SIFANG CSC-161 User manual

CSC-161

Line Protection IED

Product Guide

Version V1.10

Doc. Code: 0SF.492.052(E)

Issued Date 2012.8

Copyright owner: Beijing Sifang Automation Co., Ltd.

Note: The company keeps the right to perfect the instruction. If equipments do not agree with the

instruction at anywhere, please contact our company in time. We will provide you with corresponding

service.

®

is registered trademark of Beijing Sifang Automation Co., Ltd.

We reserve all rights to this document, even in the event that a patent is issued and a different

commercial proprietary right is registered. Improper use, in particular reproduction and dissemination

to third parties, is not permitted.

This document has been carefully checked. If the user nevertheless detects any errors, he is asked to

notify us as soon as possible.

The data contained in this manual is intended solely for the IED description and is not to be deemed

to be a statement of guaranteed properties. In the interests of our customers, we constantly seek to

ensure that our products are developed to the latest technological standards as a result; it is possible

that there may be some differences between the hardware/software product and this information

product.

Manufacturer:

Beijing Sifang Automation Co., Ltd.

Overview

1

CSC-161 is selective, reliable and high

speed comprehensive transmission line

protection IED (Intelligent Electronic

Device) for overhead lines, cables or

combination of them. It is a proper solution

for following applications:

 Subtransmission network and

distribution network, with solidly earthed

(grounded), low-resistance earthed,

isolated or compensated neutral point

 All type of station arrangement, such as

1.5 breakers arrangement, double bus

arrangement, etc.

 Short lines

 Heavily loaded lines

 For three pole operated circuit breaker

 Communication with station automation

system

The IED provides a highly sensitive and

reliable distance protection with innovative

and proven quadrilateral characteristic. In

addition to separated zone extension

functionality, five distance zones have fully

independent measuring and setting values

which gives high flexibility for all types of

lines and fault resistances. Many other

functions are integrated to provide a

complete backup protection library.

The wide application flexibility makes the

IED an excellent choice for both new

installations and retrofitting of the existing

stations

.

Feature

2

 Protection and monitoring IED with

extensive functional library, user

configuration possibility and expandable

hardware design to meet with user’s

special requirements

 Redundant A/D sampling channels

guarantee the high security and

reliability of the IED

 Three tripping/reclosing

 Highly sensitive startup elements, which

enhance the IED sensitivity in all

disturbance conditions and avoid

maloperation

 Current sudden-change startup

element

 Zero sequence current startup

element

 Over current startup element

 Undervoltage startup element for

weak-infeed end of line

 Three kinds of faulty phase selectors are

combined to guarantee the correction of

phase selection:

 Current sudden-change phase

selector

 Zero sequence and negative

sequence phase selector

 Under voltage phase selector

 Four kinds of directional elements

cooperate each other so as to determine

the fault direction correctly and promptly:

 Memory voltage directional element

 Zero sequence component

directional element

 Negative sequence component

directional element

 Impedance directional element

 Full scheme phase-to-phase and

phase-to-earth distance protection with

five quadrilateral protection zones and

additional extension zone characteristic

(21, 21N)

 Power swing function (68)

 Proven and reliable principle of

power swing logic

 Unblock elements during power

swing

 All useful types of tele-protection

scheme (85)

 Permissive Underreach Transfer

Trip (PUTT) scheme

 Permissive Overreach Transfer Trip

(POTT) scheme

 Blocking scheme

 Inter-tripping scheme

 Particular logic for tele-protection

scheme

 Current reversal

 Weak-infeed end

 Evolving fault logic

 Sequence tripping logic

 A complete protection functions library,

include:

 Distance protection with

quadrilateral characteristic

(21,21N)

 Power swing function (68)

 Tele-protection scheme based on

Feature

3

distance protection (85-21,21N)

 Tele-protection scheme based on

dedicated earth fault protection

(85-67N)

 Overcurrent protection (50, 51, 67)

 Earth fault protection (50N, 51N,

67N)

 Emergency/backup overcurrent

protection (50, 51)

 Emergency/backup earth fault

protection (50N, 51N)

 Switch-onto-fault protection

(50SOTF)

 Overload protection (50OL)

 Overvoltage protection (59)

 Undervoltage protection (27)

 Circuit breaker failure protection

(50BF)

 Poles discordance protection

(50PD)

 Dead zone protection (50DZ)

 STUB protection (50STUB)

 Synchro-check and energizing

check (25)

 Auto-reclosing function for single-

and/or three-phase reclosing (79)

 Voltage transformer secondary

circuit supervision (97FF)

 Current transformer secondary

circuit supervision

 Self-supervision to all modules in the

IED

 Complete IED information recording:

tripping reports, alarm reports, startup

reports and general operation reports.

