Protección de Motor

8/3/2019 Protección de Motor

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SIEMENS

FUNDAMENTOS DE LOS SISTEMAS DE

PROTECCION NUMERICOS

Protección de Motor



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ED SE PTI

Content of presentation

§ Technical data from the motor manufacturer§ Setting examples of thermal functions§ Overload protection stator (running motor)§ Restart inhibit function§

Motor starting time supervision§ Unbalanced load (negative sequence) protection



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Technical Data

MVA1,60S

154A6000V3S

IU3S

N

N

NNN

=

∗∗=

=

KW1379P

0.9580.9MVA1,60P

cosS P

N

N

NN

=∗∗=

∗∗= ηϕ



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Motor starting curve (acceleration)

Technicaldata (2)



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Technicaldata (3)



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9s13s

for Statoroverloadprotection

1,15

Technicaldata (3)

Locked rotorlimits with thegiven startingcurrent



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Stator overload protection(running motor under load)

This should be set to equal the k-factor.1,15 IN,MCurrent alarm stage

The value 2,5 IN,M

can be used for a short starting time. If a

longer starting time is possible (>20s), the limit should be

reduced to 2 I/IN,M.

2,5 I/IN,MCurrent limiting

During operation under rated condition the thermal memory is

always below 90%. With the default setting of 1,1, this is 83%

and in the case of k = 1,15, only 76%.

90%Thermal alarm stage

Take this from the thermal characteristic (technical data (4)); if

this is not available a k-factor of 1,1 can be used, because the

thermal class F/B is specified (see technical data (1))

1,15k-factor

Take this from the motor data sheet (technical data (4)) or set

an experienced-based value, e.g. 7 times the heating time

constant.

175 minCooling down time constant

Take this from the motor data sheet

(technical data (4)).

25 minHeating time constant

CommentValueSetting parameters



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Current limiting

Freezing the thermal memory during starting§ This is intended to avoid overfunction of the overload protection during

starting.§ Realization: 7SJ6

Internal limiting of the starting current§ The current fed to the thermal model is limited during starting. This

“slows down” the heating development. Current limiting should lie atapproximately 2,5 I/IN,M. Further reduction of limiting is recommended ifstarting times are long and successive warm starts are possible. Forexample, a value of 2 I/IN,M makes sense for a starting time of 52 s (at

0,8 UN).§ Realization: 7UM6



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Restart inhibit function

A time between 15 min and 30 min is recommended if no data is available. The

longer time must be chosen for longer starts.

20 minMinimum restart inhibit

time

A value of 10 is recommended at short starting times. A value of 5 can be

selected at clearly longer starting times. At a starting time of 50s and a setting of

5 the release command for a possible restart is given after approximately 30 min.

10Extension of time constant

at stop

This time is considered practicable and also takes running down to stand still into

consideration.

Note: Restarting of the motor is not possible during this time. The time must be

set to zero if only a blocking is to take place when the thermal limit is reached.

1 minRotor temperature

equalization time,

Take this from the motor data sheet (technical data (3)); if values are missing

assume the value 2.

2Warm starts

Take this from the motor data sheet (technical data (3)); if values are missing

assume the value 3.3Cold starts

Choose the time to the current (technical data (3)).

If the motor starts clearly faster, e.g. in 2,6 s, you can be a little bit generous with

the setting. Here we choose the lowest setting value of 3 s.

3 sStarting time

Take this from motor data sheet – current at rated voltage (technical data (1) and

(3)).

5,65 I/ IN,MStarting currentCommentValueSetting parameters



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Starting time supervision

With reduced voltage the starting current amounts to 3,9 I/

IN,M

.

Due to the lower starting current a value of 2 I/I N,M was

selected.

The typical value of 2,5 I/IN,M

used for standard motors.

2 I/ IN,MStart selection

To this end, the specified starting time must be compared

with the characteristic curve times (technical data 3). Go

below the thermal charac-teristic if there is an adequate safety

clearance. According to the figure in technical data (2) a value

of 9s is permissible in the case of a starting current of 5,65 I/

IN,M

in the warm start state. For this current the motor starting

time is specified as 3 s.

Chosen permissible starting time: 6 s

6 sMaximum permissible

starting time

Take this from the motor data sheet

(technical data (1)).

