Answer:

Introduction:
Pelton turbine is a type of impulse turbine used for generating electricity. It works on the principle of impulse force of a high-velocity jet of water striking the buckets of the turbine. The pressure inside the Pelton turbine casing plays a crucial role in its operation.

Explanation:
The pressure inside a Pelton turbine casing during working remains constant. This can be explained based on the following points:

1. Working Principle:
The Pelton turbine consists of a wheel or rotor with a series of double-cupped buckets evenly spaced around its circumference. Water is supplied to the turbine through a nozzle, which forms a high-velocity jet. The jet of water strikes the buckets, causing the rotor to rotate.

2. Impulse Force:
The high-velocity jet of water possesses kinetic energy. As the jet strikes the buckets, the water imparts its kinetic energy to the buckets, thereby transferring the impulse force. This force causes the rotor to rotate.

3. No Change in Pressure:
The pressure inside the Pelton turbine casing remains constant during the working of the turbine. This is because the turbine casing is designed to be airtight and water-tight. It is responsible for enclosing the entire turbine assembly, including the rotor and buckets.

4. Conservation of Energy:
The constant pressure inside the turbine casing ensures that the energy of the water jet is efficiently transferred to the buckets. The pressure remains constant as the water flows through the turbine and exits the casing. This ensures that there is no loss of energy due to changes in pressure.

5. Constant Energy Conversion:
The constant pressure inside the turbine casing allows for a consistent energy conversion process. The kinetic energy of the water jet is converted into mechanical energy as the rotor rotates. This mechanical energy is then further converted into electrical energy through the connected generator.

Conclusion:
In conclusion, the pressure inside a Pelton turbine casing remains constant during its working. This constant pressure ensures efficient energy transfer and consistent energy conversion, resulting in the generation of electricity.