Principles of hydro power generation By Ankit Saxena

NHPC Limited • (Formerly known as National Hydroelectric Power Corporation Ltd. ), • A Govt. of India Enterprise, was incorporated in the year 1975 with an objective to plan, promote and organize an integrated and efficient development of hydroelectric power in all aspects. • Later on NHPC expanded its objects to include development of power in all its aspects through conventional and non-conventional sources in India and abroad. • Mini-Ratna Category-I Enterprise of the Govt. of India with an authorized share capital of Rs. 1, 50, 000 Million. With an investment base of over Rs. 3, 87, 180 Million Approx. • NHPC is among the TOP TEN companies in the country in terms of investment. • Presently NHPC is engaged in the construction of 9 projects aggregating to a total installed capacity of 4271 MW.

FEATURES OF HYDRO-POWER PROJECTS • Classification of Hydro-power plant Ø Based on head Low head plant i. e Head < 30 m Medium Head plant i. e Head < 250 m High head plant i. e Head > 250 m Ø Based on type of reservoir Storage Run of the river with pondage Run of the river Ø Based on power generation Base load plant Peak load plant

FEATURES OF HYDROPOWER PROJECTS • Classification of Hydro-power plant Ø Based on Generation capacity Type of scheme Capacity Micro Hydel Plant < 100 KW Mini Hydel Plant < 2000 KW Small Hydel Plant < 15 MW High Capacity Hydel Plant >15 MW Ø Based on type of Turbine Head 18 m or less 18 m to 300 m and above Type Of Turbine Kaplan Turbine Francis Turbine Pelton Turbine

LAYOUT & COMPONENTS DIVERSION STUCTURE POWER INTAKE R E V POWER HOUSE RI ER CH N AN EL W POWER CHANNEL PO FOREBAY R PENSTOCK POWER HOUSE TAIL RACE POOL R E IV

DC Excitation TRCM 220 K 11 KV cooler Pole Cool C Water oo ler Hot water In Gate Water ROTOR Pole GGB Gen Shaft Oil Stator Winding Thrust Pad HS LUB Tur Shaft G V T R A N S F O R M E R G V DT Gate Water

Cross section of layout RESERVOIR Electro-mechanical Equipments • Turbine • Generator • Transformer • Switch Gear • Auxiliary Equipments Dam Surge Tank Intake Head Turbine Race T unne l/cha nnel Tailrace Penstock Main Inlet Valve

Turbine

Types of Turbines Pelton Francis Kaplan

Pelton Turbine • The Pelton wheel is an impulse turbine which is among the most efficient types of water turbines. The Pelton wheel extracts energy from the impulse (momentum) of moving water. Nozzles direct forceful streams of water against a series of spoon-shaped buckets mounted around the edge of a wheel.

Francis Runner • The Francis wheel is an inward-flow reaction turbine that combines radial and axial flow concepts. Francis turbines are the most common water turbine in use today. The Francis turbine is a reaction turbine, which means that the working fluid changes pressure as it moves through the turbine, giving up its energy.

Kaplan Runner • The Kaplan turbine is a propeller-type water turbine which has adjustable blades. The Kaplan turbine was an evolution of the Francis turbine. Its invention allowed efficient power production in low-head applications that was not possible with Francis turbines. The Kaplan turbine is an inward flow reaction turbine.

Generator & Auxiliaries

Turbine Generator Set Rotational Energy Is Converted To Electrical Energy By - Generator Potential/Kinetic Energy Of Water Is Converted To Mechanical Rotational Energy By - Turbine

Types of Generators HYDRO GENERATOR Ø Driven By Water Turbine Ø Rating Up to 750 Mw Ø Speed Range 100 To 1000 Rpm TURBO ALTERNATORS Ø Driven By Steam Turbine Ø Rating Up to 1000 Mw Ø Speed Range Upto 3000 Rpm

Rotor Being lowered

Terms related to Generator • Synchronous reactance is an important parameter of synchronous rotating machine because it affects on the machine output capacity, voltage variation and steady-state stability. • Short circuit ratio It is defined as the ratio of the field ampere – turns required to produce rated voltage on no load to the field ampere turns required to produce rated current on short circuit. It is equal to 1/xd if there were no saturation • Reactive capability The reactive capability (synchronous condenser operation) is the maximum amount of reactive KVA/MVA that the machine can generate when operating at over excited condition at rated frequency and voltage, without exceeding the rated temperature rise. Typical values for hydroelectric machines can be approximated by the equation : k. VAr = (1. 40 – RATED POWER FACTOR) x (RATED k. VA output )

