Presentation Overview• Introduction & objective• LDC & its functions• Load Generation Balance• SCADA system• Southern & Kerala grid• Cascade tripping• Madakkathara s/s details• D.I.P• MiPower software• Special Protection Scheme• Load flow study (peak hours)• SPS implementation• References & conclusion

DESIGN OF SPECIAL PROTECTION SCHEME FOR 315 MVA TRANSFORMER AT

TRICHUR 400KV s/s

By Jerry J Moolan

Nikita Gomez Nirmal S

Sreedevi Prabhakaran

Introduction• Madakkathara 400 kv s/s is an important link in the

Kerala Power Grid, connecting our state to TN grid.

• At present there are two 315 mva, 400/220 kv transformers at Madakkathara, loaded at 75%.

• If one transformer trips, the load on the second transformer goes upto 1.5 times full load value leading to the tripping of that transformer.

• Results in the failure of entire supply at Thrissur s/s and beyond north of it.

LDC; its functions and Load Generation Balance

By

Nirmal S

OBJECTIVE

The project aims at conducting load flow studies to counter the menace of tripping.

Results obtained from the studies are used as inputs for constructing some islanding schemes to prevent the tripping of healthy transformers.

Load Dispatching and its Functions

• LDC is an important link between generation and transmission

• Coordinates the power requirements of the consumers• Power requirement of different consumers differ at

different times• Effective power system management is the key to

exercise proper control over the generation and loads.• This calls for current real time data from all grid system

components.• Strong and reliable communication network required for

data transmission to LDC and system control instructions from LDC.

Requisites of a LDC

• Reliable and far reaching communication network.

• Accurate SCADA system.• Fast data processor and data formatting system.• Reliable power supply 24x7 at LDC.• Visual display systems for data streaming in and

out.• Integrity of efficient engineers well versed in

operations.• Basic amenities, utilities and logistics.

Functions of LDC

• Load generation balance and quality of supply.• Maintenance scheduling of generating units and transmission lines.• Economic load dispatch.• Grid discipline.• Load forecasting or demand estimations.• System security and islanding facility.• Black start preparedness.• Communication and SCADA management.• Energy distribution and load study pattern.• Event analysis and preventive measures.• Coordination with neighbor grids.• Public relations and consumer interaction.

Load Generation Balance• To maintain the frequency at 50z the demand and generation

should balance each other.

• If demand + losses = generation then the frequency is 50hz.

• If demand > generation, frequency is less than 50hz and in case of demand < generation, frequency is more than 50hz.

• Power number of southern grid is around 1000MW.

• Frequency of grid @ 49.5hz implies generation is around 500MW short.

• LGB is one of the important functions of LDC.

• In order to restore this balance, the LDC should control the generation or cut the loads to maintain the frequency of the system at the set standard.

Frequency-Voltage Dynamics

• Frequency is not a local phenomenon, it’s uniform throughout the grid.

• Voltage is a local phenomenon controlled in each node or bus.• Rated voltage is available when reactive power requirement and

supply matches.• If reactive requirement is more than supply, voltage declines from

the rated and if reactive power supply is more than required, voltage exceeds the rated.

• LDC maintains the voltage in the grid by controlling reactive power generation from machines, switching capacitors, charging additional lines etc.

• Over voltage problem can be tackled by switching off some of the transmission lines also.

SCADA and Grid systems

By

Nikita Gomez

SCADA

• It stands for Supervisory Control and Data Acquisition.

• It generally refers to a a computer system

monitoring and controlling a process.• This system is a networked distributed processing

environment consisting of one or more interconnected processing nodes.

• These nodes are configurable in order to meet system requirement.

• It monitors and control HVAC, access and energy consumption.

• Uses different bus architectures in distributed and networking processors and interconnected systems in order to optimize system performance and expandability.

• Distributed system processing permits full capability for inter program control and communication program executing on prime and backup CPUs.

• Supports full access to system files, real time database, and user interface from backup CPUs.

• System can be expandable in both hardware and software to meet future functional or performance requirement.

System components:

• Human-Machine interface (HMI)

• presents data to a human operator

• Helps human operator to monitor and control the process

Supervisory (computer) system :

• gathering data

• sending commands (control) to the process.