5,65 I/ IN,MStarting current




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Restart inhibit function

Play with the starting time and starting current to find a compromise for the

setting values.

Use the values at rated voltage and reduced voltage.

Proceeding:

Select the variant with the lowest calculated time constant for safety reasons

2StwcStRotor I)n-(nt≈τ

Data:nc = 3; nw= 2

100% UN

Iat = 5,65tSt = 3 s

70% UN

ISt = 3,9tSt = 10 s

)n-(n

n k wc

cRotor ≈

1,73k Rotor ≈

s95,85,651s3 2Rotor =∗∗≈τ

s1523,91s102

Rotor =∗∗≈τ

Take the values at100 % UN for safetyreasons.

Compromise:Starting can be set to 4s,because a voltage dip is thenormal case during motorstarting (than the rotor time

constant is τ ≈ 128 s)



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Thermal characteristics

1 1.5 2 2.5 3 3.5 4 4.5 5 5.5 6 6.5 71

10

100

1 .103

1 .104

Overload coldOverload warmStarting time supervisionLocked rotor warm

rated motor current

t i m e i n s e c o n d

s

5.89 103×

1

t i( )

t v i( )

t A j( )

t Aw j( )

71 i i, j,

Stator overloadcold

warm

Characteristic ofstarting timesupervision

Locked rotor limit(warm)



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Restart inhibit functionStart at 100% voltage

Settings:

nc = 3nw = 2ISt = 5,65 I/In,M

tSt = 3 s

Internalcalculated:Tau = 94,3 skRotor = 1,7

Simulation:

ISt = 5,65tSt = 3 s0 50 100 150 200 250 300 350 400 450

0

0.2

0.4

0.6

0.8

1

Threshold

Rotor temperaturestarting current

Time in second s

R o t o r t e m p e r a t u r e a n d c

u r r e n t i n p . u .

1.2

0

WE ex

Tempi

Ii

4390 i delT⋅



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Restart inhibit functionStart at 70% voltage, blocking is more sensitive

Settings:nc = 3nw = 2ISt = 5,65 I/In,M

tSt = 3 s

Internalcalculated:Tau = 94,3 skRotor = 1,7

Simulation:ISt

= 3,9tSt = 10 s

0 50 100 150 200 250 300 350 400 450 5000

0.5

1

1.5

Threshold

Rotor temperaturestarting current

Time in seconds

R o t o r t e m p e r a t u r e a n d c

u r r e n t i n p . u .

1.5

0

WEex

Tempi

Ii

4600 i delT⋅

After the 2. reclosing theinhibit function will be active.



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Unbalanced load protection

s2000,1

s2

I

I

K t

22

MN,

zul.2,

downCooling ==

=

Use the following relationship:200 sCooling down time of the

thermal model

The conservative setting of 2 s is chosen if the motor manufacturer

does not specify any details. The time really ought to be longer

comparable to synchronous machines is presupposed.

2 sThermal unbalanced load time

((I2 / I

N,M)2 t = K)

(internal designation:

FACTOR K )

Two phase operation under rated condition leads to a negative

sequence current of about 66 %. Due to the power be produced, it

will rise and will certainly reach values of 100%.

A tripping delay of about 3 s is recommended to allow for transient

phenomena.

0,4 I2 / IN,MTripping stage

Unless otherwise is specified this value should be set.

If this stage should also trip, it must be delayed appropriately

(approx. 15 - 30 s);

Suggestion: 20 s.

0,1 I2 / IN,MContinuously permissible

unbalanced load




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Unbalanced load protectionDifferences in the devices

2 definite time negative sequence stages§ Negative sequence current and time delay can be set per stage§ Realization: 7SJ6

Thermal unbalanced load protection§ Reduced thermal model considers the heating and cooling down

(I22 t = K)

§ Model starts with a integration if the negative sequence current is overthe pick-up threshold

§ Realization: 7UM62§

Additional available: 1 alarm stage and 1 definite time stage



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Characteristics unbalanced load protection(negative sequence protection)

0.1 0.2 0.3 0.4 0.51

10

100

1 .103

Negative sequence th ermal K=2s

negative sequence current

t i m e i n s e c o n d s

200

1

3

20

t neg j( )

0.6.01

0.1 0.4

j

Definitetimestages

Thermalcharacteristic

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Protección de Motor