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the type and size of the cable system and the installation conditions.
The client will then be granted access to the system to determine
the required ratings from a remote location which could be the office
of the engineer, the control room of a utility with the knowledge of
the cable operating conditions or any computer with internet access.
Figure 2
shows the basic OCRC (Online Cable Rating Calculator)
model with the heart being the simulation server where the simulation
software and other control programs are installed.
Emergency rating
More information will now be required to perform the calculations.
The first step will be to calculate the temperature of the conductors
before the emergency load is applied. It will therefore be required
to input not only the basic information but also the current at which
the cable operated prior to the application of the emergency current.
For the emergency rating calculation it will be required to input the
‘emergency’ or ‘overload’ current for which the simulation should be
performed as well as the time for which the current is
expected to flow. Two outputs will be available to the
client, namely: the temperature of the conductors if
the ‘emergency’ current is maintained for the specified
time, and the time that it will take for the temperature
of the conductors to reach the maximum allowable
temperature.
Conclusion
The client will be able to select the format in which
the results should be presented. These should be the
final results as for steady state simulations and tables
or graphs results showing for example the increase
in temperature with time for the selected conditions.
References
[1] Moore GF. Electric Cables Handbook, Third Edition. Oxford:
Blackwell Science, 1997.
[2] Anders GJ, Napieralski A, Zubert M, Orlikowski M. Advanced
modelling techniques for Dynamic Feeder Rating Systems.
[3] Liang M-j. April 1999. An assessment of conductor temperature
rises of cables caused by a sudden application of short pulse in
a daily cyclic load. IEEE Transactions on Power Delivery, Vol. 14,
No. 2.
[4] Anders GJ. 1997. Ratings of electric power cables. New York:
IEEE Press.
[5] Walker JJ. Modelling of power cables for thermal Finite Element
computer simulations. XVth International Symposium on High
Voltage Engineering University of Ljubljana, Elektroinštitut Milan
Vidmar, Ljubljana, Slovenia. 2007.
Client 1
Client 2
OCRC Simulation
Server
OCRC
Management
INTERFACE
Client ‘n’
Figure 2: OCRC model structure.
5
Functions of units in this model
OCRC management
• Register clients and maintain licences
• Manage and maintain simulation software on the server
• Create cable installation model in conjunction with the client
• Maintain the client database
• Maintain the data libraries in the simulation program
• Client support and consultation
OCRC simulation server
• Run the Simulation Software program continuously in the back-
ground (the programwill allowmultiple simultaneous client access)
• Run the OCRC access software
• House all client databases
• Allow clients to log onto the OCRC Simulation Server with a
Username and Password via the Internet and Service Provider
website
Programme
Following registration by the client for access to OCRC, the cable
model to be analysed will be created and the required expected outputs
confirmed. When the client accesses the program, he will be required
to select the type of simulation to be performed. Two options will be
available, namely ‘State Rating’ and ‘Emergency Rating’.
Steady state rating
For the steady state rating only basic information (values of variables)
will be required based on the cable model that was created. The
program will then calculate the current for the required conductor
temperature using the steady state thermal simulation platform.
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ENERGY EFFICIENCY MADE SIMPLE 2015