Remote Terminal Units (RTUs) :

• connects to sensors in the process

• converting sensor signals to digital data

• sending digital data to the supervisory system.

Programmable Logic Controller (PLCs):

• used as field devices because they are more economical, versatile, flexible, and configurable than special-purpose RTUs.

Communication infrastructure:

• connects the supervisory system to the Remote Terminal Units

The SCADA/Energy Management System (EMS) package under ULDC is designed for providing state of art control centers with hierarchical levels of co-ordination planned in system operation as shown in figure.

Other applications of SCADA:

• manufacturing

• production

• fabrication

• refining

What is a Grid?

A grid consists of generating stations, substations, transmission lines and distribution system with proper interconnection between these systems.

Tie lines connect a a generating station to a substation or a substation to a substation or a generating station to another generating station in a grid.

SOUTHERN GRID

Consists of:

1)Kerala grid,

2)Tamil Nadu grid,

3)Karnataka grid,

4)Andhra grid

5)Pondy & Goa grid.

• Interconnected by tie lines at 440, 220 and 110kv levels.

• All grids except Southern grid, i.e. Northern, Western, Eastern and North-Eastern grid, work in integrated mode.

• While islanding Kerala & TN maybe in integrated mode; Karnataka and TN may be in integrated mode.

• Each state in itself may be in integrated mode if the entire tie lines to that particular state trips.

• Southern grid is interconnected asynchronously to Eastern & Western grids through HVDC lines.

• At 30,000MW evening peak load, Southern grids accounts for 30% of

All-India peak demand, which’s at 1,00,000MW

Kerala Grid

Kerala grid is connected to the southern grid through the following interstate tie lines.

No. Inter State LinesVoltage Levels Connect Kerala to

1 Udumelpet – Thrissur I and II 400 kV Tamil Nadu

2 Madurai – Pothencode I and II 400 kV Tamil Nadu

3 Idukki – Udumelpet I and II 220 kV Tamil Nadu

4 Sabarigiri – Theni I and II 220 kV Tamil Nadu

6 Edamon – Kayathar I and II 220 kV Tamil Nadu

5 Kadakola – Kaniampetta I and II 220 kV Karnataka

7 Mangalore – Konaje I and II 110 kV Karnataka

8 Parassala – Kuzhithura I and II 110 kV Tamil Nadu

Cascade tripping, Madakkathara s/s, D.I.P and

MiPower software

By

Sreedevi Prabhakaran

Cascade Tripping/ Blackout• The phenomenon of tripping of generators

in series is called cascade tripping.

• When a generator trips the frequency will drop and the load will be divided amongst the generators those are working.

• Overload causes the remaining machines to trip resulting in total supply failure in the grid.

• Tripping of generators leads to overloaded tie-lines, causing them to trip too.

• Connectivity to other state grids gets lost in this process, which may even lead to entire southern grid blacking out with major tie-line trips or huge generational losses in the grid.

• Special protection schemes are thus required to safeguard the system as its very hard to restore supply after cascade tripping.

• The other 220KV outgoing tie lines at Madakkathara are

1) Madakkathara-Shornur-220KV line

2) Madakathara-Malaparambu 220KV line and

3)Madakkathara-Arecode 220KV line.

• During evening peak hour the load at Madakkathara is around 800MW.

• The load tripping is intended in the following 110kv feeder at Madakkathara.

1)Madakkathara-Valappadu -110KV feeder

2)Madakkathara-Cherpu – 110KV feeder

3)Madakkathara-Shornur No.1 110KV feeder

and

4)Madakkathara-Shornur No.2 110KV feeder

• In addition to 315 MVA transformer there are 2 No. of 200MVA/110KV transformers at Madakkathara

DIP 5000 [Digital Protection Relay]

• The DIP 5000 provides comprehensive digital tele-protection for power networks.

• Offers highest level of security and dependability. It is easy to install and commission.

• Has the highest level of security and dependability using the latest signaling processing technology and advanced coding algorithm.

• Performs continuous testing of the equipment and communication link, and provides alarm and event recorder files with 1ms accuracy.

• Can be customized to a project’s specific requirements.

