20ladr-ieema

LADR AN INNOVATIVE CONCEPT FOR POWER SYSTEM

STABILITY.

P.K. Pattanaik

Deputy Manager

E&MR Division, OPTCL, BURLA-768017

Synopsis:-

Availability of

electrical power with proper

quality has become an

essential commodity for any

utility that deal power system

network. Reliability is an

important aspect for the study

of electrical power system. So

to maintain quality and

reliable power, any

utility/company should secure

a competitive electrical

equipment to accommodate

the rapidly changing

situations. Progressive

deregulation of market,

complexity of industrial

processes and upcoming

demand of load in the network

system have also compelled

and necessitated the utility for

the introduction of

sophisticated protection

schemes that can employ a

quick response to the fault

occurrences.

Many utilities use

interconnected tie lines,

ring main network etc.. to

enhance the system

reliability and stability. But

the ring main system has

its own advantages and

disadvantages. One of the

major disadvantages of the

system is to attain proper

relay co-ordination in the

system. Some times for the

fault on any line, causes

over loading of the other

lines connected in the

system results cascade

tripping in the system.

Instances of complete

black out of the system

have also been observed

due to the tripping of an

important line. This

situation of overload

tripping and corresponding

effect of cascade tripping

or black out not only

causes heavy loss to the

utility but also results

difficult situation to

normalize the network.

Because the generators,

load centers, equipments

etc... in the system are

required to be coordinated

and controlled for revival

of the system stability and

smooth power flow.

To avoid the

precarious conditions as

described above, an

innovative design

approach have been

selected in the protection

schemes. This concept is

named as LADR (Load

Accessed Directional

Relay). The detail of the

concept has been dealt in

this paper with suitable

example of the network.

2. Introduction:-

To maintain system

stability and reliability,

protective relays play the vital

role, which actuate in time and

clear the fault in the system.

So the protective schemes

need to be designed in such a

way that the reliability of each

protection device and co-

ordination among them should

be achieved up to the optimum

level.

In actual practice,

protection schemes are

categorized in two ways.

(Main protection and Back up

protection). Back up

protection is used to

strengthen the scheme with

confirmation that if main

protection fails to respond

then B/U relay actuates to

clear the fault.

For the instance of

feeder protection Distance

Relays are used as the Main

protection and Over Load

relays are used as the B/U

protection. But for an

optimum situation like

overloading in the system due

to break/fault in the tie line/

interconnected line, it

becomes difficult to control

the stability of the system.

Because the other associated

relays in the healthy lines

also respond to the over

load situation and cause

tripping of the healthy

lines. Sometimes this

condition also causes

complete black out of the

system due to cascade

tripping in the network. .

Similar situation

also results for the case of

equipment protection

(Transformer, Generators

etc...). Here Differential

Relay is used as the Main

protection and Over Load

relay is used as the B/U

protection. For the tripping

of any one or more

transformers in the sub-

station, over loading

situation is resulted on the

other healthy transformers

in the network. So the

system stability gets

hampered and many a

times causes complete

blackout of the system.

This situation of

over load tripping can not

be avoided by the present

available protection

scheme. Because all the

available O/L relays do not

change their plug settings

automatically according to

the load demand on the

line. With the available

pre set value, the relay

responds and issues trip

command if the over load

value reaches above the

setting value. How ever

this problem can be

partially solved by proper

relay coordination of

protection scheme.

3. Basic Concept of

LADR :-

This relay works

on the principle of change

in electrical parameters on

the system. Similar to

conventional directional

relay, this relay also

requires both current and

voltage parameters for its

working operation. The

pick up direction depends

upon the flow of current

and voltage direction. As

per the requirement of the

protection scheme, the

relay can be set either in

forward direction or in

reverse direction. This

LADR is programmed on

the basis of change of

current on the system. The

change of current on the

system occurs due to the

following causes.

1. Over current drawal due to

the rise of consumer load on

a healthy system.

2. Change of electrical

parameters (Voltage and

Current) due to outage of

one or more ties/feeders on

the system for fault

condition.

