Ssfcl

Solid State Fault Current Limiter

Project Group Member

Name Enrollment No.

Jariwala Dhaval 090420109001

Topiwala Jaykumar 090420109010

Parmar Ronal 090420109031

Master Chirag 090420109062

Kulkarni Girishkumar 090424109403

Guided By

Prof . Rajesh Prasad

INTRODUCTION :-

• In today circumstance, rapid development of power system network cause the fault current of the system increased greatly .

• The levels of fault current in many places have often exceeded the withstand capacity of existing power system equipment.

• As implication to this matter ; security , stability and reliability of power system will be negatively affected .

• Thus , limiting the fault current of the power system to a safe level can greatly reduce the risk of failure to the power system equipment due to high fault current flowing through the system. Because of that, there is no surprise to fault current limiter (FCL) become a most favourite research since this technology can limit the fault current .

In Present

• Let Assume 7500 KVA be the base KVA ,• % Reactance of generator A on the base KVA = 7*7500/3000 = 17.5%• % Reactance of generator B on the base KVA = 8*7500/4500 = 13.34%• % Reactance of transformer on the base KVA = 7.5*7500/7500 = 7.5%

• Short circuit KVA = (7500 *1090 ) / 11.36 = 66,021 kVA• Short-circuit current = ( S/C kVA) / (√3 * Voltage)

= 66,021 / (√3 * 3300 ) = 11.5506 kA • Rating of C.B = 12kA , 66MVA

Single line diagram of system in figure without FCL

In Future

• Let Assume 7500 kVA be the base kVA ,

% Reactance of generator A on the base kVA = 7*7500/3000 = 17.5%

% Reactance of generator B & C on the base kVA = 8*7500/4500 = 13.34%

% Reactance of transformer on the base kVA = 7.5*7500/7500 = 7.5%

Short circuit kVA = 7500 * 100 / ( 7.3921 ) = 101,459.66 kVA

Short-circuit current = ( 55440) / (√3 * 3300 ) = 17.75 kA

Rating of C.B = 20kA , 100MVA

In Future With FCL

• Let Assume 7500 KVA be the base KVA ,% Reactance of generator A on the base KVA = 7*7500/3000 = 17.5%

% Reactance of generator B & C on the base KVA = 8*7500/4500 =13.34%

% Reactance of transformer on the base KVA = 7.5*7500/7500 = 7.5%

Short circuit KVA = 7500 * 100 / (12.4362) = 60,307.81 KVA

Short-circuit Current = (60,307.81) / (√3 * 3300) = 10.55 KA

Rating of C.B = 12kA , 66MVA

IN PAST WITHOUT

FCL

IN PRESENT WITHOUT

FCL

IN PRESENT

WITH FCL

CIRCUITDIAGRAM

SHORTCIRCUIT

CURRENT(KA)

11.56 17.5 10.50

C.BRATING 12KA ,66MVA 20KA , 100MVA 12KA , 66MVA

At normal state the FCL is expected to :-

1. Have a low insertion impedance2. Able to withstand distribution and transmission level

voltage and current rating3. Have a low voltage drop 4. Have a low power loss

In case of a fault, the FCL is required to :-

1. Be capable of limiting the first fault current peak 2. Large increase of impedance 3. Have an acceptable power loss 4. Tolerate the mechanical stresses 5. Endure the temperature rise 6. Withstand the fault condition for a sufficient time 7. Be capable of fast transition from normal to faulted state and vice versa.

TYPES OF FCL :-

• Depending upon the method used to increase the series impedance, the current limiters can be broadly classified into the major types as,

1. Reactor 2. Super conductors (resistive)

3. Power electronic

Reactor Current Limiters

Bus-BarReactor

G1 G2 G3

Feeder

Super Conducting Current limiters

• These types of current limiters are based on super conducting materials (YBCO, NBCO etc). For super conductors to remain in super conducting state, the conditions to be satisfied include: »The temperature is lower than the limit. » The magnetic flux is lower than the limit. » Current density is lower than the limit.

• When one or more conditions are not met then the conductor comes out of super conduction state and offers high impedance .

Advantages :-

• Distortion only during first cycle.• Size may be small, because HTS performs

limiting action.

• Passive triggering• Re-cooling required.

Disadvantages :-

Power Electronic Current Limiters

• These types of current limiters are based on the use of solid state switches (SCR, GTO, IGBT etc) and are at present limited to applications in low voltage and medium voltage systems.

• The basic principle is to turn off a series connected solid state switch and increase the impedance of the network and effectively limit the fault current.

