protect the cable against burning in case of a short in the appliance.

The quick blow fuse is typically used to protect resistive loads and is not recommended for use with switching power supplies, electric motors and such as to get the inrush rating the fuse rating is way above what will protect. They are only there for things like impedance protected transformers and motors, those small ones where the short circuit current in the secondary or the stalled rotor current is only a small amount over standard full load current, where the fuse provides protection. Also used on the secondary to protect against overcurrent, but not where inrush current is too high.

Ultra quick blow is used to protect semiconductor devices, where it has the possibility of protecting a rugged power semiconductor, likely a power transistor or power diode, against an overcurrent condition, or to clear the overcurrent in case of a short across the output. There it might blow faster than the power device, though in many cases it will not be faster than the fusing silicon.