3-Phase Angle Calculations; Phase-Sequence Monitoring - Siemens SICAM Manual

Device Functions
4.1 Description
If the P,Q sign parameter value is set to not reversed, the sign of active power (P) and reactive power
(Q) for all phases indicates the original active power (P) and reactive power (Q). If the P,Q sign parameter
value is set to reversed, the signs of active power (P) and reactive power (Q) for all phases get reversed. The
P,Q sign parameter is independent of the power-flow direction parameter. The P,Q sign parameter
affects the total active power (P) and reactive power (Q). The P,Q sign parameter does not affect the
power-flow direction, fault direction, current angle, and power factor for all phases. It also does not affect the
watt-metric ground current.
For more information about the P,Q sign parameter, refer to

3-Phase Angle Calculations

4.1.13
A phase sequence defines the sequential timing in which each phase-to-ground voltage phasor lags each
phase-to-ground voltage phasor in the counter-clockwise direction.
Figure 4-8 shows the 3-phase sequence. The sequence shown below implies that V12 leads V23 by 120° and
V23 leads V31 by 120°. In addition, V1N leads V2N by 120° and V2N leads V3N by 120°. It is mandatory to
establish the balanced phase sequence before any calculations. In the device, V1N is considered as a reference
phasor at 0°. This phase sequence is needed to relate the calculated phasor angles with reference to the
phasor V1N.
[dw_sfcm3phangcalc, 1, en_US]
Figure 4-8
In a standard balanced system, all phase-to-phase voltages are phase-to-neutral voltages multiplied by √3 and
lead the phase-to-neutral voltage phasors by 30°. For example, in a standard 4-wire, 3-phase wye system with
phase-to-neutral voltages of 120 V and V1N selected as the reference phasor, then phase-to-phase voltages
are as follows: V12 = 208∠ 30°; V23 = 208∠ 270°; V31 = 208∠ 150°.
4.1.14

Phase-Sequence Monitoring

The phase sequence of the measured phase-to-ground voltages is checked by monitoring the angle difference
between phase-to-ground and phase-to-phase voltages.
SICAM FCM monitors the phase sequence of voltage signals from voltage sensors and displays it on the HMI/
Modbus. The phase-sequence monitoring algorithm uses measured phase-to-ground voltage and phase-to-
phase voltage angles in balanced condition. For monitoring the phase sequence, the threshold voltage is at
least 50 % of primary voltage.
40
3-Phase Angle Calculations
P,Q Sign, Page 125.
SICAM, Feeder Condition Monitor, Manual
E50417-H8940-C580-A4, Edition 03.2019