3. Change of electrical

parameters (Voltage and

Current) due to sudden rise

of fault current in the

system.

Relay is so

programmed that when current

rises beyond certain limit due

to isolation of a part or parts

of the network system or due

to rise of load demand in the

system, then PSM (Plug

Setting Multiplier) changes

accordingly to meet the

extra load demands on the

system. This change of

PSM can be programmed

till to the electrical current

carrying strength of the

line conductor or as per the

required final limit of the

current in the conductor

But for the

condition of fault in the

line the relay issues trip

command directly without

change of PSM and

accordingly isolates the

faulty line.

3.1 Design Approach of

the Relay:-

This setting data of

the relay depends upon the

change in the parameter

group by the binary input

to the relay. Setting groups

are selected as per the

binary input available to

the relay. Two binary

inputs are required for the

purpose of changing four

set of groups. One binary

input must be set for Group

Bit 0 and other for Group

Bit 1. The selection table-1

is shown below.

The setting groups

can be selected as per the

requirement of the load on

the system. The

characteristic of this type

of relay is to change the

setting and also becomes

ready to adopt with the

new setting quickly.

Table 1

Binary Input

Events

Group

Bit 0

Group

Bit 1

Active

Groups

No No Group A

Yes No Group B

No Yes Group C

Yes Yes Group D

Connection Diagram

Relay

A V+ B V -

C

D

V+ A V-

B

C

D

3.2 Study of Current

Behaviours:-

The rate of change

of current due to the rise of

load in the system becomes

slow as compared to the rate

of change of current due to

fault in the system. So, di/dt

(Rate of change of current)

decides the parameters to

the logic function of the

relay, either to change the

plug setting to next groups

or to issue the trip command

without change of setting.

The discrimination between

the di/dt for both the

condition is clearly

indicative and becomes

suitable to develop the logic

function. But measuring

mode for di/dt signal

becomes slight difficult for

the fault condition in the

system. Because the di/dt is

very instantaneous and does

not bear remarkable

difference between the

conditions like fault and

lightning. But to some

extent it can be traced for

logical function.

4. Directional O/C

Protection (67, 67N)

Directional O/C

protection requires the

responses from both voltage

and current transformers in

the system. For the design

of the operating time

characteristics, the

following formula is used as

the working function for

IDMTL Relay.

As per IEC 255-4, BS 142,

3.2)

t =1)/(

cIsI

TmK

Where

t= operating time in seconds

I = fault current in Ampere

Is = Start Current = 1.1 Ib in

Ampere

Tm= Time multiplier

K, c = Factors

Value of K,c

But for the

selection of direction and

working torque of the relay,

the connection of current

coil and voltage coil play

the important role.

Followings are the available

connection of the relay with

relation to MTA (Maximum

Toque Angle).

4.1 DIRECTIONAL B/U RELAY (O/C)

Relationship between MTA (Maximum Torque Angle) and relay connection of O/C relay

Connection

Aph Bph Cph

Relay

connection

angle

MTA

Current

coil

Voltage

coil

Current

coil

Voltage

coil

Current

coil

Voltage

coil

30 0 Ia Vac Ib Vba Ic Vcb

60 Type 1 0 Iab Vac Ibc Vba Ica Vcb

60 Type 2 0 Ia - Vc Ib - Va Ic - Vb

90 30 Lead Ia Vbc Ib Vca Ic Vab

90 45 Lead Ia Vbc Ib Vca Ic Vab

Type K c

Normal

Inverse

0.14 0.02

Very

Inverse

13.5 1.0

Extremely

Inverse

80 2.0

Long Time

Inverse

120 1.0

4.2 DIRECTIONAL B/U RELAY (E/F)

Connection Relay characteristic angle

Current coil Voltage coil

12.5 (lag)

14 (lag)

45 (lag)

60 (lag)

Residual Current

I0 = IA + IB + IC

Residual Voltage

= Open Delta Secondary Voltage

4.3 Basic theory of Relay

Connection

In general for O/C

relay, 900 relay connection

is used with MTA be 450

(lead ) and for E/F relay,

relay connection is also

used as 900 but relay

characteristics angle is taken

as 12.50 ( Lag ).

