ABB Relion 670 Series Technical Reference Manual page 474

Section 7
Current protection
7.10.2.1
7.10.2.2
468
The BLOCK signal is a general purpose blocking signal of the pole discrepancy
protection. It can be connected to a binary input in the IED in order to receive a block
command from external devices or can be software connected to other internal
functions in the IED itself in order to receive a block command from internal functions.
Through OR gate it can be connected to both binary inputs and internal function outputs.
The BLKDBYAR signal blocks the pole discrepancy operation when a single phase
autoreclosing cycle is in progress. It can be connected to the output signal 1PT1 on
SMBRREC (79) function block. If the autoreclosing function is an external device,
then BLKDBYAR has to be connected to a binary input in the IED and this binary
input is connected to a signalization "1phase autoreclosing in progress" from the
external autoreclosing device.
If the pole discrepancy protection is enabled, then two different criteria can generate a
trip signal TRIP:
• Pole discrepancy signaling from the circuit breaker.
• Unsymmetrical current detection.
Pole discrepancy signaling from circuit breaker
If one or two poles of the circuit breaker have failed to open or to close the pole
discrepancy status, then the function input EXTPDIND is activated from the pole
discrepancy signal derived from the circuit breaker auxiliary contacts (one NO contact
for each phase connected in parallel, and in series with one NC contact for each phase
connected in parallel) and, after a settable time interval tTrip (0-60 s), a 150 ms trip
pulse command TRIP is generated by the Polediscrepancy function (52PD).
Unsymmetrical current detection
Unsymmetrical current indicated if:
• any phase current is lower than CurrUnsymPU of the highest current in the three
phases.
• the highest phase current is greater than CurrRelPU of IBase.
If these conditions are true, an unsymmetrical condition is detected and the internal
signal INPS is turned high. This detection is enabled to generate a trip after a set time
delay tTrip if the detection occurs in the next 200 ms after the circuit breaker has
received a command to open trip or close and if the unbalance persists. The 200 ms
limitation is for avoiding unwanted operation during unsymmetrical load conditions.
The pole discrepancy protection is informed that a trip or close command has been
given to the circuit breaker through the inputs CLOSECMD (for closing command
1MRK505222-UUS C
Technical reference manual