A Methodology for Setting up Generator Out-of-Step Protective Relays

84.0 78.0 72.0 66.0 60.0 54.0 48.0 42.0 36.0 30.0 24.0 18.0 12.0 6.00 -6.00 -12.0 -18.0 -24.0 -30.0 -36.0 -42.0 -48.0 -54.0

-60.0 [sec.Ohm

Line - Line impedance

] 66.0

60.0 54.0 48.0 42.0 36.0 30.0 24.0 18.0 12.0 6.00

-6.00 -12.0 -18.0 -24.0 -30.0 -36.0 [sec.Ohm]

Stability Study

3 Phase fail 220KV Alto Anchicayá Clearing Time 310ms

Relay Alto Anchicayá 84.0 84.0 84 78.0 78.0 78 72.0 72.0 72 66.0 66.0 66 60.0 60.0 60 54.0 54.0 54 48.0 48.0 48 42.0 42.0 42 36.0 36.0 36 30.0 30.0 30 24.0 24.0 24 18.0 18.0 18 12.0 12.0 12 6.00 -6.00.00.0 -12.0 -18.0 -24.0 -30.0 -36.0 -42.0 -48.0 -54.0

-60.0 [sec[sec[s .Ohm

Line - Line impedance

] hm] hm 66.0

66.0 66 60.0 60.0 60 54.0 54.0 54 48.0 48.0 48 42.0 42.0 42 36.0 36.0 36 30.0 30.0 30 24.0 24.0 24 18.0 18.0 18 12.0 12.0 12 6.00 6.00 6.

-6.00.00.0 -12.0 -18.0 -24.0 -30.0 -36.0 [sec [sec [s .Ohm]hm]hm

Stability Study

3 Phase fail 220KV Alto Anchicayá Clearing Time 310ms

Relay Alto Anchicayá

A Methodology for Setting

up Generator Out-of-Step

Protective Relays

M^ILLER Z^ULETA * G^LADYS C^AICEDO**

F^RANCISCO J^AVIER M^URCIA*** J^OHN E^DWIN C^ANDELO****

Resumen

En este artículo se presenta una metodología para el ajuste de la protección de pérdida de paso en generadores, que puede ser aplicada en cualquier gene- rador del Sistema de Potencia Colombiano. Se presenta una comparación entre los criterios de ajuste propuestos en artícu- los de investigación y el de un fabricante. La aplicación meto- dológica requirió información como la reactancia transitoria de eje directo del generador, la reactancia del transformador y la impedancia del sistema, así como encontrar los tiempos críticos re- queridos para un correcto ajuste de la protección. La metodología propuesta fue implementada en las protecciones de las centrales eléctricas de Salvajina y el Alto Anchicayá, mejorando la selec- tividad con nuevos criterios de ajuste.

Palabras clave: Centro eléc- trico, generador eléctrico, pérdi- da de paso, relé de protección, oscilación de potencia.

* Electrical Engineer, Universidad del Valle

** Electrical Engineer, Ph.D, Universidad del Valle - GRALTA.

*** Electrical Engineer, Empresa de Energía del Pacífi co EPSA.

**** Electrical Engineer, Ph.D Student, Colciencias, GRALTA - Universidad del Valle. Fecha de recibo: junio de 2006 Fecha de aceptación: agosto de 2006

Abstract

In this article a methodo- logy for setting up generator out-of-step protective relay, to be applied in any generator of Colombian Power System is pre- sented. A comparison between settings proposed in research articles and a manufacturer was carried out. The application of the methodology required infor- mation as generator direct-axis transient reactance, transformer reactance, power system impe- dance and critical time for setting up protective relay. The proposed methodology for setting up gene- rator out-of-step protective relay was applied in the Salvajina and Alto Anchicayá power plants, improving the selectivity with new settings approaches.

Key words: Electrical center, generator, out-of-step, protective relay, power swims.

protective relay and its application in the Salvajina and Alto Anchicayá hydroelectric power plants are pre- sented. The study was carried out with information from international article, protection relay manuals, books and other information ex- tracted from internet.

2. General Concepts

Equation 1 corresponds to the active power transfer from the send- ing node to the receiving node as function of the power system angle (δ). This equation is called Active Power Transfer [1].

