GE GCX51A User manual

GEI

98328

INSTRUCTIONS

DIRECTIONAL

DISTANCE

(

REACTANCE

RELAY

)

TYPES

GCX

Forms

and

GCX

Forms

and

GENERAL

ELECTRIC

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98328

TABLE

CONTENTS

PAGE

DESCRIPTION

APPLICATION

RATINGS

OPERATING

PRINCIPLES

MHO

Unit

OHM

Unit

CHARACTERISTICS

MHO

Unit

OHM

Unit

Operating

Time

Vernier

Adjustment

for

Low

Tap

Settings

OHM

Unit

Transfer

Auxiliary

BURDENS

CALCULATION

SETTINGS

CONSTRUCTION

ACCEPTANCE

TESTS

Visual

Inspection

Mechanical

Inspection

Electrical

Checks

MHO

Unit

Checks

Control

Spring

Adjustment

Ohmic

Reach

Angle

Maximum

Torque

Check

....

OHM

Unit

Checks

Control

Spring

Adjustment

Ohmic

Reach

and

Angle

Maximum

Torque

Other

Checks

and

Tests

OHM

Unit

Transfer

Relay

(

)

Target

Seal

Unit

INSTALLATION

PROCEDURE

Location

Mounting

Connections

Visual

Inspection

Mechanical

Inspection

Electrical

Check

Tests

Induction

Units

Testing

the

OHM

Unit

Testing

the

MHO

Unit

Other

Checks

and

Tests

Overall

Tests

PERIODIC

CHECKS

AND

ROUTINE

MAINTENANCE

Contact

Cleaning

SERVICING

MHO

UNIT

Control

Spring

Adjustment

Ohmic

Reach

Adjustment

Angle

Maximum

Torque

OHM

UNIT

Control

Spring

Adjustment

Reach

and

Angle

Maximum

Torque

Adjustment

RENEWAL

PARTS

LIST

FIGURES

APPENDIX

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GEI

98328

DIRECTIONAL

DISTANCE

(

REACTANCE

)

RELAYS

TYPE

GCX

DESCRIPTION

The

Type

GCX

and

GCX

relays

are

single

phase

three

zone

phase

distance

relays

The

first

and

second

zone

distance

measurements

are

made

unit

having

reactance

(

OHM

)

type

characteristic

while

the

third

zone

has

directional

MHO

characteristic

The

GCX

and

relays

are

identical

except

that

the

GCX

contains

instantaneous

overcurrent

fault

detector

while

the

GCX

does

not

Three

type

GCX

relays

plus

suitable

RPM

SAM

timing

relay

will

provide

three

step

directional

distance

protection

against

three

phase

and

double

phase

ground

faults

transmission

line

conjunction

with

other

relays

and

pilot

channels

provide

high

speed

protection

transferred

tripping

and

directional

comparison

schemes

Each

GCX

has

one

target

seal

unit

and

comes

case

The

characteristics

these

relays

are

shown

the

diagram

Figure

They

are

also

used

APPLICATION

The

type

GCX

and

GCX

relays

because

the

reactance

characteristics

their

first

and

second

zones

are

particularly

well

suited

for

the

protection

circuits

where

arc

resistance

apt

problem

Since

the

arc

resistance

fault

directly

the

length

the

arc

and

inversely

the

current

arc

resistance

independent

line

length

Thus

arc

resistance

becomes

significant

part

the

total

impedance

from

the

relay

the

fault

the

protected

line

length

gets

shorter

for

this

reason

that

the

GCX

type

characteristic

ideally

suited

for

the

protection

short

transmission

lines

However

the

GCX

relays

may

also

applied

longer

lines

the

range

the

relay

permits

the

required

reach

settings

will

noted

the

section

RATINGS

that

the

reactance

unit

each

GCX

relay

provides

three

basic

minimum

reach

settings

readily

selected

means

tap

link

the

front

the

relay

general

when

setting

these

units

for

given

reach

desirable

use

the

highest

basic

reach

tap

that

will

accommodate

the

required

first

zone

reach

setting

For

example

0.75

ohm

setting

required

for

the

first

zone

standard

reach

relay

the

0.5

ohm

basic

reach

tap

should

used

rather

than

the

0.25

ohm

tap

not

recommended

that

the

OHM

unit

tap

leads

set

for

less

than

These

instructions

not

purport

cover

all

details

variations

equipment

nor

provide

for

every

possible

contingency

met

connection

with

installation

operation

maintenance

Should

further

information

desired

should

particular

problems

arise

which

are

not

covered

sufficiently

for

the

purchaser

’