Explanation:-

For A phase

element, comparing Ia with

Vbc at relay location,

determines direction of the

element. Similarly for the

directional ground fault

element, it is Io and Vo.

The operation and

restraint of the relay

depends upon the torque

angle and maximum

sensitivity will occur when

= . The different fault

directions and associated

voltages and currents have

been explained in the

following table-2.

Ia

Va Ia Maximum Sensitivity

angle

= 450

Vbc

Vbc Operation : cos ( ) = + ve

Table-2 Restraint : cos ( ) = - ve

A B C Ground Pick up

Current Voltage Current Voltage Current Voltage Current Voltage

NOTE

A Ia Vbc

B Ib Vca

C Ic Vab

A,G Ia Vbc Io Vo

B,G Ib Vca Io Vo

C,G Ic Vab Io Vo

A,B Ia Vbc Ib Vca

B,C Ib Vca Ic Vab

C,A Ia Vbc Ic Vab

A,B,G Ia Vbc Ib Vca Io Vo

B,C,G Ib Vca Ic Vab Io Vo

C,A,G Ia Vbc Ic Vab Io Vo

A,B,C Ia Vbc Ib Vca Ic Vab

A,B,C,G Ia Vbc Ib Vca Ic Vab Io Vo

Vo is the

residual

voltage =

Va+ Vb +

Vc

obtained

from open

Delta

connection

5. Programming of

LADR:-

LADR can be

programmed for setting of

different values in groups.

The selection groups can be

chosen as per the

requirement of the

protection scheme and the

associated network in the

system. The change of

group setting is done by the

signal either received

internally from the logic

equation or from the

external triggering by

certain binary input signals.

Consider an

Example of a LADR with 3

groups of settings on O/C

element in a tie line feeder

with 3 parallel lines

between two stations. (Ref.

Table-3)

Table-3

Setting of O/C element

Parameters Group-1 Group-2 Group-3

Specification Dir. Forward,

IDMTL, Normal

Inverse

Dir. Forward,

IDMTL,

Normal Inverse

Dir. Forward,

IDMTL,

Normal Inverse

67-1 pick

up(PSM)

0.75 1.0 1.25

67-1 Time

(TSM)

0.5 0.5 0.5

67-2 pick up

(PSM )

1.0 1.5 1.75

67-2

Time(TSM)

0.5 0.5 0.5

A 1 B

2

3

Fig-1

Here 1,2,3,4,5,6 All Load Accessed Directional Relays ( LADRs )

1*,2*,3*,4*,5*,6* - Main Distance Protection Relays

5.1 Fault Realization and

Programme

For the case of

fault on the line No.1, the

distance protection relay 1*,

4* actuate and isolate the

faulty part from the system.

But due to reduction of tie

link, rest of the two lines

share the extra loads, with a

result of rise in load current

on the line. But because of

LADR at both ends of line 2

&3, the said relays are

sensed by the external

trigger from the DP relays

with conditional rise of load

current on the system and

G1 G2

1,

1*

4,

4*

2,

2*

3,

3*

5,

5*

6,

6*

other logical conditions in

the system. So, the next

group settings are activated

automatically to

accommodate the extra rise

of current in the system.

Similarly with

the available of two lines

say 2 & 3, if the fault occurs

on any one of the line, then

the LADR on the healthy

line being actuated with

next settings, manages the

extra loads till to the current

carrying strength of the line

conductor or to the desired

value of power flow. But for

the condition of actual fault

on the line, the LADR

instead of changing the

setting to next group, issues

trip command for isolation

of fault in the system.

For a system

network, the use of LADR

at different

tie/interconnected lines can

also be programmed by

studying the regular power

flow study for fault in

different part or parts of the

line. According to the study,

the logical condition can be

fed to the LADR for

obtaining smooth and stable

power.