Any kinds of reports can be stored up to

2000 and be memorized in case of

power disconnection

 Remote communication

 Tele-protection contacts for power

line carrier protection interface

 Up to two fiber optical remote

communication ports for protection

function, like tele-protection, used

up to 100kM single–mode optical

fiber cable

 External optical/electrical converter,

which support communication

through SDH or PCM, for G.703

(64kbit/s) and G.703E1 (2048kbit/s)

 Up to three electric /optical Ethernet

ports can be selected to communicate

with substation automation system by

IEC61850 or IEC60870-5-103 protocols

 Up to two electric RS-485 ports can be

selected to communicate with substation

automation system by IEC60870-5-103

protocol

 Time synchronization via network

(SNTP), pulse and IRIG-B mode

 Configurable LEDs (Light Emitting

Diodes) and output relays satisfied users’

requirement

 Versatile human-machine interface

 Multifunctional software tool for setting,

monitoring, fault recording analysis,

configuration, etc.

Function

4

Protection functions

Description

ANSI Code

IEC 61850

Logical Node

Name

IEC 60617

graphical symbol

Distance protection

21, 21N

PDIS

Z<

Power-swing function

68

RPSB

Zpsb

Tele-protection

Communication scheme for distance

protection

85–21,21N

PSCH

Communication scheme for earth fault

protection

85–67N

PSCH

Current protection

Overcurrent protection

50,51,67

PTOC

3IINV>

3I >>

3I >>>

Earth fault protection

50N, 51N, 67N

PEFM

I0INV>

I0>>

I0>>>

Emergency/backup overcurrent protection

50,51

PTOC

3IINV>

3I >

Emergency/backup earth fault protection

50N,51N

PTEF

I0INV>

I0 >

Switch-onto-fault protection

50SOTF

PSOF

3I >SOTF

I0>SOTF

Overload protection

50OL

PTOC

3I >OL

Voltage protection

Overvoltage protection

59

PTOV

3U>

3U>>

Undervoltage protection

27

PTUV

3U<

3U<<

Breaker protection and control function

Circuit breaker failure protection

50BF

RBRF

3I> BF

I0>BF

I2>BF

Dead zone protection

50DZ

3I>DZ

Function

5

I0>DZ

I2>DZ

STUB protection

50STUB

PTOC

3I>STUB

Poles discordance protection

50PD

RPLD

3I< PD

I0>PD

I2>PD

Synchro-check and energizing check

25

RSYN

Auto-reclosing

79

RREC

O→I

Single- and/or three-pole tripping

94-1/3

PTRC

Secondary system supervision

CT secondary circuit supervision

VT secondary circuit supervision

97FF

Monitoring functions

Description

Redundant A/D sampling data self-check

Phase-sequence of voltage and current supervision

3I0 polarity supervision

The third harmonic of voltage supervision

Synchro-check reference voltage supervision

Auxiliary contacts of circuit breaker supervision

Broken conductor check

Self-supervision

Logicality of setting self-check

Fault locator

Fault recorder

Station communication

Description

Function

6

Front communication port

Isolated RS232 port for maintaining

Rear communication port

0-2 isolated electrical RS485 communication ports, support IEC 60870-5-103 protocol

