ABB RER620 Technical Manual page 390

Section 7
Measurement functions
384
Demand value calculation
The demand value is calculated separately for each phase. The demand function is
implemented by means of a function that calculates the linear average of the signal
measured over a settable demand time interval. A new demand value is obtained once in a
minute, indicating the analog signal demand over the demand time interval preceding the
update time. The actual rolling demand values are stored in the memory until the value is
updated at the end of the next time interval. The switching of the demand interval without
the loss of data is done by storing the one minute demand values in the memory until the
longest demand interval is available. The maximum demand values for each phase are
recorded with time stamps. The recorded values are reset with a command.
The demand value calculation is only available in the three-phase current measurement
function, IA, IB, IC.
Value reporting
The measurement functions are capable to report new values for network control center
(SCADA system) based on the following functions:
• Zero point clamping
• Deadband supervision
• Limit value supervision
In the three-phase voltage measurement function, VA, VB, VC, the
supervision functions are based on the phase-to-phase voltages. However,
the phase-to-ground voltage values are also reported together with the
phase-to-phase voltages.
Zero point clamping
A measured value under zero point clamping limit is forced to zero. This allows the noise
in the input signal to be ignored. The active clamping function forces both the actual
measurement value and the angle value of the measured signal to zero. In the three-phase
or sequence measuring functions, each phase or sequence component has a separate zero
point clamping function. The zero value detection operates so that, once the measured
value exceeds or falls below the value of zero clamping limit, new values are reported.
1MAC309294-MB F
RER620
Technical Manual