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Function:
1 Application
Fast, reliable supervision of different analogue quantities is of vital impor-
tance during the normal operation of a power system.
Operators in the control centres can, for example:
• Continuously follow active and reactive power flow in the network
• Supervise the busbar voltages
• Check the temperature of power transformers, shunt reactors
• Monitor pressure in circuit breakers
Different measuring methods are available for different quantities. Cur-
rent and voltage instrument transformers provide the basic information on
measured phase currents and voltages in different points within the power
system. At the same time, currents and voltages serve as the input measur-
ing quantities to power and energy meters, protective devices and so on.
Further processing of this information occurs within different control,
protection, and monitoring terminals and within the higher hierarchical
systems in the secondary power system.
The REx 5xx protection, control, and monitoring terminals have a built-in
option to measure and further process information about up to five input
currents and five input voltages. The number of processed alternate meas-
uring quantities depends on the type of terminal and built-in options.
Additional information is also available:
• Mean values of measured currents I in the first, three current-mea-
suring channels
• Mean values of measured voltages U in the first, three voltage-mea-
suring channels
• Three-phase active power P as measured by the first, three current-
and voltage-measuring channels
• Three-phase reactive power Q as measured by the first, three current-
and voltage-measuring channels
•Frequency f
The accuracy of measurement depends on the requirements. Basic accu-
racy satisfies the operating (information) needs. An additional calibration
of measuring channels is necessary and must be ordered separately when
the requirements on accuracy of the measurement are higher. Refer to the
technical data and ordering particulars, for the particular terminal.
The information on measured quantities are then available to the user on
different locations:
• Locally by means of a built-in, man-machine interface (MMI) unit
• Locally by means of a front-connected personal computer (PC)
• Remotely over the LON bus to the station control system (SCS)
• Remotely over the SPA port to the station monitoring system (SMS)
7
Measurement of alternating
quantities
1MRK 580 159-XEN
Version 1.0-00
October 1996
Optional
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