0-3 Ethernet electrical/optical communication ports, support IEC 61850 protocol or IEC 60870-5-103

protocol

Time synchronization port, support GPS pulse or IRIG-B code

Remote communication

Description

Communication port

Contact(s) interface for power line carrier for tele-protection

0– 2 fiber optical communication port(s) for tele-protection

Connection mode

Direction fiber cable connection

Digital communication network through converter

IED software tools

Functions

Reading measuring value, IED report

Setting

IED testing

Disturbance recording analysis

IED configuration

Printing

Function

7

21 Z<

PDIS

21N

FL

RFLO

Z<

PDIS

59 3U>

PTOV

27 3U<

PTUV

25

79 O→ I

RREC

MONITORING

STATION

COMMUNICATION

MEASUREMENT

50 3I>>>

PIOC

50N I0>>>

PIEF

PTOC

51/67 3I>>,3I>

51N/67N I0>>,I0>

PTEF

50SOTF

PSOF

50BF

RBRF

3I>BF 50STUB 3I>STUB

PTOC

94

PTRC

- RS232/485

- RJ45/FO

- IEC61850

- IEC60870-5-103

RSYN

50DZ

Fault recording

50PD PD

RPLD

68

RPSB

Zpsb

85-21

85-67N

PSCH

PLC Protection

interface 1

PLC Protection

interface 2

Remote

Communication

Ports

FO CONNECTION

Protection

8

Startup elements

The startup elements basically work as

sensitive detector to all types of fault. As

soon as fault or disturbance happens, the

highly sensitive startup elements will

operate immediately and initiate all

necessary protection functions for

selective clearance of the fault.

The control circuit of tripping relays is

controlled by the startup elements. Only

when one of the startup elements is

triggered, the tripping relays can be

energized to trip. Thus, the maloperation,

due to fatal internal hardware fault, is

avoided in this way.

Based on different principle, there are four

kinds of startup elements listed below,

which are used to enhance the sensitivity,

and to guarantee the security in case of

IED’s internal hardware faults.

Sudden-change current startup

element

Sudden-change phase to phase or zero

sequence current elements are the main

startup element that can sensitively detect

most of faults. The criteria are as follows:

 

or



where:

Δi=|| i (K) - i (K-T) | - |i (K-T) - i

(K-2T) ||

: AB,BC or CA, e.g. iAB= iA-iB

K: The present sample

T: The sample quantity of one power cycle

Δ3i0: Sudden-change zero sequence current

I_Abrupt: The setting value of current

sudden-change elements

Zero sequence current startup

element

Zero sequence current startup element is

applied to improve the fault detection

sensitivity at the high resistance earth

faults. As an auxiliary startup element, it

operates with a short time delay.

Overcurrent startup element

If overcurrent protection function is

enabled, over current startup element is

used to improve the fault detection

sensitivity. As an auxiliary startup element,

it operates with short time delay.

Low-voltage startup element

When one end of the protected line is a

weak-source system, and the fault

sudden-change phase to phase current is

too low to startup the IED, low-voltage

startup element can be in service to startup

the tele-protection scheme with weak-echo

logic.

Phase selector

The IED applies different phase selectors

to determine the faulty phase to make

tripping or Auto-reclosing initiation

correctly. There are three kinds of phase

selectors based on different principle for

different fault stages.

Sudden-change current phase

selector

It operates as soon as the sudden- change

current startup element starts up. It makes

a phase selection for fast tripping by

Protection

9

comparison amongst changes of

phase-phase currents, iAB, iBC and

iCA.

Symmetrical component phase

selector

During the whole period of fault, the phase

selector checks the angle between

negative sequence current and zero

sequence current vectors to determine

faulty phases. In addition, phase to phase

faults will be discriminated through

impedance characteristic.

Low voltage phase selector

Both current sudden-change phase and

symmetric component phase selector are

not applicable for weak-infeed end of

protected line, so low-voltage phase

selector is employed in this condition

without VT failure. Theoretically, when one,

two or three phase voltages reduce, the

relevant phase(s) is selected as faulty

phase.

Directional elements

Four kinds of directional elements are

employed for reliable determination of

various faults direction. The related

protection modules, such as distance

protection, tele-protection schemes and

overcurrent and earth fault protections,

utilize the output of the directional

elements as one of their operating

condition. All the following directional

elements cooperate with the mentioned

protection functions.

