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Function Descript ion

The start of the function is initiated:via the device-internal protection function and/or externally (via binary

inputs or interface, for example, GOOSE). The start can be done 1-pole or 3-pole. Figure 6-356and

Figure 6-357showing the functionality.

Internal StartBy default, each device-internal protection stage, which has to control the local circuit breaker starts the

circuit-breaker failure protection. The function is started by the tripping of the protection stage. In case of

phase-selective tripping, the start will also be phase-selective. In addition, circuit-breaker failure protection is

started with 3-pole tripping of automatic reclosing (AREC). In the default setting, the starting signal

Internal start(see Figure 6-356) is held when the pickup signal has a falling edge or the protection

function has tripped. The CBFP function can in this case only dropout if the CB is detected to be open. This is

detected using the current flow or circuit-breaker auxiliary contact criterion. If necessary, the CBFP function

can also dropout when the pickup signal has a falling edge or the protection function trips (internal starting

signal is not held).

Where required, individual protection stages or protection functions can be routed so that they are excluded

as starting source. If all device-internal starting sources are excluded in this manner, the start must be initi-

ated externally.

Routing of the internal starting sources takes place in the protection function groups via the Circuit breaker

interactionentry (for this, see 2.1 Function Embedding in the Device , DIGSI 5 Project Tree (excerpt)).

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Figure 6-356 Internal CBFP Start

6.42.3

Protection and Automation Functions

6.42 Circuit-Breaker Failure Protection

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External Start

The parameter Start via binary inputis used to set whether the external start is initiated by a 1-

channel or 2-channel signal. The required routing of the input signals is compared with the setting. If a routing

is missing, an error message is generated. The Health signal changes to the state Warning.

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Figure 6-357 Configuration of the External Start of the CBFP Function

In 1-channel mode, start for 1-pole tripping is initiated only with the binary input signals >Start pole A,

>Start pole B, and >Start pole C. In the case of 3-pole tripping, start is initiated only with the input

signal >Start 3-pole(see Figure 6-358).

In 2-channel operation, to initiate the start, the binary input signal >Release 1-polemust be activated in

case of the 1-pole start, or >Release 3-polein case of the 3-pole start. In the default setting, the internal

starting signals External start Lxand External start 3poldrop out immediately when the binary

input signals have a falling edge (see Figure 6-358). If necessary, the internal start signal can be held. In this

case, the start remains active when the binary input signals have a falling edge.

The input signals are monitored to avoid an unwanted pickup of the function.

Static supervision (see Figure 6-358):If one of the binary starting and release signals is active for more than 15 s without a pickup of the func-

tion, an error in the binary input circuit is assumed. The corresponding signal is blocked to exclude an

external pickup of the function. A corresponding indication is issued, and the ready signal changes to the

stateWarning. The blocking is reset as soon as the binary input signal drops out.

This static supervision is disabled in the following cases:

a) On pickup of the CBFP (only in the case of an external start). This avoids an unwanted pickup of the

supervision if the external protection that starts the CBFP uses a lockout functionality. When the starting

signal drops out, the supervision is enabled again.

b) As long as the function (or the device) is in test mode. This allows to check the function without the

supervision blocking the function.

Dynamic supervision (see Figure 6-358):If one of the starting signals is active but no release signal is present after a settable supervision timehas elapsed, pickup is blocked and a corresponding indication is issued. The Health signal changes to

the state Warning. The blocking is reset with the dropout of the starting signal.

The binary input signals only take effect if the binary inputs are activated for at least 10 ms (SW filter, see

Figure 6-358).



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Figure 6-358 External Start of the CBFP, Logic

1-Pole or Multi-Pole Start

Based on the starting signals it is determined whether the start in question is 1-pole or multipole (see

Figure 6-359). This information is required for starting the various time delays.




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Figure 6-360 Current-Flow Criterion

Circuit-Breaker Auxiliary-Contact Criterion

Settings allow you to set whether the auxiliary contacts of the circuit breaker are permitted for determining the

circuit-breaker switch position. The following settings are possible:

In this function, circuit-breaker auxiliary contacts are not used for determining the CB position.

