The electrical outlet and power plug type D are widely used in India and Nepal. It is the British Standard 546, which means it was the standard power used in Great Britain before 1947.
Type D plugs have three round pins, arranged in triangular patterns.
The center earth pin has a diameter of 7.1 mm and a length of 20.6 mm. The other two pins have a length of 14.9 mm and have 19.1 mm space between them.
The middle of the imaginary line between the power pins and the grounding pins has a center-to-center distance of 22.2 mm.
The type D plug is used along with the type M plug, which has larger pins in India.
Typically both plugs are used for large appliances and can fit in the socket of the same type. A socket that can accommodate the type D plug most likely can contain the type M plug.
Type D plugs bear similarity to type C plugs. Although the distance between the prongs of a type C plug (17.5-18.6 mm) is closer than that of the type D plug, type C plugs can fit into a type D outlet.
This is as a result of the elasticity of the pins, which does not extend to its base.
The inelasticity of type C plugs at the base and the fact that type C pins are longer than type D’s makes attachment to the receptacle loose.
This can lead to sparks, and in certain cases, short-circuit.
Combining type C plugs with a type D outlet can be unsafe but still feasible in use. Using type E and F plugs with type D outlets is far more unsafe; in fact, it’s dangerous.
Type E and F plug pins are about 19 mm apart compared to 19.1 mm of type D.
This means type E and F plugs can be forced into type D receptacle, even without the presence of flexible pins like type C.
When type E and F are fitted into a type D receptacle, they would not be grounded as they should, this leading to a lot of sparking circuit breaking.
Type D outlets are designed for type D plugs with pins of 14.9 mm in length.
Type E and F pins have 19 mm length, do when they are forced into a type D receptacle, about 4.1 mm of the pin would be exposed, thus leading to the risk of electrocution.
With type C, that risk is eliminated as the prongs are eliminated.
Type D plugs are widely used in India and Nepal, but type D outlets can be found in the UK.
If you stumble across a type D outlet in the UK, do not plug anything into it, as it most likely has a special purpose.
Type D plugs are one of the most dangerous, as their pins are not insulated; thus, the risk of electrocution exists if the plugs are pulled halfway.
Also, the outlets are not recessed, thus eliminating protection from live pins.