GE STD15C, STD16C Instructions Manual

INSTRUCTIONS

GE

K-45307K

TRANSFORMER

PERCENTAGE

TYPES

DIFFERENTIAL

AN!)

STD15C

RELAYS

HARMONIC

and

STD16C

WITH

RESTRAINT

GE

Protection

205

Great

Malvern,

and

Valley

19355-1337

PA

Control

Parkway

DESCRIPTION APPLICATION CALCULATION

OF Method Current

Transformer Determination Current

Percent I

II IA hA III

Transformer

Slope

Determination

Percent Repeat

Repeat

Percent

Ratio

-

Slope

RATINGS

Models

Auxiliary

12STD15B

Relay

CHARACTERISTICS

and

Pickup

Overcurrent

Percentage

Harmonic

Operating

Unit

Differential

Restraint BURDENS CONSTRUCTION

Current

Transformers Through—Current Differential-Current Overcurrent

Operating

Main

Seal-in

Target

and

Case RECEIVING, ACCEPTANCE

Visual

Mechanical

Electrical

Test

INSTALLATION

HANDLING TESTS

Inspection

Tests

Equipment

PROCEDURE

Tests

Pickup

Harmonic

Current

Through-Current

Instantaneous

Main

Dropout

of

Location

Mounting

Connections

ADJUSTMENTS

Plug

Tap

Percent

Positioning

Slope

OPERATION

Targets Disabling

of

MAINTENANCE

Contact

PERIODIC

Cleaning

TESTS

Pickup

Harmonic

Current

Through-Current

SERVICING RENEWAL

PARTS

SETTINGS

CT

of Setting

of

Error

Turns

CT

Percent

Setting

and

Control

Pickup

Restraint

Unit

AND

Restraint

Overcurrent

Unit

Setting

STD

Type

Restraint

GEK-45307

Connections

CT

and Ratio

and Error

Turns

Relay

Error

Turns Ratio

12STD16B

Circuit

Time

Characteristics

Circuit

Unit

STORAGE

Unit

Relay

Type

and

Tap

2

STD

Relay

Setting

Tap

Setting

3 3 5 5 5 5

6

8

8 9

9 10 10

10 10 11 ii 11

11

12

12 13 14 14 14

15 15 16

16

16 17 17 17

17

18

18 18 19 19 20

21

21 21 21

21

23

23 23

24

24 24

25 25

26

GEK-45

307

Relays features small

telephone-type

Percentage faults

the

by internal

Each

Type

used

for

current The

Type

three

has It

may

three the

circuits

weakest,

the

of

percentage

restraint

at

high

difference

fault,

STD

the

restraint

STD16C

through-current

also

be

needs

STD

current,

and

relay

protection

circuits

relay

used

require

WITH

type

and

relay

permits

while

in

waveform,

that

of

is

a

single-phase

is

for

four-circuit

through-current

no

through-current

TRANSFORMER

PERCENTAGE

STD15C

INTRODUCTION

transformer

are

harmonic

provides

that

accurate

harmonic

between

transformer

DES

of

two-winding

and

one

differential—current

designed

for

restraint

DIFFERENTIAL

AND

HARMONIC

and

STD16C

differential

restraint.

the

contact

discrimination

restraint

the

magnetizing

CR1

PTI

ON

unit.

The

power

use

with

circuits

and

transformer

restraint,

restraint.

RELAYS

RESTRAINT

relays

static

A

output.

between

enables

differential

inrush.

Type

STD15C

transformers

circuit.

three—winding

one

differential—current

protection

while

the

decision

the

current

relay

power

(see

provided

internal relay

and

Figure

fourth

unit

and

distinguish,

to

caused

is

designed

has

two

transformers

1)

circuit,

with

controls

external

through-

circuit.

when

by

to

only

being

the

a

an

be

and

The

current maximum transformer transformer selected

The

1.

the be available to

Since

increasing as accuracy

sensitivity

ratios

with

lower sensitivity.

compatible

increase

the

result

a

These

every

possible further the

purchaser’s

the

To

but

such

no

transformer

(CT),

the

following

the

relay

with

of

increasing

the

relay

the

of

the

1nstrucron5

ctingency

nforma

ton

purposes,

extent

required

assurance

without

or

the

in

the

However,

CT

ratio

burden

CT

ratio

reducing

CTs.

