Summer Training Report

NHPC - Faridabad

ATraining Report

OnStudy of Hydro Power Plants and Detailed

Design of Large Hydro Generators

Contents

Overview of NHPC Design E & M Division Hydro Power Plants Hydro Turbines Power House Hydro Generators Design Study

About the Software

About NHPC NHPC (National Hydro Power Corporation) A Govt. of India Enterprise

Established in 1975 Started with an authorized capital of Rs. 2000

million, today has an asset value of Rs. 200000million

One of the largest organization for Hydro-Powerdevelopment in India

Has constructed 13 hydro-power projects inIndia and abroad

Total Installed Capacity of 3694.35 MW

Projects completed Baira Siul (MP)

Salal (J&K)

Chamera (Himachal Pradesh)

Dhauliganga (Uttaranchal )

Indira Sagar (MP)

3 X 60

3 X 115

3 X 180

4 X 70

8 X 125

Projects under Construction

Teesta– V (Sikkim) 510 MW

Parbati–II (Himachal Pradesh) 800 MW

Subansiri (Arunachal Pradesh)2000 MW

Chamera-III (Himachal Pradesh)231 MW

DESIGN ( E & M) DIVISION

One of many divisions of NHPC

Deals with the design Electrical &Mechanical components of power plant

Functions of Design E&M

Planning and preparation of Electrical andMechanical design for DPR

Power Potential Studies & Power SystemStudies

Preparation of Technical specification of

E & M equipments

Standardization of Technical specification

Assistance in evaluation of all tenders

Hydro Power Plants Reservoir : Holds the water from the river

Dam : Civil construction

Penstock : Large pipes through which waterFlows from the reservoir to the turbine

Turbine :Turned by the force of water on theirblades

Power Plant : Power generation andtransmission

Generator : Converts mechanical energy ofturbine into electrical energy

Control Gates : Control the flow of water

Types of Hydro Power Plants

Storage Plants

Pumped Storage Plants

Run-of-River Plants

Storage Plants

Impound and store water in a reservoir formedbehind a dam.

During peak demands, enough water can bereleased to meet the additional demand.

Water flow rate may change greatly

May involve dramatic environmentalconsequences including soil erosion, degradingshorelines, crop damage, disrupting fisheriesand other wildlife, and even flooding

Pumped Storage Plants

Reuse water after it is initially used togenerate electricity.

Water is pumped back to the reservoirduring peak-off hours

During peak hours this water is used againfor generating electricity

Run-of-River Plants

Amount of water running through theturbine varies with the flow rate of water inthe river

Amount of electricity generated changeswith seasons and weather conditions

Since these plants do not block water in areservoir, their environmental impact isminimal

Hydro Turbines

Hydro turbines can be classified on thebasis of force exerted by water on theturbine A) Reaction Turbines

Francis Kaplan Propeller Bulb

B) Impulse Turbines Pelton

Hydro Turbines

Type of turbine to be used in a plant isdecided on the basis of available head

Head Range 2m to 70 m Kaplan 30m to 450 m Francis above 300 m Pelton

Also a turbine is characterized by itsspecific speed.

Power House

POWER HOUSE BUILDING CONSISTS OFTHREE MAIN AREAS NAMELY

1. Machine Hall/Unit Bay

2. Erection/Service Bay

3. Control Room/Auxiliary Bay

HEAD CALCULATION

• Avg. Gross Head = MDDL + 2/3(FRL - MDDL) -TWL(4 Units Running)= 203 + 2/3(208 - 203) -184.24

= 22.09 m. • Rated/Net Head = Avg. Gross Head - Head Loss

= 22.09 - 0.75= 21.34 m.

• Max. Gross Head = FRL - min TWL= 208.00 - 181.78= 26.22 m

• Max. Net Head = Max. Gross Head-Head Loss= 26.22-0.75= 25.47 m

• Min. Gross Head = MDDL - TWL(4 Units Running)= 203.00 - 184.24= 18.76m

• Min. Net Head = Min. Gross Head - Head Loss=18.76 - 0.75=18.01 m.

# calculations has been done for PARBATI H.E. PROJECT, STAGE-II

Selection of Machine Speed

Economically should have highestpracticable speed

Deciding parameters :• Variation of head

• Silt content

• Cavitation

• Vibrations

• Drop in peak efficiency

HYDRO GENERATORS

Hydro Generators are low speed salient pole typemachines.

