Section 8 Application And Settings; Over-All Measuring Principles Of The Fp-5000; Ct Connection Options - Eaton Cutler-Hammer FP-5000 Instructions Manual

IL17569
8 APPLICATION AND SETTINGS

8.1 Over-all Measuring Principles of the FP-5000

8.1.1 Analog Input Sample Processing
The four current (I , I , I , I ) and four voltage (V
A B C X
inputs are sampled 32 times per cycle. The residual current, I
computed from the phase currents during each update. The definition
of I is dependent upon the System Configuration setting for the Ct
R
Connection. Diagrams of the system configurations and definitions
of I are included in Section 8.2, Ct Connection Options, below.
R
For most protection purposes, the values of voltage and current are
updated every frequency cycle. In the case of instantaneous
overcurrent protection (50X and 50P) the values are updated every
half cycle.
For the monitoring function, values are the sums of one cycle rms
values averaged over 32 cycles. The averaged rms quantities
provide stable values of current and voltage for display on the front
panel. The phase angle for voltages and currents is computed from
the one-cycle voltage and current phasor values every 32 cycles for
updating the current phasor angle displays.
8.1.2 Frequency Measurement
The line frequency is obtained through the measurement of the
period of the phase A voltage. The frequency measurement is used
to determine the dynamic sampling rate of all other voltage and
current inputs. A system configuration setting is used to declare the
nominal frequency as 50 or 60 Hz, and this frequency will be used
for sampling in the case where phase A voltage is unavailable.
8.1.3 Discrete Input Sampling
The eight discrete contact inputs Cin1 – Cin8 and the zone
interlocking input states are declared every cycle.

8.2 Ct Connection Options

The Current Transformers may be connected in several ways, and
the specified configuration affects the way system measurements
are made and results computed.
The computation of the residual current I
System Configuration setting for the Ct Connection. The configura-
tions resulting from the three setting options are shown as well as
the calculated I residual current.
R
Effective June, 2001
, V , V , V )
A B C X
, is
R
, is dependent on the
R
Figure 8-1. Three-Wire Ct Connection
Figure 8-2. Four-Wire with IN Ct
Figure 8-3. Four-Wire with IG Ct
Page 8-1