Memory voltage directional

element

The IED uses the memory voltage and

fault current to determine the direction of

the fault. Therefore transient voltage of

short circuit conditions doesn’t influence

the direction detection. Additionally, it

improves the direction detection sensitivity

for symmetrical or asymmetrical close-in

faults with extremely low voltage. But it

should be noted that the memory voltage

cannot be effective for a long time.

Therefore, the following directional

elements work as supplement to detect

direction correctly.

Zero sequence component

directional element

Zero-sequence directional element has

efficient features in the solidly grounded

system. The directional characteristic only

relates to zero sequence impedance angle

of the zero sequence network of power

system, regardless of the quantity of load

current and/or fault resistance throughout

the fault. The characteristic of the zero

sequence directional element is illustrated

in

Figure 1.

Forward

Φ0_Char

Bisector

0_Ref

3

U

0°

-3I0

3I090°

Figure 1 Characteristic of zero sequence

directional element

where:

Protection

10

Ф0_Char: The settable characteristic angle

Negative sequence component

directional element

Negative sequence directional element

can make an accurate directional

discrimination in any asymmetric fault. The

directional characteristic only relates to

negative sequence impedance angle of the

negative sequence network of power

system, regardless the quantity of load

current and/or fault resistance throughout

the fault. The characteristic of the negative

sequence directional element is illustrated

in Figure 2.

Forward

Φ2_Char

I

32

I

-3 2

3Ref

U2_

0°

90°

Bisector

Figure 2 Characteristic of negative sequence

directional element

where:

Ф2_Char: The settable characteristic angle

Impedance directional

elements

The characteristic of the impedance

directional element (shown in Figure 3) is

same with that of distance protection.

X

R

R_Set

Forward

Reverse

X_Set

-n∙X_Set

-n∙R_Set

Figure 3 Direction detection characteristic of

impedance directional element

where:

RSET: The resistance setting of relevant zone

of distance protection

XSET: The reactance setting of relevant zone

of distance protection

n: Multiplier for reverse directional element,

which make the reverse directional

element more sensitive than forward one

Distance protection

(21, 21N)

The transmission line distance protection

provides a five zones full scheme

protection with all phase to phase faults

and phase to earth fault loops

independently for each zones. Zone

arrangement illustrated in Figure 4.

Additionally, one extension zone is

employed to co-operate with Auto-

-reclosing and tele-protection schemes.

Protection

11

R

Zone 1

X

Zone 2

Zone 3

Zone 4

Zone 5

Zone 4 Reverse

(optional)

Zone 5 Reverse

(optional)

Zone Ext.

Figure 4 Distance protection zones

Individual settings of resistive and reactive

reach for phase to phase and phase to

earth fault of each zone give flexibility for

application on overhead lines and cables

of different types and lengths, considering

different fault resistance for phase to

phase and phase to ground short circuits.

Characteristic of distance

protection

The IED utilizes quadrilateral characteristic

as shown in Figure 5.

X

R

X_ZSet

R_ZSet

Φ_ZTop

Φ_ZBottom

Φ_ZLeft Φ_ZRight

Figure 5 Characteristics of distance protection

where:

R_ZSet: R_ZnPP or R_ZnPE;

X_ZSet: X_ZnPP or X_ZnPE;

R_ZnPP: Resistance reach setting for phase

to phase fault. Subscript n means the

number of protection zone. Subscript PP

means phase to phase fault

R_ZnPE: Resistance reach setting for phase

to earth fault. Subscript X means the

number of protection zone. Subscript PE

means phase to earth fault

X_ZnPP: Reactance reach setting for phase

to phase fault

X_ZnPE: Reactance reach setting for phase

to earth fault

Φ_ZTop: The upper boundary angle of the

characteristic in the first quadrant is

designed to avoid distance protection

overreaching when a close-in fault

happens on the adjacent line

Φ_ZBottom: The bottom boundary angle of

the characteristic in the fourth quadrant

improves the reliability of the relay to

operate reliably for close-in faults with arc

resistance

Φ_ZRight: The right boundary angle of

characteristic in the first quadrant is used

to deal with load encroachment problems

Φ_ZLeft: The left boundary angle of the

characteristic in the second quadrant

considers the line impedance angle which

generally is not larger than 90°. Thus this

angle guarantees the correct operation of

the relay

Extended operating

characteristic

To ensure the correct operation at close-in

faults, a rectangle zone covering the

Protection

12

original point is added to the quadrilateral

characteristic. The rectangular offset

characteristic (illustrated in Figure 6) is

calculated automatically according to the

related distance zones settings.

