DARREC Shot initiation - Arc protection - Motor protection - Feeder protection - Back-up protection - Technical Manual - REX610 Protection and control - Relion Protection and Control - 1.2 - IEC - ANSI - 19.04.2024

REX610 Technical Manual
Figure 1. Example of an autoreclosing program with a reclose scheme matrix

In the AR function, each shot can be programmed to locate anywhere in the reclose scheme matrix. The shots are like building blocks used to design the reclose program. The building blocks are called CBBs. All blocks are alike and have settings which give the attempt number (columns in the matrix), the initiation or blocking signals (rows in the matrix) and the reclose time of the shot.

The settings related to CBB configuration are:
  • First...Seventh reclose time
  • Init signals CBB1…CBB7
  • Blk signals CBB1…CBB7
  • Shot number CBB1…CBB7
The reclose time defines the open and dead times, that is, the time between the OPEN_CB and the CLOSE_CB commands. The Init signals CBBx setting defines the initiation signals. The Blk signals CBBx setting defines the blocking signals that are related to the CBB (rows in the matrix). The Shot number CBB1…CBB7 setting defines which shot is related to the CBB (columns in the matrix). For example, CBB1 settings are:
  • First reclose time = 1.0s
  • Init signals CBB1 = 7 (three lowest bits: 111000 = 7)
  • Blk signals CBB1 = 16 (the fifth bit: 000010 = 16)
  • Shot number CBB1 = 1
CBB2 settings are:
  • Second reclose time = 10s
  • Init signals CBB2 = 6 (the second and third bits: 011000 = 6)
  • Blk signals CBB2 = 16 (the fifth bit: 000010 = 16)
  • Shot number CBB2 = 2
CBB3 settings are:
  • Third reclose time = 30s
  • Init signals CBB3 = 4 (the third bit: 001000 = 4)
  • Blk signals CBB3 = 16 (the fifth bit: 000010 = 16)
  • Shot number CBB3 = 3
CBB4 settings are:
  • Fourth reclose time = 0.5s
  • Init signals CBB4 = 8 (the fourth bit: 000100 = 8)
  • Blk signals CBB4 = 0 (no blocking signals related to this CBB)
  • Shot number CBB4 = 1

If a shot is initiated from the INIT_1 line, only one shot is allowed before lockout. If a shot is initiated from the INIT_3 line, three shots are allowed before lockout.

A sequence initiation from the INIT_4 line leads to a lockout after two shots. In a situation where the initiation is made from both the INIT_3 and INIT_4 lines, a third shot is allowed, that is, CBB3 is allowed to start. This is called conditional lockout. If the initiation is made from the INIT_2 and INIT_3 lines, an immediate lockout occurs.

The INIT_5 line is used for blocking purposes. If the INIT_5 line is active during a sequence start, the reclose attempt is blocked and the AR function goes to lockout.

Note: If more than one CBBs are started with the shot pointer, the CBB with the smallest individual number is always selected. For example, if the INIT_2 and INIT_4 lines are active for the second shot, that is, the shot pointer is 2, CBB2 is started instead of CBB5.

Even if the initiation signals are not received from the protection functions, the AR function can be set to continue from the second to the fifth reclose shot. The AR function can, for example, be requested to automatically continue with the sequence when the circuit breaker fails to close when requested. In such a case, the AR function issues a CLOSE_CB command. When the wait close time elapses, that is, the closing of the circuit breaker fails, the next shot is automatically started. Another example is the embedded generation on the power line, which can make the synchronism check fail and prevent the reclosing. If the auto-reclose sequence is continued to the second shot, a successful synchronous reclosing is more likely than with the first shot, since the second shot lasts longer than the first one.

Figure 2. Logic diagram of auto-initiation sequence detection
Automatic initiation can be selected with the Auto initiation Cnd setting to be the following:
  • Not allowed: no automatic initiation is allowed
  • When the synchronization fails, the automatic initiation is carried out when the auto wait time elapses and the reclosing is prevented due to a failure during the synchronism check
  • When the circuit breaker does not close, the automatic initiation is carried out if the circuit breaker does not close within the wait close time after issuing the reclose command
  • Both: the automatic initiation is allowed when synchronization fails or the circuit breaker does not close.
Note: The Auto init parameter defines which INIT_X lines are activated in the auto-initiation. The default value for this parameter is "0", which means that no auto-initiation is selected.
Figure 3. Example of an auto-initiation sequence with synchronization failure in the first shot and circuit breaker closing failure in the second shot

In the first shot, the synchronization condition is not fulfilled ( SYNC is FALSE). When the auto wait timer elapses, the sequence continues to the second shot. During the second reclosing, the synchronization condition is fulfilled and the close command is given to the circuit breaker after the second reclose time has elapsed.

After the second shot, the circuit breaker fails to close when the wait close time has elapsed. The third shot is started and a new close command is given after the third reclose time has elapsed. The circuit breaker closes normally and the reclaim time starts. When the reclaim time has elapsed, the sequence is concluded successful.