1. Introduction

An intolerable operation condi- tion of power system, conducting to the instability is produced by: large-load variations, large-gene- ration variation, line outage and other events that affect the normal operation of power system. Power swims are produced when instabi- lity is presented, causing an out-of- step condition and large currents in generator windings and power transformers; this condition gene- rates electro-dynamical efforts that reduce the useful life of elements.

Standards in Colombia regulate that power plants must include out-of-step protection (ANSI 78), but the settings have been made with relay manuals and operator experience, being no optimal for the power system protection.

In this article a methodology for setting up generator out-of-step

δ

* sin

X

V

P

= V

where:

VS = Sending voltage VR = Receiving voltage X = Equivalent reactance

between sending and re- ceiving nodes.

When the mechanical power is equal to the electrical power, the generator operates in normal condition and operating angle (δ) is about 30º or 40º. After a disturban- ce, the power system equilibrium changes and angle increases. If an- gle exceeds 90º, the generator gets into the critical operating zone and losses synchronism with the system reference. The synchronism limit is about 120º and if this limit is not reached, the oscillation can be avoi- ded with machine-speed regulator, but when the limit is exceed, the generator accelerates impeding the recuperation of the initial condition and an out-of-step is presented. 2.1 Stability and Instability

types

Figure 1 shows the different stability and instability types that produce different effects over power system and the associated parame- ters [2]. The cases are:

1 2 3 4

ANGLE SPREAD

IN IT IA L S T A T E A F T E R D IST U R B A N C E

T I M E ( M in u t e s ) S T E A D Y S T A T E S TA B IL IT Y

(a )

1 2 3 4

ANGLE SPREAD

T I M E ( M in u t e s ) S T E A D Y S T A T E I N S T A B IL IT Y

(a )

1 2 3 4

ANGLE S PREAD

T I M E ( S e c o n d s ) T R A N S I E N T S T A B IL IT Y

(b )

1 2 3 4

ANGLE SPREAD

T I M E ( S e c o n d s ) T R A N S I E N T IN S T A B IL IT Y

(b )

1 2 3 4

ANGLE SPREAD

T I M E ( S e c o n d s ) O S C I L L A T O R Y S T A B IL IT Y

(c )

1 2 3 4

ANGLES PREAD

T I M E ( S e c on d s ) O S C I L L A T O R Y IN S T A B ILIT Y

(c )

0^o

90^o

1 80^o 0^o

90^o 18 0^o

E_A ^EB

E_{A EB}

Zg ^{Zt ZS}

+ -

+ - 0^o

90^o

1 80^o 0^o

90^o 18 0^o

E_A ^EB

E_{A EB}

Zg ^{Zt ZS}

+ -

+ -

1 2 3 4

ANGLE SPREAD

IN IT IA L S T A T E A F T E R D IST U R B A N C E

T I M E ( M in u t e s ) S T E A D Y S T A T E S TA B IL IT Y

(a )

1 2 3 4

ANGLE SPREAD

T I M E ( M in u t e s ) S T E A D Y S T A T E I N S T A B IL IT Y

(a )

1 2 3 4

ANGLE S PREAANGLE S PREAANGLED

T I M E ( S e c o n d s ) T R A N S I E N T S T A B IL IT Y

(b )

1 2 3 4

ANGLE SPREAD SPREAD SPREA

T I M E ( S e c o n d s ) T R A N S I E N T IN S T A B IL IT Y

(b )

1 2 3 4

ANGLE SPREAD

T I M E ( S e c o n d s ) O S C I L L A T O R Y S T A B IL IT Y

(c )

1 2

1 2 3 4

ANGLES PREAD

T I M E ( S e c on d s ) O S C I L L A T O R Y IN S T A B ILIT Y

(c )

a. Steady state stability and instability: when the system is stable and has the ability of respond- ing to events, the electrical machine remains on synchronism with the system and the angle (δ) is smaller than 90º. Small disturbances can increase the angle gradually until it exceeds 90º, where instability is presented. This process can occur in long periods of time (from minutes to hours), as shown in Figure 1(a). For this condition, considerable changes in generators have not occurred and power swims are not presented.

Although, the possibility of pre- senting an angle instability is lower, a special case of load increment could occurs, causing a generator- terminal voltage reduction; if the load is larger than the maximal gen- eration, the angle increases gradu- ally, passing the stability limit, and the system becomes unstable.

b. Transient stability and instability: is presented with lar- ge-disturbances occurrence. Figure 1(b) shows the angle variation over time; if perturbation is cleared ra- pidly, power system could have the ability of responding to the events and oscillation would be dampen, other way it would become a tran- sient instability.

c. Oscillatory stability and instability: is presented with large- disturbance occurrence in power system and is recognized because the angle oscillates constantly over time, as shown in Figure 1c. These changes could be abrupt and rapids.

