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Hi veritas, It is outdoor installation at 132kV. thanks.

Thanks so far, I have a low-impedance scheme to commission. Problem is that customer does not want to disconnect loads. Double busbars are available, so we would probably create a dead bus then we could test CT ratio & polarities via primary injection. But I have a problem wrt the added bus...

Hi, I have had experience in testing busbar protection via secondary injection methods. This is easier because no live circuitry involved, no HV switching required. Can anyone give me tips on how to carry out site-commissioning, especially with regard to adding new bays to bus protection to...

Hi, We've had a few trips on our transformer differential relay that feeds an aluminum smelter. The differential relay is microprocessor-based, low impedance type. Are there anyone who has seen any funnies with this load? What from the load side could affect the protection adversely? The...

Hello, We have two 15MVA star-star transformers terminating on two 11kV busbars with a bus-tie. Full load current for the transformers are 787Amps. Assuming the load is spread evenly between the two buses, how would the bus-tie CB and bus-equipment be rated? Thanks.

Thanks for this invaluable input! I'm new at Distribution type work, more familiar with 220kV and above. I just need clarification on busbar configurations for 11kV indoor networks: i) What are typical busbar layouts? Or reference document (IEC). ii) If a double bus layout; would incomers...

dpc, The relay will trip an 11kV circuit breaker that is provided for as well. EPEngineer, It surprised me too... b.

EPEngineer, The xfr is indoor type. This was my thought as well, the use of a microprocessor relay to protect a small xfr like this is not justified. This I cannot change becos it was requested, priced and accepted before I had to have a look at it. Thanx, b.

Hi, I meant to say, please provide me with technical papers or bulletins to find this information. b.

Good day, I'm in an IEC world. I have a 11kV/0.4kV, 200kVA xfr. This means 10.5A high side nominal current, and 282A low side nominal current. How do I size the 11kV CT for overcurrent protection? The fault levels on 11kV is 25kA. b.

Kirabanda, You're right, I'm in an IEC country. Thank you for the info. I'll try to track these down, but these IEC documents are expensive. Are there any alternative to obtaining these? b.

Hi, Could anyone point me to documentation (preferably free to download?) that would assist me in specifying a circuit breaker on 11kV to 132kV networks? Your help is appreciated. B.

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Ralph, The Reactor is oil-immersed, whether it is gapped iron or coreless I do not have this info yet. I imagine the inrush phenomena to be more prominent in the gapped iron design? Yes we use 2nd harmonic restraint for energizing. I see how the design or type of reactor is important, this...

Hi, Need help. We have a 100MVA shunt reactor connected to 400kV bus. Additionally, this shunt reactor has a star connected tertiary that is loaded in emergency conditions. It's differential protection is misbehaving. Diff protection trips the breaker whenever the breaker is switched (ie...

KJvR, REF protection is quite fast (in the order of 20 ms). It does provide added sensitivity, but I think in your scenario, you'd need an added CT input. I agree with Ralph that 5P20 (or even 10P20) sufficient for OC or EF applications, and is standard industry practice. Ralph, Please...

Hi, I would like to have access to books/documents or url's regarding substation design from environmental impact assessment, sub location, construction, equipment rating, substation layout, cables layout, water ducts, and other factors that might affect design. Your comments would be appreciated.