The position is determined (pole-selective) via the double-point indications Position Lx(from theCircuit breakerfunction block).

The double-point indication 3-pole position(from the Circuit breakerfunction block) is used todetermine whether all 3 poles of the circuit breaker are closed.

If the double-point indications are not routed, an error message is issued. The ready signal also changes to

the state Warning.

A detected static disturbed position (not an intermediate position) has the effect that the circuit breaker auxil-iary contact criterion is not used (the signalsAux.co.crit. CB Clsd Lxare inactive).




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Figure 6-361 Circuit-Breaker Auxiliary-Contact Criterion

Pickup/Dropout

After the start, a check is performed whether the circuit breaker or the individual circuit-breaker pole is closed.

The current-flow criterion and the circuit-breaker auxiliary-contact criterion are available for this purpose.

Even if the circuit-breaker auxiliary contact criterion is permitted, preference is given to the fulfilled current-

flow criterion because it is the most reliable criterion for determining whether the CB or CB pole is closed.

This means that the CB or CB pole is considered to be closed if it is closed according to the current-flow crite-

rion but, at the same time, open according to the circuit-breaker auxiliary contact criterion.If no current is flowing at the moment of start, the function can only pick up via the circuit-breaker auxiliary-

contact criterion. For this purpose, the circuit-breaker auxiliary contacts must be permitted as criterion. When

the current begins to flow after the start, the function switches over to the current-flow criterion.

If the circuit-breaker or a circuit-breaker pole is detected to be closed, the function picks up.

The pickup starts a time delay (see Delay/Tripping). While the delay is running, the system checks continu-

ously whether the circuit breaker or a CB pole has opened. In the default setting, the opening of the CB is

checked on the basis of the currently valid criterion, which is normally the current-flow criterion because it is

preferred. If until expiration of the time delay, no current flow above the set threshold values has been

detected, the circuit-breaker auxiliary-contact criterion becomes effective.

The function has also a setting in which dropout is only possible if both criteria detect in parallel the CB or CB

pole to be open (dropout with auxiliary contact and current-flow criterion).

In the default setting, the internal starting signal is held (see Figure 6-356and Figure 6-358). This means thatdropout is controlled solely by the current-flow or circuit-breaker auxiliary-contact criterion. If dropout is also to

occur on the falling edge of the starting signal (that is, when the pickup signal has a falling edge or the protec-

tion function trips), holding of the start signal must be disabled.




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Figure 6-362 Pickup/Dropout of the CBFP

Delay/Tripping

In a first step, tripping at the local CB can be repeated. Tripping is repeated after expiration of the settabledelay T1. You can set various T1 times for a 1-pole and multipole start. In case of a 1-pole start, tripping can

be repeated in a 1-pole or 3-pole way depending on the setting.

Time delay T2 (backup tripping) can be started in parallel with time T1 or after expiration of time T1. You can

set various T2 times for a 1-pole and multipole start.

If the assigned 1-pole period is initially started by a 1-pole start and a multiphase short circuit and multiphase

start occur subsequently, the corresponding multiphase period is also started so that the 2 periods run in

parallel. Tripping is determined by the period that expires first.

When there is a 1-pole start with 3-pole trip repeat, the 3-pole T2 time is started.

If time delay T2 expires without a dropout of the function, a circuit-breaker failure is assumed, and the backup

tripping signal Trip T2is generated. This tripping is always 3-pole. If the device is equipped with a protec-

tion interface, a transfer trip signal can be sent to the opposite end if necessary (see chapter Protection inter-

face3.5.3.1 Overview of Functions

).If the >CB defectinput signal is valid, any repetition of the trip signal is suppressed, and the backup tripping

signal T2 is generated immediately (without delay). The corresponding binary input must be activated for at

least 20 ms before the input signal >CB defectbecomes valid.

TheMinimum operate timeparameter defines the minimum duration for tripping the function. In contrast

to other protection functions, the parameter is set within its own function. As a result, the setting is inde-

pendent of the identically named comprehensive parameter that is set in the Device settings.