2.2. Electrical Center

Each voltage of the power sys- tem has a magnitude and a phase angle. As system operating point changes, the voltage phasors can be outside or inside the permissible operating zone, depending on the presented perturbation type.

Figure 2 shows a power system with its voltage magnitudes and angles, which can be different, de- pending on the impedance from the sending to the receiving zone and the operation condition of the power system. If the separation angle from sending node EA to the receiving node EB is 180º, it means that in some place along the network, the voltage has a value of zero [3] and for the elements it could be seen as a three-phased short circuit. The point where the voltage is zero is known as the electrical center of the system and it indicates that a power

Figure 2. Power system electrical center Figure 1. Stability and instability types

instability is presented, causing an out-of-step condition.

If loss-of-synchronism is pre- sented, the equivalent impedance value changes with the relation EA/EB [4], as shown in Figure 3. If EA/EB=1, the impedance locus is along the line LM and perpendicular to the line A-B, bisecting the middle point. Impedance moves from point L to point M and angle δ increases; when the angle passes 120º, the system is considered unstable. The value δ=180º is the point where lines A-B and L-M are intercepted and is the electrical center, where voltage becomes zero.

If E_A/E_B>1, the impedance locus is a circle with center at total impedance line A-B, in the region (+X), in this case the electrical cen- ter is located in the intersection of the curve 1 and the line A-B. Simi- larly, when the relation is E_A/E_B<1, the impedance locus is a circle with center in the region (-X), in this case the electrical center is located in the intersection of the curve 2 and the line A-B.

Determination of the electrical center allows fi nding the operating zones of the out-of-step protective relay.

3. Protective Relay Operation Out-of-step condition can be originated depending on the dif- ferent behavior of power swims. Figure 4, shows the different power swims (curves 1, 2 and 3); the oper- ating zone of out-of-step protective relay is between the two blinders (A and B) and the circle (Mho charac- teristic). The relay measures the sys- tem impedance, but it only operates when the impedance passes through the operating zone, from Blinder B to Blinder A.

Some times a power swim can get into the mho characteristic and reaches one of the blinders, but the

Figure 3. Electrical center as function of the voltage relation

Figure 4. Operating zone of protection ANSI 78

protection settings will not allow operation until it reaches the other blinder. That settings are made be- cause some oscillations can return

B lin d e r A B lin d e r B

X'd XT

Z s

O s c i l l a ti o n B lin d e r AA BB lin d e r B

X'd XT

Z s

O s c i l l a ti o n

to stabilization as shown in Figure 4 (curves 2 and 3).

4. Setting Criteria for Out-of- Step Protection

For setting up the protection, some parameters are required from power system and other must be calculated by computational tools. The invariant physical parameters are taken from generators (direct axis transient reactance Xʼd) and transformers (reactance X_T). Two studies are carried out: one-phase short circuit study in order to fi nd

Figure 5. Operation Characteristic of relay SIEMENS 7UM62

Table 1. Difference between IEEE and Siemens relays settings

Relay IEEE articles Relay Siemens 7UM62

Generator X’d must be multiplied by factor m, from 200% to 300 %.

Must be used 100% of generator impedance

Transformer Xt must be multiplied by factor n from 150% to 200 %.

Must be used from 70% to 90% of transformer impedance

MHO Characteristic ^D_where:^{Mho= n*XT + m*X’d} D_Mho= Mho circle diameter

Not Presented

Characteristic 1 Not Presented

Cart 1 = Zb + Zc where: Zb: X’d

Zc: entre 70 al 90 % XT. Characteristic 2 Not Presented

Cart 2 = Zd - Zc where: Zd: XSIS + XT.

Blinders

N= 0.289 *Z _tot where

Ztot = X’d + Xt + Zsys N: Distance between total line impedance and a blinder

N= 0.289 *Z _tot where:

Ztot = Xb + Xc o Ztot = Xb + Xd

the system impedance and a stability study to fi nd the critical time (120º) and generator poles slip (180º).