do

not

to

desi red

be

the

given

is

ratios

tap

some

purport

be

or

matter

the

with

risking

possibility

various

points

and

of

either

in

is

tends

the

met

in

should

products

respect

APPLICATION

and

in

the

lowest

the

preference

likely

to

maximum

to

cover

connection

parti

cular

be

described

to

relay

thermal

windings

mind:

lower

following

CT

to

improve

secondary

details

i.11

with

probleme

referred

herein

local

codes

3

taps

of

the

CT

ratio

to

be

installation,

to

meet

ratio

the

or

arise

the

and

should

overload

misoperation.

of

the

CT

ratio

and restrictions. or

the

relay

small the

compared

relative

fault

variations

General

applicable

ordinances

which

in

operation

are

Electric

ANSI,

because

be

of

power

selected,

the

relay

tap.

current

equipaent

not

Company.

selected

the

Therefore,

transformer

lowest

Where

tap,

to

performance

nez

IlntnCe.

or covered

ziWficiently

IEt

andN

varç

they

relay

the

relay

the

and

e

greatly.

to

higher

it

increasing

provide

Should

standards,

tap

a

is

lead

of

for

obtain

or

should

choice

desirable

the

current current

will may

burden,

CT5,

the

be

not

is

the

GEK—45307

2.

3.

4.

5.

6.

7.

CT

The

CT

The

should

The

the

The cooled

inrush under

secondary

relay

not

CT

ratios

relay

basis)

night

consideration

manufacturer

is

the

rating

inrush

The times

characteristics

current

rated current. less

than

sufficient

be

The

CT external exactly provided

within

it

is

5%.

obvious changing of

the

relied

when

upon

the

winding.

current

exceed

under

current

If

times

8

ratios

faults.

selection

by

the

on

When

range.

range

to

load-ratio

current

twice

should

maximum

corresponding

should

operate

should

of

self-cooled

a

transformer

relay

the

tap

current

tap

to

cause

should

Since

relay

the

that

a

In

and

the

prevent

should

corresponding

tap

value,

high

be

enough

internal

not

exceed

the

instantaneous

does

be

not

consulted

transformer

as

the

transformer

tap

chosen

current,

transformers

it

current

means

the

restraint

selected

is

rarely

value,

false

be

of

by

protected

close

this

match

case,

percentage_differential

relay

control

is

operation at

not

exceed

to which

that

fault

to

rated the

have

for

must

with

harmonic

to

transformer

of

which

transformer

cannot

the

secondary

the

ends

the continuous

maximum

is

the

conditions

kVA

relay

overcurrent

self—cooled

a

the

“equivalent

that

being

be

error

an

produce

content

on

internal

provide

possible

the

be

obtained

on

of

kVA

the

thermal

secondary

of

tap

considered.

able

an

to

ratios,

currents

is

equipped

currents

characteristic

the

(on

(refer

the

power

value

unit).

would

to

of

less error of faults.

balanced

match

at

unbalanced

range.

thermal

forced-cooled

a

rating

of

currents

to

RATINGS).

transformer

selected

If

rating, self—cooled have

the

supply

than

of

the

20%

greater

secondary

the

ratio—matching

may

usually

with

all

are

load-ratio

points

matched

current

the

will

the

same

of

rating

relay.

not

(on

(magnetizing

transformer transformer

rating”;

magnetizing

relay

the

of

than current

current

currents

taps

be

matched control

of

the

at

the

relay

which

of

the

basis)

damage

self-

that

with

total

20%

may

are

ratiomiddle

flows

8

at

on

is

In

8. voltage

for selected load current. voltage) restraint

It

is

not

differential

In

addition,

false

operation “sympathetic tend

to

harmonics Typical

and

3.

some

applications,

or

example

so

current

desirable

protection,

if

inrush”

flow

between

in

the

elementary

low

in

that

It

is

breakers

on

heavy

the

on

relay

diagrams

voltage

ring—bus

a

the

flowing

recommended

be

through-fault

to

since

banks

magnetizing

into

the

banks,

current

the

system

secondary

around

connected

protect

can

the

for

power

through

arrangement.

the

that

two

the

sensitivity

be

switched

inrush

bank

already

with

to

restrain

the

STD15C

transformer

windings

ring

CTs

to

a

current

parallel

the

possibility

4

four

in

on

each

separate

flowing

separately,

to

energized.

the

and

breakers

this

In

will

addition

of

transformer

of

the

one

relay.