purposes

the

matter

should

referred

the

General

Electric

Company

the

extent

required

the

products

described

herein

meet

applicable

ANSI

IEEE

and

NEMA

standards

;

but

such

assurance

given

with

respect

local

codes

and

ordinances

because

they

vary

greatly

Courtesy of NationalSwitchgear.com

98328

The

third

zone

MHO

unit

these

relays

adjusted

the

factory

have

angle

maximum

torque

Athough

this

can

adjusted

desirable

retain

the

setting

obtain

maximum

arc

resistance

accommodation

for

first

zone

faults

the

relay

location

not

recommended

that

the

MHO

unit

tap

leads

set

for

less

than

The

MHO

unit

reach

setting

may

subject

further

limitations

described

Appendix

Table

shows

the

minimum

currents

required

the

relay

for

three

phase

faults

the

remote

end

the

protected

line

These

values

current

were

determined

tests

all

conditions

fault

locations

MHO

and

OHM

unit

coordination

and

proper

unit

contact

action

determine

the

final

limitation

for

positive

relay

operation

for

any

multi

phase

fault

the

line

TABLE

Min

Three

Phase

Fault

Current

Secondary

Amperes

Basic

Tap

Setting

Short

Reach

Relay

0.1

ohms

0.2

ohms

0.4

ohms

Amperes

Standard

Reach

Relay

0.25

ohms

0.50

ohms

1.00

ohms

Amperes

Because

they

have

significant

transient

overreach

the

first

zone

units

the

GCX

relays

may

set

for

the

distance

the

nearest

remote

terminal

The

second

zone

units

should

set

reach

least

110

the

distance

the

farthest

remote

terminal

(

including

the

effects

infeed

present

)

The

third

zone

MHO

units

should

set

reach

sufficiently

farther

than

the

second

zone

units

provide

for

accommodating

arc

resistance

the

second

zone

balance

point

The

third

zone

MHO

units

sometimes

are

used

obtain

back

protection

for

faults

remote

line

sections

However

not

good

practice

set

the

MHO

unit

reach

any

farther

than

necessary

The

overcurrent

fault

detector

the

GCX

relays

should

always

set

pick

lower

than

115

maximum

load

current

These

fault

detector

units

are

not

designed

operate

continuously

the

picked

position

For

information

settings

see

the

section

CALCULATIONS

SETTINGS

For

typical

external

connections

three

step

distance

scheme

see

Figure

RATINGS

The

Type

GCX

and

GCX

relays

covered

these

instructions

are

available

for

120

volts

amperes

cycle

rating

The

second

current

rating

225

amperes

The

control

voltage

125

250

selected

link

setting

the

front

the

relay

The

basic

minimum

reach

and

adjustment

range

for

the

OHM

and

MHO

units

the

standard

reach

and

short

reach

forms

the

relay

are

given

Table

Courtesy of NationalSwitchgear.com

98328

TABLE

MHO

UNIT

OHM

UNIT

ANGLL

MAX

TORQUE

RANGE

(

OHMS

)

RANGE

(

OHMS

)

BASIC

MIN

REACH

(

OHMS

)

BASIC

MIN

REACH

(

OHMS

)

RELAY

0.4

174

0.1

Short

Reach

2.5

0.25

0.5

1.0

0.25

600

2.5

Standard

Reach

Adjustment

link

set

the

0.2

0.5

basic

min

reach

prior

shipment

The

angle

maximum

torque

the

MHO

unit

can

adjusted

with

resulting

increase

reach

approximately

120

the

reach

the

angle

maximum

torque

will

noted

that

for

each

relay

three

basic

minimum

reach

settings

are

listed

for

the

OHM

unit

Selection

the

desired

basic

minimum

reach

made

means

two

captive

tap

screws

tap

block

the

front

the

relay

The

reach

settings

the

OHM

and

the

MHO

units

can

adjusted

one

percent

(

)