Furthermore, the memory voltage direction

element, the zero sequence directional

element, and the negative sequence

direction element are applied to determine

the direction together.

X

R

XSet

RSet

ΦTop

ΦBottom

ΦLeft ΦRight

XOffset

ROffset

Figure 6 Extended polygonal distance protection

zone characteristic

Reverse zone characteristic

In addition to the forward characteristic

zones mentioned above, the IED provides

two optional reverse zone characteristics

to protect connected busbar as a backup

protection. The reverse zone characteristic

can be set for zones 4 and 5 individually.

This reverse characteristic has been

shown in Figure 7.

X

R

-X_ZSet

-R_ZSet

Figure 7 Characteristic distance protection

reverse zone

Switch-onto- fault protection

function

Under either auto reclosing or manual

closing process, the protection function is

able to discriminate these conditions to

give an instantaneous tripping once the

circuit breaker is closed on permanent

faulty line.

Power swing (68)

The IED provides a high reliable power

swing detector which discriminates

between fault and power swing with

different algorithm.

Power swing blocking logic

According to the slow behavior of power

swing phenomenon, once one of the two

following conditions is met, the protection

program will switch to power swing logic

process:

 Without operation of sudden-change

current startup element, all

phase-to-phase impedances, ZAB, ZBC

Protection

13

and ZCA enter into the largest zone of

distance protection

 Without operation of sudden-change

current startup element, all phase

currents are bigger than the power

swing current setting

In addition, according to the experimental

results of power swing, it is not possible for

impedance vector to come into protected

zones in 150 ms after triggering of the

current sudden- -change startup element.

After 150 ms, the protection program will

be switched to power swing logic process if

no tripping is issued.

Therefore, according to the above

condition, the IED program enters the

power swing logic process and the

distance protection is blocked until

removing of the mentioned conditions or

until a fault occurrence in the protected

line.

Power swing unblocking logic

The unblocking logic provides possibility

for selective tripping of faults on

transmission lines during system

oscillations, when the distance protection

function is normally blocked. In order to

unblock distance protection and therefore,

fast clearing of the faults, the following

elements are in service to discriminate

between an internal fault and power swing

conditions.

 Asymmetric faults detection element

The zero and negative sequence

current are always the key features of

the asymmetric fault. By comparison

amongst the positive, negative and

zero sequence component of phase

current, the element distinguishes the

asymmetric fault from power swing.

 Three phase fault detection element

Based on the experimental results and

practical proof, the change rate of

measuring resistance and the change

vector of measuring impedance are

combined to detect the three phase

fault during the power swing.

Tele-protection

scheme for distance

protection (85-21)

To achieve non-delayed and selective

tripping on 100 % of the line length for all

faults, the communication scheme logic is

provided for distance protection. The

communication schemes are as follows:

 Permissive Overreach Transfer Trip

(POTT)

 Permissive Underreach Transfer Trip

(PUTT)

 Blocking scheme

Following protection logic are used to

ensure correct operation under some

special fault conditions:

 Current reversal logic

 Weak-infeed end and echo logic

 Evolving fault logic

 Sequence tripping logic

Direct Transfer Trip

The function is provided to cooperate with

related local protection IED, such as

busbar protection, breaker failure

protection, etc., to trip the opposite end

circuit breaker.

Protection

14

Tele-protection

scheme for earth fault

protection (85-67N)

To achieve highly sensitive and selective

tripping on 100 % of the line length for all

faults, especially at the high resistance

earth faults. It always works as

complement to tele-protection for distance

protection with a short time delay.

Permissive transfer trip communication

scheme is applied.

The protection provides dedicated current

and time elements independent of the

earth fault protection.

Following protection logic are used to

ensure correct operation under some

special fault conditions.