STD16C

will

be (as

case,

not

be

the

restraining

around

protection

there

transformer

In

that

there

are

connected

shown the

thermally

to

the

two low

the

ring

banks

is

this

case,

will

illustrated

in

ratios

CT

overloaded transformer voltage

winding

bus.

with

would

possibility

a

bank,

the

be

to

the

Figure

must

(or

to

one

set

reduced.

be

causing

harmonics

insufficient

in

Figures

high

1)

load high

assure

as be

on

of

a

2

GEK—45307

METHOD

The

calculations

below.

CURRENT

sample

A

TRANSFORMER

Power

DETERMINATION

Determine

1. transformer

transformer.

Max.

required

calculation,

CONNECTIONS

Transformer

Delta-Wye

Wye-Del

Delta-Delta

Wye-Wye

Delta-Zigzag shift

between

secondary

CT

the

TURNS

maximum

OF

winding

—

Maximum

-

CALCULATION

for

determining

for

Connections

the

OF

the proper

transformer

SETTINGS

shown

Current

relay

Figure

in

Transformer

and

taps

CT

4,

Connections

outlined

are

is

then

given.

Wye-Delta Del

ta

ta-Wye Wye—Wye Delta-Delta

with

primary

TYPE

AND

line currents

may

carry

Transformer

(Line

phase

O

and

STD

RELAY

the

TAP

(Max.

maximum

SETTING

I)

forced—cooled

kVA

kV)

Delta—Delta

on

the

basis

rated

that

each

kVA

of

power

the

2.

3.

Determine power

transformer

transformer,

100%

Actually, carry of

these

calculating

voltage so

that

Select not

CT

exceed transformer selected current

be

3

times

properly

can than

For

the

full—load

or

the

—

100%

‘P

-

this calculation

maximum

the

ratings.

the

relay

in

ratios

the

so

either

is

that

so CT connected

the

matched

lowest

Wye-connected

Tap

Current

winding

“equivalent”

Transformer

(Line

load

currents

This

will

not

that

secondary

CT

breaker.

current).

CTs

=

rated

may

currents

is

the

operate

the

to

thermal

by

means

100%

line

carry

self-cooled

kVA

kV)

does

in requirement

secondary

thermal

ring

a

rating

Also,

I

currents

the

not

mean

continuously.

the

other

for

any

current

rating

bus,

will

select

of

the

relay

(100%

full

ratings.

that

windings

for

external

(5

for

not

CT

ratios

I)

self-cooled

windings

all

This

selecting

fault.

corresponding

amperes).

example,

exceeded

be

so

taps.

(Highest

on

is

in

the

that

the

rated

only

proportion

relay

the

to

In

CT

by

the

basis

will

a

convenient

maximum

the

ratio

the

relay

current

that

kVA

necessarily

to

tap

case

where

should

maximum

currents not

each

of

their

setting

does

Ip

load

more

the

way

a

be

5

For

Delta-connected

GEK-45307

CTs

4.

5.

Current

Tap where

Check as

low

the

as

Calculate determine differences of

mismatch.

three-winding

For

for

all

combinations

If

taps

limits,

lines,

Check relay amperes the

cannot

it

to

for

RMS

relay

accommodated

(Amperes)?

N

is

matching

possible.

the

percentage

ratio

the

between

The

will

obtain

see

that

fault

a

for

can

be

in

=

the

number

of

these

mismatch

transformers,

of

be

selected

necessary

be

a

better

the

at second.

1

definitely

accordance

seconds

x

LnL

N

relay

of

the

currents

match

sum

of

CT

currents

mismatch

two

relay

ratios,

normally

to

of

the

terminals

If

the

limited

with

48,400

secondary

divided

should

the

percent of

or

taps.

keep

choose

between

relay

period

to

the

relation:

to

as

currents

this

relay

of

the

a

turns.

relay

follows:

by not

percentage

different

a

currents

power

during

shorter

taps,

and

the

exceed

mismatch

currents

which

time,

to

keep

two—winding

on

the

tap

smaller

5%.

error

CT

and

will

that

transformer

a

values

ratio,

ratio

relay

fault

higher

the

should

within

be

is

current

mismatch

transformers,

selected.

the

is

be

one

on

taps.

applied

less

current

error

percent

checked

allowable

or

more

to

than

flows

can

The

the 220

in

be

Also external

CURRENT

CT

The

is tap figure

The

ratio

based

rating.

must

calculations performance transformer the

protected

Determine

1.

a.

b.