Table 1 reviews two setting methods for the protection ANSI 78. Figure 5 shows the settings pro- posed in IEEE articles [5], using the Mho characteristic and the blinders. Figure 6 shows the settings criteria made by SIEMENS for the relay 7UM62[6].

The settings for relay Siemens 7UM62 are similar to the proposed in articles IEEE, but relay 7UM62 uses operation zones denoted as characteristic 1 and 2 and not the Mho characteristic, as shown in Figure 6.

Figure 6. Operating characteristic of relay SIEMENS 7UM62

Im(Z)

Re(Z)

Zb

Za Zc

Zd

Characteristic 1 Characteristic 2 Zd - Zc

X'd (70 a 90 %)Xt

The characteristic 1 can be set to operate between 1 and 4 swims and the characteristic 2 allow between 2 y 8 swims.

5. Methodology for setting generator out-of-step protective relay.

The methodology was applied to relay Siemens 7UM62 located in the Salvajina and Alto Anchicayá hydroelectric power plants, using the computational tool DigSilent and data from the network of Valle del Cauca, Colombia (Table 2).

Relay IEEE articles

Relay IEEE articles Relay Siemens 7UM62Relay Siemens 7UM62 Generator X’d must be multiplied by factor m,

from 200% to 300 %.

Must be used 100% of generator impedance

Transformer Xt must be multiplied by factor n from 150% to 200 %.

Must be used from 70% to 90% of transformer impedance

MHO Characteristic ^D_where:^{Mho= n*XT + m*X’d} D_MhMhMhooo= Mho circle diameter

Not Presented

Characteristic 1 Not Presented

Cart 1 = Zb + Zc where: Zb: X’d

Zc: entre 70 al 90 % XT. Characteristic 2 Not Presented

Cart 2 = Zd - Zc where: Zd: XSIS + XT.

Blinders

N= 0.289 *Z _tot where

Ztot = X’d + Xt + Zsys N: Distance between total line impedance and a blinde impedance and a blinder

N= 0.289 *Z _tot where:

Ztot = Xb + Xc o Ztot = Xb + Xd

The methodology was devel- oped in four stages:

1. Obtaining information from the generator reactance Xʼd and transformer reactance XT. 2. Carrying out one-phase simula-

tions of generation bus, opening previously the associated power switch to obtain the system im- pedance.

3. Referring the system impedance values to the low-voltage side, where the relay is located. 4. Constructing the operating cha-

racteristic as shown in Figure 7. According to the simulation results the correct percents of covering zones of relay 7UM62 must be assigned.

Table 2. Parameters and variables calculated with DigSilent

Salvajina Alto Anchivayá

Generator

X’d 0.2862 pu 0.25 pu

V_N 13.8 kV 13.8 kV

S 100 MVA 126 MVA

Transformer ^{XT 9.99 % 13.14 %}

S 115 MVA 129 MVA

Measuring Transformers ^{TP 14400/120 14400/120}

TC 6000/5 8000/5

Relation ^{RTP 120 120}

RTC 1200 1600

System impedance

R 3.047Ω 3.155Ω

X 26.690Ω 26.494Ω

Z 26.864Ω 26.681Ω

Figure 7. Blinder construction for relay 7UM62

6. Application of the methodology for setting protective relay 78 in Salvajina and Alto Anchicayá.

a. Required Information: The information Xʼd y XT was obtained from network data base of EPSA and is shown in Table 2.

b. One-phase short circuit: Ta- ble 3 shows the data obtained from one-phase short circuit at buses of Salvajina and Alto Anchicayá.

Table 3. One-phase short circuit data

Salvajina Alto Anchicayá

System impedance

R 3.047Ω 3.155Ω

X 26.690Ω 26.494Ω

Z 26.864Ω 26.681Ω

c. Values referred to the low-vol- tage side: The value obtained from Table 2, must be referred to Ω-sec (ohm-secondary), be- cause of the measuring transfor- mers, according Equations (3), (6) and (8).