 Current reversal logic

 Weak-infeed end logic

 Sequence tripping logic

Direct Transfer Trip

The function is provided to cooperate with

related local protection IED, such as

busbar protection, breaker failure

protection, etc., to trip the remote end

circuit breaker.

Overcurrent protection

(50, 51, 67)

The protection provides following features:

 Two definite time stages

 One inverse time stage

 11 kinds of IEC and ANSI inverse time

characteristic curves as well as

optional user defined characteristic

 Settable directional element

characteristic angle, to satisfy the

different network conditions and

applications

 Each stage can be set individually as

directional/non-directional

 Each stage can be set individually for

inrush restraint

 Cross blocking function for inrush

detection

 Settable maximum inrush current

 VT secondary circuit supervision for

directional protection. Once VT failure

happens, the directional stage can be

set to be blocked

Inrush restraint function

The protection relay may detect large

magnetizing inrush currents during

transformer energizing. In addition to

considerable unbalance fundamental

current, inrush current comprises large

second harmonic current which does not

appear in short circuit current. Therefore,

the inrush current may affect the protection

functions which operate based on the

fundamental component of the measured

current. Accordingly, inrush restraint logic

is provided to prevent overcurrent

protection from maloperation.

Furthermore, by recognition of the inrush

current in one phase, it is possible to set

the protection in a way that not only the

phase with the considerable inrush current,

but also the other phases of the

overcurrent protection are blocked for a

certain time. This is achieved by

cross-blocking feature integrated in the

Protection

15

IED.

The inrush restraint function has a

maximum inrush current setting. Once the

measuring current exceeds the setting, the

overcurrent protection will not be blocked

any longer.

Characteristic of direction

element

The direction detection is performed by

determining the position of current vector

in directional characteristic. In other word,

it is done by comparing phase angle

between the fault current and the reference

voltage, Figure 8 illustrates the direction

detection characteristic for phase A

element.

Forward

UBC_Ref

ΦPh_Char

IA

-

0°

90°

Bisector

Figure 8 Direction detection characteristic of

overcurrent protection directional element

where:

ФPh_Char: The settable characteristic angle

The assignment of the applied measuring

values used in direction determination has

been shown in Table 1 for different types of

faults.

Table 1 Assignment of applied current and

reference voltage for directional element

Phase

Current

Voltage

A

a

I

bc

U

B

b

I

ca

U

C

c

I

ab

U

For three-phase short-circuit fault, without

any healthy phase, memory voltage values

are used to determine direction clearly if

the measured voltage values are not

sufficient. The detected direction is based

on the memory voltage of previous power

cycles.

Earth fault protection

(50N, 51N, 67N)

The earth fault protection can be used to

clear phase to earth faults as system

back-up protection.

The protection provides following features:

 Two definite time stages

 One inverse time stage

 11 kinds of the IEC and ANSI inverse

time characteristic curves as well as

optional user defined characteristic

 Zero sequence directional element

 Negative sequence directional element

is applied as a complement to zero

sequence directional element. It can be

enabled/disabled by setting

 Each stage can be set individually as

directional/non-directional

 Settable directional element

characteristic angle, to satisfy the

different network conditions and

applications

Protection

16

 Each stage can be set individually for

inrush restraint

 Settable maximum inrush current

 VT secondary circuit supervision for

directional protection function. Once

VT failure happens, the directional

stage can be set to be blocked

 CT secondary circuit supervision for

earth fault protection. Once CT failure

happens, all stages will be blocked

 Zero-sequence current is measured

from earth phase CT

Directional element

The earth fault protection adopts zero

sequence directional element which

compares the zero sequence system

quantities:

 3I0, current is measured from earth

phase CT

 3U0, the voltage is used as reference

voltage. It is calculated from the sum of

the three phase voltages

Forward

Φ0_Char

Bisector

0_Ref

3U

0°

-3I0

3I090°

Figure 9 Direction detection characteristic of

zero sequence directional element

where:

Ф0_Char: The settable characteristic angle

For earth fault protection, users can

choose negative sequence directional

element as the complement of zero

sequence directional element. It can be

used in case of too low zero sequence

voltage due to some fault condition e.g. the

unfavorable zero-sequence voltage. The

negative sequence directional element

characteristic is shown in Figure 10.