Rotor is characterized by large diameter and short axiallength.

Capacity of such generator varies from 500 KW to 700MW.

Power factor are usually 0.90 to 0.95 lagging. Available head is a limitation in the choice of speed of

hydro generator. Standard generation voltage in our country is 3.3KV,

6.6KV, 11 KV ,13.8 KV, & 16KV at 50 Hz. Short Circuit Ratio varies from 1 to 1.4.

A typical Hydro Generator

CLASSIFICATION

Classification of Hydro Generators can bedone with respect to the position of rotor

(i) Horizontal

(ii) Vertical (two types)

a) Suspension Type

b) Umbrella Type

Suspended Type Vertical Generator

COMPONENTS OF GENERATOR

1. STATOR

Stator Sole Plates

Stator Frame

Stator Magnetic Core

Stator Windings

2. ROTOR

Rotor Shaft

Rotor Spider

Rotor Rim

Rotor Poles

Ring Collectors

Rotor Spider Rotor Rim

3. BRACKETS

Upper Bracket Lower Bracket

4.

GENERATOR

AUXILIARIES

Excitation System

Air Cooling System Braking And Jacking System Bearings

Fire Protection Heaters

Design Study Output equation can be derived by the basic emf equation of a

hydro generator.This has been taken from Electric Machine Design ,AK Sawhney.

Output Equation: Q = C0 * D2 * L * Ns

Where, output coefficient, C0 = 11 * Bav * ac * Kw * 10-3

Q = kVA rating of machine

Bav = specific magnetic loadingac = specific electrical loading

Kw = winding factor

Source: (derived from output equation of AC machines) (Pg-456,Electric Machine Design, AK Sawhney)

Design Study Calculation of Output Coefficient

Is calculated from a graph obtained by analyzing thepublished data of 40 generators in manufacture in USA,Canada, UK, Japan a Europe.

Calculation of Number of Polesusing P=120f/N

Frequency f is 50 Hz as per Indian Standards

Air Gap DiameterDi= (60 * Vr) / (pi * N)

Vr is the Maximum peripheral velocity obtained from agraph between Vr and Number of poles

Design Study Calculation of Stator core length

Stator core length is the gross length of the stator andcan be calculated by using the formula for outputcoefficient

L t= W/ (C0* Di 2 * N)Where,

W = Rated KVA of machineC0 = Output coefficient obtained from curve

N = Rated RPM of the machine

Source : (Fig 1-1, Page 4, Large AC Machines by J.H. Walker.)

Design Study STATOR DESIGNING

Pole pitch is defined as the peripheral distance between twoconsecutive poles. It may be expressed as number of slots, degrees.(electrical or mechanical)

Calculated as : ψ= pi x Di/PWhere Pi (constant) =22/7Di = Air gap diameter in metersP = No. of poles

Flux per poleFlux per pole (φ) =Mean flux density * Pole pitch (ψ)* Length of core

Mean Flux density is assumed to be 0.6-0.7 Wb/m2

Turns per phase = = (1.1 * Vph)/4.44fφ

Design Study Calculation of number of parallel paths

Total current per slot should not exceed 5000 A.

If I be the rated current per phase and there be p parallel pathsthen current per conductor is I/p , and current per slot is 2*I/p

This should not exceed the limit of 5000 A.5000 > 2 * I / p

The value of p greater than or equal to this value, that satisfies otherdesigning constraints is chosen as the appropriate number ofparallel paths.

After the calculation of turns per phase we can calculate theapproximate no. of stator slots.

Design Study

No. of slots is given by,

Ns = (no. of phases) * T ph * (no. of parallel paths) /(turns per coil)Note: Turns per coil = 1 for bar winding

Number of conductor per slots = 2 ( for bar winding)

Design Study Short Circuit Ratio

Defined as the ratio of field currentrequired to produce rated voltage underopen circuit conditions to the field currentrequired to circulate rated current at shortcircuit. Short circuit ratio is the reciprocal ofsynchronous reactance Xd

For salient pole hydro electric generatorsSCR varies from 1.0 to 1.1.