Schweitzer Engineering Laboratories SEL-352-1 - MOD Operating Current (50 MD); Timer 2 (M2 Pu); Timer 3 (M3 Pu)-Scheme 2; Trip and Reset Logic Scheme Selection (TRLOG)

Date Code 20010731 Close Logic 4-21
SEL-352-1, -2 Instruction Manual
 Set M86T using the SELOGIC control equation, i.e., M86T = FBF + LBF + FOBF +
UBBF.
MOD Operating Current (50MD)
Range: 0.10–45.00 A in 0.01-A steps (5 A)
0.02–9.00 A in 0.01-A steps (1 A)
Set the 50MD overcurrent setting to pick up when the protected breaker current exceeds the
current break rating of the isolating disconnects. The lockout relay will not reset until current
has dropped below 50MD along with other conditions. A recommended setting is to require that
all breakers are open, and that the failed breaker is isolated with no current flowing through it,
50MD = 0.1 A for a nominal 5 A relay, 0.02 A for a nominal 1 A relay.
Trip and Reset Logic Scheme Selection (TRLOG)
Range: OFF, 1, 2, CUSTOM
The SEL-352 Relay provides two lockout relay control schemes. Each scheme has a trip
(86BFT) and reset (86RS) output. Scheme 2 also has an MOD trip output (MDT). All three of
these Relay Word bits are used in output equations such as OUT301 = 86BFT.
Use the 86BFT output to energize a lockout relay or trip another breaker directly. Use the 86RS
output to reset a lockout relay or indicate “OK to reset lockout relay.” Use the MDT output to
trip an MOD to isolate the failed breaker or use it for a “safe to disconnect” indication.
Timer 2 (M2pu)
Range: 0–8191 cycles in 1/8-cycle steps
Set M2pu long enough for breaker isolation and for the current to drop below the 50MD setting.
Take into account the lockout relay operate time, the operate times of any additional auxiliary
relays, the nominal tripping time of the slowest switching device to isolate the breaker, the time
for the 50MD element to drop out, and some margin. A very conservative setting is M2pu = 600
cycles.
Refer to the logic diagrams and timing diagrams in Section 5: Control Logic.
Timer 3 (M3pu)–Scheme 2
Range: 0–8191 cycles in 1/8-cycle steps
Scheme 2 uses a second timer, M3pu, to provide time for the MOD to completely open before
the lockout relay is reset. Set M3pu longer than the time required for the MOD to completely
open. A recommended setting is 120 percent of the MOD opening time, M3pu = 1.2
• 500 cycles
= 600 cycles.
A breaker alarm called “Current After MOD Trip” uses the M3 output, current, and the MOD
status indication (MODST) to alarm for slow MODs.
Refer to the logic diagrams and timing diagrams in Section 5: Control Logic.