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Busbar Protection

BasicsDevices overview

Ago-11 Alejandro De Vega

Need for busbar protection

A busbar is a point of convergence of many circuits generation transmission load

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M

G

GG

MM

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power concentrationpower concentration


Need for busbar protection

A busbar is a point of convergence of many circuits a concentration of power

high, destructive fault currents result !

A busbar fault endagers the stability of the grid

a fast and selective fault clearance is required (100…200ms incl. CB operation)

a high degree of availability/ dependability is a demand(EHV: redundant BBP „main1“/“main2“)

leads to serious damages of the switchgearfastest and selective fault clearance is required

may endanger human livefastest fault clearance is required


Reasons and probability of a busbar fault

Reasons mechanical problems (isolators, CTs) insulation problems (pollution, flash over) human errors (switch-onto-fault)

Probability ca. 1 fault / 10 years

but: the effects can be tremendous!!(outage, cost)


Principles of busbar protection

Reverse interlocking

Limited application range (no power reversal, single bus)

Distance protection

Slow fault clearance time (> 300ms)

Differential protection

fast, selective, wide application range


Typical scope of applications

Single busbar, up to 12 feeders *, w/o sectionalizer 7UT6x

Single busbar, any feeders, with sectionalizers 7SS60

Simple double busbar, with couplers 7SS60

Complex multi busbar (e.g. transfer bus) 7SS52

1½ breaker scheme 7UT6x, 7SS60, 7SS52

*) depending on the version of relay (7UT612, 7UT613/633, 7UT635) and type of measurement (1/3-phase)


7SS52 Distributed Busbar & Breaker Failure Protection

since 02/1998

distributed scheme,phase segregatedmeasurement

>1000 systems 7SS52 in operation

central unit

bay units

• • •


The 4 „S“ of a perfect substation protection

Selectivity

Stability

7SS52

+ limits breakdown amount+ increases availability

Communication

+ interfaces the world

+ avoids breakdown by false tripping

Security

HMI

+ ease of use

Self monitoring

+ reduces maintenance

Speed

+ limits damages+ maintains stability

+ avoids over- andunderfunction

Additional functions

+ added value


7SS52 System features (1)

12 busbars or bus sections (independant protection zones ) 48 feeders with up to 5 disconnectors 16 couplers (1 CT) / 8 couplers (2 CTs) 12 coupling zones (BB sections w/o feeders)

well proven measurement principle which is used by SIEMENS in analog and numerical systems tripping time <15 ms at the command contact CT saturation tolerated after 2ms (50Hz) / 1.7ms (60Hz)


7SS52 System features (2)

phase selective measurement for each zone

additional isolator independant 'checkzone'

dead zone (coupler) / end fault (feeder) protection for faults

between CB and CT

additional tripping characteristic for earth faults in resistive

earthed networks

integrated versatile two step breaker failure protection


high availability of the system by self monitoring provides profound information about network

disturbances (fault buffer, fault recorder) reduced maintenance efforts due to constant accuracy,

no ageing of components, no drift of pick up values high reliability as no mechanical switch-overs are made when

assigning feeders to selectivity zones according to their disconnector position a selectivity zone is taken over by another one (e.g. on-load transfer)

multifunctional by integration of additional protection functions (e.g. BFP) flexible and fit for the future as the system configuration is done

with standard DIGSI4 operating software

Why a numerical busbar protection?


Why a distributed busbar protection?

simplier and more flexible system

faster and easier installation

shorter comissioning time („bay by bay“)

easy and fast extension of protection system

lower CT burden

reduced wiring

simple and reliable tripping circuits


Distributed architecture

.

50

terminal panel

substation

50

terminal panel

50

terminal panel

50

terminal panel

central unit

22 22

fibre optics

1,5 km

bay unit


Centralized and local operation

B U S B A R P R O T E C T I O N 7 S S 5 2 1 1 - 5 C A 0 0

S I P R O T E C


S I P R O T E C


S I P R O T E C


S I P R O T E C

1 3 482


S I P R O T E C

RS 232

DIGSI 4Central unitand bay units

DIGSI 4bay unit

OF

RS 232


IEC 60870-5-103 interface

7SS522 - central unit

COMSBK SK1 to SK6... ...

Device address: 49

7SS523 - bay unit

Device address: 1 2 48

...

Substation controlsystem SCS

Telegram with address 49

Telegrams with addresses 1 to 48

* Device addresses are samples

one pair ofoptical fibers


Busbar and isolator configuration, online visualization

Configuration and operation of 7SS52 with DIGSI 4

Configuration as with Display Editor

Library of static and dynamic symbols, user defined possible as well

Connection of the dynamic symbol with the respective device (i.e. CB, isolator), measured value,

Standard typicals are provided, new typicals can be stored

Online visualization


Fault record

record of differential- and stabilizing currents (CU) and feeder currents (BU)


7SS52 Benefits

Reduced expenditure of engineering, installation

and commissioning Low CT requirements

matching of different CT ratios, Tsat>2ms(50Hz)/

1.7ms(60Hz), shared CT cores, easy verfication User friendly HMI („One DIGSI“) Maintenance reduced to testing of input quantities and trip circuits

due to high degree of internal supervision Few different system components (reduced stock of spare parts) Open for the future by easy and fast extension of protection system

Busbar Protection

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