Generator Auxiliaries Damper winding Ø In order to damp out the oscillations, damper winding are used which are housed on the pole shoes/pole faces. Ø It is common practice to specify all hydroelectric machines to have low resistance damper windings. Ventilation & cooling mode Basically two types of cooling are provided: Ø Direct cooling – a winding mainly cooled by coolant flowing in direct contact with the cooled part through hollow conductors, regardless of their orientation, form an integral part of the winding inside the main insulation. Ø Indirect cooling – any winding other than a direct coole 4 d winding

Generator Auxiliaries • Excitation System o Electro-magnetising the rotor with dc supply for building up the voltage in the stator winding. • Governing System o A Governor is a device which adjusts the speed of the machine according to frequency of the grid by matching the guide vane opening & desired output. o The Governing System performs this function through a combination of Electrical, Electronics and hydraulic devices, which include speed sensing, processing, hydraulic amplification and operation of Guide Vane & Runner Servomotors.

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

BUS DUCT

BUS DUCT • Connection from generator to GSU transformer • Tap off connection for UAT & excitation transformer. • Tap off connection for PT & sp cubicle.

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

GSU TRANSFORMER

GSU TRANSFORMERS • • Generator step-up transformers Used for stepping up of generating voltage (MV) to high voltage (HV) for transmission

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

XLPE CABLES

XLPE CABLES Cross linked poly ethylene (XLPE) is a thermosetting compound which has superior resistance to deformation at high temperature. XLPE insulated cable can operate at a maximum continuous temperature of 900 c. Typical use: • Connection between GSU transformers and GIS, and/or • Connection between GIS and potyard equipments

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

GAS INSULATED SWITCHGEAR (GIS) • A totally enclosed switchgear in which SF 6 gas is used as the insulating & arc quenching medium. • Advantages compared to conventional switchgear: • Less space requirement • High reliability • Enhanced safety • Easy maintenance

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

OUTDOOR POTYARD EQIPMENTS

OUTDOOR POTYARD EQUIPMENTS • Capacitive voltage transformers (CVT) • Wave trap • Surge arresters • Lightning spikes • Overhead conductors • Gantry tower Capacitive voltage transformers (CVT): CVT acts as a normal voltage transformer for the measurement of line voltages and also coupling capacitors for PLCC. The main purpose of the coupling capacitor is two fold: o Protection of PLCC terminals from high voltage o Passing the HF signal with minimum attenuation Wave traps: The function of a wave trap is to confine the high frequency current to the outgoing power line and to block Them from the impedance represented by the station equipments like Surge arresters: Surge arrester is a protective device for limiting surge voltages on equipment by discharging or by-passing surge current. It prevents continued flow of follow current to ground, and is capable of repeating these functions as specified.

Potyard Eqipments

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

DC Systems • A direct-current system is used for the basic controls, relaying, SCADA equipment, inverter, communication equipment, generator exciter field flashing, alarm functions, and emergency lights. • The system consists of a storage battery with its associated eliminator-type chargers, providing the stored energy system required to ensure adequate and uninterruptible power for critical power plant equipment. • The battery and battery circuits should be properly designed, safeguarded and maintained, and the emergency requirements should be carefully estimated to ensure adequate battery performance during emergencies.

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

CONTROL MONITORING SYSTEM

CONTROL & MONITORING SYSTEM Major components: • • • The control system consists primarily of a computer-based control system, hard-wired logic or programmable logic, indicating and recording instruments, control switches, protective relays, and similar equipment. The greatest part of this equipment should be grouped at one location to facilitate supervision and operation of the main generating units, transmission lines, and station auxiliaries. The grouping of these controls at one location within the confines of the power plant is termed “centralized control. ”

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

Protection System • Hydro turbine-generators should be protected against mechanical, electrical, hydraulic, and thermal damage that may occur as a result of abnormal conditions in the plant or in the utility system to which the plant is electrically connected. • The abnormal operating conditions that may arise should be detected automatically and corrective action taken in a timely fashion to minimize the impact. • Relays (utilizing electrical quantities), temperature sensors, pressure or liquid level sensors, and mechanical contacts operated by centrifugal force, etc. , may be utilized in the detection of abnormal conditions. • These devices in turn operate other electrical and mechanical devices to isolate the equipment from the system.

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

DG Set • A DG set is a comprehensive system, comprising several parts such as a diesel engine, an alternating current (AC) generator and controls. • It is provided to serve as a source of emergency power as well as during starting of the unit, to supply the essential Unit Auxiliaries and Station Auxiliaries. • It also supplies the Emergency Illumination System, during blackouts and other emergencies.

Other ELECTRICAL AUXILIARIES • • • BUS DUCT GSU TRANSFORMERS XLPE CABLES GAS INSULATED SWITCHGEAR (GIS) OUTDOOR POTYARD EQUIPMENTS DC SYSTEMS CONTROL & MONITORING SYSTEM PROTECTION SYSTEM DG SETS ILLUMINATION SYSTEM

THANK YOU