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Figure 6-363 Delay/Tripping of the CBFP

Appl icat ion and Setting Notes

Figure 6-364gives an overview of the functions involved in an external start of the CBFP function.In the case

of an internal start, there is no external protection device and the protection functionality is located in the

CBFP device.

6.42.4




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Figure 6-364 Circuit-Breaker Failure Protection with External Pole-Selective Start, Pole-Selective Tripping

Repetition, and 3-Pole Tripping (T2)

Routing: Configuration of Internal Starting Sources (Internal Protection Function)

Configuration of the internal starting sources takes place in the protection function groups via the Circuit

breaker interactionentry (for this see 2.1 Function Embedding in the Device , Figure 2-4).

By default, the function can be started by any tripping of the internal protection functions, which control the

local circuit breaker. Depending on the specific application, it may be necessary to exclude certain device-

internal protection functions from starting the CBFP. For instance, busbar disconnection following a localcircuit-breaker failure may be undesirable in the case of load-shedding applications or ground faults in

isolated/resonant-grounded systems.

Where a start exclusively from external sources is required, all internal protection functions must be routed so

that they are excluded as starting source.

Parameter: Start via binary input

Default setting (_:107) Start via binary input= no

Parameter Value Description

no If no external start is intended, the parameter is set to no.




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with position

with position phsx

The auxiliary contacts are permitted as a further criterion in applications (see

the following examples) where the current is no reliable criterion for deter-

mining the circuit-breaker position.

When the protection trips phase-segregated, it makes sense to link also the

auxiliary contacts to the device phase-segregated to ensure a pole-selective

detection of the position To do so, select with Position phsx.If pole-selective detection is not possible, set with Position. Observe that

the CB is deemed open as soon as the 1st pole has opened.

EXAMPLES

Appl ications wh ich require you to permit the circui t-breaker auxi liary-contact cr iterion:

Tripping of the high and low voltage side CB on the transformer: If only one of the 2 CBs trips, there isno more current flow.

Tripping of protection functions whose tripping decision is not based on current measurement in combi-nation with low-load situations.

Injection of the tripping signal from Buchholz protection

Parameter: Dropout

Recommended setting value (_:104) Dropout= with effective criterion

The parameter Dropoutis available if the circuit-breaker auxiliary-contact criterion is permitted (see param-

eter CB aux.cont. crit. allowed).


with effective

criterion

Siemens recommends keeping the default setting, because it prefers the

current as a reliable criterion for detection of an open CB and thus for dropout

of the CBFP function.

w. aux.c. and

curr.crit.

Select this setting for applications on transformers or generators (see the

preceding examples) in which the current flow is such that the current is nolonger a reliable criterion for detecting the opening of the CB.

Parameter: Retrip

Default setting (_:110) Retrip after T1= no


no Where no redundant CB control is provided, a repetition of the trip signal to the

local CB is not required.

start T2 after T1 Where a redundant CB control (2nd trip coil with 2 trip circuits) is provided, a

repetition of the trip signal to the local CB makes sense.

Siemens recommends the setting start T2 after T1because it provides a

clear chronological separation of the processes for trip repeat and backup trip-ping. Remember here that the overall fault-clearance time in case of a failure of

the local CB is the sum of T1 and T2.

parallel start T2,

T1

Alternatively to setting start T2 after T1, you can startparallel

start T2, T1.

Parameter: Delay T1 for 1-pole retrip , Delay T1 3-pole retr ip

Default setting (_:113) Delay T1 for 1-pole retrip= 0.05 s

Default setting (_:111) Delay T1 for 3-pole retrip= 0.25 s

The parameters are visible only when the repetition of tripping is set.




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For most applications, the time delays for the 1-pole and the 3-pole (multipole) start are set equally.

The setting depends on the user's philosophy.

The following settings make sense:

If the minimum fault-clearing time has top priority, Siemens recommends setting the time to 0. Thissetting causes initiation of the retrip immediately upon the start. The drawback is that a defect of the 1st

trip circuit is not detected.

