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  • Users: DTR2011
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  1. DTR2011

    Digital Relay Loosing it’s Mind

    We’re currently commissioning a large substation with A and B systems from different manufacturers. The P&C design has done away with control switches, Lock out relays and replaced with virtual lockouts. We’ve discovered that on the B system, the non volatile latches, used as 86 devices, are...
  2. DTR2011

    10kV Megger Testing on Oil Filled Devices

    We see specifications for 10kV megger tests on oil filled equipment from time to time. We own several 1kV and 5kV units, but often have to rent a 10kV device. Examples of equipment may be HV VT's, CCVT's, Power Transformers, etc. Typical testing specs often also call out for a "Doble" or...
  3. DTR2011

    thread238-349003 - Negative Power Factor Readings on SF6 Circuit Breaker

    There is a closed thread, 238-349003, with a bit of discussion on Negative Power (and Watts) readings on an SF6 breaker. We recently had a brand new 345kV Gas breaker flash over internally upon initial energization. The system was from the remote end and approximately 4 minutes after...
  4. DTR2011

    85CO Switch Function

    Generally speaking, I have seen 85CO switches on lines that have a communications based protection scheme. Is there any general consensus on what exactly placing the 85CO switch in the "Test" position should do, especially to the protection at the remote end? My understanding would be that if...
  5. DTR2011

    Negative Sequence Voltage (ANSI 47) on a Motor Bus

    I have been asked to investigate an issue for an industrial customer. There was an event where a 480V Main - Tie - Main Switchgear tripped both mains. I performed a site visit today, gathered information. The 480V SWGR feeds motor loads only, a combination of VFD's and across the line motors...
  6. DTR2011

    Bus Differential and Lock Out

    I came across something that did not 'feel right' when reviewing a new installation. 138kV Utility switching station with several large generation sources tied into a ring bus. There is an upgrade to the bus for new 87B (Bus Differential) relays. New panels, Lock Out Relay, Test Switches...
  7. DTR2011

    Generator Voltage THD - how much is too much?

    I was recently doing a Power Quality analysis at a small utility. Internally, when they run equipment (UPS in particular), there are some issues. In particular, it is when they run a certain generator (4160V 10MW - Wye Connected, Reactance grounded). The utility parallels with a much larger...
  8. DTR2011

    India - 370M INDIANS SWELTER IN HEAT AFTER POWER FAILS

    Story Ignoring all of the technical details that will likely be wrong, 370 Million is a lot of people left in the dark. Has there been a larger event in the world?
  9. DTR2011

    Distance Protection - Quad or Mho and Why?

    Let's assume we are talking about modern digital relays here. It seems in North America the Mho is preferred and in other countries the Quad is. My guesses would be historical preference or comfort. I am aware that the Quad offers better resistive coverage. My experience is that the Mho is...
  10. DTR2011

    Breaker and One Half Tripping Schemes

    Hi All- I was reviewing some potential work and came across what I would call a convolution of security vs. dependability. Curious how others handle tripping. I am concerned about local tripping onlt. Thanks
  11. DTR2011

    Solar Storms

    I'm curious who in the utility world is concerned and what is normally done to advert damage?
  12. DTR2011

    Proper wiring of Test Switches for Protection Devices

    Can someone please explain to me why some designers continue to wire relay test switches "backwards"? Example... I am reviewing a DC schematic, where the +DC goes to the top (odd number ) of an FT type switch, then out the blade, then to the LOR contacts. This appears to only function as an...
  13. DTR2011

    Protection System Scheme Testing

    I am curious about how folks in the utility world view this. We are a commissioning company and prefer to test for realistic scenarios. Our test protocol (on this job) calls for very simplistic tests. I feel like we are forced to comply with test specifications that require light bulbs and a...
  14. DTR2011

    Multi Ratio CT Testing Question

    Greetings- We have a customer that insists that all ratios of a MR CT be tested. We normally test all of the main taps, ie x1-x5, x2-x5,x3-x5,x4-x5. We are being asked to measure the inter tap ratios (x2-x3, x1-x2, etc). It is my understanding that the inter tap ratios are obtained via...

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