check

that

fault

TRANSFORMER

on

error

the

If

be

must

instantaneous

the

reduced,

listed

is

concerned,

winding,

transformer.

the

burden

For

Wye-connected

=

For

Delta-connected

=

2B

Z

the

do

not

RATIO

ERROR

be

instantaneous

as

below

which

with

none

on

+

Ne+2f

+

Ne

1000

of

suni exceed

less

unit

described

of

each

CTs

+

CTs

+

2f

+

than

are

is

2R

the

150.

being

the

CT,

20%

unit

in

for

an

using

Ohms

multiples

at

set

pickup

the

the internal fault

times

8

at

its is

CHARACTERISTICS

worst—fault

ground

current

the

following

of

tap

relay

normal

raised

supplied

current

rated

setting,

above

section.

condition,

fault

expressions:

this

between

through

on

tap

an

current.

which

value,

as

the

(Equation

internal

is

far

and

CT

neutral

8 the

This

times

as

1)

2)

or

20%

CT

the

of

6

GEK-45307

where

STD

B

N e

f

R

TAPS

2.9

3.2

3.5

3.8

4.2

4.6

5.0

8.7

STD

=

number

bushing

busing

one-way

AMPS

relay

of

total

turns

CT

tempera

CT

ture) resistance

temperature)

control

temperature)

Total

X

8

burden

in

resistance

cable

Burden

TAP

AMPS

23.2

25.6

28.0

30.4

33.6

36.8

40.0

69.6

(see

bushing

per

lead

TABLE

for

Table

CT

turn,

lead,

resistance

I

60

Cycle

BURDEN

I)

milliohms

Relays

OHMS

0.180

0.156

0.140

0.120

0.112

0.096

0.088

0.048

(at

(B)

(at

maximum

(at

maximum

MIN

expected

P.U.

0.87

0.96

1.05

1.14

1.26

1.38

1.50

2.61

AMPS

2.

3.

4.

5.

Determine

(Note: current relay CTs

Determine

Esec

From

excitation

determine

Esec. Determine

%

should

This necessary calculations error.

CT

=

8

are secondary

=

excitation

the

error

to

secondary

x

STD

For is

current

connected

IZ

curve

percent

1

E

=

Is

not

exceed choose on

selection

relay

the

supplied

are

CT

of

current

error

100

X

a

higher

current

tap

location

by

the

in

voltage

particular

20%

of

same,

wye

in

of

for

rating

of

one

CT,

or

required

corresponding

IE.

each

any

tap

on

relay

times

8

fault

so regardless delta.)

tap

by

CT

of

set

that

taps,

tap

assumed, that

at

8

of

current

the

CTs. set

of

mismatch

setting.

all

current

CT of

whether

times

tap

transformer

this

to

expression:

it

If

CTs,

error,

the

and the

setting.

secondary

does, and

fault

it

repeat

and

being

will

the

percent

used,

voltage,

be

ratio

7

GE:K-45307

PERCENT The

proper

a.

The

tap

The

b.

Set

the

The

percentage total total

20%, If

should

error

but

the

be

EXAMPLE

I.

Determination

1.

2.

3.

4.

5.

6.

7.

8.

SLOPE

percent

maximum

changing maximum

desired

not

movable

chosen

(REFER

Transformer Maximum 100% Assume Maximum 100% CT Relay

SETTING

range

means,

percent

slope current current

the

35%,

lead

about

TO

FIGURE

I

=

Ip

CT

I

secondary

I

connections

Current

slope

of

setting

the

to

does

40%

is

used

twice

of

CT

and

=

3750/

3000/

turns

secondary

required

manual

in

of

slope

smaller

not

setting

4) Turns

Line

J

(N)

for

taps

percent.

mismatch

by

means

selected

exceed

in

(as

as

high,

and

(Line

J3

(Line

(less

I

100%

is

determined

of

20%,

is

used.

Figure

since

STD

kV)

than

Sec.

and

the

of

should the

the

Relay

5a)

by

the

load—ratio-control,

relay

R3

through

1,

the

(See

be

25%

for

Tap

taps.

Figure

greater

currents.

setting

example)

movable

Settings

the

sum

than

lead

A

19.7

15.7

20

0.98

0.79

Delta

1.37

6A).

is

of:

the In

used.

the

provides

B

49.5

39.6 20

Wye

ratio

general,

percent

2.47

1.98

or

If

automatic

of

maximum

if

it

exceeds

slope

no

restraint.

