Black start in Hydro power Plant and Steam Plant

A black start is the process of restoring an electric power station or a part of an electric grid to operation without relying on the external transmission network.

Normally, the electric power used within the plant is provided from the station's own generators. If all of the plant's main generators are shut down, station service power is provided by drawing power from the grid through the plant's transmission line. However, during a wide-area outage, off-site power supply from the grid will not be available. In the absence of grid power, a so-called black start needs to be performed to bootstrap the power grid into operation.

To provide a black start, some power stations have small diesel generators, normally called the black start diesel generator (BSDG), which can be used to start larger generators (of several megawatts capacity), which in turn can be used to start the main power station generators. Generating plants using steam turbines require station service power of up to 10% of their capacity for boiler feedwater pumps, boiler forced-draft combustion air blowers, and for fuel preparation. It is uneconomical to provide such a large standby capacity at each station, so black-start power must be provided over designated tie lines from another station. Often hydroelectric power plants are designated as the black-start sources to restore network interconnections.

A hydroelectric station needs very little initial power to start (just enough to open the intake gates and the excitation of the generator field coils), and can put a large block of power on line very quickly to allow start-up of fossil-fueled or nuclear stations. Certain types of combustion turbine can be configured for black start, providing another option in places without suitable hydroelectric plants.

Comments

Core type and Shell type Transformers

Constructionally, the transformers are of two general types, distinguished from each other merely by the manner in which the primary and secondary coils are placed around the laminated core. The two types are:- Core type Shell type Another recent development is spiral core or wound core type, the trade name being spirakore transformer. Core type transformer:- In the core type transformer, the windings surround a considerable part of the core. In the simplified diagram of the core type transformer, the primary and secondary winding are shown located on the opposite limbs of the core, but in actual construction they are interleaved to reduce leakage flux. As in the figure, half the primary and half the secondary winding have been placed side by side or concentrically on each limb, not primary on one limb and the secondary on the other. The coil used are form-wound and are of the cylindrical type. In small size core type transformers, a simple rectangular c...

Skin Effect in Conductors

When a conductor is carrying dc current , it is uniformly distributed over the cross section of the conductor . However an alternting current flowing through the conductor does not distribute uniformly, rather it has the tendency to concetrate near the surface of the conductor. This is known as Skin effect. Thus, skin effect is the tendency of an alternting current to concentrate near the surface of the conductor. Due to skin effect the effective area of cross section of the conductor through which current flows is reduced consequently, the resistance of the conductor is slightly increased when carrying an alternating current. Cause of skin effect The cause of skin effect can be easily explained. A solid conductor may be thought to be consisting of a large number of strands, each carrying a small part of current. The inductance of each strand will vary according to its position. Thus, the strands near the centre are surrounded by a greater magnetic f...

Smart Grid

The concept of Electrical grid was given by Nicole Tesla about 120 years ago. Since then the generation, transmission and distribution of Electrical energy has undergone vast changes. Giant size generators and EHV lines are very common now. The per capita consumption has increased manifold (and is still increasing) and consumers demand reliability and quality in Electric supply. The power industry is faced with challenges and opportunity of transforming the Electrical grid into smart grid to manage demand growth, conserve Energy, reduced losses, optimize efficiency, improve power quality and reliability. Smart grid also known as intelligent grid refers to combination of hardware, software and communication tools to meet the above objectives. The main features of a smart grid are: 1. It is self healing from power distuebances. 2. It ensures power quality and reliability. 3. It accommdates centralized giant size generators as well as distributed generation. 4. It uses conven...

Electrical Engineering Home

Search This Blog