Salvajina Alto Anchivayá

Generator

X’d 0.2862 pu 0.25 pu

V_N 13.8 kV 13.8 kV

S 100 MVA 126 MVA

Transformer ^{XT 9.99 % 13.14 %}

S 115 MVA 129 MVA

Measuring Transformers ^{TP 14400/120 14400/120}

TC 6000/5 8000/5

Relation ^{RTP 120 120}

RTC 1200 1600

System impedance

R 3.047Ω 3.155Ω

X 26.690Ω 26.494Ω

Z 26.864Ω 26.681Ω

Salvajina Alto Anchicayá

System impedance

R 3.047Ω 3.155Ω

X 26.690Ω 26.494Ω

Z 26.864Ω 26.681Ω

(10) (5)

(6)

(7)

(8) (2)

(3) (4)

d. Construction of the op- erating characteristic: to set up blinders as shown in Figure 7, the operating characteristic is calcu- lated as:

Figure 8. Generator rotor angle Tdes = 260 ms

base pu base

pri MVA

d X d kV

X' ^{* '}

2

_ ⁼

Ω

RTP d RTC

X d

X' _{Ω_sec} = ' _{Ω_pri}*

sec

' _Ω_

= X d Z_b

For transformer:

base T base pri

T MVA

X

X kV ^*

2

_ ⁼

Ω

RTP X RTC

X_{TΩ_sec}= _{TΩ_pri}*

For system:

_ 2

*

base SYS base pri

SYS kV

X X _Ω = MVA

RTP X RTC

X_{SYSΩ_sec}= _{SYSΩ_pri}*

4. 00 3.00

2. 00 1. 00

0.00 [s ]

200. 00

100. 00

-0.0 0

-100 .00

-200 .00

Al to A nc hy a 1-3: Án gul o de l R ot or c o n re s p e cto a l Á ngu lo d e la M · qu in a d e R e fe re nc ia in d e g Sa lva jin a 1-3: Á ngu lo d e l R ot or c on r e spe cto a l Áng ulo de la M · qu ina de Re fe re n c ia in de g

0.59 3 s 175 .917 de g

0. 603 s -179. 39 8 d e g

ESTUD IO DE E ST AB ILI DAD AN G U L O S

FAL L A 3 F BAR R A 2 20 KV SAL VAJ IN A TI EMPO D E D ESPEJ E 2 60 m s

DIgSILENT

) (9)

2 / tan(

2 /

tot

δ

a

Z = Z (9)

where δ = 120º

) 2 / 120o

tan( 2

tot /

a

Z = Z

tot

a

^Z

Z = 0 . 289 *

The total system impedance is expressed as:

c b

tot

^{Z Z}

Z = +

for power swim angle between generator and transformer, and

d b

tot

^{Z Z}

Z = +

for power swim angle between generator and system network.

The critical fault-clearing time as the maximum time to avoid in- stability, the time where generator rotor angle reaches 120º and the time for poles slipping (180º) are calculated by three-phase faults simulations at generation high-volt- age buses, using an approximation method before and after the critical fault-clearing. Also the number of power swims and the swim behavior through the impedance locus are obtained.

Figure 8 and Figure 9 show the three-phase short circuit study at bus 230 kV of Salvajina. The rotor angles behavior and apparent impedance seen for the relays, after a fault-clearing time of 260 ms is shown. Figure 9 shows the impe- dance swings for an out-of-step condition.

Figure 10 and Figure 11 show the rotor angle behavior generators and the apparent impedance seen for Alto Anchicayá and Salvajina in a three-phase short circuit at bus 230 kV with a fault-clearing time of 310 ms. Figure 11 shows a strong power swim and an out-of-step condition originated when a long fault-clear- ing time is presented.

7. Application of out-of- step protective settings for Salvajina and Alto Anchicayá.

Table 4 shows simulation re- sults for setting up both generator out-of-step protective relays. Data

4. 00 3.00

2. 00 1. 00

0.00 [s ]

200. 00

100. 00

-0.0 0

-100 .00

-200 .00

Al to A nc hy a 1-3: Án gul o de l R ot or c o n re s p e cto a l Á ngu lo d e la M · qu in a d e R e fe re nc ia in d e g Sa lva jin a 1-3: Á ngu lo d e l R ot or c on r e spe cto a l Áng ulo de la M · qu ina de Re fe re n c ia in de g

0.59 0.59 3 s 175 .917 de ggg

0. 603 s -179. 39 8 d e ggg

DIgSILENT

For generator:

14 .0 13 .0 12 .0 11 .0 10 .0 9. 0 0 8. 0 0 7. 0 0 6. 0 0 5. 0 0 4. 0 0 3. 0 0 2. 0 0 1. 0 -1 .0 0 -2 .0 0 -3 .0 0 -4 .0 0 -5 .0 0 -6 .0 0 -7 .0 0 -8 .0 0 -9 .0 0

