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Thanks for the update and do you know if it was a mechanical failure of the tower/line or failure of the protection scheme?

Does anyone know what caused wide spread power outage in Ecuador yesterday?

Recently numerical Trf Diff relay of an out of service transformer picked up when it’s HV dead tank circuit breaker was being tested for contact resistance by injecting 200A of DC current.I am bit curious to find out CT behaviour or response to pure DC current. Please share your views

Is there a way to find/derive the accuracy class of protection class CT with following specs ? Ratio- 1000/1A, 0.1 Px 500 R 3.0 ohm Is it fair to say that such a CT will equivalent to metering CT of class 1 accuracy?

Does anyone know what caused the power outage in Argentina and Uruguay?

we have an application wherein under voltage load shedding scheme needs to select 3 phase voltage from one of possile three line VTs.Can some one suggest a voltage selection relay capable of accepting three sets of three phase voltages?

Does anyone have experience with ABB make fault current limiter called "Is" ?

Phonanian and Slavag, Thanks for for use full tip.I would love to read IEEE document on this subject recommended by Slavag but can't get into IEEE website.Can some one upload this document on this website please?

Guys, Thanks for you valuable responses.UFLS scheme in question is part of state wide system protection scheme and consists of various stages consisting of rocof and simple under frequency stages.On tripping side it trips mix of residential and industrial loads at appropriate frequency...

What criterion should be followed for designing Under frequency load shedding scheme i.e. should it be based on security i.e.by having contact of main and check relays in series to issue trip or should it be based towards reliability or dependability i.e. by having contact of main and check...

Slavag Well I beg to differ with your view point on this issue.IEC 61850 is (or will become) very much part and parcel of protection as it talks about how to send CBF or interlocking signals via GSSE/GOOSE or how to send sample values from CT and VTs, both conventional and non conventional...

Is there a forum to discuss protection issues related to IEC 61850 standard?

David, Thanks for that.Your last option seems most prudent but how do you make sure that busbar is physically isolated after genuine bus fault. All other circuits(CBs) will trip by virtue of trip signal emanating from Bus prot scheme but station service bay will remain connected and...

Attached document produced by ESB, will give you some ideahttp://files.engineering.com/getfile.aspx?folder=c99392ce-c4bf-4ee7-b3a5-eaed5925b9cd&file=Review_of_Draft_Wind_Power_Station_Grid_Code_Provisions.pdf

It is about busbar proptection of HV(22kV) board ,where all circuits except station service transformer circuit have dedicated CTs for high impedance based bus protection scheme. Station service trf bay is switch fuse unit without CT. Appropriate fuse can be choosen to make sure that BZ scheme...

Is it possible to trip switch fuse unit via external trip signal? In other word does HV (22kv)switch fuse unit have trip coil?

Which is a good and easy software package for drawing electrical schematic drawings pertaining electrical power system ?

I would like to know difference,advantages and disadvantages of having transformer tap changer based on variable flux and constant flux method?

Does anyone know as to what level of financial penalty was imposed by the regulator for this incidence?

PRC, One of the ways to reduce fault current of YY grounded transformers could be by specifing high positive and zero seq impedance.