Ppt power grid design

Department of Electrical Engg.SIET,Dhenkanal.

Synergy Institute of Engineering & Technology,Dhenkanal

Seminar on

Power Grid Design

Submitted by

Susanta Das 7th Semester B.Tech

Reg.No-0901230234

Seminar Guide Mr. A. Panda

Department of Electrical Engg.SIET,Dhenkanal. 2

Outline of Presentation Introduction Need of Power Grids Selection Site Layout Design 1.Busbar Schemes

2.Electrical Layout Drawing3.Bill of Material

Safety Clearance in Grid Design of Earth Mat Control Room Switch/Relay Room Grid Equipments Conclusion ReferenceDepartment of Electrical Engg.SIET,Dhenkanal.

INTRODUCTION

An electrical grid is an interconnected network for delivering electricity from suppliers to consumers. It consists of three main components; 1) power station that produce electricity from combustible fuels or non-combustible fuels; 2) transmission lines that carry electricity from power plants to demand centers; and 3) transformers that reduce voltage so distribution lines carry power for final delivery.


WHY WE NEED GRID? Improvement of

Reliability Improvement of

economics Improvement of

efficiency Imrovement of power

quality Improvement of

security & safety Controller of entire

power system


SELECTION OF SITE Selection of site for construction of a Grid Sub Station is

the first and important activity. This needs meticulous planning, fore-sight, skillful observation and handling so that the selected site is technically, environmentally, economically and socially optimal and is the best suited to the requirements

The site should be:- As near the load centre as possible. Easily accessible to the public road to facilitate transport

of material Above highest flood level (HFL) so that there is no water

logging. Sufficiently away from areas where police and military

rifle practices are held. Free from master plans / layouts or future development

activities to have free line The should be far away from AirportDepartment of Electrical Engg.SIET,Dhenkanal.

REQUIREMENT OF LAND / AREA:- The site should have sufficient area to properly

accommodate the Sub Station buildings, structures, equipments, etc. and should have the sufficient area for future extension of the buildings and / or switchyard.

The requirement of land for construction of Sub Station including staff colony is as under:

S.No. Voltage Class of GSS

Required Area

1 400 20.0 Hectare

2 220 6.0 Hectare

3 132 3.5 Hectare


Layout Design-Bus bar Schemes

The commonly used bus bar schemes at Sub Stations are:

Single bus bar. Main and Auxiliary

bus bar. Double bus bar. Double Main and

Auxiliary bus bar One and a half

breaker scheme.


Single bus bar:- This is the simplest switching

scheme in which each circuit is provided with one circuit breaker.

This arrangement offers little security against bus bar faults .

The entire Sub Station is lost in case of a fault on the bus bar.

In case of maintenance of circuit breaker, the associated feeder has also to be shutdown.

Main and Auxiliary bus

Bar:- This is technically a single bus

bar arrangement with an additional bus bar called “Auxiliary bus”.

As in the case of single bus arrangement, due to the fault the entire substation is lost.

This bus arrangement has been extensively used in 132 kV Sub Stations.


Double Bus Bar In this scheme, a double bus bar

arrangement is provided. Each circuit can be connected to either one of these bus bars through respective bus bar isolator.

Bus coupler breaker is also provided so that the circuits can be switched on from one bus to the other on load.

This scheme suffers from the disadvantage that when any circuit breaker is taken out for maintenance, the associated feeder has to be shutdown

This Bus bar arrangement was generally used in earlier 220 kV sub stations.

DOUBLE MAIN AND AUXILIARY BUS BAR ARRANGEMENT

The limitation of double bus bar scheme can be overcome by using additional Auxiliary bus,.

The feeder is transferred to the Auxiliary bus during maintenance of its controlling circuit breaker without affecting the other ckt.


One & A Half Breaker Arrangement In this scheme, three circuit

breakers are used for controlling two circuits which are connected between two bus bars. Normally, both the bus bars are in service.

A fault on any one of the bus bars is cleared by opening of the associated circuit breakers connected to the faulty bus bar without affecting continuity of supply. Similarly any circuit breaker can be taken out for maintenance without causing interruption.

Load transfer is achieved through the breakers and, therefore, the operation is simple.

The breaker and a half scheme is best for those substations which handle large quantities of power and where the orientation of out going.

This scheme has been used in the 400 kV substations.


Electrical Layout Drawing



List of Material The lists of material are only typical and cover the general

requirement. Any other equipment / structure / material which may be required for

construction of Sub Station as per layout and other requirements and not included in the above

typical lists of




Safety Clearance The various equipments and associated / required facilities have to be so arranged within the

substation that specified minimum clearances are always available from the point of view of the system reliability and safety of operating personnel. These include the minimum clearances from live parts to earth, between live parts of adjacent phases and sectional clearance between live parts of adjacent circuits / bays. It must be ensured that sufficient clearance to ground is also available within the Sub Station so as to ensure safety of the personnel moving about within the switchyard.

As per Rule 64 (2) of the Indian Electricity Rules, 1956, the following safety working clearances shall be maintained for the bare conductors and live parts of any apparatus in any Sub Stations, excluding over head lines of HV and EHV installations:

Nominal system Voltage in (kv)

Highest System Voltage in(kv)

Lighting impulse Level(KVp)

Switching Implulse Voltage in (KVp)

Minm Clearance Betn Phase &Earth(mm)

Minm clearance Betn Phases(in mm)

Safety Clearance(mm)

Ground Clearance(mm)

11 12 70 ---- 178 229 2600 3700

33 36 170 ---- 320 320 2800 3700

132 145 550650

---- 11001300

11001300

37003800

46004600

220 245 9501050

---- 19002100

19002100

43004600

55005500

400 420 1425 1050(Ph-E)1575(Ph-Pb)

3400----

----4200

6400 8000

765 800 2100 1550(Ph-E)2550(Ph-Pb)

6400----

----9400

10300 13000

Earth Mat Design Provision of adequate earthing system in

a Sub Station is extremely important for the safety of the operating personnel as well as for proper system operation and performance of the protective devices.