-1 0 . 0 [s e c . O h m ]

10 .0 9. 0 0 8. 0 0 7. 0 0 6. 0 0 5. 0 0 4. 0 0 3. 0 0 2. 0 0 1. 0 0

-1 .0 0 -2 .0 0 -3 .0 0 -4 .0 0 -5 .0 0 -6 .0 0 -7 .0 0 [s e c. O hm ]

REL E A L T O \R E A L I m pe da nc ia LÌ ne a -L Ì ne a

E S T UDI O D E E S T A B IL IDA D R E L E A L T O

F A L L A 3F BAR R AJ E 2 2 0 kV AL T O A N C H IC A Y ¡ T IE M PO D E D E SPEJ E: 310 m s

DIgSILENT

3-PH A SE F A I L B U S 2 2 0 k V A L T O AN C H I C AY A ST A B I L I T Y ST U D Y

C L E A R I N G T I M E : 3 1 0 m s Li ne -Li ne I m ped anc e

R e l a y A l t o 14 .0 13 .0 12 .0 11 .0 10 .0 9. 0 0 8. 0 0 7. 0 0 6. 0 0 5. 0 0 4. 0 0 3. 0 0 2. 0 0 1. 0 -1 .0 0 -2 .0 0 -3 .0 0 -4 .0 0 -5 .0 0 -6 .0 0 -7 .0 0 -8 .0 0 -9 .0 0

-1 0 . 0 [s e c . O h m ]

10 .0 9. 0 0 8. 0 0 7. 0 0 6. 0 0 5. 0 0 4. 0 0 3. 0 0 2. 0 0 1. 0 0

-1 .0 0 -2 .0 0 -3 .0 0 -4 .0 0 -5 .0 0 -6 .0 0 -7 .0 0 [s e c. O hm ]

REL E A L T O \R E A L

¡

DIgSILENT

3-PH A SE F A I L B U S 2 2 0 k V A L T O AN C H I C AY A ST A B I L I T Y ST U D Y

C L E A R I N G T I M E : 3 1 0 m s Li ne -Li ne I m ped anc e

R e l a y A l t o

14. 0 13 .0 12 .0 11 .0 10 .0 9.00 8. 00 7. 00 6.00 5. 00 4. 00 3.00 2. 00 1. 0 -1 .0 0 -2 .0 0 -3 .0 0 -4 .0 0 -5 .0 0 -6 .0 0 -7 .0 0 -8 .0 0 -9 .0 0

-10. 0 [s e c .O hm ]

10 .0 9. 0 0 8. 0 0 7. 0 0 6. 0 0 5. 0 0 4. 0 0 3. 0 0 2. 0 0 1. 0 0

-1 .0 0 -2 .0 0 -3 .0 0 -4 .0 0 -5 .0 0 -6 .0 0 -7 .0 0 [s e c .O h m ]

S A LV A JIN A _ R X \P o lar izin g Im ped an cia LÌ nea- LÌnea

E S T U D IO D E E S T A B IL ID A D R E L E S A L V A J IN A

F A LL A 3F E N BA R R A JE SA LV A J IN A 2 2 0 kV T IEM P O D E D E SPE J E 2 6 0 M S

DIgSILENT

ST A B ILIT Y ST U D Y

3 -P H A S E F A IL BU S 220 kV S A LVAJ IN A C LE A R IN G T IM E : 260 m s Line -Line Im peda nc e

14. 0 13 .0 12 .0 11 .0 10 .0 9.00 8. 00 7. 00 6.00 5. 00 4. 00 3.00 2. 00 1. 0 -1 .0 0 -2 .0 0 -3 .0 0 -4 .0 0 -5 .0 0 -6 .0 0 -7 .0 0 -8 .0 0 -9 .0 0

-10. 0 [s e c .O hm ]

10 .0 9. 0 0 8. 0 0 7. 0 0 6. 0 0 5. 0 0 4. 0 0 3. 0 0 2. 0 0 1. 0 0

-1 .0 0 -2 .0 0 -3 .0 0 -4 .0 0 -5 .0 0 -6 .0 0 -7 .0 0 [s e c .O h m ]