C

157

125

60

2.62

2.08

Delta

3.60

the

setting

10.

11.

9.

Select

currents

If

any

chosen

Ideal

Try

Relay

Check Ratio

1.98

-

—

1.37 Mismatch

Ratio

Mismatch

a

relay

in

current

for

it,

Relay

Taps

Mismatch of

Taps

1.44

of

Taps

1.89

other

Taps

on

-

on

-

1

tap

lines

is

and

(Set

Error

Lines

43

LinesC-B

1.82

8

for

greater new

C

=

one

would

ideal

B-A

0.7%

-!.j-

3.8%

8.7)

than

relay

of

the

line

be

if

they

times

V3

taps

=

1.43

1.89

Ratio

=

calculated

Ratio

currents

were

any

3.31

3.2

of

Sec.

increased

other,

Sec.

Line

and

for

4.78

Lines

the

4.6

Currents

calculate

in

the

8.7 other

Currents

tap

8.7

same

should

lines.

what

=

the

ratio.

be

1.82

8

GE

K—45

307

II.

12.

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Bushing

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of

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7.

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14.6%

Continuous

The

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tap

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Short

220

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amperes

relay.

with

the

where

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For relay

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i

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value

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time

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STD15C

the

should

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for

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equation:

amperes

in

seconds.

several

be

result

circuit.

breakers

transformer

any

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twice

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and

STD16C

sets

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measured

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of

on

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of

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value)

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of

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value

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type

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to

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if

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GEK—45

307

DC

Resistance Carry Carry Carry

AUXILIARY

STD15C

The

and

110 links

220

located

voltages.

STD

The circuit. exceeding tripping relay. relays breaker

After

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or

normally

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30

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10

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volts.

250

current

the

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by

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STD16C

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relays

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front

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breaker

auxiliary)

automatic

more

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than

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the

relay

two

one

it

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TABLE

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contact

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the

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to

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to

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plate

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of

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on

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recommended

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ohms

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with

one

voltages

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with

the

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or

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output

if

the

these

circuit

48,

not the

STD

and

PICKUP

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indicates

AND

operating

shows

percentage

OPERATING

an approximately operating

current

milliseconds. Curves

shown time

OVERCURRENT

The transformer flowing

of

the

in

Figure

includes

overcurrent

in

that

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only

UNIT

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the

AC current component

characteristic

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percent

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approximate

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operating

5,

auxiliary

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tap.

one

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component

transformer

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unit

CT

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supplies

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value

time

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example:

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current

in

the

CHARACTERISTI

shown

versus

given characteristic. (see

to

zero

of

the

differential

times

the

current,

required

transformer

relay

in

Figure

the

throughcurrent

Table

from

main

time.

to

pick

ampere

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for

produces

to

any

unit

pickup.

Cs

7.

a

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value

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output

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unit

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on

11

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307

If

tap

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unit

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where

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=

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percentage restraint differential

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unbalanced

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shown

on

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transformers

currents

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as Settings.

taps

on

a

self-cooled

inrush.

may

pick that

the

pickup

requirements

equation: 20

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error

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of

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differential

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current

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the

in

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by

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on

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the

currents

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in

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addition

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their

characteristic ratios

currents

described

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at

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in

characteristics

to

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current

indirectly

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percentage,

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currents

to

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caused

under

rated

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overcurrent

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relay

unit.

be

more

pickup

of

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transformers,

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current

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transformer

tap

setting

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stringent,

of

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tap

setting.

are

circuit,

transformer

determined

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imperfect

unit

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the

overcurrent

provided

the

by

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is

of

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rating,

banks.

be

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in

which

relay

the

secondary

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the

to

prevent cores

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prevent

secondary

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on

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time

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establishes

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Power

causes

false

system component. constant cycle

at

Transformer

exciting magnitude, full-load

of-circuit of

sharply practically illustrated

RESTRAINT

power

a

the

and

in

the

an

unbalance

operation

fault

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sine

circuit

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fault

magnetizing-inrush

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current

closure

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no

current

in

Figure

CHARACTERISTICS

transformer

required

primary

flux

winding

current

if

means

currents

waveform

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occurs,

were

are

results

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and

resulting

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for

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on

half-cycle

voltage

during

conditions

loops

the

8.

is

of

DC

upon

currents from

RMS

an

wave.

opposite

energized,

in

the

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flow

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nearly

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component

circuit

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value

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core.

only

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saturation.

power

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current

half

current

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to

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with

100%

transformer

have

on

cycles.

current

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voltage

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one

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it.

on

to

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side

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called

relay,

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time

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waveform

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current

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magnetizing

transformers.