With a small time delay of, for instance, 50 ms, the defect of the 1st trip circuit can be detected based onthe analysis of the fault record.

With a long time delay which reliably ensures the dropout of the CBFP with the CB open, the rising edgeindication of the trip repeat Retrip T1is a sure signal for a fault in the 1st trip circuit. The following

example shows how this time is determined.

EXAMPLE

Determining the T1 Time that Reliably Ensures the Dropout of the CBFP with the CB Open:

Time of device binary output (when tripping is

caused by the device-internal protection)

5 ms

CB inherent time up to power interruption 2 periods (assumed rated frequency = 50 Hz)

Dropout time of CBFP function 1 period

Subtotal 65 ms

Safety Factor 2

Total (time T1) 130 ms

EXAMPLE

Different T1 times, depending on whether the start was 1-pole or 3-pole:

The protection tripping can be 1-pole. 1-pole tripping results in a 1-pole AR. The trip repeat prompted by the

CBFP should be 3-pole on principle.

Under these circumstances, the T1 time can be set short (for example 50 ms) in a 3-pole start. The T1 time

for 1-pole start, however, must be set to the full clearance time (for example 130 ms) because the two fault-free phases are to be tripped only in case of an authentic circuit-breaker failure.

Parameter: Delay T2 1-pole, Delay T2 3-pole

Default setting (_:114) Delay T2 for 1-pole trip= 0.13 s

Default setting (_:112) Delay T2 for 3-pole trip= 0.13 s

This setting has to ensure that after opening of the local CB the function drops out reliably and that backup

tripping is avoided under all circumstances. The setting depends on the parameter Retrip after T1.

If T2 is started afterT1, there is no need to consider the time T1 for the setting of T2.

EXAMPLE

Determining the T2 Time that Reliably Ensures the Dropout of the CBFP with the CB Open:

Time of binary device output

(when tripping is caused by device-internal

protection)

5 ms

CB inherent time up to power interruption 2 periods (assumed rated frequency = 50 Hz)

Dropout time of CBFP function 1 period

Subtotal 65 ms

Safety Factor 2

Total (time T2) 130 ms




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If T1 and T2 are started in parallel, take into account the time T1 for the setting of T2.

EXAMPLE

Simultaneous start of T2 and T1

Time for a reliable dropout after the local CB has

opened

130 ms

Setting of T1 50 ms

Total (= T2) 180 ms

Various times can be set for a 1-pole and 3-pole (multipole) start. In the presence of 1-phase short circuits

that do not jeopardize network stability it can make sense to allow more time to the local CB (such as twice

the clearance time: 2 x 130 ms = 260 ms), expecting that the CB will open yet. This way, tripping of the

surrounding CBs can be avoided.

Parameter: Minimum operate time

Default setting (_:115) Minimum operate time= -

TheMinimum operate timeparameter is used to set the minimum duration for tripping the function.

! CAUTIONDo not set a time that is too short.

If you set a time that is too short, there is a danger (dropout of the function without the current-

flow criterion) that the device contacts will interrupt the control circu it. If this happens, the device

contacts will burn out.

Set a duration that is long enough to ensure that the circuit breaker reliably reaches its final position

(open) after a control operation.

Input signal: >CB defect

The input signal >CB defecthas a preset filtering time of 20 ms. This filtering time prevents the input signal

from becoming effective in the case of a transient activation of the physical binary input, which can be caused

by the pressure change when the CB opens.

This time can be set to 0 if such a transient response of the physical binary input can be excluded due to the

CB design.

Output signal: Retrip T1

The output signal Retrip T1must be explicitly routed to a binary output.

If only one control circuit is available for the local CB, the output signal must be routed to the binary output to

which the general CB trip command (command Position) is routed.If a 2nd control circuit is present, the Retrip T1output signal must be routed to the associated binary

output.

Output signal: Trip T2

In order to operate the adjacent circuit breakers, the backup tripping (indication Trip T2) must be routed to

a binary output; andif necessary, to an interface (intertripping to opposite end).




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