Forward

Φ2_Char

I

32

I

-3 2

3Ref

U2_

0°

90°

Bisector

Figure 10 Direction detection characteristic of

negative sequence directional element

where:

Ф2_Char: The settable characteristic angle

Furthermore, under the VT failure situation,

it can be set to block directional earth fault

protection.

Inrush restraint function

The protection relay may detect large

magnetizing inrush currents during

transformer energizing. In addition to

considerable unbalance fundamental

current, Inrush current comprises large

second harmonic current which doesn’t

appear in short circuit current. Therefore,

Protection

17

the inrush current may affect the protection

functions which operate based on the

fundamental component of the measured

current. Accordingly, inrush restraint logic

is provided to prevent earth fault protection

from mis-tripping.

Since inrush current cannot be more than a

specified value, the inrush restraint

provides an upper current limit in which

blocking does not occur.

Emergency/backup

overcurrent protection

(50, 51)

In the case of VT fail condition, all distance

zones and protection functions related with

voltage input are out of service. In this

case, an emergency overcurrent protection

comes into operation.

Additionally, the protection can be set as

backup non directional overcurrent

protection according to the user’s

requirement.

The protection provides following features:

 One definite time stage

 One inverse time stage

 11 kinds of IEC and ANSI inverse

characteristics curve as well as

optional user defined characteristic

 Inrush restraint function can be set for

each stage separately

 Cross blocking of inrush detection

 Settable maximum inrush current

Emergency/backup

earth fault protection

(50N, 51N)

In the case of VT fail condition, all distance

zones and protection functions related with

voltage input are out of operation. An

emergency earth fault protection comes

into operation.

Additionally, the protection can be set as

backup non directional earth fault

protection according to the user’s

requirement.

The protection provides following features:

 One definite time stage

 One inverse time stage

 11 kinds of IEC and ANSI inverse

characteristics curve as well as

optional user defined characteristic

 Inrush restraint can be selected

individually for each stage

 Settable maximum inrush current

 CT secondary circuit supervision for

earth fault protection. Once CT failure

happens, all stages will be blocked

 Zero-sequence current is measured

from 3-phase currents summation

Switch-onto-fault

protection (50SOTF)

The protection gives a trip when the circuit

breaker is closed manually onto a short

circuited line.

The protection provide following features:

Protection

18

 One definite time overcurrent stage

 One definite time earth fault protection

stage

 Inrush restraint can be selected

 Cross blocking for inrush detection

 Settable maximum inrush current

 Manual closing binary input detection

Overload protection

(50OL)

The IED supervises load flow in real time.

If each phase current is greater than the

dedicated setting for a set delay time, the

protection will issue alarm.

Overvoltage protection

(59)

The overvoltage protection detects

abnormally network high voltage

conditions. Overvoltage conditions may

occur possibly in the power system during

abnormal conditions such as no-load,

lightly load, or open line end on long line.

The protection can be used as open line

end detector or as system voltage

supervision normally.

The protection provides following features:

 Two definite time stages

 Each stage can be set to alarm or trip

 Measuring voltage between phase-

-earth voltage and phase-phase

(selectable)

 Settable dropout ratio

Undervoltage

protection (27)

One voltage reduction can occur in the

power system during faults or abnormal

conditions.

The protection provides following features:

 Two definite time stages

 Each stage can be set to alarm or trip

 Measuring voltage between phase-

-earth voltage and phase-phase

selectable

 Current criteria supervision

 Circuit breaker aux. contact

supervision

 VT secondary circuit supervision, the

Undervoltage function will be blocked

when VT failure happens

 Settable dropout ratio

Breaker failure

protection (50BF)

The circuit breaker failure protection is

designed to detect failure of the circuit

breaker during a fault clearance. It ensures

fast back-up tripping of surrounding

breakers by tripping relevant bus sections.

The protection can be three phase started

to allow use with single or three-phase

tripping applications.

Once a circuit breaker operating failure

occurs on a feeder/transformer, the bus

section which the feeder/transformer is

connected with can be selectively isolated

by the protection. In addition a transfer trip

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SIFANG CSC-161 User manual

SIFANG CSC-161 User manual

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