The primary requirements of a good earthing system in a Sub Station are

a):-The impedance to ground should be as low as possible but it should not exceed 1.0 (ONE) Ohm.

b):- The Step Potential, which is the maximum value of the potential difference possible of being shunted by a human body between two accessible points on the ground separated by the distance of one pace (which may be assumed to be one metre), should be within safe limits.

c):- Touch Potential, which is the maximum value of potential difference between a point on the ground and a point on an object likely to carry fault current such that the points can be touched by a person, should also be within safe limits.


Cont.The details of the earthing material generally used in a sub station are given below:

Design of Control Room

The control room is the main command centre of the substation. The entire operation of the site is monitored and controlled from this central location.

A control room may range from a small, seldom manned, non-ventilated room to a large, air conditioned area containing numerous staff members and electronic equipment (PCs, control panels/consoles, electrical and electronic switching devices, under floor cabling, etc.).


Design of battery Room The Battery Room houses lead acid or

nickel cadmium batteries for uninterrupted power supply (UPS) to the substation.

In power grid normally 110 no. of batteries are present, having each capacity of 2.1V to maintain 220V output & the specific gravity of liquid is 1.835.

Power House FCBC are designed to supply continuous power to the DC load and simultaneously charge the batteries connected. Input supply form 415V. AC 3 Phase or 220V. AC 1 Ph. is converted to regulated DC. The charger has two independent systems.

Normally the DC Power is supplied to he load by the Float Charger. It also supplies trickle current to the battery to keep it healthy. If the charging current under Float Mode exceeds a set level.Boost charger is switched ON. It supplies Quick charging current to the battery. On battery reaching the set value the Boost Charger is switched OFF.


Design of Switch/Relay Room The Switch Room

accommodates high density of electronic equipment housed in cabinets and automated switch-gear. In-cabinet equipment maintain the primary functions of the facility and form the switching interface between the Control Room and the field equipment. The area may also accommodate a significant amount of metering and logging equipment. Due to the high volume of critical electronic equipment, it is essential that a fire event be detected before the operation of the plant is compromised.


Grid EquipmentsLighting Arrestor It is an instrument that

protect vital equipments in the grid

when a lightning strikes a power transmission line, the induced high voltage travels along the line towards both ends; this arrester will bypass this high voltage to the ground so that the nearby transformer will not be damaged.

Line Volt.(KV)

L.A.Rating(KV)

400 327

220 180

132 108

33 27

CVT:- It is that type tfr which is used

to measure potential It is the major advantage of

PT, & also used for carrier communication, which replace the coupling capacitor.

At first for carrier communication a coupling capacitor is used with a PT, which is costlier than CVT.

It act as a high pass filter.

Connection diagram of CVT

Potential transformer:-

Potential Transformer or Voltage Transformer are used in electrical power system for stepping down the system voltage to a safe value which can be fed to low ratings meters and relays. Commercially available relays and meters used for protection and metering, are designed for low voltage.

Current Transformer:-

A current transformer is used in high voltage circuits where it is not possible to measure current directly.

A CT is a step up transformer with only one turn in primary. There will be as many cores based on the purposes like metering, protection etc.

The secondary of a CT should never be kept open circuited because very high flux will be developed in the secondary and hence it may be damaged.

Power TRANSFORMER It is a static device which

transforms electrical energy from one ckt to another ckt without change of frequency, but changing voltage with the principle mutual induction.

Most of the power transformer are in MVA ratings.

It is the most costlier equipments in the grid.

INSULATOR:- Insulators are used to

prevent flow of current from conducting material to non conducting material.

It should be mechanically strong & high dielectric strength.

Each insulator rating is of 11kv to 16kv.

Wave Trap:-It is the combination of inductance & capacitance, which act as a low pass filter, which passes low frequencies in to the grid, & this frequency is used in the grid.The Line trap offers high impedance to the high frequency communication signals thus obstructs the flow of these signals in to the substation bus bars. If there were not to be there, then signal loss is more and communication will be ineffective/probably impossible.

Circuit breaker:- It is protective equipments in

the grid. It is the automatic on load

switch. There are of 5 medium type of

circuit breaker., but SF6 ckt breaker is used for best.

Isolators:- This is an off load switching

device to used open or close for flow of current or not to flow respectively in the grid.

Conclusion:- Grid is the nodal point of the

entire power system. It has two objectives i.e.1:

Supply Quality Power, 2:Supply the power from source to load with an economic reasons.

AS Grids are interconnected so, there is an improvement of reliability of can achieved.

As grid is the nodal point, if it fails to work, then entire power system will fails.

Grid efficiency is lower i.e. 50-70%.

As Grid has too many equipments so, design of grid is too costlier.

Reference:- Construction Manual for substations by Shreemat Pandey

Chairman & Managing Director Jaipur Rajasthan Rajya Vidyut Prasaran Nigam Ltd.

Albert, R., Albert, I., and Nakarado, G. L. (2004). Structural Vulnerability of the North American Power Grid. Physical Review E 69 025103(R). 1-4 pgs.

Grid Manual of OPTCL. http://www.powergridindia.com

Dept of Electrical Engg. 33

Business

Ppt power grid design