Solid state fault current limiter ( SSFCL ) :-

Types of solid state fault current limiter :-

1. Resonant circuit current limiters

2. Resistance fault current limiter

1. Resonant Circuit Current Limiters :-

2. Resistance fault current limiter :-

SSFCL advantage :-

• Limited fault current.

• Limited inrush current (soft start), even for capacitive loads.

• Repeated operations with high reliability and without wear-

out.

• Reduced switching surges.

• Improved power quality for healthy lines.

Fault-Current Limiter Applications :-

• Fault-current limiters can be applied in a number of distribution or transmission areas.

1. Generator FCL

2. Feeder FCL

3. Bus-Bar FCL

Generator FCL :-

• Advantages :-1. The fault-current limiter FCL

protects the entire bus.

2. A larger transformer can be used to meet increased demand on a bus without breaker upgrades.

3. I2t damage to the transformer is limited.

4. A large, low impedance transformer can be used to maintain voltage regulation at the new power level.

Feeder FCL :-

• Fault-current limiter in the feeder position. The fault-current limiter FCL protects an individual circuit on the bus.

• The selective application of small and less expensive limiters can be used to protect old or overstressed equipment that is difficult to replace, such as underground cables or transformers in volts.

Bus-Bar FCL :-

• Advantages :-1. Separate buses can be tied together without a large increase in the fault duty on

either bus

2. During a fault, a large voltage drop across the limiter maintains voltage level on the un-faulted bus

3. The paralleled transformers result in low system impedance and good voltage regulation; tap-changing transformers can be avoided

4. Excess capacity of each bus is available to both buses, thus making better use of the transformer rating

Case-study from Iran Power Network :-

• The short circuit analysis of the power network was done based on the actual and future network specifications which have been designed and published by Iran Generation Transmission & Distribution Company.

• This method allows decreasing of 27% in fault current amplitude.

• At the beginning, generating units were separated from each other. But by increasing the electrical demand and in order to increase the system stability and reliability, they gradually became interconnected and more generating units, substations, parallel transmission lines, series and parallel capacitors were installed.

• One of the problems related to the growth of the transmission and distribution of electrical energy system is the fast increase in the short circuit level that may cause the following effects:

i. Overheating the series devices in the fault route.

ii. Producing very high mechanical forces in the transformers, generators and reactors.

iii. Power system stability can be lost depending on the fault current amplitude as well as its clearing time.

iv. Decreasing in reliability of electrical network.

There are generally three solutions to remove those effects:

1. To design power network in a way that probability of occurring a fault be low enough.

2. Using applicable strategies in order to minimize the network damage when a fault occurs.

3. Using fault current limiter depending short circuit current level of each desired bus of power system.

Economical observation

• For this observation, the high voltage substation of FirouzBahram was considered.

• In year 2011 due to increasing short circuit current level, all circuit breaker of this substation must resize and again reinstall.

• Price of C.B of 50KA :-100,000$• Price of C.B of 63KA :-165,000$• Structure civil & reinstalling of

C.B = 3% of total fees• All C.B replaced cost:-

1,700,000$• Price of Plan = 850,000$

• the 850,000$ will be the total price of plan which contains any changing in the actual circuit breakers and using only the combination method as fault current limiter in the best configuration such as one presented in Fig.

• The price of basic components of this plan is as follow as:

– two circuit breakers: 230,000$

– four sectionalizes; 80,000$

– three rectors and three capacitors; 400,000$

– three surge arrestors; 90,000$

• It shows a big benefit for this application. If the substation had less than 12 circuit breakers this benefit achieved to zero and it is more suitable to change all circuit breaker with new ones.

Proposed scheme for Simulation and Hardware

Future Work :-

• We will simulate proposed scheme on MATLAB.

• Later , implementation of Hardware will be based on the simulation results.

References :-

a) Vibhor Chauhan, Rishi Pratap Singh and Seema Dhariwal , “Analysis of fault current limiter (FCL) for voltage sag mitigation through MATLAB and simulink” , Journal of Pune and applied science and techo , pp. 50-58 , Jan 2012 .

b) Hamid Javadi ,” Fault current limiter using a series impedance combined with bus sectionalizing circuit breaker”, Electrical power and energy systems , pp. 731-736 , Jan 2011

c) Vinod Gupta, U. C. Trivedi, N. J. Buch ,” Solid state fault current limiter ” , National Power Electronic Conference ,IIT Roorke, 2010

d) Ram PARASHAR, Christian SASSE, Robin BANKS and Leslie FALKINGHAM AREVA , “ Fault current limiters for transmission & Distribution Network ” , T&D Technology Centre, United Kingdom , pp. 6-9 , June 2006

e) Michael Steurer , Klaus Frohlich , “Current limiter state of art “, 15&16 July 1998