steps

means

auto

transformer

tap

leads

the

tap

block

the

right

side

the

relay

First

zone

reach

the

OHM

unit

determined

the

leads

second

zone

reach

the

leads

and

the

reach

the

MHO

unit

the

leads

The

GCX

relay

includes

instantaneous

overcurrent

unit

identified

The

short

reach

form

the

GCX

the

internal

connection

diagram

Figure

normally

furnished

with

unit

having

ampere

calibration

range

standard

reach

form

available

with

calibration

ranges

The

amperes

The

contacts

the

GCX

relays

will

and

carry

momentarily

amperes

However

the

circuit

breaker

trip

circuit

must

opened

auxiliary

switch

contact

other

suitable

means

since

the

relay

contacts

have

interrupting

rating

The

0.6

ampere

target

seal

unit

used

the

GCX

relays

has

ratings

shown

Table

III

TABLE

III

TARGET

SEAL

UNIT

0.6

Amp

lap

2.0

Amp

lap

Minimum

Operating

Carry

Continuously

Carry

Amps

for

Carry

Amps

for

Resistance

Cycle

Impedance

2.0

amps

3.5

amps

secs

0.13

ohms

0.53

ohms

0.6

amps

1.5

amps

0.3

secs

0.6

ohms

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GEI

98328

OPERATING

PRINCIPLES

MHO

Unit

The

MHO

unit

the

Type

GCX

relays

the

four

pole

induction

cylinder

construction

(

see

Figure

)

with

schematic

connections

shown

Figure

The

two

side

poles

energized

with

phase

voltage

produce

the

polarizing

flux

The

flux

the

front

pole

energized

with

percentage

the

same

phase

voltage

interacts

with

the

polarizing

flux

produce

restraint

torque

The

flux

the

rear

pole

energized

with

the

two

line

currents

associated

with

the

same

phase

voltage

interacts

with

the

polarizing

flux

produce

the

operating

torque

The

torque

the

balance

point

can

therefore

expressed

the

following

equation

cos

(

)

where

The

phase

voltage

(

)

The

delta

current

(

)

Angle

maximum

torque

the

unit

Power

factor

angle

fault

impedance

Design

constant

Dividing

through

and

transposing

the

equation

reduces

the

following

expression

terms

impedance

cos

(

)

cos

(

)

Thus

the

unit

will

pick

constant

component

admittance

fixed

angle

depending

the

angle

maximum

torque

Hence

the

name

MHO

unit

OHM

Unit

The

OHM

unit

the

GCX

relays

also

the

four

pole

induction

cylinder

construction

(

see

Figure

)

with

schematic

connections

shown

Figure

front

and

back

poles

energized

with

delta

current

produce

the

polarizing

flux

The

side

poles

are

energized

with

voltage

equal

the

difference

between

the

operating

quantity

IZT

and

the

restraint

voltage

where

the

delta

current

and

the

transfer

impedance

the

transactor

Torque

the

unit

results

from

interaction

between

the

net

flux

the

side

and

the

polarizing

flux

the

front

and

rear

poles

and

the

balance

point

can

expressed

the

following

equation

(

IZT

)

sin

The

where

phase

voltage

(

)

delta

current

(

)

transfer

impedance

transactor

(

design

constant

)

angle

between

and

(

IZj

)

design

constant

Courtesy of NationalSwitchgear.com

GEI

98328

means

trigonometric

relations

the

above

equation

can

reduced

(

)

(

IZT

)

sin

(

)

sin

where

angle

between

and

IZj

(

the

transactor

angle

design

constant

)

angle

between

and

(

angle

fault

impedance

)

Since

for

particular

transactor

tap

setting

also

design

constant

the

equation

becomes

sin

—

sin

Thus

the

unit

will

operate

when

the

fault

reactance

less

than

constant

determined

the

transactor

characteristics

and

tap

setting

CHARACTERISTICS

The

operating

characteristics

the

OHM

and

MHO

units

the

GCX

relays

are

best

shown

impedance

characteristics

diagram

(

See

Figure

)

MHO

Unit

The

MHO

unit

has

circular

impedance

characteristic

which

passes

through

the

origin

and

has

its

center

the

angle

maximum

torque

line

the

unit

basic

minimum

reach

the

unit

the

angle

maximum

torque

(

see

Table

under

RATINGS

)

obtained

when

the

restraint

taps

are

100

The

ohmic

reach

can

extended

reducing

the

percentage

the

fault

voltage

applied

the

restraint

circuit

that

setting

the

restraint

taps

lower

percentage

position

the

tap

block

The

ohmic

reach

the

unit

the

transmission

line

angle

which

will

usually

differ

from

the

angle

maximum

torque

can

determined

from

the

following

equation

Ohmic

Reach

Line

Angle

(

Input

Tap

)