S A LV A JIN A _ R X \P o larar izizin g

DIgSILENT

ST A B ILIT Y ST U D Y

3 -P H A S E F A IL BU S 220 kV S A LVAJ IN A C LE A R IN G T IM E : 260 m s Line -Line Im peda nc e

112. 104. 96.0 88.0 80.0 72.0 64.0 56.0 48.0 40.0 32.0 24.0 16.0 8.00 -8.00 -16.0 -24.0 -32.0 -40.0 -48.0 -56.0 -64.0 -72.0

-80.0 [sec.Ohm]

80.0 72.0 64.0 56.0 48.0 40.0 32.0 24.0 16.0 8.00

-8.00 -16.0 -24.0 -32.0 -40.0 -48.0 -56.0 [sec.Ohm]

DIgSILENT

3-P H A S E FA IL- B U S 220 k V S A LV A J IN A Line -Line Impedanc e

SALVAJINA RX\Polarizing

S TA B ILITY S TU D Y

C LE A R IN G TIME : 260 ms R e l a y S a l v a j i n a

for constructing the out-of-step relay operating characteristic is obtained from Tables 2, 3 and 4. Table 5 shows the relay settings for Alto Anchicayá and Salvajina obtained with equa- tions mentioned above.

Figure 12 shows the operating zone settings of generator out-of-step protective relay of Alto Anchicayá.

Figure 9. Apparent impedance seen from Salvajina Tdes=260ms

Figure 10. Generator rotor angle Tdes = 310

Figure 11. Apparent impedance seen from Alto Anchicayá Tdes = 310 ms

4. 00 3. 00

2. 00 1. 00

0. 00 [s]

200. 00

100. 00

-0.00

-100. 00

-200. 00

Al to Anc hy a 1-3: Á ng ulo de l Rot or c on respe cto al Ángul o de la M áqui na de Re ferenc ia in de g Sa lvajina 1-3: Ángul o de l R ot or c on r espe cto a l Á n gul o de la Má qui na de Re ferenc ia in de g 0. 646 s

176. 193 de g

0. 46 5 s 50. 154 de g

0. 928 s -43. 74 5 de g

0. 655 s -179. 442 de g

DIgSILENT

R e l a y S a l v a j i n a

84.0 78.0 72.0 66.0 60.0 54.0 48.0 42.0 36.0 30.0 24.0 18.0 12.0 6.00 -6.00 -12.0 -18.0 -24.0 -30.0 -36.0 -42.0 -48.0 -54.0

-60.0 [sec.Ohm]

66.0 60.0 54.0 48.0 42.0 36.0 30.0 24.0 18.0 12.0 6.00

-6.00 -12.0 -18.0 -24.0 -30.0 -36.0 [sec.Ohm]

RELEALTO\REAL Impedancia LÌnea-LÌnea

ESTUDIO DE ESTABILIDAD

FALLA 3F BARRAJE 220kV ALTO ANCHICAY¡ TIEMPO DE DESPEJE: 310 ms

DIgSILENT

S TA B ILITY S TUDY

3-P HA S E FA IL 220 kV A LTO A NCHICA Y A CLE A RING

TIME 310 m s Line -Line impedance

R e l a y A l t o a c h i c a y a

X´d (Ω sec) X_T (Ω sec) X_S(Ω sec)

Salvajina 5.45 1.9025 0.9196

Alto Anchicayá 5.037 2.6480 0.5514

Table 4. Obtained parameters (Ω-secondary)

Figure 12. Operating characteristic of Alto Anchicayá Figure 13. Operating characteristic of Salvajina

4. 00 3. 00

2. 00 1. 00

0. 00 [s]

200. 00

100. 00

-0.00

-100. 00

-200. 00

Al to Anc hy a 1-3: Á ng ulo de l Rot or c on respe cto al Ángul o de la M áqui na de Re ferenc ia in de g Sa lvajina 1-3: Ángul o de l R ot or c on r espe cto a l Á n gul o de la Má qui na de Re ferenc ia in de g 0. 646 s

176. 193 de ggg

0. 46 5 s 50. 154 de ggg

0. 928 s -43. 74 5 de ggg

0. 655 s -179. 442 de ggg

DIgSILENT

X´d (Ω sec) X_T (Ω sec) X_S(Ω sec)

Salvajina 5.45 1.9025 0.9196

Alto Anchicayá 5.037 2.6480 0.5514

Figure 13 shows the operating zone settings of generator out-of- step protective relay of Salvajina. In Table 6, the recommended values for setting up generator out-of-step protection of Salvajina and Alto Anchicayá are registered.

