Monday, February 6, 2012

Modeling Circuit Breakers for Single and Three Phases

Models for switchgear are defined in IEC 61850-7-4 Edition 2. The model defines several aspects like controlling and monitoring of real circuit breaker switchgear:

XCBR excerpt of model:

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XCBR represents usually one (1 phase) circuit breaker. In some special cases it may represent all three (3 phase) circuit breaker. If you want to trip all three CBs of a 3-phase system, you have to define an instance 1 for that purpose: e.g., All_XCBR1.

In case you want to model the case to trip a single phase CB, you have to model 3 instances of XCBR, e.g., A_XCBR1, B_XCBR2, C-XCBR3.

The data object XCBR.SumSwARs represents the “Sum of switched amperes, resettable”. What to do when you want to model the SumSwARs of all three phases?

I saw this model the other day: extended data objects:SumSwARs1, SumSwARs2, SumSwARs3 … for Phase A, B, and C in a single XCBR instance:

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From a general modeling point of view this could be done (it is not wrong!) – But it is highly recommended not to do! Since a XCBR is usually representing a single CB then we need 1 instance per phase. A_XCBR1 would represent the sum of switched amperes of Phase A. The All-XCBR1 (see above) could represent the sum of switched amperes of all 3 CBs.

3 comments:

Anonymous said...

By the way, Karlheinz... does XCBR1.Dsc.stVal=false mean that all 3 phases are open OR all 3 phases are closed (assuming XCBR1 represents the 3 circuit breakers as a whole)? That's what most people have understood, I believe. But then, if XCBR1 is just one of the three CB, what would 'Dsc' mean?
Julio Dominguez

Karlheinz Schwarz said...

Dear Julio,
XCBR.Dsc represents the time discrepancy between multiple contacts. It does not appear in a single phase "LN XCBR". It would be available only in the LN XCBR representing the 3 phases (3 contacts).
The technical report IEC 61850-7-500 underway describes several use-cases. With regard to our issue it says: "Since also in three-phase breakers differences in the pole positions per phase may happen, the
modelling of supervision requests three instances of XCBR. The common XCBR reports the
phase discrepancy if any. The trip may be performed for all three phases (three-phase trip) or per
phase (single phase tripping) is very common at higher voltage levels e.g. to keep the power
system synchronization."

Ibrahima Gaye said...

Dear Karlheinz,
if a XCBR or XSWI represent the 3 phases(contacts), we can use the Data object Dsc(discrepancy).In Your comment you say that "XCBR.Dsc represents the time discrepancy between multiple contacts" but Dsc has SPS as functional Constraint so it 's boolean . For me Dsc is set true if there is discrepancy ?