Zmin

COS

(

)

Tap

Setting

(

)

The

where

Angle

maximum

torque

the

unit

The

angle

the

line

Zmin

The

basic

minimum

phase

neutral

ohmic

reach

the

unit

Input

tap

setting

Percent

(

normally

100

except

explained

under

Vernier

Adjustment

page

)

Tap

Setting

(

)

the

Voltage

Restraint

Tap

Setting

percent

For

tap

and

input

tap

settings

100

the

phase

neutral

ohmic

reach

will

equal

the

basic

minumum

reach

shown

Table

under

RATINGS

when

the

angles

and

are

equal

Input

Tap

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98328

The

primary

purpose

the

MHO

unit

the

type

GCX

relays

provide

the

directional

discrimination

that

necessary

since

the

OHM

unit

inherently

nondirectional

The

MHO

unit

directional

characteristic

such

that

will

operate

correctly

for

either

forward

reverse

faults

voltages

down

rated

voltage

over

current

range

amperes

secondary

purpose

the

MHO

unit

measure

fault

impedance

for

the

third

zone

protection

reduced

voltage

the

ohmic

value

which

the

MHO

unit

will

operate

may

somewhat

lower

than

its

calculated

value

This

pullback

reduction

reach

shown

Figure

for

the

1.0

ohm

MHO

unit

used

the

short

reach

relay

Figure

for

the

2.5

ohm

MHO

unit

used

the

standard

reach

relay

The

percentage

relay

reach

for

constant

tap

setting

expressed

function

the

three

phase

fault

current

for

various

ohmic

reach

settings

The

MHO

unit

will

operate

for

all

points

the

right

the

curves

The

static

curves

Figures

and

were

determined

tests

performed

with

voltage

supplied

the

relay

before

the

fault

was

applied

The

dynamic

curves

were

obtained

with

full

rated

voltage

120

volts

supplied

the

relay

before

the

fault

was

applied

These

dynamic

curves

illustrate

the

effect

the

MHO

unit

memory

action

which

maintains

the

polarizing

voltage

the

unit

for

few

cycles

after

the

inception

the

fault

This

memory

action

particularly

effective

low

voltage

levels

where

enables

the

MHO

unit

operate

for

low

fault

currents

This

can

most

forcefully

illustrated

for

zero

voltage

fault

referring

Figure

zero

voltage

fault

must

right

the

relay

bus

and

therefore

protect

for

this

fault

imperative

that

the

relay

reach

zero

percent

(

)

its

setting

Figure

shows

that

the

MHO

unit

under

static

conditions

will

not

see

fault

zero

percent

(

)

the

relay

setting

regardless

the

tap

setting

However

under

dynamic

conditions

when

the

memory

action

effective

Figure

shows

that

2.5

ohm

MHO

unit

with

100

tap

setting

will

pick

greater

than

2.5

This

course

marginal

condition

The

minimum

fault

currents

considered

safe

are

listed

Table

the

APPLICATION

section

OHM

Unit

The

OHM

unit

impedance

characteristic

when

represented

the

diagram

(

Figure

)

straight

line

parallel

with

the

axis

The

unit

will

operate

for

fault

impedances

lying

below

its

characteristic

and

hence

non

directional

During

normal

conditions

when

load

being

transmitted

over

the

protected

line

the

voltage

and

current

supplied

the

unit

present

impedance

that

lies

the

axis

since

load

will

very

near

unity

power

factor

contrast

with

the

reactive

KVA

that

flows

during

fault

conditions

impedance

near

the

axis

will

lie

below

the

OHM

unit

characteristic

(

see

Figure

)

and

hence

the

OHM

unit

contact

will

closed

This

will

cause

trouble

however

since

the

directional

MHO

unit

contact

will

not

closed

for

this

condition

(

see

Figure

)

The

basic

minimum

reach

the

OHM

unit

listed

Table

under

RATINGS

obtained

when

the

restraint

tap

leads

are

100

The

ohmic

reach

can

extended

setting

the

restraint

tap

leads

lower

percentage

position

the

tap

block

The

setting

the

two

tap

leads

marked

determines

the

reach

the

instantaneous

first

zone

and

the

setting

the

two

tap

leads

marked

determines

the

reach

the

intermediate

second

zone

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GEI

98328

The

tap

setting

required

protect

zone

ohms

long

where

the

positive

phase

sequence

reactance

(

phase

neutral

)

expressed

secondary

ohms

determined

the

following

equation

Output

Tap

Setting

(

)

