Quantcast Coordination Study -Cont.

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Procedures (b) and (c) are repeated as often as required. Procedures (a) and (b) are the most
beneficially adapted to computer methods. These procedures are repetitive tasks that do not
require engineering judgement. While many decisions made in procedure (c) could be
determined using computer software, it would be difficult to duplicate sectionalizing situations.
Computer generated data derived from procedures (a) to (c) will be beneficial to the
performance.of procedure (d). Final documentation, however, requires the communication skills
of an engineer.
The data required to accomplish a coordination study is:
(a) A representation or model of the system including the type of device and its
location at each sectionalizing point.
(b) Peak load current at each sectionalizing point.
(c) Maximum and minimum fault current at each end point.
(d) Time current characteristic curves and ratings for each device used.
For the engineer performing a coordination study, a system map showing system configuration,
location of consumers, and existing sectionalizing points serves as an acceptable model of the
system. To calculate load and fault currents the model must also in some way give line section
loading, distance, conductor, and phasing information. It is recommended that line current and
fault current values be added to the sectionalizing study map to aid sectionalizing point
evaluations.
Final documentation will require a system map for communication of sectionalizing point
locations, in order to monitor and check computer results. A system's circuit diagram, modified
to include sectionalizing device locations, will often be adequate for a computer aided study.
Load current, maximum available fault current, and minimum available fault current is required
for each sectionalizing point. Sectionalizing software can be programmed to calculate these
current values. A more efficient method, however, is to modify existing voltage drop and fault
current software to store this information for later use by the sectionalizing software. This
will make use of the existing software already programmed to calculate these values and greatly
reduce sectionalizing software requirements.
The voltage rating, continuous current rating, interrupting current rating, minimum pickup rating,
and time current characteristic curves for each device used on the system are required for the
study. This data should be stored on a permanent computer data file since it remains constant
from one study to the next except for the addition of devices.
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