ABB REL 356, Instruction Booklet

Page: 41 / 237

ABB REL 356 Current Differential Protection
2-18 Installation, Operation and Maintenance
56/64 kbps Option Only
FEPH Bit Error
DISPLAY VALUE # of Frames in Error in the previous hour (NA will be dis-
played for the first 5 minutes after power up)
CHTB Channel Trouble
Communication Channel Interface
REL 356 processors and intelligent data communication equipment (Modem or CODEC) continuously monitor status of
communication channel interface used for current differential protection.
The communication between two relays is full-duplex i.e., each relay continuously transmits and receives serial data.
The status of receiver and transmitter are displayed in the monitoring function fields CHRX and CHTX respectively.
Receiver Status
CHRX has the following definitions:
NORM – Normal, error-free reception
CHTB – Channel trouble, CRC error, excessive noise, corrupted frame, etc.
DCER – Failure to communicate with local DCE (modem, codec)
NODM – Failure to measure communication delay time
IDER – Unit ID error
TTRP – Reception of direct transfer trip code from the remote end
DSBL – Reception of differential protection disable code from the far end
OPBR – Reception of open breaker information from the remote relay
Transmitter Status
The following definitions are used for CHTX:
NORM – Normal state transmission
TTRP – Transmission of direct transfer trip code to the far end
Target (Fault Data) Information
The REL 356 stores 16 sets of targets (fault data). All 16 sets are accessible through INCOM
®
, but only the two most
recent sets of data are accessible from the front panel (see Table 2-3).
The first part of the fault data contains “Yes/No” targets (see Table 2-4), which identify the cause of the trip and the
status of certain system inputs and outputs; the second part of the fault data contains values, including currents,
voltages, fault impedance, and distance to the fault.
Communication Channel Testing
Monitoring functions display the following communication channel information:
MLDT — Provides Communication Delay (in msec)
9600 bps Audio Tone Option Only
XMTR — provides transmitter output level (in dBm)
RCVR — provides receiver input level (in dBm)
SNR — provides signal-to-noise-ratio (in dB)