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Thread: Voltage Balance Relay / Switching VT inputs

  1. #31
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    Quote Originally Posted by myspark View Post
    You could have them both open but not both closed because N1102 and N1105 would be able to handle this part safely.


    Ok, I hear you and to quell you fears I give you this:
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    I'm in over my head...

  2. #32
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    Here is ABB's definition- time ran out to edit the above post.

    http://ask.abb.com/products/___/disc...-capabili/1341


    Also see page 8:


    https://pure.tue.nl/ws/files/2370686/200410772.pdf



















    Bus-transfer is loop switching between busbars within a substation. Gas insulated disconnectors are those associated with gas insulated switchgear or GIS as it is commonly known.

    The loops formed by such switchgear are short compared to those found in air insulated
    switchgear arrangements and hence the lower recovery or bus-transfer voltages.
    In North America, the term disconnecting or disconnect switch is used instead of disconnec-
    tor. Such a device is defined by the Institut
    e of Electrical and Electronic Engineers (IEEE)
    as:
    2
    “A mechanical switching device used for changing the connections in a circuit, or for
    isolating a circuit or equipmen
    t from the source of power.
    NOTE: It is required to carry normal load current continuously and also abnormal or
    short-circuit currents for intervals as specified. It is also required to open or close circuits
    when negligible current is broken or made, or when no significant change in the voltage
    across the terminals of each of the switch poles occurs.”
    The definitions are very similar
    both recognizing an ability to break negligible current. Only
    IEC, however, states specific values: up to 0.5 A of capacitive charging current and, for spe-
    cific disconnectors, a bus-transfer ability of
    1600 A against open-circuit voltages of 100 V to
    300 V (Annex B of reference 1).
    An earlier version of an IEEE standard included the following note:
    3
    “A disconnecting switch and a horn-gap switch have no interrupting rating. However, it is
    recognized that they may be required to inte
    rrupt the charging current of adjacent buses,
    supports and bushings. Under certain conditions, they may interrupt other relatively low
    currents, such as:
    1.
    Transformer magnetizing current.
    2.
    Charging currents of lines depending on length, voltage, insulation and other local
    conditions.
    3.
    Small load currents.”
    Horn-gap disconnectors generally have wider phas
    e spacings. The implication is that such are
    used to break currents and that some accommodation should be made for the reach of the arc
    towards other phases or grounded structures. In
    fact, this note recognizes that disconnectors
    are commonly used in North America to break small capacitive currents, transformer mag-
    netizing currents and loop currents. The standard was originally an American National Stan-
    dards Institute (ANSI) standard and was revised in 1992 to become an IEEE standard. At that
    time, the above-discussed note was removed. The reason for this was that a guide on current
    interruption had been developed
    4
    . The guide was based on the work of Andrews et al
    5
    and
    Peelo.
    6
    For reasons discussed later in sections 3 and 5 and Annex E, the guide should be
    viewed as questionable.











    This is for GIS, but explains it in detail and remains similar for open air bus work:


    https://www.google.com/url?sa=t&rct=...rj26MouqO5mby0
    I'm in over my head...

  3. #33
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    MBrooke...

    You approach is too complicated ! You failed to pick up my reference to a mechanically-interlocked contactor (in my day, ANSI 9R, based on EM relays) ! Then, N-bus VT and S-Bus VT become the two 3-ph inputs to the '9R' ! Their coil inputs will come from the '60' ! Furthermore, if the N Bus and S-bus are coupled, one-side (or the other) of the '9R' remains energized, providing voltage to the line's VT-associated circuitry, even when both isolators are closed !

    If you are into digital, SEL-700 should work!

    Regards, Phil
    Last edited by Phil Corso; 11-13-18 at 10:06 PM.

  4. #34
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    Quote Originally Posted by Phil Corso View Post
    MBrooke...

    You approach is too complicated ! You failed to pick up my reference to a mechanically-interlocked contactor (in my day, ANSI 9R, based on EM relays) ! Then, N-bus VT and S-Bus VT become the two 3-ph inputs to the '9R' ! Their coil inputs will come from the '60' ! Furthermore, if the N Bus and S-bus are coupled, one-side (or the other) of the '9R' remains energized, providing voltage to the line's VT-associated circuitry, even when both isolators are closed !

    If you are into digital, SEL-700 should work!

    Regards, Phil
    I like this- but one request- can you draw out the diagram?
    I'm in over my head...

  5. #35
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    MBrooke...

    Reur #34... Certainly! Contact me via MHF Notification Service!

    Phil
    Last edited by infinity; 11-14-18 at 08:37 PM. Reason: Removed email address us PM function for contact

  6. #36
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    Quote Originally Posted by Phil Corso View Post
    MBrooke...

    Reur #34... Certainly! Contact me via MHF Notification Service!

    Phil
    Email sent- let me know if it came through.
    Last edited by infinity; 11-14-18 at 08:37 PM. Reason: Removed email address us PM function for contact
    I'm in over my head...

  7. #37
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    MBrooke...

    Have previous commitments! Response will be sent later this morning!

    Phil

  8. #38
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    MBrooke...

    It's on its way!

    Phil

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