6. Practical Case Study

(Ring Main System)

A practical case

study has been chosen to

avail UPS (Uninterrupted

Power supply) to limited

part of Western Orissa. The

available distribution

network scheme, system

equipments have been

coordinated among them for

optimization of the system

stability. Particularly the use

of NTR (Nodal

Transformer), LADR (Load

Accessed Directional

Relays), and #RLADR with

fault free Auto closing

breaker scheme can achieve

the stable and reliable

power.

6.1 Fault Realization On

the Network

For the case of

fault on any of the Sub

Transmission Tie, the

relays available on either

side of the tie get actuated

to isolate the faulty portion

from the network. But

supply to other distribution

centers (sub-stations) does

not get hampered .Because

other ties being in

connection; provide the

required load to the system.

At the same time the relays

on the faulty line, during

fault actuation send signal

to the other associated

LADRs on the healthy lines

and the suitable settings of

the LADRs are

automatically changed

according to the available

Loads in the network.

For the example

of fault on the Sub

Transmission Tie between

Hirakud substation and

Burla substation, the relays

on this tie line at both ends

are actuated and

simultaneously send trip

command to the breaker

with triggering signals to

the LADRs on the healthy

lines. So the settings on the

LADRs are changed to

accommodate the extra rise

of load current on the

system.

Similarly the

faults on other system

network can be studied to

design the logic programme

of LADRs on the system.

# RLADR (Restricted

Load Accessed Directional

Relays)

These relays

have same characteristics as

that of LADR with certain

limitations. It responds due

to over drawal of limiting

current. In this study, these

relays have been used on

11KV-interconnected tie,

which take load current if

only when 33KV Bus get

faulted. But 11KV network

has certain limitation to

carry the load current .So

when such exigency arises;

the outgoing feeders on the

11KV Bus are automatically

shaded in rotation according

to the available limit of

loads on the 11KV tie. The

kind of load shedding

rotation is pre-programmed

in the RLADR.

6.2 New Idea Of fault free

auto closing of the breaker

From the study

of the described

interconnected distribution

system, it got concluded that

for the fault on any tie,

power supply interruption

does not affect to the

distribution load centers

connected in the network

due to the availability of

other tie lines. So it does not

become important for

immediate restoration /

reclosing of breaker for

power flow on the tie line.

Moreover, reclosing of

breaker with wrong design

of dead time and reclaimed

time sometimes result

severe damage to the

equipment and also converts

transient faults into

permanent faults. For the

case of permanent faults on

the system , every shot of

closing of the breaker,

results electrical and

mechanical stresses on the

system, which causes the

reduction of lifespan of the

system equipments .So it is

always advantageous to

close the breaker for a fault

free feeder.

For the new

idea of fault free auto

closing of the breaker, the

fault detector circuits are

installed on the network,

which automatically detects

the presence of fault on the

circuit and accordingly

sends a signal for operation

of the circuit breaker. For

any faulty feeder, the fault

detector circuit continuously

monitors the status of the

fault and blocks the signal

for closing the breaker till to

the time of clearance of the

fault. After clearance of the

fault the signal is

automatically extended for

closing of the breaker. This

method of monitoring the

status of the fault on the

feeder and deciding output

signal for breaker operation

is repeated automatically

with interval of every five

minutes.

Note: - The

Detail design and the

characteristics of the

system network are beyond

the scope of this paper. So

author has only mentioned

the concept of LADRs,

#RLADRs in this scheme.

7. Conclusion

LADR (Load

Accessed Directional Relay)

is one of the concept in

which over load tripping

can be avoided. But the

programming for the

interconnected system

becomes difficult due to the

complexity of the network

associated in the system.

However it becomes quite

suitable for the tie line

feeders.

Synopsis:-

Availability of

electrical power with proper

quality has become an

essential commodity for any

utility that deal power system

network. Reliability is an

important aspect for the

study of electrical power

system. So to maintain

quality and reliable power,

any utility/company should

secure a competitive

electrical equipment to

accommodate the rapidly

changing situations.