Input

Tap

Setting

(

)

}

fBasic

Min

Ohms

)

For

numerical

example

the

determination

the

OHM

and

MHO

unit

settings

refer

the

section

CALCULATIONS

SETTINGS

The

purpose

the

OHM

unit

the

GCX

relays

provide

accurate

measurement

the

distance

fault

and

its

contacts

the

fault

lies

within

the

first

second

zone

protected

the

relay

The

overreach

the

OHM

unit

from

transient

offset

the

fault

current

very

small

even

with

highly

lagging

line

impedances

and

can

neglected

for

relay

settings

within

the

recommended

ranges

Operating

Time

The

operating

time

the

Type

GCX

relay

determined

number

factors

such

basic

minimum

reach

the

OHM

and

MHO

units

fault

current

magnitude

ratio

fault

impedance

relay

reach

and

whether

relay

voltage

prior

the

fault

rated

120

volts

zero

(

)

series

figures

included

the

rear

the

book

showing

operating

time

the

MHO

unit

and

overall

operating

time

the

relay

for

number

typical

conditions

The

operating

time

the

MHO

unit

given

separately

because

this

unit

frequently

used

for

the

carrier

stop

function

directional

comparison

carrier

schemes

The

time

curve

figures

are

listed

Table

for

the

MHO

unit

alone

and

Table

for

the

relay

TABLE

Time

Curves

for

MHO

Unit

Alone

Volts

Prior

Fault

Basic

Min

Reach

(

MHO

Unit

)

Figure

Relay

120

1.0

ohm

Short

Reach

Stand

Reach

1.0

ohm

120

2.5

ohm

2.5

ohm

each

figure

will

noted

that

time

curves

are

given

for

three

ratios

fault

impedance

relay

reach

setting

the

case

the

figures

for

the

zero

voltage

condition

additional

curve

(

shown

dotted

)

also

given

for

volt

resistive

fault

condition

all

cases

the

and

the

taps

were

the

100

position

and

the

MHO

unit

angle

maximum

torque

was

set

lag

Courtesy of NationalSwitchgear.com

GEI

98328

TABLE

Overall

Time

Curves

for

Relay

Basic

Min

Reach

(

MHO

Unit

)

Volts

Prior

Fault

Figure

Relay

ITU

OTT

0.1

120

Short

Reach

0.2

120

0.4

5775

0.25

170

120

0.5

Standard

Reach

0.5

120

1.0

Vernier

Adjustment

for

Low

Tap

Settings

The

input

leads

are

normally

set

100

but

with

high

secondary

ine

reactance

where

the

tap

leads

would

set

low

percentage

the

input

connections

may

varied

vernier

method

obtain

closer

setting

example

the

desired

first

zone

reach

1.2

ohms

and

the

basic

minimum

ach

the

OHM

unit

1.0

ohm

with

the

input

100

the

output

tap

setting

would

100

1.2

83.3

which

can

set

within

0.4

However

the

desired

first

zone

reach

were

9.5

ohms

the

output

setting

would

100

9.5

10.55

The

nearest

output

tap

would

which

off

the

desired

value

correct

this

the

input

leads

can

shifted

which

case

the

output

setting

would

9.5

which

course

can

set

exactly

For

OHM

Unit

Transfer

Auxiliary

The

OHM

unit

transfer

auxiliary

telephone

type

relay

whose

coil

and

contacts

are

shown

the

right

the

internal

connection

diagram

Figure

The

unit

mounted

the

top

the

relay

and

used

change

the

setting

the

OHM

unit

provide

second

step

transmission

line

protection

controlled

the

Type

RPM

SAM

timing

relay

shown

the

external

connections

diagram

Figure

The

normally

closed

contacts

the

transfer

auxiliary

provide

the

circuit

for

instantaneous

tripping

used

for

faults

the

first

step

line

protection

auxiliary

changes

the

setting

the

OHM

unit

switching

the

taps

the

autotransformer

from

which

smaller

potential

supplied

the

unit

potential

restraint

windings

This

extends

the

ohmic

reach

the

OHM

unit

and

enables

operate

for

faults

the

second

zone

transmission

line

protection

Its

operation

the

fault

beyond

the

first

zone

protection

the

transfer

Courtesy of NationalSwitchgear.com

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