Signal Processing; Ur Signal Processing - GE C70 Instruction Manual

CHAPTER 2: PRODUCT DESCRIPTION

2.4 Signal processing

2.4.1 UR signal processing

The UR series relays are microprocessor-based protective relays that are designed to measure power system conditions
directly via CT and PT inputs and via other sources of information, such as analog inputs, communications inputs and
contact inputs. The following figure shows the overall signal processing in URs.
An analog low pass anti-aliasing filter with a 3 dB corner frequency is set at 2.4 kHz and is used for current and voltage
analog filtering as well as signal conditioning. The same filtering is applied for phase, ground currents, phase-to-phase
(when applicable), and auxiliary voltages. The 2.4 kHz cut-off frequency applies to both 50 Hz and 60 Hz applications and
fixed in the hardware, and thus is not dependent on the system nominal frequency setting.
Analog low-
Analog Inputs
pass filter
U
From
CT/VT
I
DSP module
HMI
Ethernet
ports
Communi-
Serial
cation
ports protocols
IRIG-B
Accurate
IEEE Time stamping
Real-Time
1588
clock
SNTP
CPU module
Ddebounce
filtering
Optoisolated
The UR samples its AC signals at 64 samples per cycle, that is, at 3840 Hz in 60 Hz systems, and 3200 Hz in 50 Hz systems.
The sampling rate is dynamically adjusted to the actual system frequency by an accurate and fast frequency tracking
system.
The A/D converter has the following ranges of AC signals:
Voltages:
C70 CAPACITOR BANK PROTECTION AND CONTROL SYSTEM – INSTRUCTION MANUAL
Figure 2-3: UR signal processing
Analog-to-
Digital band-
Digital
pass filter
Converter
A
D
Synchro-
phasors
Sampling
filtering
frequency
Tracking
frequency
Protection
selection,
algorithms
estimation
I>
Z<
U<
Synchrophasors
calculations
Channel
monitoring
CRC check
G.703, RS-422,
C37.94, direct fiber
± 2 ⋅ 260 V ( )
Phasor
estimation
½ cycle
Fundamen
tal freq.
Fourier
Phasors,
1 cycle
Seq. com-
Fourier
ponents
Frequency
T
RMS
values
Control
elements,
monitoring
elements,
FlexLogic,
Aggregation,
post-filtering
A
D
DCmA, RTD
SIGNAL PROCESSING
Analog Outputs
module
Events
Comtrade, data
logger
DNP, Modbus,
IEC60870
PMU (IEEE C37.118,
IEC 61850-90-5)
IEC 61850 (GOOSE,
MMS Server)
Inter-relay
comms
module
Contact Outputs
module
859740A1.vsd
Eq. 2-1
2-15
2