Progressive deregulation of

market, complexity of

industrial processes and

upcoming demand of load in

the network system have also

compelled and necessitated

the utility for the

introduction of sophisticated

protection schemes that can

employ a quick response to

the fault occurrences.

Many utilities use

interconnected tie lines, ring

main network etc.. to

enhance the system

reliability and stability. But

the ring main system has its

own advantages and

disadvantages. One of the

major disadvantages of the

system is to attain proper

relay co-ordination in the

system. Some times for the

fault on any line, causes over

loading of the other lines

connected in the system

results cascade tripping in

the system. Instances of

complete black out of the

system have also been

observed due to the tripping

of an important line. This

situation of overload

tripping and corresponding

effect of cascade tripping or

black out not only causes

heavy loss to the utility but

also results difficult situation

to normalize the network.

Because the generators, load

centers, equipments etc... in

the system are required to be

coordinated and controlled

for revival of the system

stability and smooth power

flow.

To avoid the

precarious conditions as

described above, an

innovative design approach

have been selected in the

protection schemes. This

concept is named as LADR

(Load Accessed Directional

Relay). The detail of the

concept has been dealt in

this paper with suitable

example of the network.

HIGHLIGHTS: -

LADR AN

INNOVATIVE CONCEPT

FOR POWER SYSTEM

STABILITY.

Author of this article

has mentioned one of the

concepts in the area of

directional relay called

LADR (Load Accessed

Directional Relay) in which

over load situation in the

network system can be

avoided. Thus the problem

like cascade tripping and

consequence black out of

the system can be saved.

Letter No. 100/Tech/2006 Dtd. 24.10.2006

From

P.K.PATTANAIK Contacts

Deputy Manager (Elect.) Ph. (0663)-2430514,2430512(O)

E&MR Divn. BURLA - 2431232 (R )

OPTCL, Sambalpur-768017 FAX- (0663)- 2430160 (O )

Email:- ppk110 @ rediffmail.com Mob:- 09437209480

To,

The Editor, IEEMA Journal

501,Kakad Chambers,

132, Dr. A.Besant Road

WORLI, MUMBAI-400018

Sub:- Article for publication in IEEMA Journal

Sir,

Please find enclosed here with the a article titled LADR AN INNOVATIVE

CONCEPT FOR POWER SYSTEM STABILITY. for publication of the same in IEEMA

Journal with other relevant documents.

Receipt of the letter with enclosures may kindly be acknowledged on the Fax- (0663)-

2430160 or e-mail to the above address.

Thanking You

Yours faithfully

Enclosures: -

1. 2 (Two) hard copies of the article P. K. Pattanaik 2. CD with contents of the article

3. Two copies of the photographs

4. Declaration in respect of the Article.

From

P.K.PATTANAIK Contacts

Deputy Manager (Elect.) Ph. (0663)-2430514,2430512(O)

E&MR Divn. BURLA - 2431232 (R )

OPTCL, Sambalpur-768017 FAX- (0663)- 2430160 (O )

Email:- ppk110 @ rediffmail.com Mob:- 09437209480

To,

The Editor, IEEMA Journal

501,Kakad Chambers,

132, Dr. A.Besant Road

WORLI, MUMBAI-400018

Sir,

Sub: - Regarding the Declaration in respect of the Article LADR AN INNOVATIVE

CONCEPT FOR POWER SYSTEM STABILITY.

1. I confirm that this article is original and has not been earlier published in any journal/magazine or any other publication in India. The article has also not been

presented in any seminar/ conference held in India.

2. I confirm that this article has not been sent by me to any other journal/magazine/publication for publishing the same.

3. I am aware, that IEEMA pays honorarium to every published article. On payment of such honorarium, the copyright of the article rests with IEEMA Journal. Therefore,

the same cannot be published elsewhere without express permission from IEEMA

Journal.

4. I confirm that I am responsible for Correctness of data/experimental results presented, Opinions expressed in the article, and Infringement, if any, of copyrights/

ownership rights.

