Schweitzer Engineering Laboratories SEL-700G Series, Instruction Manual

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H.2
SEL-700G Relay Instruction Manual Date Code 20170814
Synchrophasors
Synchrophasor Measurement
➤
Small-signal analysis
➤
Power-system disturbance analysis
The SEL-3306 Synchrophasor Processor is a PC-based communications
processor specifically designed to interface with PMUs. The SEL-3306 has
two primary functions. The first is to collect and correlate synchrophasor data
from multiple PMUs. The second is to then compact and transmit
synchrophasor data either to a data historian for post-analysis or to
visualization software for real-time viewing of a power system.
The SEL-700G supports the protocol portion of the IEEE C37.118, Standard
for Synchrophasors for Power Systems. In the SEL-700G, this protocol is
referred to as C37.118. See Settings Affect Message Contents on page H.16.
Synchrophasor Measurement
The phasor measurement unit in the SEL-700G measures voltages and
currents on a constant-time basis. These samples are time-stamped with the
IRIG time source. The relay then filters the measured samples according to
Global setting PMAPP := Fast or Narrow (see PMAPP on page H.5).
The phase angle is measured relative to an absolute time reference, which is
represented by a cosine function in Figure H.1. The time-of-day is shown for
the two time marks. The reference is consistent with the phase reference
defined in the C37.118 standard. During steady-state conditions, the
SEL-700G synchrophasor values can be directly compared to values from
other phasor measurement units that conform to C37.118.
Figure H.1 Phase Reference
The TSOK Relay Word bit asserts when the SEL-700G has determined that
the IRIG-B time source has sufficient accuracy and the synchrophasor data
meet the specified accuracy. Synchrophasors are still measured if the time
source threshold is not met, as indicated by Relay Word bit TSOK = logical 0.
The MET PM command is not available in this case.
The instrumentation transformers (PTs or CTs) and the interconnecting cables
may introduce a time shift in the measured signal. Global settings VXCOMP,
VYCOMP, VSCOMP, IXCOMP, and IYCOMP, entered in degrees, are added
to the measured phasor angles to create the corrected phasor angles, as shown
in Figure H.2, Figure H.3, and Equation H.1. The VXCOMP, VYCOMP,
VSCOMP, IXCOMP, and IYCOMP settings may be positive or negative
values. The corrected angles are displayed in the MET PM command and
transmitted as part of synchrophasor messages.
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