• Highly modular and offers extensive monitoring features and a wide range of communication interfaces.

MiPower s/w Tool

• As electric utilities have grown in size, and the number of interconnections has increased, planning for future expansion has become increasingly complex.

• Detailed studies of the system, based on assumptions like, normal and abnormal operating conditions, peak and off-peak loadings, and present and future years of operation to be considered.

• Large volumes of network data must also be collected and accurately handled.

• To assist the engineer in this power-system planning, digital computers and highly sophisticated computer programs are indispensable.

Contd.

• MiPower is one of such indispensable customised program.

• A highly interactive, user friendly windows based Power System Analysis software package.

• Includes a set of programs for performing a range of power system design and analysis study.

MiPower includes the following major power system application programs:

• Load flow

• Short circuit

• Transient stability

• Dynamic stability

• Sub synchronous resonance

• Relay coordination

• Over voltage study

• Network reduction

• Line and Cable parameter calculation

• Long Term load forecasting

• Free Programmable Blocks

Thank You.

SPS, Load flow study and Implementation

By

Jerry J Moolan

Special Protection Scheme [SPS]

A SPS or special protection scheme is a safeguard measure used to maintain Load Generation Balance

in the system, when there is generation failure or overload tripping of power system element.

The common protection schemes are over current relay, earth fault relay, distance protection, differential protection, under frequency protection, df/dt protection etc.

The Talcher Case• Talcher-Kolar HVDC system has SPS implemented in two steps.• In bipolar mode 2000MW is the power transfer capability.

• When a pole trips the capacity is reduced to 1000MW.

• Since there’s a generational loss of 1000MW, there should be equivalent load relief in the grid to maintain the LGB.

• Some protection schemes are employed to trip off 1000MW load in various parts of the southern region.

• Moreover the generation at Talcher is reduced by 1000MW by tripping of one or two machines

• The trip is sensed by a relay and the signal is transmitted to various points by communication channels to trip some radial loads.

SPS requirement at Madakkathara s/s• There are two 315MVA transformers (400/220kv) at Madakkathara.• Almost fully loaded at evening peak hours.• When one of the transformers trips, the other gets overloaded and

trips too.

• Failure of main source at Madakkathara leads the entire load to Lower Periyar- Madakkathara feeder causing it to trip.

• Since all 220kv sources are dead, entire load falls to generators at Kuttiady & Kozhikode leading to blackout.

• Madakkathara s/s limits and entire Northern Kerala blacks out.

• In order to prevent this SPS has to be implemented at Madakkathatra.

315MVA TrFr SPS (local tripping scheme)

Contd.

Local tripping scheme

• When current reaches 1000A in any one of the transformer the overcurrent relay contact is closed.

• This leads to the SPS activating.

• The auxiliary contact of the circuit now gets closed.

• Closing of the circuit leads to the energisation of the trip circuit.

Following feeders are identified for remote tripping using digital protection coupler and carrier inter trip.

SUBSTATION FEEDER NAME PEAK LOAD MW

Palakkad 220kv 110kv Kozhinjampana

110kv Kollenpode

20

11

Shornur 220kv 110kv Panali

110kv Ottappalam

26

38

Nallam 220kv 110kv Kizhissery 46

Kanhirode 220kv 110kv Mundayad #1

110kv Mundayad #2

30

30

Taliparamba 220kv 110kv Payyannur

110kv Cheruvathoor

28

21

The trip signal generated at Madakkathara may be multiplied using a contact multiplier relay & the available signal may be used for local tripping as well as transmitting to other stations.

Project Implementation methodology

• Conducting load flow studies of Kerala Power System in the following cases,

a) At off-peak hours.

b) At day time.

c) At evening peak hours

to find out actual load on 315MVA transformer, when one of them trips.

• Design of SPS at Madakkathara 400kv s/s.

• Conducting load flow studies after the SPS has acted.

• Ascertaining that the design is properly working.

References

[1] S.B. Lele, “Power System Management and Load Dispatch”. Central Techno Publications, Nagpur, India. First Edition: Nov.2003.

[2] PRDC, “MiPower: Design and application”. Power Research & Development Consultants Private Ltd., Bangalore, India. May 1998-99.