5. I am aware, that IEEMA journal publishes articles on good faith basis. Hence I will be solely responsible for contents, violation of any law in the contents or actions

arising from contents or illustrations.

Thanking You.

Yours faithfully

P. K.PATTANAIK.

PROFILE OF THE AUTHOR

PRASANTA KUMAR PATTANAIK, 40 YR,

! " #$# % & ' ( # )

))*

Letter No. 200/Tech/2007 Dtd. 05.06.2007

From

P.K.PATTANAIK Contacts

Deputy Manager (Elect.) Ph. (0663)-2430514,2430512(O)

E&MR Divn. BURLA - 2431232 (R )

OPTCL, Sambalpur-768017 FAX- (0663)- 2430160 (O )

Email:- ppk110 @ rediffmail.com Mob:- 09437209480

To,

The Editor, IEEMA Journal

501,Kakad Chambers,

132, Dr. A.Besant Road

WORLI, MUMBAI-400018

Sub:- Article for publication in IEEMA Journal, titled LADR AN INNOVATIVE

CONCEPT FOR POWER SYSTEM STABILITY.

Ref:- 1. My ltr No Letter No. 100/Tech/2006, Dtd. 24.10.2006

2. Your Ltr No IJ/PROC.04(555)/245 dated 30.04.2007.

Sir,

Please find enclosed here with the reply to the scrutineers comments on the article

titled LADR AN INNOVATIVE CONCEPT FOR POWER SYSTEM STABILITY.

Receipt of the letter with enclosures may kindly be acknowledged on the Fax- (0663)-

2430160 or e-mail to the above address.

Thanking You

Yours faithfully

Enclosure: - Reply to the scrutineers comments on the article.

Scrutineers comments and Authors Reply on the article LADR

AN INNOVATIVE CONCEPT FOR POWER SYSTEM

STABILITY.

It is my great

pleasure to answer the

comments on the article

titled LADR AN

INNOVATIVE

CONCEPT FOR POWER

SYSTEM STABILITY.

My sincere thanks to the

IEEMA team for allowing

the scrutineers to realize

the concept of the article in

serious manner and the

scrutineers have interacted

on the issues of the article.

I would be rather happy, if

the relay manufacturers

start thinking of

developing the relay with

LADR concept and

utilities to accept the same

for the system stability of

the network.

REPLY

Disturbances on the

network system at

distribution level (11 KV

/33 KV) are not the big

concern for the system

instability. More over if

proper co-ordination on the

relays are achieved, then

the isolation of the faulty

part/parts can be obtained

successfully, avoiding the

problems in the network.

In the article the discussion

on the clearance of the

fault or the actuation of the

sensitive relays to the fault

has not been emphasized.

The article has covered the

solution to the problems

that develop due to over

loading situation in the

system, which causes the

tripping of the healthy

network and system

instability.

For the distribution

level (11 KV /33 KV) , the

initiation of the LADR

relays can be provided

from the associated

auxiliary contacts of the

breaker/switchgear of the

fault zone circuit. So the

external triggering instead

of availing from the remote

relays can be utilized from

the zero state logic of the

equipments (Either

electrical parameter status

of the network or the

physical status of the

relays, breakers, isolators

etc...).

The method

described in the article is

the concept of the LADR

only, but the detail logic

and associated circuit

design depends upon the

available system study and

the tripping characteristics

of other relays associated

in the network. However,

presently the practical

application of the LADR

with the availability of

Distance Protection relays

on the EHV line has

already been tested and

working successfully in the

scheme.

Similarly for the 33

KV level with RING

MAIN system, the external

signal can obtained from

the associated relays in the

network during the time of

fault. So in the situation of

LADR concept, the

initialization of the relay

completely depends upon

the zero state logic of the

associated equipments that

causes the system

instability after the

clearance of the fault. The

initialization can be

obtained from the available

protection scheme of the

system either from the

distance Protection Relays

or from the Over Load

relays in the system.

Irrespective of system

level (11 KV, 33 KV, 132

KV or above) this LADR

relay can be used in the

network to avoid the

system instability due to

Over loading situation.