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  • Users: hallmg
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  1. hallmg

    Transformer Trip/Fault procedure

    Hi, Where in the UK would i find regulations or procedures to do with what steps to take when an HV transformer has tripped, what tests to do, when to do a reset etc, that kind of thing? Regards, hallmg.
  2. hallmg

    Transformer trip yellow phase duo bias differential

    Hi Am wondering what kind of fault would cause an 33-3.3KV transformer to trip out on the yellow phase duo bias differential relay? Any help would be much appreciated.
  3. hallmg

    Adjusting transformer tap changers

    Hi, My query is:- There are two transformers feeding a distibution board. I wish to increase the voltage slightly by adjusting the tap settings on the transformers. How could this be accomplished? I assume you cannot have two transformers feeding a common board with different tap settings...
  4. hallmg

    Transformer Isolations Query

    Hello, The query i have is when performing isolations on transformers, why is the transformer secondary breaker opened first? Any help would be much appreciated. Regards, Hallmg.
  5. hallmg

    E/F relay suitability

    Hi, We are planning to use a spare feeder to supply a compressor motor (see attached drawing) The feeder panel has an earth fault relay already fitted, which has a CT on each phase and on the neutral. The compressor motor only has three phases and no neutral. The question is can this...
  6. hallmg

    415v motor heaters

    Hi, I have noticed some 415V motors have heaters fitted, but others dont, is this just down to the design of each particular motor? All HV motors have heaters fitted. Regards, Hallmg.
  7. hallmg

    33/3.3kv transformer spurious trips

    Hi, We have a spurious fault on a 33/3.3Kv transformer. Feeder L is isolated and feeder R is online, when deisolating L and closing in the 3.3Kv breaker, feeder R will trip, usually on restricted earth fault. The trip is cleared and no fault is found, feeder R is closed in and back online...
  8. hallmg

    How to calculate CT ratio

    Hi, I am trying to find the CT ratios for my 33KV switchgear protection relays, as the equipment is very old i cannot find much information so far. Is there a way to calculate what the turns ratios should be? Any help would be much appreciated. Regards, Melvin.
  9. hallmg

    3 phase motor phase fault

    Hi, We have a 415v motor which lost a phase but kept running. the usual running current was 37A, the overloads were set at 53A, on two phases the motor was drawing 63A. Supply fuses were 60A. Should not this fault have tripped the overloads?
  10. hallmg

    HV transformer VT on secondary side?

    Hi, I was wondering why on an HV transforemer,(33KV down to 11KV in this case) the VT is at the secondary side board incomer OCB, there appears to be no VT at the primary feed OCB? Does the VT at the secondary feed the control and protection n the primary then?
  11. hallmg

    UPS dummy battery bank

    Hi, I am looking to acquire some kind of dummy battery bank which could be connected to a UPS charger load, while the main bank is disconnected and put on on discharge test, would it be a case of making something up or could there be something available off the shelf? Any help would be much...
  12. hallmg

    What water type is best for topping up ni-cad cells?

    Hi, Was wondering what types of water is best for topping up UPS nickel-cadmium cells? We have steam condensate water and treated water available, treated water has been through reverse osmosis. Any suggestions would be much appreciated.
  13. hallmg

    MAVR null balance meter oscillation

    Hi, On one of my gas turbine control panels the 'null balance meter' for the modular AVR unit is steadily fluctuating about 5 degrees either way. The AVR unit is pretty old probably been in situ over 30 years, is made by John Brown, Type B9602941. On the other panels this meter is not...

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