8. Conclusion

When comparing the relay 78 settings of Alto Anchicayá with the settings recommended in this article, some differences were founded in the covering areas of characteristics 1 and 2, because it was considered to be larger than the obtained one with computational studies.

A methodology for setting up generator out-of-step protective relay, in two different ways was presented. The fi rst one proposed in IEEE articles and the second one proposed for protection ANSI 78, relay Siemens 7UM62 of Salvajina and Alto Anchicayá.

Three-phase fault simulations over high-voltage buses allowed verifying the out-of-step condi- tion and the critical fault-clearing time and order to set up protection ANSI 78.

Although, the relay operating characteristics proposed by IEEE articles and Siemens are similar, the investigation results indicate that criteria implemented by Siemens are more selective, because this pro- tection allows zoning the operating characteristic in two parts, which have different setting approaches. The confi guration of these operation areas avoids tripping when impe- dance swings are presented, that can be detected outside of the involved area of the generator-transformer group. Also, the blinders for relay Siemens 7UM62 are set up with characteristic 1 or are set up to cover both characteristic 1 and 2, in order to determinate if power swim is sta- ble or unstable, avoiding generator tripping in stable conditions.

Table 5. Calculated parameters for relay Siemens 7UM62.

Alto Anchicayá Salvajina

Zb=X’d 5.037 Ω/sec 5.45 Ω/sec

Zc=80% Covering X_T 2.1184 Ω/sec 1.522 Ω/sec

Zd= X_S + X_T 3.5676 Ω/sec 2.4539 Ω/sec

Zd – Zc = Caract 2 1.4492 Ω/sec 0.9319 Ω/sec

Za (characteristic 1) 2.0679 Ω/sec 1.8443 Ω/sec Za (characteristic 1 and 2) 2.4867 Ω/sec 2.2842 Ω/sec

Settings Salvajina Alto Anchicayá

Za 1,8443 Ω-Sec 2,0679 Ω-Sec

Zb 5,45 Ω-Sec 5,037 Ω-Sec

Zd-Zc 0,9319 Ω-Sec 1,4492 Ω-Sec

Polygon 90º 90º

Swims characteristic 1 1 1

Swims charactistic 2 4 4

T-signal 0.04 0.04

Table 6. Recommended data for protection ANSI 78

Alto Anchicayá Salvajina

Zb=X’d 5.037 Ω/sec 5.45 Ω/sec

Zc=80% Covering X_T 2.1184 Ω/sec 1.522 Ω/sec

Zd= X_S + X_T 3.5676 Ω/sec 2.4539 Ω/sec

Zd – Zc = Caract 2 1.4492 Ω/sec 0.9319 Ω/sec

Za (characteristic 1) 2.0679 Ω/sec 1.8443 Ω/sec Za (characteristic 1 and 2) 2.4867 Ω/sec 2.2842 Ω/sec

Settings Salvajina Alto Anchicayá

Za 1,8443 Ω-Sec 2,0679 Ω-Sec

Zb 5,45 Ω-Sec 5,037 Ω-Sec

Zd-Zc 0,9319 Ω-Sec 1,4492 Ω-Sec

Polygon 90º 90º

Swims characteristic 1 1 1

Swims charactistic 2 4 4

T-signal 0.04 0.04

This methodology can be ap- plied for other generator out-of-step protective relays and contribute to define approaches that are used in the standards CREG.

9. Bibliographic

[1] J. J. Grainger, W. D. Stevenson. Análisis de Sistemas de Potencia. Ed. McGraw-Hill. 1998.

[2] P. Kundur. Power System Stability and Control. Ed. EPRI, Ed. McGraw- Hill. 1994.

[3] P. M. Anderson. Power System Protection. IEEE Press Power En-

gineering Series, Ed. McGraw-Hill. 1999.

[4] J. Berdy, “Out-of-step Protection for Generators”, General Electric Company, [documento en inter- net], disponible en: http://www. beckwithelectric.com/infoctr/tech- papers/genprot01.pdf.

[5] IEEE Guide for AC Generator Protection”, ANSI/IEEE C37.102- 2002

[6] SIPROTEC “Multifunction Gene- rator, Motor and Transformer Pro- tection Relay 7UM62”. SIEMENS Company. 2002