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DC

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and

in

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angle.

often

flux

and

zero

axis, waves

primary

would

transient

nearly

voltage

variable of

times

16

point-

made

high

up and are

12

GEK—45307

current

Any of one

DC

a

of

component

the

frequencies

relative

magnitudes fundamental fault-current

while

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afford

wave.

the

high

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value

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distorted,

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determine

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through

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shown

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system

2,

the

found

of

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Table

a

phase

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number

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4,

5,

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relays,

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electric

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transformer

effect.

of

harmonics

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on

of

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differential—current

III

and IV.

the

percent

given

are

waveform

sine-wave

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relay

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slope

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on

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reference

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lower

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current

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to

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AMPS

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0.96

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relay

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140

coil

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TABLE

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CYCLE

60

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2.4

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1.5

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same

TABLE

CONTROL

III

CIRCUIT

RELAYS

IMPEDANCE

OHMS

0.128

0.108

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normal

or

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CIRCUIT 250

88

13

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lower.

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48

140

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220

80

—

Figure Refer

identify

6

also

shows

the

to

parts

the

internal

more

arrangement

connection

completely.

GEK—45307

CONSTRUCTION

the

of

diagrams,

components

Figures

10

of

and

the

STD15C

11,

which

relay.

will

CURRENT

In

one

and

In each

windings

In

brought

The block

TRANSFORMERS

Type

the

each

for

winding

Type

the

with

No.

both

relays

out

primary

arrangement. (depending through-current

connected

is

inserting

When

the between the

marked

the

fourth

terminals

terminal

winding

transformer

under

the

lead.

STD15C

relay,

line-current-transformer

No.2terminates

one No.

relay,

primary

2

STD16C

only

I,

there

stud

to

circuit

5.

of

Two

whether

on

transformer

end

a

relay

6

and

corresponding

in

CT

and

to

tap

plugs

STD16C

circuit

6

1),

the

STD

that

tap

in

screw

the

at

there

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and

is

differential—current

a

each

of

or

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winding.

tap

the

used

is

connected at

7

reconnected

which

relay.

gives

through-current

4.

stud

are

winding,

corresponding

3

these

three

transformers

horizontal

is

tap

blocks.

on

four-circuit

to

rear

the

to

connects

terminal

The

the

best

circuit.

three

and

Type

a

tap

A

of

stud

of

the

it

current

transformer

Winding

separate

each

to

rows

STD15C

the

on

the

through—current

applications,

7,

relay

the

upper

row

directly

on

match

has

No.

through—current

terminating

4

studs

6,

transformer

is

completed

of

tap

STD16C),

or

differential—current

jumper

the

and

to

for

the

should

tap

the

cradle

in

movable

primary

two

terminates

1

at

a

with

in

3

one

and

through

positions

one

restraint

shown

as

normally

be

block

differential-current

lead

should

current

windings,

at

transformers,

separate

order.

that

primary

special

a

provided

are

for

row

transformer

windings

in

Figure

connected

disconnected

(above

be

the

in

stud

stud,

lead

tap

each

the

row

placed

movable

6

by

1, at

matching

are

moved

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from

differential—current

restraint

recognized

but

quantity

RESTRAINT

bridge

rectifier

transformer.

in

so one

windings

producing

of

parallel.

connections

both

on

transformer

permit

is

The The

tap

taps current

taps

tap

plug

through-current

should

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be transformer transformer,

this

THROUGH-CURRENT

wave

full

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restraint

are

connected

of

arranged

position

remains

that

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CIRCUIT

unequal

are

constant.

pickup

through

some

receives

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line—current

in

that

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to

transformer

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current

one

restraint.

so

small

is

the

STD16C

the

total

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14

matching

of

output

flows

the

that

relay,

transformer

the

in

horizontal

a

winding

selected

not

primary

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it

may

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of

is

secondary

only

windings

compared

be

secondary

the

directed

and

so

assumed

DC

secondary

row,

one

that

through

outputs

to

currents,

corresponding

of

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differential-

the

of

the

to

of

each

of

the

percent

the

be

currents.

when

through—

percent

through-

operating

zero.

through

three

all

slope

a

GE STD15C, STD16C Instructions Manual

Specifications and Main Features

Frequently Asked Questions

User Manual